With the general knowledge of the processes involved in the manufacture of tea appreciation of the fire hazards becomes a simpler task, but the variation between factory and factory, as well as between district and district, is so considerable that the underwriter must know not only details of construction and external hazards, but must also be able to appreciate and apprise the vital differences between the internal hazards.

TYPES OF FACTORIES

Factories are, broadly speaking, of two types only – those used for the purely mechanical processes, and those in which withering is also carried on, the latter beign storeyed buildings with the withering lofts above, and the manufacturing processes on the ground floor. The reason for this distinction is that the combined factory is so designed as to utilise the heat radiated from the firing room to assist in withering the leaf spread in the lofts above, but this artificial heat is used only when climatic conditions are such that a natural wither (i.e. by a current of fresh air) is impracticable. The factory having no withering lofts above will ordinarily wither its leaf in seprate detached leaf houses which are generally open-sided, withering being entirely dependent upon natural atmospheric conditions.

If follows that the type of factory suitable to the estate depends largely upon the geographical situation, and for those estates situated in hilly country, where mist and humidity are high for the greater portion of the year, the ‘combined’ type of factory is essential. In Ceylon, Southern India of factory is essential. In Ceylon, Southern India, Darjeeling, the Dooars (Northern Bengal) and the Kangra Valley, the factories are storeyed, whilst in Assam, Cachar and Sylhet they are ordinary ‘shed’ buildings, detached withering houses being used. In recent years, however, there has been a tendency to attach greater importance to ‘controlled’ withering system which necessitate the use of artificially dried air as well as fans, and although Assam gardens have hitherto depended upon, and resisted any temptation to dispense with, the natural withering system, there are indications that this condition of things may not always prevail.

The lay-out of the factory is a matter dependent largely upon individual taste or convenience, but is generally recognized that the rolling and fermenting processes should be effectively separated from the firing, packing and sorting rooms, as the atmospheric conditions suitable to the former are diametrically the opposite of those required in the latter. The ideal situation of the engine room is as near as possible to the centre of the drive, but in practice there is greater diversity in this respect than in any other. The following illustration accords very closely with the most modern ideas of a suitable arrangements :-

PRINCIPAL FACTORY UNITS

A. Humidification Plant.
B. Rollers
C. Roll Breakers.
D. Driers.
E. Engines.
F. Dynamo.
G. Packer
H. Tea cutter
I. Sorter
J. Fanner
K. Main shafting.

When it is explained that in the construction of tea factories it is usual for the walls to be of brick or corrugated iron or partly brick walls with wooden framework and extensive glass paneling, with roof of corrugsted iron over iron frame, whilst the wooden frames on which are stretched thousands of metres of jute (hession) cloth, it will be realised that the difference in fire hazard between a single and multiple storeyed tea factory is far more than in the average risk in which the ‘storeyed’ character merely involves considerations of height, stairways, chutes and other inter-storey communication. The heat conveyed to the upper lofts of a ‘combined’ factory, for withering purpose, makes the whole super-structure absolutely dry and this together with the hessian withering racks (often called ‘tats’) average degree. There is an added danger in the tea fluff and fibre, which penetrate to every corner and crack in the word work. This is referred to later.

Before leaving the question of factory construction, it should also be explained that whilst the construction is occasionally inferior to that described in the preceding paragraph, it is never superior thereto in India or Ceylon. Java is understood to have some excellently designed tea factories of ‘massive’ construction. but India and Ceylon have hitherto adopted the cheapest and most easily constructed type of building compatible with manufacturing requirements. However recently in India also such factories of first class construction are coming up.

WITHERING LOFTS AND HOUSES

The fire hazard in this section depends very largely upon the material of which the racks, which are some 5 or 6 inches apart, and stand in tiers 8 feet to 10 feet high, are constructed. If of wire-netting on frames of angle-iron (as opposite to jute cloth on wooden frames), the risk is obviously substantially reduced, but, unfortunately, from a fire insurance point of view, this type of withering loft is rarely found outside Assam, and then only in leaf houses of the detached and open sided type.

The following illustration will give an idea of the Assam open-sided leaf house, which consists of a steel framed, corrugated iron-roofed structure with two or three lines of racks running the entire length of the building (generally from 100 to 150 feet in length), with gangways between the racks, and a stair-case at each end. The leaf is withered by natural air currents through the open sides, and where wire mesh is used, the racks are sloped towards the gangways to facilitate removal of the withered leaf. The tendency in recent years has been to revert to horizontal hessian racks, as greater importance is attached to adequate withering, and so this end the hessian racks are considered more effective.

END ELEVATION SHOWING TWO LINES OF SLOPIG RACKS (AS FITTED WHEN WIRE MESH USED) AND ONE LINE OF HORIZENTAL RACKS (AS FITTED WHEN HESSIAN CLOTH USED)

The favoured type of rack in the combined factory is that with wooden pillars, the edges of rack being formed by tightly stretched galvanised wire. To these wire edges the hessian cloth is attached, and forms a very cheap and easily is type of rack for carrying green leaf. The leaf is only spread thinly on the racks (about 15 square feet to the pound of green leaf), and it is both easily distributed and easily removed without bruising the leaf. These advantages, coupled with the fact that no fire-resisting substitute seems to be available at other than a prohibitive price, explains why the considerable fire hazard represented by the use of hessian is perpetuated.

In the detached withering house, surreptitious smoking or cooking by the labour force is usually found to be responsible for any fires that occur.

In the combined factory with withering lofts, the hazard from surreptitious smoking by the labour force remains, but, when examining the dangers arising out of the readily combustible nature of the lofts, other points that have to be considered are :
(a) Electrical short circuits;
(b) Sparks from drier furnaces or exhausts.
(c) Friction sparks from shafting, fans, etc.

Where fans are used to assist or control withering, the fire hazard is substantially increased if hot air from the drier is being used, since these fans have the effect of spreading a small outbreak so rapidly that efforts at extinguishment are rarely effective. This aspect is further discussed in a later paragraph dealing with hot-air systems.

ROLLING AND FERMENTING ROOMS

There is virtually no inherent fire hazard in the rolling and fermenting processes, as the atmosphere is humid, and the leaf damp.

FIRING ROOM

The firing room is probably responsible for the very large majority of the fire losses, and these seem to arise in two ways :
(a) Careless firing or mechanical fault in the drier furnace.
(b) A spark from the drier exhaust.

It is not difficult to imagine the dangers arising from the drier furnance when, as not infrequently happens, the stove is erected inside the factory or in open communication therewith. These dangers are multiplied when air circulating fans are working in the factory, (and possibly insurers have hitherto not attached to this factor the importance which it undoubtedly deserves). The only safe arrangement is for the drier stove to be in a separate fire-resisting compartment, any communication with the factory being limited to the minimum amount necessary for pipes or shafting. This lessens very considerably the danger arising from sparks from the furnace door, and, where oil fuel is used, from broken oil pipes or a “blow back”.

A spark from the drier exhaust can originate in two ways :
(a) From a mechanical fault in the stove which allows a spark from the furnace to leak through into the air flues, and thence through the drying chamber.
(b) Ignition of fluff in the drier tubes through over-heating of the furnace, due to careless stocking

The first of these dangers is probably greater in those areas where manufacture is not seasonal but continues throughout the year, the reason being that in a factory where manufacture is seasonal there is opportunity for annual examination and overhaul of driers. Where manufacture is continuous – as in Ceylon and Southern India – little more than superficial repair work may be done until such time as the stove is in a condition that renders general overhaul imperative. It is all the more remarkable, therefore, that in Northern India, which has the advantage of a “silent” season, it is the rule rather than the exception to employ qualified engineers, than the exception to employ qualified engineers, whereas in Ceylon exactly opposite conditions obtain.

The average coolie’s idea of stoking is to fill the furnace to capacity so that the longest possible period will elapse before the operation need be repeated, thereby extending his “leisure” period (mostly spent in sleep). It is little wonder, therefore, that firing is erratic, and stoves become overheated or damaged.

One of the greatest hazards in a tea factory arises from the fluff and fibre, which is discharged from the drier exhaust or the machinery in the sorting room, finding its way into every nook and crevice in the factory. The hazard lies in the fact that combustion of tea fluff is very slow and a spark has the tendency to form an ignited core rather than burn on the surface, only bursting into flame when sufficient heat has developed. This is considered to be the probable explanation of fires having broken out in tea factories some hours after work for the day had stopped.

Cleanliness in a factory may not altogether eliminate the dangers from the tea fluff, but will reduce it to a minimum. Tests have shown that fluff will only commence to char at 300 deg. F., and that the ignition point is about 400 deg. F. so that a spark from the driers or from an electrical short circuit would be necessary to start combustion of fluff. The particular characteristic of tea fluff in relation to the fire hazard is the tenacity with which it will hold the spark, and the slow combustion which follows.

SORTING

The fluff and fibre seprated from the tea in shifting operations is the only point of interest to the fire underwriter is the only point of interest to the fire underwriter in this section of the factory. There are various dust extracting systems in use in factories which make a striking difference in the deposit of fluff in the sorting room, but it is not possible entirely to eliminate the danger. It is strange, however, that this portion of the factory has, never been suspected or known to be the seat of origin of a fire.

PACKING

The process of packing might, in the earlier days of tea manufacture, have warranted particular attention as box-making and soldering were not entirely free from fire hazards. Comparatively few factories now use other than 3 ply wood chests with patent aluminium or lead or polythene sheets linings for packing, for which no sewing or soldering is necessary, and this portion of the factory is not now important as a potential danger. However excessive storage of shooks or boxes present storage hazard and the student will observe that the tariff itself stipulates an additional rate for storage in excess of 25% of the annual requirements.

POWER UNITS

The very large majority of factories in India and Cevlon now utilise the cold-starting crude-oil internal combustion engine, although a few factories keep an old steam engine and boiler for stand-by puposes, oil engines are always housed in a separate compartment, for the primary reason that tea is exceptionally and cleaning oils all give off an unmistakable odour. The fire hazard within the engine room is not particularly great, as the fuel has a flash point of about 185 deg to 200 def. F., and a burst cylinder head is perhaps the main hazard in a well constructed and cleanly kept engine room, though it is important that the oil supply should be housed in such a manner that in case of accident it could not flow into contact with the dryer furnace or the like.

The exhaust may in certain circumstances be dangerous in a storeyed factory unless it is so constructed as to discharge away from the factory or is carried well above the eaves. The danger arises from incandescent pieces of carbon being discharged, due to faulty combustion or worn cylinders.

The old type of crude oil engine had a hot bulb starter and it is not difficult to imagine the danger arising from careless handling of the blow-lamp in a compartment where oil and oily waste may be lying about. It must be ill-educated coolies with minimum requisite knowledge to start stop and lubricate the engine, so that trouble may arise in a manner that would be considered quits improbable in other than an Eastern Country.

A clean dry atmosphere is very desirable for electrical apparatus, apart, of course, from provision of a separate “electric” house. Yet it is not infrequently found that this equipment is installed in the firing room, or rolling room, with the result that insulation troubles are almost certain to ensure. The safe-guard from an insurance point of view is that the danger would ordinarily only arise when the factory is working, so that any electrical fault would then be immediately detected.

LIGHTING

Where electricity is installed, the workmanship, maintenance, and testing are of vital importance, as the potential dangers are less obvious than with oil lamps. It must be remembered that the varying atmospheric conditions in a factory, from approximately saturation point in intense heat, call for the best in materials and workmanship, and the heavy condensation under normal atmospheric conditions in the tropics is responsible for rapid and often unsuspected deterioration of electrical installations. The greatest safety factor lies in the complete shutting down of the installation when work in the factory ceases, so that, unless a fault has already set up slow combustion in tea fluff or behind woodwork, the installation is ‘dead’, and not a potential danger.

The periodical testing and examination of electrical circuits constitutes the only safeguard under working conditions. The general practice of replacing a burnt out fuse by a higher size by uninformed mechanics is to deprecated. In many old factories open type wiring are used both for lighting and power. Only rigid conduit or armoured cable wiring should be used in tea factories. All the electric motors should be of totally enclosed type.

HOT – AIR SYSTEMS AND DUCTS

Ducts are sometimes fitted in storeyed ‘factories for the purpose, during wet or misty weather, of utilising in the withering lofts the exhaust air from the driers which are, of course, located on the ground floor. These ducts are usually made of metal sheets, and , if they discharge directly into the lofts, may increase the fire hazard, since a spark from the dryer exhaust could reach the highly combustible withering racks without being observed. The fluff and fibre which are exhausted from the dryers tend to collect in the ducts, and thus provide a readily combustible medium which a single spark may convert into an incandescent mass, the draught in the duct doing the rest.

It is, of course, possible for ducts to be so constructed as to discharge downwards on to a non-combustible floor, and to be readily accessible for cleaning purposes. Without knowledge of the particular arrangement adopted (and ducts vary very considerably), it is generally correct to regard them as an undesirable arrangement in a tea factory from the insurance point of view.

The recent system of controlled withering depends upon a central air-bulking chamber into which the hot air from the dryer room rises or is drawn by fans, there to be mixed with fresh air in a predetermined ratio. From the central chamber the air is forced or drawn through the withering floors and discharged out of a window (opened specially for the purpose), as it will by then absorb no further moisture from the system of utilising hot air for weathering, as installed in many Ceylon factories, the title arising from the reversal of the air flow by means of fens and to trap doors in order that the degree of wither throughout both lofts should be as even as possible.

Air flow from firing room to central chamber ‘G’ is set up by Fan ‘M’ and is thence directed through any loft or combination of lofts assisted, if necessary, by fans ‘H’ & ‘J’. The Diagram shows air flowing through ‘C’ to ‘A’ and thence to atmosphere through
open window ‘K’
The Reverse of the above Air-Flow is shown through ‘D’ & ‘F’ and thence to atmosphere through open window ‘L’

It will be seen that if the dryer exhaust is too close to the central air chamber, the danger of sparks being drawn up unnoticed is enhanced, but, speaking generally the possibility of fire in a storeyed factory of the most modern type is less EXTERNAL FIRE HAZARDS

The tea factory building may include various ancillary compartments for office purposes, stores and box-making, but these are more often detached buildings, and not “within risk” of the factory. Similarly, where natural withering is done in separate leaf hoses, it usual for these buildings FIRE EXTINGUISHING APPLIANCES

With very few exceptions – so few as to be almost negligible – no tea factory in India or Ceylon is equipped with other than hand appliances, however, there are some sprinklered tea factories. Of those equipped with buckets and patent extinguishers, the majority are only casually protected, according to the ideas of the individual estate proprietor or superintendent, and are not equipped according to insurers requirements.

Lack of interest in fire fighting equipment may be due to lack of awareness as well as the idea held in certain quarters that even a complete automatic sprinkler installation would not save a storeyed factory fitted with hessian withering racks once the fire reached the hessian withering racks once the fire reached the hessian cloth. This idea is fallacious. The spread of fire in banks of hessian “tats” is certainly rapid. Sprinklers would confine the damage to little more than the hessian cloth, and that the building – even if the framework were of wood construction – would not be affected other than in a purely superficial manner. The great – and at the moment almost inseparable – difficulty is the high cost of the sprinkler installation compared with the value of the property protected; even a limited single water supply system is frequently found to be an uneconomical proposition. But automatic sprinkler protection is the only answer since :
(1) One of the primary difficulties in the majority of tea estates is the provision of adequate water supplies for fire fighting equipment, as the water available is often little more than the minimum necessary for engines and other essential services.
(2) Proximity of the location of fire brigade which may be located far away in the plains.

The value of hand appliances depends upon the speed with which they are brought into use, attacking the outbreak in its incipient stage. The extinguisher is specially useful for dealing rapidly with overhead fires, such as those arising from electrical faults, and it seems unfortunate that a larger proportion of tea factories are not equipped with hand appliances.

SUMMARY

Knowledge of the very combustible style of construction, the hazards incidental to the manufacturing process, and the want of technical supervision in the larger majority of tea factories, leads one to wonder why, the fire loss ratio has been so moderate. More often than not, an outbreak of fire in a tea factory results in a total loss, and it is to an element of luck, such as the direction of the wind, or the presence of the staff at the very inception of the fire, that one may attribute those escape from complete destruction which do occur.

The difficulties attendant upon the installation of other than “first aid” fire fighting equipment are shown in the preceding paragraph, and the insurer has necessarily to concentrate upon the measure taken for prevention of fire, such as maintenance of equipment, cleanliness, careful supervision in the factory, and the elimination of hazards form external sources.

Two case histories or actual fire occurred in Tea Estates aro given in the next lesson to give practical illustrations to the student.

CASE HISTORY

1. Tea Estate, Vandiperiver :

Construction Details :

The factory building was having ground, and 2 upper floors. The intermediate floors were of timber construction and wooden false ceiling was used at the top of each floor.

An employee of the Factory noticed a fire coming out of the withering loft and raised an alarm. Within minutes, the fire was out of control. The entire factory was engulfed. Within half an hour the intermediate floors collapsed and were completely gutted. Only twisted mass of steel work, severly burnt down electric motors and buckled and bent up machinery parts were the remains in the debris. The tea stock stored in the premises was also completely burnt. The total loss was estimated to be Rs. 25 lakhs.

Following are the reasons for large loss :
(a) Absence of water for fire fighting.
(b) Absence of Fire Fighting Equipments.
(c) Untrained Workers.
(d) Combustible materials were used as building materials.
(e) Huge accumulation of stock in the process area.

2. Tea Estate, Nilgiris :

The factory building was of class II construction with ground and 2 upper floors. The intermediate floors were of wooden construction. Wooden materials were used extensively as building material.

Fire was due to the escape of sparks from the furnace through drying chamber to the withering lofts. Fire became out of control because hot air suction fans were in operation. The estimated loss was Rs. 17 lacs.

Reasons for large loss :

(i) Intermediate floors were of timber.
(ii) Wooden ducts and bulking timber were used for passing flue gases from drier to withering lofts.
(iii) Unprotected structural steel framework added to the collapse of structure.
(iv) Storage areas were not segregated from process area.
(v) Huge accumulation of tea stock in process block.
(vi) Absence of water, storage facility and fire fighting equipments.
(vii) Fire brigade people were not familiar with the risk.

TEA FACTORIES

1. Draw a typical layout of tea factory and describe the hazards associated with construction thereof.

2. Discuss the fire hazards in withering lofts and withering houses. How can they be minimized?

3. What are the hazards associated with firing rooms? How can they be reduced?

4. Discuss the hazards of power units in tea factories.

5. Write about the essential features of good electrical installation in a tea factory.

6. Describe the hazards posed by hot air systems and ducts.

7. What are the external fire hazards encountered by a tea factory?

8. What type of fire extinguishing appliances are recommended for a tea factory?

9. Describe the reasons of large losses in tea factories. What are the remedial measures?

10. Discuss in brief, the process of tea manufacturing and hazards associated there-with.

Leave a Reply

Your email address will not be published. Required fields are marked *

  • two × 2 =