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docuthek.com Blow-off and breather pipes or conduits

Where blow-off or breather pipes or conduits are fitted on regulators or relief valves or vent valves, adequate means shall be provided to facilitate the venting of gas from the system to a safe discharge area1).

In case breathers or blow-off pipes are gathered2), the cross section of the collector shall be suitable to evacuate simultaneously total flow rates of the exhaust sources.


The following chapters are printed with the permission of the DIN Deutsches Institut für Normung e.V. (German Institute for Standardization). For the implementation of the DIN Standard, the version with the most recent issue date is deemed authoritative. This is available from Beuth Verlag GmbH, Burggrafenstrasse 6, 10787 Berlin, Germany.


Our note on this Standard:

1) Gas escaping through openings in the equipment may lead to formation of an ignitable mixture. In order to avoid this, the openings must be provided with blow-off pipes and venting pipes ending in a safe area or the vent connections must be equipped with restrictors, provided this does not impair operation.

It must be borne in mind that gas escaping from blow-off pipes outside enclosed spaces as well may create areas with an explosive atmosphere, depending on operating and ambient conditions. Consequently, such areas must be free of all ignition sources and must be at a safe distance from doors and windows. Precautions must be taken to avoid blockage of the outlet opening of the pipes to the atmosphere and to protect against penetration of foreign bodies, such as water, dirt, etc.

The above-mentioned openings also include vent holes in diaphragms of pressure regulators and safety devices. Pipes connected to such openings must also have adequate capacity for unhindered escape of the gas and proper operation of pressure regulators and safety devices should pressure build up in the pipe.

2) Blow-off pipes and breather pipes must not be routed together with venting pipes in a manifold. Blow-off pipes for gas may not be combined with blow-off pipes for air or oxygen. If blow-off pipes, breather pipes and venting pipes are each combined in a manifold, these must be dimensioned adequately large so as not to impair the function of the equipment connected. Connection of pipes from sections of different pressure ratings must be avoided. However, if pipes from sections of different pressure ratings are connected to a manifold, the maximum possible pressure in the manifold must not exceed the maximum allowable operating pressure of the system section with the lowest pressure rating.


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