Re: Boiler Blowdown

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Posted by Vern on December 26, 2001 at 22:18:12:

In Reply to: Boiler Blowdown posted by JimC on December 25, 2001 at 17:54:40:

: Can some one help me?
: I seem to be getting conflicting information about the proper location and types of bottom blowdown valves and procedure for operating them.

: We have a 100 HP, three-pass, fire tube, boiler burning natural gas. Producing 100psi steam. presently there is a ball valve next to the bottom of the boiler and directly below that, there is a slow opening globe valve.

: For years we have conducted our daily bottom blowdowns by opening the fast opening ballvalve first, then the slow opening globe valve second. Then closing in the reverse order.

: Now, there is a chemical rep. who says that we are wrong. What is the correct valve arrangement for this boiler and what is the correct procedure for blowdown? Please explain the rationale for your answer. Many thanks in advance!

You are correct in your procedure. If you open the slow valve first and then the quick opening, you will shock load your piping. In extreme
cases you can physically break either the piping or the valve. Here in Ca. in the mid 80's such a circumstance happened. The slow opening valve
was left open all the time and the boiler operator kicked open the bronze ball valve, which was correctly rated for the pressure and temperature,
and the ball valve broke open. The boiler operator died as a result, because some idiot had locked one of the emergency exit doors.

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