Test procedures of high velocity vents are as follow –
(1) The testing shall be capable of producing the required flow rate. Suitable test rigs should be used , Other test rigs may be used provided equivalent tests are achieved.
(2) A flow condition test shall be carried out with high velocity vents using compressed air or gas at agreed flow rates.
The following characteristics shall be recorded :-
- The flow rate, where air in a gas either than cargo vapours with which the vent is to be achieved shall be corrected to reflect the vapour density of such cargoes.
- The pressure before the vent opens. The pressure in the tank on which the device is located shall not rises at rates greater than 0.01 newton’s per square milimeter per minute.
- The pressure at which the vent opens.
- The pressure at which the vent closes ad
- The efflux velocity measured at the outlet.
(3) The following fire safety tests shall be conducted using a mixture of gasoline vapour and air which produces the most easily ignitable mixture at the point of ignition.
This mixture shall be ignited with the aid of a permanent pilot flame at the outlet:
(a) Flash-back tests shall be carried out with the vent in the upright positions and then included at 10 to vertical .For some vent designed further tests with greater inclinations of the vent may be required.’
In each of these tests the flow shall be reduced until the vent closes ant the flame is extinguished and each test shall e carried out at least 50 times. The influx side of combined valves shall be tested in accordance with the requirements of this schedule with the vaccum valve held open.
(b)An endurance burning test as prescribed in above paragraph of this schedule shall be carried out. In this test the main flame shall be extinguished and, with the pilot light on, small quantites of the most easily ignitable mixture shall be allowed to escape for a period of 10 minutes during which tie flashback shall not occur. For this test the soft seals or seats shall be removed.