6 replies to this topic

[shahidulislam48]

Hi,

 

I am working on some data sheets of ON/OFF valves. In those data sheets I am having confusion about the mentioned process data.

I have attached a drawing about the arrangement of valves in PID.

 Drawing1.pdf   87.86KB   21 downloads

 

In the drawing there 2 possible arrangements according to the pipe class specification.

 

For Figure-1, the data sheet of ON/OFF valve contains the process data of inlet N2.

 

While for Figure-2, the data sheet of ON/OFF valve contains the process data of process line instead of inlet N2 (Both are different: process line-liquid, N2-gas).

 

But the purpose of ON/OFF for both cases are same (flow of N2 in the process line). 

 

All these variations (observed from the PID's) are due to the change from Pipe Class Specification: SS14 to SS10 or vice versa.

 

Usually we provide inlet data for sizing a valve for which it would really be operated.

 

Is this how process data are selected according to the pipe class specification for valve sizing?

Or are there some other factors that have to be considered other than inlet data?

 

Would be very grateful for getting any help.

 

Many Thanks

Shahidul

[shan]

I do not see any difference between SS10 and SS14.  They have the same pressure rating 150#, the same temperature range -29 to 427 deg C, the same material 304/304L SS, and the same allowance 0.00 in.

[vigneshdk]

Hi,

 

I am working on some data sheets of ON/OFF valves. In those data sheets I am having confusion about the mentioned process data.

I have attached a drawing about the arrangement of valves in PID.

Drawing1.pdf

 

In the drawing there 2 possible arrangements according to the pipe class specification.

 

For Figure-1, the data sheet of ON/OFF valve contains the process data of inlet N2.

 

While for Figure-2, the data sheet of ON/OFF valve contains the process data of process line instead of inlet N2 (Both are different: process line-liquid, N2-gas).

 

But the purpose of ON/OFF for both cases are same (flow of N2 in the process line). 

 

All these variations (observed from the PID's) are due to the change from Pipe Class Specification: SS14 to SS10 or vice versa.

 

Usually we provide inlet data for sizing a valve for which it would really be operated.

 

Is this how process data are selected according to the pipe class specification for valve sizing?

Or are there some other factors that have to be considered other than inlet data?

 

Would be very grateful for getting any help.

 

Many Thanks

Shahidul

Hello Shahidul,

Other data that would be helpful for for on-off valve design are 

 

Line Size/Sch.

Valve Size and Rating

Operating Temp.

Operating Pressure

Leakage Class

Design Pressure

Design Temp.

 

BODY MATERIAL

TRIM MATERIAL

GLAND PACKING

GASKET

 

Applicable Pipe Specs. - already covered above

 

ACTUATION ON AIR & POWER FAILURE

 

BOLTING MATERIAL

 

thanks and regards

Vignesh

[ankur2061]

I do not see any difference between SS10 and SS14.  They have the same pressure rating 150#, the same temperature range -29 to 427 deg C, the same material 304/304L SS, and the same allowance 0.00 in.

Shahidul,

 

Shan is right the sketch you have attached shows both SS10 and SS14 to have same specifications and hence it is of no help. If you want to understand about how process engineers are supposed to provide pipe specification breaks on P&IDs refer the attachment in the link below ( post #7):

 

https://www.cheresou...3151#entry23151

 

Regards,

Ankur.

[shahidulislam48]

Thanks Sir Ankur for your valuable reply.

 

It really helped me to understand how pipe spec break work and why.

 

I want to focus on your provided doc on point 10.4.

 

The pipe spec breaks at inlet of check valve. The block valve or shut off valve, after check valve, remains in the corrosive region.

But the valve is intended to pass the fluid of no-corrosive medium to the fluid of corrosive medium.

If I want to size the block or shut off valve, which fluid process data should I use?

Is it the process data of fluid of non-corrosive region or the process data of fluid from corrosive region downstream of valve?

Both, corrosive and non-corrosive region, have different process conditions.

 

Regards.

Shahidul

[ankur2061]

Shahidul,

 

The terminology you use "size the block valve" is not correct. Sizing has nothing to do with locating pipe specification breaks. Sizing is related to size of pipe and valves which in turn is related to flow rate and pressure drop. The attachment in the link provides guidelines for pipe specification breaks for various scenarios.

 

The attachment provides guidelines only. Guidelines also mean recommendations based on previous experience by designers and operators. However, some designers and operators may provide guidelines which match with their own experience and different from what is given in the attachment

 

10.4 in the attachment clearly recommends how to provide a pipe specification break for 2 cases: 1) check valve upstream of block or control valve and 2) check valve downstream of block or control valve. The sketch provided is based on the 1st case and for the 2nd case the description is simple enough for any engineer to make a sketch.

 

Regards,

Ankur.

[shahidulislam48]

Thank you Sir Ankur for your clarification.