Canadian Grain Commission
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Spoilage and heating of stored agricultural products



Chapter 6 – Control of spoilage and heating

Control of spoilage and heating involves four main steps: preparatory planning, problem determination, problem handling and control, and salvage. Emphasis is placed first on determining the extent and type of the problem, then on applying appropriate measures.

Preparatory planning

When designing or modifying facilities for fire protection and control, the local fire chief should be consulted on such matters as the location of water mains, emergency lighting, and exit provisions. It is necessary for the fire chief to be familiar with the facilities and to be asked to participate in practice fire drills. Staff of the facility need to be equipped with two-way radios, be trained to handle spoilage and heating problems, and be aware of potential safety hazards.

Problem determination

Once spoilage or heating is suspected, the tendency is to react immediately, which often results in incorrect action being taken. This tendency must be avoided. Before optimal control measures can be applied, certain key questions have to be answered including the nature and extent of the problem, commodity involved, temperature distribution, and facilities and staff available. At sea, additional important questions have to be answered including the availability of radio advice and fire-fighting facilities at nearby ports. Answers are needed for the following:

  • What is the nature of the problem? If spoilage is the problem, only a localized portion of the stocks will likely be affected. If heating is the problem, the situation is potentially more serious, as fire could result and affect part or all of the stocks and other facilities.
  • What is the extent of the problem? This is best determined by probing the stocks and using a thermometer or thermocouple to determine the temperature distribution pattern. On no account should the pile or bin contents be opened up suddenly to search for the source of the heating or spoilage, as the exposure of smoldering material to the air may cause almost instantaneous ignition of the entire mass of material (Bowen 1982). If the temperature within the pile is more than 10-15°C above the ambient, then potentially dangerous heating is occurring. If possible, obtain a thermographic profile of silo bins (Rispin 1978). If the temperature within the pile is less than 10-15°C from ambient, probe the bin contents with a deep bin cup and check by visual and odor examination for any spoilage.
  • Which commodities are involved and in what form? It is important to know whether the products affected are cereals, oilseeds, or pellets and whether they are bagged or in bulk, because these factors can affect the type of control measures applied.
  • What staff and facilities are available? After informing the local fire chief of the problem, staff on the premises should be identified and briefed and off-duty staff recalled. A quick inventory of available empty bins, metal-sided trucks, or paved areas into or onto which commodities can be transferred is useful.

Problem handling and control

The following account summarizes methods used to handle and control spoilage and heating situations that occur in commodities stored in indoor or outdoor piles, in farm bins, in vertical silos, in ships, and in port installations, or that occur within equipment such as dryers or conveyers (Table 7 and Table 8).

The methods outlined can only be considered as general guidelines, not as specific instructions for handling problem situations. This is because each spoilage and heating situation is different with unknown modifying factors and the human and financial risks are consequently high. It is strongly recommended that the advice and services of a safety engineer be obtained whenever complex spoilage and heating problems occur, particularly with binned materials.

Table 7 – Handling and control of spoilage in stored commodities
Type of storage Spoilage location and type Handling or control method used
* Double dust mask, rest every 15 min.
** Gas canister respirator, safety belts and ropes, two attendants.
*** Gas canister respirator, safety belts, two attendants, bosun’s chair located above the adherent wall material.
Outdoor piles Top crust, centre of pile Wear a mask.* Separate the material by shovelling, burning, or burying it.
Open-topped farm bins Within 15 cm of wall As above.
Polyethylene-covered farms bins
Farm bins Around doors, on floors of nearby empty bins, beneath roof vent or roof holes As above.
Farm bins Within lower bulk (flood damage) Wear a mask*. Probe for crust, remove the good grain above it and discard the crust and spoiled grain below it.
Farm bins At or near surface as full or partial bridge Use proper safety practices for bin entry.** Loosen material and remove it through the top hatch or the uncovered side port.
Farm bins and vertical grain silos Within bulk as full or partial bridge, as compacted mass, or within unload auger Use proper safety practices for bin entry.** Remove unspoiled material from above, using a portable pneumatic grain elevator (Fig. 11), loosen spoiled material, and remove it through the upper hatch in same manner. A less effective method is to cut a hole in the wall to unload the material.
Within bulk (early stages of spoilage) Aerate and/or dry the material, then rebin.
Vertical grain silos Within bulk (early stages of spoilage) Mix by transferring to another bin, or aerate and/or dry the material, then rebin.
Vertical grain silos On walls as adherent material (hang-ups) Use proper safety procedures for bosun’s chair.*** Dislodge adherent material working only above the obstruction (Fig. 12), or dislodge the material, using a whip device from above bin.
Railcars Within cars as compacted mass Wear a mask.* Dislodge and aspirate compacted material.
Ships and barges (in bags) On bag surfaces wetted by condensed water Wear a mask*. Remove and air-dry bags, then assess quality of stock.
Ships and barges (in bulk) Near surface under hatch joint as sprouted grains and in triangular area below Wear mask.* Separate caked and moldy material, using a shovel and aspirate the material or elevate it out in a bucket
In mid-bulk as full bridge or crust from seam leak or hull puncture Wear a mask.* Remove the bridge by aspiration, without mixing, then remove the grain beneath.
In lower or mid-bulk from water entering through ventilators or bilge control valves, then moving upward Wear a mask.* Use pneumatic or mechanical unloading equipment to move good grain. Probe for crust, remove the good grain above it and discard the crust and spoiled grain below it.
Table 8 – Handling and control of heating and fires in stored products
Type of storage Type of heating Handling or control method used
* Gas canister respirator, safety belts and ropes, two attendants
Outdoor piles Heating or smoldering fire Locate problem area, using a temperature probe, remove crust and heated material, cool.
Indoor piles As above As above. Keep dust levels low, remove by tractor bucket to outside of building, cool.
Farm bin or vertical grain silos Heating Locate problem area, using a temperature probe. If temperature is below 50°C, turn or aerate the stocks to cool off. If severe heating is occurring, do not aerate, as a flame fire may result.
Vertical grain silo Smoldering fire in ground animal feeds, pellets, or whole grains Do not disturb with pressurized H20 or foam because of danger of dust explosions. Wear a respirator.* Seal openings to reduce O2 supply, carefully purge contents with N2 or CO2, measure atmosphere in silo and work rooms, and remove contents when the O2 level is less than 10%.

When contents are cool, make a hole in the bin or silo wall at its base to allow the material to flow out.
Wooden grain elevator Flame fire Since the building usually cannot be saved, add water from a safe distance to diminish flames, but not to the grain itself to avoid spoilage. Save moveables such as accounting records. Avoid disturbance with pressurized H2O or foam. Use only a hand pump in the elevator.
Vertical silage silos (top and bottom unloading) Smoldering fire Do not add water or foam to fire through open-top hatches; place placards to warn fire fighters of explosion hazard; do not close roof hatches if steam or smoke is issuing forth or if silo is vibrating; close but do not secure hatches if silo is quiet and no steam or smoke has come out for several hours; inject CO2 or liquid N2 into silo, taking gas safety precautions to extinguish fire. See methods described by Murphy and Arble (1982), and NIOSH (1986).
Fires in dryers Flame fire Shut off heat and fan; if necessary, use water to extinguish the fire.
Shipping container Smoldering fire See methods described in R.J. Brady & Co. (1979), Nicholls (1984), and Chapter 6 of this manual.
Ship or barge Smoldering and flame fires For details of CO2, water, and other control systems used, see R.J. Brady & Co. (1979), Reanney (1969), Rushbrook (1979), and Taylor and Pucill (1982).

Spoilage problems

Numerous fungal and other spores are present on spoiled grains and grain products. During handling wear a mask, take breaks every 15 min to breathe in fresh air, and provide cross ventilation by fans. Entering bins, silos, and ships’ holds to handle problems requires safety equipment and other persons in attendance.

Outdoor piles

Grain is often stored unprotected on the ground in large piles for many weeks after harvest. A crust of sprouted and moldy grains may develop on the top surface and spoilage may occur within the bulk (Mills and Wallace 1979). First, separate the outer crust and any moldy clumps from non-moldy grains; later burn or bury this material. If necessary, dry the remainder of the bulk or cool it in a bin until a dryer becomes available.

Grain stored in open-topped or polyethylene-covered temporary bins is more prone to spoilage than when stored in metal bins. Most hot spots (and spoilage) occur in columns within 15 cm of the wall in both bin types, particularly in polyethylene-covered bins, during summer. Spoilage also occurs when water runs down the grain cone and enters depressions in the grain or small holes in the plastic. Separate the spoiled material from the good grain with a shovel (Muir et al. 1973).

Farm bins

Handling spoilage problems within farm bins requires careful consideration. Determine the location and extent of the spoilage by visually examining the product and by probing it to ensure that the most suitable handling techniques are used. When discovered at the early stages, spoilage can be controlled by transferring the product to another bin, aerating continuously until the temperature front is through the grain, or drying and rebinning. When spoilage is at an advanced stage, select remedial actions that minimize admixture of spoiled and non-spoiled material and damage to the bin and associated structures. Remove spoiled grains around doors, separate spoiled material beneath roof vents or roof holes from unspoiled material, then discard. If spoiled grains occur as a bridge or larger area in a bin or within internal auger systems, gradually remove the non-spoiled material to uncover the spoiled area. Remove this by aspiration, using a portable pneumatic grain elevator (Fig. 11), digging out and winching through an upper hatch, cutting hole(s) in the sides, or removing a metal wall sheet. Extreme care must be taken when removing grains from around blocked auger systems, as uneven pressure effects may result in the collapse of one or more bins and associated conveyor systems. If spoilage is extensive and the grains are cemented together by mold mycelium, use pickaxes, jackhammers, or even rototillers to break up the material. Remove spoiled material from above. It is possible to remove spoiled bin contents from below by using a front-end loader to lift the bin wall, then augering.

Portable pneumatic elevator for moving grain and grain products.

Figure 11 – Portable pneumatic elevator for moving grain and grain products.

Flooded bins

Determine the maximum water level attained, usually visible as debris marks on the outer bin wall or on nearby buildings, after flood waters have receded. Within the bin look for a layer of sprouted, moldy grains at or about this water level. Salvage grains above the sprouted layer before spoilage odors permeate the sprouted layer. Dry grains 5-30 cm above the sprouted layer. Bury or burn sprouted, moldy, and sodden grains (Mills and Abramson 1981).

Vertical grain silos

Early stages of grain spoilage can be controlled by transferring the product to another bin, aerating continuously until the temperature front is through the grain, or drying and rebinning. Advanced stages of spoilage are harder to handle and control. Grain tends to aggregate into a solid mass after storage in a moist condition as occurs, for example, when a moist carlot of grain is added to a silo of dry grain. When this occurs in the lower part of a silo or when unloading, augers become blocked by clumped grains. Remove the unspoiled product from above either by aspiration, winching material up and out, or via an exit made in the upper wall. Break up and remove the spoiled material in the same manner. Dislodge adherent material or hang-ups on the upper bin walls, using a bosun’s chair from above (Fig. 12a). Alternatively, use a special whip device operated by compressed air from outside the bin (Fig. 12b). Take extreme care when using the bosun’s chair. Dislodged material can bury anyone working at levels below the obstruction.

Removal of bin hang-ups

Figure 12 – Removal of bin hang-ups: A, bosun’s chair, showing upper safe working position and extremely hazardous positions beneath (after Boumans 1985); B, remote-controlled whip device (Northern Vibrator Manufacturing Co., Georgetown, ON).

Railcars

Spoilage can occur in railcars as a result of rain entering through open lids before loading, and in cars containing high moisture seeds that are mislaid in a siding en route to commercial drying facilities. In winter, spoilage occurs in cars of freshly pelleted materials with too much residual heat. Such spoilage results in adsorption of moisture and mold growth and makes the unload system inoperable. In such instances, dislodge the spoiled material either by digging or by using compressed air jets, then remove through the top hatch. Check for noxious gases and oxygen deficiency, and work in pairs, taking adequate safety precautions (National Safety Council 1962).

Ships and barges

Spoilage occurs on the surface and also deep within the holds of cargo vessels, bulk carriers (Figs. 13a, 13b), and barges in transit (Christensen and Kaufmann 1978). Spoilage may occur because of incipient molded grain, inadequate blending, too high a moisture, condensation, also known as ships sweat or cargo sweat (Knight 1985), or other reasons. Before unloading, remove with a shovel any sprouted or caked grains that are on the surface, together with any deeper triangular-shaped areas of spoiled grains beneath the hatch joints. With bagged cargoes, especially those transported from cold climates to hot ones, condensation and mold development may occur on the bags. Unload, dry, and assess contents of affected bags for quality and end use.

Midship sections of (A) cargo vessel, and (B) bulk carrier

Figure 13 – Midship sections of (A) cargo vessel, and (B) bulk carrier: A, electrical casing; B, pipe guard; C, fuel tank; D, wooden bulkhead; E, ladder; F, bilge area; G, ventilator; H, ventilator grill; I, trimming hatch; J, degaussing casing; K, cargo battens; L, limber boards; M, wooden ceiling (on bearers); N, propeller shaft tunnel; O, wing tank; P, McGregor hatch (open); and Q, hatch (closed) (after Monro 1969).

Spoilage that occurs deep within the holds of oceangoing ships is caused by water entering either through a weld or hull puncture or through ventilators or other deck openings (see Fig. 13a). In either situation, the water moves up to a certain level above which dry grains are unloaded mechanically or by aspiration. The amount of water in the hold, its location, and the length of time the grain has been wet are factors that determine whether the grain beneath is spoiled or not (see Table 7). Spoilage that occurs deep within the holds of lake ships is mainly the result of leaking cargo hold bilge valves, not, as in ocean-going ships, the result of leaking seams or hull punctures, because the cargo hold is separated from the hull plating by a double bottom and side tanks (H. Uustalu, pers. com. 1986).

In vessel transit, if the product is shipped too moist or too warm, spoilage cannot be prevented whether shipboard ventilation is used or not on the voyage (Milton and Jarrett 1970). Ventilation onto the surface of the bulk via deck ventilators is ineffective in controlling spoilage deep within the hold, is of doubtful use in controlling spoilage on the surface, and may aggravate spoilage if the air relative humidity is above 80% and the air temperature is above 25°C (Christensen and Kaufmann 1978). The most effective control method is prevention. Ideally, dry the shipments to safe moisture limits to prevent spoilage in transit, especially for long voyages (Milton and Jarrett 1970). The amount of kernel breakage affects the rate of spoilage in corn and must be kept low by careful handling (Paulsen and Hill1977). For information on the effects of condensation, and mold, insect, and mite damage in containerized and non-containerized ships cargoes see Knight (1985).

Heating and fire problems

Extreme care must be taken when handling and controlling heating situations in stored commodities in order to avoid fires and explosions. Avoid disturbance of heating materials with pressurized water or foam, as a dust explosion may result. Each situation requires evaluation at the scene by a safety engineer and specialized fire fighters to determine the optimal handling method. Table 8 summarizes methods used for handling heating situations in various types of storages.

Outdoor piles

Cereal grain piles may heat if left unprotected from rain for 2-3 months. Heating is likely in freshly harvested grain in piles larger than 1000 t because of seed respiration. It is aggravated by development of a sprouted surface crust, which prevents air circulation and facilitates heat buildup. First, determine the location of the heated area within the pile and temperatures involved, probably 30-60°C. Remove and discard the crust, then remove the heated material by tractor bucket and allow to cool in a 30-cm layer on a concrete floor. When cool, dry and bin or restack in a smaller pile until sold.

Indoor piles

Some conditions that cause pelleted feed materials piled in warehouses to heat and smolder are as follows: (1) accidental addition of water due to flooding or leaky roofs, (2) part of the stock being warmer than normal due to inadequate cooling, and (3) the presence of metal fragments heated during processing. Heating of pelleted feeds is aggravated by the presence of animal fats, oil seeds, or flammable contaminants in the pellets or on the floor, and on disturbance a heated pile may suddenly ignite. Grain piles are less likely to ignite but may do so, for example, when burning grain is conveyed accidentally from an earlier fire and incorporated into the pile (Boumans 1985). First, determine the location of the heated area in the pile and the temperatures involved. Avoid disturbing the piled material creating potentially explosive dust clouds. Remove the unaffected material, then the heated material, using a tractor bucket. Move the heated material from the building and spread it in a 30-cm layer to cool. Spraying heated grains with water is not advised (see next paragraph).

Silos

Handling of heating situations involving grain and silage stored in vertical silos is described in Campbell (1973), Fire Protection Association (FPA)(1968), and National Institute for Occupational Safety and Health (NIOSH) (1986), sometimes with conflicting advice.

NIOSH (1986) recommends that fires in silos be extinguished through injection of carbon dioxide or nitrogen. Water or foam should not be directed into the fire through the top hatches, since this may allow oxygen to enter the silo and cause the suspension of explosive dust (NIOSH 1985). For more information see the section on vertical silage silos and Murphy and Arble (1982). The NIOSH recommendations (1986) are for oxygen-limiting silos, but they could be applied to other types of vertical silo. If in doubt obtain professional advice.

Several years ago an explosion at a terminal in Thunder Bay, ON, was blamed on the creation of “coal gas” when water was introduced into the silo.

Farm bins and vertical grain silos

Fires occur after the aeration of materials in an advanced state of biological and chemical heating; when pelleted materials are binned together with hot fused lumps of aggregated material or hot metal fragments; or when smoldering or very hot material, originating from a fire elsewhere in the complex, is added to bins of unheated material. The following methods have been used to control smoldering fires.

Nitrogen (N2) Dinglinger (1981) describes (in German) a major fire that occurred in West Germany involving a silo of feed pellets, which was safely extinguished using 18 000-m3 of N2 gas over 10 days (Fig. 14). Dinglinger states that if a smoldering fire is discovered in a silo containing animal feed pellets or other coarse materials, the chimney effect created by the heat of the fumes will keep supplying fresh air to the fire. Fume condensates eventually cause the product to stick together, creating the risk of bridge formation near the source of the fire. Quickly emptying the silo without first purging with N2 or other suitable gas may cause the bridge to collapse and the dust raised to ignite. The following procedures are recommended for silo fires:

  • Seal openings at the base and floor of the silo as quickly as possible, including cracks along flange mountings. This cuts off or at least slows down the supply of fresh oxygen. Bridges may even be prevented from forming in the first place.
  • Purge cavities in the silo with inert gas. Install permanent nozzles for this purpose at the base and floor of the silo as a precautionary measure.
  • Monitor the atmosphere in the silo and adjacent work rooms.
  • Once the atmosphere in the silo is such that ignition is no longer possible (less than 10% oxygen gas (02)), clearing may begin.

Carbon dioxide (CO2) Boumans (1985) describes the use of CO2 for controlling smoldering fires in silos. After sealing the silo, CO2 is applied as a gas at a rate of about 1 kg/m3 silo volume. A valve is fitted to the silo hopper for entrance of the CO2 under pressure. Special precautions are required during application to prevent suffocation. Additional CO2 is applied every few hours to maintain the required level of gas at the top of the material. Smith (1982) gives complete instructions on how to use CO2 to control fires in Harvestore® oxygen-limiting silos.

Nitrogen purging of a smoldering fire in an 80-t feed mill silo

Figure 14 – Nitrogen purging of a smoldering fire in an 80-t feed mill silo: (1) intake chute; (2) filter bags with beater; (3) feed meal; (4) smoldering fire pocket; (5) lever for moving safety hood; (6) pressure hose connector for N2 intake; (7) N2 gas; (8) circular channel with drill holes; (9) outflow (after Dinglinger 1981).

Other

For silo bins with outside walls, a hole is cut in the wall above the fire to remove undamaged material, which is allowed to run very slowly into trucks or onto the ground. The disadvantage with pouring the material onto the ground is interference with operations at ground level. Meeker (1979) extinguished a fire in a silo containing soybeans by cutting an upper hole to remove undamaged material and a lower one to extract burning material. Do not use the existing conveyor system when discharging. For interstitial silo bins, install a temporary closed screw conveyor from the hopper outlet directly to the outside and discharge the bin in an inert atmosphere by continuously introducing CO2 into the conveyor, or better, into the bottom of the hopper near the outlet opening (Boumans 1985).

Never store discharged material that contains (or contained) heated fused chunks of material without a long period of cooling in a thin layer and close monitoring. This is particularly important when wooden structures are involved. Even when large chunks are removed by screening, small portions of heated material may remain, causing fires or explosions during handling and storage.

Vertical silage silos

Numerous fires and occasional explosions have occurred in the USA in vertical silos containing grass silage or haylage (Koegel and Bruhn 1971; Campbell 1973; NIOSH 1986). The sequence of events leading to an explosion in a bottom-unloading 6 x 18-m silo containing rye silage and first-cutting alfalfa hay of high moisture content are described by Singley (1968). Four days before the explosion, which lifted the structure’s 15-t concrete roof, the roof hatches and discharge door at the base were left open to receive more hay but this action created a chimney effect within the silo. At least 2 days before the explosion, the hay delivered by the unloader was noticeably charred. This charring produced flammable gases until the open flame combustion point of the moist hay was reached. The fire was extinguished with 9000 L of water. Note: Use of water to extinguish silo fires is hazardous (see next paragraph).

On 27 August 1985 three firefighters in the USA were killed when a burning oxygen-limiting silo exploded. The firefighters were spraying water onto the fire from the top of the silo when an explosion lifted the concrete silo roof, throwing them to the ground. The explosion was due either to a buildup of combustible gases from incomplete combustion or a dust explosion, or to a combination of the two. Opening the top hatches to apply water to the fire could have increased the level of oxygen and created an explosive atmosphere. Air entrained in the water stream may also have contributed to the explosion. Additionally, the water spray could have suspended the dust and increased the risk of explosion. Because of the improper fire fighting methods used and the lack of proper operating and maintenance procedures in this case, the National Institute for Occupational Safety and Health (NIOSH) subsequently issued a safety warning and the following recommendations (NIOSH 1986).

Fire departments are warned that directing water or foam onto a fire through the top openings of an oxygen-limiting silo may result In the silo exploding.

Recommendations for preventing fires and explosions in oxygen-limiting silos include the following:

  • Hatches should be kept closed when silos are not being filled or emptied. If the silo is properly sealed, the amount of oxygen trapped is usually insufficient to support a fire by self-heating.
  • Proper maintenance of the silo should be performed in accordance with the manufacturer’s instructions to ensure the integrity of the oxygen-limiting features.
  • The moisture content of stored silage should be controlled, as should the type of cut of the silage. Filling rates recommended by the manufacturer should also be followed to reduce the possibility of self-heating. A description of the elements of good silage is given by Murphy and Arble (1982).

Recommendations for fire control in oxygen-limiting silos include the following:

  • Water or foam should not be directed onto the fire through the top hatches, since this may allow oxygen to enter the silo and cause the suspension of explosive dust.
  • Placards should be placed on the silo warning firefighters that it is an oxygen-limiting silo, and they should include information concerning the proper extinguishing techniques.
  • Do not close open-roof hatches if steam or smoke is coming from the hatches or if the silo is vibrating.
  • Roof hatches should be safe to close if the silo is quiet and there has been no smoke or steam coming from the hatches for several hours. Do not secure the hatch. This will permit the relief of any subsequent pressure that may build up.
  • Large quantities of carbon dioxide (CO2) or liquid nitrogen (N2) should be injected into the silo to extinguish the fire. Some silos have valves specifically designed for this. If it is necessary to drill a small hole in the silo for insertion of the gas tube, care should be taken not to allow additional oxygen to be pulled into the silo. All handling precautions normally associated with CO2 or N2 should be taken. For a 6-m diameter by 18-m-high silo, 20 standard cylinders of CO2 or 40 standard cylinders of liquid N2 are required. For other silo sizes and amounts of gases required see Murphy and Arble (1982).
  • Manufacturers, in conjuction with the local fire departments, should establish a program to provide valves designed for injection of gases for fire control on all new and existing oxygen-limiting silos.
  • Certain manufacturers, for example Harvestore® Products (1982), have step-by-step instructions on how to extinguish fires in their silos. Farm owners should obtain these instructions from the silo manufacturer.

For further information on handling fires in vertical silage or other silos contact the National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, West Virginia; Tel. (304) 285-6017.

Dryers

Shut off the heat and fan to extinguish fire in a dryer. The fire may snuff itself out in a recirculating dryer if the auger is left running, but it is often necessary to use some water to extinguish it (Friesen 1981).

Ships

Control of smoldering fires in ship cargoes requires careful consideration, technical knowledge, and a well-trained staff using modern equipment. Management of such fires is made difficult in that they occur in complex moving structures strongly influenced by sea and atmospheric conditions, often at a considerable distance from outside help. Factors that apply on board ship differ from those which apply in a warehouse situation. This difference must be considered, otherwise both cargo and ship may be lost. Each cargo fire situation is unique and must be treated on an individual basis. The approach used to manage the fire is determined by whether the ship is in port or at sea. For a recent account of fighting a stubborn fire, probably caused by self-ignition of wet animal feed, in a general cargo ship at sea and in port see Fire Protection Association (1986). The reader is referred to the excellent books on the science of fire fighting on ships by Reanney (1969), R.J. Brady & Co. (1979), and Rushbrook (1979). Details on how to fight container fires on the decks and in the holds of ships are given in R.J. Brady & Go. (1979) and Nicholls (1984).

Nicholls (1984) outlines problems encountered when fighting dockside shipboard fires in Port Elizabeth, South Africa, and the procedures developed to combat them.

  • Communication problems, both in language and in nautical terms, often occur between firefighters and ships’ crews, complicating the efforts to extinguish the fires.
  • Each ship is different and firefighters are continually working in unfamiliar territory.
  • There is a constant need to be aware of the ship’s stability, a factor which determines the amount of water that can be used.
  • On ship arrival, fire fighters need to know the following:
    • What is burning (or believed to be)?
    • Where is the seat of the fire (or thought to be)?
    • What is the risk of the fire spreading from one compartment to another?
    • What steps have already been taken to deal with the fire?
    • What fixed fire protection is available?
    • What cargo is being carried? (The ship’s manifest or cargo plan should be produced.)

Open hold fires in early stages of development are tackled from within the hold, using high-pressure jets, or from the deck, using hose lines. Move the cargo onto the quayside by crane, then dampen down. If the fire increases, quickly batten down the hatches before they become heat distorted, and introduce carbon dioxide from the ship’s installation. Inspect adjacent holds, remove cargo from nearby bulkheads, and discharge additional carbon dioxide.

Closed hold fires are recognizable from smoke issuing from ventilators and hatches. Use high-pressure water lines to extinguish flames before crews, wearing breathing apparatus, enter the hold via the booby hatch to determine the extent of the fire and to inspect the bulkheads. Keep the hold closed to prevent the fire from flaring and possibly causing severe damage to the cargo and ship. Close and cover the ventilators with wet tarpaulins and discharge the ship’s carbon dioxide installation into the hold. Using dockside tankers, add more carbon dioxide to the affected hold via a small hole, enlarged in stages and drilled in the deck. Take a temperature reading by lowering a thermometer into the hold. Apply additional carbon dioxide every 2 hours, every hour if the temperature does not decrease. Apply cooling jets to the bulkheads and the ship’s sides. When the fire is out and the fire fighters and crew have inspected the hold, wearing breathing apparatus, introduce four high-pressure hose lines into the hold via the booby hatch and dampen the affected area before opening the main hatch. Continue dampening until the hold is certified free of gas, then have the cargo removed by stevedores.

Container ship fires are difficult to tackle. The vessels have a high freeboard, which creates an access problem, and they are inherently unstable. Water cannot be used because of its adverse effect on cargo and because of the stability problem. To solve the access problem use a roofless container that has one side removed to transport equipment and personnel to the deck by crane. Hoist medium-expansion foam-making equipment and concentrate to the deck and add the foam through vertical side hatches. Off-load the deck-stowed containers at the same time to gain hatch access. Open hatches and apply foam from the top, keeping side hatches closed. The affected container is usually located by a more rapid breakdown of foam and possibly the presence of an updraft. When the affected container is located, remove the surrounding containers and spray the damaged one, using high-pressure jets, then remove it to the quay (Nicholls 1984).

Salvage

After a fire, the safe removal of a product is done by salvage operators, who sort and subsequently screen the material to maximize its salvage value. This operation requires considerable experience. The services of salvage companies are retained by insurance firms when they are dealing with pertinent insurance claims.

Guidelines for salvaging products from grain elevators are as follows:

  • By the time a fire is discovered in a wooden grain elevator it is usually too late to save the elevator or product (see Fig. 18b). Devote efforts to moving railcars, protecting fertilizer sheds and adjoining elevators, and removing record books.
  • Add water to the fire itself to reduce its intensity and to other buildings. Do not add water to the grain itself. Wet grain is difficult to salvage and must then be separated and dried. Remember elevators often hold in excess of 6000 t of grain, but grain driers only operate at a rate of about 6 t/hour.
  • Do not apply water to the same spot for prolonged periods.

The most likely causes of fire in grain elevators in order of frequency are mechanical (moving parts, bearings, hot debris falling into dust, and so forth); lightning (look for melted copper rods as evidence); arson (look for pieces of a bottle that might have been filled with fuel and rags); electrical (motors, wiring, inspection boxes); and self-ignition. Self-ignition does not usually occur in small elevators and is more likely to occur with oilseeds or meals than with coarse grains. In large terminals, severe heating problems occur more frequently, as they are aggravated by large volumes of product, high pressures, closed-up spaces, and bin gases. A useful account of the salvage of grains and grain products is given by the Grain Dealers Mutual Insurance Company (1961).

Knight (1985) has compiled a general reference book for the use of cargo surveyors, adjusters, insurers, and others concerned with packing, transporting, and stowing commodities worldwide. Of special interest is the section describing the general principles to be observed when doing a survey on damaged goods.