Types of Valves
Valves and valve construction to be suitable for the pressure, temperature, and fluid quality of the service in which they are to be used. All valves to be in accordance with applicable British Standards. Minimum test pressure for all valves to be 1.5 times maximum system design pressure unless noted otherwise. Test Certificate shall be submitted for all critical isolator valves. All valves used shall be suitable to operate for continuous temperature fluctuation from 5 deg C to 35 deg C without any leakages. Butterfly valves are suitable for dead end service and constructed of high quality industrial design. Use valve from factory having ISO-9002 quality system.
Table of content in this article
Gate Valve
Gate valves shall be fitted with rising stem of dezincification resistant brass. 50mm and smaller valve with rising stem, screwed bonnet, inside screw and wedge gate with screwed ends. 65mm and longer valves with rising stem, bolted bonnet, outside screw and yokes, wedge, iron body with flanged end.
Globe Valve
All globe valves 2” and below shall be of the screwed bronze body type with internal spindle. All globe valves 2½” to 3” shall be of the flanged bronze body type with internal spindle. Notwithstanding the above, all globe valves in the plant room shall be of external spindle type.
Swing type to use for low pressure general services: 50mm and smaller with screw bonnet, screwed end; 65mm and larger with bolted bonnet, flanged end. Valves to have renewable bronze seat and disc.
Silent Type to sue on pumps with cycling control and larger than 50mm discharge. Valves to have cast iron body with bronze or stainless steel trim and to be of center guide type, with flanged end.
Provide wafer type check valves for use in pipe 600mm diameter and larger. Check valves to be water type with steel body and disc flanged ends.
All ball valves shall be supplied and fitted complete with back-nuts ball float and arm. Ball floats may be of soldered copper or brass or alternatively stainless steel. They shall generally comply with B.S. 1212 standards.
Use for stop and isolation in water systems up to 40 deg. C and pipe sizes 65mm and larger.
Butterfly valves to have ductile iron full lug body, 316 stainless steel stem with bronze bushings and aluminium bronze disc.
The stem journals will be a multiple seal design providing for completely independent seals. The stem disc assembly will be such that the need for pins, screws or bolts is not required. Positive stem retention to be provided to permit removable of handle or actuator while under full operating pressure. The valves seats to consist of replaceable resilient elastomer. Manuals butterfly valves to size 100mm to be supplied with multi-position handles; size 150mm and over to be supplied with enclosed worm gear operator. Valve body to be full-lug pattern to comply with and be compatible with flanges of appropriate pressure rating. Use locally made butterfly valves with sufficient pressure rating for the system requirements.
Control valves shall be supplied and fitted where shown on the drawings and where regarded essential for proper balancing and water flow control. They shall be of the globe pattern and equal percentage type, screwed gunmetal for sizes up to and including 50 mm dia. Valves 65 mm and above shall be of the flanged cast iron type. For copper pipe work the relevant detail specified earlier for isolating valves shall apply.
Balancing valves shall be of bronze construction, rated for the working pressure of the system.
Balancing valves shall be used to regulate the flow rate of a circuit, terminal unit or zone. Each balancing value shall be provided with test plugs or matching station to facilitate the connecting of a differential pressure meter to measure pressure drop across the valve in determining the flow rate.
The balancing valve shall have an indexing pointer and calibrated memory stop to indicate the degree of closure of the precision machined orifice.
Each balancing valve is to be constructed with internal 0-ring seals to prevent leakage around the rotating element. The valve shall be provided with drainage facility. A suitable electronic microprocessor test kit shall be provided. The set shall be complete with al necessary hoses, shut-off and vent valves, gauge, base plate and carrying case. Reading range shall cover the maximum flow of the system.
Balancing valve connected to the chilled water line shall be insulated with performed polyurethane sections bonded to ‘Zincanneal’ metal sheaths, which shall be held together with spring loaded clips or locks. In addition, the balancing valves shall be provided with extended pressure tapping stems exceeding the insulation depth.
Execution
All valves, cocks etc. shall be suitable for the working and test pressure of the system concerned. Valve flanges shall be in accordance with the B.S. Tables as specified for their respective service pipe work.
Valves shall be fitted in accessible positions for operation and repair. The connection between each valve and the adjacent equipment shall be made wither with a union or a flange for ease of dismantling.
Valve spindles shall be adequately lubricated with graphite, and all glands shall be freshly packed before installation. Where possible, all valves supplied and fitted shall be of the same manufacture.
All valves, cocks etc. for water or other services shall comply to the requirements of the Local Water Authorities.