No offence taken.
When it comes to SIL rating 2 in series does mean you can reduce the SIL level required of the individual valve/actuator so I think it is a good idea.
I believe that people get really hung up with the SIL rating of the actual valves (It is after all an instrument safety...
Thanks Ashereng.
I don't think it would be a good idea for me to ask my I&C resource, as my job is to specify the valves - I don't have a problem with doing this.
The question was put to get other peoples opinions on why they thought ball valves were better for gas pipelines & I have found all...
Thanks for all the comments.
From what I have gleaned from the above there is nothing cut & dried, it is still a question of personal choice / experience and how long you think resiliant seats will last compared to conventional HF seats.
The reason the question was asked in the first place was...
Thanks for all the replies there have been some interesting points.
Apart from the pigging aspect why not use a butterfly valve although they were not mentioned in my original post I would imagine they are a lot cheaper & initially as leak tight as a ball & there would be no need for cavity...
I agree with the effort used by ops. but, I forgot to mention that the site is mostly automated so gates can use smaller actuators and take up less room.
Good gate valve manufacturers are offering resiliant seats which I assume will be as leak tight as ball?
Is there nothing on the side of the valve which gives a manufacturers Fig. number or tag number & then ask the manufacturer.
Take some general external measurements and check with manufacturers catalogue this will usually tell you whether you have FB or RB - but it does not mean that full bore...
This would depend on what code you are working to & whether any Federal or state rules override the ASME code.
B31-4 & API RP1110 the min. time for the Hydro. test is 4hours after stabilisation and pump is isolated.
I would agree with all of above.
Installing butterfly valves in pump suction lines is an absolute no no due to turbulence and pressure drop across valve - to reduce pressure drop in line reduce number of bends & reduce number of valves, try and automate the gate valves & get rid of b/fly valves.
I don't know whether this is a simple Q or not.
Why use ball valves on Gas pipelines instead of gate & or globe valves, am I missing something?
I am new to Gas pipelines having mostly worked in petrochem & powerstations where gate & globe valves are the standard for isolation because they are...
API 608 & ASME B16.34 for design - press. temp ratings
ASME B16.10 for Dimensional standard
API 598 & 607 for Inspection & testing inc. Fire safe
When you get to larger sizes / higher press. then there are no Dimensional std. in B16.34.
As above post people get confused about class of leakage.
Control valves because there primary function is to control are often not leak tight - the class rating is so that clients can specify a control valve which has also got a tight shut off capability.
This is not the same as Isolation...
Gate valves are often used on petrochem plants as primary isolation valves in case of emergency as, they can be relied on to close when required even after being left for long periods in the open position.
Good info on the web sites thanks
I have also found info on cooper cameron valve website which directly links temp. and valve class.
I believe they have a good reputation.
Thanks for the help & web sites - I will look thru' them.
I thought it would not be as straight forward as press. temp curves.
The reason for the post was so I could clarify manufacturer's data as they seem to differ & I need to order ball valves up to 36" and press/temp ratings of 4350psi at...
