Moline vacuum system

Jim Walsh

Anyone have any experience with a Moline 2-pipe vacuum steam system? I got called to check why heating bills are so high. Boiler is a Weil McLain EG-50 Natural gas steam.I checked boiler steam rating(sq. ft.) vs. connected load and it's sized properly. Was wondering if it is practical to try to run this type of system on gas being that it was designed to operate on coal. Thoughts?

Steamhead

Paging Boilerpro!

He's the Moline specialist here.

The Moline was one of the top-of-the-line systems in the old days. It was actually a Vapor/Vacuum system. An ejector driven by steam from the boiler pulled the air out of the system and discharged it from a vent, after first running thru a condenser to keep steam from prematurely closing the vent. Once the steam got as far as the vent, it closed, and the whole system went into a vacuum as the steam cooled.

Running vacuum this way only worked well with coal firing. The steam stayed up for a long time, then went down gradually, allowing the system to exhaust all the air before the vacuum formed. This is far different from oil or gas firing.

Molines can run well as Orifice systems by limiting the boiler pressure, since each radiator valve was sized to the radiator it served. Use a Vaporstat at the boiler instead of a Pressuretrol. This will keep steam from getting into the dry (overhead) returns.

When Boilerpro sees this, he can give you more specifics. He's worked on a bunch of these systems.

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DanHolohan

Moline is in the Library

The original book from the company:

Moline

It pays to wander off the Wall.