4。11Drain, Vent, and Sealant Valves

Drain and vent block valves may be provided。 When provided, the drain and block valves shall have a rated pressure not less than the valve on which they are installed and be suitable for blow-down operation。 Block and check valves fitted to sealant injection lines shall be rated for the greater of the piping valve rated pressure and the injection pressure defined in 4。10。

4。12Handwheels and Wrenches—Levers

Wrenches for valves shall either be of an integral design or consist of a head that fits on the stem and is designed to take an extended handle。

The head design shall allow permanent attachment of the extended section if specified by the purchaser。

The maximum force required at the handwheel or wrench to apply the breakaway torque or thrust shall not exceed 80 lbf (360 N)。

Wrenches that are of integral design (not loose) shall not be longer than twice the face-to-face or end-to-end dimension。

Handwheel diameter(s) shall not exceed the 40 in。 (1065 mm)。 Spokes shall not extend beyond the perimeter of the handwheel。

Direction of closing shall be clockwise。

4。13Locking Provision

Valves may be supplied with a provision for locking。

When specified, the locking feature for check valves shall be designed to lock the valve in the open position only。

Locking feature for other types of valves shall be designed to lock the valve in the open and/or closed position。

4。14Position of the Obturator

Except for check valves, the position of the obturator shall not be altered by dynamic forces of the passing flow or in the case of screw operated gate valves by forces generated from internal pressure。

4。15Position Indicators

Valves fitted with manual or powered actuators shall be furnished with a visible indicator to show the open and the closed position of the obturator。

For plug and ball valves, the wrench and/or the position indicator shall be in line with the pipe when the valve is open and transverse when the valve is closed。 The design shall be such that the component(s) of the indicator and/or wrench cannot be assembled to falsely indicate the valve position。

Valves without position stops shall have provision for the verification of open and closed alignment with the operator/actuator removed。

4。16Travel Stops

Valves that do not require mechanical force to affect a seal shall be provided with travel stops on the valve and/or operator and they shall locate the position of the obturator in the open and closed position。

The travel stops shall not affect the sealing capability of the valve。

4。17Actuator, Operators, and Stem Extensions

4。17。1General

The output of an actuator shall not exceed the stress limits of the valve drive train permitted by 4。20。2。

Actuator sizing and mounting kits shall be in accordance with API 6DX。

4。17。2Misalignment

Misalignment or improper assembly of components shall be prevented by suitable means, such as a dowel pin or fitting bolt, which ensures the correct location of manual or powered operators and stem extension assemblies。

4。17。3Sealing

Operators, stem extensions, and their interfaces shall be sealed to prevent ingress of external contaminants and moisture。

4。17。4Overpressure Protection

Operators and stem extension assemblies shall be provided with a means of preventing pressure buildup in the mechanism resulting from stem or bonnet seal leakage。

4。17。5Protection of Extended Stems and Shafts in

Belowground Service

Extended stems and shafts in belowground service shall be protected by an extension casing (housing)。

4。18Lifting