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What do I need to specify in engineering a motor operated valves?

Marine Engineering professionals, Please share your valuable experience with me by replying the following questions related to Propeller Cavitation: Q1: At what RPM (Revolution Per Minute) does cavitation start at the tip of the propellers? Q2: What is the diameter of the propellers in Q1? Q3...

I do not have experience with subsea control valve applications. Please check with The Valve Doctors, CCI. (Tel:1-949-858-1877)

TreeEng Regarding the equations that you posted: Cv ~ 38*A*Cd A=cross-sectional area please see Crane Technical Publication 410. In Crane, you will find that Cv = 29.9 d^2 /sqrt(K), where (pi)d^2/4 = A, i.e. the effective cross-sectional area. Therefore Cv/A = 38/sqrt(K). Hence, 1/sqrt(K)...

For water flow, recommended velocity at trim exit of control valve is 100 feet/sec., i.e. an exit trim fluid kinetic energy of 70 psi. See P. 438, Practical Guide for Measurement and Control, Control Valves, ed. Borden, 1998, ISA.

jsummerfield (John), I believe equation (4) in Fisher's article (How to Size Liquid Control Valves) is inaccurate. For an inlet reducer, K1 = 0.5[1-(d^2)/(D^2)] should be correct, i.e. without squaring the term in the outer bracket. Same inaccuracy was found in ISA S75.01. I have informed...

TD2K is correct.

People, Please check the amount of energy released by cavitation. The US Patent Office has rejected Copes Vulcan (Raven trim)to patent former CCI technology. Itchtudder is correct. US Patent Office reexamination document 6161584 refers. 4carats

Cornejoi, I advise you to buy the following book: Principles and Practice of Automatic Process Control, by Carios A. Smith and Armando B. Corripio. Important: get the 1st edition (not the 2nd edition). In the 1st edition, it shows derivation of "Installed Characteristics" from...

I know Valtek (now FlowServe) make a control valve with pressure and temperature sensors in it for measuring flow, except I do not know how good it is.

You also need to consider the hydraulics and the overall effect on the control system when you change the inherent flow charteristic of a control valve. In parallel valves operation, it is even more important to check if the slope of flow vs lift match between parallel valves. You can change the...

I agree with Snarayan.

Check Appendix A, Crane Technical Paper 410. There are formulas relating Cv and Equivalents of Resistance Coefficient (i.e. Loss Coefficient) K for geometry of flow through a circular hole. I call the above equation, eq.(2), i.e. Cv/area = f(K) You started with a known Cv. I call this...

ANSI/ISA S75.01 Standard: Flow Equations for Sizing Control Valves" does not recognize the Cv defined by Fisher. The "Cv method", a well accepted method by all valve manufacturers, was first introduced in 1944 by Masoneillan International, Inc. [Ref: Corripio, Priniciples and...

I believe your question refers to small (< 1/8&quot;) poppet pneumatic pilot operated valve for on-off service. I have never seen a process modulating control valve operating this fast pneumatically; I believe the stroke is very small. I suggest you talk to the control valve manufacturers...

Saxon, Thank you. The two big valves were upsized in 1984 for 850,000 lbm/hr of steam flow each. [The energy from one valve is big enough to supply electricity for a city of population of 50,000 people.] The upsize was done independent of the small valve, i.e. the small valve has been left...

TD2k Thank you. The positioner linkage broke several times due to vibrations. The lantern rings (stainless steel cylinders 2 inches tall X 1 inch diameter) within the valve --- one disappeared; one was worn down to 1/2&quot; inches due to vibration. Vibrations affected control. Downstream...

Hi TD2K, By resolution I mean for every unit change in stroke, what is the change in downstream transient pressure. I am talking about valves of size 12 inches and bigger. The hydraulic forces of the fluid (and enthalpy change) are so huge that the valve(s) are vibrating. What resolution can...

Thank you, TD2K. Each of the three valves has their own controller. I advised my Company to change the trim of the big valves except I have no experience in how characterization of the trim is done. I know how much flow overlap is needed; I need to know how to translate the desired flow vs lift...

This is not the answer to my own question above. Our Company has a serious problem in Steam Letdown Valves. To capture the problem in more details: Three Steam Letdown Valves, A, B & C, are arragned in parallel, each has an upstream pressure of 900 psig, and an outlet pressure of 600 psig. The...