A frequent question concerning oil field engines is how to
connect the gas supply. The majority of oil field engines were
configured to run on well-head natural gas. Today, propane is the
natural substitution for these engines, but most people have never
tried to run an engine on propane until they run into an oil field
In my experience propane -often called ‘vapor gas’ – is
much more user-friendly than one might think. The important thing
to remember is fuel and air must be delivered in the correct
proportions. How you deliver that mixture to the engine doesn’t
matter: If the fuel is mixed right, you could just place a hose at
the mouth of the engine’s intake, and it would run.
Fuel Line Issues
Carburetion problems are eliminated with propane-burning
engines. Since propane is a gas and needs no vaporizing, all these
engines need to operate is a live fuel line. Everyone has an
opinion on the best way to plumb these fuel lines, but I’ll
share what works for me.
In the photo of the 15 HP Reid (Photo #1) the gas supply line
enters at the lower left. The propane is plumbed to the hot tube
upstream from the regulator, since the hot tube requires higher gas
pressure than the engine.
In this case, the hot-tube burner is a Bunsen with a small
orifice. A good control valve for this hot tube burner is a
hydraulic needle valve, but you can use a needle valve off an old
kerosene weed burner. This works very well – maybe even better than
an original hot-tube burner valve.
Next, the gas for the engine enters the regulator. I’ve had
good luck with RV-style regulators such as the Marshall Brass #230.
Many of these regulator types produce 6 to 8 ounces of pressure but
also allow for a high volume of gas. A word of caution, however:
Some regulator pressures are too high for an oil field engine. I
have found that high-volume, low-pressure regulators work best, as
engines can easily flood on propane. Also, check fittings and
regulators to make sure they don’t have any small orifices (as
many do) that will constrict propane flow.
From the regulator, propane enters the engine through a throttle
valve. Propane is more combustible than natural or well-head gas,
so it doesn’t take much to run an engine. I prefer the old dial
cock-type valves with a diamond-shaped cut inside for reducing the
propane feed to a trickle. These valves are sensitive and need an
adjustment now and then. I often give them a slight tap with my
pocketknife or the side of a wrench when running the engine. The
older-style valves also afford the operator instant control of the
gas, from a slight trickle to a large blast. You could use a needle
valve with no problem, but you lose that instant control. The
proper throttle valve setting is often tricky to perfect on an
engine you’re unfamiliar with, but trial and error will usually
show you the sweet spot on the engine where it starts and runs
The old dial cocks can be a problem because many are as old as
the engine itself. Also, they’re often hard to locate and can
be somewhat pricey. Dial-cock valves can be purchased from
industrial supply houses and oil field suppliers, but their cost is
usually comparable to what you would pay for an original at an
antique engine show. If you’re like me and have a Bessemer,
you’ll want to purchase an old Powell valve that has
‘Bessemer’ stamped on it. Original Reid valves with the
large dial and stubby handle are even harder to locate. I still
don’t have one!
Accumulator Tank Issues
Accumulator tanks are usually placed after the regulator and as
close as possible to the throttle valve. I’ve never needed an
accumulator tank on my 22 HP Bessemer or my 15 HP Reid, but I
believe that an accumulator can be a big help on larger engines
that are hungry for fuel. Many engines won’t run on propane
without an accumulator tank.
A good rule of thumb is to use an accumulator equal in size to
the volume displaced by the engine’s cylinder. You’re less
likely to need an accumulator using a 300-pound propane bottle over
a 100-pound bottle.
In the photo of the 22 HP Bessemer (Photo #2), notice the
plumbing is routed similar to the Reid, until it passes the
regulator. The propane then passes through an original-style
driller’s wheel bypass, through the governor and then under the
engine, ending at the intake valve. With this type of
configuration, be certain the driller’s wheel valve is closed
and the governor valve stays completely open during operation if
you want to maintain control at the throttle valve.
Propane Engine Etiquette
Proper regulation and the right throttle setting are essential
to operating a propane-burning engine. If the right air-to-fuel
ratio isn’t achieved, the mixture will not ignite. If you start
your engine, and it doesn’t fire within a few attempts, shut
off the gas and roll the engine over a few more times. This will
either cause the engine to fire, or it’ll air out the cylinder
for another attempt. Never let the gas run too long without this
engine running as dangerous amounts of propane can accumulate at
the intake and inside the engine.
The best advice is stay safe and always handle propane – or any
other flammable materials – with caution. Also, make sure all
fittings are good and that all hoses are rated for the pressures
they will hold.
As always, please call, write or e-mail if you would like a free
membership in the Oil Field Engine Society (OFES).
Contact the Oil Field Engine Society at: 1231 Banta’s Creek
Road, Eaton, OH 45320-9701, online at: www.oilfieldengine.com or
e-mail at: email@example.com