2 replies to this topic

[mr19667]

All

 

I am a Process Engineer working on the topsides design of a FPSO project.  We have a Heating Medium (HM) system.  This is a pressurised, closed loop system.  The HM is a TEG / Fresh Water mixture.  HM supply temperature (to consumers) = 140ºC, HM return temperature (from consumers) = 90ºC.

 

My previous project experience with such a system is that Gate valves should be selected for manual isolation valves in this service.  However, I cannot recall the technical reason for avoiding other types, such as ball, for HM service.  We also may have shutdown valves in this service and we have sown these as being gate types, but a query has been raised as to whether ball would be acceptable. 

 

I would greatly appreciate any input to this, as I am sure Gate is the right selection and that ball should be avoided in this service - I just cannot remember why!  Thanks.

 

M

[Art Montemayor]

I would not use gate valves for this service.  I would use 100% ball valves instead.

 

Gates do not seal as effectively as the correct ball valve soft seat.  Gates were used a lot when there were no economically available ball valves (about 50 years ago).  Times have changed; ball valves are now produced in abundance and are more economical than gates - with less maintenance and more ease of operation.

 

Depending on your application, you might require that a "weep" (or vent) hole be drilled in the downstream side of the ball.  This is to avoid any entrapment of fluid in the ball cavity when the valve is in the shut off position.   This is usually a special requirement and should be specified in your specifications to your valve vendors.

[ankur2061]

M,

 

I have successfully used piston valves in "Heat Transfer Fluid" (HTF) applications with temperatures as high as 280-290 deg C. Uniklinger has a very popular range of piston valves from 1/2" to 8". Refer the link below:

 

http://www.uniklinge...q=piston-valves

 

Regards,

Ankur.