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Overow valves Type OFV 20-25 Type OFV-SS 20-25

REFRIGERATION AND

AIR CONDITIONING Technical leaet

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2 RD7GD302 → DKRCI.PD.HQ0.A1.02 / 520H1728 Danoss A/S (AC-DSL/MWA ), 11 - 2006

Technical leaet Overow valves, type OFV, OFV-SS 20 - 25

Contents Page

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Understanding the OFV in practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Adjusting set pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Computation and selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Capacity calculation or derost pressure regulating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Plant applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Material specication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Connections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Dimensions and weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

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Danoss A/S (AC-DSL/MWA ), 11 - 2006 RD7GD302 → DKRCI.PD.HQ0.A1.02 / 520H1728 3


Introduction

Features

OFV are angle-way over ow valves, whichhave ajustable opening pressure and cover thedierential pressure range (∆P): 2 - 8 bar (29 - 116psi). The valve can be closed manually, e.g. duringplant service and have backseating, enabling thespindle seal to be replaced with the valve stillunder pressure.

The valves are especially designed to preventuttering due to low velocity and/or low density.In consequence it is possible to apply the valveswith wide uctuations in capacity demands,i.e. rom maximum perormance to part load. Aexible O-ring provides perect sealing over theseat.

Applicable to all common non ammablererigerants including R717 and non corrosive

gases/liquids dependent on sealing materialcompatability.

Full temperature range packing gland–50/+150°C (–58/+302°F)

Maximum operating pressure:40 bar g (580 psig)

Three unctions in one valve. The OFV valvecombines the unctions o an overow valve, acheck valve and a stop valve

Classication: To get an updated list o certication on the products please contactyour local Danoss Sales Company.

Special eatures or OFV-SS- Low temperature stainless steel housing and

bonnet- Low temperature packing gland -60/+150°C

(–76/+302°F)- Maximum operating pressure 52 bar

(754 psi g)

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Design

Technical data

ConnectionsAvailable with the ollowing connections:

Welding DIN (EN 10220)

Welding ANSI (B 36.10 Schedule 80)

Packing gland OFV The “ull temperature range” packing glandconsists o a double O-ring sealing arrangementcombined with permanent lubrication rom agrease reservoir. This ensures perect tightnessthroughout the whole range: –50/+150°C(–58/+302°F).Flexible O-ring provides perect sealing over theseat.

Packing gland OFV-SS The stainless steel packing gland comprises aspring loaded seal packing gland which ensures aperect tightness in the range:-60/+150°C (-76/+302°F).

The packing glands are equipped with a scraperring to prevent penetration o dirt and ice intothe packing gland.

Pressure Equipment Directive (PED)OFV valves are approved and CE-marked inaccordance with the Pressure EquipmentDirective - 97/23/EC.

For urther details / restrictions - see InstallationInstruction

Installation The valve is designed to resist very high internalpressure, but as to the pipe system in general,hydraulic pressure caused by thermal expansionsin entrapped rerigerants should be avoided. For

urther inormation please see OFV installationinstruction.

RerigerantsApplicable or all rerigerants and noncorrosive gases/liquids, dependent on sealingmaterial combability.Flammable hydrocarbons are notrecommended. For urther inormation pleasecontact your local Danoss Sales Company.

Temperature rangeOFV: –50/+150°C (–58/+302°F)OFV-SS: –60/+150°C (–76/+302°F)

Pressure rangeMaximum operating pressure:OFV: 40 bar g (580 psig)OFV-SS: 52 bar (754 psi g)

Set pressure (∆p): 2 - 8 bar (29 - 116 psi).

Example o Marking Ring, Valve type OFV.

OFV

Nominal bore DN≤ 25 mm (1 in.)

Classifed or Fluid group I

Category Article 3, paragraph 3

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Adjusting set pressure

Fig. 2Set pressure as a unction o the spindle turns

The set pressure is the pressureat which the valve starts toopen.

The set pressure is adjustable inthe range 2 - 8 bar dierentialpressure. When the valve isdelivered, a distance piece issupplied seperately with thevalve. The distance piece can be

mounted under the spring, thusincreasing the initial tension o the spring. Thereore the valvecovers the complete range 2- 8 bar dierential pressure, asollows:

2 - 6.5 bar dierential pressurewithout distance piece.3.5 - 8 bar dierential pressurewith distance piece.

* see material specication and installationan maintenance instruction or OFV.

* S e t p r

e s s u r e

w i t h d

i s t a n c e

p o s. 2

3

* S e t p r

e s s u r e

w i t h o u t d i

s t a n c e

p o s. 2

3

Spindle turns

Understanding the OFV inpractice(when working in a derostingapplication)

As ∆Pover is plant specic, it ollows that the totalworking pressure (∆Ptotal = ∆Pset + ∆Pover) is plantspecic too. By adjusting the opening dierentialpressure ∆Pset it is possible to adjust the workingpressure ∆Pset + ∆Pover until you get the required

derosting pressure.

Fig. 1

How the OFV works The opening pressure o the OFV can be adjustedto a specic dierential pressure ∆Pset by turningthe spindle. ∆Pset indirectly determines the de-

rosting pressure. As illustrated in g. 1 the OFVwill work at a pressure somewhat higher than∆Pset, namely the ∆Ptotal which will be situatedsomewhere in the area marked with grey in g. 1.

Derosting pressure ≈ Evaporating pressure +∆Pset + ∆Pover.

Important! The OFV valve is back pressure dependent.

min. temperature

Condensing temperature/pressure

∆ P

t o t a l

∆ P

o v e r

∆ P

s e t + ∆

P o v e r

Evaporating temperature/pressure

∆ P

s e t

max. temperature(derosting temperature)

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Computation and selection

Fig. 3.k v values or OFV 20 - 25

The capacity o the OFV valves can be calculatedby the ollowing ormulas:

Liquids without phase change

Liquids with phase change (e.g. pressure control during derost)

G: mass ow (kg/h)

k v: ow rate (m3 /h) (the k v value isdependent on ∆Pover, see g. 3).

ρ: density, liquid (kg/m3)

∆Pbar = dierential pressure (bar) ∆Pbar = ∆Pset + ∆Pover

Derosting pressure ≈ Evaporatingpressure + ∆Pset + ∆Pover

Capacity calculation orderost pressure regulating

Table 1: Max. mass ow (GOFV ) or OFV 20 and OFV 25 with R717

Note: the calculation is based on ormula or "liquids with phase change" in the paragraph "Computation and selection".

Guide line: Derost capacity GOFV ~ (2 – 3) × G0

Evaporating temperature –10°C –20°C –30°C –40°C –50°C

Derosting temperature 10°C

Table 2: Calculating o rerigerant mass ow G0

Q0: Capacity o the evaporator (kW)Note: the calculation is based on pump circulating system (Liquid temperature = Evaporating temperature)

Evaporating temperature –10°C –20°C –30°C –40°C –50°C

Mass ow G0 (kg/h) 2.780 × Q0 2.712 × Q0 2.651 × Q0 2.595 × Q0 2.544 × Q0

Example:An evaporator in a rerigerant plant has a capacityo Qo = 150 kW and a evaporating temperature o –40°C.

The derosting temperature has to be controlledwith an OFV valve.

Table 2: G0= 2.595 × Q0 = 389 kg/h The derosting capacity in this example is2.5 × G0.GOFV ≥ 2.5 × 389 = 972 kg/h.OFV 25 is selected (GOFV 25 max. = 2156 kg/h (table 1)).

Mass ow GOFV 25 (kg/h)

(∆Pover = 1.5 bar ⇒ k v = 1.5 m3 /h)1666 1906 2059 2156 2216

OFV 20

Mass ow GOFV 20 (kg/h)

(∆Pover = 1 bar ⇒ k v = 0.52 m3 /h)577 661 714 747 768

OFV 25

G = k v √ρ× ∆Ptotal ×1000

G = k v × 0.78 √ρ× ∆Ptotal ×1000

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Plant applications

Hot gas supply

Floodedreturn line

Liquidsupply

Pressure/temperature control during hot gasderosting

In order to obtain efcient hot gas derostingthe temperature (pressure) must be increased

to approx. 10°C (50°F). The OFV is the optimalsolution or controlling the derosting pressureand thus the corresponding temperature. It isrecommended to start the derosting cycle byclosing the GPS valve in the liquid supply line andallowing some o the cold liquid contained in theevaporator to return to the liquid separator. Close

the GPS valve in the suction line and ater a delayopen the solenoid valve in the hot gas supply inorder to build up the derosting pressure in theevaporator. When the derosting pressure reachesthe set OFV-pressure, the OFV will open and the

derosting pressure will increase to the workingpressure ∆Pset + ∆Pover.

Ater derosting, it is normal practice to open theGPS in the return line to equalize the pressureto the suction side beore opening to the pumpside.

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Material specifcation

No. Part Material EN ISO ASTM

1 Housing Steel P285 QH

EN10222-4LFA350

2 Bonnet, Flange Steel P275 NL1

EN10028-3

3 Bonnet, Insert Steel

4 Spindle Stainless steel X10 CrNi S18-917440 Type 17683/13 AISI 303

5 Cone Steel

8 Packing gland Steel

9 Packing washer Aluminium

12 Bolts Stainless steel A2-70 A2-70 Type 308

13 O-ring Cloroprene (Neoprene)

14 Spring Steel

16 Spring washer Steel

17 Cap Aluminium

18 Gasket or cap Nylon

20 Gu ide piece Steel


22 Sealing ring PTFE (Teon)

23 Distance piece Steel24 O-ring Cloroprene (Neoprene)

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OFV-SS 20 - 25 ( 3 / 4 - 1")

No. Part Material DIN/EN ISO ASTM

1 Housing Stainless steel X5CrNi18-10

EN10088

AISI 304

2 Bonnet, Flange Stainless steel X5CrNi18-10

EN10088

AISI 304

3 Bonnet, Insert Stainless steel

4 Spindle Stainless steel X8CrNiS18-9DIN 17440

Type 17, 683/13 AISI 303

5 Cone Steel 9SMn28 Type 2 1213

8 Packing gland Stainless steel

9 Packing washer Non asbestos

12 Bolts Stainless steel A2-70 A2-70 Type 308


14 Spring Steel

16 Spring washer Steel Steel

17 Spindle seal cap Aluminium

18 Seal cap gasket Nylon

20 Guide piece Steel


22 Sealing ring PTFE (Teon)

23 Distance piece Steel


Material specifcation

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Connections

DIN

ANSI

Dimensions and weightsOFV 20 - 25

Specied weights are approximate values only.

20

25

3 /4

1

26.9

33.7

2.3

2.6

1.059

1.327

0.091

0.103

0 - 0.52

0 - 1.50

0 - 0.60

0 - 1.74

Welding DIN (EN 10220)

Size

mm

Size

in.

OD

mm

T

mm

OD

in.

T

in.

k v-angle

m3 /h

Cv-angle

USgal/min

OFV 20 (¾ in.)mm

in.

45

1.77

230

9.1

290

11.4

38

1.5

60

2.42.0 kg

OFV 25 (1 in.)mm

in.

45

1.77

230

9.1

290

11.4

38

1.5

60

2.42.0 kg

Valve size G C Cmin ∅D H Weight

OFV 20 - 25

20

25

3 /4

1

26.9

33.7

4.0

4.6

1.059

1.327

0.158

0.181

0 - 0.52

0 - 1.50

0 - 0.60

0 - 1.74

Welding ANSI (B 36.10 Schedule 80)

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Opening diferential pressure2-8 bar (29-116 psi):

How to order The table below is used to identiy the valverequired.

Please note that the type codes only serve to

identiy the valves, some o which may not ormpart o the standard product range.

For urther inormation please contact your localDanoss Sales Company.

Type codesExample or type codes

OFV 25 D 1 3 3 Valve type OFV Over Flow Valve

Nominal size in mm 20

25

DN 20

DN 25

Connections A

D

Welding branches: ANSI B 31.5 schedule 80

Welding branches: DIN 2448

Valve housing 1 Angle ow

Materials 3 Housing: P285 QH, Bonnet: P275 NL1

Other equipment 3 Cap, short spindle with Cloroprene (Neoprene) O-ring

Important!Where products need to be certied accordingto specic certication societies or where higherpressures are required, the relevant inormationshould be included at the time o order.

Ordering

Size Type Code No.

mm in

20 ¾ OFV 20 A 133 2412+185

20 ¾ OFV 20 D 133 2412+18320 ¾ OFV-SS 20 D ANG OVER FLOW VALVE 52BAR 148G3194

25 1 OFV 25 A 133 2412+186

25 1 OFV 25 D 133 2412+184

25 1 OFV-SS 25 D ANG OVER FLOW VALVE 52BAR 148G3195

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