5 replies to this topic

[Sherif Morsi]

Hi All,

 

I was reading an archived discussion about the use of ball vs. butterfly valves. This is a subject for a running project I am working on now.

We are installing new seawater fine filters for the water injection system. Triple Offset butterfly valves are an option on the table along with the normal gate valves. Line sizes range from 12" to 18".

 

Valves will be used for isolation: Filter Inlet Isolation, Outlet Filter Isolation and Backwash Line Isolation (activated by DP).

I tried to find some more literature about single, double and triple offset butterfly valves along with some schematics but couldn't find much. Would you please guide to where I can find such information?

Also, which valve should we use, Ball or Gate or Butterfly? Also, What's the difference between single, double and triple offset butterfly valves?

Appreciate your input

Regards,
Sherif

[Zauberberg]

Here is some basic information about single/double/triple offset butterfly valves, and the differences in quality of sealing: http://www.flowserve... literature.pdf

 

Butterfly valves are generally acceptable in water applications, and nowadays they can be designed with tightness up to ANSI B16.104 Class V or even higher. They come with the smallest footprint and usually the lowest cost.

 

It is very hard to give you a definite recommendation with regards to valve selection - this will largely depend on other details of the application (presence of solids, required tightness, pressure differential across the valve in shutoff conditions etc.). For example, if they are intended to isolate the equipment with 300 bar on the other side of a closed valve, they wouldn't be my first choice. A floating ball valve would be preferred then. If the pressure differential is in the range of a few bars and you don't expect too much sand and dirt, a butterfly valve may be the best option.

[Sherif Morsi]

Hi, I am not sure what ANSI B16.104 Class V is. Is this #150, #300 or higher?

 

The valves will be installed within the seawater system. The seawater carries some solids, mostly fine solids. The system pressure is around 5 bar and the temperature is ambient. There shouldn't be a considerable pressure drop across the valves.

 

Would gate valves be considered for high pressure isolation? Would gate and/or butterfly be considered for solids as well?

 

Thanks,

Sherif

[gegio1960]

Sherif,

ANSI B16.104 Classes measure the tightness/leakage of a valve (as Dejan already wrote....).

Nothing to do with rating (#150 etc).

Tightness/leakage is classified from I to VI (if I remember well): as the "Roman" figure increases (I, II, III, IV, V, VI stay for 1, 2, 3, 4, 5, 6) also the tightness of the valve increases (or the leakage decreases).

Each class is associated to a measure of the allowed leakage.

The easiest reference is http://en.wikipedia....i/Valve_leakage. You can find tons of literature with google

When you see the acronym "TSO" (ie Tight Shut Off) near a valve symbol on a P&ID, it means the valve is either class V or class VI.

For instance, TSO valves are used on the fuel gas line to burners: for safety reasons, you can't tolerate fuel losses when the valve is closed.

Another typical application of TSO valves is for shutdown/isolation.

 

Butterfly valves are often used for your kind of application.

The attached brochure is only an example.

 

Good luck!

Attached Files

•  BVS - E.pdf   676.46KB   51 downloads

Edited by gegio1960, 25 February 2015 - 12:50 AM.

[Zauberberg]

Butterfly valve seems like a good candidate for the above mentioned service conditions. Depending on the leakage tolerance, single or double offset valve should be more than sufficient.

[Sherif Morsi]

Thanks guys, appreciate your support