EXEMPTION: | You are exempt from the requirement not to install the shut off valve between the safety relief valve and the container or systems in the following situations: |
1. A three-way valve installed under two safety relief valves, each with: | |
a. The required rate of discharge; and | |
b. Installed to allow either of the safety relief valves to be closed off but not at the same time. | |
2. Two separate relief valves are installed with individual shut off valves. | |
The two shut off valve stems must be mechanically interconnected to allow the full required flow of one safety relief valve at all times. | |
3. When a safety relief valve manifold that allows: | |
a. One valve of two or more to be closed off; and | |
b. The remaining valve or valves will provide not less than the rate of discharge shown on the manifold nameplate. |
If you have: | Then make sure they: | |
Filling connections | Are fitted with one of the following: | |
1. | A combination back-pressure check valve and excess flow valve. | |
2. | One double or 2 single back-pressure check valves. | |
3. | A positive shut off valve used with either an: | |
a. | Internal back-pressure check valve; or | |
b. | Internal excess flow valve. | |
A fully enclosed guard | Have properly vented safety relief valves. | |
Fittings | Are protected from physical damage by a rigid guard designed: | |
1. | To withstand static loading in any direction equal to twice the weight of the container and lading. | |
2. | With a safety factor of 4 based on the maximum strength of the material used. | |
Liquid withdrawal lines installed in the bottom of the container | Have connections, including the hose that are not lower than the lowest horizontal edge of the truck axle. | |
Columnar-type gauges | 1. | Are shielded against the direct rays of the sun. |
2. | Are equipped with all of the following: | |
a. | Shut off valves having metallic hand-wheels; | |
b. | Excess flow valves; | |
c. | Extra heavy glass that is adequately protected with a metal housing applied by the gauge manufacturer. | |
Hydrostatic relief valves | Are installed between each pair of valves in the liquid ammonia piping or hose. |