pressure boosting

KSB Know-how, Volume 5

Pressure Boosting

Planning information for pressure boosting

November 2007 edition

Subject to technical modifications.

© Copyright byKSB Aktiengesellschaft

Publisher:KSB Aktiengesellschaft

Division:Building Services PumpsD-91253 Pegnitz

All rights concerning public distribution through film,radio, television, video, photo-mechanical reproduction,sound and data storage devices of any kind, the printingof excerpts, and the saving, accessing and manipulationof data in any way, shape or form are only granted withthe expressed permission of the manufacturer.

KSB – the complete range!

Pumps and systems for pressure boosting and fire fighting

Hya-Solo E

Hya-Solo D/DV

Hya-Eco K/VP

Hyamat K/V/VP

1

Contents

Page

1 Foreword 3

2 Fundamentals 4

3 Calculating the hydraulic data of pressure boosting units 8

3.1 Calculating the flow rate of a pressure boosting unit 8

3.1.1 Calculation example (1) – Drinking water supply system for a residential building

3.2 Calculating the pressure values and pressure zones 9

3.2.1 Connection types 9

3.2.2 Calculating the available pressure upstream of the PBU (pinl) 9

3.2.2.1 Determining the pressure zone upstream of the PBU 9

3.2.2.2 Calculation example for direct connection; continuation of (1) 10

3.2.3 Calculating the required pressure downstream of the PBU (pdischarge) 12

3.2.4 Calculating the discharge head of the PBU 13

3.2.5 Determining the pressure zone(s) downstream of the PBU 13

4 Calculation example (2) – Calculating the hydraulic data of a PBU for the supply of 14fire-fighting water for wall-mounted fire hydrants

5 Choosing the correct PBU variant (Pump type) – with calculation examples (3) + (4) 15

5.1 PBU with cascade control (Hya-Eco and Hyamat K) 15

5.2 PBU with one variable speed pump (Hyamat V) 20

5.3 PBU with speed control on all pumps (Hyamat VP) 26

6 Overview – Connection types for drinking water and service water installations 28

7 Overview – Connection types for fire-fighting systems, wet risers 30

8 Overview – Connection types for combined installations 32(drinking and fire-fighting water supply as well as service and fire-fighting water supply)

9 Overview – Connection types for wet- / dry-type systems 33

10 Accumulator selection / calculations 34

11 Dry running protection, selection criteria for PBUs 37

11.1 Protection of the supply network 37

11.2 Protection of pressure boosting unit 37

12 Effects of inlet pressure fluctuations 39

12.1 Indirect connection 39

12.2 Direct connection 39

2

Contents

2

Page

13 Causes of pressure surges 42

13.1 Pressure surges caused by valves 42

13.2 Pressure surges as a result of inlet pressure fluctuations 42

14 Standards, directives and statutory regulations 43

15 Inspection, maintenance and repair 46

16 Nomenclature 47

17 References 50

18 Annex

Worksheet 1, Calculation flow rates and minimum flow pressures 52

Worksheet 2, Calculating the peak flow rate 53

Worksheet 3, Flow rates 54

Worksheet 4, Water meters 55

Worksheet 5, Filters, drinking water heating systems, pressure losses in consumer supply pipes 56

Worksheet 6, Conversion of discharge head H into pressure increase �p 57

Worksheet 7, Head losses of steel pipes 58

Worksheet 8, Head losses of low-friction pipes 59

Worksheet 9, Permissible flow rate criteria of a PBU 60

1Foreword

This brochure is intended for all involved with theplanning, design and service of pressure boostingunits (PBU).

Pressure boosting units are often found in modernoffice, residential and hotel buildings for generalwater provision and fire-fighting purposes.

Considering the various PBU design concepts such as

• cascade control (Hya-Eco, Hyamat K)

• variable-speed control for one pump (Hyamat V)

• variable-speed control for all pumps (Hyamat VP)

• etc.

it is particularly important to select the right PBUconcept for the specific project at the planningstage.

This brochure offers design guidance for pressureboosting units ensuring easy installation anduninterrupted water supply.

KSB justifies its status as a full-line supplier ofpumps for building services by constantly devel-oping its range of products according to therequirements of its customers.

Pressure boosting units have the following typicalapplications:

• Residential buildings

• Office buildings

• Hotels

• Department stores

• Clinics/hospitals

• Trade and industry plants

• Spray and conventional irrigation

• Rainwater harvesting

• Small-scale domestic water supply units

A pressure boosting unit is required when theminimum pressure supplied by the local waterprovider, see Fig. 1, is insufficient.

Pressure boosting units and their ancillary com-ponents must be designed and operated in such away that neither the public water supply nor anyother consumer units are interfered with – anydegradation in the quality of drinking water mustlikewise be ruled out.

The regulations referred to in the brochure arebased upon regulations in force in Germany at thetime of writing. To ensure compliance, referenceshould be made to LOCAL and current regula-tions.

3

1Foreword

2Fundamentals

Drinking water is a consumable product, and is

therefore subject to strict legal regulations.

The essential requirements for drinking water

quality are laid down in:

DIN 2000

Central drinking water supply

DIN 2001

Drinking water supply from small units and

non-stationary plants

IfSG

Protection Against Infection Act

LMBG

Foodstuffs and Commodities Act

TrinkwV

Drinking Water Ordinance

The regulations for adequate water provision to

consumers which are applicable to units situated

in buildings and property are as follows:

AVB Wasser V

General Water Supply Terms Ordinance

DIN 1988

Drinking water supply units

DIN EN 805

Water supply – Requirements for units and

components outside buildings (if agreed upon)

DIN EN 806

Specifications for installations inside buildings

conveying water for human consumption (if

agreed upon)

(Public drinking water supply, for which KSB also

offers an extensive pump programme, is not dealt

with here.)

In terms of the origins of drinking water, a differ-

ence must be made between centralized and/or

local individual water supply units.

The following discussion deals with both possible

applications.

In all cases where the minimum supplied water

pressure (pmin,V) does not enable an unconditional

supply to all extraction points, i.e.:

pmin,V < ∆pgeo + pmin,flow + Σ(R· l+Z) + [1]

∆pwm + ∆pap [bar]

the deployment of a PBU is necessary.

Legend for [1]:

pmin,V = Minimum pressure available at the

local water provider’s hand-over point

∆pgeo = Static pressure loss

pmin,flow = Minimum flow pressure at the least

hydraulically favourable extraction point

4

2 Fundamentals

Fig. 1:Flow diagram, pressure boosting unit (PBU): direct connection

000

Mains water supply

pipe

Service pipe Installation within the building

Water meter

Consumer supply

pipe upstream of

the PBU

Consumer supply

pipe upstream

of

the PBU PBU= Pressure boosting unit and

ancillary components

PBU

Hand-over point-local water provider

(public/private)

m3

Filp

min,V

Σ(R·l+Z) = Pipe friction and other losses

∆pwm = Water meter pressure loss

∆pap = Apparatus pressure loss

The configuration and function of the PBU are de-scribed in DIN 1988 Part 5. This standard appliesto centralized and individual water provisionunits. It prescribes, amongst other things, built-instand-by pumps suitable for immediate operationfor the transportation of drinking water. Perman-ent operating reliability is required according toDIN EN 806 Part 2.

Omitting the installation of a stand-by pumpalongside a PBU for drinking water supply may bejustified when the breakdown of a PBU does notseriously affect residents’ requirements, e.g. in thecase of weekend houses. Here, a PBU may be in-stalled and operated without a stand-by pump.

Permission must however always be sought fromthe responsible Water Authority.

As a rule, the integration of the PBU (Fig. 1) mustbe performed in such a way that adverse hydrauliceffects on the public water supply network areminimized. This is facilitated through the selectionof suitable components which in turn relies onknowledge of inlet pressure fluctuation and themaximum connection capacity of the service pipetogether with an examination of the flow velocityin the house service pipe.

Anti-vibration mounting of the PBU (e.g. expan-sion joints with length limiters, anti-vibrationmounts) markedly contributes to a reduction insolid-borne sound transmission.

Fluctuating inlet pressures

Fluctuations in the supply pressure have a consid-erable effect on the operating characteristics of thePBU.

These range from a dramatic rise in switchingfrequency (excessive on/off) to increased levels ofdischarge pressure fluctuation. In certain cases, therated pressure of the unit components can beexceeded. This leads in all cases to pressure surgesand consequent wear on all associated parts.

If the inlet pressure fluctuations lie beyond +0.3/-0.2 bar, the following remedial action ispossible and may be necessary:

• Pressure controller / reducer upstream of the PBU(type series Hyamat K, Hyamat V, Hya-Eco)

• PBUs with variable speed base load pump(type series Hyamat V) (see also section 5.5.2)

• for large inlet pressure fluctuations: PBUs with speed control on all pumps (type series Hyamat VP)

Distribution of flow volume

Decisive for sizing the individual pumps of a PBUis the relationship between the PBU’s design flowrate and the maximum connection capacity of theservice pipe. Particularly in the case of PBUs withcascade control (Hya-Eco and Hyamat K range) itis important to ensure that the velocity change inthe service pipe does not exceed 0.15m/s when theindividual pumps are started and stopped. Thiscan be achieved by distributing the design flowrate across several pumps.

Possible remedies:

• Incorporating membrane-type accumulators on the inlet side

• Indirect connection via unpressurized inlet tank

• PBU with one variable speed base load pump (Hyamat V)

• PBU with speed control on all pumps (Hyamat VP)

Demand fluctuations

Sudden changes in demand downstream of a PBUcan lead to pressure surges/noises in the discharge-side distribution unit.

Pressure surges can sometimes trigger safetydevices or even cause damage to apparatus or leadto burst pipes and increased wear on pumps,valves, and piping. Reduction in the highlydynamic levels of consumption is the most effective

5

2Fundamentals

remedy (e.g. through the replacement of solenoidvalves with motor-operated valves).

Just as important is the adequate sizing of thepump in relation to its nominal flow rate.

∆QPu > ∆Qmax,dyn [m3/h] [2]

Legend for [2]:

∆Qmax,dyn = Change of flow of a highly dynamic consumer

∆QPu = Change of flow rate of each pump

In addition, membrane-type accumulators fitteddirectly upstream of dynamic consumers reducethe aforementioned effects. These must be of thedirect-flow type.

PBUs incorporating continuously variable speedcontrol on all pumps (Hyamat VP) can respondbetter to high consumer fluctuations due to thesynchronized operating mode of the pumps.

Noises

Modern PBUs are expected to operate with aminimum of noise.

Operating noise (airborne sound) is mainly gener-ated by the electric motor fans.

Cladding can considerably reduce noise emission.The selection of an appropriate location is likewisean important factor (away from recreation roomsand bedrooms).

In operation, pumps create vibrations, flow noiseand solid-borne noise. The provision of adequatesound insulation of the piping from the PBU istherefore of primary importance, and every PBUmust be separated from the piping and structuresurrounding it by suitable sound insulation (i.e.expansion joints with length limiters, anti-vibra-tion mounting using rubber-bonded metalelements).

Expansion joints must be easily replaceable.

With regard to flow noises, a moderate flow vel-ocity in piping, apparatus and pipe fittings shouldbe ensured.

Hygiene

In view of hygiene requirements, a distinctionshould be made between units dealing with drink-ing water and those handling service water.

Drinking water:According to the Drinking Water Ordinance (ex-cerpt) drinking water is referred to as “water forhuman consumption and use”. Drinking water isto be understood as water in its original conditionor after treatment which is used for drinking,cooking, preparing meals and beverages, for per-sonal hygiene and the cleaning of objects whichare destined to be used with food and those whichare temporarily in contact with the human body.

Service water:“Water to serve commercial, industrial, agricul-tural or similar purposes with varying levels ofquality which can include drinking water”.

When operating a PBU it is important that waterquality is not impaired.

An essential requirement is: operation of the PBUand its associated components should not allowstagnation.

As a closed unit rules out any health risk resultingfrom external contamination of drinking water,units with direct connection should be preferred tothose with indirect connection.

The following measures reduce the chance ofwater stagnating:

• Direct-flow membrane-type accumulators (dual connection)

• Automatic switchover between all pumps

• Smallest possible dead spaces in components handling water

• Forced flushing of pipe sections where stagnation could occur

A further aspect of hygiene is the temperature ofthe fluid.

The following factors can lead to a temperatureincrease of the water inside PBU components –unpressurized inlet tank, pumps, pipe componentsand membrane-type accumulators:

6

2 Fundamentals

• Increased ambient temperature at the site of installation

• Long periods of minimum consumption (office buildings at the weekend)

• Temperature increase due to the pumping operation (heat losses).

These factors can be eliminated through the selec-tion of an appropriate location and the promptstopping of pumps at minimum/zero consumption.

The materials and auxiliary equipment used in theconstruction of a PBU must be in line with therelevant regulations regarding the compatibilitywith drinking water (as stipulated, for example, bythe German LMBG, KTW, DVGW regulations).

Cleanliness during construction, transport, instal-lation and commissioning of a PBU und its associ-ated equipment, together with a final flushing ofthe entire unit according to DIN 1988 Part 2 orZVSHK technical instruction leaflet, are manda-tory requirements for water according toDIN 2000 which is:

• Absolutely hygienic

• Cool

• Neutral in terms of taste and odour

• Clear

• Free from foreign substances

7

2Fundamentals

3Calculating the hydraulic data of pressureboosting units

3.1Calculating the flow rate of a pressure boostingunit

3.1.1Calculation example (1)Drinking water supply system for a residential building

The calculation is performed on the basis of DIN 1988 (1988 edition).

The assumptions are as follows:High-rise residential building with basement,ground floor and a further 14 floors, see Fig. 4.

97 identically equipped living units have to besupplied with drinking water. The living units (LU)are equipped as follows:

Per living unit (LU):2 toilets with cisterns, DN 151 bath tub, DN 151 shower, DN 152 sink units, DN 151 bidet, DN 151 washing machine, DN 151 dishwasher, DN 151 kitchen sink, DN 15

The required total flow ΣV·R should as a rule be

established on the basis of the specifications madeby the taps, showerheads and fittings manufactur-ers.

If in a specific case such information is not avail-able, the total flow can be calculated by means ofWorksheet No. 1 in the Appendix.

According to this Worksheet ΣV·R is as follows:

Appliance flow rates

2 toilets 0.26 l/s1 bath tub 0.3 l/s1 shower 0.3 l/s2 sink units 0.28 l/s1 bidet 0.14 l/s1 washing machine 0.25 l/s1 dishwasher 0.15 l/s1 kitchen sink 0.14 l/s

This gives a required total flow per living unit of:1.82 l/s

The total calculated flow for 97 living units is:

ΣV·cal = 97 · 1.82 l/s = 176.5 l/s

In practice, total flow is never required.

For the determination of a realistic peak flow V·peak

use Worksheet 2, curve A, in the Appendix.

8

3 Calculating the flow rate of the PBU

Flow rate in m3/h (l/s)

Drinking water demand 4 5 6 8 9 10 11 12 13 14 15 20 25 30 40 50(1.11) (1.39) 1.67 2.22 (2.5) 2.78 3.06 3.33 3.61 3.89 4.17 5.56 6.94 8.33 11.1 13.9

Residential buildings 1)4 6 10 30 45 60 75 95 115 140 180

up to ... living units

Hospital 2)30 40 50 65 75 85 95 100 115 125 135 180 230 300 420 560

up to ... beds

Office buildings 2)160 200 240 340 380 440 480 540 600 660 730 1100 1500 2000

up to ... employees

Hotel 2)20 25 30 40 45 50 55 60 65 70 75 100 125 155 210 280

up to ... beds

Department store 2)40 50 60 85 95 105 115 125 135 150 160 220 300 400 750 1400

up to ... employees

1) These are reference values for living units with standard equipment (V· cal < 1 l/s); for living units with more “luxury” installations higher valuesmust be considered and/or a detailed calculation performed.

2) These reference values serve merely as a guideline. To determine the water consumption, the design engineer has to calculate the expected max. consumption taking the installations and their usage into account.

Table 1:Data for approximately calculating the flow rate of a PBU

9

3Calculating the flow rate of the PBU

The resultant peak flow is: V·peak = 4.4 l/s

The PBU to be selected must be capable ofhandling at least this peak flow.The followingequation is therefore applied:

V·peak =̂ Vmax,P =̂ QD = 4.4 l/s

� 15.9 m3/h

In pumping technology, the peak flow (V·peak)

corresponds to the design flow rate of the PBU(QD).

For an approximate calculation of the flow rate,below table 1 can be used.

3.2Calculating the pressure values and pressure zones

3.2.1Connection types

As a rule, a distinction is made between the directand indirect connection of a PBU to the watersupply unit.

The water provider will determine the type ofconnection permitted.

3.2.1.1Direct connection of a PBU, Fig. 2

This type of connection is characterized by a spe-cific inlet pressure (pinl) available upstream of thePBU.

As the supply pressure level at the hand-over pointcan vary between pmin,V and pmax,V, the resultantinlet pressure pinl upstream of the PBU has to beestablished according to the example in section3.2.2.2.

3.2.1.2Indirect connection of a PBU, Fig. 3

As the unit is separated through the installation ofan unpressurized inlet tank (indirect connectiontype), the existing supply pressure is reduced tothe ambient pressure; hence installing the PBU onthe same level as the inlet tank means that only thefilling level of the inlet tank is the available hydro-static inlet pressure (pinl � 0.1 bar).

Hence, an inlet pressure (pinl) of 0 bar is assumedfor the design of the PBU.

N.B.If the installation level of the unpressurized inlettank is lower than that of the PBU, the PBU mustbe designed for suction lift operation.

3.2.2Calculating the available pressure upstream ofthe PBU (pinl)

3.2.2.1Determining the pressure zone upstream ofthe PBU

The number of floors can be established throughthe following equation:

Fig. 2:Flow diagram, direct connection of a pressure boosting unit (PBU)

0 0 0

Mains water supply

pipe

p max,V

p min,V p inlet

PBU

m 3

Fil

Water meter Service pipe Consumer pipes upstream of the PBU

Consumer pipes

downstream of the PBU

Hand-over point (local water provider)

pinl, min – pflow – ∆pdynNwithoutPBU � ––––––—––––––––– [3]

∆pfl

2.47 – 1.0 – 0.2NwithoutPBU � ––––—–––––––

0.3

NwithoutPBU = 4.23

Rounded down

Nwithout PBU = 4

Counting from the branch (upstream of the PBUinlet pipe), the first 4 floors (ground floor, 1st, 2nd and 3rd floor) can be supplieddirectly, Fig. 4.

Water supply by means of a PBU isrequired from the 4th floor, Fig. 4.

Legend for [3]:

Nwithout PBU= Number of floors which can be supplied without PBU

pinl,min = Minimum pressure available upstream of the PBU

pflow = Flow pressure at consumer

�pdyn = Dynamic pressure difference

�pfl = Pressure loss per floor

3.2.2.2Calculation example for direct connection;continuation of (1)

The local water provider provides the followinginformation for a drinking water installation asper section 3.1.1:

pmin,V = 2.8 bar

pmax,V = 4.8 bar

Nom. diameter of service pipe: DN 80

Direct connection of PBU

Woltmann-type water meter

10


Fig. 4:Diagram depicting pressure zones

pressure

zone, here

pressure

reduction

measures

are not

required

Basement

Ground floor

5th

4th

3rd

2nd

1st

15th

.

.

.

.

.

.

.

.

.

.

N = 4 without PBU

N = 6flpr

PBU

000pmax,V

pmin,V

pinlet 0 bar

PBU

Mains water supply

pipe

Water meter Service pipe Consumer pipes upstream of the PBU

Consumer pipes

downstream

of the PBU


m3

Fil

Fig. 3:Flow diagram, indirect connection of a pressure boosting unit (PBU)

Calculating the flow rate of the PBU

Calculation of minimum, maximum and inletpressure fluctuations upstream of the PBU.

Σ(R·l+Z)inl = 0.1 bar(assumption made by engineering consultant)

V·peak

�pwm =[–––––]2

· �pV·max

15.9 1�pwm =[–––––]2

· 600 · ––––– bar30 1000

= 0.17 bar

(Woltmann-type water meter, vertical, DN 50,see Worksheet 4, Appendix)

V·S

�pap =[–––––]2

· �pV·max

15.9 1�pap =[–––––]2

· 200 ·––––– bar30 1000

= 0.06 bar

(Filter: nom. throughflow 30 m3/h, see Work-sheet 5, Appendix)

Minimum pressure:

This level is reached under min. supply pressurepmin,V and simultaneous max. water consumptionV·peak conditions. This requires that the dynamic

pressure losses in the installation between hand-over point (local water provider) and PBU inlet betaken into account.

[4]

Result, Fig. 5:

pinl,min = 2.8 – 0.1 – 0.17 – 0.06 = 2.47 bar

pinl,min � 2.5 bar

pinl,max = 4.8 bar

�pinl = 4.8 – 2.5 = 2.3 bar

The PBU must be able to operate reliably with aninlet pressure fluctuation of �pinl = 2.3 bar.

The inlet pressure pinl upstream of the PBUfluctuates to a greater extent than the supplypressure at the hand-over point. Therefore, it mustbe possible to operate the PBU with a supply pres-sure fluctuation �pinl. This must be examined foreach specific unit and, if necessary, appropriatemeasures should be taken to properly protect theunit (e.g. pressure reducers).

Maximum pressure:

This level is reached under maximum supplypressure pmax,V and simultaneous minimum waterconsumption conditions. The dynamic pressurelosses in the supply-side installation can be dis-regarded.

[5]pinl,max = pmax,V [bar]

pinl,min = pmin,V – Σ(R · l + Z)inl – ∆pwm –

∆pap [bar]

11

3

Fig. 5:Flow diagram, direct connection of PBU including pressure values

0 0 0 p max,v = 4.8 bar

= 2.8 bar p min,v p inl,min

p inl,max

= 2.5 bar

= 4.8 bar

PBU

m 3

Fil

Water meter

Mains water supply

pipe

Service pipe Consumer pipes upstream of the PBU

Consumer pipes

downstream of the PBU


[6]

Legend for [4], [5], [6]:

pinl,min = Minimum available pressure upstream of the PBU

pmin,V = Minimum available pressure at the local water provider’s hand-over point

Σ(R·l+Z)inl = Pipe friction and other losses from the supply pipe to the PBU

�pwm = Water meter pressure loss

�pap = Apparatus pressure loss

pinl,max = Maximum pressure upstream of the PBU

pmax,V = Maximum available pressure at the local water provider’s hand-over point

�pinl = Pressure fluctuation upstream of the PBU

3.2.3Calculating the required pressure downstreamof the PBU (pdischarge)

Calculation example:

The residential building as per section 3.1.1 isprovided with 97 identical living units. All floors – basement, ground floor and a further 14 floors –have a floor height of 3 m.

[7]

Calculation procedure:

The static head loss is calculated on the basis of the number of floors (N) and the floor height(Hfl).

[8]

see also Appendix, Worksheet 6

15 · 3�pgeo = ––––––– = 4.5 bar

10

70 · 15Σ(R·l+Z)discharge = –––––– = 1.05 bar

1000

(Estimation, see Appendix, Worksheet 5)

The measured pipe length from the PBU to theleast hydraulically favourable extraction point isapprox. 70 m.

(Exact calculation acc. to DIN 1988, Part 3)

pmin,flow = 1.0 bar (see Appendix, Worksheet 1)

The tap requiring the highest pressure determinesthe required minimum flow pressure (pmin,flow).

�pap = 0 (assumption: no further apparatusesbuilt into piping)

Above values inserted into the formula:

pdischarge = 4.5 + 1.05 + 1.0 + 0

= 6.55 bar ≈ 6.6 bar

Legend for [7], [8]:

pdischarge = Required pressure downstream of thePBU

�pgeo = Pressure loss from static head difference

Σ(R·l+Z)discharge = Pipe friction and other losses downstream of the PBU

�pwm = Water meter pressure loss

pmin,flow = Minimum flow pressure at consumer

�pap = Apparatus pressure loss (e.g. individual water meter)

N = Number of floors

Hfl = Floor height

N · Hfl∆pgeo = ––––––– [bar]10

pdischarge = ∆pgeo + Σ(R · l + Z)discharge +

pmin,flow + ∆pap [bar]

∆pinl = pinl,max – pinl,min [bar]

12


3.2.4Calculating the discharge head of the PBU

In the case of direct PBU connection, the inletpressure pinl can generally be used, under certainconditions (see sections 5.2 and 5.3) even fully.

The minimum permissible inlet pressure pinl,min (orthe inlet pressure fluctuation) depends on the PBUcontrol mode:

• for cascade controlled PBUs (Hya-Eco,Hyamat K) installing a pressure reducer up-stream of the PBU is often essential (see section2). This is assumed for our example. The over-all pressure reduction achieved by the pressurereducer is �ppressred 0.7 bar.

Above values inserted into the formula [9]:

H = [6.6 – (2.5 – 0.7)] · 10 = 48 m

• for variable speed PBUs (Hyamat V, HyamatVP) installing a pressure reducer on the inletpressure side is normally not required.*)

In general, the following equation applies forthe calculation of the pump’s discharge head H:

H = (pdischarge – pinl,min) · 10 [m] [9]

Above values inserted into the formula [9]:

H = (6.6 – 2.5) · 10 = 41 m

Legend for [9]:

H = Pump discharge head

pdischarge = Required pressure downstream of the PBU


3.2.5Determining the pressure zone(s) downstreamof the PBU

Assuming a constant supply pressure downstreamof the PBU of pdischarge � 6.6 bar, a rough checkof protective measures required can be made asfollows.

The maximum permissible static pressure in resi-dential buildings is max. 5.0 bar (safety valves,noises, toilet cisterns).

Since this maximum pressure of 5.0 bar must notbe exceeded and the highest static pressure levelwill be reached at zero consumption (Q �0), thedynamic pressure losses will be Σ(R·l+Z) = 0.

In order to find out up to which floor the con-sumers have to be protected by means of pressurereducers against a pressure of � 5.0 bar, thefollowing calculation can be applied:

[10]

6.6 – 5.0Nflpr � –––––––– = 5.3

0.3

(This value must be rounded up to 6.)

Legend for [10]:

Nflpr = Number of floors which have to be protected against inadmissible pressures by means of pressure reducers


pmax,flow= Maximum permissible flow pressure at consumer


At least the first 6 floors have to be protected withpressure reducers installed in the consumer pipesdownstream of the PBU. In this case, this appliesto floors 4 and 5, since the lower floors are sup-plied directly, cf. Fig. 4, page 10.

This consideration only applies to pressureboosting units with a constant, variable-speedcontrolled discharge pressure.

pdischarge – pmax,flowNflpr � –––––––––––––––––

�pfl

13

3Calculating the flow rate of the PBU

*) Whether this approach is hydraulically permissi-ble must, however, be checked by means of theKSB documentation.

14

4 Supply of fire-fighting water for wall-mounted fire hydrants

4Calculation example (2):Calculating the hydraulic data of a PBU for thesupply of fire-fighting water for wall-mountedfire hydrants

The residential building as per section 3.1.1 isequipped with 18 fire hydrants including standardfire service connections which must be suppliedwith fire-fighting water by a PBU.

The peak flow (V·peak) for the fire-fighting water

supply is calculated exclusively on the basis of thecalculated flow rate per hydrant multiplied by thesimultaneity factor (f).

The calculated flow per wall-mounted fire hydrantis V

·cal = 100 l/min = 6 m3/h (Worksheet 3, Appen-

dix) for a hydrant marked “F”. A simultaneityfactor of f = 3 according to DIN 14461 part 1 hasbeen laid down.

In the example, the peak flow (V·peak) and therefore

the design flow rate (QD) of the PBU for thesupply of fire-fighting water is:

[11]

V·peak = 6 m3/h · 3 = 18 m3/h = QD

Legend for [11]:

V·peak = Peak flow of a PBU

V·cal = Calculated flow rate per hydrant

f = Simultaneity factor

QD = Design flow rate of a PBU

According to EN 806-2: 2005 the followingapplies to PBUs for water supply and fire-fighting:

The flow rate of the PBU should be the high-er value of both supply requirements.

Calculating the pump discharge head H:

H = (pdischarge – pinl,min) · 10 [m] [12]

Using the discharge head calculation for drinkingwater, the discharge pressure and head of the fire-fighting PBU can be established with the followingformula:

[13]

Legend for [13]:


Σ(R·l+Z)discharge = Pipe friction and other lossesdown-stream of the PBU

pmin,hydr = Minimum flow pressure at the least hydraulically favourable hydrant


H = (4.5 + 1.05 + 3.0 – 1.8) m · 10 = 67.5 m

Selected: Hya-Solo D 1807 / 1.8

(1 Pump, 7.5 kW, pco = 9.6 bar, pci = 11.6 bar,pressure-dependent control)

The standard applied for the pressure boostingunits is DIN 1988-5 or, if agreed upon, DIN EN 806-2. In addition, the requirements for the respective fire-fighting concept are applicable.

∆pP = ∆pgeo + Σ(R · l + Z)discharge + pmin,hydr

– pinl,min [bar]

V·peak = V·cal · f = QD [m3/h]

15

Choosing the correct PBU variant

5Choosing the correct PBU variant (Pump type) – with calculation examples (3) + (4)

5.1PBU with cascade control(Hya-Eco and Hyamat K)

5.1.1Features

• Pumps are started / stopped as a function ofpressure

• Pumps run at full speed

• Auto-changeover of pumps

• Output pressure fluctuates by min. (pco – pci)by max. (p0 – pci) + �pinl

• Excessive on/off ("hunting") occurs when the water demand falls below a min. capacity Qmin (pco)

• The range of excessive on/off operation is enlarged with increasing pinl (inlet pressure).

This is particularly noticeable in the case of pumps with fewer stages (flat pump curve)

• In the case of inlet pressure fluctuations, potential use of the inlet pressure is limited

• Therefore, upstream pressure reducers are frequently required

• Adverse hydraulic impact on the mains supply network is relatively high

5.1.2Calculation example (3) Discharge head of PBU

Calculating the required pressure downstream ofthe (pdischarge)

[14]

pdischarge = 3.3 + 1.1 + 1.0

(assumed values)

pdischarge = 5.4 bar

The discharge pressure(pdischarge) required ofa PBU with cascade control is the cut-inpressure (pci). Depending on the design of thepump, the discharge pressure can rise up tothe value p0 = pinl + H0 / 10.

This increase in pressure always depends onthe type of pumps selected (flat/steep charac-teristic curve).

According to the local water provider, the supply pressure at the hand-over pointmay vary between a minimum value ofpmin,V = 2.2 bar and a maximum value of pmax,V = 3.5 bar. As the inlet pressurefluctuations are too high for cascade control,it is necessary to install a pressure reducer.Due to the pressure reduction of approx.0.7 bar achieved by the pressure reducer, the available inlet pressure is lowered to pinl = 1.5 bar.

pdischarge = �pgeo + Σ(R · l + Z) + pmin,flow [bar]

Hyamat K

On�/�Off

Cascade control

pco

p

pci

p(co-ci)

Q

Fig. 6:Performance chart of a PBU with cascade control (typeseries: Hya-Eco and Hyamat K)

pco

p0

pci

p(co-ci)

Fluctuation range of

discharge pressure

QQ (p )min co

Excessive on/off

H

5

16

5 Choosing the correct PBU variant

The pump’s discharge head is therefore establishedas follows:

[15]

H = (5.4 – 1.5) · 10

H = 39 m (Fig. 7)


pdischarge= Required pressure downstream of the PBU

�pgeo = Static pressure loss


pmin,flow = Minimum flow pressure at the consumer


pinl = Available inlet pressure upstream of the PBU

Selecting the appropriate PBU size(s):

V·peak = QD = 24 m3/h

(assumed)

H = 39 m

The following pumps have been selected

1. Hyamat K 5/0407/1.5 (5 pumps),

2. Hyamat K 6/0406/1.5 (6 pumps),

both options with stand-by pump

5.1.3Determining the pressure zones

Calculating pmin and pmax per floor:

(Refer to Fig. 8)

The max. discharge pressure pdischarge = p0 = pinl + H0 /10 is assumed for the PBU’ discharge pressure (pdischarge).

We assume that the installation of an upstreampressure reducer for a PBU in cascade operation isalways compulsory.

The available pressure upstream of the PBU (pinl)is to be understood as the pressure reducer’s out-put pressure. If a pressure reducer has not been in-stalled, the max. possible supply pressure (pmax,V)is to be used for pinl

[16]

8.0 – 5.0Nflpr = ––––––––– = 10

0.3

Legend for [16]:

Nflpr = Number of floors which haveto be protected against inad-missible pressures by means ofpressure reducers

pdischarge = Required pressure downstreamof the PBU

pmax = Maximum permissible flowpressure at consumer

�pfl = Pressure loss per floor (hfl = 3m)

H = (pdischarge – pinl) · 10 [m]

Fig. 7: Performance chart of a PBU with cascade controlincluding pressure values for a specifically chosenpump with inlet pressure (pinl )

p0pco

pci

p inl

= 8.0= 7.7

= 5.4 39

65

6.0

4.5

3.0

= 1.5

50

30

20

10

0

Fluctuation

range for p

at constant inlet

pressure

discharge

Output pressure from

the pressure

reducer

Pressure increase of pump

incl. inlet pressure pinl

Pump discharge head

for p = 0 barinl

QQ (p )min co QN

H [m]p [bar]discharge

pdischarge – pmaxNflpr = ––––––––––––––

�pfl

17

5Choosing the correct PBU variant

Calculating the max. flow pressure on arandom floor pmax,fl

Assumption:

Water consumption is zero or very low. Therefore,the head loss is HL ≈ 0

Calculation:

The max. floor pressure (pmax,fl) is calculated bydeducting the static pressure loss �pgeo (floor X)of the respective floor from the PBU dischargepressure (pdischarge).

The static pressure loss of a building with N = 11 floors, meaning ground floor + 10 floors,amounts to:

[17]

Where �pgeo,fl = 0.3 bar

�pgeo = 11 · 0.3 bar = 3.3 bar

[18]

For example for the 10th floor

pmax = 8.0 bar – 3.3 bar = 4.7 bar

In general, the following calculation applies to themax. floor pressure:

[19]

[20]

0

Pumps per PBU

withoutstand-by pump

with stand-by pumpaccording to DIN 1988

1 2

4

6

8

10

12

2

3

4

5

6

/

/

2

3

4

5

6

3

6

9

12

15

18

4

8

12

16

20

24

5

10

15

20

25

30

6

12

18

24

30

36

7

14

21

28

35

42

8

16

24

32

40

48

9

18

27

36

45

54

14.4

pbar

A Hm

Qm /h3

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

0415

0413

0411

0409

0408

0407

0406

0405

0404

0403

0402

12.4

10.5

9.5

8.5

6.6

5.6

4.6

3.6p .9 barP = 3

2.6

1.7

0

7.5

0410

Characteristic curve values and tolerances to ISO 9906

Fig. 8:Selection chart Movitec 4

∆pgeo = N · ∆pgeo,fl [bar]

pmax = pdischarge – ∆pgeo (floor X)

= p0 – ∆pgeo (floor X) [bar]

pdischarge= p0 [bar]

pmax = p0 – �pfl · N [bar]

18


Legend for [17], [18], [19], [20]


�pgeo,fl = Pressure loss from static head difference per floor


p0 = Maximum pump pressure at zero flow rate (Q = 0)

pmax = Maximum pressure



�pgeo (floor X) = Static pressure loss for floor X

Calculating the minimum flow pressure on arandom floor

Assunption:

1. The PBU discharge pressure (pdischarge) corresponds to the cut-in pressure pci.

2. Water consumption is max QN = V·peak.

3. The dynamic pressure losses Σ(R·I+Z) correspond to the maximum value.

4. For simplification we assume a linear distribu-tion of the pressure loss across the individualfloors. This applies both to the static anddynamic pressure loss.

Calculation:

The following applies to a building with 11 floors (N = 11):

�pgeo,fl = 0.3 bar per floor

A dynamic pressure loss of

Σ(R·l+Z) = 1.1 bar

gives a dynamic pressure loss per floor of

[21]

1.1�pdyn, fl =–—––––– = 0.1 bar

11

The calculated total pressure loss per floor is

[22]

�pfl = 0.3 bar + 0.1 bar

�pfl = 0.4 bar

In general, the following applies to the flowpressure at a floor:

[23]

Legend for [21], [22], [23]

�pdyn,fl = Dynamic pressure loss per floor

Σ(R·l+Z) = Pipe and other losses


�pfl,tot = Total pressure loss per floor

�pgeo,fl = Static pressure loss per floor

pmin,flow (N)= Minimum flow pressure at the consumer on floor N


Example:

Determining the available flow pressure for the 5th floor:

N = 6 (ground floor + 5 floors)

using the values as per Fig. 9 gives:

pmin,flow (6) = 5.4 bar – 0.4 bar · 6

pmin,flow (6) = 3.0 bar

Σ(R·l+Z)�pdyn, fl = –—––––– [bar]

N

�pfl,tot = �pgeo,fl + �pdyn,fl [bar]

pmin,flow(N) = pdischarge – �pfl · N [bar]

19


5.1.4Pressure zone calculation for a building equipped with a PBU using cascade control(Hya-Eco and Hyamat K)

Outcome:

In the event of pump failure, consumers are notaffected since appropriate measures (installation ofpressure reducers on the inlet side, establishingpressure zones on the consumer side) have beentaken.

• Inlet pressure reducer:

Required as the inlet side pressure fluctuationsare too high for cascade operation.

As a result of the pressure loss inherent in thereducer (here = �p 0.7 bar) the minimumavailable inlet pressure pinl drops to 1.5 bar.The nominal discharge head required of thepumps is thereby increased by 7 m.

• Consumer-side pressure reducer

On floors 3 to 8, the max. permissible pressurepmax = 5 bar would be exceeded (Fig. 9). Forthis reason, these floors require protection frompressure reducers. The available pressures arethen set to a uniform pressure of 1.3 bar.

5.1.5Summary

The cascade-controlled PBUis favourably priced.However, tackling this unit’snegative consequences(pressure fluctuations,excessive on/off operation,hydraulic impact on thewater supply network…)requires the installation ofvarious additionalcomponents (pressurecontroller, membrane-typeaccumulator…).

Top pressure zone,

directly supplied via PBU

Bottom pressure zone,

directly supplied via

supply pressure

Middle pressure zone,

supplied via PBU,

protected by a pressure

reducer per floor

Basement

Ground floor

10th

9th

8th

7th

6th

5th

4th

3rd

2nd

1st

Hyamat K p 0

p ci p inl

= 8.0 bar

± 0 m

+ 3.0 m

+ 6.0 m

+ 9.0 m

+ 12.0 m

+ 15.0 m

+ 18.0 m

+ 21.0 m

+ 24.0 m

+ 27.0 m

+ 30.0 m

+ 33.0 m

p = max 6.8 bar

p = bar max 6.5

p = bar max 6.2

p = max 5.9 bar

p = bar max 5.6

p = bar max 5.3

p = bar max 5.0

= 5.4 bar

p = bar min 3.8

p = bar min 3.4

p = bar min 3.0

p = bar min 2.6

p = bar min 2.2

p = bar min 1.8

p = bar min 1.4

=1.5 bar = 2.2 bar

1.4 bar

p = 1.0 min bar

p = 1.0 min bar

1.8 bar

= 3.5 bar

2.9 bar

p = 2.6 max bar

p = 4.7 max bar

3.2 bar

1.3 bar

1.3 bar

1.3 bar

1.3 bar

1.3 bar

1.3 bar

W F p max,V

p min,V

Fig. 9:Schematic drawing of a PBU operating with cascade control incl. pressure values and pressure zones

20


5.2PBU with one variable speed pump (Hyamat V)

5.2.1Features

• One variable speed base load pump

• Peak load pumps cut in depending on the pressure (�p-range)

• Peak load pumps run at full speed

• Pump change-over of variable speed base loadpumps is possible

• Discharge pressure is largely constant

• Inlet pressure fluctuations can be compensatedfor

• In the event of a malfunction of the speedcontrol, unit operates like a cascade

• Under low flow conditions, the base load pumpis shut down irrespective of the inlet pressure

• Hydraulic impact on the water supply networkis low

• Inlet side pressure reducer is normally notrequired

5.2.2Calculation example (4)Discharge head of PBU

The discharge pressure pdischarge is calculated asfollows

[24]

pdischarge = 3.3 bar + 1.1 bar + 1.0 bar = 5.4 bar

Legend for [24]

pdischarge= Required pressure downstream of thePBU

�pgeo = Static pressure loss


pmin,flow = Minimum flow pressure at consumer

The required discharge pressure (pdischarge) onpressure boosting units with one variable speedpump is also referred to as the cut-in pressure (pci).

Under normal operating conditions, the dischargepressure is almost constant.

When peak load pumps are started or stopped, thedischarge pressure may slightly deviate from pci

(e. g. ± 0.5 bar) for a short period of time.

Note:

In the event of a malfunction (speed controlfailure) the unit automatically changes over tocascade operation. As a pressure reducer is notnormally installed in the case of a PBU with onevariable speed pump, the discharge pressure canrise to a maximum value of

pdischarge = p0 = pinl,max +H0 / 10.

pdischarge = �pgeo + Σ(R·l+Z) + pmin, flow [bar]

Fig. 10:Performance chart of a PBU with one variablespeed pump (Type: Hyamat V)

p 0

p ci

Q Excessive on/off

Almost constant

discharge pressure

H

n pumpsn-1 pumps

Hyamat V

On / Off continuously

controlled

pump change-over

One pump with continuous speed control

p

const.pci

Q

21

Possible remedial measures:

Option 1

One central pressure reducer on the discharge sideof the PBU

Setting the pressure reducer to the output pressureppr = 6.2 bar ensures that the pressure reducer isfully open under normal operating conditions.Only in the event of a fault is the pressure thuslimited to the value set (ppr = 6.2 bar).

Option 2

A pressure-controlled by-pass valve between inletand discharge side of the PBU with additional tem-perature monitoring.

The by-pass valve opens as soon as the set pres-sure is reached or exceeded (pdischarge � 6.2 bar). If consumer demand is low, the excess flow isrouted to the PBU inlet.

The installation of an additional temperaturemonitoring device in the by-pass (hygiene!)ensures the pump is shutdown in the event of aprolonged period of low water demand.

Calculating the discharge head of the PBU

The supply pressure at the hand-over point variesbetween the minimum pmin,V = 2.2 bar and themaximum value pmax,V = 3.5 bar.

Pressure boosting units with one variable speedpump are capable of handling supply pressurefluctuations (see Fig. 13 and 14) thus eliminatingthe need for pressure reducers.

The discharge head is determined on the basis ofthe minimum supply pressure pmin,V.

The pump head is calculated as follows:

[25]

H = (5.4 bar - 2.2 bar) · 10

H = 32 m (i.e. 7 m less than Hyamat K)

Legend for [25]:





Fig. 11Central pressure control (e.g. pressure reducer)

p 0

p ci

p pr

= 9.1 bar

= 5.4 bar

= 6.2 bar

PBU

Hyamat V

p ci

p mon

p discharge

= 5.4 bar

= 6.2 bar

6.2 bar PBU

Hyamat V

T max

≥

Fig. 12Pressure control using a by-pass valve

H = (pdischarge - pinl,min)·10 [m]

22


Fig. 14:Performance chart of a PBU withone variable speed pump, incl.pressure values, for a specific pumpwith inlet pressure pinl,min

p 0 without protection

with protection

p E

p = ppr valve

p inl,min

= 7.8

= 5.4 32

Rotational

speed = 76 %

Rotational

speed = 100 %

H = 56 0

= 6.2

= 2.2

60

50

40

20

10

0

Pressure increase of

pump(s) incl. min.

inlet pressure

p inl,min

Discharge head of

pump(s) for

p = 0 bar inl

Discharge pressure Pump discharge head

Q Q N

H [m] p [bar] discharge

min. inlet pressure

Fig. 13:Performance chart of a PBU withone variable speed pump, incl.pressure values for operation withmax. inlet pressure pinl,max.

Inlet pressure reducers are notnormally installed with this type ofsystem! The max. inlet pressure pinl,max, iscritical for calculating the max.discharge pressure p0.The max. discharge pressure p0 canonly occur in the case of a fault inthe continuous speed control.(Change-over to cascade operation).

p 0 without protection

with protection

p ci

p = ppr valve

p inl,max

= 9.1

= 5.4 19

Rotational speed = 58 %

Rotational

speed = 100 %

H = 56 0

= 6.2

= 3.5

60

50

40

30

10

0

Discharge pressure

Pressure increase of

pump(s) incl. max.

inlet pressure

p inl,max

Discharge head of

pump(s) for

p = 0 bar

inl

Pump discharge head

Q Q N

H [m] p [bar] discharge

max. inlet pressure

23

Choosing the correct PBU variant 5

Selecting the appropriate PBU size(s):

V·peak = QD = 24 m3/h (assumed)

H = 32 m

The pumps selected

1. Hyamat V 5/0406/2,2 (5 pumps)�pinl,perm = 1.3 bar,

2. Hyamat V 6/0405/2,2 (6 pumps)�pinl,perm = 1.5 bar, with stand-by pump for each option

In this case (�pinl = 1.3 bar) both PBU sizes canoperate without a pressure reducer on the inletpressure side.

Pumps per PBU

without stand-by pump

with stand-by pump according to DIN 1988

8

10

12

–

–

–

5

6

/

/

5

6

12

15

18

16

20

24

20

25

30

24

30

36

28

35

42

0

0

0

0

0

0

0

0

0

0

0

0

Movitec 0415

Movitec 0413

Movitec 0411

Movitec 0410

Movitec 0409

Movitec 0408

Movitec 0407

Movitec 0406

Movitec 0405

Movitec 0404

Movitec 0403

Movitec 0402

32

40

48

36

45

54

14.4

pbar

A Hm

Qm /h3

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

0415

0413

0411

0409

0408

0407

0406

0405

0404

0403

0402

12.4

10.5

9.5

8.5

6.6

5.6

4.6

3.6p . barP = 3 2

2.6

1.7

0

7.5

0410

Characteristic curve valuesand tolerances to ISO 9906

–

–

–

1

1

1

1

1

1

1

11.3

11.5

1

1

1

2

2

2

2

2

2

2

2

2

2

1.5

3

3

3

3

3

3

3

3

3

4

4

4

4

4

4

4

5

5

5

5

6

6

6

78

7

Max

. use

ful i

nlet

pre

ssur

e ris

e

pin

bar

in r

elat

ion

to t

he p

ump

cur

ve

inl,m

ax .

bar

Fig. 15:Selection chart Movitec 4

24

Choosing the correct PBU variant5


Under normal operating conditions, a unit usingcontinuous speed control ensures an almostconstant discharge pressure pdischarge = 5.4 bar (see also section 5.2.2).

The following equation applies to the number offloors requiring protection (Nflpr):

[26]

5.4 bar - 5.0 barNflpr = ––––––––––––––

0.3 bar

Nflpr = 1.3 � 2

From this equation can be deduced that the lowesttwo floors, namely the basement and the groundfloor, would require protection. However, thebasement, ground floor as well as 1st and 2nd

floors are not connected to the PBU. Floors 3 to10 do not, in principle, require any protection.

In the event of a fault: Speed control failure

In this case, the following applies due to change-over to cascade operation:

[27]

pdischarge = p0 = 3.5 bar + 5.6 bar

= 9.1 bar

Result of [27] inserted into equation no. [26]:

9.1 bar - 5.0 barNflpr = ––––––––––––––

0.3 bar

Nflpr = 13.6

This means that while in principle no floorsrequire protection, in the event of a malfunction,

all floors connected to the PBU must be protected (see also section 5.2.2).


Nflpr = Number of floors which have to beprotected against inadmissible pressuresby means of pressure reducers

pdischarge= Required pressure downstream of thePBU

pmax = Maximum pressure


p0 = Maximum pump pressure at zero flow rate (Q = 0)

pinl,max = Maximum pressure upstream of the PBU

H0 = Maximum discharge head at zero flow rate (Q = 0)

Determining the max. floor pressure (pmax,fl)

As in section 5.1.3, we take a static approachmeaning we do not assume any flow lossesΣ(R·l+Z).

Normal conditions:

pdischarge = pci

In the event of a fault: pdischarge = p0

[28]

Example:

Floor 10 requires: �pgeo,10th floor = 3.3 bar

Normal conditions:

pmax,10th floor = 5.4 bar - 3.3 bar

pmax,10th floor = 2.1 bar

In the event of a fault:

pmax,10th floor = 9.1 bar - 3.3 bar

pmax,10th floor = 5.8 bar

H0pdischarge= p0 = pinl,max + –––––– [bar]10

pmax,fl = pdischarge - �Hgeo (floor x) [bar]

pdischarge - pmaxNflpr = ––––––––––––

�pfl

pdischarge - pmaxNflpr = ––––––––––––

�pfl

25

Choosing the correct PBU variant 5The other floor pressures can be calculated usingthe respective �pgeo values.

Legend for [28]:

pmax,fl = Maximum pressure per floor


�Hgeo(floor X) = Static pressure loss for floor X.

Calculating the minimum flow pressure perfloor

The same calculation as the one described insection 5.1.3 (Calculating the minimum flowpressure per floor) can be used.

The following applies to the 5th floor: pmin,fl = 3.0 bar

5.2.4PBU with one variable speed pump (Hyamat V)– Possible effects

In the event of a fault (breakdown of the variablespeed control), the pressure rises on those floorsnot provided with additional safety equipment!

Conclusion:

In the event of a fault (variable speed controlbreakdown), the max. static pressure from floors 4 to 10 considerably exceeds the maximum setpressure of 5 bar.

Possible effects:

• Considerably increased flowvelocity

• Float valves of cisterns ceaseto close

• At a pressure of 6 bar, thesafety valves on the waterheaters open. As a result ofpossible fluctuations, in-creased switching frequencyof the pumps and evenpressure surges are to beexpected.

Possible remedial measures:

• Installation of a centralpressure reducer downstreamof the PBU (the value set forthis downstream pressuremust be > pci)

• Installation of a by-pass valve+ temperature monitor in theby-pass pipe from theconsumer to the inlet side



supply pressure

Top pressure zone,

supply via PBU

Basement

Ground floor

10th

9th

8th

7th

6th

5th

4th

3rd

2nd

1st

Hyamat V

± 0 m

+ 3.0 m

+ 6.0 m

+ 9.0 m

+ 12.0 m

+ 15.0 m

+ 18.0 m

+ 21.0 m

+ 24.0 m

+ 27.0 m

+ 30.0 m

+ 33.0 m

= 2.1 bar

Normal operation Fault

= 2.4 bar

= 2.7 bar

= 3.0 bar

= 3.3 bar

= 3.6 bar

= 3.9 bar

= 4.2 bar

= 1.0 bar

= 1.4 bar

= 1.8 bar

= 2.2 bar

= 2.6 bar

= 3.0 bar

= 3.4 bar

= 3.8 bar

= 2.2 bar = 9.1 bar

in the event of a fault

= 1.0 bar

= 1.4 bar

= 1.8 bar

= 3.5 bar = 5.4 bar

= 2.6 bar

= 2.9 bar

= 3.2 bar

7.9 bar

7.6 bar

7.3 bar

7.0 bar

6.7 bar

6.4 bar

6.1 bar

5.8 bar

W F p max,V pdischarge

p max

p max

p max

p max

p max

p max

p max

p max

p max

p max

p max

p min

p min

p min

p min

p min

p min

p min

p min

p min

p min

p min

p min,V p 0,max

possible remedial measures: Section 5.2.2

Fig. 16Schematic drawing of a PBU with one variable speed pump incl. pressure values and pressure zones

26

5

5.2.5Summary

The disadvantages of cascade operation areavoided. Generally, pressure reducers and largemembrane-type accumulators are not necessary.Making full use of the inlet pressure saveselectrical drive energy.

5.3PBU with speed control on all pumps (Hyamat VP)

5.3.1Features

• All pumps are variable speed

• Number of operating pumps depends on flow rate

• No pressure rise in the event of a fault/variablespeed pump breakdown

• Broad regulating range, optimum conditionswhen all pumps are running

• Constant discharge pressure

• Compensation for very high inlet pressurefluctuations possible

• With regard to fluctuations during operation,the adverse hydraulic effects on the public waternetwork are very low

5.3.2Calculation example

(also see section 5.2.2)

All calculations are performed as per section 5.1.2and 5.2.2 in accordance with example (4) pdischarge = pci = 5.4 bar

Even in the event of a fault, inadmissible pressurerises cannot occur with this type of PBU concept.

Therefore, floors 3 to 10 can be directly connectedto the PBU (Fig. 11) without any protective meas-ures. A constant discharge pressure pdischarge isguaranteed at all times.


see also section 5.2.3

Nflpr = 1.3 � 2

From this equation can be deduced that the lowesttwo floors, namely the basement and the groundfloor, would require protection. As, however, thebasement, ground floor as well as 1st and 2nd

floors are not connected to the PBU anyway thiscan be disregarded.

A special feature of this PBU concept is that even inthe event of a fault (e.g. breakdown of one variablespeed pump) a pressure rise is not to be expected.All other variable speed pumps continue operating.If required, the stand-by pump (also equipped withvariable speed control) can be started up.

Hence, floors 3 to 10 are supplied with waterwithout needing additional protective equipment.

Determining the maximum floor pressure pmax,fl

As in section 5.1.3, we take a static approachmeaning we do not assume any flow losses Σ (R x l + Z).

Hyamat VP

continuously variable

Speed control on all pumps

p

const.pci

Q

p 0

p ci

Q excessive on/off

constant

discharge

pressure p discharge

H

n pumpsn-1 pumps

Fig. 17:Performance chart of a PBU with speed controlon all pumps (Hyamat VP)

Choosing the correct PBU variant

27


The following is therefore applicable:

[29]

[30]

Example:

The following is applicable for the 5th floor:

N = 6; �pgeo,fl = 0.3 bar; pdischarge = 5.4 bar

�pgeo (floor 5) = N · �pgeo,fl = 6 · 0.3 bar

�pgeo (floor 5) = 1.8 bar

therefore,

pmax (floor 5) = 5.4 bar - 1.8 bar

pmax (floor 5) = 3.6 bar


pdischarge = Required pressure downstream ofthe PBU

pmax,fl = Maximum pressure per floor

pci = Cut-in pressure / setpoint

�pgeo (floor X) = Static pressure loss for floor X

Determining the minimum floor pressure pmin,fl

The following is also applicable for floor 5:

pmin (floor 5) = 3.0 bar

5.3.4PBU with speed control on all pumps (Hyamat VP) – Possible effects

All pumps are variable speed.

In the event of a fault (breakdownof one variable speed pump), theHyamat VP unit continues operat-ing with the available variablespeed pumps.

The supply pressure is not subjectedto any fluctuations.

Conclusion:

Additional measures are not re-quired.

In buildings with more than10 floors, it is normal to definepressure zones.

5.3.5Summary

Even if one frequency inverter unitbreaks down, the discharge pressureremains constant (in the Hyamat Vconcept, by contrast, the PBUwould automatically change over tocascade operation). Any hydraulicequipment limiting the pressure isnot required.

Fig. 18Schematic drawing of a PBU, all pumps are variable speed con-trolled, incl. pressure values and pressure zones



supply pressure

Top pressure zone,

supply via PBU

Basement

Ground floor

10th

9th

8th

7th

6th

5th

4th

3rd

2nd

1st

Hyamat VP

± 0 m

+ 3.0 m

+ 6.0 m

+ 9.0 m

+ 12.0 m

+ 15.0 m

+ 18.0 m

+ 21.0 m

+ 24.0 m

+ 27.0 m

+ 30.0 m

+ 33.0 m

= 2.1 bar

= 2.4 bar

= 2.7 bar

= 3.0 bar

= 3.3 bar

= 3.6 bar

= 3.9 bar

= 4.2 bar

= 1.0 bar

= 1.4 bar

= 1.8 bar

= 2.2 bar

= 2.6 bar

= 3.0 bar

= 3.4 bar

= 3.8 bar

= 2.2 bar

= 1.0 bar

= 1.4 bar

= 1.8 bar

= 3.5 bar

= 5.4 bar

= 2.6 bar

= 2.9 bar

= 3.2 bar

W F p max,V

p discharge

p max

p max

p max

p max

p max

p max

p max

p max

p max

p max

p max

p min

p min

p min

p min

p min

p min

p min

p min

p min

p min

p min

p min,V

pdischarge = pci = constant [bar]

pmax,fl = pdischarge - �pgeo (floor X) [bar]

6 Overview – Connection types for drinking water installations 6Overview – Connection types for drinking water installations

2928

No adverse effects on

supply network

Demand peaks

are covered

Constant inlet pressure

Risk of contamination

No risk of contamination

Additional pressure loss

Dampened impact on supply network


Wasted energy

(max. +0,3/-0,2 bar)

Tank is not required Normally

not required

Observe pump curve

profile

Observe pump curve

profile

Exploitation of design

inlet pressure

Inlet pressure

fluctuation must

be limited

Inlet pressure may

fluctuate slightly

Full exploitation

of inlet pressure

Greater inlet pressure

fluctuation permitted

Full exploitation of

inlet pressure

Inlet side

Indirect connection Direct connection

Unpressurized tank

for volume balancing

Flow isdistributedacross pumpsaccording todemandDischargepressurefluctuation

Constantdischargepressure

Wastedenergy

Optimum

Good

Possible

Unfavourable

Constantdischargepressure

Minimumenergydemand

ConstantdischargepressureMinimumenergy demandHighly dynamicregulatingpotential

No risk of contamination

Reduction of switching frequencies

Additional pressure loss

Not required

Pressurepeaks arereduced

See also section 9

Low pressurelosses highflow rates

at

Reduction ofswitchingfrequency

Excessiveon/off isavoided

Excessiveon/off isavoidedThrottled filling

Unthrottledre-filling

Balancing ofdynamicfluctuations inconsumption

Thottled filling

Unthrottledre-filling

Pressure boosting unitService water

Consumer side

Pressure-dependent cascade control

Arrangement example

One pump is variable speed

All pumps are variable speed

Legend

Unpressurized inlettank

Direct-flow membrane-typeaccumulator with dualconnection

Pressure reducerNon-return valve

Solenoid valve(dyn. consumer)

Drinking water valve

Service water valve

Supply network Membrane-type accumulator Cascade-controlled pump

Variable speed pump

Hyamat K

Hyamat V

Hyamat VP

PBU

p

p

p

pco

pci

pci

pci Const.

Const.

Q

Q

Q

Drinking water DW Service water SW

6Overview – Connection types for drinking water (to DIN 1988, always with stand-by pump) andservice water installations

7Overview – Connection types for fire-fighting units, wet risers7 Overview – Connection types for fire-fighting units, wet risers

30 31

Seite

nran

d

Direct-flow membrane-typeaccumulator with dualconnection

Pressurereducer

Time-controlledsolenoid valve

Membrane-type accumulator Cascade-controlled pump

Risk of contaminationdue to waterstagnation.

Tapping drinkingwater is not possible

Constant dischargepressure

Pressure zonesdecentralized

No DINrecommendation forpressure reducers

Switching frequency is limited(e. g. toilet flushing)

Adverse effects when tank is being filledand in the case of direct connection

Start-up via remote-electric controlledcontact possible

No excessiveon/off during fire-fighting duty

Consumer side

Fire hydrant

Fire hydrant with electriccontact

Toilet used regularly ensuresexchange of water

WC

WC

WC

WC

Signal line

Optimum

Good

Possible

Unfavourable

Legend

Unpressurized inlet tank

Supply network

To reduce the risk of back contamination it is important to ensure that time-controlled flushing of the fire-fighting system (1.5 x the pipe contents per week) takes place in directly connected pressure boosting units.

Pressure boosting system

pressure-dependent control

pressure-dependent cascade control

Hya-Solo D *)

Hya-Eco + Hyamat K*)

*)

p

p

pco

pco

pci

pci

Q

Q

FfW Fire-fighting waterDW Drinking water

QQnetw

FfW must be

lower than

Exploitation of

design inlet pressureHydraulic separation

Storage of water

No adverse effects onsupply netword


No DIN recommendation for

pressure reducers

Dampened effects on supply network

Inlet side

Indirect connection Direct connection

Unpressurized tank for

volume balancing

*Limited volume balancing as a standard, full volume balancing on option

Exploitation of

design inlet pressure

Inlet pressure

fluctuation has an

influence on the

system’s

characteristics

7Overview – Connection types for fire-fighting units, wet risers

Overview – Connection types for wet- / dry-type units

33

8 Overview – Connection types for combined installations

32

Cascade-controlled pump

Wall-mounted

fire hydrant

Variable speed pump

Drinking water valve

To reduce the risk of contamination in the connection pipe

it is important to ensure that time-controlled flushing of the

fire-fighting pipe branch (1.5 times the pipe contents per week)

takes place in drinking water operation (direct connection).

Fire-fighting operation is activated via the contacts

on the wall-mounted fire hydrants

**)

*)

ContactSignal line

Pressure boosting unit

Cascade control

Cascade control for all pumps

Arrangement example

One variable speed pump and pressure-dependentcontrol of fire-fighting pump

One variable speed pump

Hyamat K

Hyamat K

Hyamat V

Hya-Solo D **)

Hya-Solo D **)

Hyamat V

PBU

p

p

p

p

Selection of economicallydetermined pump sizes

Selection of economicallydetermined pump sizes

pA

pE

FL

Ftw

TW

DW

TW

DW

FL

Ftw

Set valueSet value D

Ftw

W

Q

Q

Q

Q

*)

*)

Optimum

Good

Possible

Unfavourable

Legend

W/D

Optimum

Good

Possible

Unfavourable

Legend

Wet/dry valve station

Pressure boosting unit

Cascade control

Hyamat KHya-Solo D

Hyamat K

PBU

Arrangement example

p

p

p

p

Δ

Δ

Fire-fighting pumps

Filling pump

pA

pA

pE

pE

Q

Q

W / D

Cascade-controlled pump

Wall-mounted fire

hydrant

*)

*)

*)

To reduce the risk of back contamination

it is important to ensure that time-controlled

flushing of the fire-fighting unit

(1.5 x the pipe contents per week)

takes place in directly connected

pressure boosting units.

*)

8Overview – Connection types for combined installations: Drinking water and fire-fighting water

Service water and fire-fighting water

Seit

enra

nd

9

N.B.: Depending on the specific unit conditions, the requirements for pressure boosting units must beagreed with the manufacturer.

The connection types and the installation of accumulators must be realized in compliance with thewater provider’s and manufacturer’s specifications for the specific unit.

9Overview – Connection types for wet- / dry-type units

NB: If special solutions are involved, specific unit requirements must be agreed with the manufacturer!The connection types must be determined in compliance with the water provider’s and manufacturer’srequirements.

10Accumulator selection / calculations

35

10 Accumulator selection / calculations

34

Selection of re-fill valve by means of

p and Qinl,min D

V = (Q - Q ) · t [m ]IT D min3

Determining the storage volume by the

volume difference / time method.

pinl,min p

2”2 x 2”

selected

nominal diameter1”

1 / î1 2

3

3

N.B.: The size of the tank is proportional

to that of the re-fill valve.

Standardi.e. the water supply network is capable of

providing at any time.Vmax

Tank selection

V = 0.03 ·V (Q ) [m ]IT Dmax3

Unpressurized inlet tank

for indirect connection

Membrane-type accumulator for direct

connection

QD

Q

m3m /h3

Vtot

Total volume of accumulators on inlet

pressure side of PBU

The minimum volume should not be

less than 0.3 m3

Total accumulatorvolume on inlet

pressure side of pumps

Maximum flowrate of a PBU pump

0.3

0.5

0.75

Legend:

Pinl,min

Pinl,max

Vtot

VIT

t

QD

Qmin

Qmax

Minimum available pressure on filling side

Maximum inlet pressure on filling side

Maximum volume flow of a PBU pump

Total accumulator volume in m3

Usable volume of atmospheric inlet tank

Buffering period of inlet tank in h

Design flow rate of PBU

Re-fill volume flow under minimum inletpressure (p ) conditionsinl,min

Maximum permissible re-fill volume flownetwork extraction)(=

=

=

=

=

=

=

=

=

=

Inlet side

Vmax,p

Vmax,p

This selection allows for a buffer

volume sufficient for approx. 100 s in the

case of maximum water consumption

and if re-filling does not take place.

10Accumulator selection / calculations

Some of the following design information is taken from the DIN 1988 standard and other parts are spe-cific KSB infomation. They are to be considered as KSB recommendations. Determing the tank sizes of the PBU

In the case of consumers with very low demand

In compliance with PBU manufacturer’srequirements we recommend the installation of a

80 l standard accumulator

In the case of highly dynamic consumers

Consumer side

Pressure boosting units with variable speed control on one or all pumps(e. g. Hyamat V, Hyamat VP)

Membrane-type accumulators are normally not required in variable speed pump systems.

They have a negative influence on the control characteristics of a PBU.

Pump size

2

2

4

4

10

10

18

18

32 - 45

32 - 45

Numberof stages

2 to 10

11 to 25

2 to 10

11 to 25

2 to 7

8 to 20

2 to 7

8 to 16

2 to 6

7 to 12

Switchingoperations/h

23

14

23

14

17

9

17

9

14

9

Selection on the basis of the

consumer behaviour

Selection on the basis

of the Q . limitcrit

Sizing the accumulator

Qcrit.

p0

Pco

Pci

p

Q

Unstable

area

Stable

areaIndustrial operations

Residential buildingsOffice and administrationbuildingsHotelsDepartment storesHospitalsSchoolsFire-fighting systems withwater exchange lines

1.1 m /h3

2.2 m /h3

0.4 m /h3

Q lconsumer, smal

Obtain informationor perform selectionon the basis of theQ limitcrit

Yes No Legend:Q < Qconsumer, small crit .

V = Qtot consumer, small ·

Qconsumer, small = Low or permanent consumptiondependent on usage

Vtot = Total accumulator volume

V = Qtot crit. ·Qcrit. = Critical minimum flow of PBUp + 1co

Pco = PBU cut-out pressure

Pci = PBU cut-in pressure

p + 1A

S = Switching frequency

n = Number of pumps (incl. stand-by pump)

= Difference between cut-in/-out pressures

Pressure boosting units with

pressure-dependent or cascade control

(e. g. Hyamat K, Hya-Solo)

2.3 m /h

3.6 m /h

4.7 m /h

3

3

3

1.8 m /h3

p(co-ci)

p(co-ci)p(co-ci)

p(co-ci)

Pump size Numberof stages

Switchingoperations/h

Determining accumulator efficiency

Consumers with quick ON/OFF characteristics (solenoid valves)

4

6

8

10

2

Determining the max. re-fill volume

Duration of extraction t Flow volume extracted Q

Determining the gross accumulator volume

Example:

from diagram

tank efficiency

t

p [bar]0.50 1 1.5 2 2.5 3

P = 5 barci

p = Inlet pressure, accumulatorci

P = 2 barci

P = 2 bar ,ci

P = 1 barci

V = 1.5 l/s · 25 s = 37.5 l

V . = 37.5 l · 4 = 150 laccum

Chosen 180 l standard accumulator

t = 25 s , Q = 1.5 l/s

Q

Efficiency

Approximate estimation of the required accumulator efficiency with

given inlet pressure p and permissible pressure drop (p)ci

= Accumulator efficiency

= 4

p = Pressure drop

p = 1.0 barperm.

Vaccum. =

Customer:

Commerzbank AG

Fields of application:

Heating, air-conditioning,

water supply and disposal,

fire-fighting and sprinkler systems

Scope of supply:

294 pumps and some 2,000 valves.

Pumps:

Ama-Drainer, CPK, Compacta,

Etanorm, Eta-R, Etaline, Hyamat

with Movitec, Hyatronic, Rio and

Riotec

Valves:

BOA-Control IMS, BOA-Compact,

BOA-Compact-EKB, BOA-H,

BOA-S, SISTO, BOAX

Commissioned:

17.5.1997

Scope o f supp l y and t e chn i ca l da ta

Commerzbank headquar tersF rankfur t on the Ma in /Germany

H ighes t o f f i c e t owe r i n Eu ropeBUILDINGSERVICESENERGY

WASTEWATERWATER MININGINDUSTRY

BUILDINGSERVICES

The Commerzbank headquarters in

Frankfurt on the Main is the highest

office building in Europe and dom-

inates the skyline with its accom-

plished architectural features.

Impressive, too, is the number of

KSB products integrated in the

building’s various service systems

that reliably fulfil their daily tasks

to their owner’s complete satisfac-

tion: approximately 300 pumps and

2,000 valves of a wide variety of

types and sizes have safeguarded

safe and reliable fluid transport

since 1997. Our extensive product

scope, the know-how of our special-

ists and KSB’s uncompromising

quality management convinced the

customer to place his order with us.

This is without doubt a reference

we can be proud of.

For further information, contact us

on phone number

+49 69 94208-221, by email at

[email protected] or visit

our website at www.ksb.com.

0127

.103

1-10

bd

f

05/

05

CPK Mr. Muschelknautz Hyamat

37

11

11Dry running protectionSelection criteria for PBUs

“Dry running protection” is the protection of thepumping station against inadmissible operation(such as lack of water) and the timely shutdown ofthe PBU to protect the supply network.

The following presents an overview of the variousdry-running protection concepts.

11.1Protection of the supply network

By stipulating minimum pressures, the GeneralWater Supply Terms Ordinance (AVB Wasser V),the DIN 1988 and the future DIN EN 806 stand-ards endeavour to prevent consumers directlysupplied via a house connection being inadmis-sibly compromised as a result of PBU operation.

Possible causes for an inadmissible pressure dropat the house connection are for example:

• Insufficient supply network. The pressure of themains water pipe drops when considerablequantities of water are extracted.

• If the service pipe’s diameter is insufficient, thesupply pressure drops at the hand-over pointwhen considerable quantities of water are con-sumed.

• Pressures drop at the hand-over point if consider-able quantities of water are pumped via the PBU(e. g. due to large pumps and/or a large mem-brane-type accumulator downstream of the PBU).

An inlet pressure monitoring device is installed onthe PBU inlet side in order to monitor and observethe required minimum pressure of pmin,V = 1 bar.Depending on the unit, this monitoring equipmentcan either be a pressure switch or an analog pres-sure transmitter. Whenever the minimum pressureis reached the PBU should reduce the number ofoperating pumps.

Simultaneous stopping of all operating pumpsmust be avoided.

Alternatively, the possibility of an indirect connec-tion of the PBU providing sufficient protectionshould be examined.

11.2Protection of pressure boosting unit

High-pressure centrifugal pumps are mainlyemployed for PBUs and, apart from a few excep-tions, these are non-self priming pump types. Thismeans that the inlet / suction pipe must be con-stantly filled with water.

In essence, all protection concepts aim to preventinadmissible rises in temperature or, in the worstcase, the dry running of the pumps.

A distinction should be made between direct andindirect protection methods.

Direct protection:

• Flow control on the PBU inlet side

Indirect protection:

• Inlet pressure control upstream of the PBU– particularly in the case of cascade control(Hya-Eco and Hyamat K) – by making surethat the pumps can reach or exceed the cut-out pressure pco.

• Water level control in the inlet tank

• Pump performance monitoring (electrically)

• Temperature monitors on each pump (alter-natively)

Fig. 17:Pressure development at the consumer end of theservice pipe, i. e. upstream of the PBU, during start-upand shutdown of pumps

Permissible pressure

increasePermissible

pressure drop

Period of

operation Run-down time

Pump start-

up phase

pmin,V

0.0 bar

p2

p2

p1p1

≤ 1.0 bar

1.0

ba

r

≤ 0.5 pmin,V

Dry running protection

38

Conclusion:

Generally, PBUs must be protected against operat-ing with a lack of water.

As a whole host of connection types for PBUs anddifferent operating conditions exists, there is nosuch thing as a standard solution. The protectionconcept chosen must always suit the individualoperating conditions (see Fig. 20).

Direct connection

PBU protection concepts

Options

Flow monitoring + pressure monitoringdownstream of the PBU

Water level monitoring using a float switch

Pressure monitoring using adigital pressure transmitter � 0.5 bar

Water level monitoring using electrodes

Pressure monitoring using ananalog pressure transmitter � 0.5 bar

OptionsOptions

PBUPBU

PBU

PBU

PBU

Q PP

P

e.g. BMS

PBU not self-priming

After “lack of water” trippingmanual reset required

Indirect connection

Suction head operationSuction lift operation

Fig. 20:PBU protection concepts

11 Dry running protection

12Effects of inlet pressure fluctuations

Supply pressure fluctuations at the hand-overpoint (water meter) influence the operatingbehaviour of pressure boosting units.

12.1Indirect connection, Fig. 21

The PBU takes the required quantity of waterfrom an unpressurized inlet tank situated up-stream.

The tank filling device is usually sized such thatthe PBU’s nominal flow rate QN is reached undernormal inlet pressure (pinl) conditions. If the inletpressure drops to the minimum inlet pressurepinl,min this may lead to a significant reduction ofthe filling volume.

Example:

pinl,min = 1.0 bar

pinl,max = 3.1 bar

pinl = 2 bar (angenommen)

QN = 20 m3/h

Selection of float valve for pinl = 2 bar, Fig. 22

QN = 20 m3/h � 11⁄2 ”

at pinl,min = 1 bar � Q = 14 m3/h

This results in a filling volume reduction of 30%.

It should be noted that the stored volume will beused up under minimum inlet pressure conditionsand a water consumption of more than 14 m3/hover a prolonged period of time (risking a lack-of-water condition).

The PBU’s function is not impaired as long aswater is available.

12.2Direct connection, Fig. 23

12.2.1Inlet pressure fluctuations in the form ofpressure increase

When PBUs with cascade control are used (Hya-Eco, Hyamat K, Hya-Solo D) inlet pressurefluctuations (in this case in the form of pressureincreases) will directly influence the PBUs’ dis-charge pressure. Since cascade-controlled PBUshave an inherent discharge pressure fluctuation of �p(co-ci) + 0.3 bar (Fig. 24), the sum of dischargepressure fluctuation and inlet pressure fluctuationmust be examined to ensure that it is acceptablefor the consumers downstream. The maximumfluctuation range recommended by DIN 1988 is2.5 bar.

[31]

PBU

Fig. 21 Indirect connection

70

50

40

30

20

10

0

500

300

200

100

00 1 2 3 4 5 0 1 2 3 4 5

Q

m /h3

Inlet pressure p bar Inlet pressure p bar

Q

m /h3

2 x 2”

2”

DN 100

DN 80

1”

1 / ”12

14

Fig. 22Selection diagram for filling devices

PBU

Fig. 21: Direct connection

39

12Effects of inlet pressure fluctuations

�pPBU,max = �p(co-ci) + 0.3 + �pinl,max [bar]

40

Legend for [31]:

�pPBU,max = Maximum pressure differencedownstream of the PBU

�p(co-ci) = Switching pressure difference

�pinl,max = Maximum pressure upstreamof the PBU

If this is not the case, it is important to usean inlet side or discharge side pressure con-troller / reducer.

A negative effect of inlet pressure increaseis the shifting of the minimum flow rate forcontinuous operation (Qco at pco) and theminimum inlet pressure pinl,min toconsiderably larger cut-out flow rates atincreased inlet pressure, especially in thecase of PBUs with a low number ofstages.

The consequences are as follows (Fig. 24):

• Low flow rates (> Qco for pinl,min) lead to therisk of excessive on/off operation (very highswitching frequency of the PBU pumps).

• As a result of the cut-out of the last pump inoperation at flow rates > Qco audible pressuresurges in the pipes are to be expected.

Example:

Impact of inlet pressure increase on a real pumpcurve (Fig. 25), Hyamat K series.

Pump size: 0406

Qco = 1.5 m3/h at pinl,min

After an inlet pressure increase of 0.5 bar

pinl = pinl,min + 0.5 bar

the cut-out flow rate is

Qco = 3 m3/h.

Cascade-controlled PBUs have fixed pressure-dependent switching points for pump cut-in andcut-out.

In the case of direct PBU connection, the respec-tive inlet pressure is added to the discharge headof the pump(s).

The factory-set value for the cut-out pressure pco isnormally 0.3 bar lower than the maximumdischarge pressure of the pump (at Q = 0 m3/h).

Point 1 on the pump curve (Fig. 25) characterizesthe cut-out flow rate of the pump for the designinlet pressure pinl,min (not considering possibleafter-run time).

As a pump is always stopped whenever the cut-outpressure pco is exceeded, the conclusion in the caseof increased inlet pressure is that the pump stopswith a lower discharge pressure.

Point 2 demonstrates the increased cut-out flowrate at the lower pump discharge pressure.

The characteristic curves used as an exampleclearly show that especially with flat pump curves(fewer stages) one can expect an excessive flowrate increase at the cut-out point.

Fig. 24:The operating characteristics of a pressure boosting unitwith cascade control, i. e. without speed control

Impact of inlet pressure increase of 0.3 bar

Discharge pressure

Pressure fluctuation inherent to PBU

p (co - ci)

p (co - ci)

+ p inl,min + 0.3 bar

p E

p A

H 0

Q co Q DQ co

+ 0.3 bar

Example:

Pressure development of a system with 3 pumps

with increasing flow rate (consumption)

with decreasing flow rate (consumption)

12 Effects of inlet pressure fluctuations

41

12Inlet pressure fluctuations in the form of pressure decrease

12.2.2Inlet pressure fluctuations in the form ofpressure decrease

Inlet pressure fluctuations (in this case in the formof pressure decreases) which fall below the min-imum inlet pressure are particularly dangerous forPBUs.

Cascade-controlled PBUs have a nominal cut-outpressure margin of 0.3 bar. This means that themaximum pump discharge head is 0.3 bar abovethe cut-out pressure pco. As soon as the minimuminlet pressure drops by more than 0.3 bar, the PBU

pumps in operation can no longer reach the cut-out pressure!

0

Pumps per system

1

Point 1Point 2

3.02

4

6

8

10

12

2

3

4

5

6

/

/

2

3

4

5

6

3

6

9

12

15

18

4

8

12

16

20

24

5

10

15

20

25

30

6

12

18

24

30

36

7

14

21

28

35

42

8

16

24

32

40

48

9

18

27

36

45

54

14.4

pbar

A Hm

Qm /h3

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

0415

0413

0411

0409

0408

0407

0406

0405

0404

0403

0402

12.4

10.5

9.5

8.5

6.6

5.6

4.6

3.6

2.6

1.7

0

0.5 bar

7.5

0410

1.5

without stand-

by pump

with stand-

by pump

Characteristic curve

valvues and tolerarances

to ISO 2548, Annex B

Specifically selectedPBU for p inl,min

Fig. 25:Pump selection chart for Movitec V 4

42

13Causes of pressure surges

13.1Pressure surges caused by valves

All kinds of valves can, when they close quickly,lead to pressure surges.

The theoretic basis for calculating this phenom-enon is described in the formula by Joukowsky:

[32]

Legend for [32]

�H = Pressure increase

a = Propagation of a pressure wave at approx. 1000 - 1200 m/s

g = Acceleration due to gravity, approx. 10 m/s2

�v = Velocity difference

The full impact of the pressure surge can be math-ematically expressed by the following formula:

[33]

Legend for [33]

TC = Valve closing time

TR = Reflection time in the piping

l = Length of piping up to the location ofdisturbance

This means when the pressure wave returns andthe valve is closed, the pressure surge according toJoukowsky fully develops.

Remedy:

TC must be markedly longer than TR.

e.g.: TC � 2 · TR

13.2Pressure surges as a result of inlet pressurefluctuations in the case of PBUs with cascadecontrol

If the inlet pressure increases, the pump curvesshift upwards and the base load pump is stoppedat a higher volume flow (Fig. 27). This results inan increased flow velocity change as the pumpstops, thus generating pressure surges!

Remedy:

A pressure reducer/controller has to be installedupstream of the pressure boosting unit to preventdetrimental effects.

Impact of inlet pressure increase by 0.3 bar

Discharge pressure

Example:

Pressure development of a system with 3 pumps

with increasing flow rate (consumption)

with decreasing flow rate (consumption)

p (co -ci)

p E

p A

H 0

Q co, normal Q DQ co, inlet pressure increase by 0.3 bar

Fig. 27: Operating characteristics of a pressure boostingunit with cascade control, i. e. without speedcontrol

l

Valve

pressure wave

Location of

disturbance,

e.g. T-piece

Fig. 26: Pressure surge caused by valves

a�� = — · �v [m]

g

2 · lTC � TR = ——— [s]

a

13 Causes of pressure surges

43

14Standards, directives and statutory regulations


DIN 1988 (December 1988 edition)Codes of practice for drinking water installations (TRWI); general;- DVGW1 code of practice

Part 1, Generalincludes among others:Competences, technical terms, graphic symbols and designations

Part 2, Planning and operation; component parts, apparatus and materialsincludes among others:Piping units, valves, apparatus, drinking water heating units, drinking water tanks, drinking water treat-ment equipment, measuring and metering instruments.

Part 2, Sheet 1Compilation of standards and other technical specifications regarding materials, components, apparatus.

Part 3, Calculating the pipe diametersincludes among others:Calculation flow rate and flow pressure, application of conversion curve(s) of total flow to peak flow,selection of piping diameter, circulation pipes and circulation pumps, calculation examples; Annex A:forms for calculation

Part 3, Sheet 1, Calculation examples

Part 4, Protection of drinking water, drinking water quality controlincludes among others:Causes for impairment and endangering of drinking water quality, equipment preventing back flow,protection of drinking water in water heating units

Part 5, Boosting and pressure reductionincludes among others:Pressure boosting units and pressure reducers

Part 6, Fire-fighting and fire protection installationsincludes among others:Terms, configuration and requirements, commissioning

Part 7, Prevention of corrosion damage and calcareous deposit formationincludes among others:Prevention of damage due to interior and exterior corrosion and calcareous deposit formation

1 German Gas and Drinking Water Association

44

Part 8, Operation of plantsincludes among others:Commissioning, operation, damage and faults, maintenance information Annex A Information on maintenance measuresAnnex B Inspection and maintenance scheduleAnnex C Sample forms for commissioning and instruction reports

DIN 2000 (November 1973 edition)Centralized drinking water supply; principles for drinking water requirements, planning, constructionand operation of units

DIN 2001 (February 1983 edition)Individual drinking water supply; principles for drinking water requirements, planning, construction andoperation of units; DVGW code of practice

DIN 4109, Part 5 (October 1989 edition)Sound insulation in building construction

EN 1717 (February 1995 edition)Protection against pollution of potable water installations and general requirements of devices to preventpollution by backflow

DIN 4807, Part 5 (March 1997 edition)Direct flow membrane pressure vessels in drinking water installations

DIN 14200 (June 1979 edition)Nozzle discharge

IfSG – Protection Against Infection Act (01.2001)Act regulating the prevention of and protection against communicable diseases in humans

LMBG – Foodstuffs and Commodities Act (09.1997)Official food control law for food, tobacco, cosmetic products and other commodities to protect healthand to safeguard consumers’ rights

TrinkwV 2001 – Drinking Water OrdinanceRegulation for the quality of water for human use

VDI Directives Directives issued by the Association of German Engineers

Standards, directives and statutory regulations14

45


Group Group I Group III Group IVclassification

� PN 25p · V � 200 p · V > 200; p · V > 1000; > 1 bar

p · V � 1000Operating pressure > 1 bar Operating pressure > 1 bar

Single tests Pressure vessel code (DruckbehV) § 9, Testing prior to commissioning

In the case of a pressure vessel which has been subjected to an ac-ceptance test at another location – excluding the installation test – and

not applicable provided with an acceptance certificate accordingly, it is sufficient that the installation at the place of operation is checked by an expert and that this is confirmed in writing, e. g. through a commissioning/acceptance report

Pressure vessel code (DruckbehV) § 10Regular testing

(1) In accordance with sections 4 to 9, agroup IV pressure vessel must be subjected toregular testing carried out by an expert (e. g. TÜV) at defined intervals.

Regular testing not applicable not applicable

(4) Groups IV and VII pressure vessels mustbe subjected to internal tests every five years;pressure tests must be carried out every tenyears and external tests must be performedevery two years.

Allocation of Accumulator PN 10 ; 80 l PN 10; 180 l, 300 l, 400 l, 800 l, 1000 lmembrane type (PN 16; 12 l) PN 16; 80 l, 180 l, 300 l, 400 l, 800 l, 1000 lpressure vessel (accumulator) sizes

Regulation governing plant safety (BetrSichV, 27.09.2002 edition)

Excerpt (special, manufacturer-related aspects have to be considered)

Table 2:Allocation of membrane-type pressure vessels (accumulators) and tests according to pressure vessel code

46

15Inspection, maintenance and repair to DIN 1988, Part 8

Inspection, maintenance and repair: According the manufacturers’ operating instructions

Carried out by: Installation contractor

Interval: Annually unless otherwise specified by the manufacturer

Inspection, maintenance and repair15

47

16Nomenclature

16Nomenclature

Description Symbols Unit

Propagation velocity of a pressure wave a m/s

Simultaneity factor f -

Acceleration due to gravity (9.81 m/s2) g m/s2

Pump discharge head H m

Max. pump discharge head at zero flow rate (Q = 0) H0 m

Static head loss Hgeo m

Floor height Hfl m

Head loss HL m

Head increase ∆H m

Static pressure loss for floor X ∆Hgeo (floor X) m

Number of pumps (incl. stand-by pump) n -

Number of floors which have to be protected against Nflpr -inadmissible pressures by means of pressure reducers

Number of floors which can be supplied without PBU Nwithout PBU -

Pressure p bar

Maximum pump pressure at zero flow rate (Q = 0) p0 bar

Cut-out pressure, pressure at which one pump of a pco barpressure-controlled PBU cuts out

Cut-in pressure, pressure at which one pump of a pci barpressure-controlled PBU cuts in

Setpoint (of a speed controlled PBU)

Flow pressure at consumer pflow bar

Minimum flow pressure at consumer pmin,flow bar

Minimum flow pressure at consumer in floor N pmin,flow(N) bar

Minimum supply pressure (at hand-over point betweenlocal provider and consumer) pmin,V bar

Maximum pressure pmax bar

Maximum flow pressure at consumer pmax,flow bar

Maximum pressure per floor pmax,fl bar

Maximum supply pressure (at hand-over point betweenlocal provider and consumer) pmax,V bar

Required pressure downstream of the PBU pdischarge bar

Available pressure upstream of the PBU pinl bar

Minimum available pressure upstream of the PBU pinl,min bar

Maximum pressure upstream of the PBU pinl,max bar

Opening pressure of a by-pass valve pvalve bar

48


Pressure drop during pump start-up ∆p1 bar

Pressure increase during pump shutdown ∆p2 bar

Apparatus pressure loss ∆pap bar

Difference between cut-in/-out pressures ∆p(co-ci) bar

Maximum pressure difference downstream of the PBU ∆pPBU,max bar

Dynamic pressure difference ∆pdyn bar

Dynamic pressure loss per floor ∆pdyn,fl bar

Static pressure loss ∆pgeo bar

Static pressure loss per floor ∆pgeo,fl bar

Static pressure loss for floor X ∆pgeo (floorX) bar

Pressure loss per floor ∆pfl bar

Total pressure loss per floor ∆pfl,tot bar

Pressure fluctuation upstream of the PBU ∆pinl bar

Water meter pressure loss ∆pwm bar

Permissible pressure loss ∆pperm. bar

Mean pressure drop in consumer supply pipes ∆p/l mbar/m

Cut-out flow rate of the last pump in operation (without after-run period) Qco m3/h

PBU design flow rate = nominal flow rate of a PBU (V·max) QD m3/h

Maximum volume flow of a PBU incl. stand-by pump QDS m3/h

Fire-fighting water volume flow QFfw m3/h

Critical minimum flow rate of pressure-dependent cascade control Qcrit m3/h

Minimum flow rate Qmin m3/h

Maximum permissible volume flow of filling device Qmax m3/h

Maximum permissible volume flow from water supply network Qmax,netw m3/h

Nominal flow rate of water meters Qn m3/h

Nominal flow rate of PBU QN m3/h

Filling volume flow Qfill m3/h

Water supply network volume flow Qnetw m3/h

Low or permanent consumption dependent on usage Qconsumer, small m3/h

Nomenclature16

49

16Nomenclature


Volume flow difference ∆Q m3/h

Volume flow change of a highly dynamic consumer ∆Qmax,dyn m3/h

Change of nominal flow rate per pump ∆QPU m3/h

Switching frequency S -

Period of time required to fill a hydrant pipe up to the wall-mounted t sfire hydrant which is most unfavourably located

Inlet tank buffering period t h

Time difference ∆t s

Closing time of valve TC s

Reflection time in the pipeline TR s

Flow velocity v m/s

Flow velocity difference ∆v m/s

Usable volume of the atmospheric inlet tank VIT m3

Accumulator volume Vaccum. m3

Gross accumulator volume Vgross m3

Total accumulator volume Vtot m3

Contents of network piping Vpipe m3

Calculation flow rate of a tap/fitting Vcal m3

Total accumulator volume Vtot m3

Volume difference ∆V m3

Nominal flow rate of water meters V·n m3/h

Minimum flow rate V·min m3/h

Nominal flow rate of a PBU = design flow rate of a PBU (QD) V·max m3/h

Maximum volume flow of a PBU pump V·max,p m3/h

Calculation flow rate of a wall-mounted fire hydrant V·cal l/s

Peak flow rate of a PBU V·peak l/s

Sum of all calculation flow rates of all taps/fittings to be supplied ΣV·cal l/s

Pipe friction and other losses Σ(R · I+Z) bar

Pipe friction and other losses from supply pipe up to PBU Σ(R · I+Z)inl bar

Pipe friction and other losses downstream of PBU Σ(R · I+Z)discharge bar

Mean pressure drop in a pipe R bar/m

Individual friction losses Z bar

Pipe length I m

Sum of pipe length from PBU to the hydraulically least favourable extraction point ΣIdischarge m

Accumulator efficiency e -

Temperature factor j -

50

17References

– DIN 1988Codes of practice for drinking water installations

– DIN EN 806, Parts 1 und 2Codes of practice for drinking water installations

– Kommentar zu DIN 1988, Teil 1 bis 81st edition 1989

– FeurichSanitärtechnik 1999 (Sanitation Engineering)

– KSB brochure / manual“Selecting centrifugal pumps”5th edition 2005

17 References

52

Worksheet 1

Minimum Calculation flow rate for extraction offlow pressure cold or heated

mixed water1) drinking water Type of drinking water extraction point only

pmin,flow V·cal V·cal V·calcold warm

bar l/s l/s l/s

0.5 Water tapwithout spray2) DN 15 – – 0.30

0.5 DN 20 – – 0.500.5 DN 25 _ _ 1.001.0 with spray DN 10 – – 0.151.0 DN 15 – – 0.15

1.0 Showerheads DN 15 0.10 0.10 0.20

1.2 Flush valve to DIN 3265 Part 1 DN 15 – – 0.701.2 Flush valve to DIN 3265 Part 1 DN 20 – – 1.000.4 Flush valve to DIN 3265 Part 1 DN 25 – – 1.001.2 Flush valve for urinals DN 15 – – 0.30

1.0 Domestic dishwasher DN 15 – – 0.151.0 Domestic washing machine DN 15 – – 0.25

Mixer for1.0 combined bathtubs/shower DN 15 0.15 0.15 –1.0 bathtubs DN 15 0.15 0.15 –1.0 kitchen sinks DN 15 0.07 0.07 –1.0 sink units DN 15 0.07 0.07 –1.0 bidets DN 15 0.07 0.07 –

1.0 Mixer tap DN 20 0.30 0.30 –

0.5 Cistern to DIN 19 542 DN 15 – – 0.13

1.0 Electric water heater DN 15 – – 0.10 3)

Worksheet 1Calculation flow rates and minimum flow pressures

Step 1:

Determining the calculation flow rates of all taps/fittings and apparatus to be connected according to manufacturer’s specifications (Rough evaluation on the basis of reference values according toDIN 1988, Part 3, Table 11).

1) The temperatures for the calculation of flow rates for mixed water extraction were assumed to be 15°C for cold and 60°C for heated drinkingwater.

2) Taps with screwed hose connections (without spray): the pressure loss in the hose (up to 10 m) and in connected apparatus (e. g. lawn sprinkler) isgenerally taken into account via the minimum flow pressure. In this case, the minimum pressure is increased by 1.0 bar to 1.5 bar.

3) With fully opened throttle screw

Table 3: Reference values for minimum flow pressure and calculation flow rates of common drinking waterextraction points

Comment:In the case of similar extraction points and apparatus with larger flow rates or minimum flows which have not beenspecified in this table, information should be obtained from the respective manufacturers in order to calculate thepiping diameter

Step 2:

Adding the calculation flow rates = ΣV·cal

Calculation flow rates and minimum flow pressures

53

Worksheet 2Calculating the peak flow rate

Worksheet 2Calculating the peak flow rate

Step 3:

Calculating the peak flow V·peak in accordance with diagram (from DIN 1988, Part 3, Fig. 3) below.

(For more accurate calculations, we recommend using tables 12 to 17 of DIN standard 1988, Part 3,especially when higher outputs are required)

The simultaneity of water extraction in particular must be considered – if required, upon consultationwith the operator – for all drinking water installations which have not been specified here.

100

100 150

176.5

4.4

200 300 400 500

100

70

70

70

7

7

7

0.7

0.7

0.7

50

50

50

5

5

5

0.5

0.5

0.5

40

40

40

4

4

4

0.4

0.4

0.4

30

30

30

3

3

3

0.3

0.3

0.3

20

20

20

2

2

2

0.2

0.2

0.2

15

15

15

1.5

1.5

1.5

0.15

0.15

0.15

10

10

10

1.0

1.0

1.0

0.10.1

0.1

Range of application:

Residential buildings

Office and adminis- tration buildings

Hotels

Department stores

Hospitals (wards equipped with beds only)

Schools

V < 20 l/scal

V in l/scalTotal flow rate

V > 1.5 l/scal

V = V from 0 . to1 1 . 5 l / scal peak

Pe

ak flo

w V

inl/s

peak

V > 0.5 l/scal V < 0.5 l/scal

Range of application:

Residential buildings

Office and adminis-tration buildings

Hotels

Department stores

Hospitals (wards equipped with beds only)

Schools

V > 20 l/scal

A rough evaluation can be made for residential buildings on the basis of a total flow rate of ΣV·cal = 2.0 l/s per livingunit.

Fig. 26: Peak flow rate V·peak in l/s as a function of total flow rate ΣV·cal in l/s

54

Worksheet 3

Worksheet 3Flow rates

Water flow rate of fire-fighting hose nozzles1) according to DIN 14 200

Pressure Internal diameter d in mm

p 4 3) 6 6) 8 9 4) 10 12 7)

bar Water flow rate Q in 1/min

3.0 18 41 73 93 115 165

3.5 20 45 79 100 125 180

4.0 21 48 85 105 130 190

4.5 22 50 90 115 140 200

5.0 24 53 95 120 150 215

6.0 26 58 105 130 160 235

7.0 28 63 110 140 175 250

3) Corresponds to fire-fighting hose nozzle DM (d5 = 4)4) Corresponds to fire-fighting hose nozzle CM (d5 = 9)6) Corresponds to fire-fighting hose nozzle DM (d2 = 6)7) Corresponds to fire-fighting hose nozzle CM (d2 = 12)

to DIN 14 365, Part 1

Frequently applied flow rates for fire hydrants

Table 4: Flow rates of fire-fighting hose nozzles

Requirements as per the following standards

DIN 14 461-1 (Delivery valve installation with semi-rigid hose) requires water volumes of 100 l/min at3 bar and simultaneous operation of three wall-mounted fire hydrants (3 x 1.67 l/s).

DIN 1988/6: The piping system must be designed to deal with a maximum water volume of 2 x 24 l/min (2 x 0.4 l/s) at 2 bar (wall-mounted fire hydrant, type S).

Flow rates

55

Worksheet 4

Worksheet 4Water meters

Pressure losses �pwm of water metersStandard values

Nominal Pressure loss �pflow rate at V·max (Qmax) to

Flowmeter type V·n(Qn) DIN ISO 4064, Part 1m3/h mbar

max.

Turbine flowmeter < 15 1000

Woltman type � 15 600flowmeter (vertical)

Woltman type � 15 300flowmeter (parallel)

As a rule, the water meter type, quantity andsize are determined by the local waterprovider.

If the local water provider determines thesize of the water meter, then the water meterpressure loss specified by the provider mustbe applied.

The following applies according to DIN ISO 4064, Part 1:

[34]

V·n (Qn) applies to permanent consumption

V·max (Qmax) applies to short-term peak consumption

V·n (Qn) = 0.5 V·max (Qmax)

Connection, nominal and maximum flow rate of water meters to DIN ISO 4064, Part 1

ConnectionFlowmeter type Thread size Connection size Nominal Maximum

to (nominal flange size) flow rate *) flow rateDIN ISO 228, Part 1 DN V·n (Qn) V·max (Qmax)

m3/h m3/h

G 1/2 B – 0.6 1.2

Positive G 1/2 B – 1 2

displacement G 3/4 B – 1.5 3

and turbine G 1 B – 2.5 5

flowmeters G 1 1/4 B – 3.5 7

G 1 1/2 B – 6 12

G 2 B – 10 20

– 50 15 30

– 50 15 30

– 65 25 50

Woltman flowmeter – 80 40 80

– 100 60 120

– 150 150 300

– 200 250 500

*)The nominal flow rate is a water meter specification. According to DIN ISO 4064, Part 1, thread sizes for a given nominal flow V·n (Qn) can alsobe taken from the class directly above or below those indicated in the table for the respective values.

Table 6Flow rates for water meters

Table 5Water meter pressure losses

Water meters

56

Worksheet 5 Filters, drinking water heating systems,

pressure losses in consumer supply pipes

Worksheet 5Filters, drinking water heating systems, pressure losses in consumer supply pipes

Filter-induced pressure losses

A reference value of 200 mbar can be applied for filterswith V·max = V·peak.

Pressure loss �pDH of drinking water heating systems for several extraction points

Reference values:

Pressure lossHeater type �pDH

1)

bar

Electric through-flow water heater,thermally controlled 0.5hydraulically controlled 2) 1.0

Electric or gas water heater withstorage tank, nom. volume up to 80 l 0.2

Gas through-flow water heater andcombined gas heater for warm waterand heating systems to DIN 3368,Parts 2 and 4 0.8

1) These values do not include the pressure loss caused by safety and connection valves/fittings

2) Corresponds to the required switching pressure difference

Table 7Pressure losses of drinking water heaters

To calculate the pressure loss of further apparatus(e. g. water softening or dosing equipment) obtainrelevant manufacturer’s data, if required.

Pressure losses of consumer supply pipes down-stream of the PBU

Evaluation to DIN 1988, Part 3:

Pipe length from PBU to Mean pressure drop inleast hydraulically favourable consumer supply pipes

extraction point �p (R· l + Z)downstream— = ————————Σldownstream l Σldownstream

m mbar/m

� 30 20

> 30 � 80 15

> 80 10

In the planning phase the system designer is however required to perform a detailed calculationof the pressure losses.

Table 8Pressure loss evaluation of consumersupply pipes downstream of PBU

57

Worksheet 6

Worksheet 6Conversion of discharge head H into pressure increase �p

[35]

�p = pressure increase in pa (1pa = 1 N/m2)(1bar = 100 000 pa)

� = Density in kg/m3

g = Acceleration due to gravity = 9.81 m/s2

H = Discharge head per pump in m

In practice, the value assumed for acceleration due to gravity (g) is 10 m/s2

and for density � 1000 kg/m3

The above equation is therefore simplified:

[36]

�p = Pressure increase in bar

H = Discharge head in m

Both equations also apply to static pressure losses,e. g. �pgeo , and the static head losses, e. g. Hgeo.

Therefore:

[37]Hgeo

�pgeo � —— [bar]10

H�p � —— [bar]

10

�p = � · g · H

Conversion of discharge head H into pressure increase �p

58

Worksheet 7

Worksheet 7Head losses of steel pipes

01

01001

0001

012

013

014

001

05 02 01 5 2 1 5,0

2,0

1,0

50,0

20,0

10,05

5

5

05005

0005ls/m

/h35

Flo

w r

ate

QS

ourc

e: S

ele

cting c

entr

ifugal pum

ps, K

SB

Head loss HL

55,0

5,0

2

2

2

02002

0002

22

21

1

mm 51 = d

s/m 0,5 = v

0,4 5,3 0,3 5,2 0,2

5,1 52,1 0,1 8,0

6,0 5,0 4,0

3,0

02

52

23

04

05

56

08

001

521

051

571

002

052

003

053

004

005

006

007

008

009

0001

0021

0041

0061

0081

0002

mm 001

New

un

mac

hin

ed s

teel

pip

es, s

eam

less

Fig. 27: Head losses HL for new unmachined steel pipes, seamless (k= 0.05 mm)

Head losses of steel pipes

59

Worksheet 8Head losses of low friction pipes

Worksheet 8Head losses of low friction pipes

Fig. 28: Head losses HL for low-friction pipes (k ≈ 0)(For plastic pipes when t � 10°C multiply by the temperature factor �).

01

01001

0001

012

013

014

001

05 02 01 5 2 1 5,0

2,0

1,0

50,0

20,0

10,05

5

5

05005

0005ls/m

/h35

Flo

w r

ate

QS

ourc

e: S

ele

cting c

entr

ifugal pum

ps, K

SB

Head loss HL

55,0

5,0

2

2

2

02002

0002

22

21

1

0,4 5,3 0,3 5,2

0,2

5,1 52,1 0,1 8,0

6,0 5,0

4,0

3,0

02

52

23

04

05

56

08

001

521

051

571

002

052

003

053

004

005

mm 001

Pla

stic

an

d d

raw

n m

etal

pip

es

1,1

0,1

9,0

8,00

02Te

mp

era

ture

t

Temperature factor

04o C

06

H-c

orr

ectio

n fo

r p

lastic p

ipe

sL

mm 51 = d

s/m 0,5 = v

60

Worksheet 9 Permissible flow rate criteria of a PBU

Nominal service Max. total flow upstream of Max. permissible flow rates for direct connection

pipe diameters PBU and consumer of a PBU without pressurized inlet tank

pipes without PBU

DN I IIa IIb

Qmax at v < 2.0 m/s Qmax at v < 0.15 m/s Qmax PBU at v < 0.5 m/s

m3/h

25 / 1" 3.50 0.26 0.88

32 / 1 1⁄4" 5.80 0.43 1.45

40 / 1 1⁄2" 9.00 0.68 2.30

50 / 2" 14.00 1.06 3.50

65 24.00 1.80 6.00

80 36.00 2.70 9.00

100 57.00 4.20 14.00

125 88.00 6.60 22.00

150 127.00 9.50 32.00

200 226.00 17.00 57.00

250 353.00 26.50 88.00

300 509.00 38.00 127.00

Worksheet 9Permissible flow rate criteria of a PBU

Permissible flow velocity in service pipe(to DIN 1988 Part 5, section 4.4.1)

I: The total flow velocity upstream of the PBU and upstream of the consumer pipes without PBUmust not exceed 2.0 m/s.

For direct connection to a PBU without pressurized inlet tank the difference in flow velocity in theservice pipe as a result of starting and stopping the PBU pumps must not exceed the followingvalues:

IIa: v < 0.15 m/s by one (the largest) single pump

IIb: v < 0.5 m/s by simultaneously stopping all PBU duty pumps

The table provides information on flow rate criteria for the specified nominal service pipe diametersdepending on the following:

– permissible flow velocity ( IIa) and

– its change as a result of the number of pumps started / stopped (IIb) and

– total flow rate (I).

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