UL-842:2015 pdf free download – STANDARD FOR SAFETY Valves for Flammable Fluids.
7.5 When corrosion of a valve stem results in damage to a packing or seal material and results in
leakage, or binding of the assembly, the stem shall be of corrosion resistant material or be provided with
a corrosion resistant coating or treatment.
7.6 A valve stem shall not be capable of being completely withdrawn from the valve by reverse rotation. Threads of a valve stem shall not enter a stuffing box recess.
7.7 A stem shall be of sufficient length to permit repacking the stuffing box without requiring the part to be dismantled.
8 Diaphragms
8.1 A valve in which a flexible diaphragm, bellows, or similar construction constitutes the only fluid seal shall have the atmospheric side of the diaphragm or bellows enclosed in a casing intended to limit external leakage in the event of diaphragm or bellows rupture, or shall have provision for connection of a vent pipe or tubing intended to be routed to the outdoors or other location.
8.2 To comply with 8.1, a valve shall not leak under conditions of ruptured diaphragm or bellows from an unthreaded vent opening or around any pins, stems, or linkage passing through the housing in excess of the following rate when the valve is tested to its maximum rated pressure:
a) 1 cubic foot (28 dm3) per hour of a 0.64 specific gravity gas for a valve for use only with fuel gases having specific gravities less than 1.0;
b) 0.5 cubic foot (14 dm3) per hour of a 1.53 specific gravity gas for a valve for use with LP-Gas;
c) 1000 cubic centimeters per hour of water for a valve for use with gasoline, kerosene, and Nos. 1 and 2 fuel oil;
d) 2000 cubic centimeters per hour of the lightest grade of fuel oil heavier than No. 2 for which a valve is to be used.
8.3 A diaphragm or bellows shall be protected from damage.
8.4 Metal parts coming in contact with a diaphragm shall have no sharp edges, burrs, projections, or the like which cause chafing or abrasion of the diaphragm.
9 Springs
9.1 A spring shall be guided and arranged to minimize binding, buckling, or other interference with its free movement. When required, ends of a spring shall be closed and squared.
10 Operating Mechanisms
10.1 Screws and nuts used to attach operating parts to movable members shall be upset or otherwise locked to prevent loosening.
10.2 A manually-operated mechanism of a valve shall provide free movement of all parts.
PERFORMANCE
11 General
11.1 Except as otherwise indicated, representative samples of each type of valve are to be subjected to the tests described in these requirements. Additional samples of parts constructed of nonmetallic materials, such as seal materials and valve seat discs, shall be provided as required for physical and chemical tests.
11.2 When a series of valves is to be investigated in which the bodies differ in size only, three representative samples are to be chosen to include the largest, smallest, and one intermediate size.