THE PIPING VALVE TYPE

Primary isolation valves shall be shown on the P&ID and identified in accordance with valve identification number. Isolation valves shall be provided for all instrument connections, isolation of equipment that can be serviced when bypassed, multiple (spare) pump installations, etc.

The valve type shall be in accordance with each specific piping material class specification no. Valves description will as given in the valves specification no.  All valves shall be furnished with manual operators unless specified otherwise.

Gear Operators, as furnished by the valve manufacturer, shall be provided for large valves which satisfy both of the following conditions:

Class 150 rating	10” size and larger
Class 300 rating	8” size and larger
Class 600 & 900 rating	6” size and larger
Class 1500 & 2500 rating	4” size and larger

Gear operators shall be sized such that its output torque is at least 1.5 times the maximum required operating torque of the valve proper and shall be suitable for operation in a tropical environment.  The gear ratio shall be maximum 1:60 for valves NPS 8 and smaller or maximum 1:120 for valve NPS 10 and larger.  Gear operators shall be self locking and be provided with a position indicator.

All valves shall be capable of being locked in the open or closed position with a positive position locking device other than chain.

Block valves shall in general be ball valves of fire safe design in accordance with API 607/API 6FA or equivalent and a copy of the certification shall be provided. Butterfly valves may be used in cooling water services. Globe valves will be used when throttling is required.

Valves shall be provided with pressure equalizing bypasses when high differential pressure exists across the closed valve. Valves for which bypasses are to be furnished and the size and type of bypass valve will be shown on the applicable flow diagram.

All 2” size and larger valves shall have flanged ends. 1½” and smaller size valves shall have flanged or socket weld ends.

Check valves will be provided for all lines tying into common headers, or to prevent back flow.

Flanged end valves which are described as outside screw and yoke (OS&Y) in the valve classification tables shall be provided with stem protectors.

Globe, ball, check, and slab-type gate valves shall be field repairable. Balls, seals and seats shall be replaceable without welding or cutting.

Valve dimensions shall be identical to the dimensions specified in ASME B16.10, Face-to Face and End-to-End Dimensions of Ferrous Valves.  Face-to-face dimensions shall be long patterns.

All valves except check valves shall be capable of sealing with design pressure applied from either end of the valve.

Unless otherwise specified, valves shall be suitable for oil, water, and gas service throughout the temperature range of the pressure class.

Double seated valves capable of sealing simultaneously against pressure differential from the bonnet section to the adjacent pipe in both directions shall be equipped with self relieving seals.  Valves ANSI Class 900 and above shall have ring joint faced flanges in accordance with ASME B16.20 Ring-Joint Gaskets and Grooves for Steel Pipe Flanges unless otherwise indicated.

Vent and drain valves shall comply with the requirements of the valve classification tables and shall be adequate for the pressure and temperature limits indicated on the material and service classification data sheets.

Valve pressure-class ratings shall be in accordance with ASME 16.5.

For testing of valves, API standard 598, Valve Inspection and Test, or API specification 6D, Pipeline Valves, shall be used as a basis.

Unless otherwise specified on the piping material classification data sheets, gate valves shall be outside screw and yoke (OS&Y) with a rising stem, a bolted bonnet, a bolted packing gland, and a solid wedge gate.

If resilient seat inserts are used, the inserts shall be capable of withstanding the maximum temperature encountered in the service application.  Teflon or reinforced Teflon seat insert is preferred.

Valve seats and seals in service ASME Class 900 rating and above shall be specified explosive decompression resistant.

In general reduced bore isolation valves shall be used in all except the following circumstances:

a.     Manifold valves.

b.    Piggable lines.

c.     Pump suctions.

d.    On drain lines subject to potential blockage.

e.     Where the bore velocity would cause unacceptable pressure loss, noise, erosion, or exceed supplied specified limits for corrosion inhibitor film stability

The valve stem shall not be retained by the packing gland.  A shouldered stem with bottom entry is preferred.

The sealing characteristics of ball valves shall not be impaired by rapid temperature changes or in throttling application.

The following restrictions apply to ball valves installed by socket welding or seal welding:

a.     Installation of ball valves by socket welding, seal welding and stress relieving shall not damage the valve seats.

b.    For all socket weld valves disassembly during the installation will be required.

Check valves other than the check valves listed in the piping material classification data sheets may be required for certain service conditions as given below.

Piping Sizes	Check Valves
2 Inches and smaller	Lift type (ball, piston or disc)
3 Inches and larger	Spring actuated, double flapper type

a.     In services with fluids moving at high velocities or with pulsating vapour flows, piston check valves shall be used.

b.    In severe service applications, non-slam check valves with hydraulic (or another type) damping devices shall be used. Lines 8 inches and larger in services that do not require non-slam devices may use spring-actuated double-flapper type check valves.

c.    Centrifugal pump discharge check valves shall be of either the lift disc; balanced tilting-disc or spring actuated double-flapper type

Check valves shall be provided with drains on the downstream side of the check if required for safe operation and maintenance.

Wafer type check valves may be used as an option to flanged swing check valves in ANSI Class 600 and lower.  Wafer check valves shall be designed to API Std 594, Wafer and Wafer-Lug Check Valves.

Butterfly valves shall be limited to water and air service.  Wafer lug and wafer drop-in type butterfly valves shall normally be used.  Butterfly valves shall be designed to API Std 609, Lug and Wafer Type Butterfly Valves.