1.1 Objective The objective of this document is to describe the Company requirements and design practices within Piping Engineering. TR1951 shall apply to both onshore and offshore facilities. For offshore facilities TR1951 shall apply to all piping systems contained within the facility (topsides and hull). The facility limits shall with respect to external interfaces on offshore plants be considered as being the following:Import risers – from and including riser ESD valves Export risers – to and including riser ESD valves Xmas tree and wellhead assemblies – from / to flanged interface on Xmas tree or wellhead.For onshore facilities TR1951 apply to all piping systems contained within the facility. The facility limits shall, with respect to external interfaces for onshore plants be considered as being the plant isolation valve, i.e. the first or last valve on any pipe or pipeline that has an interface outside of the plantSee GL1951 for guidance on the design and engineering of piping systems1.2 Target group The target group for this document is personnel involved in conceptual studies, FEED studies, pre-engineering, project execution, detail design and modifications.1.3 Provision Provision is made in Management System (TR3010 “Mechanical Technology Technical Requirements and Standards”).2 TR2000 - Piping and valve material specification2.1 General TR2000 is a Piping and Valve Specification System. The basic principles of the system are to standardize requirements to components and to tailor the menu of Piping Class Sheets (PCS) to each plant´s need, i.e. process requirements. The TR2000 “Plants” includes piping and valve material specifications for Plant Categories "Operative Plants" including existing plants and realization projects, "Best Practice" library with piping class sheets (typical naming E MAS) and "Frame Agreements". For each plant, all relevant datasheets are collected in an Issue. The Issue contains a set of plant specific PCS´s, with specific revisions of all referenced datasheets i.e. MDS, VDS etc. To avoid frequent changes of a plant specific Issue, an Issue is not always updated to include the latest revision of datasheets referenced from PCS.SR-15915 - For projects in the study phase "Best Practice" library should be used as the basis for the studies. In cases where the project is mature and requires special piping classes, a plant for the project specific piping and valve specification shall be developed in the TR2000 database and will be located in Plant Category "Operative Plant". Reference is made to www.TR2000.net.SR-15916 - The TR2000 shall be developed along with material selection and process requirements to achieve a goodReference is made to section 9 below for line sizing and optimization.SR-15917 - New piping classes and Valve Data Sheets shall be generated from the TR2000 based on existing piping component articles. All adjustments and/or additional piping classes/Valve Data Sheets etc. shall be approved.SR-15868 - The development of the TR2000 must be started early in the project phase and will be a “living” document as the development of the project progresses. This includes all project development phases.2.2 Design codes SR-12659 - Design code is specified in TR2000 Piping Class sheet. ASME B31.3 shall normally be used. Other codes may be used when required and it shall then be identified in the TR2000 Piping Class sheets.2.3 The European Pressure Equipment Directive (PED) SR-12661 - The European Union Pressure Directive (PED) is mandatory for plants located within the European Economic Area (EEA). If changes in the TR2000 are proposed relative to PED, then Company shall be addressed with the objective to participate in discussion and communications in order to maintain the TR2000 technology. Contractor shall develop and present a PED strategy to Company, detailing Contractor's methods to achieve PED compliance. Each project shall be responsible for PED compliance by a Notified Body’s formal approval. Engagement of Notified Body in this process is dependent on the Contractor’s quality system and the selected quality module.SR-15918 - A general conformity assessment of use of ASME B31.3 / TR2000 under PED has been performed by two independent Norwegian Notified Bodies DNV GL and Kiwa. Discussions regarding use of ASME B31.3 as design code and materials (ASTM) are hence not any issue as long as any of these Notified Bodies are selected. Ref. PED tab in TR2000. If another Notified Body is selected for a project, the selected Notified Body has to perform an evaluation of TR2000 and use of ASME B31.3 under PED (preferable as an endorsement of DNV GL's and Kiwa's conclusions).2.4 Line sizing and material selection SR-12663 - Line sizing and material selection is a part of the development of a project’s TR2000 and shall be based on how material selection, piping class selection and process requirements affect the economical result.2.5 Piping specification in mechanical packages SR-12665 - Piping specification in mechanical packages or system modules shall be according to TR2000. However, for equipment where it is unreasonable to use this specification, the supplier may request a deviation. The deviation can only be implemented after acceptance. Deviation request shall include details enabling Company to evaluate if the alternative solution shall be included in TR2000.2.6 Valve selection SR-12667 - TR3017 Valve Selection Manual shall be used in projects. Engineering evaluation shall be performed with the objective to evaluate all affecting parameters and to achieve an optimal solution. Deviations to TR3017 may be proposed, but shall only be implemented if accepted.Table 1 Table for selection of flanges and mechanical jointsSee also section 3, “Flange pressure rating and design pressure" regarding design pressure for ASME and MSS-SP flanges.2.7 Flanges and mechanical joints (Clamp connector) SR-15919 - Flanges and/or mechanical joints are specified in each of the Piping Classes in TR2000. ASME B16.5 and ASME B 16.47 Series A (MSS-SP-44) shall generally be specified for pressure Class 150 and up to an including class 2500 Clamp connector may be specified for Class 1500 and higher up and including 12” size, see table 1.Valves are normally specified with flanged or mechanical joint connections. Piping inline equipment should be specified similarly. Deviation to this may be accepted if the equipment clearly is designed for the life time of the plant without need of disconnection, or if needed for special reasons, e g. toxic fluids. Other equipment connected to piping shall be specified with the same connection as stated in the Piping Class.2.7.1 ASME B16.5 flanges versus Compact flanges SR-12673 - ASME B16.5 (ASME B 16.47 Series A) ring joint facing shall be used as default for CL 600 to CL 2500.SR-12674 - Compact flanges should be used when the following conditions and design requirements are important for the project:• Beneficial to the stress calculation (more resistant to explosion loads).• The present design and layout will require or benefit in smaller flange dimensions.• Credited for safety (more safe than ASME B16.5 flanges) due to two sealing faces (heel and ring) and static behaviour of the flange.• The ring (gasket) is less exposed to the fluid, external environment and thereby corrosion.SR-12675 - When Compact flanges are selected they shall not be used for equipment listed below:• Spectacle blinds and spacers that are frequently used (every 6 month or more frequent)SR-12676 - The project shall standardise on one type of flange/joint (to the maximum extent). SR-14734 - Manufacture/machining shall be prequalified prior to fabrication of Compact flanges.SR-14739 - Riser components on battery limit pipeline side of ESDV shall comply with TR1098, Submarine pipeline systems.2.7.2.1 General requirements Compact flanges according to the standard ISO 27509 may be specified for pressure class 600 and higher and for pipe sizes 3” and larger.SR-16831 - Compact flange shall not be evaluated for use for pressure class below class 600 for austenitic stainless steel materials due to undesirable welding heat effects that can cause deformation on the flange.The project Piping Class will show the type of joints to be used.2.7.2.2 Compact flanges installed upstream of ESDV (riser side for offshore) SR-12681 - If flanges can be used on the riser side of a flow line, compact flanges shall be the preferred selection. For technical safety requirements see TR1055 (offshore) and TR2237 (onshore).SR-12682 - Where compact flanges are used on risers, the following additional technical requirements shall be adhered to:Special design of compact flanges outside ISO 27509 shall be verified according to ISO 10423 Annex F or qualified according to ARIS, Qualify technology for first use. Compact flange design shall be verified and accepted by technical personnel - typically discipline responsible (internal or external) having relevant competence on compact flanges. Weld neck compact flanges shall be made according to ISO 27509. The compact flanges shall be subject to individual dimensional checks. A test procedure for testing of flange after welding to pup piece or riser shall be developed and accepted. The test procedure shall as a minimum include the following requirements: The flange shall be individually pressure tested to verify and document that the sealing surfaces in both heal and ring groove are tight. The flange shall be tested with blind flange designed with a test port between flange heal and ring groove. Test no. 1 shall be performed with a IX seal ring in the compact flange ring groove with 1.5 times the design pressure to verify the flange heel sealing capability. The pressure shall be monitored and any leakage shall be measured through the blind flange test port. Test no. 2 shall be performed with a IX seal ring in the compact flange ring groove with 1.5 times the design pressure of the Piping Class in both flange bore and blind flange test port to verify the flange ring groove sealing capability. Any leakage shall be measured with a pressure gauge through the blind flange test port by monitoring any pressure decrease. Alternative test procedures may be proposed for evaluation and acceptance.In addition to the assembly requirements in ISO 27509 the following shall be added and included in a procedure that shall be developed and accepted: Perform visual inspection to verify that there are no damages or corrosion on the flange sealing surface immediately prior to flange assembly and bolt-up. For preservation, apply a layer of thin oil on flange sealing surfaces and on the IX seal ring. Apply grease on the middle section of the bolt (the part of the bolt that will be inside the flange). Theremaining part of the bolt shall be lubricated with special paste for bolt torque. Protection caps should be provided for bolt and nut protruding out from flange. Apply a wax layer on the outside of the flange wedge in order to protect bolting from environmental moist etc. The seal ring shall not be re-used if the flange connection has been opened. A procedure shall be developed if the joint has to be re-opened including the requirements listed above.3.1 Occasional variation of pressure and temperature SR-12688 - ASME B31.3 allows for the piping to be exposed to temperature and pressure over the design in periods as defined in ASME B31.3 § 302.2.4. The use of this paragraph is encouraged where significant cost and weight savings can be achieved. To ensure safe and consistent practice and to document the use for the operational phase, the use of this paragraph shall be documented and approved in deviation system; DISP. The content of the deviation request shall be as specified in 3.1.4. The two Norwegian Notified Bodies DnV and TIS have accepted the use of this paragraph under PED.Shut-in pressure of well stream when considerably higher than normal operating conditions Shut-in pressure of pumps and compressors Equalising pressure across discharge to suction pressure of compressors and pumps. When PSHH or PSH dependent on process case can be set high enough compared to normal operating condition to avoid operating limitation. In such cases design condition should be at the PSHH or PSH if considerable saving in piping material is achieved Pressure surge, e.g. water hammer, see GL1951.These are examples only and other cases may be evaluated.3.1.2 PSV set pressure SR-12693 - ASME B31.3 § 322.6.3 (b) and (c) with respect to PSV set pressure shall be included in the evaluation, also noting that note 13 in (c) of the § is met. This means that set pressure of PSV that is protecting the piping may be set at a higher pressure than the design pressure given in the piping class.3.1.3 Exposure time SR-16833 - For exposure above the design pressure, Company philosophy is that the nature of and potential for the exposure time should be evaluated and grouped within the time frames in ASME B31.3, § 302.2.4 (f) (1) and (2), based on the time being nominal time. In each case of occasional overload scenarios, fulfilments of the ASME B31.3 Chapter 302.2.4 requirements shall be documented. In most cases the nature of and potential for exposure over design will be sufficient documentation of fulfilment of code requirements. Logging of time will normally not be required. The effect of fatigue of the piping and the effect the enhanced condition may have on other connected pressure equipment, i.e. valves, fittings, vessels etc., shall be taken into account.3.1.4 Justification of piping overpressure SR-12698 - For piping systems with possible overpressure scenarios, the following minimum documentation shall be included in a deviation request.Based on process data Per cent overpressure above design (100%) ASME B31.3 § 302.2.4 Cause of overpressure Expected frequency of overpressure Expected duration and mechanisms that will limit the duration Measures to document that the ASME requirements are satisfied Cost / benefit assessment Evaluation of potential risk in case of leakage from rated components or damage to equipment. Confirmation from the suppliers that involved valves and equipment will handle the overpressure if the pressure exceeds 1,1 times the valve design pressure.There shall be an approved deviation application before it is designed for overpressure and implementation in a project. This is to ensure a uniform treatment within Company of such cases.3.2 ASME B16.5 flange pressure rating including valves and equipment flanges SR-12701 - For certain materials, Company uses higher pressure rating than tabulated in ASME B16.5. This is based on experience prior to the time the material was included in ASME B16.5, and based on evaluation and calculation according to ASME B31.3 and ASME VIII Div. 1. The Piping Classes and valves in TR2000 are specified with the rating as determined by Company. Flanges on equipment that are connected to the piping shall be according to the rating of ASME B16.5 or TR2000, whichever is the higher rating.Example of material that is used with higher pressure rating than in ASME B16.5 are 22 and 25 Cr duplex material, 6Mo and titanium.4.1 General Isolation barriers as it is handled in this chapter, is defined as an isolation barrier between a pressurised system and a part that will be needed to open for maintenance or modifications. The relevant types of isolation barrier and the conditions and limitations attached to them are described below.SR-12704 - Beyond the specific requirements given in this document and TR3017 Valve Selection Manual, design of isolation barrier philosophy with valve type shall be based on life cycle cost of installation and maintenance operations.SR-12705 - New products, which shall be used as an isolation barrier, shall be qualified for the purpose in accordance with ARIS, Qualify technology for first use.4.2 Requirements to isolation barrier practice SR-14743 - Table 2 states the isolation barrier requirements for different services and ratings. Comments are as noted below the table.1. Excluding liquefied gas (LNG or LPG) or medium at a temperature above the self-ignition temperature2. Toxic gas means that the concentration of the toxic gas can be high enough to cause permanent injury or death by breathing it in case of a leakage.3. Classification according to ASME B16.5, specific pressure limits are dependent upon temperature and material quality, but typically CL150 covers pressures up to 20 bar, CL300 covers pressures up to 50 bars and CL600 covers pressures up to 100 bars.4. For valves with dimensions up to and including 3" it is acceptable to use two block valves without bleed, with a simplified barrier test.5. E.g. equipment that can be removed and then blinded off with a blind flange, threaded plug/cap or isolated by a physical blind (Spectacle blind or spade).6. Typical liquid systems that cannot be depressurised within one hour. For barriers where the system to be opened is in an area where any liquid leakage will be collected by an open drain system with sufficient capacity, time to drain of liquid could be prolonged.7. Valid for duplicated equipment's, typical A & B trains, where maintenance normally will last for typical several weeksFigure 1 Example DI&B with two valves on left side and by single valve on right side8. For instrument connections as specified in TR2325, isolation between piping and instruments, a single valve is acceptable for CL150 through CL2500 provided that instrument equipment includes a built-in isolation valve and a bleed facility4.3 Blinding and physical disconnection/ removal of spool piece SR-12710 - Blinding and gaskets shall be of the same pressure class as the flanges to which they are fitted.4.4 Single isolation barrier by use of valves SR-12712 - A single isolation barrier is achieved by establishing a barrier that can be tested prior to use and be maintained and monitored as long as it is used as a barrier. See appendix A (example 5) for description of how a typical single barrier is arranged.4.5 Double isolation and bleed (DI&B) by use of valves SR-12714 - ”Double isolation and bleed” is achieved by establishing two independent isolation barriers that both can be tested prior to use and be maintained and monitored as long as they are used as barrier. See appendix A (examples 1 to 4) for procedure for alternative DI&B barriers.SR-12715 - DI&B can be achieved using the following two arrangements:Two block valves set in series with an interposed bleed-off valve stubbed in between the two block valves to provide a means to bleed to a safe location (see valve arrangement on left hand side below). DI&B achieve in a single valve body with a barrier on each side of the closing device (ball, gate, plug or similar, that is activated through the valve stem or in combination with spring and pressure forces), and with a bleed-off facility from the cavity. See the valve arrangement on the right hand side of Figure 1 below.barrier Downstream Upstream barrier barrier POINT TOBE ISOLATEDSR-12716 - For valves where the seat sealing surface is activated through the pressure from the media, it is important to ensure that the downstream barrier is maintained in correct position (e.g. slabs in gate valves can move with external movement or by gravity when not pressurised).4.6 Requirements for valves when used as isolation barriers SR-12718 -It shall be possible to secure the valve in the closed position, and the securing device shall be unlocked/ broken before the valve can be operated. There shall be no (cavity entrapped) pressurised hydrocarbons, toxic or dangerous medium downstream the upstream barrier (for valves <6” with a small cavity volume, deviation to this requirement could be acceptable) Any pressure activated sealing shall be kept in desired position For actuator-operated barrier valves, it shall be physically checked that the valves cannot be operated once it has been taken into use as a barrier. The actuator energy supply shall be disconnected if the valve is not secured with mechanical equipment that is significant stronger than the actuator. Barriers that are mechanically activated by stem force shall have an actuator spring return that force the valve in correct position, if not secured with mechanical equipment that is strong enough to ensure this. Barriers that are not mechanically activated by stem force shall have all springs in the actuator in the relaxed position if the valve is not secured with mechanical equipment that is significant stronger than the actuator. Any gravity induced forces shall also be considered (e.g. for reverse acting slab gate valves).SR-12719 - Table 3 gives an overview of how typical valve types can be used in a DI&B barrier. The intension of this table is to give the designer an overview of the connections needed and work required to establish a safe isolation barrier. (Handling of old valves with large leakages are not covered by this table, e.g. use of a pressurised fluid to block a leakage).barrier with 7-10barg -periodic surveillance for any increase in leakage through the bleedFigure 2 Double isolation barrier without bleed between-depressurise cavity of downstream valve -periodic surveillance for any increase in leakage through the bleed-periodic surveillance for any increase in leakage through the bleedTable 3 Minimum requirements to different valve types when used as DI&B barrierIn case of pressure increase in bleed section to above 20bar after 4 hours use as barrier, the work shall be temporary stopped, while the segment is fully depressurised to safe location and then re-pressurised with Nitrogen to 16bar. When two different valve types are used as barrier, the downstream valve type shall be ruling for these requirements. The two independent valves can be arranged together in a single body or be flanged/welded together to a double isolation and bleed arrangement. If the valve is supplied with only one DP seat, the DP seat to be downstream only to obtain DI&B.4.7 Simplified test for small bore valves SR-16848 - Instruments connected to piping systems normally have ports that can be used as bleed. For barrier valves to such instruments, introducing of an extra bleed port can cause a higher risk during normal operation than what a simplified barrier test will cause during a maintenance situation.For double isolation barriers where the valve port sizes are 3” or smaller, bleed between them can be avoided if there are ports on the instrument that can be used to performance test the barrier.The barrier procedure shall contain the following aspects:Check the downstream valve for leakage by closing it, with the upstream valve open Check the upstream valve for leakage by closing it, with the downstream valve open (to be carefully open to release pressure) Close the downstream valve Carry out required work immediately For situations where the barrier shall be kept for more than 2 hours, blind it off with equipment that’s allows possibility for re-testing.4.8 Use of stem backseat as isolation barrier Use of backseat as barrier for packing box replacement can be considered for valves with stem leakage through a gland compressed packing box, and where the leakage is stopped by setting the valve in backseat.The barrier procedure for backseat shall contain the following aspectsThe system pressure shall be stable, and shall be expected to be constant for the whole operation Documentation logs for the valve gives no indications of defective backseat or damaged stem Gas-sniffer is used during the entire work Packing box leakage is defined and that the backseat stops the leakage Packing box leakage arise again when the valve is taken out of backseat The valve is locked in backseat The valve is regularly checked to be free for leakage for minimum one hour Gland nuts are careful unfastened until the gland flange is unstressed, but both nuts shall be fully engaged to the gland bolts The valve is regularly checked to be free for leakage for minimum 5 minutes continuously With any detection of leakage, the operation shall be stopped and the gland nuts be retightened (if possible) The packing box shall be removed with approved equipment New packing box is mounted, and the gland is carefully pre-stressed The valve is carefully opened and the packing box is adjusted according to applicable procedure The valve is regularly checked to be free for leakage for minimum 5 minutes Documentation log for the valve is updated with services rendered4.9 Use of other types of isolation barriers SR-12730 - Other types of barriers, such as mechanical or hydraulically expanding plugs, ice plugs, etc. shall not be used as a primary isolation except in special cases where calculations and Safe Work Analysis (SJA) has been performed and special acceptance has been given by the responsible leader of the respective plant. Mechanical or hydraulically expanding plugs shall be qualified according to ARIS, Qualify technology for first use.6.4 Tubing as replacement for piping SR-12740 - For tubing used as replacement for piping, the following shall apply:Requirements for Piping Detail Standard are defined in TR2325.6.1 General Reference is made to TR2323 “Piping Fabrication, Installation and Testing Specification”.6.2 Code hydro-test pressure SR-12735 - The test pressure shall be derived based on the design pressure of the Piping Class, multiplied by the factor as required by the design Code.6.3 Bolt tensioning SR-12737 - Bolt tension force shall be according to TR1968. For installations and plants where the specific tables are based on the available local tools, lubrication and gaskets defined, bolt tension force and torque shall be according to TR2000 Plant Specific tables.Tubing shall not be used on pressurised HC system. All tubing used as replacement for piping shall be defined with piping line number. The tubing used shall be defined in the TR2000 piping class sheet.SR-12741 - Typical interface definition between piping and instrument related to use of tubing shall be according to TR2325 “Piping Detail Standard”.For selection of piping tubing materials reference is made to TR3032 "Field instrumentation". SR-12742 - The project specific service code list shall include applicable tubing piping classes.ASME B16.5 ASME B16.47A Compact flange Mechanical Joints <=24" 26"-60" CL150 CL300 <=24" 26"-60" CL600 <=24" 26"-60" 3"-48" CL900 <=24" 26M8" 3"-48" 1„ 1 2 „ CL1500 <=24" 3"-48" r 12" CL2500 <=12" 3"-24" CL4500—> 1"-12"Isolation barrier requirement Additional isolation barrier requirements 3) Service\Rating CL300 8) < 8) CL150 > CL600 Equipment or systems that may be disconnected for longer periods, all ratings 7 ) Segments where a barrier leakage can result in a severe incident caused by leakage of large volumes from the segment 6 ), all ratings Non-hazardous medium Single barrier Same as CL150, CL300 & CL600 Line blinds not required Flammable 1 ) or hazardous medium Single barrier with possibility to blind off 5 ), or DI&B 4 ) DI&B 4 ’ Line blinds DI&B 4 ) Liquefied gas (LNG orLPG) or medium at a temperature above the self- ignition temperature DI&B DI&B Toxic gas 2 ) (e.g. H2S)Valve type Case 2 Single valve used as DI&B barrier Case 1 Two independent valves used as DI&B barrier2,3) Floating ball, fixed seat -cannot be used as DI&B -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -low pressure performance test of downstream barrier with 7-10 barg -periodic surveillance for any increase in leakage through the bleed Floating ball, floating seat -cavity bleed required -high pressure performance test of both barriers, max pressure -periodic surveillance for any increase in leakage through the bleed -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -low pressure performance test of downstream barrier with 7-10 barg -periodic surveillance for any increase in leakage through the bleed -cannot be used as DI&B Trunnion mounted (fixed) ball, self-relief seats -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -low pressure performance test of downstreamTrunnion mounted (fixed) ball, double piston seat downstream (Note 4) -cavity bleed required -high pressure performance test of both barriers, max pressure -low pressure performance test of downstream barrier with 7-10 barg -periodic surveillance for any increase in leakage through the bleed -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -low pressure performance test of downstream barrier with 7-10 barg -periodic surveillance for any increase in leakage through the bleed -cannot be used as DI&B Non-contact ball, single seated -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -low pressure performance test of downstream barrier with 7-10 barg -periodic surveillance for any increase in leakage through the bleed Non-contact ball, double seated -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -periodic surveillance for any increase in leakage through the bleed -cavity bleed required -high pressure performance test of both barriers, max pressure downstream valve -periodic surveillance for any increase in leakage through the bleed Wedge gate -generally cannot be used as DI&B, but can be considered if it has cavity bleed -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -periodic surveillance for any increase in leakage through the bleed Slab gate, floating seat -cavity bleed required -high pressure performance test of both barriers, max pressure -periodic surveillance for any increase in leakage through the bleed -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -pressurise downstream barrier with N2,16barg -periodic surveillance for any pressure changes between the barriers, stop work if pressure below 16 barg or above 20 barg1) -cannot be used as DI&B Slab gate, fixed seat or floating seats without sealing between seat and body -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -pressurise downstream barrier with N2,16barg -periodic surveillance for any pressure changes between the barriers, stop work if pressure below 16barg or above 20barg1) Expanding gate -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -cavity bleed required -high pressure performance test of both barriers, max pressureGlobe -cannot be used as DI&B -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -low pressure performance test of downstream barrier with 0.5barg -periodic surveillance for any increase in leakage through the bleed Plug, expanding -cavity bleed required -high pressure performance test of both barriers, max pressure -periodic surveillance for any increase in leakage through the bleed -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -periodic surveillance for any increase in leakage through the bleed Plug, other -cannot be used as DI&B -bleed required between the two barriers -high pressure performance test of both barriers, max pressure -depressurise cavity of downstream valve -periodic surveillance for any increase in leakage through the bleed