(A) Every container used in systems covered
by rules
901:5-3-12
to
901:5-3-14
of the Administrative Code shall be provided with one or more safety relief
valves of the spring-loaded or equivalent type. The discharge from safety
relief valves shall be vented away from the container, upward and unobstructed
to the atmosphere. All safety relief valve discharge openings shall have
suitable raincaps that will allow free discharge of the vapor and prevent the
entrance of water. Provision shall be made for draining condensate which may
accumulate. The rate of the discharge shall be in accordance with the
provisions of'Appendix A, ANSI K 61.1 -1972;"
(B) Container safety relief valves shall be
set to start-to-discharge as follows, with relations to the design pressure of
the container:
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(C)
Safety relief devices used in systems covered by rules
901:5-3-12
to
901:5-3-14
of the Administrative Code shall be constructed to discharge at not less than
the rates required in paragraph (A) before the pressure is in excess of one
hundred twenty per cent of the maximum permitted start-to-discharge pressure
setting of the device;
(D) Safety
relief valves shall be so arranged that the possibility of tampering will be
minimized. If the pressure setting adjustment is external, the relief valves
shall be provided with means for sealing the adjustment;
(E) Shut-off valves shall not be installed
between the safety relief valves and the containers or systems described in
rules
901:5-3-12
to
901:5-3-14
of the Administrative Code except that a shut-off valve may be used where the
arrangement of this valve is such as always to afford required capacity flow
through the relief valves.
Note: The above exception is made to cover such cases as a
threeway valve installed under two safety relief valves, each of which has the
required rate of discharge and is so installed as to allow either of the safety
valves to be closed off, but does not allow both safety valves to be closed off
at the same time. Another exception to this may be where two separate relief
valves are installed with individual shut-off valves. In this case, the two
shut-off valve stems shall be mechanically interconnected in a manner which
will allow full required flow of one safety relief valve at all times. Still
another exception is a safety relief valve manifold which allows one valve of
two, three, four or more to be closed off and the remaining valve or valves
will provide not less than the rate of discharge shown on the manifold
nameplate.
(F) Safety
relief valves shall have unrestricted access to the vapor space of the
container;
(G) Each safety relief
valve used with systems described in rules
901:5-3-12
to
901:5-3-14
of the Administrative Code shall be plainly and permanently marked as follows:
(1) With the letters "AA" or the symbol
"NH3";
(2)
The pressure in pounds per square inch gage (psig) at which the valve is set to
start-to-discharge;
(3) The rate
of discharge of the valve in cubic feet per minute of air at sixty degrees
Fahrenheit and atmospheric pressure ( 14.7 psia);
(4) The manufacturer's name or trademark and
catalog number and date of manufacture shall be required on all newly installed
relief valves. For example, a safety relief valve marked "AA-250-4200" (air)
means that this valve is suitable for use on an anhydrous ammonia container;
that it is set to start-to-discharge at two hundred fifty psig; and that its
rate of discharge is four thousand two hundred cubic feet per minute of air;
(H) The flow capacity
of the safety relief valve shall not be restricted by any connection to it on
either the upstream or downstream side;
(I) The manufacturer or supplier of a safety
relief valve manifold shall publish complete data showing the flow rating
through the combined assembly of the manifold with safety relief valves
installed. The manifold flow rating shall be determined by testing the manifold
with all but one valve discharging. If one or more openings have restrictions
not present in the remaining openings, the restricted opening or openings or
those having the lowest flow shall be used to establish the flow rate marked on
the manifold nameplate. The marking shall be similar to that required in
paragraph (G) for individual valves;
(J) A hydrostatic relief valve shall be
installed between each pair of shut-off valves in the liquid ammonia piping or
hose where liquid may be trapped so as to relieve into the atmosphere at a safe
location, or shut-off valves with internal relief shall be used;
(K) Discharge from safety relief devices
shall not terminate in or beneath any building.
