Oil Field Engine News

Fuel for Thought

| March/April 2004

15 HP Reid Engine

Photo #1: Propane feed line branches to the hot tube before reaching the pressure regulator. The hot tube needs higher pressure than the engine.

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 engine.

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.

Regulator Issues

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.