Category: News

Plastic

INTRODUCTION

There are at least 45 generic families of plastics, and thousands of variations¹. New compounds and processing operations are being developed continually. It should be noted that actual operations may vary greatly from risk to risk, depending on the type of resins and product involved. However, although the machinery and techniques used to shape plastics are extremely varied and custom operations performed are often unique. The many different processes do have some elements in common. Most use heat to soften the plastic so that it can flow and pressure to force the molten material into the mold cavity or through a die. For the purpose of this assignment, a brief outline of the most commonly used plastic conversion processes namely molding and extrusion is briefly discussed.

PLASTIC

Plastic is any one of a large and varied number of materials consisting wholly or in part of combinations of carbon with oxygen, hydrogen, nitrogen and other organic and non-organic elements While it is solid in the finished state, at some stage in its manufacture it is liquid and capable of being formed into various shapes through the application of heat and pressure.

There are nearly 45 basic families of plastics, each with numerous subdivisions and distinct characteristics. However, whatever their properties or forms, most plastics fall into two groups namely thermoplastics and thermosets.

Thermoplastic resins can be repeatedly softened and hardened by heating and cooling without any chemical change take place. While Thermoset resins, cannot be resoftened by further heating without some alteration to the plastic’s chemical composition.

PLASTIC CONVERSION

Plastic processing involves the conversion of plastic resin into shapes and end products. Generally, the plastic industry can be divided into three sub-industries namely secondary petro-chemical production, plastic fabricating & finishing and plastic moulding forming and extruding (also known as plastic products manufacturing.

Secondary petro-chemical products – entails processing primary petro-chemicals (e.g. ethane) that have been extracted from crude oil and transforming them into secondary petrochemicals (e.g. ethylene).

Plastic fabricating and finishing – entails processing secondary petrochemicals (e.g. ethylene) into solids, synthetic resinous compound (e.g. polyethylene), better known as “raw plastic” (or plastic resin).

Plastic moulding, forming and extruding – entails the shaping of raw plastic (e.g. bulk polyethylene) into finished products (e.g. plastic cups, auto-body parts, etc) that are sold to public.

In relation to processes commonly adapted by Malaysian plastic industry, conversion is commonly done by moulding, forming and extruding.

The processes involve heating of resins so that it will flow into shape when the plastic is cooled.

PROCESS
Injection Moulding


Figure 1: Diagram of typical injection molding machine

Plastic resins in form of pellets, granules, flakes, powders, liquids and pastes is first mixed with various additives3. It is then pumped into the injection molding machine through the hopper. The compound is then brought to a molten state in a heated barrel. The quality of the end product made from the plastics depends on the temperature maintained during the process. The temperature condition depend upon the structure of material being pressed and the manufacturing features involved in the making of the products. The barrel can be heated by steam, gas or electric heaters. But electric heaters are most common. It can be found in three varieties namely resistance, induction or semi-conductor types.

The reciprocating screw inside the barrel will compacts, melts and pumps the molten plastic through a non-return flow screw where it is allowed to accumulate. The rotation of screw is then stop and the molten plastic is then hydraulically injected into a mold located at the end of the barrel. Injection Molding mold is normally made of unhardened steel or non-ferrous alloys. It can be classified under 2 categories namely compression mold and transfer mold. In compression mold, the die accommodates the loading chamber and the bottom shaping cavity. The material is charged into the die in which it is heated and then pressed by the punch. The punch transmits the pressure upon the material and shapes the top and the internal surface of the products. Whereas in transfer mold, the loading chamber and the shaping cavity are the separate units and both are completely clamped prior to fill it with the molten plastic. There are two types of transfer mold namely with or without a loading chamber. Transfer mold without a loading chamber is generally used in the injection machine.

Once the molten plastic flow throughout the cavity of the mold and completely fills it. The plastic is then cooled off rapidly by using circulated water. Once the materials is hardened, the mold is opened and the finished product is removed/ejected. The process of removing the plastic products from the mold can be either done manually or by a robotics arm. Some products may require spray painting and/or silk screen printing.

Plastic Extrusion

 


Figure 2: Diagram of typical single screw extruder

This method is employed to form thermoplastic materials into continuous sheeting, film, tubes, rods, profile shapes or filaments and to coat wire , cable and cord.

In a basic single screw extruder, plastics pellets (or powders) are fed through the hopper into a screw that rotates in a heated barrel. The rotation of the screw, which is normally powered by the drive motor, convey the plastic forward for melting and delivery through the breaker plate and adapter into the die which dictates the shape and size of the final extrudate. In some industries for example plastic bag manufacturer, the extruded plastic is blown to produce continuous hollow sheet. This sheet will later undergo a printing process normally by using solvent based ink.

THE BEHAVIOR OF PLASTICS IN FIRE

From the above table, we have seen that plastics are combustible to a greater or lesser extent and in the event of a fire easily fall prey to the flames.

The plastics industry has identified this fact and has succeeded in developing plastics that are difficult to burn. It is possible to incorporate foreign atoms into the plastic molecule which bring about such an effect for example it can also be achieved by adding flame retardant agents. Practice did show that, although such agents prevented ignition of the plastic. But in many cases where plastic is not the primary cause of fire, the flame retardant will largely lose their effect if a fire does in fact occur. This is explained the fact that when subject to a thermal load, plastics give off combustible decomposition products which in turn help to spread the fire. In many cases the flame-retardant agents are also decomposed and lose effect. It has proven to be more effective to incorporate foreign molecules, such as phosphor, antimon or halogone. Paradoxically, it is precisely here that the great danger lies, as the primary fire damage can in fact be quite small but the consequential damage can exceed all proportions. Halogenised plastics such as PVC decompose under the effect of heat (please refer below).

Once plastics have caught fire and the fire intensity is high enough, they mostly burn very quickly indeed with a very high heat production as most plastics have very large calorific values. As they burn, they release products such as smoke, soot, toxic and corrosive gases. Precisely the commonly used plastics such as polystyrene or polyvinyl chloride and almost all rubbery materials are very strong producers of smoke which can, for example, hamper the fire brigade in their fire-fighting and life saving actions, even rendering it impossible, or could lead to escape routes filling with smoke, making them unusable.

HALOGENATED PLASTICS AND THEIR BEHAVIOUR IN FIRE

Halogenated plastics are plastics which contain one or several halogens, halogens being the four elements fluorine (F), chlorine (Cl), bromine (Br) and iodine (I). In practice the following plastics have gained special importance:

  • polyvinyl chloride
  • polyvinylidene chloride
  • chloroprene
  • chlorinated rubber
  • chloroisobutylene
  • chlorinated polyolefins
  • foam-plastics containing bromine
  • plastics containing fluorine

The most common chlorinated plastic is polyvinyl chloride (PVC). PVC is the polymerization product of vinyl chloride, therefore in its usual form PVC contains approximately 50% chlorine (by weight). For it various application purposes, plasticizer, pigments and colorants are added to give flexible PVC. PVC without or with few additives is considered to be difficult to burn or even self-extinguishing and many experiments have shown that these properties actually do exist. When plasticizer or other agents are added this property can disappear. Plasticizer can promote combustability in that they are released under the effect of heat and burn on the surface. PVC is thermically stable up to approximately 180°C, then decomposition sets in and hydrochloric acid is given off.. PVC decomposes forming HCl, CO and CO2, as well as minor quantities of different organic products of combustion. The immense consequences of PVC fire are clear when it is considered that the decomposition of 1kg PVC gives off approximately 550 grams of pure HCL gas. Under normal conditions this corresponds to a quantity of approximately 1.2 kg of concentrated aqueous hydrochloric acid or approximately 330 litres HCl gas.

The HCl gas which is given off in the decomposition of PVC or other chlorinated plastics combines with the water vapour and moisture to form the moist aerosol of hydrochloric acid. This condenses on surfaces which are below the dew point temperature of the acid aerosol, thereby causing a corrosive effect. Tests have shown that the gas phase reaction takes place considerably more slowly than than the reaction in the liquid phase. This is also confirmed by observations which show that the corrosion damage to materials in the immediate vicinity of the fire area and whose surfaces consequently also have high temperatures is considerably smaller than with cold surfaces which are exposed to the HCl attack. Through the condensation of hydrochloric acid metals with blank surfaces corrode practically immediately.

THE BEHAVIOR OF FOAMS IN FIRE

Foams assume a special position as regards their fire hazardousness. In recent years there have been repeated spectacular fires in plastics foam factories giving foams the general reputation of being a fire hazard. It should be stated that this comment is only correct to a limited extent. Foams have a general tendency to burn very quickly. This is explained by the fact that most have a very low weight per unit of volume (10-50 kg/m), i. e. only about 1-5% of the volume is solid. In the pores which at the beginning mostly contain only incombustible propellants (halogenized hydrocarbons, CO2, etc.), these gases are exchanged for air by diffusion. After some time there is then an almost ideal fuel/ air mixture to aid combustion, whereby the fuel (plastic foam) is relatively well distributed (thin cell walls). Therefore a relatively slight amount of heat is needed to set the foam on fire. This heat is often supplied by the electrical filaments with which the foam is cut, thus giving rise to the fires in foam-processing factories. More and more foams are being made with the inclusion of so-called flame-retardant which considerably reduce the ignitability.

There is a further cause of fire in factories which produce foam plastics from polyurethane especially where large blocks are foamed. By altering the polyol/isocyanate ratio in the mixture, uncontrolled chemical reactions can occur in certain parts of the foam blocks. Since these reactions are highly exothermal (heat producing) and foams are good insulating materials and do not conduct the heat, so-called nucleus burning zones develop, i.e. the stored heat can give rise to glowing nests. If these are not discovered, a fire becomes a certainty. Very often the blocks are stored in a warehouse which naturally then becomes a victim of the flames.

HAZARDS IN THE PROCESSING OF PLASTICS

The raw and semi-finished products needed to process finished products are supplied by the petrochemical industry in the form of liquids, powders, granulate, chips, pastes, etc. The basic materials are processed into finished products by a variety of methods from processing by hand to a computer-controlled fully automatic plant. The hazards that arise during fabrication are not necessarily specific to plastics, even though an increased fire hazard often arises from the fact that the quantities of combustible material handled can be quite considerable in plastic plants.

PHYSICAL HAZARDS

Plastics factories are subject to a variety of hazards that can result in explosions and fire. The board area of hazards involves the presence of large stockpiles of flammable raw materials and finished products, heating of machinery due to faulty or malfunctioning wiring and electrical equipment, static electricity discharges, excessive mechanical friction, overheated process machinery, grinding operation, dangerous quantities of explosive plastic dust, hot work, hydraulic and heat transfer liquids and most importantly, failure to observed good storage and housekeeping practices.

Explosions.
Although when in a solid massive form many plastics can be difficult to ignite. However nearly all will burn rapidly in the form of dust and if dispersed in air can be explosively ignited by spark or flame.
Plastic pellets for injection or extrusion molding are commonly known as molding powder. They are usually screened to remove finer particles to permit more uniform feeding to machines and dust can be generated by abrasion of these particles when conveyed in the pneumatic system.
Trimmings from injection molding are normally cut to small size. The process is known as regrinding. Regrinding process normally generates some fine powder.

Flammable solvents.
Flammable organic solvents are found in nearly every plastic plant. They are widely used in painting and coating process. There may be increased hazard when solvents are applied to plastics particularly when printing or coating on fast moving films because plastics usually have high electrical resistivity and they generate and retain static charges.
Improper handling of flammable liquids has caused serious fires in plastics plants. Failure to recognise the importance of static spark prevention, explosion proof electrical equipment and vapour removal system has been the most frequent causes of flammable liquids fires.

Heating elements.
Molding and extrusion operations have hazards associated with local overheating of electrical components. Operating temperatures normally range from 149°C to 343°C depending on which plastic is being processed. Materials which remains in these heated areas can be subject to exclusively high temperature and may release combustible vapour. Cleanliness in molding and extruding areas is vital to reduce the hazard of ignition from overheated bands where flammable vapours may be generated.

Static electricity.
Many operations in plastics plants generate static electricity. Since plastics is a good electrical insulator, static electricity on them can rapidly can rapidly build up to spark discharge. This can creates a hazardous condition if dust or flammable vapours are present. Operations which can generate static are stripping of films from production or printing equipment, rapid passage of films across rolls or guides, belts for power transmission etc. Attention should be given to grounding of equipment. Care should also be given to separating vapour and dust from machines where static electricity ignition sources could develop.

Hydraulic pressure system.
Hydraulic system are used to clamp molds and to provide pressure to rams or screw which force molten plastic into molds by injection molding. Ignition of lubricant fluids may be resulted for the application of high pressure.

Storage arrangements.
The fire hazards of plastics in storage are determined by their chemical composition, physical form and storage arrangement. the hazard of a particular plastics in any form of storage arrangement is the same whether it is encapsulated or non-encapsulated. If fire occurs, large quantities of smoke are usually generated, making manual fire fighting difficult. High sprinkler discharge densities over relatively large areas are necessary.

The following table gives a summary of the classification for common plastic and its combustibility and smoke intensity:

    Material Combustibility Smoke Intensity
    ABS IV Yes
    Celluloid II No
    Celluloid acetate IV – V No
    Chloroprene rubber IV – V Yes
    Epoxy resin III, IV – V Yes
    Melamin (formaldehyde) resin V No
    Phenol (formaldehyde) resin V Yes
    Polyacrylonitrile III No
    Polyethylene III – IV No
    Polyamide IV No
    Polybutadiene III – IV Yes
    Polycarbonate IV – V Yes
    Polychlorobutadiene IV – V Yes
    Glass fibre reinforced plastics (UP) IV – V Yes
    Polyisobutylene III – IV Yes
    Polymethylmethacrylate III – IV No
    Polypropylene III – IV No
    Polystyrene III / IV – V Yes
    Polytetrafluoroethylene V No
    Polyurethane III / IV – V No
    Polyvinyl chloride, flexible IV – V Yes
    Polyvinyl chloride, rigid V Yes
    Foams (depending on basic material) III – V No

Source: CEA “Materials & Goods, Hazard Evaluation

Factors
I     Very highly flammable & burning rapidly
II    Highly flammable & fast burning
III   Highly combustible
IV   Moderately combustible
V    Low combustible
VI   Non-combustible

MORAL HAZARDS

Here again the hazard situation is characterized by human inadequacy. An additional factor is that there is a considerable loss potential, particularly in large, fully automatic plants since plastics. Machines are not exactly cheap. However, in such plants, as a rule the necessary experts are available who are also trained in loss prevention and fire fighting. Moreover considerable investments are made in safety installations.
More dangerous is the proliferance of small and mini-plants where, because of the relatively simple methods, non-experts process plastics from raw materials whose properties they do not fully know, if at all. Often the necessary safety measures are lacking, mostly for financial reasons or know-how.
The exposure to loss stands and falls-not only in plastic plant, but sometimes with the interest the company management or rather the proprietor displays in safety. Thus there is a typical risk picture which the inspector often finds in plastics enterprises:

  • rooms which are too small and crammed full ; no compartmentations
  • expensive machine park
  • high fire load
  • plastics which release dangerous combustion products
  • lack of or incorrect safety measures
  • ignorance or lack of interest of the company management for loss
  • revention
  • financially “tight” situations
  • relatively low insurance premiums
  • “I’m insured” mentality

This list shows that there is a broad field of activity for the loss prevention specialist. The condition is that he has enough experience to determine and build upon the possible factors in every situation. Such plus points are:

  • every manager, proprietor is proud of his plant
  • every manager wants to produce
  • no plant can afford a loss.

Although insurance covers the material damage and the loss of profit, loss of market, increased advertising costs, personal involvement in restoration, social concerns of the staff all remain a matter of the company. It is therefore not surprising that many and particularly small companies disappear from the scene in the first two years after a fire.

PROTECTION MEASURES

It is no simple matter to establish general protection measures that apply to every plastic enterprise since it must be assumed that every plant looks different. To work out a tailor-made protection concept it is necessary in all cases to carry out first a risk analysis which should reveal all week points and hazards of a plant.

Despite all the varieties of individual plants there are a series of general protection measures. These can be divided up into four groups: construction, operation, defense and loss reduction (see table). Limitation of fire spread, fire prevention, fire fighting and salvage are among the terms mentioned. There is already enough literature on these field, therefore only the individual categories are commented on here.

Structural Protection

Structural fire protection is the main means of limiting the spread of fire. The principle factors necessary for the safety of buildings are briefly:

  • the fire behavior of building materials ( e.g. burnt clay, plaster, cement, steel, wood, glass, plastics, etc.);
  • the fire resistance of building parts such as support constructions, walls, ceilings, supports, doors, stairwells, etc;
  • the formation of fire compartments by means of fire-resistant vertical and horizontal separations;
  • the installation of smoke and heat extraction units;
  • the sealing of wall and floor openings, pipe and cable ducts, etc. with an appropriate fire-resistant material;
  • protection for neighboring buildings by the correct façade construction or by appropriate distances;
  • securing the rescuing of persons and the extinguishing action by the fire brigade by correct design of escape and approach routes.

Operational Fire Protection

Here the main factors are:

  • safe design of production flows and production installations such as separate facilities for energy production (firing, heating, ventilation) and for product manufacture (paint spraying installations, cleaning baths, heating, baking and drying furnaces, dust filtering systems);
  • ensure electrical installations which correspond to the occupancy of installations and plants (e.g. explosion proof);
  • correct storage of dangerous and exposed goods and materials;
  • good order and housekeeping;
  • trained and competent safety officer (supported by a safety group, etc.);
  • training staff to work safely and adhere to it;
  • constant monitoring of operations, acknowledgement of circumstances which contravene safety and elimination of shortcomings;
  • permanent surveillance of operations even during non-working hours by own or commissioned guard service:

Defensive Fire Protection

  • securing water supply by own or secured external means such as tapping and ground wells, fire water ponds, tanks, public water supply, etc;
  • securing the distribution of water by means of ring water mains, pumps, etc
    working out of an alarm and emergency plan, which stipulates alarm procedure, conduct in the event of a fire and measures after the fire;
  • the training of staff in how to use the company’s own fire-fighting installations;
  • the formation of a fire-fighting group or company fire brigade;
  • organization of rescue operations for persons and property, neighboring aid, etc;
  • installation of fire detectors, fixed fire protection installations (sprinkler, CO2 total flooding system, Halon, powder) to protect the entire plant or as particular protection for individual machines or installation.
Fire Protection
Structural Fire Protection Operational Fire Protection Defensive Fire Protection Salvage
Faultless design of building and installations, from fire protection point of view Safe design of process and product flows, storage, etc Securing water supply Organization of “salvage” group
Separation of dangerous and undangerous processes Safe technical installations(electricity, etc.) Organization of fire Alarm Prevention of consequential damage by removing water, soot, corrosive gases, etc
Limitation of fire spread Training of staff in safety matters Saving of people and property Restoration of building and machinery
Installation of smoke and heat extraction units Continuous monitoring and elimination of faults and short comings, etc Training staff in fire-fighting Restoration of fire protection installations
Organization of guard services safety engineers, safety audits, etc Organization of mutual aid and public fire brigades Gradual start-up of operations
Periodical control of safety installations Fixed fire protection installation (sprinklers, deluge systems, etc)
Installation of early warning systems (smoke detector, etc.)

Source: Plastics – Swiss Reinsurance Company

Composite Panels

INTRODUCTION

Composite panels incorporating combustible cores and without adequate fire resistance, have been a source of concern to insurers for many years. More recently, large fires which has occured in the food industry have heightened this concern. See Appendix I – Large Losses.

A “composite” panel comprises an outer and inner metal skin with a core of insulation sanwiched between. An authentic composite panel is factory made and delivered to site ready for fixing, but “split construction” also encountered, which comprises similar components, erected separately on site.

This “paper” address the technical information on the various types of composite panels, guidance for the selection of acceptable products and loss prevention measures applicable where both satisfactory and unsatisfactory composite panels are encountered.

Composite panels are frequently found as external wall and roof claddings, mainly to industrial buildings, but are also used as claddings to commercial buildings. Most incorporate combustible cores (rigid polyurethane predominates) and lack satisfactory overall fire resistance.

Similar panels (denoted as “food industry panels” by this paper), but usually incorporating significantly more insulation, are used throughout food industry in manufacturing, storage and distribution risks, e.g. coldroom. Their insulation cores are mostly combustible expanded polystrene or rigid polyurethane. Through increasing demand for frozen and chilled foods, their overall use has greatly increased in recent years. Also improved food hygiene regulations and other demands have resulted in significantly increased use in production areas, where inception risks are often enhanced, e.g. deep fat frying, and combustible packaging maybe concentrated.

Consequently, in boot food manufacturing and storage risks, is now common to find such panels in considerable use as internal walls (as: lining to external structure walls and/or as partitions) and as suspended ceilings, above which are extensive voids containing services, include refrigeration plant. These panels may also serve as external structural walls of food industry buildings.

OUTER AND INNER METAL SKINS (FACINGS) [top of page]

The profiles of outer and inner skins may be similar or dissimilar and are steel and occasionally alumunium.

CORES [top of page]

As manufactured, most composite panel cores are exposed on at least two edges and total encapsulation during manufacture is virtually never found. However, fixing methods usually result in the cores not being readily visible, particularly where a lip is provided on a panel which overlaps the adjacent when erected.

Therefore, for existing buildings, surveyors can only do their best to identify the core within a composite panel.

Where positive identification is not possible, it is best to err on the safe side and describe the core as combustible.

See Appendix 2 – Composite Panels Cores, for details of the combustible and non-combustible cores which may be encountered.

LOSS PREVENTION [top of page]

General Building Applications (excluding “food industry panels”) AND Food Industry Panels.

Where we have the opportunity to specify materials for new buildings, preference should be given to having entirely non-combustible panels, listed in the LPC list of Approved Products and Services. However, panels with basically combustible cores but fire resistant which have been similarly listed by LPC are acceptable.

We should also actively encourage our Insured to replace existing unsatisfactory panels, where general refurbishment is not planned.

Even in the longer term, partial replacement, but concentrate in the “priority” buildings or areas is obviously better than none.

As for “food industry panels”, the most readily acceptable alternative products are the ones that incorporate mineral fibre cores.

OTHER LOSS PREVENTION PROGRAMME [top of page]

SURVEYORS TAKE NOTE!

Below are Loss Prevention Measures to be applied to all buildings containing composite panels, ranging from those with entirely satisfactory panels, to those buildings containing the most combustible panels.

A separate section is devoted to measures applicable to food industry buildings.

  • Facing and joints must be maintained in good repair, to prevent exposure of combustible cores to ignition sources, to maintain the fire resistance of non combustible panels to prevent fire too easily spreading into any voids behind the panels.
  • Appropriate precautions are necessary for any heater flue or other potential hot trunking which passes through panels.
  • Repairs involving welding or other obvious ignition sources must never be permited to composite panels, or in their vicinity unless properly protected by non combustible or purpose made blankets, drapes or screens.
  • Particularly important that yard storage of combustible is not againts or whithin risk of walls containing composite panels.
  • Exposed bottom edges of external panels (e.g. where they occur above dwarf brick walls) to be closed off with steel cappings wherever practicable.
  • Sprinklers and/or sub-division by fire break walls should be considered, but there are particular difficulties for food industry buildings, see below

In addition to those above, the following loss prevention measures apply to food industry buildings.
Sprinklers and sub-division should be considered for all such buildings.

  • Sprinklers will greatly improve risk, but care need to be taken to position heads for full coverage of voids, such as those between the structural external walls of buildings and inner walls of composite insulating panels. However, it will be found that installation costs are usually prohibitively high for existing factories, mostly due to the need to maintain hygiene during installation and the considerable area of voids requiring sprinklers. The installation of sprinklers in sub zero temprature areas has aditional high cost implications.
  • Sub-division employing fire break walls may be approprite to limit material damage and/or business interruption losses, but costs will be enhanced in exisiting factories, again of hygiene reasons if construction occurs whilst production continues. Alternatively, although less effective sub-division maybe more easily attainable by employing the most fire resistant composite panels systems available.
  • Automatic smoke detection (or heat detectors where appropriate), with reliable signaling for prompt brigade response are to be installed in at least those areas rarely visited, such as roof void plant rooms and roof voids in general.
  • Hazardous process (e.g. deep fat frying) in close proximity to composite panels in walls are to be relocated, or improvement obtained by the additional of linings of one hour (minimum) fire resistance, to extend beyond the hazardous process areas. Also, similar lining applied to ceiling above and well beyond such processes are necessary, regardless of their location. Better still compartment all such processes with non-combustible walls and ceilings of 1 hour fire resistance minimum; doors and their openings to be similarly rated and fitted with self closures. Include fixed extinguishing system (e.g. gas spot protection for kitchen hood) and also thermostats/high temperature limit controls.
  • Apply at least similar standards to last, to compartment hazardous plant areas, such as those for refrigeration and heating equipment, especially where located within roof voids.
  • Relocate fork lift truck battery recharging to safer buildings or areas.
  • Increase periodic electrical examintation and test frequency to “annual” to reflect proximity of equipment and cabling to unsatisfactory panels.

CONCLUSIONS [top of page]

The presence of large amounts of unsatisfacoty composite panels results in heavy risks, even where the inherent trade hazards are low. Serious losses have occured in the food industry when fire has rapidly spread through paneling, to engulf entire buildings.

Improvements by diligently applying the loss prevention advice contained in this paper to both existing and new buildings is highly recommended. However, the difficulties associated with obtaining the most significant risk improvements, such as sprinklers or sub-division for exisiting buildings in the industry, are acknowledged.

APPENDIX 1 – Large Loses [top of page]

Typical of the many serious losses which have occured in the food industry are:
Meat Processors, Milton Keynes : 1989.

      Walls of external metal clad steel; internal double skinned steel sheet infield with polystrene. Estimated loss 2.9 million pound sterling. Supposed cause electrical fault or heat from gas fired boiler.
      Fire destroyed a meat processing plant, which had little compartment to halt its progress, and where the insulated internal walls assisted the fire spread.

Bakery, Dronfield: 1989

      Overheating of frying oil led to ignition of nearby composite panels containing polystrene. The fire, which including business interruption cost 7.5 million pound sterling, quickly spread through the entire section of the building via simillar wall and ceiling panels.

Backery, Spain: 1990

      False ceiling of double skinned metal with core of polyurethane sandwiched between. Loss of 15.8 million pound sterling including business interruption. Fire occured in the extract flue of a doughnut fryer which then ignited the polyurethane infill of the false ceiling.
      Fire subsequently spread and destroyed the whole of the building.

Poultry Processors, Uckfield: 1991

      A fire in a disused oven quickly spread into a ceiling of composite panels containing polystrene. The fire engulfed both production and ancillary areas. Loss of 5.5 million including business interruption.

Poultry Processors, Cullompton: 1992

      Almost all of the main buildings were destroyed in a fire which swept through this modern poultry-processing and storage plant, aided by the presence of polystrene in-fill in the walls and ceilings. Estimated loss 4.9 million pound sterling. Supposed cause short circuit in electrical wiring.

Poultry Processors, Hereford: 1992

    A serious blaze which is believed to have involved large areas of combustible composite panels devastated this modern processing plant for breaded and battered chicken products. The damage is said to have run into millions of pounds. Unconfirmed reports suggest the fire originated in a refrigeration unit. Tragically, two firefighter died during this blaze.

APPENDIX 2 – Composite Panel Cores [top of page]

An “*” denotes the cores most likely to be encountered in modern products.

The undernoted cores are combustible:Rigid Polyurethane (P.U.R.)

      *

 

      The most commonly encountered. Made by reaction of a hydroxl group of polyester, polyether, or polyalcohol with diisocyanate. Usually treated to provent ignition by low heat source, but a larger flame will ignite and spread rapidly, with abundant smoke and toxic decomposition giving off hydrogen cyanide, oxides of nitrogen and carbon monoxide, Ignition temprature 416

o

      C.

Rigid Polyisocyanurate (P.I.R)

      A modified polyurethane reasonably resistant to all but large ignition source but smoke and decomposition similar to P.U.R.

 

      Generally, fire performance is superior to P.U.R., but this does vary quite widely depending in the formulation of individual products and the quality control.

Foamed urea-formaldehyde

      Little mechanical stability. Brief duration flames for a short distance from ignition source. Charring of surface prevents sustained flaming.

Phonetic Foam* (As yet uncommon, but likely to increase)

      Not easily ignited by a small ignition source. Some types exhibit smoldering or glowing after extinction of ignition flame. Generally superior to polyurethane or polyisocyanurate as regards rate of burning, evolution of smoke and burning droplets.

Expanded Polystrene*

      Made by impregnating polystrene heads with pentane, which are then steam heated. Melts and shrinks away from small heat source. Severe flaming and rapid emission of heavy black smoke/soot if exposed to a large heat source. May produce flaming droplets. The addition of flame regardent does not make it non-combustible. Ignition temprature 490

o

    C.


The undernoted cores are non-combustible:
Expanded Purlite

      Lightweight loose fill siliceous glassy rock of volcanic origin.

Expanded Vermiculite

      Loss fill lightweight exfoliated material made from flaky stone, closely resembling mica, also available in board form.

Mineral Fibre*

    Made from glass fibre, slagwool, rock fibre, or rockwool. Addition of resin binders enables the fibres to be formed into blankets. Regardless of addition of binders, the product is for all purposes non-combustible.


- by Mahendran

Plywood and Veneer

intended for exposure to the weather, and varying heat and pressures, are required for proper curing.

The panels are stacked on top of each other separated by a piece of lumber (to provide ventilation gaps in between) for at least 4 hours to allow for complete setting of the adhesive. They are then trimmed to exact sizes and sanded to produce the desired finish. Where necessary the panels are patched or plugged with small pieces of veneer and resanded. Finish panels are graded, packed and marked before they are sent for storage. Metal bands are used to strap the panels together; strapping is done either manually or with automatic equipment and can be done prior to stacking in the warehouse.

The Fire Hazards and Safeguards

Because of the combustibility of the contents and buildings in some cases, extensive damage to both the building and the contents is possible.

Fire hazards include:

1. large quantities of fire dusts in the finishing department where the plywood sheets are given a finish which uses sanders;
2. other waste materials generated in the early stages of preparing the veneers for assembly into finished plys;  
3. combustible hydraulic fluids in some process machinery;  
4. flammable adhesive products; and
5. stored finished products.


Potential ignition sources include welding and cutting operations; heat-producing equipment such as dryers and presses, smoking, faulty electrical equipment and human carelessness.

In order to minimize these hazards, careful attention should be given to preventive measures. Cleaning of waste should be done by a vacuum sweeping apparatus to minimize the scattering of dust. Sanding appliances should be fitted with integral exhaust equipment (pneumatic cyclone extractor) to remove dust generated from them.

A suitable mechanical or pneumatic conveyor should be used to transport trimmings from the clipping process area so that no hazardous buildup of combustible materials will occur.

Grinding and milling equipment requires regular inspection to prevent bearing failure, loosening of parts or internal breakage; any of these accidents may cause sparks or heat buildup sufficient to ignite the wood dust. Certain vapours, such as formaldehyde vapours emitting from urea-formaldehyde or phenol-formaldehyde which is used as adhesive, are flammable in the air. The insured must take the necessary precautions to eliminate possible sources of ignition from places where these vapours may exist.

Any welding and cutting done in the plant should be supervised directly. All working areas must be thoroughly cleaned and wet down before hot work is conducted and wet down again after the job is completed.

Veneer dryers require special attention, as the temperature within them approaches the nominal heat of ignition for wood. Dryers should be inspected frequently and cleaned to remove any accumulations of dust and fibres that may ignite.

Hot presses used for consolidating the plywood and partial glue curing are potentially hazardous. Hydraulic fluids leaking or flowing from broken lines may be ignited by an immediate or distant ignition source. Easily accessible shutoff valves on the hydraulic fluid reservoirs of the presses can minimize flows in emergencies.

Smoking also is a cause of fire loss; it should be strictly prohibited in all manufacturing areas. Designated smoking area equipped with ashtrays such as rest rooms which are free of combustible materials should be provided.

Electrical fires are fairly common. Inspection and maintenance of machinery must be done on a regular basis.

Above all it must be bore in mind that safety precautions should extend from log yards to storage areas.

Care should be taken to ensure that there are adequate clear separation and aisles between log decks to prevent fire spread and to permit access by mobile fire fighting units.

Industrial trucking equipment used to move logs should be refueled and serviced in areas that are isolated from the storage area. Yards should be situated in cleared areas and at least 100 feet from the nearest building forming part of the factory.

Fire control systems

The most effective extinguishing medium for a wood based fire is water. This can be applied in various forms. Automatic sprinkler protection for the entire plant is preferred over the others to protect against the hazards associated with high fuel loadings, such as those represented by the stock storage and the manufacturing process. However the high cost of installing the system may make it unjustified.

Yard hydrants is the most appropriate in terms of cost effectiveness. For reliability, it is preferable for the ring main system to be installed.

Strong water supplies are needed to supply the hydrants. One major manufacturer of wood products requires a minimum flow of 1,500 to 2,000 gpm (gallons per minute) or 5678 to 7571 liters/minute at about 100 psi (690 kpa) for at least three hours. A good primary supply would be automatic fire pumps taking suction from ground reservoirs or ground storage tanks supplemented by elevated tanks or reservoirs or a connection to a public water supply.

Other supporting appliances are hose reel and portable fire extinguishers. Hose reel system can be taped off from an existing hydrant system or installed as a system on its own. Water supply should be pump-fed although there may be many of those which are gravity fed from elevated water throughout the premises on an area basis ie. 1 x 2 gallons water type or 1 x 10 lbs. Dry Chemical Powder or its equivalent for every 2,250 square feet of floor area. They should consist predominantly of the water type with several units of dry chemical powder or BCF (Bromochlorodifluoromethane) type for electrical and oil or flammable liquid fires.

It is important to remember that the fire fighting equipment is only part of a fire control system. It would available on each shift who are capable of handling these equipment in the event of an emergency.

Chipboard
Raw Materials

Chips, shavings and sawdust, the principal raw materials for chipboard are delivered to the plant by truck or conveyed from adjacent woodworking processes. They are usually stored in open-bay buildings.

Free-fall dumping of incoming materials and retrieval by front-end loaders can put wood dust into suspension and create an explosion hazard.

Some protective measures should be taken to reduce these hazards. The raw material, when possible, should be prescreened to remove small particles or ‘fines’ that could be potentially explosive later in the production process. The fines may be stored as fuel for dryer equipment if the plant has a burner or boiler that can handle wood waste. Removal of the fines at this point also helps to minimize the accumulation of dust throughout the plant.

The Production Process

Briefly outlined, the production process starts with a grinding operation to mill the particles to desired size. After grinding, the particles are dried and screened to remove fines and return oversized particles for further grinding.
The particles are then dried and mixed with a resin, such as urea-formaldehyde or phenol-formaldehyde, and a preservative and then formed into boards or panels.

Grinding

The first step in making chipboards is to grind or mill the chips, shaving, etc; to the desired size in hammer mills. But before the materials enter the grinders and mills, they should pass through separating equipment (magnets, air dropout, etc) to remove ‘tramp metal’ or other foreign objects which might cause sparks or machine failure.

Drying

Drying of the milled and ground material is necessary to assure correct and uniform moisture content.

This is done in dryers which may be heated directly by fossil fuels or wood dust from the plant’s own sanding and screening operations or they may be directly heated by steam from boilers heated by either of the above fuels. Spark detection/suppression systems backed up by high temperature switches at the dryer inlet and outlet provide good protection. High temperature switches set approximately to 50º F (28º C) above normal maximum temperatures can shut off the heat source and material infeed and outfeed, and triggers and emergency alarm.

From the cyclone collector at the end of the drying operation, the raw material may go to a separator for segregating fines and larger particles. This separation takes place in plants where different boards are manufactured or where layered board is made with large chips in the core and finer materials on the face. The dried and separated material is stored in bins or silos before blending and forming.

Forming

Forming machine may be of the tray type or the extrusion type.

In try forming, the mixed wood particles and resins are metered by weight or volume onto an open tray or box where, through a high vacuum arrangement, they are formed and pressed into board shape.

In the extrusion process, the mixed materials are forced between heated platens.

The properties of the finished products will depend upon the size and orientation of the particles and the method used to produce the board.

The tray-type method tends to orient the particles with long dimension approximately parallel to the face of the board, while extrusion leave the particles randomly oriented.

Pressing

From the forming boxes, composite panels go to the hot presses where they are further consolidated by pressure.

Under the heat, the resin liquefies, flowing around the wood particles. As the resin is thermosetting, it soon solidifies to form a solid sheet of wood.

Sanders

In the final production stage, the boards are cooled and sanded as part of the finishing operation.

Finished panels are graded and packed before they are sent for storage.

The Fire Hazards and Safeguards

The fire hazards involved are quite similar to those present in a plywood and veneer factory. Refer to previous notes under PLYWOOD AND VENEER.

Fire Control Systems

Refer to notes under PLYWOOD AND VENEER

Summary
Plywood, veneer and chipboards or particle boards plants are inherently susceptible to fires which may result in injury or death to employees and extensive property damage. The hazards can be reduced by one or more preventive or containment measures. Among these are:

1. Prevention of dust and wood waste buildup by good housekeeping.
2. Minimizing ignition sources by eliminating spark-producing mechanisms, static electricity and well maintained electrical installation.
3. Installing spark detection/suppression, temperature control switches and other fire suppressions systems where necessary.
4. Isolation of burning materials e.g. burners or steam boilers by use of airlocks, diverters and flash-back dampers, etc.

These may be considered as preventive measures which should be used where applicable to reduce the hazard. They cannot be completely relied upon to prevent fire or explosion, but will help to minimize the consequences.

The extent to which any of them should be utilized will depend upon the degree of hazard, personnel exposure, proximity of adjacent structures, cost and feasibility.

Some Studies on Fire at Hotels and Shopping Centres

Hotels

Most large hotels are of high-rise buildings. Compared to high-rise buildings with multiple occupancies, there are certain particularities that have to be considered for hotels.

Firstly, hotel guests are normally not familiar with the building and its emergency and protection features since they stay there only for a short period of time. This is one of the major reasons for the high number of injuries and fatalities during hotel fires.

Secondly, hotels have good internal compartmentation because the guestrooms are separated from each other by massive walls. This prevents an internal fire spread. However, the fire load in hotels is of entirely different nature compared to the fire load in an office building. In office buildings, the fire load is normally quite high due to files, office furniture and office equipment. However, the fire load in the corridors is normally low since public areas often have marbles or other stone floors and wall claddings. In hotels, normally the fire load is rather equally distributed throughout all guestroom floors. Wall cladding in corridors and wall-to-wall carpets in the guestroom areas represent quite often a significant fire load.

Thirdly, in respect of safety standards, hotel buildings are entirely managed and controlled by one managing company. No tenants are present as it is common in office or apartment buildings where different tenant occupies different part of the building. Therefore, in multi-tenant buildings, the building management company has only limited influence and access to the privately occupied areas.

Loss Prevention Concept for Hotels (and High-Rise Buildings)

1. Fire resistant construction

Either concrete or steel structures with fire-resistant coatings should be used throughout.

2. Non-combustible building materials

Only non-combustible building materials should be used throughout. This applies especially for insulation materials e.g. at air-conditioning ducts, suspended ceilings, temporary fixtures and dividers as well as for pipes and ducts.

3. Fire walls

All openings in fire walls, like door openings, ducts, pipes or electrical cables penetrating the walls should be sealed in a fire-resistant way. Utility areas include areas such as electrical, chiller, boiler and generator rooms. Emergency staircases should in addition be equipped with pressurization system which should be activated automatically in case of emergency.

4. Fire resistant sealing of installation risers

All vertical installation risers (electrical risers, water supply pipes, air-conditioning ducts, etc.) should be sealed in a fire-resistant way on each floor level to prevent a vertical smoke and fire spread.

5. Mechanical heat and smoke ventilation system

Thick smoke is a major problem for the fire fighting attempts of the fire brigade. Therefore, it is of utmost importance that an effective heat and smoke ventilation system is installed. This is especially important in atrium-like buildings.

Shopping Centres in South-east Asia

It can generally be distinguished between so-called “first class” and “second class” shopping centres and department stores in South-east Asia. Some of the “first class” shopping centres reach international standards for which they are fully sprinklered and adequately managed. However, the risk quality of the “second class” shopping centres can sometimes be extremely poor. Some of them can even be described as uninsurable risks. Most of the “second class” shopping centres are not or only partially sprinklered and in various cases an automatic fire detection system is not installed.

Compared to most of the developed countries, fire detection and fire fighting installations are often not reliable in various South-east Asian countries. There were several cases where sprinkler systems in shopping centers were not operational for a long period of time due to management deficiencies. Valves were closed, sprinkler pumps were switched-off without reasons or pump panels were not permanently manned or were damaged. Wet risers were not pressurized and hoses and nozzles were missing from the hose reel cabinets. As a result, high-value fire protection investments were made useless due to poor risk awareness and lack of management commitment.

In most industrialized countries, automatic fire detection and fire fighting systems are regularly checked, tested and approved on a large scale by the respective authority, independent bodies or associations related to the insurance industry.

According to the German and international statistics from other western countries, about 98% of all fires in sprinklered areas could be either controlled or extinguished by the sprinkler system. These impressive results are mainly related to the design standards and strict supervision of the systems in these countries.

The risk quality of shopping centres in South-east Asia depends very much on the “human factor”. This is the main factor that influences the overall risk quality. There are no process hazards involved in this occupancy and therefore, the risk is often underestimated. The poor attitude normally starts on a management level and as a consequence, the safety organization of the respective risk is unsatisfactory. This often leads to the above-mentioned deficiencies regarding the maintenance of fire protection installations as well as to structural deficiencies such as blocked fire doors or unprotected openings in fire walls. In addition, poor housekeeping standards, problems related to hot works are a result of indifference towards risk awareness. However, there are also shopping centres and department stores within South-east Asia that are very well organized and the management has a full understanding for the need of a comprehensive risk management concept.

Example of Losses at Shopping Complex

1. The Mall, Ngamwongwan, Thailand (October 20, 1995)

The complex consisted of an 8-storey shopping centre of about 145,000 m2 and an office tower on the top of about 25,000 m2. It was a fire-resistant concrete structure with massive walls and concrete ceiling and roof slabs.

The fire was caused by an electrical defect in a shoe shop on the first floor at about 1.00 a.m. It was detected by a security guard soon after. Upon arrival of the fire brigade, smoke has already spread from the building. Due to heavy smoke, fire fighters faced difficulties to fight the fire from inside the building. The fire was supposed to be under control by about 3.00 a.m. The General Manager of the shopping mall ordered the fireman to stop their activities but shortly after, the fire unexpectedly rose up again and the second fire quickly ran out of control. At 11.00 a.m., some concrete floors collapsed and by 3.00 p.m. on October 20, the fire was finally extinguished. More than 50 fire trucks and 100 firemen were involved in the fire fighting activities.

The fire water supply was insufficient and the hose reels of the fire brigade did not match to the hydrants. In addition, the fire fighters were not allowed to enter certain parts of the building.

The overall loss was about 700 million baht which equals to about 40% of total sum insured.

2. Central Department Store, Chidlom, Thailand (November 22, 1995)

The department store was a 7-storey building with one level of basement carpark. A central atrium linked all levels. The lower floors up to the 3rd floor were of fire-resistant concrete structures with pre-casted ceiling elements. The 4th until 7th floor was a steel frame construction with concrete floors and a steel sheet roof. The building had a square shape with a floor area of about 9,000 m2 per level. The building was not sprinklered but heat and smoke detectors were installed.

The fire was caused by an electrical defect in a shoe store of the 3rd floor. A desk light was not switched off and the fire started from the extension cord of the desk light due to a short circuit. The fire was detected by a security guard at about 9.10 p.m. The fire brigade was alerted and arrived shortly after. After 1.00 a.m., the fire was extinguished and most of the fire trucks left the premises. Executives of the insured inspected the building at about 3.00 a.m. and found that the fire had broken out again on the 5th floor. The fire ran out of control and the fire brigade could only extinguished it more than 24 hours after it was initially discovered.

Four officials were killed and 14 were injured when the ceiling on the 6th floor collapsed while they were inspecting the building interior on November 24 in order to remove undamaged stocks.

The loss for property damage and business interruption is about 1,150 million baht which is equal to about 74% of the total sum insured.

Above is the summary on seminar title “Fire Protection and Risk Assessment of Industrial and Commercial Risks” conducted by Andreas Kleiner, Chief Fire Engineer, Munich Re (Singapore) on January 3, 1999 at Parkroyal Hotel, Kuala Lumpur. You can contact FPAM for the full seminar note.