11. SPECIAL OPERATION CONSIDERATIONS


11.1 Care and cleanliness
11.2 Personnel working in cold stores
11.3 Safety
11.4 Security
11.5 Instruments
11.6 Energy management and conservation


This document is not a full manual of the operation of cold stores, some information on factors of special interest and importance are given below.

11.1 Care and Cleanliness

Close attention to care and cleanliness will minimise loss of quality, and the risk of introducing food poisoning micro-organisms.

Good handling practice should begin on board fishing vessels and be carried through to consumption. The fish should be stowed as soon as possible after catching, but always in a clean condition. Guts, trash fish, etc., should be kept separate and not allowed to contaminate fish for storage or processing. Offal and refuse should be kept away from processed fish and there should be an adequate system of disposal. All plant and equipment, fish rooms, containers, tables, etc., should be designed for case of cleaning, and they should preferably be made of non-corroding, washable material, especially where in contact with fish. They should be kept clean by frequent washing. Care must be taken in the choice of cleaning and sterilising materials and methods.

Personnel should be trained to understand the causes of food poisoning and to practise high standards of hygiene. Coughing, sneezing, spitting, smoking and some minor injuries are potentially dangerous. Proper toilet and washing facilities are essential. Suitable clothing must be worn and kept clean. Personnel should be medically free from diseases.

All facilities and operations should be checked regularly with regard to care and cleanliness. The importance of high hygienic standards at the cold store cannot be overemphasised. In order to assure that storage facilities are continuously maintained in a manner which satisfy both company and regulatory agency standards and regulations, a store quality assistance audit should be scheduled on a regular basis and followed point by point. One example of such a quality assurance audit is given in Appendix 3. Obviously such a programme must take local requirements into consideration.

11.2 Personnel Working in Cold Stores

Working in a cold store means exposure to extreme cold and demands high physical and mental standards. Heat losses from the body must be minimised by proper clothing. In addition, working in a low temperature environment creates special effect on the human body, which must be counteracted by a special working routine and provisions for personal welfare. As for anybody else working in the food industry, the employees must undergo regular checks and maintain the necessary level of personal hygiene required for this industry.

Among the initial effects of exposure to low temperatures are numbness in the fingers and toes and reduction in dexterity. Muscular activity and increased metabolism would help to maintain the body temperature around 37C. On average, the heat dissipated by a man in W/min varies according to the physical activity e.g. at rest 1.5, light work 2.5-3, moderate work 4.5-5 and hard work 8. Shivering is the principal mechanism of the body to momentarily increase its metabolism, but a shivering worker becomes ineffective, when the heat losses are greater than the heat generation, the body temperature will continue to fall and thus causes unsatisfactory physical response. It is usually considered that the metabolism will decrease by 12 percent for every 1C decrease of the body temperature. The lungs begin to freeze at about -53C. The human body will lose liquid through cold when exposed to low temperature. However, working in a low temperature environment is not hazardous to health, provided the worker is physically fit, i.e., submits himself to the necessary medical examination before employment and uses all the precautionary measures provided by the cold store properly.

11.2.1 Protective clothing

The term clo was introduced in order to define the insulating quality of clothing assembly. By definition, one clo will provide thermal comfort to a man sitting in an ambient of 21 C, 50 percent relative humidity and 0.1 m/s air velocity. A long suit corresponds roughly to one clo, a linen suit to 0.8 clo, and a woollen suit under which is a waistcoat, shirt and underclothes to 1.3-1.5. One clo is equal to 0.18 C m2 h/kcal. In polar climates 3 clos generally are considered suitable for moderate activity in a -20C ambient with a low wind velocity. However, this relates to selected individuals and for similar conditions in a cold store a value of 4 clos may be considered necessary. The importance of correct clothing is shown in Table 25, which shows the relation between ambient activity and heat production.

Table 26 Metabolic rates for various activities

Activity Total heat production in watts
Sleeping 80.5
Sitting 117.2
Typing 161.2
Walking slowly 263.7
Shovelling sand 536.2

Physical activity therefore has a significant bearing on the type of clothing worn. Clothing with a value of 4 clos will effectively protect a man at rest in an ambient of 0C or carrying out moderate work in an ambient of -30C. Thermal protection of only 2 clos would be necessary for heavy work in an ambient of -40C. If dressed in too heavily insulated clothing staff could be susceptible to a heat shock when doing heavy work in a cold environment.

The insulating value of the air layer surrounding the subject varies with the air velocity. The face is particularly sensitive to very cold air circulating at high velocity. Special clothing is always designed to be windproof.

The protective clothing for personnel working in cold stores should be properly tailored to the body and dimensioned to the work. The latter aspect is very difficult to achieve, as the intensity of work varies. The needs and preferences of individuals also vary. While ensuring good thermal protection, clothing should not be too thick, too stiff or too heavy. Clothing should not be too tight in order not to hinder internal air circulation or restrict blood circulation. Best results are obtained if the clothing assembly is constructed according to the so-called several-layer-principle, e.g., in three layers:

  1. The inner layer next to the skin should regulate the micro climate around the body. With a thermal vest, appropriate regulation is automatically affected by the movements of the body. The vest produces a thermal insulating stratum of still air next to the skin. If the work is not too heavy, the body will require increased insulation at a minimum of ventilation and the reverse takes place when the body is subjected to heavy work. The greater the body motion the greater the ventilation should be. The vest also allows for evaporation of perspiration, which is essential, as the perspiration sooner or later will cool off the body, if allowed to be absorbed in the clothing.
  2. The middle layer should be insulated as well as permeable to water vapour produced by perspiration. Sweaters, pullovers, etc., are conventional garments. Warmer items can be made from synthetic materials, e.g., non-woollen, polyester or nylon fur padding.
  3. The outer layer should generally be wind and watertight, but should also be as permeable as possible to water vapour to avoid excessive perspiration. It should allow ventilation at certain areas. Clothing should be adjustable at the wrist and the neck.

The helmet should be lined. It should protect the neck, ears and forehead. Shoes and boots should be lined and fitted with non-skid soles. Gloves are not produced in any standard form and should be chosen to suit the actual work. They should be properly lined and not too tight. Overtight gloves can cause frost-bite. For psychological reasons the personnel should be allowed some degree of freedom in selecting their clothing.

11.2.2 Working in cold rooms

Cold rooms should provide as good a working environment as possible. Analysis of environmental stresses show that draughts have a great influence on comfort and must therefore be avoided. Lighting should be adequate to facilitate handling operations. Psychologically, a well lit room appears less cold than a dark room. Staff should be provided with heated rooms, where they can rest and dry their clothes if necessary. Resting periods require time and cost money hence they should be properly planned and supervised. A well spent rest, even if relatively short, restores the physical as well as the mental capacity of the worker and contributes greatly to improved physical performance. A normal work period in cold rooms is 50 min followed by a rest period of 10 min.

A warm rest room is essential. It should be strategically located to enable easy access during rest periods and at the same time provide proper supervision. There should be a free issue of hot beverage, coffee, tea, chocolate and also of cold non-alcoholic drinks. Smoking should be prohibited. Furniture should be comfortable, robust and easy to clean. Floor and walls should also be easy to clean. The room should be maintained at a temperature between 20C-27C and be well ventilated.

It is essential that people are instructed in the proper use of the heated rest room and in the maintenance and use of their protective clothing.

11.3 Safety

Safety is a very broad subject and it is impossible to cover all the hazards that different situations create. Large variations safety regulations are found from country to country and only general safety risks of are dealt with here.

11.3.1 Fire

Special attention must be paid to local fire regulations and the cold store should be planned to avoid obvious fire risks, e.g., air trunking, piping, fire walls, etc. With regard to fire-fighting equipment, it is advisable that full consultation be made with the local fire-fighting authorities who, in most cases welcome any approach. The fire brigade should also be invited to the cold store in order to familiarise themselves with layouts and equipment available. It is also recommended that training involving the local fire brigade, as well as the employees at the cold store, be carried out at regular intervals. For cold stores located remotely from local fire brigades, it is essential that an in-store fire brigade is organised and trained. In the training, it should be remembered that it is the action taken during the very first minutes which determines the size of a fire.

With regard to equipment, fire extinguishers are obviously essential, but care must be taken in choosing the right type. Various extinguishing agents are used and some can be dangerous both for humans and for equipment and property, if not properly used. This goes especially for fire-fighting in cold rooms, engine rooms and electrical installations. It is obvious that danger exists in the combination of water and electrical installations. Carbon dioxide, also poses danger as it displaces oxygen for breathing. This is especially important in small-size rooms. Normally the local fire-fighting authorities can give recommendations on equipment to be used and how the equipment should be marked for various purposes.

It is not advisable to position extinguishers in the cold rooms, because of low pressure in the equipment at the low temperature of the room. They should be placed outside and at strategic points like the loading ramp, entry point to roof cavities, and outside, as well as inside the engine rooms. All the extinguishers should be regularly maintained, preferably by the manufacturer or by other authorised personnel.

Breathing apparatus must be within easy reach and is normally placed close to the engine room entrance. There should be at least one set of pressurised air breathing apparatus at both the normal entrance and at the escape entrance to the engine room. It should be observed that no reliance can be made on the simple filter type gas mask in heavy concentrations of smoke, ammonia or other refrigerant, but this type can be useful in lower concentrations. It is of obvious importance that a sufficient number of the employees are trained in the correct use of breathing apparatus.

Space around the outside of the buildings is important in order to give the fire brigade quick access to any point, and provision of water hydrants are necessary, particularly if the buildings are placed at some distance from public roads. It is important to check that the couplings at the fire-points fit the fire brigade hoses and that the water pressure is adequate.

Welding operations have a high fire potential risk and therefore very strict precautions must be taken. The welder, who may not be a member of the employees of the cold store, should always be accompanied by a member of the staff. It is also advisable that the local fire brigade is informed when major work is to be carried out and in some countries welding is not allowed without a representative of the local fire brigade being present. It is important that there are always two men at the working place equipped with fire extinguishers. If working close to timber, insulation or other combustible material, the area of work should be covered, e.g., by asbestos blankets.

Where electric welding sets are used care must be taken to ensure proper earthing, but not to the structure of the building since this can lead to arcing and the initiation of a fire at a point far away from the actual welding operation.

11.3.2 Emergency escape

Adequate escape from cold stores is very important due to the low temperatures. Emergency doors should always be installed to give at least two alternative escape routes from any point in the cold room. Maximum distance to a door from any point is often set to 40 m. This is equally important for engine rooms. Gangways with dead ends should be avoided, as well as blocking of gangways with products. The emergency exits should preferably lead to the outside of the building where easy escape from the area is allowed. Escape onto roofs of a joining building should be avoided if possible.

Emergency exits present a security risk and therefore outside handles should be eliminated and the door secured on the inside. The latter must, however, be done with a simple, easy to remove device which must be regularly checked and maintained in order to avoid icing up.

11.3.3 Emergency lighting

Lighting must be provided at all times in low-temperature rooms. The minimum requirement is one lamp at each doorway, gangway and section.

11.3.4 Alarms

An acoustic alarm system must be provided for anyone who is accidentally locked up in a low-temperature room or for an injured person who cannot open the doors. The switches for the alarm should preferably be placed by every door and not more than 0.5 m from the floor. Other places for alarms are gangways around evaporators, roofs, engine room, etc. The sounder should be positioned where there is always someone in attendance, e.g., the loading bank or in the reception office.

Fire alarm systems are normally placed outside the cold rooms (to allow anyone to escape before raising the alarm). The alarm should sound both inside and outside the storage chambers. Automatic systems and smoke detectors are normally not a good alternative inside the low temperature rooms due to frosting up and reacting on to warm, moist air, etc.

11.3.5 Refrigeration plants

All personnel responsible for or working with refrigeration plants must have a clear understanding of:

The engine room should be equipped with a plate outside the room giving information of the supplier of the refrigeration plant, type of refrigerant and amount of refrigerant used in the system. In the engine room there must be a highly visible flow diagram of the refrigeration plant. There must be fire extinguishers and at least one respirator or breathing set, placed in a separate box outside the engine room. The mask should be complete with a suitable filter and there must be separate filters available together with two sets of protective gloves or rubber or similar suitable material. There must be a water tap and adjacent hose available which makes it possible to spray water at all points of the engine room. One of the most important safety equipments is a first-aid kit complete with eye-washing facilities.

11.3.6 Smoking regulations

Most food legislation prohibits smoking on and in premises used for food production, processing and handling. Therefore all personnel must be informed, when employed, about those regulations. Clear signs or markings should show where smoking is not allowed - any area where food is stored, processed, packed or handled. Special smoking zones should be located at convenient places and equipped appropriately with ashtrays and fire extinguishers. As a general rule smoking should be discouraged.

11.3.7 Safety instructions

Safety instructions must be issued to all employees and cover emergencies such as fire, refrigerant leaks, escape doors, assembling points, etc. The instructions should be written in simple language and kept brief and to the point. An example of a safety instruction is given in Appendix 4.

11.4 Security

The objective of the security at a cold store is to, as far as possible, eliminate theft, sabotage, etc. A cold store is a most attractive place for thieves, as well as terrorists. The following are general guidelines for preventive security.

The gatehouse is best located at the end of the access road, where incoming vehicles and goods can be directed to respective areas of the store. The gatehouse is a check-point for vehicles and employees. Ample space must be available for these purposes, e.g. a small lay-by for vehicles during checking and a waiting room for employees and visitors. For security reasons it is recommended that private cars be parked outside the store perimeter. A rail-siding, when this is of interest or necessary, must be long enough to suit a reasonable number of wagons. A combined rail and road traffic system at the same loading ramp or dock is not recommended.

Fencing and gates are important to prevent theft at a warehouse. Where it is not practical to put a lock or a guard at a gate, the manager should have a clear view of the traffic in and out of the site. The fence should be high enough so that it cannot be climbed easily and there should be a reasonable distance between the sides of the building and the fence.

Persons coming and going regularly within the site should have an identification badge that can be clearly seen, preferably with a photograph which is changed periodically.

Vehicles should also be identified with an appropriate sticker or temporary pass issued at the gate.

In small facilities supervisors should be asked to question people who are not readily identifiable. Parking lots should preferably be outside the fence, or if this is impractical the lot should be well away from the store.

Access in and out of the store itself should be limited, and the entries not in use should be locked. Modern inventory control methods emphasise the importance of one or two checkpoints for shipping and receiving, rather than a multitude of doors; the material handling disadvantages being more than offset by the product control advantages.

If parking is permitted within the premises a clear view of employees on their way to the parking lot is a must. Lights in the parking lots and other areas will pay off in theft prevention. The store itself should be well lit for safety and security. Employees should be trained to ask questions of people who they do not recognise as employees or authorised visitors.

Drivers of vehicles and their helpers have a great opportunity for theft. Unfortunately, experience has shown that outside drivers are a possible problem and should be treated as such. This problem has to be dealt with defensively by employing policies and procedures which prevent drivers or their helpers from loitering around the dock when not working. A good way to overcome this problem is to provide a waiting room for rest, food and relaxation. The vehicles should be checked on the way in, as well as out, (either on a continuous basis or by spot checks) and their authority to pick up a load should be verified. When practical, conduct random unloading and recounting. Such a procedure has a considerable psychological effect.

A large proportion of industrial crime is committed by employees and therefore a major part of the security efforts must be concentrated internally. Besides ordinary theft of products, special attention should be given to so-called "white collar" pilferage, such as paying a supplier twice, keeping the second cheque for personnel, and abuse or manipulation of time-cards.

Security starts at the top and it is important that the chief executive of the cold store complex is firmly against illegal or improper conduct. It is important that he takes immediate and correct action when something is wrong.

11.5 Instruments

The chamber temperatures are measured either by recorders which are placed outside the chamber or centrally covering more than one chamber, or by indicating instruments which are placed inside the chamber or centrally.

In order to obtain meaningful readings thermometers (probes) should riot be placed close to the door and it is recommended that the probe is buffered in order to avoid large fluctuations in the readings and the recordings. These fluctuations in air temperature, caused by door openings, etc., have normally no bearing on the product temperature. The buffering of the sensing probes is easily done by, e.g., placing the probe in a cylinder filled with a glycol solution with a lower freezing point than the actual room temperature.

The instrument used for checking product temperature should be a robust instrument as it is often handled in a rough manner. There are a large number of instruments to choose from, mainly battery powered. For measuring product temperatures liquid and glass thermometers are prohibited. Mercury thermometers may only be used for calibration of the instruments in daily use.

This thermometer should be a standard instrument with a certificated accuracy and the calibration should preferably be carried out at the actual operation temperatures.

11.6 Energy Management and Conservation

In view of the increasing demand for energy and the escalating costs of energy from all sources, energy management and energy conservation are becoming increasingly important in all industries and obviously also in the food systems.

Even if a number of investigations have shown that freezing and frozen storage, as well as chilled storage, are less energy demanding than some other preservation methods used for foods, good energy management and energy conservation are important factors in the operation of cold stores.

Energy consumption obviously has to be regarded already at the planning and design stages of a cold store. Large savings can be made by careful selection and assembly of components. Choosing efficient evaporator fans with the correct mass air flow and air throw for the store dimensions and optimising the insulation thickness taking relevant location conditions into account can show considerable savings.

Heat pumps can be used to utilise condenser heat for heating purposes, e.g., hot water for cleaning or heating. All buildings should be of a light colour. The loading dock should preferably be enclosed. This is just to mention a few measures to be taken. Today, most of the relevant actions are taken in the cold store design as long as experienced consultants are used.

The measures to be taken from an operational point of view range from proper control of lighting and air conditioning, to the proper running and maintenance of the engine room.

However the storage temperature should be kept lower than -18C and preferably -24C to -30C, especially for fish products. Even if the energy bill could be reduced by increased storage temperature, this saving is minimal compared to the total saving possible by an adequate energy management.