It's 2:00am, I'm at work here in the Boilerhouse and all's quiet, at least for now! I recently bid on Ebay for a wet-ometer. I didn't get it at $175.00. I guess the secret of thier value is getting out so I'll write on the subject a bit.
Of course when I was pumping, all of the powerhouses here in Northwestern Ohio had gasometers on the engines. Most were wet-ometers. These are ones that have an inverted can free to float & rise up within an upright lower can using crude or motor oil for a filler.The upper can serves as the gas resevoir and has a linkage on it connected to a valve on the high pressure incoming gas pipe to shut off the incoming gas when it has filled. A dry-ometer is one that uses a diaphram[rubber] connected to a valve to shut off the incoming gas. These descriptive wet/ dry -ometer terms were used by the now long dead oldtimers in our oilfields and are as I learned them. When a person is depending on making a living pumping oil as I did for many years, he learns things to make life easier running these old engines. Gasometers do just that. They are not fixed accumulators.
Most diaphram gas regulators cannot fufill the large and varying gas demands of these old oilfield engines such as when starting, idling, or under load. Many operators use a fixed accumulator, such as a pipe or tank,to compensate the regulators lack of capacity for these engine's intake requirements. When the engine calls for gas the volume stored in this accumulator rapidly decreases and so does the pressure. Many factors come into play affecting the performance of the regulator & accumulator. Atmospheric pressure. Ambient air temp. Humidity. The size/volume of the accumulator and the gas regulator used. What this amounts to is an opportunity for the accumulator/regulator to vary in it's performance. These can result in your engine starting differently, not at all, running rough, stalling, and the need to mess with the gas valve to keep it going throught the day as conditions vary.
Wet or dry ometers[ I prefer wet] provide a steady, consistant, low pressure, large volume supply of gas available to the engine when called for. None of the above mentioned conditions affect them. The engine calls for gas, the upper can or diaphram drops, it's linkage opens the high pressure gas inlet valve[usually 3/4 or 1 in. pipe] to admit more gas to compensate the loss as it does. Remember, even when admitting gas, the pressure and volume available within the gasometer and to the engine remains the same. Once gas fills the gasometer, the inlet [ball] valve is automatically closed via the linkage connected to it from the upper can. With a consistant volume and pressure provided, the engine starts and runs the same every time. In fact, with a good ball valve on the inlet of the ometer, you dont need to use a LP gas regulator at all. I've had unregulated casing head gas pressure increase well over 100psi after pumping for awhile with no effect on the ometer or engine. Without a gas regulator though, you'll not get much motion from the upper can and not as much of a show for people to watch. Between engine firings, a diaphram regulator has time to refill the ometer within it's volume capacity. You can adjust the spring on them to give the ometer's upper can or diaphram a lot of motion and put on a good show.On a lot of these old oilfield engines you'll see 2 notches filed on the gas valve. The first is the pumpers setpoint for starting, and the one further open is the setpoint for running. Once the gas valve locations are noted, engines will start and run all day pretty much the same way every time unless the tramper screws up while starting, the tube is not hot, or something else is wrong with the engine. On a S. M. Jones, I used to get mad at the mice. They loved to crawl into the mechanical valve's exaust pipe from out front of the powerhouse and build a nest on the top of the atmospheric exhaust valve. This would then require taking the valve chamber apart and cleaning it out before starting up to pump. I cut my exhaust pipes ends on a 45 degree angle to deter them. That worked. Buggers couldn't crawl in upside down.
I hope this will be of interest and benefit to someone. The writing of it has brought back some of my very pleasant memories of times spent out in the oilfields.Thanks Harry. The very best to you all.--John