Installation hazard assessment

The user and system designer are in full possession of all the relevant available facts regarding the gas and the installation. Any assumptions made should be passed to the fan manufac­turer and identified as such. The user must assess the risks at­tached to all the possible hazards and decide what, if any, leak­age is acceptable. Gas properties reviewed during the assessment should include:

Auto ignition point

The temperature about which a substance wilt start to burn without an ignition source being necessary.

Flash point

The lowest temperature at which a gas will burn if an ignition source is present.

Atmospheric boiling point

The temperature at which any liquid will boil at atmospheric pressure. 101.325 kPa.

Vapour specific gravity

Specific gravity is the ratio of a vapour’s density to air at standard conditions, atmospheric pressure. 101.325 kPa.

The nature of the hazards will also dictate the type of duct con­nections to be used. Spigot, flat-face, flanged, raised-face flanged, ring-type joints. Process upset conditions must be con­sidered as part of the assessment. Upset conditions which last for more than one or two hours may have a significant impact on pump and ancillary equipment selection.

The physical location of the fan, indoor or outdoor, will decide the behaviour of the leakage once outside the fan. Will any vapour cloud quickly disperse on a breeze which always blows over the un-manned site or will a manned enclosed fan house gradually build up a dangerous concentration of gas? Only the user can assess these questions and specify the necessary precautions.

It is the responsibility of the user to define exactly what the fan is intended to do. It is the responsibility of the fan manufacturer to supply equipment to meet the required performance.

Posted in Fans Ventilation A Practical Guide


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