Evaluation of steam turbine 1

[MKhademi]

Hello,
I am now busy with the evaluation of a steam turbine in the refinery project. The question that I have is that Client asked DUPLICATE Trip/Throttle valves. I would like to know what this type of valve is or if somebody can send me more information/schematic about this type of valve.

Thanks
Mohammad

 

[chicopee]

check this site: Valves Throttle Trip Valves - Schutte & Koerting at

http://www.s-k.com/pages/pro_09_02.html

 

[MKhademi]

Thanks Chicopee. I visited the web site. However what I was looking for is the Duplicate type of T/T valves or the advantages. Is the Duplicate T/T/ valves represent a quantity? Do you have any schematic of duplicate type valves or pros-cons of this type of T/T/ valves?
Thanks

 

[racookpe1978]

Are you really sure of the terms you have used: Depending on turbine type and manufacturer (GE, Siemens, Westinghouse, etc) and fossil or HRSG-GT or nuclear plant) the valves get all sorts of different names for a valve that is in basically the same position serving the same purpose. Reheat Stop Valve -> Intercept Valve -> Throttle Valve -> Governor Valve is one sequence, but they may be also often in one, two or three different castings.
The valve series may be in two parallel runs, or (for the newer HRSG-GT steam turbines) be only one set.

Talk to YOUR client, talk to the potential turbine suppliers.

 

[byrdj]

I am not familiar with the phrasing "DUPLICATE Trip/Throttle valves".

For steam turbine control and protection the practice is to used two steam valves in series, one is used with the primary governor to provide control of speed and load. some of the names I have heard this valve called is throttle, governor, control or intercept.
the second is used with the emergency governor to provide safety in the event the primary governor and its valve fail. some of the names I have heard this valve called is trip or stop. While this valve original purpose was emergency fast closure, it has been incorperated into providing some control throttling of steam flow also.

while I said two in series, there could be multiple of these two due to quanity of steam and piping arrangements. they can also be in various configurations as pure series or grouped in header.

one design catch phrase I like when discussion the use of the primary and emergency valve for steam turbine control and protection is these valves be "seperate and diverse". that is the emergency valve and its control do not share any dependant features with the primary valve and its control

Is it possible the desire is to have DUAL valve inlets, thus a left trip & throttle valves and a right trip & throttle valves

 

[JJPellin]

When I read duplicate trip valves, I am thinking of two trip valves in parallel. This arrangement can be used so that a full stroke test can be performed with the unit on-line. If a system needs to be rated a SIL 3 or 4 to address process safety risk, a full stroke test may be required. For a process that only shuts down once every 5 or 6 years, this would require dual trip valves. We don't have any systems with this set-up. But, I have heard of this arrangement at other facilities.

Johnny Pellin

 

[MKhademi]

Dear All,
Thanks for all the input with regard to my question. Actually the wording "DUPLICATE" is specified in API Data sheet. In page 6 of API 61S data sheet, there are 3 choices for T/T/ valves. One of them is DUPLICATE type. That's why I raised this question. I think Johnny response is more close to the meaning of DUPLICATE.

Thanks again for the support

 

[chicopee]

In some cases words are taken out of context and there is no way to understand their meanings unless the entire publication is presented which seems to be the case with your OP.

 

[byrdj]

I didn't work industrial size units so the I am not familiar with the API standards. finding the data sheet on line, it refers to the standard section which defines the DUPLICATE as using two 100% in parallel so that online full closure testing can be performed if the unit is not routinely removed from service.

I highlighted the part of standby valve being closed as the use of multiple stop valves was used by utility size units, but both were open during operation