GB2124698A - Diesel engine fuel systems - Google Patents

Abstract

Vehicle or other diesel engine fuel systems are protected against disablement at low temperatures due to fuel congealing by insulation of the fuel tank and, preferably, fuel lines and other parts of the system. The insulation, especially for existing systems, may include spray coating with a polyurethane compound which solidifies and expands to form a rigid or semi-rigid foamed coating having high thermal insulation qualities and good resistance to impact and other damage. A tank heater may be incorporated to operate only intermittently, e.g. while the engine is running.

Description

SPECIFICATION Diesel fuel systems This invention relates to diesel fuel systems, particularly on road vehicles though the invention may also have application to the fuel systems of engines of other types of transport such as boats, tractors, contractors' equipment, equipment used by emergency services, and stationary and portable engines particularly where used and/or stored or parked outdoors and subjected to adverse weather conditions.

A serious drawback to the use of diesel fuel is its property of congealing at low temperatures, it begins to congeal at about -9" C so that it will not then pass readily through the filters normally fitted to fuel systems and along narrow bore fuel lines.

Once congealing has occurred the vehicle or other equipment is effectively disabled with consequent delay and cost in terms of operating time, and, in the case of road vehicles, probable blockage or roads (usually under already adverse winter conditions) which may hold up traffic and cause danger of accidents.

Attempts have been made to reduce these difficulties e.g. by using additives in the fuel which increase its cost and are wasteful because they are unnecessary when conditions improve. Another proposal has been to install an electric wire heating element acting on the inlet end of the fuel line within the fuel tank which is switched on for a few minutes before attempted start-up in the hope of freeing the flow from the tank if the fuel has congealed.

The object of the present invention is to provide means for effectively protecting a diesel fuel system from the effect of low temperatures over a substantial period yet which is simple and cheap to install, and, importantly, can readily be applied to existing systems e.g. on vehicles already in service.

According to the invention a method of protecting a diesel fuel system against the adverse effects of low ambient temperatures includes the step of applying a coating of a thermal insulating material to the exterior of the fuel tank of the system and, preferably, to fuel feed lines and components of the system.

Preferably the insulating material is a polyurethane based compound applied by spraying and which solidifies and expands on application to form a rigid or semi-rigid foamed coating of substantial thickness.

The method of the invention may further include the provision of means for heating the fuel in the system, for example electric heating of the fuel lines as referred to above and/orthe provision of a thermostatically controlled or other immersion heater, conveniently in the fuel tank itself, and one example of such arrangement is described in our co-pending patent application No. 8213399 dated 10th May 1982.

The invention further resides in a vehicle or other diesel fuel system thermally insulated in the manner defined above.

invention the fuel system of a heavy goods vehicle was protected by spray coating the exterior of the fuel tank and fuel feed lines including the filter with a polyurethane rigid foaming compound sold under the trade name or trade mark "FROTH-PAK" manufactured by Insta-foam Products Incorporated (U.S.A.).

This compound is applied as a liquid spray, mixture of its component material taking place at the time of application from a portable pack by means of a hand held spray gun. This material has excellent properties of adherence to the exterior surfaces of the tank etc and cures by chemical reaction almost immediately with a degree of expansion or foaming to form a practically rigid cellular coating, the application being effected so that the finished coating is at least 1 9mm (3/4 inch) thick. Application is controlled to provide a finished material of medium density (about 0.79kg per 0.028 cu.m.; 13/4 Jb. per cu.ft.).

It will readily adhere even to surfaces which have been subjected to corrosion or are not completely clean so that the fuel systems of existing vehicles can be treated quite speedily, the main problems of application being whether there is ready access to the run of the fuel lines etc. The exterior finish of the coating is such that it can be painted with most normal paints e.g. to match the vehicle finish.

This insulating material has the added advantages that it is highly resistant to diesel fuel or other solvents once cured and is also resistant to impact damage. As well as insulating e.g. the tank it will protect the latter from accidental damage and exterior corrosion.

Tests have shown that use of insulation in this way has a dramatic effect on the time taken for fuel contained in the system to cool to its coagulation level when the system is subjected to low ambient temperatures (which, on a fast moving vehicle, may be aggravated by the "chill factor" due to the air flow to which the, usually exposed, fuel tank is subjected).

One experiment showed that a tank of liquid at a temperature of about 50"C above the ambient temperature of still air indoors would take approximately 20 hours for its temperature to equalise due to natural cooling in an uninsulated metal tank while the equivalent test with the tank insulated as referred to above had to be continued for five days at the end of which the liquid had still not cooled to ambient, it was about above.

Thus it is believed that under the kind of operating conditions experinced in bad winter weather (say temperatures down to around -20 C) if the fuel in the insulated system starts at or can be intermittently heated to a temperature of around + 100C, cooling to the danger level would take several days and would protect the vehicle while standing overnight or even over a weekend without any further heating being applied. Even with the fuel at about +5"C it is believed it would take two days or more at an ambient temperature of -20 C for the fuel to approach the danger level.

If the system includes the thermostatically actu ntorl tnnk winter it is Dreferred that the latter is switched so that it can only be operated when the vehicle is running t(s avoid drain on the battery and that it is set to heat the tank fuel to around +1 0 C, thus its operation is extremely economical yet, in combination with the insulation, it will afford almost certain protection and thus vastly increase vehicle reliability and cost saving.

The invention may be particularly useful for intermittently used eniergency equipment such as fire appliances, ambulances, police or military vehicles, lifeboats and the like where absolute reliability and instant startup after periods of standing may be vital.

CLAIMS (Filed on 2.8.83) 1. A method of protecting a diesel fuel system against the adverse effects of low ambient temperatures including the step of applying a coating of a thermal insulating material to the exterior of at least the fuel tank of the system.

2. A method as in Claim 1 wherein the material is applied by spraying.

3. A method as in Claim 2 wherein the material is a polyurethane based compound which solidifies and expands on application to form a rigid or semi-rigid foamed coating of substantial thickness.

4. A method as in Claim 3 wherein the finished coating is at least 19 mm thick and of medium density.

5. A method as in any preceding claim wherein thermal insulating material is applied to fuel feed lines, fuel filters and other components of the system in addition to the tank.

6. A method as in any preceding claim including the provision of means for heating the fuel in the system at least intermittently to a temperature sufficient to enable the insulating material to prevent cooling to danger level for a period of several days in which the ambient temperature remains low.

7. A method as in Claim 6 wherein said heating means is adapted to raise the temperature of the fuel to an initial temperature of at least +5 C.

8. A method as in Claim 6 or 7 wherein said heating means is a thermostatically actuated tank heater.

9. A method as in Claim 8 wherein said heating means is operable only while an engine fuelled by the system is running.

10. A diesel fuel system protected by the method of any one of the preceding claims.

11. A diesel powered vehicle having a fuel system protected by the method of any one of claims 1 to9.

12. A method of protecting a diesel fuel system substantially as hereinbefore described.

13. A vehicle diesel fuel system substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. switched so that it can only be operated when the vehicle is running t(s avoid drain on the battery and that it is set to heat the tank fuel to around +1 0 C, thus its operation is extremely economical yet, in combination with the insulation, it will afford almost certain protection and thus vastly increase vehicle reliability and cost saving. The invention may be particularly useful for intermittently used eniergency equipment such as fire appliances, ambulances, police or military vehicles, lifeboats and the like where absolute reliability and instant startup after periods of standing may be vital. CLAIMS (Filed on 2.8.83)

1. A method of protecting a diesel fuel system against the adverse effects of low ambient temperatures including the step of applying a coating of a thermal insulating material to the exterior of at least the fuel tank of the system.

2. A method as in Claim 1 wherein the material is applied by spraying.

3. A method as in Claim 2 wherein the material is a polyurethane based compound which solidifies and expands on application to form a rigid or semi-rigid foamed coating of substantial thickness.

4. A method as in Claim 3 wherein the finished coating is at least 19 mm thick and of medium density.

5. A method as in any preceding claim wherein thermal insulating material is applied to fuel feed lines, fuel filters and other components of the system in addition to the tank.

6. A method as in any preceding claim including the provision of means for heating the fuel in the system at least intermittently to a temperature sufficient to enable the insulating material to prevent cooling to danger level for a period of several days in which the ambient temperature remains low.

7. A method as in Claim 6 wherein said heating means is adapted to raise the temperature of the fuel to an initial temperature of at least +5 C.

8. A method as in Claim 6 or 7 wherein said heating means is a thermostatically actuated tank heater.

9. A method as in Claim 8 wherein said heating means is operable only while an engine fuelled by the system is running.

10. A diesel fuel system protected by the method of any one of the preceding claims.

11. A diesel powered vehicle having a fuel system protected by the method of any one of claims 1 to9.

12. A method of protecting a diesel fuel system substantially as hereinbefore described.

13. A vehicle diesel fuel system substantially as hereinbefore described.