FUEL OIL HAZARDS
Use of Oil for Fuel Has Increased in Recent Years and the Consequent Fire Risks Have to be Taken Into Consideration—Summary Showing Practices Followed and Peculiar Conditions Found—Some Safety Devices in Use
THE use of oil for fuel in the various industries has increased rapidly in recent years and will no doubt become more common as the production of oil increases. Being more or less highly inflammable, particularly when under pressure or when heated to the flashpoint, its use in furnaces, both stationary and portable, has introduced a very considerable fire hazard. This hazard may be greatly reduced by the use of approved methods in planning and installing fuel oil systems. Our own experience in the shipbuilding industry during the past year places the fuel oil hazard at the top of the list of causes in the fire loss schedule.
It is not the purpose of this paper to propose new standards to follow in laying out fuel oil systems, as the rules and regulations of the National Board of Fire Underwriters for the storage and use of fuel oil are, of course, accepted by us, and these rules cover the situation fairly well. Those of us who come in direct contact with the actual work in the field meet with conditions almost every day which are not and cannot be fully covered by established rules. The expediency of industry, peculiar local problems and the inventiveness of operators, are factors to be reckoned with for the reason that they often compel modification of existing standards and call for special ruling, the soundness of which necessarily must be based on the judgment and experience of the inspector. It will rather be my aim to submit as briefly as possible a summary showing practices commonly followed, some of the peculiar conditions found in the field, safety devices in use and methods which have been found effective for controlling fuel oil fires.
We learn from a report prepared by General Fire Marshal James McFall, of the United States Shipping Board; that during the past year there were 157 fires, with losses aggregating $320,000 in the 186 shipyards under his supervision. Of those fires 43 resulted from the use of fuel oil and caused a total loss of $125,000. One fire caused a loss of $100,000; one fire $15,000, six fires more than $500 and less than $5,000; eight fires more than $100 and less than $500, and five fires less than $100 each; the remaining twenty-two fires were reported as causing no losses.
From this report it will be seen that in the shipbuilding industry the fuel oil hazard is by far the most important single factor to consider in connection with our work, but it should be remembered that on account of the pressing demand for ships during the war, shipyard plant construction was carried on under exceedingly high pressure and, in consequence, fuel oil installations were in many cases of a temporary nature. This was particularly true during the first part of the year. For this reason the loss ratio established during this particular period may not hold good in normal times, as this same report shows that the heaviest losses took place before the most necesary safeguards could be provided.
Typical Fuel Oil Fires in Shipyards
- Fuel oil furnaces in wood frame fabricating shop. Oil supplied burners by gravity from small tank directly overhead. Overflow in small tank let the oil spread over furnace and become ignited; fire spread to building very rapidly, causing total loss.
- Construction of building same as No. 1. Oil supplied by pump through underground pipes (pressure, 25 pounds). Settling of furnace caused fuel oil pipe to break near burner; oil ignited and fire spread to building before supply could be shut off. Installation approved, with shut-off valve near furnace. Total loss.
- Fuel oil tanks on ship in water were being filled from tank on deck through rubber hose covered by steel wrapping. Electric wires grounded on steel wrapping causing arc which burned hole in hose and ignited oil letting burning fluid flow on top of water between boat and dock. Fire burned 20 minutes and warped 10 plates in hull; damage about $15,000.
- Fuel oil accumulated on water near boat at dock was ignited in some unknown manner. Fire damaged several plates in hull. Loss about $2,500.
- Rubber hose on portable burner operated in copper shop parted under 90 pounds’ pressure. Fuel oil was ignited and the two operators severely burned. Fire spread to building, causing total loss.
*Paper read before the annual convention of the International Association of Fire Engineers, Kansas City, Mo., June 24-27.
The outstanding lesson from fires No. 1 and 2 is quite plain. Fuel oil furnaces should not be placed in a combustible building, nor should burnable materials of any kind be placed near them. Both of these fires could have been put out with small loss had they not occurred in wooden buildings, Fire No. 1 also illustrates the danger from gravity supply from overhead tank in shop.
We learn from fires No. 3 and 4 that fuel oil will readily ignite on the surface of the water. Fires of this kind are often difficult to control, particularly at piers built on open piling, as the fire will instantly spread underneath. Oil should never be allowed to accumulate near piers or dock lines.
Fire No: 5 is typical of the danger in connection with the use of portable burner outfits. These are in common use and for convenience are often of very light construction. The greatest danger lies in the fact that the rubber hose leading from tank to burner is subject to injury or wear causing the oil to escape and ignite. Armored hose is recommended for this purpose, hut it is pot popular with the operators because it is not as light and flexible as the rubber hose. Portable burner outfits should be well constructed and have an automatic shutoff valve on fuel line.
Fuel Oil in Common Use
The oil most commonly used for fuel is the waste from refineries, where the light oils and the volatile elements have been removed. It has a flash point around 160 degrees Fahrenheit and a gravity test of from 20 to 30 Baunie. This grade of oil makes a very satisfactory fuel and will flow readily under all ordinary temperatures. When the demand for fuel oil was heavy and the supply short, which happened during the war, a much lower grade was often used. This oil is brought direct from the wells, and contains such a small amount of Volatile matter that it cannot be distilled with profit. Its flash point may be as low as 65 degrees and its gravity test may run from 12 to 18 Baunie. It is not suitable for use in the industries, as it will solidify in cold weather and give off explosive vapors when heated. It also contains sand and other foreign matter which find their way into the fuel lines and obstruct the flow of oil to the burners. Its use is more costly as a much greater air pressure is required to atomize it at the burner.
In passing from the tank cars to the supply tanks, the oil should be thoroughly strained and all foreign matter removed. When this practice is followed, strainers on supply lines should not be necessary and uninterrupted service at the furnace should result. Strainers on supply lines are generally neglected and allowed to fill up with foreign matter so as to obstruct the flow of oil to the burner, causing interruption of the service and increasing the fire hazard.
Supply tanks should be placed below the level of the ground, either in a covered concrete reservoir, or buried in the dirt. If this cannot be done, they should be surrounded by retaining walls of sufficient size and durability. Tanks must be strongly built and equipped with vent pipes or suitable relief valves. All supply lines leading from tanks should preferably be laid below the frost line and be carried underground to the furnace with drainage towards the tanks. Excessive heat should not be employed to make the oil flow, as it will cause vaporization and invite disasters.
Methods of Distribution
The safest method of supplying oil to the furnaces is by pumping direct from the storage tank to the burner. This method is approved by the underwriters and is in common use. The pressure maintained on fuel oil lines is ordinarily 30 pounds.
The use of pumps causes a slight pulsation in the line, which is partly overcome by placing receivers or accumulators on the lines. It is claimed by some operators that an even fire may be had only when the oil is under steady pressure. To obtain this result, storage tanks are sometimes placed under pressure from the air compressors in the plant. This pressure is ordinarily about 100 pounds. A system of this kind is not approved, as the risk is plainly too great.
A method which is less objectionable and which gives the oven fire in the furnace, so much desired, is to pump the oil from the storage tank into a small tank, whose capacity should not exceed a half day’s supply. This small tank is placed under pressure from the air lines in the shop. Another method is to provide a supply of air to the receivers on the lines supplied by pumps by connecting the top of the receiver to the air line in the shop, using a check valve to prevent the oil from entering the air line.
Gravity feed from tanks placed on roofs or above furnaces should never be employed, as this system has caused many serious fires.
Control of Oil Supply
It is evident that the most important problem to consider in connection with the use of fuel oil is to provide instant control of the flow of oil in case of break in the lines. If a pipe under pressure be broken or ruptured near the furnace, the stream of oil will instantly ignite and liquid fire will be throwm in all directions. Shutoff valves should therefore be placed on the supply lines near all furnaces, and also outside the building. These valves should be plainly marked and located so that they may be easily closed. Failure to shut off the supply of oil promptly has caused many heavy losses. In most cases the manually operated valve has proven too slow, even when conveniently located and resorted to without delay.
There is now on the market, and very generally used, an automatic shut-off valve bearing the Underwriters’ approval, which, when placed on the supply line and given proper care, will instantly and automatically stop the flow of oil in case of breakage in the line. This valve is so designed that when placed in service it will remain open until there is an increase in the discharge when it will instantly and automatically close. In a well laid out system, an automatic master valve is placed near the source of supply; an automatic group control valve is provided for each building, and an individual automatic control valve at each furnace or group of burners. A plain shut-off valve is also installed near each automatic device. These valves should be made accessible and given reasonably good care in order to insure reliable service.
Pressures on fuel oil systems vary from 10 pounds to 250 pounds, depending upon local conditions, the needs of the industry or on the whims of the operators. The automatic shut-off valve must be designed to meet the conditions and requirements of the system on which it is to be installed, in order to obtain satisfactory results. If given proper care, it will work satisfactorily under any pressure down to 10 pounds. Its use is recommended by the National Board of Fire Underwriters for all fuel oil svstems. See index, Miscellaneous Hazards, 198,
Fuel Oil Fires
Fires frequently occur in connection with the use of fuel oil, and means to control them should be provided. A stream of water is not always effective when used in the ordinary way, as it may spread the burning oil. Soda and acid tanks are about as effective as water. When the fire is confined to tanks or fireproof enclosures, steam may be used with success.
I am of the opinion that the foam chemical engine is the most effective extinguisher if used promptly in case of fuel oil fires in shops. The heavy foam discharged has an instantaneous smothering effect on the fire. The foam extinguisher has won a unique place in this field, and its use is recommended for fires in fuel oil and other inflammable liquids. However, full reliance should not be placed in any of the smaller chemical appliances and their use should at all times be bac_____rd up with a sufficient number of large hose lines to protect surrounding property.
It was stated at the outset that the rules and requirements of the National Board of Fire Underwriters covered the fuel oil situation fairly well. These rules are easily obtainable and should be followed as nearly as possible when fuel oil systems are being planned or installed. We find, however, that they do not govern in the majority of cases which come to our notice, and there seems to be a growing demand for a revision of the last edition of the rules. As no change has been made for several years, the present rules do not cover recent developments in the industries. Therefore the Chief of the Fire Department, or the inspector in the field, should make himself familiar with conditions as he finds them to the end that he may offer such recommendations and advice as may not only bring about improvements where possible, but which may also suggest to the operator the best-known methods to prevent or control accidents and fires resulting from the use of fuel oil.