Flow Control - Jan 2012
think tank quiz corner Upstream Straight Run Obstructions by David W Spitzer W hich of the following can be located in the upstream straight run of an orifice plate primary element installation A Elbow B Tee C Fully Open Full Port Ball Valve D Fully Open Reduced Port Ball Valve E Throttling Valve F None of the Above Commentary The performance of most flowmeters can be adversely affected by a distorted velocity profile at the flowmeter inlet One method to improve the velocity profile at the inlet of the flowmeter is to install straight run upstream that allows velocity profile distortions to dissipate prior to entering the flowmeter To achieve this end the upstream straight run should not contain any obstructions to flow Elbows tees and throttling valves present an obstruction to the fluid flow and can distort the velocity profile Because the objective of straight run is the opposite reduce velocity profile distortion elbows tees and throttling valves should not be located in the upstream straight run Answers A B and E are not correct Although designed without turns or bends fully open reducedport ball valves do present a small obstruction to flow and should not be located in the upstream straight run Answer D is not correct A fully open full port ball valve should create minimal if any distortion of the velocity profile if proper gaskets are used if the valve is properly aligned in the pipe and if the valve is maintained in its fully open position In a practical sense this valve could be located within the upstream straight run but it would be better if it were located upstream of the straight run However this valve would not be acceptable in the straight run when the flowmeter installation standard requires the upstream straight run to have a machined finish Depending on application Answer C or F might be correct Additional Complicating Factors Fully open ball valves could be pragmatically used in the upstream straight run such as when space is limited or when extensive piping modifications are necessary to install sufficient straight run Full port ball valves are preferred but reduced port valves could be used in a pinch FC David W Spitzer is a regular contributor to Flow Control with more than 35 years of experience in specifying building installing startup troubleshooting and teaching process control instrumentation Mr Spitzer has written over 10 books and 150 technical articles about instrumentation and process control including the popular Consumer Guide series that compares flowmeters by supplier Mr Spitzer is a principal in Spitzer and Boyes LLC offering engineering expert witness development marketing and distribution consulting for manufacturing and automation companies He can be reached at 845 623 1830 www spitzerandboyes com november SOLUTION Spray Optimization A F L U I D P R O P E R T I E S E O I A Y R S I S Y L A N A E Z I S P O R D I A G A A I R A T O M I Z I N G E Z O G U L E F E E I N O I T A Z I M O T A O E N G I I S I T N T A S P R A Y A N G L A I G U L I O M R O F I N U E L A T E T O F E C T R F R E E P A S S A G E L R A P O S S R D A R T S R F O P L E G E N R N R E S A I I U T I K F A C F N T Y S O I M S E T A T P A T A R S R A T Z S I A S I Y V I S A R P S E S C Y A R O T R I S T A R O S Z T Y T A M A P O L A U N L S Y P U A A I A A S E R Y T D R C L N E P A R C P P M R R N P A C A T P U Y L A A A S P S E O W P S R A E L M D N L R P S P I M A E T O S P F H I U R L T O A Y T A L U P R A L S K O F P F A I T T P N G F P P N F F F R E T A R W O L F E I O C S L D I R E C T P R E S S U R E L D S P E Z I I I L R T L A O W I D I C I E R A T E Circle 27 or Request Info Instantly at www FlowControlNetwork com 48 January 2012 Flow Control
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