I have a drip leg on a 300# - SS316L line where I have to select a couple of "block" valves (1" size)
Previously the line was 2" and we had gate valves installed (Press 30barg, Temperature 300?C, that's why we didn't use ball or plug valves).

The vendors catalogues for SS gate valves go down to 1.1/2".

Which valve would you recomend me to use there?

If drip leg = draining point (with or without steamtrap) and the purpose is draining and/or blowing out dirt/condensate, a good quality ball valve with graphite sealings suitable for given pressure and temperature could be used for this 'end of line use'.

Ask for steam references. CS recommended, SS if solid and steam references from supplier.

Needle valves in SS (Note correct sealings for steam temperature and pressure required) can be used as rough regulating valves, but not suitable for 'dirt /cleaning' as dirt could clog the reduced, angeled conduit.

For inline use: ball valves could be used for steam, but note: cavitation will occur almost immidiately if not 100% closed and thight. Remember steam velocity is usually 15m/s (90 feet/s or up to about double).

CS is recommended mostly for economical and commercial availability reasons. Of course SS is best on a material basis, but valve buyers very often back down and select CS when the price total (and often deliverytime) comes up.

You could check both.

There is of course present the chance of galvanic corrosion CS /SS, but this should cause no great problems taking proper steps (I'm no expert on this). Very often, as example, land based treatment plants for drinking water or process plants will have SS lines but Nodular Cast Iron or steel valves.

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