Shutdown Valves

If you want help here you will need to give us more information.

• What country is this plant located in?
  
• What kind of plant are these shut down valves in?
• What services (commodity) is in this line?
• What size are these valves?
• What kind of valves are these (Gate, Ball, Butterfly, Plug, etc.)?
  
• How often are these valves operated?
• Are these valves normal manual shut-down valves? or
• Are these valves identified on the P&IDs as "ESD" valves and fitted with some form of (electric or pneumatic) operators?
• Why do you care if they are if they are full port or reduced port?
  

Cause the information you provide is not sufficient, let me give you an example for reference.

In chemical process plant, the on-off valve type is specified by 'piping specification', which means you must follow the valve specification required by the engineering document 'piping specification, say, full or reduced bore, floating or trunnion ball, body material, packing material, fire-safe, etc.

Otherwise, if you are the person to make 'piping specification', that will be another question. General speaking, reduced bore is cheaper than full bore since less material used, but can not be used in piping-pig application.

For partial stroke, it is helpful for the valve for SIS system to keep the reliability of the system.

The I.D. of the reduced bore is specified in API/ASME/MSS standard.

thank you all I appreciate your contributions

I think Srini has covered all the issues on manual reset.

For the rest my 2p worth

Unless you are pigging the line I would always use a normal (ie reduced bore) ball valve. The cost size etc of the full bore valve is not justified in shutdown valves unless you need to pig. The extra pressure drop is minimal unless you are dealing with a very short very low pressure drop system.

With partial stroke you need to consider the consequences of partially stroking the valve. For those that close its usually ok, but for a blow down valve that opens in emergency you cannot partially stroke these valves as you will vent the system.

As was mentioned above the size of the reduced bore is a standard based on piping standards and typically is one size down from the valve size.