3.7 Design considerations for nonreturn devices
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3.7 Design considerations for nonreturn devices

  3.7.1 The material used in the construction of the nonreturn devices should be resistant to fire and to the corrosive attack from acids formed by the gas. Alternatively low carbon steel protected by a rubber lining or coated with glass fibre epoxy resin or equivalent material may be used. Particular attention should be paid to the gas inlet pipe to the water seal.

  3.7.2 The deck water seal should present a resistance to backflow of not less than the pressure setting of the pressure/vacuum breaking device on the inert gas distribution system and should be so designed as to prevent the backflow of gases under any foreseeable operating conditions.

  3.7.3 The water in the deck seal should be maintained by a regulating flow of clean water through the deck seal reservoir.

  3.7.4 Sight glasses and inspection openings should be provided on the deck seal to permit satisfactory observation of the water level during its operation and to facilitate a thorough survey. The sight glasses should be reinforced to withstand impact.

  3.7.5 Any drains from the nonreturn devices should incorporate a water seal in accordance with 3.15.4 and should comply generally with 3.16.


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