ALTERNATIVE FUEL SYSTEMS, INC.

M456 and M456-1 Thermostats

PROTECT YOUR LPG FUEL SYSTEM COMPONENTS

FROM THE DAMAGING EFFECTS OF HIGH CONVERTER TEMPERATURES, WHILE OPTIMIZING FUEL VAPORIZATION!

  Propane is a gaseous fuel. When it is stored in the fuel cylinder  under pressure, the fuel is liquid. To be used as a motor fuel, the propane in it's liquid state must be heated and allowed to return to a vapor. This process occurs in the LPG converter. In a water cooled system, the heat necessary to vaporize the liquid propane is provided by the engine coolant. This heated coolant enters the converter from the engine block, heats the converter and returns to the water pump to be re-circulated. The coolant actually serves two purposes. First it provides heat to vaporize the fuel. Secondly it prevents the converter from freezing. The process of converting a liquid to vapor results in a refrigeration effect. If the converter is not sufficiently heated, this effect will cause the converter to freeze up, and damage internal components.

 The optimum temperature for vaporizing propane is 130°. Most forklift truck engines run in excess of 190°. The cooling effect of vaporizing fuel is not enough to overcome 190° temperatures. If the heated water is allowed to continue to flow uncontrolled through the converter, the fuel temperature will rise well above 140°.  At temperatures above 140°, propane begins to re-refine inside the converter. This process causes the various compounds, oils, and impurities in propane to separate leaving the heavier solids to accumulate in the converter. This sediment will cause diaphragms to deteriorate, and seats to fail due to ever increasing primary pressure. Any contamination on the primary seat will cause the primary pressure to rise in an effort to stop the flow of fuel. Either of these types of damage will cause premature failure of the converter and are not covered under warranty. Depending on the quality of the fuel, this can occur in a very short time.

 The solution? Use the cooling effect of vaporizing propane to keep the converter below the 140° threshold. All that is necessary is a variable restriction in the coolant line of the converter. Slow the flow of coolant, and the converter temperature drops. When the converter nears the 130° vaporization temperature, allow the coolant to resume flowing unrestricted and the temperature will rise. This is exactly what our M456 and M456-1 thermostats are designed to do. The change in flow is always variable. It is not an on / off control. Since the change in thermostat opening is incremental, the temperature does not vary to extremes. The goal is to maintain a converter temperature in a narrow range between 130° and 140°. Our thermostats have successfully met this goal on all makes and models of fork lift trucks.  The thermostats may be installed on any size converter, from any manufacturer. The direction of flow is clearly marked for ease of installation. To function properly the thermostat must be installed on the coolant outlet side of the converter, as close as possible to the converter. Drawings are available.

P/N: M456 Thermostat with two machined 5/8" hose barbs. To be installed inline in the hose returning to the water pump. Due to being a hose barb and not having internal threads, there is slightly more flow than M456-1. This is more suitable for larger engines that flow fuel at a higher rate	P/N: M456-1 Thermostat with two 3/8 NPT Female pipe threads. To be installed directly to the coolant outlet of the converter. The closer to the converter our thermostats are installed, the faster the response time.

Vaporizing temperatures at various air fuel ratios

	The optimum stoimetric mixture of propane is 14:1. At 14:1 the optimum vaporizing temperature is 130°. Our M456  and M456-1 Thermostats keep the converter fuel temperature in the range between 130° and below 140°

Examples of typical damage to an IMPCO JB converter caused by the residue left when components in propane separate

	When contaminants build up on the primary valve, the primary pressure increases until a seal is made. Eventually it requires more pressure than the primary seat can withstand. The rubber will cut or the spring bar will deform. Both of these conditions will cause failure.			The contaminants that cause primary  diaphragms to fail can also damage secondary diaphragms. The residue will soften the diaphragms, and eventually cause holes.			The contaminants that cause primary seat failure, also damage the diaphragms in the converter. The residue will soften the diaphragms, and eventually cause holes.
Extend the Life of your LP Components, and reduce repair expenses. Install a thermostat!