pilot psv in steam service with 'condenser' on pilot line

[jrwchem]

Hello,

We have a pilot psv on a superheated 600 psig steam line. We operate close to the set pressure of the psv, hence a pilot psv was selected.

We were told by the vendor that the maximum temperature the o-rings, etc... can handle is around 400 F. Therefore, there is a condenser on the pilot line which radiates to ambient atmosphere to try and cool the steam to a suitable temperature.

The psv is located outside.

We are wondering if anyone else has used something similar, and could share their experience.

Best regards,
Jonathan

 

[gerhardl]

About ten years ago i was partly involved in a similar case. After some start-up problems, I believe caused by a combination of impurities in the steam pipeline and fluctuating steam conditions on top of measuring and calibrating inaccuracy and to short condensation coils, the system has worked without problems.

If you do not already have checked this out, I also believe pilot oprated systems exists with steam condensation and in addition a membrane separated secondary clean pilot fluid circuit to operate the pilot without impurities influencing the operation.

I am a bit unsure about the present status and construction availability, but you could try Weir with the French Sarasin-RSBD pilot operated PSVs supplied after European Atomic Power-plant safety requirements.

 

[jrwchem]

Thank you Gerhardl.

Was the psv used in outdoor service?

Regards,
Jonathan

 

[jrwchem]

Gerhardl,

What we are most concerned about is potential freezing. Our ambient temperature can drop to about -20F.

Did you have any problems with freezing?

Many thanks.
Jonathan

 

[jrwchem]

Just a little more info.

The valve is a Dresser 3900 modulating pilot series, with a 2900 series heat exchanger installed on the pilot line.

Thanks in advance to any help provided.

Regards,
Jonathan