I need to install a desuperheater valve in a pipe with only half the recommended straight pipe upstream and downstream, what is best:

-Install the desuperheater valve in proportion upstream-downstream with the recommended distances.

-Maintanin recommended upstream (or downstream) distance and keep the other as available.

The desuperheater is a Yarway Templow valve, the pipe is 36" and the steam pressure is 15-20 psi.

 

Templow requires 6D upstream & 15ft downstream straight run. For your case, it is 18 ft upstream.

Templow desuperheaters atomize (and spray) cooling water directly into flowing superheated steam. Steam vaporises these minute droplets with a change in enthalpy and hence temperature.

Insufficient upstream/downstream straight pipe only increases possibility of incomplete vaporization under all operating condition leading into bad controls/water hammer.

Generally the lowest controllable temperature achieved by these desuperheaters is 6 deg C above the saturation temperature (of steam at the pressure).

You may use upstream flow straightener device and get maximum possible downstream straight run in the installation to ensure proper mixing and vapourization.

In case you still have problem, you may contact Yarway/Tyco for help.

Regards.
Abhijit Goswami