UL 1739-2017 pdf download – Pilot-Operated Pressure-Control Valves for Fire-Protection Service.
10 Materials 10.1 A part that bears against, rotates within, or slides on stationary parts, and that moves during valve operation, shall be either: a) Made of corrosion-resistant material; or b) Fitted with bushings, inserts, or other parts made of corrosion-resistant material at those points where freedom of motion is required. 10.2 An interior bolt or screw shall be made of bronze or other material having at least equivalent resistance to corrosion. 10.3 An internal spring shall be made of material having corrosion resistance at least equivalent to that of phosphor bronze and shall be resistant to stress corrosion. 10.4 A seat ring shall be made of brass, bronze, or a material having at least equivalent resistance to corrosion and shall be held in place by screw threads, cold swaging, or the equivalent. 11 Body-Seat Rings 11 .1 A body-seat ring shall have a smooth, machined surface capable of complying with the Seat Leakage Test specified in 20.2. 1 1 .2 A seat ring of an iron-bodied valve shall be made of a material having corrosion resistance equivalent to brass or bronze and shall be held in place by screw threads, cold swaging, or the equivalent. 12 Valve Mechanisms 12.1 An internal working part that is removed during intended maintenance shall be removable without damaging the valve. The removal shall require the use of ordinary tools only, such as pipe wrenches, flat-blade or cross-point screwdrivers, pliers, and the like.
12.5 The pilot trim line used in a pressure control valve shall not incorporate a manual shutoff valve that could affect the proper operation of the valve unless the shutoff valve has provisions to be locked in the open position. 13 Clearances 13.1 Clearances shall be provided between working parts and between working and stationary parts so that corrosion or deposits of foreign matter within an assembly will not result in impaired operation of the valve. 13.2 The clearance between a valve disc or a part attached thereto and the inside walls of an iron body casting shall not be less than 1/2 inch (12.7 mm) for every position of the disc except fully open. This clearance shall not be less than 1/4 inch (6.4 mm) for valves having bodies of bronze or equivalently corrosion-resistant material. 14 Valve Adjustment 14.1 A valve shall be provided with a means such as a fastening nut to secure the intended setting. PERFORMANCE 15 General 15.1 Representative samples of each size valve shall be subjected to the tests described in Sections 16 – 22. Additional samples of parts constructed of nonmetallic materials, such as rubber seal rings, are to be used for the Elastomeric Parts (Except Gaskets) Test, Section 17. 16 10-Day Moist Ammonia Air Stress Cracking Test 16.1 After being subjected to the conditions described in 1 6.2 – 16.4, a brass part containing more than 15 percent zinc when examined using 25X magnification shall: a) Show no evidence of cracking; or b) Comply with the Leakage Test, Section 20, and the Strength of Body Test, Section 21, if there is evidence of cracking. 16.2 Each test sample is to be subjected to the physical stresses normally imposed on or within a part as the result of assembly with other components. Such stresses are to be applied to the sample prior to and maintained during the test. Samples with threads, intended to be used for installing the product in the field, are to have the threads engaged and tightened to the torque specified in Table 16.1.