OFFSHORE STANDARDS DNVGL-OS-E402 Edition July 2019 Diving systems The electronic pdf version of this document, available free of charge from http://www.dnvgl.com, is the officially binding version. DNV GL AS FOREWORD DNV GL offshore standards contain technical requirements, principles and acceptance criteria related to classification of offshore units. © DNV GL AS July 2019 Any comments may be sent by e-mail to [email protected] This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this document. The use of this document by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibility for loss or damages resulting from any use of this document. CHANGES – CURRENT This document supersedes the January 2017 edition of DNVGL-OS-E402 Diving systems. Changes in this document are highlighted in red colour. However, if the changes involve a whole chapter, section or subsection, normally only the title will be in red colour. Changes July 2019 Topic Reference Description Clarification of surface system Ch.2 Sec.1 [2.1] A requirement to submit treatment tables has been added, requirements. with operational times redefined accordingly. The ability to add additional components to a system (LDC/differing mobilisation Changes - current arrangements) is now considered as well. General updates. Ch.2 Sec.2 [4.1.5] Guidance to allow the use of small industrial sourced gas bottles without a corrosion allowance added. Ch.2 Sec.3 [1.9.12] Temperature shut downs based on lubricant added. Ch.2 Sec.6 [3.1.1] Over the side/stern operation for surface supplied diving is now restricted to a maximum significant wave height of 2 meters.. Ch.3 Sec.1 [9.2.1] Removal of the minimum hydro test value for windows which conflicted with ASME PVHO. Ch.3 Sec.1 [9.3.9] Environmental control testing has been expanded to reflect current practice. Ch.3 Sec.1 [2.2.4] Typical areas to be considered during the risk analysis for evacuation have been added including the impacts of split level diving. Ch.3 Sec.1 [2.2] Requirements have been added within the systematic review (FMEA) to collate findings that require actions in operation. Testing requirements for the systematic review (FMEA) added. Ch.3 Sec.1 [2] The purpose and content of the safety objective is rewritten, primarily to be more descriptive of expectations toward the document. Appendix A has been deleted. Ch.3 Sec.2 [2.1.10] Requirements for the use of expansion joints (bellows) has been added. Ch.3 Sec.2 [4.1.4] A method to allow ancillery pressure vessels to follow the same inspection frequency as the chambers has been added. Ch.3 Sec.3 [5.1.6] Limitation on NPT thread size added. Ch.3 Sec.3 [5.3.1] Equalisation lines are removed. Ch.3 Sec.3 [6.1.4] Requirements to the performance of bell insulation added. Ch.3 Sec.3 [6.7.1] Guidance on treatment for bacteria within chamber gas reclaim added. Ch.3 Sec.4 [5.4.1] Volume within gas analysis pipelines is now considered for time delays. A timed option instead of analysis for emergency bell CO2 control added. Offshore standards — DNVGL-OS-E402. Edition July 2019 Page 3 Diving systems DNV GL AS Topic Reference Description Ch.3 Sec.5 [2.1.3] A description of how to handle items that cannot be certified with respect to limiting ignition risk within chambers is added based upon USN. Ch.3 Sec.5 [4.1.5] Fixed fire fighting capacity in the SPHL is now differentiated from DDCs. Ch.3 Sec.6 [2.1.6] Line out counter now specified as a requirement. Ch.3 Sec.6 [2.3.3] Requirements for bell buoyancy materials added based upon UWT rules. Ch.3 Sec.8 [1.19] Launch requirements for HRCs added. Changes - current Ch.3 Sec.8 [1.6] The interpretation regarding use of the bell as an evacuation method has been copied to this document. Simplification of redundancy Ch.2 Sec.1 [4] Base redundancy case clarified while the safety objective is requirements for surface moved to [4.6]. This should allow simple systems to just follow systems. the base redundancy concept. Ch.2 Sec.6 [2.3.8] Requirements to safety interlocks within LARS systems have been added. The needed Interlocks for coordinating A frame and winch movements is also clarified. Ch.2 Sec.6 [2] The required arrangement of LARS is clarified in [2.1] and the required minimum redundancy specified in [2.2.2]. Update requirements for air Ch.2 Sec.1 [4.3.2] Essential services are now required to last the entire treatment dive equipment. table. Ch.2 Sec.1 [4.6] The safety objective has been rewritten to try and clarify intent. Requirements have been added within the systematic review (FMEA) to collate findings that require actions in operation. Testing requirements for the systematic review (FMEA) added. Ch.2 Sec.1 [5.2.3] Temperature ranges redefined, particularly for ventilated chambers that have internal temperatures linked to ambient temperature. Ch.2 Sec.2 [2.2.3] Testing of the PVHO may now be based upon actual cycles experienced. Where chambers are not used operationally but in a standby function, acceptance of records is accepted. A means to include ancillary pressure vessels within the same testing as the chamber is described. Ch.2 Sec.3 [2.3.3] Emergency gas stored within the basket/wet bell now specified as 20 min duration. Ch.2 Sec.3 [2] Primary, secondary and emergency gas supplies have been defined and gas storage requirements are based upon the treatment table specified. Ch.2 Sec.3 [4.2.1] Hot water for the divers is expected for systems operating below 3oC. Ch.2 Sec.3 [4.3.2] Where heating and cooling is provided temperature requirements have been added. Offshore standards — DNVGL-OS-E402. Edition July 2019 Page 4 Diving systems DNV GL AS Topic Reference Description Ch.2 Sec.3 [4.6.1] Requirements to ventilated chambers have been added which will govern gas storage and operating temperatures. Ch.2 Sec.3 [4.6.2] All systems will now test environmental control including ventilated chambers in order to confirm ventilation rates. Ch.2 Sec.3 [4] It is recognised that there is no clear temperature cut offs for surface supplied diving and the concept of applying a temperature rating has been revised. Only systems with active heating and cooling will now get a definative operating temperature range. Others will be based upon deviation from ambient temperature. Ch.2 Sec.5 [3.1] Position on what constitutes the outer area and the Changes - current requirements that apply for surface systems is clarified and based on evacuation time. Ch.2 Sec.8 While requirements remain essentially with the shelf authorities the following requirements have been added. Evacuation time, the need to supply O2 within the normal lifeboats and the ability to recover from the water. Editorial corrections In addition to the above stated changes, editorial corrections may have been made. Offshore standards — DNVGL-OS-E402. Edition July 2019 Page 5 Diving systems DNV GL AS CONTENTS Changes – current............................................................ 3 Chapter 1 Introduction................................................... 10 Contents Section 1 General...............................................................................................................10 1 Introduction....................................................................................................... 10 2 References......................................................................................................... 11 Chapter 2 Surface diving systems...................................27 Section 1 Design philosophy and premises........................................................................27 1 Introduction....................................................................................................... 27 2 Documentation................................................................................................... 27 3 Safety philosophy...............................................................................................28 4 Surface diving system philosophy......................................................................29 5 External and internal environmental conditions.................................................33 Section 2 Pressure vessels for human occupancy, gas storage and other purposes...........36 1 Introduction....................................................................................................... 36 2 General principles for design of chambers.........................................................40 3 Welded pressure vessels, materials, fabrication and strength........................... 44 4 Gas cylinders......................................................................................................45 5 Acrylic plastic windows......................................................................................46 Section 3 Life support systems including piping, hoses, valves, fittings, compressors, filters and umbilicals.................................................................................................... 49 1 Introduction....................................................................................................... 49 2 Gas distribution and control system.................................................................. 53 3 Gas storage........................................................................................................57 4 Diver’s heating and environmental conditioning in chambers............................ 58 5 Piping systems..................................................................................................