Posted by tarzan on December 08, 2001 at 07:55:12:
In Reply to: Re: reducing system pressure posted by Tony Conner on December 02, 2001 at 05:48:57:
Louisiana State University published a great paper on this back in 1981...Contact them via the web...
: You can often get steam quality problems when operating a boiler at significantly less than it's design conditions. Spirax Sarco has a video shot in the steam space of a running fire tube boiler. They dropped the pressure from 115 to about 50 PSIG (if I remember correctly), and you could literally see the fog form in the steam space.
: They deliberately did several things to cause steam quality problems - on/off feedwater control, let the TDS run way high, etc. Very impressive video.
: Make sure that the traps on your steam mains are big enough for the lower pressure drop they'll see when running at the reduced pressure. You'll also need to see if PRVs and temperature control valves in your system are large enough at the lower inlet pressure. A large university near me just took their system operating pressure back up from 60 PSIG to 125, and they've suddenly got all kinds of problems with PRVs hunting and not standing up very well. All of these control valves are now WAY oversized with a bigger pressure drop across them.