Valve World Americas September 2022 Sample | Page 7

Variable Name Unit Minimum Normal Maximum Volumetric Flow Rate Liquid ( QI ) gpm ( US ) 2000.000 500.000 700.000 Inlet Pressure ( P1 ) psig 1078.000 1070.000 1068.000 Outlet Pressure ( P2 ) psig 20.000 25.000 30.000 Inlet Temperature ( T1 ) deg F 250.0000 260.0000 270.0000 SG 0.946 0.941 0.937 Dynamic Viscosity ( Mu ) cP 0.232 0.221 0.211 Vapor Pressure ( Pv ) psia 29.843 35.445 41.874 Sizing Coefficent ( Cv ) 6.085 15.295 21.482 % Open 22 49 67 Valve Lpa ( LpAe1m ) dB ( A ) 69 73 74

Figure 3 : Typical basic inputs and outputs of the valve sizing .

This is a business trend that is increasingly seen in the modern instrumentation and valve business .

One could ask – why such a history detour in the article about valves ? It is here for the simple reason that without understanding the causes of today ’ s challenges one cannot affectively address these challenges and find both business and technical solutions . Industry has to face new workforce skills , short- and long- term disruption to the traditional supply chains including engineering and , as a core solution , technical competency and knowledge retention . Valve sizing and selection is one of the areas where this knowledge acquisition and retention is equally critical for operators , vendors , and engineering .

Valve Sizing and Selection

Anyone who has worked with valves can typically recite the key criteria for reliable valve selection ; valve type , size , noise level , presence of cavitation , and corrosion protection . Unfortunately other , less common criteria are often overlooked amidst the time , cost , and resource pressures of the project .

There is no question today , in the age of global high-speed internet coverage , that the availability of automation tools is essential for every profession and task . One of the biggest challenges associated with automation tools is ensuring that the correct data is used . The first criteria that should not be overlooked for valve selection , is therefore the application process and piping data as well as the type , geometry , and configuration of the valve . Without accurate information , the output of the sizing tool is unreliable and sometimes misleading , defying the whole purpose of the sizing and selection process .

The second criteria to be sure to consider is the cavitation index . If a vendor does not publish cavitation index , finding the valve that will match the application can be very difficult . Other parameters , though often hard to obtain and evaluate , are just as important . Take a pressure loss , for example . The effect of the 1.5 Mw power loss on a 20 ” valve may be negligible , but the same pressure loss dissipating kinetic energy of the fluid on a 3 ” valve may have a very destructive effect . Not only will it elevate noise , which is one of the key and easy to observe indicators , but also increasing vibration downstream , potentially leading to a failure .

Determining the Correct Valve

So how does an end user select the right valve ? The answer is simple : evaluate all the parameters that are affecting the valve , the behavior and controllability of the flow , and the reliability of its operation in the context of where the application will be used .

Knowledge and expertise are not the only ingredients for success in valve sizing . Knowledge of where and how the application will be used is essential . For example , it is often assumed that if a valve fails , it can be replaced with the same valve . As factors like a flow and upstream pressure can change during the lifespan of the failed valve , it is best not to assume that the specifications for the original valve will be accurate for the replacement valve . It is essential that the process and piping data given to the valve supplier is up-to-date and reviewed by the process or unit engineer . Figure 1 highlights an example of a small progressive decrease in the pressure drop of the minimum flow from 80 bar to 75 , and finally to 70 . It also shows how the change in the flow behavior from choking , to severe , to incipient cavitation , drastically affects the valve .

Figure 4 : Placement of the operating points - minimal , normal , and maximum flow – on the installed valve flow capacity .

Variable Name Units Minimum Normal Maximum

WARNINGS

Flow is choked

Flow is choked

Flow is choked

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Figure 5 : Examples of the information and warning messages produced by the valve sizing tools . www . valve-world-americas . net • September 2022 | Valve World Americas 7