Isha90,
More information would help!
- What is the Commodity?
- What it the Design Pressure?
- What is the Design Temperature?
- What is the Line or Nozzle size?
- Will this Valve be manual or actuator operated?
Is there any more information we should know?
Sometimes its possible to do all the right things and still get bad results
Additional thoughts:
- What type of the valve is specified in the current Piping Spec or used in the existing power plant?
- Is there any issue of the drain valve in the plant?
How often is the piping drained. I guess only once a year for maintenance. Therefore actuated operated valves are not really nessacary. DN50 is normally large enough for drains, depending on DN of pipes you should also think of installing vents to support the draining. Instead of globe a gate, butterlfy or ball are more convenient for draining since the kv-value is much higher. Seals must resist temperature and medium.
Please note that some drain valves in thermal power plants must be power actuated to prevent water induction into the steam turbine. See ASME TDP-1 for the latest requirements for drains.
As far as I remember we always used ball valves DN25 with blind flange at the end to prevent against loses in case of leackage. Ball valves are small, cheap and can make a good end connection when flanged or screwed.
Drain valves for steam lines in a thermal power plant are a special application since pressure drops across the valves can be very high (considered as "severe service"). I suggest that you move this post to the Power generating facility forum to get more appropriate responses.
