Steam Pipeline Cleaning - Blow through a Silencer 1

[Petko]

We are installing multiple replacement expansion loops in an underground steam line. Particulars are a 16" line carrying 300 PSIG steam, 40 degrees SH. We are exploring options to do a steam blow instead of chemical cleaning. We need to do a "Silent Blow" due to proximity to residences, but the normal Silent Blow company is not available. Does anyone have an experiences (good or bad) with trying to do a steam blow through a standard steam silencer? Also, does anyone know any good references available that would tell the minimum velocities needed for good cleaning?

 

[athomas236]

Petko,

There is an excellent Germanstandard (available in English) called Internal Cleaning of Water Tube Steam Generating Plants and Associated Pipework, VGB-R 513 that covers flushinh, chemical cleaning and steam blowing.

With regard to velocity, the aim during blowing is to achieve kinetic energy that is 1.3 times that during full load operation. This means:

(Mb^2*Vb)/(Mf^2*Vf) > 1.3

where Mb is steam flow rate during blowing
Mf is steam flow rate at full load
Vb is specific volume of steam during blowing
Vf is specific volume at full load.

Regard,

athomas236

 

[rmw]

Athomas addressed your question regarding velocity, but what about the 'what it is' that you are trying to blow out of the line; weld rod, slag, lunch buckets, etc? Since a silencer has baffle internals that do the silencing, had you thought about how to protect the silencer internals?

And, as your steam specific volume is increasing as the pressure necessary to obtain the 1/3 max velocity drops to atmosphere at the silencer, since the silencer has a design pressure drop across it, it would have to be carefully sized for end of line conditions.

rmw

 

[insult2injury]

There is also the option of doing air blows although this doesn't address your initial concerns.

I2I

 

[Petko]

Thanks for the feedback, all.

I was able to use Athomas' information to do a calc on the necessary steam flow, and then work with a silencer manufacturer to size the discharge unit (I'll do a recheck on the specific volume with the silencer backpressure - thanks for the tip, RMW). We discussed the problem of potential internal pluggage, and have oversized the silencer to help accomodate. I also intend to have a pressure gage between the blow-down valve and the silencer, and can monitor for blockage as well as have a secondary check on flow. We have a backup plan for removing the silencer and free-blowing during daylight hours: Not the best, but it gets us blown out if a lunch bucket does find its way down the line.

I was also able to link off of Athomas' answer to find the rest of the discussions on this subject (I had been wrongly searching for "steam cleaning" when all the real answers were under "steam blows"). Anyway, I think you all have given me a good start.

This was my first time posting a question to the forum, and I again appreciate the answers.