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RULES FORCLASSIFICATION OF

DET NORSKE VERITAS

Veritasveien 1, N-1322 Høvik, Norway Tel.: +47 67 57 99 00 Fax: +47 67 57 99 11

SHIPS / HIGH SPEED, LIGHT CRAFT ANDNAVAL SURFACE CRAFT

NEWBUILDINGS

MACHINERY AND SYSTEMSMAIN CLASS

PART 4 CHAPTER 5

ROTATING MACHINERY,DRIVEN UNITSJANUARY 2003

CONTENTS PAGE

Sec. 1 Propellers.................................................................................................................................... 5Sec. 2 Water Jets ................................................................................................................................... 9Sec. 3 Thrusters................................................................................................................................... 13Sec. 4 Compressors ............................................................................................................................. 18



CHANGES IN THE RULES

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If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such personfor his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compen-sation shall never exceed USD 2 million.In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of DetNorske Veritas.

General.

The present edition of the rules includes additions and amendmentsdecided by the board in December 2002, and supersedes the January2001 edition of the same chapter.

The rule changes come into force on 1 July 2003.

This chapter is valid until superseded by a revised chapter. Supple-

ments will not be issued except for an updated list of minor amend-ments and corrections presented in Pt.0 Ch.1 Sec.3. Pt.0 Ch.1 isnormally revised in January and July each year.

Revised chapters will be forwarded to all subscribers to the rules.Buyers of reprints are advised to check the updated list of rule chap-ters printed Pt.0 Ch.1 Sec.1 to ensure that the chapter is current.

Main changes

Sec.1 Propellers

— The requiring for the delivery of the propeller with a NV certifi-cate has been moved from item C101 to new item A105.

— A new item A202, giving reference to Pt.4 Ch.9 Sec.1, has beenincluded.

— In Table A1 the requirement for operating instructions has beendeleted from the application for all propellers and moved to theapplication for controllable pitch propellers. A new note 3 hasalso been added to the operating instructions component.

— Item C101 has been moved to new a item A105. The remainingitems have been renumbered accordingly.

— In Table C1, the column concerning ultrasonic testing of steel,has been deleted.

• Sec.2 Water Jets

— New item A102, giving reference to Ch.2 has been added.— A103, requiring the delivery of the water jet with a NV certificate

has been introduced, the remaining items have been renumberedaccordingly.

— A new item A202, concerning torsional shock vibration calcula-tions, has been added and Table A1 amended accordingly.

— The previous items B202 and B203 have been deleted and the re-maining items have been renumbered accordingly.— A new item B207, concerning duct and connection details, has

been introduced.— Items C101 and C103 have been deleted and the remaining items

have been renumbered accordingly.— A new item C202, concerning non-destructive testing, has been

added.— Table C1 has been amended to include: the requirement for a

product certificate only when sub-contracted, the row/column,Impeller/Surface crack detection has been changed from NV toW, note 5 has been deleted and note 6 renumbered note 5.

— Items C302 and C303 have been deleted and the remaining itemshave been renumbered accordingly.

— A new item E203, concerning corrections in the steering controlsystem, has been added.

— Table E1, concerning monitoring of water jets, has been amend-ed to include: deletion of requirements for rows/columns: Hy-draulic oil supply tank level/Request for slow down andHydraulic oil pressure/Alarm with individual indication. Re-quirements have been added for rows/columns, Hydraulic oilsupply tank level/Alarm with individual indication and Hydrau-

lic oil pressure/Request for slow. In note 1 the requirement for jets above 1500 mm inlet diameter has been amended to1000 mm inlet diameter.

— Items I103 and I105 have been deleted and the remaining itemshave been renumbered accordingly.

• Sec.3 Thrusters

— Item A101 has been amended to include on board function test-ing for thrusters.

— DYNPOS has been added to the class notations in item A104.— Item B301 has been amended and Table B2 has been deleted.— G102 has been amended concerning the blade frequency for pro-

pulsion thrusters.

• Sec.4 Compressors

General:This section has been amended, in order to follow the structure of Pt.4of the machinery rules.

The main changes are:

— Documentation and certification requirements have been trans-ferred to tables.

— A requirement for design approval for all compressors with shaftpower (P) > 200 kW, has been added.

— Text, limiting design verification for reciprocating compressorshas been deleted.

— The requirement for crankshaft and rotors has been changed fromNV to W.

— The requirement for cylinders has been changed from “TR or Wif specially required” to TR.

— The requirement for housing and casing has been changed from

“TR or W if specially required” to TR.— “Status“ for documentation based on model for “diesel engine”

has been changed.— Requirement for high-pressure alarm has been added.— Requirement for torsional vibration calculations has been added.— Requirement for inspection of vibration has been added.

Corrections and Clarifications

In addition to the above stated rule requirements, a number of detect-ed errors, corrections and clarifications have been made in the exist-ing rule text.



Rules for Ships / High Speed, Light Craft and Naval Surface Craft, January 2003 Pt.4 Ch.5 Contents –

DET NORSKE VERITAS

CONTENTS

SEC. 1 PROPELLERS ..................................................... 5

A. General ...................................................................................5A 100 Application........................................................................5

A 200 Documentation..................................................................5

B. Design .....................................................................................5B 100 General ..............................................................................5B 200 Criteria for propeller blade dimensions ............................6B 300 Pitch control mechanism...................................................6B 400 Fitting of propeller blades to the hub................................6

C. Inspection and Testing..........................................................7C 100 General ..............................................................................7C 200 Inspection and testing of parts ..........................................7C 300 Certification of ancillaries.................................................7

D. Workshop Testing .................................................................7D 100 General ..............................................................................7

E. Control, Alarm, Safety Functions and Indication..............7E 100 General ..............................................................................7

F. Arrangement..........................................................................8F 100 General ..............................................................................8F 200 Arrangement of propeller..................................................8F 300 Hydraulic system for pitch control....................................8

G. Vibrations ..............................................................................8G 100 General ..............................................................................8

H. Installation Inspection ..........................................................8H 100 General ..............................................................................8H 200 Fitting of propeller............................................................8H 300 Pitch marking ....................................................................8H 400 Hydraulic piping ...............................................................8

I. Shipboard Testing .................................................................8I 100 Sea trial .............................................................................8

SEC. 2 WATER JETS ...................................................... 9

A. General ...................................................................................9A 100 Application........................................................................9A 200 Documentation..................................................................9A 300 Definitions.........................................................................9

B. Design .....................................................................................9B 100 General ..............................................................................9B 200 Design of components.....................................................10

C. Inspection and Testing........................................................10C 100 General ............................................................................10C 200 Certification of parts .......................................................10C 300 Testing and inspection of parts .......................................10C 400 Assembling .....................................................................11

D. Workshop Testing ...............................................................11D 100 General ............................................................................11

E. Control, Alarm, Safety Functions and Indications..........11E 100 General ............................................................................11E 200 Monitoring and bridge control ........................................11

F. Arrangement........................................................................11F 100 General ............................................................................11

G. Vibration ..............................................................................11G 100 General ............................................................................11

H. Installation Survey ..............................................................11H 100 Surveys............................................................................11

I. Shipboard Testing ...............................................................12I 100 General ............................................................................12

SEC. 3 THRUSTERS ..................................................... 13

A. General ................................................................................ 13A 100 Application......................................................................13

A 200 Documentation................................................................13

B. Design.................................................................................. 13B 100 General............................................................................13B 200 Shafting ...........................................................................13B 300 Gear transmissions..........................................................14B 400 Azimuth steering gear.....................................................14B 500 Steering column and pod stay and underwater housing..14B 600 Propeller..........................................................................14B 700 Bearings ..........................................................................14B 800 Lubrication system..........................................................14

C. Inspection and Testing....................................................... 15C 100 General............................................................................15C 200 Certification of parts .......................................................15C 300 Material and NDT testing ...............................................15

C 400 Assembling .....................................................................15

D. Workshop Testing.............................................................. 15D 100 Testing of assembled unit ...............................................15

E. Control, Alarm, Safety Functions and Indication........... 15E 100 General............................................................................15E 200 Bridge control .................................................................16

F. Arrangement....................................................................... 16F 100 General............................................................................16F 200 Propulsion thrusters ........................................................16

G. Vibration ............................................................................. 17G 100 Torsional vibration..........................................................17G 200 Torsional impact vibration..............................................17

H. Installation Inspection ....................................................... 17H 100 Installation onboard ........................................................17

I. Shipboard testing ............................................................... 17I 100 Sea trial ...........................................................................17

SEC. 4 COMPRESSORS............................................... 18

A. General ................................................................................ 18A 100 Application......................................................................18A 200 Documentation................................................................18

B. Design.................................................................................. 18B 100 General............................................................................18B 200 Crankshafts .....................................................................18B 300 Rotors..............................................................................19

B 400 Rotor casing ....................................................................19

C. Inspection and Testing....................................................... 20C 100 General............................................................................20C 200 Certification, testing and inspection of parts..................20

D. Workshop testing ............................................................... 20D 100 General............................................................................20

E. Control and Monitoring .................................................... 20E 100 General............................................................................20

F. Arrangement Onboard ...................................................... 20F 100 General............................................................................20

G. Vibrations ........................................................................... 20

G 100 Torsional vibration..........................................................20

H. Installation Inspection ....................................................... 20H 100 General............................................................................20H 200 Vibration .........................................................................20



Rules for Ships / High Speed, Light Craft and Naval Surface Craft, January 2003Pt.4 Ch.5 Contents –

DET NORSKE VERITAS



Rules for Ships / High Speed, Light Craft and Naval Surface Craft, January 2003 Pt.4 Ch.5 Sec.1 –

DET NORSKE VERITAS

SECTION 1PROPELLERS

A. General

A 100 Application101 The rules in this section apply to propellers intended forpropulsion, steering and manoeuvring, subject to certification.See Ch.2 Sec.1 A200 (for auxiliary thrusters, see also Sec.3A101).

102 Ch.2 describes all general requirements for rotating ma-chinery and forms the basis for all sections in Ch.3, Ch.4 andCh.5.

103 The following items are recognised as parts of the pro-peller and are subject to approval:

— propeller blades— blade bolts (if any)— propeller hub

— pitch control mechanism (if any).

For fitting of the propeller to the shaft, see Ch.4 Sec.1.

104 See Pt.5 Ch.1 of the Rules for Classification of Shipsconcerning propellers for ships with ice strengthening.

105 The propeller shall be delivered with a NV certificate.

A 200 Documentation

201 Plans and particular shall be submitted as applicable ac-cording to Table A1.

The plans are to show clearly all scantling details and arrange-ments, as well as material specifications and heat treatment.For propeller blades, hubs or blade bolts made of steel, accept-ance criteria (or reference to such) for ultrasonic testing shallbe given. Design parameters, such as engine power, propellerrotational speed, maximum vessel speed and ice class shall begiven, see also Ch.4 Sec.3 A101. The manufacturing toleranceclass (ISO 484) shall be specified on the propeller drawings.

202 For instrumentation and automation, including compu-ter based control and monitoring, see Ch.9 Sec.1.

B. Design

B 100 General

101 Materials for propellers shall comply with the require-ments in Pt.2 Ch.1 and Pt.2 Ch.2.

For other materials, particulars of mechanical properties andchemical compositions shall be submitted to the Society. Fa-tigue properties different from the ones given in Table B1 maybe accepted, provided sufficient documentation is presented.

Table A1 Documentation

Application Component For approval (A)For information (I)

Reference to designrequirements

Mono-block fixed pitch propellers Propellers cast in one piece A See Classification Note 41.5

Built-up fixed pitch propellers andcontrollable pitch propellers

Blades A See Classification Note 41.5

Blade bolts A See B400

Hub A

Controllable pitch propellers

Pitch control mechanism A See B300

Schematic hydraulic diagram 1) ASee F300 and Ch.6. Sec.5 H100 ofthe Rules for Classification of Ships

Operating instructions 3) I See E102

All propellers

Propeller fitting to shaft 2) A See Ch.4 Sec.1

Installation instructions I

Diagrams for control, alarm, safetyfunctions, and indications

A See E100

Free wheeling propeller Arrangement of free wheeling propeller I See F200

1) Including permissible operating servo pressures, specification of oil filter, and specification of minimum degree of oil cleanliness.

2) Data and calculations.

3) Only in case pitch adjustment is used as load control of prime mover



Rules for Ships / High Speed, Light Craft and Naval Surface Craft, January 2003Pt.4 Ch.5 Sec.1 –

DET NORSKE VERITAS

Guidance note:

Fatigue properties U1 (fatigue strength amplitude) and U2 (rela-tive reduction of fatigue strength with increasing mean stress)may be documented in accordance with the following recom-

mended testing procedure:- Material specimen without notches is to be tested in “sea wa-

ter”. Surface roughness is to be as for finished propellers. Ma-terial properties and chemical composition are to berepresentative for the minimum material requirements.

- Bending of flat bars is preferred, but testing with rotatingbending is also acceptable.

- Thickness of specimen is to be at least 25 mm.- Tests are to be performed both with and without weld repairs.- Number of cycles to be at least 107 at a bending frequency not

higher than 5 Hz.- Minimum number of tests: 2 x 20 (with and without welding

repairs). Specimen is to be taken from at least two separatematerial charges.

- Testing is to be performed according to the “Staircase meth-od”.

U1 to be taken as average fatigue amplitude (N/mm2) corre-sponding to 107 cycles at zero mean stress (stress ratio, R = -1),divided by a factor of 2, provided the standard deviation does notexceed 15% of the average value.

In case U2 is to be documented, additional testing should be car-ried out as above, with a stress ratio, R = 0.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

102 The requirements given in 200, 300, and 400 apply to allpropellers of conventional design and arrangement, unless oth-erwise explicitly stated. For propellers not recognised as con-ventional by the Society (e.g. surface piercing propellers,cycloidal propellers etc.), the approval will be based on specialconsideration.

103 Scantlings less than required in B may be accepted if sufficient strength is documented by other means, for examplereliable measurements and or detailed calculations.

104 The combination of materials shall be such as to mini-mise galvanic corrosion.

105 The surface of the hub, conical bores, fillets and bladesshall be smoothly finished.

B 200 Criteria for propeller blade dimensions

201 The load conditions to be considered are:

a) High cycle dynamic stresses (> 108 cycles) due to rotation-al propeller load variation in normal, ahead operation.

b) Low cycle dynamic stresses (< 106 cycles) due to propellerload variations in a seaway, manoeuvres, starting and stop-ping, reversing, repetitive ice shock loads etc. are also tobe considered when dynamic stresses are not dominatedby high cycle load variations, e.g. for propellers for which

turning direction may be reversed and propellers runningin undisturbed axial inflow.

For detailed description of calculation methods, see Classifica-

tion Note 41.5.

B 300 Pitch control mechanism

301 The pitch control mechanism shall be able to withstandthe static forces transmitted when two of the blades are pre-vented from pitching (servo force acting on two blades) with asafety factor of at least 1.0 against yielding.

302 Maximum servo force (servo pressure corresponding toset point to safety valve) is to be applied in the calculations.Guide pin is assumed to be located in the most critical position.

303 Unless the propeller is intended for auxiliary purposesonly, fatigue shall be considered taking the following into ac-count:

— start and stop of propeller— manoeuvring and position keeping as applicable— change of pitch setting in normal, ahead condition— rotational load variation of propeller in normal, ahead op-

eration (for propellers intended for main propulsion only).

304 The design shall be such that reasonably low stress con-centrations are ensured.

305 The degree of filtration of hydraulic oil must correspondwith maximum allowable particle size in the system.

306 For general design requirements for piping and ancillaryequipment such as pipes, pumps, filters, coolers etc., see Ch.6of the Rules for Classification of Ships and Ch.7 as found ap-

plicable.

B 400 Fitting of propeller blades to the hub

401 The pre-tensioning of the blade bolts shall ensure fric-tion forces sufficient to prevent sliding of the propeller flangewith a safety factor of at least 1.0 when the propeller is exposedto forces as described in 300. If shear pins are fitted, the sumof friction and shear forces is to be considered. Pretensionstress in the minimum section of the blade bolts is not to ex-ceed 70% of the bolt-material yield strength or 56% of the ten-sile strength, whichever is the least.

402 The blade bolt pre-stress shall be high enough to ensurethat a certain minimum surface pressure between mating sur-faces is obtained in all permissible operating conditions. How-

ever, the blade bolt stress shall not exceed yield strength of thebolt material.

403 High cycle dynamic stress amplitudes in the minimumthread section of the blade bolts for propellers intended formain propulsion shall fulfil the following criterion:

Table B1 Material properties

Material Material constant U 1 (N/mm2)

Material constant U 2 (-)

Minimum yield strengthσ y (N/mm2)

Minimum tensile strengthσ B (N/mm2)

Mn-Brass (CU1) 55 0.15 175 440

Ni-Mn-Brass (CU2) 55 0.15 175 440

Ni-Al-Bronze (CU3) 80 0.18 245 590

Mn-Al-Bronze (CU4) 75 0.18 275 630

Martensitic/ferritic stainlesssteel (13-1)

60 0.20 440 590

Martensitic/ferritic/ austeniticstainless steel (16-5)

70 0.20 540 760

Martensitic/ferritic stainlesssteel (13-4-6)

65 0.20 550 750

Austenitic stainless steel (18-8) 55 0.23 180 440

Forged steel and other materials will be especially considered.




DET NORSKE VERITAS

S = safety factor, not to be less than 1.5

σ A = dynamic stress amplitude

U = allowable nominal stress amplitude in the threaded ar-

ea, normally 35 N/mm2 for machined threads and 60N/mm2 for rolled threads.

404 Other means of propeller blade fitting mechanisms willbe especially considered.

C. Inspection and Testing

C 100 General

101 Blade bolt pre-tensioning shall be carried out in the pres-ence of a surveyor.

102 All tests and inspections in 104 to 107 shall be carriedout in the presence of a surveyor.

103 For controllable pitch propellers, all connections shallbe properly sealed.

104 For controllable pitch propellers intended for propul-sion, the following pitch settings shall, as a minimum, be prop-erly marked on the hub and blade flange:

— pitch at 70% radius is zero

— maximum pitch ahead (pitch limited by mechanical pitchstopper)

— maximum pitch astern (pitch limited by mechanical pitchstopper).

The correctness of pitch marks and the mechanical feedback of pitch setting shall be verified.

105 The function of the pitch stoppers shall be demonstrated.If pitch stoppers are located outside of the hub, it shall be ver-

ified that maximum deflection in each direction is less than in-side the propeller hub.

106 After assembly, the complete servo system shall beproperly flushed.

107 The complete controllable pitch propeller system shallbe function tested and pressure tested as follows:

— hydraulic pitch control to 1.5 times design pressure

— tightness of propeller subject to 1 bar.

C 200 Inspection and testing of parts

201 Regarding certification schemes, short terms, manufac-turing survey arrangement, and important conditions, see Ch.2

Sec.2.202 NV certificate is required for separate blades.

203 Further certificates are required in accordance with Ta-ble C1.

204 With respect to non-destructive testing for detection of surface defects, the following acceptance criteria apply:

— for propeller blades and hubs, the criteria given in Pt.2Ch.2 Sec.7 and Sec.10 apply

— no indications of defects are accepted in highly stressed ar-eas of components in the pitching mechanism.

C 300 Certification of ancillaries

301 Pumps, electric motors, coolers, piping, filters, valves,etc. that are delivered as integral parts of the hydraulic opera-tion and cooling systems, shall be checked as found relevant bythe propeller manufacturer’s quality system.

D. Workshop Testing

D 100 General

101 The complete propeller shall be statically balanced in

accordance with ISO 484 (or equivalent) in presence of a sur-veyor. Dynamic balancing may be required for propulsion pro-pellers with tip speed exceeding 60 m/s. For built-uppropellers, the required static balancing may be replaced by anindividual control of blade weight and gravity centre position.The manufacturer is to demonstrate that the assembled propel-

ler will be within the specified limits.

E. Control, Alarm, Safety Functions and Indica-tion

E 100 General

101 For controllable pitch propellers, governing and moni-toring systems shall comply with the requirements of Ch.9.

102 Pitch adjustment shall not be used as load control systemof prime mover, unless the propeller system is especially de-

signed for this purpose.

103 A local control for pitch shall be installed.

104 Instrumentation and alarms shall be provided accordingto Table E1, if not otherwise approved.

SU

σ A

-------=

Table C1 Category C certificates

Component Material certificate (chemicalcomposition and mechanical

properties)

Magnetic particleinspection or dye

penetrant

Visual anddimensionalinspection

Propellers cast in one piece NV NV NV 1)

Separate blades NV NV NV 1)

Separate hubs NV or W 2) W 3) NV or W 2)

Blade bolts NV or W 2) W W

Crank disc, push pull rod, actuator cylinder and cross head.Other parts of pitching mechanism when found necessary

W W 4) W

1) The surveyor is to verify that the propeller blades are manufactured according to the specified tolerance class.

2) NV if propulsion.

3) Only required in A and C zones (see Pt.2 Ch.2 Sec.7 and Sec.10).

4) Only required in highly stressed areas, such as blade bolts, crank disk fillet, threads of push-pull rods, etc.




DET NORSKE VERITAS

SECTION 2WATER JETS

A. General

A 100 Application101 The rules in Sec.2 apply to axial water jets intended formain propulsion and steering for all types of vessel.


103 The waterjet unit shall be delivered with a NV certifi-cate.

104 Water jet units with main steering function are also re-garded as steering gear for the vessel.

105 Water jet units for auxiliary steering purposes (i.e. notfor propulsion) are only subject to classification after especialconsideration.

A 200 Documentation

201 Plans, particulars and calculations shall be submitted ac-cording to Table A1.

202 Torsional shock vibration calculations may be requiredupon request.

A 300 Definitions

301 The rules in Sec.2 use the nomenclature as defined be-low.

Ducting

Water streaming along the vessel bottom flows into a duct,

leading the water to the water jet. The duct forms an integralpart of the vessel hull. It is normally manufactured at the yard.

Impeller

The rotating hub with blades. The impeller is connected to theshaft. The impeller is usually cast in one piece. Alternatively,the blades are welded onto the hub.

Stator housing

By leading the water flow through a row of stationary vanesdownstream of the impeller, the swirl added to the water by theimpeller is reduced, and the longitudinal speed of the waterflow is increased. The vanes are usually formed as an integralpart of the water jet housing.

Impeller housing

The water jet casing surrounding the impeller.

Steering nozzle

The water flow is lead through a passageway that can be tiltedhorizontally in relation to the vessel's longitudinal axis, there-by changing the direction of the water jet flow. This creates aturning moment used for steering the vessel.

Reversing bucket

For reversing purposes, the water jet incorporates componentsthat can force its entry into the water flow thereby turning thewater jet discharge to be thrown somewhat forwards. This cre-ates a reversing force that acts on the vessel. The flow is eitherthrown forwards in an angle directed below the vessel, or toboth of the sides of the water jet. The components used for thispurpose is denoted a bucket.

Hydraulic actuators

Used for either steering or reversing as the driving force thatimpose the reversing bucket or acts on the steering nozzle tocreate a change in the water flow direction.

B. Design

B 100 General

101 For general design principles for machinery, see Ch.2Sec.3.

102 The water jet unit shall be capable of withstanding theloads imposed by all permissible operating modes, includingthe condition when the inlet of the suction is blocked.

103 The stresses in water jet components shall be consideredbased on loads due to the worst permissible operating condi-

Table A1 Documentation requirements

Water jet arrangement I

Cross section drawing of unit I

Structural drawings (housing, mounting flanges etc.) andconnections to the water inlet including NDT specification

I

Impeller including NDT specification I

Shafting parts to be documented according to Ch.4 Sec.1 A

Stator housing (with guide vanes) I

Steering arrangement A

Reversing arrangement A

Hydraulic actuators for steering and reversing, see B205 andB206

A

Bearing arrangement with particulars A

Seal box * A

Stern flange with bolting A

Water inlet ducting with respect to hydrodynamic design(see also Rules for Classification of HS, LC and NSC Pt.3Ch.5 Sec.1 concerning strength)

I

All bolt connections carrying thrust or torque, specificationof bolt material and tightening procedure (bolt pre-stress)

A

Control system set points and time delays, see Table E1 A

Water jet pump characteristic, with operation limits includ-ing cavitation limits, see limit as for Table E1

I

Impeller thrust, vessel thrust and maximum reversing forcesat crash stop

I

Normal operating parameters that define the permissible op-erating conditions, such as thrust, impeller r.p.m., vesselspeed, impeller r.p.m. versus vessel speed, see limit as forTable E1

I

Calculated lifetime of roller bearings A

Impeller blade strength calculations UR(I)

Strength calculation of the stern flange connection, B207 UR(A)

Strength calculation of the steering and reversing mecha-nism

UR(A)

Housing strength calculation, see B200 UR(I)

*) Type approval is required for oil lubricated standard design.

AIUR(A)UR(I)

= For approval= For information= Upon request; for approval= Upon request; for information




DET NORSKE VERITAS

tions, taking into account:

a) Hydrodynamic loads, including varying hydrodynamicloads due to water flow disturbances introduced e.g. by theducting or hull.

b) Vessel accelerations versus water jet r.p.m.

c) Air suction as assumed in G103, transient cavitation,

waves etc.Guidance note:

At full design speed on a straight course and with the vessel des-ignated trim, giving the designed water head above the water in-take, harmful impeller cavitation will normally not occur.Harmful cavitation in this context is that cavitation which will re-duce shafting system and waterjet component lifetime by intro-ducing vibration or impeller erosion.

However, the waterjet may be exposed to operating conditionsoutside the intended design. Such situations may occur for in-stance due to increased vessel weight, increased hull resistance,vessel operating at deeper waters etc. In situations where opera-tion exceeds the design premises, harmful impeller cavitationmay occur as a consequence of abnormal waterjet flow condi-tions. This phenomenon has showed to be of increasing impor-

tance with increasing waterjet size.To combat this, the waterjet should be designed with reasonablemargin for cavitation, and care should be taken to avoid vesseloverweight due to e.g. reasons mentioned in the above. The big-ger the waterjets are the more important this advice become.


104 The water jet units shall be provided with inspection fa-cilities for inspection of the shaft and impeller.

B 200 Design of components

201 The dimensions of the shafts and the shafting compo-nents, including bearings, shall comply with the requirementsin Ch.4 Sec.1.

202 The impeller housing and stator housing shall be de-signed against fatigue considering impeller pulses and otherflow pulses.

203 Steering and reversing mechanisms shall be designed in

consideration of the worst permissible operational conditions.

204 The materials used in the hydraulic actuators shall besuitable for the expected environmental conditions.

205 Hydraulic actuators for steering shall comply with therequirements given in the Rules for Classification of HS, LCand NSC Pt.3 Ch.5 Sec.2, as applicable.

206 Hydraulic actuators for reversing shall comply with therequirements given in the Rules for Classification of ShipsCh.6 Sec.5 H. However, if the hydraulic system for the revers-ing actuators is the same as for the steering system, the designand test pressure for the reversing actuators shall be the sameas for the steering actuators. Higher nominal stresses may beaccepted for the reversing actuator.

207 The critical details of the duct and connections to thehull structure shall be designed against extreme loads occur-ring during crash stop and fatigue considerations related to re-versing, steering and impeller pulses.


C 100 General

101 The certification principles and the principles of manu-facturing survey arrangements (MSA) are described in Ch.2Sec.2.

Regarding material and testing specifications, see Ch.2 Sec.3.

102 Welding procedures shall be qualified according to arecognised standard or Pt.2.

C 200 Certification of parts

201 Water jet parts, semi-products or materials shall be test-ed and certified according to Table C1 and 300 if not otherwiseagreed in a MSA, see Ch.2 Sec.2 C100.

202 Non-destructive testing (NDT) for parts submitted forapproval shall follow the approved specification. NDT forparts submitted for information shall be as per manufacturer'sspecification.

C 300 Testing and inspection of parts301 The inspection and testing described in the following arecomplementary to 200.

302 The visual inspections by the Society shall include ran-dom dimensional check of vital areas such as flange transition

radius, bolt holes etc., in addition to the main overall dimen-sions.

303 Particulars concerning ducting inspections are stated inH105.

304 The impeller shall be statically balanced.

Table C1 Requirements for certification of parts

Productcertificate,only when

sub-contracted

Documentation by certificates

Materialcertificate

Ultra-sonic or X-ray testing

Surface crackdetection 3)

Pressuretesting

Dimension-al inspec-

tion

Visualinspection

Other

Impeller NV W W W NV W 1)

Stator housing W W4) W W NV

Impeller housing W W4 W W NV

Shafting According to Ch.4 Sec.1 C

Hydraulic actuators for re-versing and steering 6)

NV NV or W2)

U-S or surface crack detection(W)4)

NV or W2)

Other steering and reversingcomponents

W (W)4) W

Bolts TR

Ducting when delivered in-tegral with the water jet

W W W NV

1) See 306.

2) NV for steering hydraulic actuators, (See also Rules for Classification of HS, LC and NSC Pt.3 Ch.5 Sec.2 B200), W for reversing hydraulic actuators.

3) Crack detection in final condition.

4) NDT of welds upon request.

5) Hydraulic actuator include cylinder, rod, cylinder end eye and rod end eye.




DET NORSKE VERITAS

Guidance note:

VDI standard no. 2060 Quality class 6.3 or ISO 1940/1 BalanceGuide G6.3 may be used as reference.


C 400 Assembling

401 For fitting of the impeller to the shaft, see Ch.4 Sec.1B300 to B700.

D. Workshop Testing

D 100 General

101 Not applicable.

E. Control, Alarm, Safety Functionsand Indications

E 100 General

101 The systems shall comply with the requirements in Ch.9.

E 200 Monitoring and bridge control

201 The monitoring of water jets (for propulsion) shall be inaccordance with Table E1 in regard to: indications, alarms andrequests for slowdown.

202 Monitoring and bridge control shall also be in compli-ance with Ch.9 and Rules for Classification of HS, LC andNSC Pt.3 Ch.5 Sec.2 D500 to D600.

203 Frequent corrections in the steering control system,when the vessel is on straight course, shall be avoided if prac-ticable.

Guidance note:The actual corrections should be read preferably by monitoringthe control signal. Alternatively, direct measurements on me-chanical feedback device from the water jet can be used.


F. Arrangement

F 100 General

101 The installation and arrangement of the water jet unitwith auxiliaries shall comply with the manufacturers specifica-tion.

102 Ship external parts of the water jet shall be protected by

guard rails or other suitable means, see Rules for Classificationof HS, LC and NSC Pt.3 Ch.5 Sec.1 C200.

G. Vibration

G 100 General

101 For requirements concerning whirling calculations andshaft alignment specification, see Ch.4 Sec.1.

102 For requirements concerning torsional vibration calcula-tions for diesel driven water jets, see Ch.3 Sec.1 G. For turbinedriven water jets, see Ch.3 Sec.2 G.

103 Calculations shall evaluate the torque variations deriv-ing from water jet load shedding from full load down to 20%and back to full load again due to of aeration of water jet. SeeCh.3 Sec.1 for diesel engines and Ch.3 Sec.2 D303 for gas tur-bines.

H. Installation Survey

H 100 Surveys

101 The fastening of the water jet to the hull and the structur-al strengthening around the water jet unit with ducting shall becarried out in agreement with the approved drawings.

102 Impeller clearances shall be checked after installationand shaft alignment and shall be in accordance with the manu-facturers specification.

103 Normal procedures for shafting apply, see Ch.4 Sec.1 H.

104 Thrust bearing axial clearances after installation shall beverified to be in accordance with the manufacturer specifica-tion, unless verified during assembly of the water jet.

105 The ducting shall be manufactured in accordance withdrawings and specifications from the water jet designer. Thesurfaces shall be smooth and free from sharp edges or bucklingthat could give raise to turbulence in the water flow and there-by adversely affect water jet operating conditions.

Guidance note:

Great care should be taken in assuring that the ducting dimen-sions agree with the water jet designer’s drawings. The ductingdesigner should be consulted for use of possible dimensionalchecking equipment, such as templates especially made for thatpurpose.


106 All piping systems shall be properly flushed, in accord-ance with the manufacturers specification. This shall be docu-mented by a work certificate.

107 Pressure testing of piping shall be done according toCh.6 of the Rules for Classification of Ships.

I. Shipboard Testing

I 100 General

101 For general requirements related to the testing of controland monitoring, see Ch.9.

Table E1 Monitoring of water jets

Failure

Required monitoring

Indicationon bridge

Alarm withindividualindication

Request forslowdown

Lubrication oiltank level(if provided)

Low X

Lubrication oilpressure (if forcedlubrication)

Low X

Hydraulic oilsupply tank level

Low X

Hydraulic oilpressure

Low X

Loss of steeringand/or reversingsignal

X X

Maximum permis-sible acceleration

exceeded (1)

High X

Impeller r.p.m.versus vesselspeed ratio (1)

High X X

(1) This requirement is only valid for waterjets above 1000 mm inlet diame-ter. However, it is advised for water jets below 1000 mm inlet diameter aswell.




DET NORSKE VERITAS

102 Final acceptance of the control system is dependentupon satisfactory results of the harbour testing and the final seatrial, as specified in items 103, 104 and 105.

103 Attention shall be paid to combinations of operationalfunctions. Testing of all combinations of functions shall becarried out.

104 Indication and alarm (if applicable) of operation outside

the specified operation limits shall be checked. This applies toacceleration as well as impeller r.p.m. versus vessel speed.

105 The water jet r.p.m. versus vessel speed shall be notedand plotted against the manufacturers operational curves. Thesurveyor shall verify the correct reading of values, and the re-sults shall be submitted to the approval centre after completionof test.




DET NORSKE VERITAS

SECTION 3THRUSTERS

A. General

A 100 Application101 The rules apply to thruster plants intended for propul-sion, propulsion and steering, dynamic positioning and, if above 300 kW, for auxiliary duty. However, all thrusters shallbe subject to function testing onboard, as covered by I. Thetunnel and other parts that are welded to the hull and form thebarrier against the ingress of sea water, shall always be subjectto approval, also for auxiliary units less than 300 kW.


103 The complete thruster shall be delivered with a DNVcertificate.

104 Definitions

A thruster is a unit equipped with a propeller or impeller in or-der to produce thrust. A thruster unit may be a conventionalunit with a lower gear, lower and upper gear or with the primemover directly attached to the propeller shaft. A unit is consid-ered as the complete unit from the propeller with nozzle to theinput shaft at the upper gear or slip ring unit (if applicable).

A propulsion thruster is a thruster that is mainly assigned topropulsion of the vessel. A propulsion thruster may also pro-vide steering function.

A dynamic positioning thruster is a thruster that is a part of adynamic positioning system on board a vessel with the classnotations: DYNPOS-AUTS, DYNPOS-AUT, DYNPOS-

AUTR and DYNPOS-AUTRO.An auxiliary thruster is a thruster for all other purposes thanpropulsion and dynamic positioning.

105 For HS, LC and NSC the following rules also apply:

— machinery in general: HSC Code 9.1.1 to 9.1.14, HSCCode 9.7 and 9.8 (passenger craft), and HSC code 9.9 (car-go craft)

— propulsion and lift devices: HSC Code 9.6.1 to 9.6.5.

106 For ice class notations, see Pt.5 Ch.1 of the Rules forClassification of Ships.

A 200 Documentation

201 Basic operation and load information to be submitted

For all thrusters except tunnel thrusters:

— information about any operational (design) limitationswhich may apply to the thruster unit (such as limitations inrotation of azimuth units at high vessel speed, maximumvessel speed for lowering and hoisting of retractable unitsetc.)

— description of crash stop procedure (thruster operation) in-cluding function of load control system during the mostextreme allowable manoeuvre

— maximum forces acting on the thruster unit under the mostextreme allowable manoeuvre.

For all thrusters:— starting procedure for electrical motors for propeller drive

including documentation of maximum start-up torque(KAP factor see. Classification Note 41.2). This documen-tation requirement does not apply to thrusters which obtain

the required scuffing safety factor (see Table B2) with apeak torque factor KAP of 1.5 or higher

— functional description of load control system and monitor-ing system including the power supply for each system.

202 Plans and particulars to be submitted

— thruster arrangement— assembly (sectional drawings)— structural drawings (gear housing, etc.) and connections to

the tunnel or nozzle— steering column— steering (azimuth) gear assembly— gears inclusive azimuth gear (as required in Ch.4 Sec.2)— shafts, couplings (as required in Ch.4 Sec.1)— propeller (as required in Sec.1)— bearing arrangement

— sealing boxes exposed to sea— mounting to the hull— sealing arrangement for flexibly mounted thrusters— propeller nozzle (see Pt.3 Ch.3 Sec.2 of the Rules for Clas-

sification of Ships).

Diagram and data

— load data for azimuth gear (see B400)— piping diagrams for cooling, lubrication and hydraulic

systems (pitch, azimuth, etc.)— alarm set points and delay times— indicator positions.

Calculations

— torsional vibration calculation, see G— torsional impact vibrations for electric motor drive with

direct start (or star-delta start)— calculated life times of rolling bearings.

203 The following calculations and procedures are to besubmitted upon request

— torsional impact vibrations (other than drives with director star-delta start)

— pendulum vibrations— component strength (i.e. for steering column etc.)— assembling and adjustment procedures regarding gear

mesh contact for drive gears.

B. Design

B 100 General

101 The thruster shall be capable of withstanding the loadsimposed by all allowable operating conditions.

102 In-dock inspection of thruster gears shall be made possi-ble either through proper inspection openings, or by othermeans (e.g. fibre optical instruments) without extensive dis-mantling.

103 For general design requirements for piping and ancillaryequipment such as pipes, pumps, filters, coolers etc., see Ch.6of the Rules for Classification of Ships and Ch.7 as found ap-plicable.

B 200 Shafting

201 The dimensions of the shafts and the shafting compo-nents shall be in accordance with Ch.4 Sec.1.




DET NORSKE VERITAS

B 300 Gear transmissions

301 Gear transmissions shall be in accordance with the re-quirements in Ch.4 Sec.2 as far as applicable. In general thelifetime criteria given in Table B1 may be used for dimension-ing the gears in the propeller drive line.

The safety factors SF against tooth fracture, SH against pitting,spalling and case crushing and SS against scuffing shall be atleast as specified in Table B1 in Ch.4 Sec.2. The safety factorfor gears in thrusters for dynamic positioning is to be as forpropulsion gears.

B 400 Azimuth steering gear

401 Azimuth thrusters designed for reversing the thrust byturning the unit, shall be able to do so at a speed of minimum2 r.p.m.

402 Azimuth steering gears are to have a margin against self-locking, unless overload protection is provided. The total drivetrain efficiency (excluding the driving motor) shall not be lessthan 0.65.

403 Azimuth steering gears for dynamically positioningthrusters shall be designed for continuos running.

404 Steering gear transmissions shall be in accordance withthe requirements in Ch.4 Sec.2 as far as applicable. The steer-ing gear transmission shall be designed considering the rele-vant loads (see A201).

Guidance note:

Typically the following load cases shall be considered:

- Maximum torque corresponding to relief valve setting pres-sure (steering gear design pressure pD) for hydraulic opera-tion, respectively max torque for electric motor operation.This can normally be considered as a static or low cycle fa-tigue case (1000 cycles).

- Loads occurring at larger manoeuvre (course changing). Thisload normally corresponds to the maximum working pressurepW and will typically occur in the range from 5000 to 100 000times during the vessels lifetime.

- Loads occurring due to course keeping corrections (auto pilotload). This is normally a high cycle load case and more than5·107 course corrections (load cycles) may be expected duringthe vessels lifetime.


405 For electric steering gear actuators the torque capacityshall be minimum 1.25 times the torque occurring during thesteering gear test (see the Rules for Classification of Ships,Pt.3 Ch.3 Sec.2 J102). This is considered equivalent to the re-quirement for hydraulic steering gear (see the Rules for Clas-sification of Ships, Pt.3 Ch.3 Sec.2 J306).

The safety factors SF against tooth fracture, SH against pitting,spalling and case crushing and SS against scuffing shall be atleast as specified in Table B3.

B 500 Steering column and pod stay and underwaterhousing

501 The maximum local stress in the steering column andpod stay shall not exceed 0.8 times the yield strength of the ma-terial under the most extreme allowable (possible) manoeuvre(see A201). FEM calculation may be required when analyticalmethods cannot give satisfactory accuracy (relevant stress con-centration factors are sometimes difficult to find in literature).The maximum nominal stress shall not exceed 50% of theyield strength.

502 The steering column and pod stay shall be designed towithstand the fatigue loads arising from thrust variations andother hydrodynamic loads, accelerations etc. This applies toparent material as well as to any welds.

503 The thruster structure as underwater housings, steeringcolumn and pod stay etc. shall have a stiffness sufficient toavoid harmful deformations which may cause damage to inter-nal shafting, sealing, bearings, gear mesh etc. when subjectedto the loads defined in A201.

504 The sealing around the steering column and pod stay, atthe hull penetration, shall normally be arranged so that any

leakage can be detected before water can gain access to watersensitive parts, such as slewing bearing and gears etc. Existingdesigns with a proven service record may be accepted with oth-er sealing arrangements.

B 600 Propeller

601 The propeller and propeller components shall meet therelevant dimensional requirements in Sec.1.

602 Special attention shall be paid to the sealing for propellerblades, in order to prevent ingress of water into the oil system.The sealing shall be designed to ensure that expected lifetimeis safely beyond the specified service intervals.

603 Controllable pitch mechanism on thrusters that are usedin a dynamic positioning system, shall be designed for contin-

uos operation.

B 700 Bearings

701 Fluid film bearings shall be designed in accordance withthe requirements in with Ch.4 Sec.2 B701.

702 Ball and roller bearings shall have a minimum L10a (ISO281) as specified in Ch.4 Sec.2 B702.

B 800 Lubrication system

801 The lubrication system shall be designed to provide allbearings, gear meshes and other parts requiring oil with ade-quate amount of oil for both lubrication and cooling purposes.This shall be maintained under all environmental conditions asstated in Ch.1 Sec.3 B200 of the Rules for Classification of

Ships.

802 The lubrication system shall include:

— an arrangement to take representative oil samples with re-spect to detecting water and particle contamination

— a filter of suitable fineness for gearing, hydraulics andbearings (see 702)

— if necessary, a cooler to keep the oil temperature within thespecified maximum temperature, when operating underthe worst relevant environmental conditions (see 801)

— for propulsion and dynamic positioning units it shall bepossible to change or clean filters without interrupting theoil supply

— if forced lubrication is required for operation of the unit,

single propulsion units are to have a standby pump withimmediate action. On vessels with two or more independ-ent and equal sized propulsion units one pump pr. unit willnormally be accepted.

803 For propulsion thrusters where wind milling may be det-

Table B1 Thruster type and load cycles

Type of thruster Minimum number of input shaftrevolutions at full power (N L load cycles)

Propulsion 1) 1·1010

Dynamic positioning 5·108

Auxiliary 5·107

1) For thusters subject to frequent overload (intermittent load), relevantload and corresponding accumulated number of load cycles are to beapplied, see also Ch.4 Sec.3 A101.

Table B3 Safety factors

SF SH SS

Azimuth steering gear- for surface hardened- for not surface hardened

1.51.5

1.151.0

1.4*1.2*

* Not applicable to slow speed gears (pitch line speed < 2 m/s)




DET NORSKE VERITAS

rimental, there shall be either:

— a shaft brake designed to hold (statically) twice the highestexpected wind milling torque, or

— an extra oil pump, which is not to be the same pump as thestandby pump.

The chosen version shall be automatically activated within 30

s after shutdown.804 For thrusters designed to operate at such low speeds thatan attached pump (if needed) cannot supply sufficient oil pres-sure, the following will be accepted:

— either an extra electric oil pump that is activated at a givenpressure, or

— 2 electric main pumps of the same capacity, one of whichis arranged as a standby pump with immediate action.These 2 electric pumps are to be supplied from differentswitchboards.


C 100 General

101 Regarding certification schemes, short terms, MSA andimportant conditions, see Ch.2 Sec.2.

102 The parts in a thruster may be tested and documented asdescribed in 200, or the entire testing and documentation ishandled by the manufacturer’s quality system, or combinationsof both. Such certification schemes are to be settled in a MSA.

C 200 Certification of parts

201 NV certificates are required for the following compo-nents and the certification requirements are given in the re-spective references or in this section:

— pinions and wheels for propeller drive, see Ch.4 Sec.2— pinions and wheels for azimuth steering, see Ch.4 Sec.2*— shafts, see Ch.4 Sec.1— clutches, see Ch.4 Sec.3— couplings, see Ch.4 Sec.4— propeller, see Sec.1— propeller nozzle, see Pt.3 Ch.3 Sec.2 of the Rules for Clas-

sification of Ships— hydraulic motor for steering, see Ch.6 Sec.6 of the Rules

for Classification of Ships.

* For propulsion thrusters which have high speed steeringgear actuators (axial hydraulic motor, electric motor etc.)which are combined with a mass produced reduction gearthe following certification requirements apply to the massproduced gear box:

— if the vessel has two or more independent propulsionthrusters and where each thruster has two or moresteering gear actuators, the certification of the gearmay be based on function testing only. The gearboxshall be conservatively chosen and able to handle allthe relevant loads for the steering gear. It is a condi-tion that the gearbox can be easily replaced. It is fur-ther a condition that the vessel will be fullymanoeuvrable with one azimuth thruster locked in theworst possible condition and the other(s) in operation.

C 300 Material and NDT testing

301 Material certificates containing chemical compositionand mechanical properties are required for:

— underwater housing (W)— inboard housing (W)— outer housing (non rotating) (NV)

— steering column or rotating support (NV)— propeller nozzle (NV).

302 Ultrasonic test certificate (W) is required for:

— steering column— welds in any part mentioned in 301 (extent to be specified

in approval).

The ultrasonic test shall be carried out at an appropriate stageof the manufacturing process. The test certificate shall refer toa recognised standard and approved acceptance levels.

303 Surface crack detection (MPI or dye penetrant) is re-quired in way of zones with stress raisers and in welded con-nections for:

— steering column (W)— housings (W).

The extent and acceptance criteria shall be specified in the doc-umentation submitted for approval.

304 Visual inspection shall be carried out of all parts men-tioned in 200 and 300 unless otherwise defined in a MSA.

305 Ancillaries, which are not part of the steering gear, suchas pumps, electric motors, coolers, piping, filters, valves, etc.that are delivered as integral parts of the lubrication, hydraulicoperation and cooling systems of the thruster, shall be checkedby the thruster manufacturer’s quality system as found rele-vant.

C 400 Assembling

401 Assembling of the drive gears regarding tooth contactshall be in accordance with the approved procedure and in thepresence of the surveyor. The surveyor shall check accessthrough inspection openings.

402 For assembling of other elements, see Ch.4 Sec.2 C500and Sec.1 C100. However, for auxiliary thrusters Sec.1 C102

and 103 need not be adhered to.

403 For propeller fitting, see Ch.4 Sec.1 H208.

D. Workshop Testing

D 100 Testing of assembled unit

101 For gear mesh checking, see Ch.4 Sec.2 D100 unlessother procedure is approved.

102 For clutch operation, see Ch.4 Sec.2 D200.

103 All hydraulic systems for steering, lubrication, pitchcontrol etc. shall be function and pressure tested.

For the steering system the test pressure shall be 1.5 times thedesign pressure pD as required in the Rules for Classificationof Ships, Pt.3 Ch.3 Sec.2.

For other hydraulic systems test pressure is 1.5 times the max-imum working pressure pW as required in Ch.6 Sec.6 of theRules for Classification of Ships. Regarding function testing of controllable pitch propellers, see Sec.1 C100.

104 The thruster unit shall be subjected to leakage testing(internal pressure, soap water test or similar).

E. Control, Alarm, Safety Functions and Indica-tion

E 100 General

101 For instrumentation and automation, including compu-ter based control and monitoring, the requirements in this itemare additional to those given in Ch.9.




DET NORSKE VERITAS

102 Additional requirements for vessels with class notationsDYNPOS-AUTS, DYNPOS-AUT, DYNPOS-AUTR andDYNPOS-AUTRO see the Rules for Classification of Ships,Pt.6 Ch.7 Sec.3 F100.

103 Alarms and indications shall be initiated, as applicable,for the faults given in Table E1.

For steering gear see also the Rules for Classification of Ships,

Pt.3 Ch.3 Sec.2.Additionally, an alarm shall be initiated on the bridge in caseof power failure of alarm, control and safety system as requiredin Ch.9 Sec.2 C100.

104 Any alarm condition in the thruster plant shall initiatean alarm on the bridge with individual or group-wise indica-tion. For HS, LC and NSC, all alarms shall have individual in-dication on the bridge.

E 200 Bridge control

201 It shall be possible to stop the propeller from the bridgeby means of a system independent of the remote control sys-

tem.

F. Arrangement

F 100 General

101 The installation of a thruster, including alignment shallbe such as to give satisfactory performance under all operatingconditions.

102 A shaft sealing box shall be installed to prevent waterfrom gaining access to internal parts of the thruster or into theship. The sealing arrangement shall protect steel shafts fromseawater, unless corrosion-resistant steel, especially approvedby the Society, is used.

103The arrangement of flexibly mounted side thrusters shallprovide effective protection against flooding. Such thrusters

shall be placed in a separate watertight compartment, unlessthe flexible sealing arrangement contains two separate effec-tive sealing elements. An arrangement for indication of leak-age into the space between the inner and outer sealing shall be

provided. The arrangement shall allow inspection of such seal-ings during bottom survey without extensive dismantling.

104 Azimuth thrusters shall be mounted in a watertight com-partment unless the penetration through the hull is situatedabove the deepest loaded waterline.

F 200 Propulsion thrusters

201 When propulsion is provided by thrusters with underwa-ter gear or when access to the internal parts of the thruster isnot possible from inside the vessel, there shall be at least 2 sep-arate, equal sized thruster units.

202 Propulsion thrusters shall be provided with means for lo-cal (normally in the thruster compartment) control of steeringgear and propeller pitch or speed. Necessary indications of az-imuth and propeller pitch positions and means for communica-tion with the navigating bridge are to be provided. In addition,

Table E1 Required instrumentation and alarms

Item Indication Alarm Comments

Lubrication

Lubrication oil pressure Local 1) Low Automatic start of standby pump if required

Lubrication oil temperature Local High 1)

Lubrication oil level Local Low

Steering system

Azimuth angle Local and remote Indication on bridge and steering gear compartment

Steering system oil pressure Local Low Alarm on bridge and machinery space

Steering system oil level Local Low Alarm on bridge and machinery space

Pump motor overload, power andphase failure 2) X Alarm on bridge and machinery space

Propeller

Propeller r.p.m. (if not constant) Remote Remote indicators to be fitted on the bridge

Rotational direction (if not constant) Remote Remote indicators to be fitted on the bridge

Propeller pitch for CP-propeller 3) Local and r emote Indication on bridge and machinery space

Servo oil pressure Local Low Automatic start of standby pump if required

Servo oil temperature 1) Local High Required if shaft power > 1500 kW

Servo oil level Local Low 1)

Servo oil filter, differential pressure High 1)

Prime mover

Overload of prime mover Remote X 4) Indication (kW-meter) on bridge for CP plants with electric mo-tor. For diesel engines, see Ch.3 Sec.1 E

Stop of prime mover X For diesel engines see Ch.3 Sec.1 E

Bilge system High

1) Not required for auxiliary thrusters.

2) Applicable to steering gear power units on propulsion thrusters.

3) The following pitch settings to be marked on the local pitch indicator: Mechanical pitch limits ahead and astern, pitch at full ahead running, maximumpitch at maximum permissible astern r.p.m., pitch at zero thrust.

4) Alarm set point to be according to approved rating.

Terms:Indication; local – gauge fitted on the relevant component or system.Indication; remote – indication may be in machinery control room, bridge or other relevant place.




DET NORSKE VERITAS

visual compass readings to all steering positions shall be ar-ranged.

203 Azimuth steering gears shall comply with the rules forsteering gears in the Rules for Classification of Ships, Pt.3Ch.3 Sec.2 with respect to the arrangement, performance andother general requirements as applicable. It shall be possible tolock the unit in all required positions to prevent it from freeturning if the steering gear is inoperable and allow it to be usedto produce thrust in locked position.

G. Vibration

G 100 Torsional vibration

101 For diesel driven thrusters, see Ch.3 Sec.1G.

102 For electric motor driven tunnel thrusters calculation of the first and second natural frequency shall be submitted. Theblade frequency shall normally not be in the range 0.8 to 1.2times the first natural frequencies. For all other electric motordriven thrusters calculations of natural frequencies includingHolzer tables shall be submitted. Forced torsional vibrations(propeller excitation, see Ch.3 Sec.1 G302 h) shall be made fornormal operation as well as for extreme steering manoeuvres.The excitation used for extreme steering manoeuvres shall besubstantiated.

Normally, for propulsion thrusters the blade frequency shallnot be in the range of 0.7 to 1.3 of the first natural frequency.

Application factors below KA = 1.10 will not be accepted forpropulsion plants. Verification of application factors throughmeasurements may be required (normally if vessel speed > 10knots and KA < 1.2).

G 200 Torsional impact vibration

201 For electric motor driven thrusters, with star-delta or di-rect start, impact calculations are to be made and the peak torque shall not exceed the approved values or to exceed 1.5times the rated torque.

Parameter variations such as delay time in star-delta shift, startwith cold oil, etc. shall be considered, see also Ch.2 Sec.3

A101.

H. Installation Inspection

H 100 Installation onboard

101 For accessible thruster gears, the requirements in Ch.4Sec.2 H apply.

102 For shaft alignment, propeller fitting and assembly of shafting components, the requirements in Ch.4 Sec.1 H apply.

I. Shipboard testingI 100 Sea trial

101 The requirements in Pt.3 Ch.3 Sec.2 K400 of the Rulesfor Classification of Ships apply. Emergency operation (seeF202) shall be tested.

102 Steering and reversing functions shall be tested underthe most severe permissible conditions.

103 Accessible thruster gears shall be inspected as in Ch.4Sec.2 I.




DET NORSKE VERITAS

SECTION 4COMPRESSORS

A. General

A 100 Application101 The rules apply to all types of compressors intended forthe following systems:

— starting air— instrument air— breathing gas (monobaric and hyperbaric systems)— refrigerating (for ships having additional class notations

Reefer, RM or RM Container) see Pt.5 Ch.10 Sec.3B600 of the Rules for Classification of Ships

— evaporated cargo compression (for ships having class no-tation Tanker for Liquefied Gas).

— inert gas production (when such a system is required bySOLAS).

102 Design approval is required for all compressors with ashaft power exceeding 200 kW.

103 The rules also apply to all types of compressors intendedfor systems with pressure above 40 bars, irrespective of the

functions mentioned in 101 and limitations in 102.A 200 Documentation

201 Plans and particulars according to Table A1 shall be sub-mitted for design approval.

The plans shall include necessary details with regard to scant-lings and arrangements as well as material specifications andheat treatments.

For compressors of special type and design, the extent of thedocumentation shall be considered in each case.

Documentation of burst test will be accepted as an alternativeto calculations.

202 For requirements for instrumentation and automation,

including computer based control and monitoring, see Ch.9Sec.1.

B. Design

B 100 General

101 All compressors shall be protected by suitable safetyvalves. The safety valves shall be set to open at the design pres-sure. For starting air compressors, see also Pt.4 Ch.7 Sec.6B200.

Guidance note:

The design pressure must be sufficiently higher than the workingpressure in order to have suitable margins for setting of the safetyvalve.


102The piping to and from the compressor shall be arrangedin order to prevent condensation from entering the cylinders.

103 Starting air compressors shall satisfy the requirements of Ch.6 Sec.5 J of the Rules for Classification of Ships.

104 Refrigerating compressors shall satisfy the requirements

of Pt.5 Ch.10 Sec.3 B600 of the Rules for Classification of Ships.

105 Compressors intended for breathing gas systems shallcomply with the requirements in the Rules for Certification of Diving Systems Pt.6 Ch.1 Sec.4. Means shall be provided toavoid oil or poisonous gases from entering the breathing airsystem.

106 Gas compressors will be especially considered and shallnormally comply with a recognised national or internationalstandard.

107 Compressors intended for inert gas production shall sat-isfy the requirements of Pt.5 Ch.4 Sec.16 of the Rules for Clas-sification of Ships.

B 200 Crankshafts201 Crankshafts shall include a satisfactory safety factoragainst fatigue failures. Various calculation methods may beused. Item 102 gives one method for evaluation of safetyagainst fatigue in the web fillets. The method applies for crank-

Table A1 Documentation

Component Drawing Material specification

Calculations Miscellaneous

Compressor assembly I

Crankshaft A A

Shaft strength: UR Torsional vibration calculations: A

NDT

Connecting rod I I

Cylinder and -head with bolts I I

Rotors (w/ blades) A A UR NDT

Casing A A Containment calculations: UR

Internal piping I

Particulars:

— medium— design pressure for all stages— working temperature— working capacity— maximum shaft power and –speed

I

Alarm set points and delay times A

AIURNDT

====

For approvalFor informationUpon requestNon-destructive testing plan




DET NORSKE VERITAS

shafts made of forged and cast steel and nodular cast iron in-tended for one or multistage compressors with the cylindersarranged in line, V or W. More detailed methods may be espe-cially considered.

Guidance note:

The stresses in the crankpin fillet are to fulfil the following crite-rion:

σ b = the bending stress amplitude in the fillet (N/mm2)

σ f = the fatigue strength (N/mm2)

S = the minimum safety factor

For the fatigue criteria mentioned below, the following minimumsafety factor applies:

S = 1.4

This safety factor includes the influence of torsional stresses inthe fillets, which for the sake of simplicity are neglected in thismethod.

The fatigue strength is to be calculated as follows:

σ f = (0.33 σ B + 40) k m

σ B = ultimate tensile strength of the material (N/mm2)

k m = material factor, see Table B1

The bending stress amplitude is to be evaluated as follows:

σ b = 0.7 σ nom α

0.7 = factor to correlate the pulsating bending stress rangeinto an equivalent single amplitude reversed stress

α = fatigue notch factor for bending

σ nom = MB / WB (N/mm2)

MB = bending moment in the middle of the web nearest thecentre of the bearing span

WB = sectional modulus of the web

D 1) = cylinder bore (mm)

P 1) = design pressure (bar)

L = distance between the centres of two adjacent bear-ings (mm), see Fig. 1

a = distance from the center of a bearing to the center of the web nearest the center of the bearing span (mm),see Fig. 1

b = L − a, (b ≥ a) (mm)

k d = design factor, see Table B2

1) For multicylinder arrangements on one bearing span, use themaximum of the individual PD2.

W B = B W 2 / 6

B = width of the web (mm), see Fig. 1

W = thickness of the web (mm)

The fatigue notch factor for bending may be calculated as fol-lows:

α = 1 + η (α th − 1)

η = notch sensitivity factor

α th = theoretical stress concentration factor (referred to webbending stress)

η = 0.62 + 0.2 log R + σ y 10-4 log (400 / R)

(if calculated > 1, η = 1 applies)

σ y = the yield strength of the material (N/mm2)

R = the actual fillet radius (mm)

α th = 3.0 f(A/d) f(W/d) f(B/d) f(R/d)

f(A/d) = 1 − 0.8 A/d

f(W/d) = 1 + 2.2 (W/d − 0.35)

f(B/d) = 1 + 0.4 (B/d − 1.45)

f(R/d) =

A = pin overlap (mm), see Fig. 1

d = diameter of the crankpin (mm).

Fig. 1

Crank throw for compressor


202 For keyway connection, see Ch.4 Sec.1 B500.

B 300 Rotors

301 Calculation of the rotor strength shall be carried out inaccordance with recognised standards.

B 400 Rotor casing

401 The strength of the casing may be documented by calcu-

lations in accordance with recognised standards.402 Proof tests may be used to establish the allowable designpressure of the rotor casing. The proof test shall be carried outin accordance with the ASME Boiler and Pressure VesselCode, Section VIII, Division I, or other recognised standards.

Table B1 Material factor

Material k mForged steelCast steel

Nodular cast iron

1.00.8

0.9

σ b

σ f

S-----≤

MBk dπ D

2

P a b40L

------------------------------=

Table B2 Design factor

Design k d

In lineV-90, W-90V-60, W-60V-45, W-45

1.001.151.501.75

0.22

R d ⁄

----------------





C 100 General

101 The certification principles are described in Ch.2 Sec.2.The principles of manufacturing survey arrangement (MSA)are described in Ch.2 Sec.2 C100.

Guidance note:

It is advised to establish an MSA with sub-suppliers deliveringmaterials or parts mentioned in 300. This applies also to thosedocumented by work certificate (W) and test report (TR), andshould at least verify that the premises for using W and TR arefulfilled.


102 Material documentation is described in Ch.2 Sec.3.

C 200 Certification, testing and inspection of parts

201 Certificates for product and material according to TableC1.

202 All parts subject to pressure of the compressors shall behydraulically pressure tested (W) to 1.5 times the design pres-

sure for the respective parts. The test pressure need not exceedthe design pressure by more than 70 bars.

D. Workshop testing

D 100 General

101 Function testing and setting of the safety valves shall becarried out on each compressor in the presence of a surveyor.

102 A capacity test shall be carried out with the compressorrunning at design condition (rated speed, pressure, tempera-ture, type of gas, etc.). The capacity test may be waived forcompressors produced in series and when previous tests havebeen carried out on similar compressors with satisfactory re-sult. The capacity test shall be witnessed by a DNV surveyor.

E. Control and Monitoring

E 100 General

101 The requirements of Ch.9 are to be complied with whereapplicable.

102 Compressors shall be supplied with an alarm for highpressure.

103 Compressors with shaft power exceeding 1500 kW shallbe supplied with an alarm for high bearing temperature.

F. Arrangement Onboard

F 100 General

101 Air compressors shall be arranged and located so as tominimise the intake of oil or water contaminated air.

G. VibrationsG 100 Torsional vibration

101 For reciprocating compressors with shaft power exceed-ing 200 kW, torsional vibration calculations shall be deter-mined according to the requirements in Ch.3 Sec.1 G300 asrelevant.

H. Installation Inspection

H 100 General

101 After installation onboard, the compressor and the sys-tem to which it is connected, shall be function tested underworking conditions. See also Ch.6 Sec.5.

102 The function test shall include testing of any control andsafety functions.

H 200 Vibration

201 For resilient mounted reciprocating compressors, the vi-bration shall be observed by the surveyor and considered withregards to hooked-up connections. See also Ch.3 Sec.1.

Table C1 Requirement for testing, inspection and certification

Component Product cer-tificate

Materialcertificate

Ultrasonictesting

Crackdetection

Hydraulictesting

Dimensioninspection

Other

CompressorNV

Function test (NV)Capacity test (NV)

Crankshaft W W W W

Connecting rod TR

Cylinder with head TR W

Rotors W W W W

Casing W W

dnv propeller

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