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Pre P.E.D. and EN 13445 Safety Design and Use CodeCrack Detection by Eddy Current

Hydro-pneumatic Accumulator / Damper Safety Design and Use Code

1) The units should be capable of losing the energy they store by virtue of the gas within them prior to reaching destruct pressure. The incorporation of a Gas Burst Disc, our designation G.B.D. at the end of the Part Nbr., is one method of accomplishing this.

2) The units must be manufactured in such a way that both the tactile and close visual inspection can be made without difficulty at any place within the units, this enables stress corrosion and pitting to be detected when units are re-pressure tested annually or as appropriate.

3) The units shall not have less than 3:1 gas vent pressure to design pressure ratio, so that potential energy storage capability is lost at a lesser pressure than final failure pressure.

4) Units shall not have less than a 4:1 safety factor, i.e. burst pressure to design pressure, except when specifically required to be in accordance with A.S.M.E. B31.3a (pipe fittings), BS5500 or others.

5) Design pressure shall not be less than 10% above maximum working pressure, to allow for the normal inconsistencies of system pressure relief valves.

6) There shall be an allowance for corrosion to 10% of wall thickness, or 3mm if required by user under A.S.M.E. Code for Unfired Pressure Vessels.

7) Allowance shall be made in the design calculations for any stress raisers, example screw thread closures, or any that could be caused by scratching of the bore of the unit, possibly resulting from malfunction of sliding parts, example pistons without bearing pads.

8) Units shall be type tested to destruction, and 1% or one off per batch, made from the same material tested in the event of any engineering change.

9) The work/shop order number shall be recorded on the material analysis and physical properties certificate of the material used in the construction.

10) The units shall be designed in such a way that it is impossible to begin to disassemble them until the pressure has been vented from within them.

11) The comlete accumulator/damper including all bladder/diaphragm/sealing members assembly shall be pressurized to 1-1/2 times working pressure before dispatch/shipment.

12) They shall be made from sufficiently ductile material to enable the result of any over pressurization to a dangerous level to result in a measurable retained deformation after they have been depressurized.

13) Any unit of a welded construction shall be pressurized to twice it’s working pressure where not specifically prohibited by Code and shall be de-rated by 30% of it’s calculated maximum working pressure for any cyclic duty exceeding 1,000 p.a.

14) Accumulators/dampers must be designed to retain above safety factors in the event of gas over pressurization, e.g. due to a local fire.

15) Every accumulator/damper must be used with a pressure relief valve so positioned as to make it impossible to isolate the accumulator/damper from the said relief valve.

16) A bleed valve shall be so positioned in relation to the accumulator, its non isolatable relief valve, and its isolation valve, that it is impossible for the bleed valve to be isolated from any pressure remaining within the accumulator so that in the event of the bleed valve being opened it cannot fail to empty any remaining pressurized fluid from the accumulator.

Gauge port reads actual pressure that vessel sees. Liquid Dynamics PF/IN/PL units with Type 11 base or end-closure designation comply with this configuration. System port to isolator. Vent or bleed to tank port cannot inadvertently be isolated from vessel. Relief port cannot be isolated from pressure vessel. Pre P.E.D. and EN 13445 Safety Design and Use Code