Main Factors of Valve Selection Function and Piping System 
        
      
	
				
		
			
	
	
	
		
	
| Function and service considerations | 
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| Selection | 
| Valves serve the purpose of controlling the fuids in building services piping.Nalves are produced in avariety of design types and materials. | 
| Proper selection is important to ensure the most efficient,cost-effective and long-lasting systems. | 
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| Function | 
| Valves are designed to perform four principal functions: | 
| 1.Starting and stopping the flow | 
| 2.Regulating (throttling) the flow | 
| 3. Preventing reversal of the flow | 
| 4.Regulating or relieving the pressure of the flow | 
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| Service Considerations | 
| 1. Pressure | 
| 2.Temperature | 
| 3. Type of fluid | 
|  a) Liquid | 
|  b)Gas; i.e., steam or air | 
|  c) Dirty or abrasive (erosive) | 
|  d) Corrosive | 
| 4. Flow | 
|  a) On-off throttling | 
|  b)Need to prevent flow reversal | 
|  c) Concern for pressure dropd) velocity | 
| 5. Operating conditions | 
|  a) Condensation | 
|  b)Frequency of operation | 
|  c)Accessibility | 
|  d) Overall sizelspace available | 
|  e) Manual or automated control | 
|  f) Need for bubble-tight shut-off |