The Steamboating Forum

My hotwell is perhaps 18" above the condenser. Interesting that you are seeing such a large drop from the boiler to the engine. Wonder where most of it is happening?

I may be wrong but wouldn't full boiler pressure only be seen in the steam chest at full stall, regulator open? It is surely about flow/usage?

Bigger prop anyone?

"wouldn't full boiler pressure only be seen in the steam chest at full stall, regulator open? It is surely about flow/usage?"

Yes, that is correct. However in current steam plant practice, the pressure drop (pressure loss) from boiler to the steam chest is only about 3% of the main steam pressure, with another 3% pressure loss across the steam throttle valve(s) when they are wide open at full power.

A properly sized steam pipe from boiler to reciprocating engine steam chest, including all valves, should be less than 10% of the boiler pressure. Of course extra pressure drop in this piping limits steam flow and power output. When running at full power the steam chest pressure will alternate significantly, but should not drop to less than 90% of boiler pressure.

The rapid pressure oscillations in the steam chest of an engine running at several hundred RPM can often foul up the readings from conventional pressure gauges, especially if there is a seal loop preceding the gauge. In that case the pressure gauge needle can jump around far more than the actual steam chest pressure, giving the impression of very low steam chest pressure, when in fact the actual steam chest pressure is much closer to boiler pressure.

Early steam engine indicators (recording cylinder pressure vs stroke) could not function properly when higher speed steam engines were being produced in the late 19th century, and special indicators were developed to compensate for this.

And too, the size of the steam chest or internal volume of the steam chest probably helps to equalize the pressure between the two, acting as a reserve. Then there is the piston valve with no primary area to store steam. Seems like that would be a case where adequate piping size would be even more critical.

-Ron