API STD 603:2001 pdf download
API STD 603:2001 pdf download.Corrosion-Resistant, Bolted Bonnet Gate Valves Flanged and Butt-Welding Ends.
The stem connection shall prevent the stern from turning or disengaging (mm the gate while the valve is in service. The stern train (stem. gate. stem nut. handwheel. and handwheel nut) shall be designed to fail outside the pressure boundary in the event of the application of excessive handwheel torque to over come a locked gale. The strength of the stem (in tension) outside the pressure boundary shall not be less than the calculated theoretical) failure load based on the external thread root area and the specilied minimum ultimate tensile strength of the stem material. The strength (in tension) of the stern-to-gate connection and of all parts of the stein within the pressure boundary shall he greater than the strength at the root of the external threads.
4.6.3 Valves shall have a stem operated by a rotating stem nut mounted at the top of the yoke. The stern nut shall have a hexagonal shank, a round shank with a keyway. or another drive of equivalent strength and durability for attachment to the handwheel. For valves larger than NPS 6 in Class ISO, NPS 4 in Class 3(X) or NPS 2 in Class 6(N) the stern nut arrangement shall be designed to:
a. permit the removal of the handw heel, without allowing the stem and gate to drop into the closed position, if the hand- wheel is removed when the valve is in the open position.
b. allow the stem nut to bc replaced. with the stem secured. without affecting the pressure retaining capability of the bonnet assembly.
However, replacement under pressure is not recommended. When a threaded hushing is used to retain the stern nut, the hushing shall be retained by a weld or other suitable means to ensure that there is no movement during operation of the valve. Metal peening (staking) is not permitted.
4.6.4 The threads of the stem and stem nut shall be Acme type conforming to ASME B 1.5 or stub threads conforming to ASME HI .8 (minor modifications are permitted for either thread). The Acme thread major diameter may be less by a maximum of /I in. (1.6 mm) than the diameter of the stem that passes through the packing. On direct handwheel-operated valves, these threads shall he left-handed threads, (Clockwise rotation of the handwheel shall close the valve.)
4.6.5 Stern threads shall project outside the stem nut on a new closed valve by a distance that is at least equal to the required wear travel distance. The maximum projection distance of the stem thread shall be five times the wear travel distance for valves NPS 6 and smaller and three times the wear travel distance for valves NPS 8 and larger.
4.6.6 The stem shall have au integral conical or spherical backseat surface to seat against the bonnet backseat when the gale is fully open.
4.6.7 The stcm shall have a surface Finish Ra of 32,, in. (0.80,. In) or smoother in the area in contact with the packing.
4.8 BOLTING
4.8.1 Bonnet and yoke bolting shall be headed bolts or continuously threaded stud bolts with heavy semi-tinished hexagonal nuts conforming to the requirements of ASME B 18.2.2. When headed bolts are used they shall be limited to class 150 in sizes NPS 8 and smaller and class M) in sizes NPS 6 and smaller. Bonnet bolting for valves NPS 3/4 and smaller may utilize cap screws (see 4.2.4).
4.8.2 Gland bolting shall be headed bolts, hinged eycbolts. or studs with hexagonal nuts.
4.8.3 Bolting that is 1 inch in diameter or smaller shall have coarse (UNC) threads. Bolting larger than I inch shall be X-thread series (8 UNC). Bolt threads shall be Class 2A and nut threads Class 28 in accordance with ASME B I . I. However. studs used for gland bolting shall be secured with a Class 5 interference-lit in accordance with ASME 8 1.12.
