Valve isolation tank
Valve isolation tank
(OP)
I have to purchase a valve to isolate a 30'' outlet line located at the bottom of a storage tank of Bunker 150 000 Barels.
I will connect a future line to this valve in few months. However, the tank will already be in operation.
Should I installed a standard gate valve, a parallel slide gate valve or a knife gate valve ?
I think a gate valve could do the jobs but will be more expensive.
I don't know ''parallel slide gate valve" but I have seen that type of valve installed on similar application.
Knife gate valve : my feeling is that it's leaks.
Thanks for your help,
Vlaidmir99
I will connect a future line to this valve in few months. However, the tank will already be in operation.
Should I installed a standard gate valve, a parallel slide gate valve or a knife gate valve ?
I think a gate valve could do the jobs but will be more expensive.
I don't know ''parallel slide gate valve" but I have seen that type of valve installed on similar application.
Knife gate valve : my feeling is that it's leaks.
Thanks for your help,
Vlaidmir99





RE: Valve isolation tank
Maybe a gate valve but they do leak. Parallel slide: expensive and the packing will rpobably leak. Knife-gates are for slurries like paper stock, but not for tight isolation.
I would look first at a butterfly valve. You may need a fire-safe valve. THese are available with a zero-leak resilient primary seat and a metal secondary seat for post-fire shutoff.
RE: Valve isolation tank
RE: Valve isolation tank
If the line were 12" or less in size then I would suggest using a sleeved plug valve. This valve can be reseated in line without disassembly. Xomox is a good manufacturer of plug valves.
Gate Valves, Knife Gate Valves leak.
RE: Valve isolation tank
You may also find the links to the relevant websites in thread408-64692: butterfly valve and thread408-126483: Discussion on triple offset valve within this Forum).
If you go with knife gate valves intead, try visiting http://www.knifegate.com/ for instance...
Hope this helps, 'NGL
RE: Valve isolation tank
Considering that this is normally low temperature, is a large valve, and does not cycle very often, your lowest cost option would be a double-offset butterfly. A triple-offset will be more expensive and takes a lot more torque to operate so not necessary unless you need to benefits of this type of valve. As JimCasey suggests, use a polymer seated version which has a metal back-up for fire safe. This is common in double-offset type.
bcd
RE: Valve isolation tank
We finally purchased a std gate valve for my application. I was looking for a parallel slide gate valve as provided by hattersley heaton (wafer type, slimline catalogue) but the delivery was too long.
I know it will leak as it is not a class 6 valve but our criteria was to meet API 598 low and high closure test.
Vladimir99