Part 4 Machinery and systems Chapter 6 Piping systems, pumps and compressors

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1 RULES FOR CLASSIFICATION Underwater technology Edition December 2015 Part 4 Machinery and systems Chapter 6 Piping systems, pumps and compressors The content of this service document is the subject of intellectual property rights reserved by ("DNV GL"). The user accepts that it is prohibited by anyone else but DNV GL and/or its licensees to offer and/or perform classification, certification and/or verification services, including the issuance of certificates and/or declarations of conformity, wholly or partly, on the basis of and/or pursuant to this document whether free of charge or chargeable, without DNV GL's prior written consent. DNV GL is not responsible for the consequences arising from any use of this document by others. The electronic pdf version of this document, available free of charge from is the officially binding version.

2 FOREWORD DNV GL rules for classification contain procedural and technical requirements related to obtaining and retaining a class certificate. The rules represent all requirements adopted by the Society as basis for classification. December 2015 Any comments may be sent by to rules@dnvgl.com If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of DNV GL, then DNV GL shall pay compensation to such person for 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 compensation shall never exceed USD 2 million. In this provision "DNV GL" shall mean, its direct and indirect owners as well as all its affiliates, subsidiaries, directors, officers, employees, agents and any other acting on behalf of DNV GL.

3 CURRENT CHANGES This is a new document. The rules enter into force 1 July Part 4 Chapter 6 Changes - current Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 3

4 CONTENTS Current changes...3 Section 1 General Introduction References...5 Section 2 Principles of design and construction Pipes, valves, fittings, hoses and pumps Bilge, compensating and trimming equipment for manned submersibles Compressed air systems Hydraulic systems Oxygen systems Compressors Operational Media...13 Part 4 Chapter 6 Contents Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 4

5 SECTION 1 GENERAL 1 Introduction 1.1 Application The rules in this chapter apply to all piping systems, including valves, fittings, hose assemblies pumps and compressors, which are needed to operate an underwater system The requirements given in this chapter shall be regarded as supplementary to those given for main class SHIP Pt.4 Ch.6. 2 References Piping systems shall comply with the technical requirements for class I piping systems in RU SHIP Pt.4 Ch.6. In piping systems with no relevance to safety, a lower pipe class may be applied, if agreed by the Society. The documents to be submitted to the Society for approval and the initial tests and trials are stated in RU SHIP Pt.4 Ch.6 and SHIP Pt.5 Ch.1 to RU SHIP Pt.5 Ch.9. The technical requirements for hose lines in umbilicals are defined in Pt.4 Ch.5.The necessary markings for machinery elements are summarized in Pt.4 Ch.1 Sec.2. Part 4 Chapter 6 Section 1 Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 5

6 SECTION 2 PRINCIPLES OF DESIGN AND CONSTRUCTION 1 Pipes, valves, fittings, hoses and pumps 1.1 General Expansion in piping systems, especially at the pressure chambers, shall be compensated by pipe bends or compensators. Attention shall be given to the suitable location of fixed points It shall be possible to evacuate, drain and vent pipelines Suction ends in pressure chambers shall be protected against inadvertent covering and suction of foreign objects All pipes, valves, fittings and pumps shall be dimensioned for a design pressure at least equal to the maximum allowable working pressure of the system to which it is fitted Piping systems which may be subjected to a higher pressure than designed for shall be fitted with a pressure relief device especially where low-pressure systems are supplied from high-pressure system. The total relieving capacity shall be sufficient to maintain the system pressure at not more than 110% of design pressure. The relief device shall be located adjoining, or as close as possible, to the reducing valve All systems shall be provided with means to manually relieve the pressure All pipes, valves, fittings and pumps for manned submersibles which can be loaded with the diving pressure shall be designed additionally for 1.1 times the collapse diving pressure (CDP) according to the load case from outside or inside. Unmanned underwater systems shall be designed for 1.0 times the collapse diving pressure (CDP) Piping systems conducting gas in life support systems shall be cleaned in accordance with an approved cleaning procedure conforming to requirements given in ASTM G93-96 Standard Practice for Cleaning Methods and Cleanliness Levels for Materials and Equipment Used in Oxygen-Enriched Environments. Other standards may be used upon acceptance from the Society Pipes which are led through the pressure hull wall shall be fitted with two shut-off devices, one of which shall be located directly at the hull wall All high-pressure piping shall be protected against mechanical damage Gas pipes and electric cable conduits shall be routed separately wherever possible. Piping which may be susceptible to mechanical damage shall be adequately protected Piping passing through spaces inaccessible for maintenance shall consist of one piece Shut-off devices shall conform to a recognized standard Valves and fittings with screw-down covers or spindles shall be safeguarded against unintentional unscrewing of the cover Valves are normally to be closed by clockwise rotation Design and arrangement of valves shall be such that open and closed positions are clearly indicated. Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 6

7 All valves acting as sea connections shall be so designed that the tapered plug opens against the external pressure. Taper cocks shall not be used Bite and compression type couplings and couplings with brazing, flared fittings, welding cones and flange connections shall be designed according to a recognised standard and be approved for the intended purpose The suitability of a design of each hose assembly type shall be verified as per following criteria: a) Establishment of the maximum allowable working pressure on basis of burst pressure tests. The minimum burst pressure for liquids is 4 times, for gases 5 times the maximum allowable working pressure. b) Hoses that are subject to external pressure are also to be certified for the external design pressure c) Flexible hoses, except for umbilicals, should be reduced to a minimum. d) Flexible hoses shall not replace fixed piping. e) Short lengths (up to 2 m) of flexible hose may be used when necessary to admit relative movements between machinery and fixed piping systems. For assemblies incorporating specially approved hoses and securing arrangements, lengths up to 5 m may be permitted if fixed piping is not practicable. In such cases, securing arrangements shall be in place at least 1 m intervals along the length of the hose. In addition to the couplings, the hoses shall be secured in such a way as to prevent the hose from whip lashing in the event that the coupling fails. When applicable, couplings shall incorporate bends so that kinks in the hoses are avoided. f) Flexible hoses with couplings shall be certified according to the technical requirements of RU SHIP Pt.4 Ch.6. g) Hot water hoses shall be designed for conveyance of fluids of temperatures not less than 100 C Flexible metallic hoses shall comply with ISO , BS6501 or equivalent. These types of hoses shall not be installed in systems subject to excessive vibrations or movements. h) Flexible synthetic hoses shall comply with SAE J 517, DIN EN 853, 856, 857 or equivalent. The internal oil resistance test may be omitted for hoses intended for gas and water only Pressure regulators shall have more than one full rotation from fully closed to fully opened position. Particle filters shall be provided on the high-pressure side of pressure reducers and close to where high pressure gas sources are connected Systems with hose lines shall be fitted with a device for relieving the pressure before the hoses are disconnected. 1.2 Testing Hydrostatic testing of piping systems shall be in accordance with the technical requirements and as for corresponding pipe class (in breathing gas systems pertaining to class I piping systems) Piping for the life support systems shall be pressure tested to 1.5 times the maximum working pressure. Hydraulic systems may, however, be tested to less than 1.5 times the maximum working pressure Piping systems intended to be used in breathing gas and oxygen systems shall be tested for purity in accordance with requirements given in ASTM G93-96 or an agreed standard The tests shall comprise measurement of contamination of the cleaning agent left in the piping system The gas storage and life support systems for gas shall be tested for leakage at low pressures and the maximum working pressure. Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 7

8 2 Bilge, compensating and trimming equipment for manned submersibles 2.1 Submersibles shall be equipped with a bilge system capable of freeing all the spaces inside the vehicle from water due to condensation and leakage. 2.2 To prevent water from penetrating into the vehicle through the bilge system, two non-return valves shall be mounted in the bilge system. One of these non-return valves shall be placed in the pipe close to the suction box. The other one shall be placed close to the pressure hull penetration valve. 2.3 Where the bilge, compensating and trimming systems are interconnected, the connecting pipes shall be fitted with valves in such a way that seawater is prevented from penetrating inside the vehicle through the bilge system even in the event of faulty switching of the valves or when the valves are in intermediate positions. 2.4 Bilge pumps shall be of the self-priming type. 2.5 The bilge system shall be provided with at least one standby pump. In case of interconnection of bilge, compensating and trimming systems the standby pump shall be able to serve all systems. 2.6 Where tanks are freed only by pumps, the standby pump shall be connected to the emergency power supply. 3 Compressed air systems 3.1 If air receivers are not changed, a compressor respectively a transfer system shall be provided for charging the compressed air receivers. 3.2 The compressed air systems shall be fitted with valves to prevent unintentional pressure equalization between different systems. 3.3 Where pressure-reducing valves are fitted in piping systems for diving, compensating and trimming tanks, these shall be redundant. In single cases provision can be made for bypassing with manual control. Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 8

9 3.4 Compressed air systems shall be equipped with a sufficient number of pressure indicators. 3.5 Compressed air systems which come into contact with seawater shall be designed adequately and to be separated from other systems. In addition measures shall be taken to prevent possible penetration of seawater into the compressed air system. 4 Hydraulic systems 4.1 Wherever necessary, the possibility of a pressure rise due to the penetration of gas or seawater into the system shall be observed. To protect the hydraulic system from over-pressurization, a closed circuit safety valve shall be fitted and the discharged oil shall be returned into the system. 4.2 Hydraulic systems essential to the safety of the submersible or the diving system shall be redundant e.g. two power driven pumps, one power driven pump and one hand-operated emergency pump. Independent submersibles shall be equipped with two power driven pumps. Guidance note: In individual cases, hydraulic systems not designed for continuous operation may also be equipped with hand-operated pumps. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e Hydraulic systems shall be fitted with filters to keep the hydraulic fluid clean. In addition, provision shall be made for venting and dewatering the system. Hydraulic fluid tanks shall be fitted with level indicators. Wherever necessary, hydraulic systems shall be equipped with means of cooling the hydraulic fluid. 4.4 Hydraulic lines should not be routed close to oxygen systems. 4.5 When selecting the hydraulic oil, allowance shall be made not only for the service conditions but also for the conditions occurring during the commissioning or repair. 4.6 Hydraulic systems shall be equipped with all the indicating devices necessary for the functioning of the system. Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 9

10 5 Oxygen systems 5.1 Pipelines for mixed gases containing more than 25% oxygen shall be treated as pure oxygen lines. 5.2 All components and materials included in the system shall be suitable for oxygen in relation to their type and application and shall be carefully cleaned according to the agreed standard before putting into operation. Guidance note: According to IGC DOC 33/06 the allowable value for residual oil and/or grease is 200 mg/m² for high pressure oxygen system (> 30 bar) and this shall not be exceeded. ASTM G93 Standard Practice: O 2 cleanliness levels A C or F ( 200mg/m²) are acceptable. Further recommended standard: MIL-STD e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e Manometers for oxygen and other gases with more than 25% oxygen shall be marked as free of oil and grease. 5.4 In piping systems containing oxygen only, spindle valves are permissible. Emergency shut-off quick-closing valves, like e.g. ball valves, may be provided at a suitable location, if they are adequately marked. Shut-off valves installed prior to pressure reduction shall be secured against unintentional activation. 5.5 Wherever possible the pressure in oxygen lines shall be reduced at the gas storage facility to a pressure which is still compatible with an adequate gas supply. 5.6 Oxygen pipes shall be routed separately from oil pipes. Pipelines carrying oxygen under high pressure shall not be routed through accommodation spaces, engine rooms or similar compartments. 5.7 The exhaust of safety relief valves (see [1.1.5]) and other exhaust pipelines of oxygen systems shall be routed into a safe area. Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 10

11 5.8 In systems conducting oxygen, all materials in contact with this gas shall be oxygen shock tested according to: EN 738-1, -2 and -3:1997/1998 Pressure regulators for use with medical gases or equivalent standard applicable to the particular component. (See also EN 849:1996, EN ISO :1997 and EN ISO 2503:1998 in informative references) For piping of copper, copper alloys and austenitic steels with chromium-nickel content above 22%, the test can be waived. Guidance note: Oxygen pressure shock tests are described in the standards referred to. However, the test includes the following principles: Commercial grade oxygen (99% pure) test gas is applied as follows for 3 identical test specimens: the test pressure is not less than the design pressure the test specimen is preheated to 60 C and exposed to a gas pressure shock up to the specified test pressure with test gas preheated to 60 C each test consists of 20 pressure shocks at approximately 30 seconds intervals. The total exposure time to each pressure shock is 10 seconds, and the gas pressure is released after each shock. The pressure increase rate during each pressure shock is obtained by a valve with an opening time less than 10 milliseconds. ---e-n-d---of---g-u-i-d-a-n-c-e---n-o-t-e--- Where stainless steel is used for oxygen lines with operating pressures above 40 bar only high-alloyed Cr-Nisteels with a content of Cr and Ni of together at least 22% or Cr-Si-steels with a Cr content of at least 22% are acceptable Connection pieces for oxygen shall be designed to avoid burnout Spindle valves for oxygen shall be so designed for nominal diameters above 15 mm and operating pressures of more than 40 bar, that the spindle gear is outside the gas space Sealing materials which come into contact with oxygen may only be used if their suitability for pressures, temperature and type of mounting is proven For valves, fittings and connections for oxygen, only lubricants that are approved for the operating conditions are permissible Hoses shall be suitable for oxygen Hoses for oxygen should, as far as practicable, be of fire-retardant construction. Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 11

12 5.15 All pipelines penetrating the wall of the pressure chamber shall be pipe class I Concerning the requirements for oxygen plants in life support systems for submersibles see Pt.4 Ch.4 Sec.3 [2.1] and for manned hyperbaric systems see Pt.5 Ch.4 and Pt.5 Ch.5. 6 Compressors The following requirements are supplementary to SHIP Pt.4 Ch.5 Sec Certification requirements Compressors shall be approved by the Society and a certificate according Table 1 shall be issued. Table 1 Certification of compressors Object Certificate type Issued by Certification standard* Additional description Compressor VL Society *Unless otherwise specified the certification standard is the rules. 6.2 Compressors shall be equipped with all the accessories and instrumentation which are necessary for effective and reliable operation. 6.3 Compressors shall be designed for the gas types, pressure rating and delivery rates as specified by the operation and so designed that the gas is protected against contamination by lubricants. 6.4 The content of contaminants in delivered breathing gas from compressors shall not exceed acceptance criteria given in EN or equivalent standard. 6.5 Compressors shall be installed in such that no harmful gases can be sucked in. 6.6 Where a compressor is used for the divers' air supply, a receiver shall be interposed for the compensation of pressure variations. 6.7 Oxygen compressors are to be installed in separate spaces with adequate ventilation. Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 12

13 6.8 Suitable protection shall be provided around moving parts, and the safety relief valves shall exhaust to a safe place. 6.9 Compressors shall be tested for the gas types, pressure and delivery rate intended. The tests shall incorporate measurements of humidity and possible contaminants in the gas delivered Compressor components subjected to pressure shall be hydrostatic tested in accordance with the design code. 7 Operational Media 7.1 Operational media such as hydraulic fluids, lubricants, etc. shall be selected in accordance with the proposed ambient conditions. They shall not tend to congeal or evaporate over the whole temperature range. 7.2 Operational media shall not contain toxic ingredients which are liable to be hazardous to health through skin contact or when given off in fumes. 7.3 Operational media shall not be corrosive or attack other operating equipment (e.g. seals, hose lines, etc.). Rules for classification: Underwater technology DNVGL-RU-UWT-Pt4Ch6. Edition December 2015 Page 13

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