Balancing Vacuum Header

MetroSystemAl

Does anyone have any ideas or suggestions on balancing the main header for a metro-pipe steam system that works in a vacuum. We have installed riser valves but when the main steam valve is only about 10-15% open some risers don't seem to get the same amount of steam through. All the traps have been checked and/or replaced. The system is pretty tight and can maintain a vacuum. Any information would be appreciated.

Steamhead

That system is supposed to work

by varying the level of vacuum rather than restricting the quantity of steam. It would have originally been installed with Dunham Differential Vacuum (later called Vari-Vac) control equipment. Is this equipment still in place and working? 

MetroSystemAl

Varivac System

yes, we have the dunham bush varivac system in place with a working differential pressure switch. however, it is just that some areas are over or under heted at times...could a defective heat balancer cause this issue? 

Steamhead

First thing I'd check

is whether you are getting the same level of vacuum in all parts of the system. The vacuum in this system extends all the way back to the main control valve rather than being confined to the return lines, though the steam-side is under slightly less vacuum than the return side. You might have to invest in a few vacuum gauges but it would let you see what's really going on. I bet you find some variations corresponding with your under- or over-heating issues.

MetroSystemAl

THANKS!!!

yes we do have gauges on the return line but only on the main condensate return. that is a great and low cost idea to but a gauge for multiple reutrn lines. thanks forthe advice!!!

Steamhead

Let us know

how you make out. 

Jamie Hall

I'll add...

my usual comment about partial port (in this case, partially open) valves and saturated steam -- as saturated steam goes through a partial port and re-expands, a surprising amount of it condenses instead of just expanding.  Which can make for low steam supply (if any!) on the downstream side of a part-open (or reduced port) valve.



This goes with Steamhead's comment: control your heat on the vacuum side, not the supply side.

MetroSystemAl

Return side control

yes, agreed my belief was to put valves on the return lines not the supply lines for the simple resaon that the valves might act as a metering device as on a refrigeration system flashing the gas(the steam) causing too much condensation........i will work with what i got and adjust controls through programming to minimize the noise.