valveselect.pdf

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NIBCO INC. WORLD HEADQUARTERS 1516 MIDDLEBURY ST. ELKHART, IN 46516-4740 USA PH: 1.800.234.0227TECH SERVICES PH: 1.888.446.4226 FAX: 1.888.234.0557 INTERNATIONAL OFFICE PH: +1.574.295.3327 FAX: +1.574.295.3455

www.nibco.com

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VALVE SELECTION GUIDE BUILDING SERVICES

SelectionValves serve the purpose of controlling the fluids in building servicespiping. Valves are produced in a variety of design types and materials.Proper selection is important to ensure the most safe, efficient, cost-effective and long-lasting systems.FunctionValves are designed to perform four principal functions:

1. Starting and stopping the flow (isolation)2. Regulating (throttling) the flow3. Preventing reversal of the flow (backflow)4. Regulating or relieving the pressure of the flow

Service Considerations

1. Pressure2. Temperature3. Type of fluid

a) Liquidb) Gas; i.e., steam or airc) Dirty or abrasive (erosive)d) Corrosive

4. Flowa) On-off, throttlingb) Need to prevent flow reversalc) Concern for pressure dropd) Velocity

e) Shock5. Operating conditions

a) Condensationb) Frequency of operation

c) Speed of operationd) Accessibilitye) Overall size/space availablef) Manual on automated controlg) Need for bubble-tight shut-off

h) Insulation

Valve Design Choices1. Multi-Turn

a) Gateb) Globe/Angle-Globe

2. Quarter-Turna) Ballb) Butterfly

3. Checka) Swingb) Liftc) Spring-actuated

4. End connections

Materials1. Bronze (up to 550F at 150 psi/up to 600 psi at 150F) "-3"2. Cast Iron (up to 450F at 250 psi/up to 500 psi at 100F)

2"-24"3. Ductile Iron (up to 650F at 125 psi/up to 600 psi at 100F)

2"-12"4. Stainless Steel (up to 650F at 125 psi/up to 2000 psi at

100F) "-12"5. PVC Plastic (up to 140F at 50 psi/up to 150 psi at 100F)

"-4"

Approvals1. Manufacturers Standardization

Society (MSS)2. Fire protection (ULand FM)3. State and local codes.

Design Detail

1. Multi-Turna) Gate Valves

Positive Features1) Good choice for on-off service2) Full flow - low pressure drop3) Bidirectional4) Best choice for steam service

Disadvantages1) Not for throttling; use fully opened or fully

closed.2) Metal-to-metal seating means not best choice for

frequent operation. Bubble-tight seating should not beexpected with metal-to-metal design.

3) Difficult to actuate.

Wedge and Seat Designs1) Solid wedge best choice for all

building services. Modern foundryand machining controls enable thesolid wedge to give good performancein a broad range of services.

2) Metal solid wedge seating againstmetal seat integral to the body is the mostcommon in building service piping. Rubber-coated solid wedge (resilient wedge) hasbecome popular in fire protection andmunicipal cold water service. The resilient

wedge design offers bubble-tight seating,but is limited to 160F water service.

Stem Designs1) Rising stem-inside screw is the most

common and preferred design for bronzemulti-turn valves. In the fully open backseated position*, the stem threads areprotected from the media. Because thestem rises as the valve is opened,clearance must be provided and stemorientation should protect it from externaldamage. The stem position indicates tothe observer if the valve is opened or

closed.*Repacking while valve is pressurized is not recommended.

2) Non-rising-inside screw stems are usedin bronze and iron gate valves. While theyare more compact than rising stem valves,the stem threads are always exposed toflowing media, allowing for possibleerosion/corrosion. Open/close indicationis not provided with this design.

Gate Valve

Solid Wedge Seat

Rising Stem-Inside Screw

Non-Rising-InsideScrew Stem


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