BS 7278:1990 pdf free.British Standard Specification for Gas tightness of equipment for gas weldingand allied processes.
BS 7278 This British Standard specifies the maximum externalleakage rates which are acceptable for equipment used forwelding, cutting and allied processes. lt applies to individual components which are used in the gassupply to a blowpipe from the connecting point of the hose(outlet of the cylinder valve or connecting point to a gas supplyplant). lt does not apply to gas supply plants.
The titles of the publications referred to in this standardare listed on the inside back cover.
For the purposes of this British Standard, the followingdefinition applies. external gas leakage: Undesired escape of gas to theatmosphere.The maximum permissible external leakage rates which arespecified in this British Standard are total leakage ratesfor a complete component including inlet connections.These rates are given in cubic centimetres per hour1 of the gasfor which the equipment was designed, corrected to standardconditions2), measured at roorn temperature.
NOTE – Connections that are necessary only for the test are excluded.
Devices to be used with helium shall be tested with helium anddevices to be used with hydrogen shall be tested with hydrogenor helium.Devices to be used with other gases shall be tested with dry oil-free air or nitrogen.
lf the test is carried out with a gas other than the gas for whichthe equipment is designed,appropriate corrections shall bemade (see annnex A).Regulators shail be tested at pressures pand p2 as definedin BS 5741.Type tests other devices shall be tested at the following pressures: a)maximum working pressure as given by the manufacturer; b)10 % of the maximum working pressure.
All devices shall be tested at that pressure (of the two pressuresspecified in 6.2.1) which gave the most unfavourable resultsduring the type tests.NOTE – The leakage rate for individual devices will be incorporateddirectly in the relevant standards for that device when they are revised.7.1Regulators
Regulators shall not have a total leakage rate greater than10 cm3/h.BS 7278 pdf download.