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 stem from turning or disengaging from the gate while the valve is in service. The stem 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 stern (in tension) owside 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 be 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 lop 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 150. NPS 4 in Class M)0 or NPS 2 in Class 600 the stem nut arrangement shall he designed to:
a. permit the removal of the handwhecl, without allowing the stem and gate to drop into the closed position. if the hand- wheel is removed when the valve is in ihe open position.
h. allow the stem nut to be 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 bushing is used to retain the stem nut, the bushing shall he 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 stein and stem nut shall be Acme type conforming to ASMF. B 1.5 or stub threads conforming to ASME Bl.X (minor modifications are permitted for either thread). The Acme thread major diameter may be less by a maximum of 1/16 in. (1.6 mm) than the diameter of the stem that passes through the packing. On direct handwbeel-operated valves, these threads shall be 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 i’he stem shall have an integral conical or spherical backseat surface to seat against the bonnet backseat when the gate is fully open.