re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
(OP)
Hi,
I would like find info about manual gate valves for isolation purposes. The gate valve spec. is Class 300 lbs SS body BW Sch40S Man Operated. The design conditions are T=200F and P=180 psig, in water. The Cv required is 3100. I came across with a similar spec that uses a trim characteristic of "Double Seat". My knowledge of valves is limited. Can someone help to understand what is "Double seat"?
In addition, can this trim characteristic achieve the Cv in a manual gate valve?
Thank you for your help in advance.
Patrick
I would like find info about manual gate valves for isolation purposes. The gate valve spec. is Class 300 lbs SS body BW Sch40S Man Operated. The design conditions are T=200F and P=180 psig, in water. The Cv required is 3100. I came across with a similar spec that uses a trim characteristic of "Double Seat". My knowledge of valves is limited. Can someone help to understand what is "Double seat"?
In addition, can this trim characteristic achieve the Cv in a manual gate valve?
Thank you for your help in advance.
Patrick





RE: re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
Or, am I way off course?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
Knife-gate valves tend to be single-seat but certainly not used in Nuclear applications-usually slurry such as pulp.
here is a link so you can take a look at the construction of a gate valve:
http://ww
Frequently Cv for gate valves is not even published because they are NOT for throttling. However, it would be highly unlikely for a 10" Gate valve to have a Cv that is not greater than 3100. As Asher said:essentially straight pipe.
Gate valves have metal-to-metal seats and it takes a huge specific loading to get them to shut off tightly. Basically it is necessary to re-coin the seat each time. Hence the wedge. Other handy associated devices for gate valves are the hammer-blow handwheel, and the large maintenance ape with the long cheater bar.
Review MSS SP 61 for seat leakage and testing procedures.
RE: re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
/* VALVE SIZE AND Cv=GPM/PSI^0.5 /* ENTER Cv ON DEFINE VALVE LINES
/* 1" = 48
/* 1.5" = 108
/* 2" = 192
/* 3" = 432
/* 4" = 768
/* 6" = 1728
/* 8" = 3072
/* 10" = 4800
/* 12" = 6912
/* 14" = 9408
/* 16" = 12288
/* 18" = 15552
/* 20" = 19200
/* 24" = 27648
/* 30" = 43200
/* 36" = 62208
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RE: re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
RE: re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
You table reminds me of the scaling rule of Cv vs valve size for a geometrically similar family of valves:
Cv=KD^2
D^2 is the valve size, squared.
K is a Constant, in this case: 48
so for your 1" valve Cv=48, for the 10" valve: 4800. Pretty close!
For globe valves, the K is usually pretty close to 14.
RE: re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte
Going the Big Inch!![[worm] worm](https://www.tipmaster.com/images/worm.gif)
http://virtualpipeline.spaces.msn.com
RE: re: 10" - 16" Manual Gate Valves "Double Seat" Trim Characte