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"How can I select a valve when the Cv value varies with the pressure variation across the valve" Simple, you select a control valve. The control valve will open or close to respond to a change in signal from the control room (or manually) to control the downstream pressure, by means of...

Supersonic flow cannot occur in a "standard" piping configuration, the valve itself would need to act as though it were a convergent divergent nozzel in order for supersonic flow to occur and he downstream pipework would need to be expanding downstream of the valve. This can in theory occur...

You need to use Lame's (with an accent) method for calculating cylinder wall thicknesses and then apply a corrosion allowance of 10% of the min wall thickness. This looks at the Yield and UTS of the material and relates against the diameter of the part of the valve you are looking at. Generally...

I agree with gerhardl..... This is too difficult to say. It depends on the customer, the application, the pressure class, where the defect is, how big it is in terms of surface area but also in terms of the depth of the defect. If the defect is ever more than 1/4 wall thickness then it should...

Ok Sendel I think i know where you are going.. Basically a valve can be deemed non-operable by Shell, if they for example specify a valve with a design temperature below -20Deg C, however they state that the valve will not meet these low temperature conditions and thus is not required to...

Sorry also forgot to add.... That all of the above is at the purchasers discretion! So if they want the valve deemed operable then you're going to have to do offer it! Regards

Sendel You may have opened "a can of worms" with this question. Basically, the Shell Specification 77/200 covers valves in service between -20 deg c and -196Deg C and specifies these as "operable" valves. Valves with operating temps between 0 and -20 Deg c are deemed non operable. This is...

Hi Guys I am trying to put together a spreadsheet, whereby a volumetric flow rate can be input, along with the properties of the fluid (IE Molecular Weight, Compressibilty and Specific Heat Ratio) and the process conditions (IE Temperature and Pressure), then this can be converted into mass...

Yalkamer, i have not heard of zikesch, Sorry! Schroeder i have heard of, they however specialise in valves for pump recirculation and are automatic. For Steam valves, i would go with a company with a proven track record in the field and depending on the type of valve you require (Control...

Hi Guys I am trying to put together a spreadsheet, whereby a volumetric flow rate can be input, along with the properties of the fluid (IE Molecular Weight, Compressibilty and Specific Heat Ratio) and the process conditions (IE Temperature and Pressure), then this can be converted into mass...

The purpose of a 2 stage pressure regulator depends on the valve manufacturer and the size of the valve. In this case the flow will be choked, however the use of multiple stages is not to prevent choked flow, but either (as stated, depending on the valve and pipe size) to reduce noise and...

Forgive the formatting, can't do anything about that i'm afraid Where NSTR =( 0.02 x FL^2 x Cv / 1.17 x XFZP1^1.5 x d x d0 ) x (( 1 / (P1 - Pv ))^0.57) This is the equation found in equation 12. FL is the valve pressure recovery factor. d = valve nominal bore diamater do = diameter of the...

I am currently looking into some noise calcs for control valves with the latest edition published by the IEC (60534-8-4) however i have come across something slightly confusing and am wondering if anyone can shed some light on the problem. The problem is that the calculation for Nstr (Corrected...

I can't say for certain, but i would say that if the valves was designed suitable for those pressures and temperatures then it will work on continuous service. However if there are process conditions that may cause damage to the valve, these may not be suitable for continuos duty (I.e high...

Micalbrch - you say that Stellite is harder, but seemingly thr figures say otherwise, can you elaborate more on this? Cheers!

I am quite interested in this myself. Kolterising seemingly increases the hardness and (i assume) the erosion resistance of the Steel and judging by the figures provided on the site, it will have a higher HRc than Stellite. Reading between the lines i would suggest that kolsterising increases...

Thanks Latexman and Davefitz! really appreciate your help, i've got it now! Cheers

I am having problems calcualting the outlet velocity of Steam across a valve and am looking for help. The valve is 24" ANSI 600# (With a body bore of 22") my process conditions are causing some what of a problem to em and are giving very high outlet velocities, but these do not take into...

ValveGuru... in a few words you are incorrect! "unival,severen,introl and KOSO" are NOT affiliated! Unival is SEVERN Unival which is part of the Severn Glocon Group. KOSO Kent Introl is a seperate company to Severn Glocon and in fact one of their major competitors! As i said Koso's disc...

It is widely though that CCI developed the first disc stack design trim, however many other companies have improved this design since the Drag trim, Valtek's tigertooth although seemingly good is often overspeced and requires larger body capacities in order to "fit in". I was not aware that...