TABLE OF CONTENTS Safety and relief valves must be the direct spring-loaded type, and for pressure ranges noted below the code [1] requires the following:
| Set Pressure | Maximum Spring Reset Referenced to Set Pressure [*] |
|---|---|
| ?250 psig | 10% |
| ?250 psig | 5% |
| [*]Marked on value |
The set pressure tolerances of pressure-relief valves are not to exceed 2psi for pressures up to and including 70psig and 3% for pressures above 70 psig. Indirect operation of safety valves, for example, by pilot valve, is not acceptable unless the primary unloading valve will automatically open and will operate fully in accordance with design relieving capacity conditions if some essential part of the pilot or auxiliary device should fail [1].
The pilot valve is a self-actuated pressure-relief valve that controls the main valve opening.
Rupture disks must have a specified bursting pressure at a specified temperature. There must be complete identification of the metallurgy (if metal) or other properties if graphite or plastic, and the disk must be guaranteed by the manufacturer to burst within 5% of the specified bursting pressure at the rated temperature.
The connection nozzle holding the disk must have a net cross-sectional area no less than that required for the design rated conditions of the disk.
The certification of disk performance is to be based on actual bursting tests of two or more disks from a lot of the same material of the same size as the disk to be sold...
