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Dairy Equipment Maintenance
|Milk Processing Guide Series|
Training Programme for Small Scale Dairy Sector and Dairy Training Institute - Naivasha
|TABLE OF CONTENTS
Dairy Equipment Maintainance*
2. DAIRY EQUIPMENT MAINTENANCE*
2.1 WHAT IS MAINTENANCE?*
2.2 TYPES OF EQUIPMENT MAINTENANCE SYSTEMS*
2.2.1 Preventive maintenance*
2.2.2 Elements of preventive maintenance programme*
2.2.3 Scheduled repairs*
2.2.4 Economical Maintenance*
2.3 IMPORTANCE OF FOLLOWING MANUFACTURER'S INSTRUCTION*
2.4 COMMON MAINTENANCE PROBLEMS*
2.5 COMMON MAINTENANCE PROCEDURES*
2.5.2 Lubrication of Equipment.*
2.6 CORROSION OF DAIRY EQUIPMENT.*
2.8 CARE OF TINNED SURFACES*
2.9 MAINTENANCE OF BASIC EQUIPMENT*
2.9.1 Milk cans*
2.9.2 Milk cooling equipment.*
2.9.3 Milk separator maintenance*
2.9.4 Butter churn maintenance*
2.9.5 Milk pumps*
2.9.6 Plate Heat Exchanger*
2.9.7 Hot Water/Steam boilers*
2.9.8 Air Compressors*
2.10 Cleaning and Sanitation.*
2.11 Setting up of Machinery*
Since the liberalisation of the dairy industry in Kenya in 1992, many small scale to medium scale dairy processing plants have been established in most of the major milk producing areas. The sizes vary from as small as 200 litres per day to as high as 15,000 litres per day. The level of mechanization and automation also vary according to the size of the plants and the capital investments that have been put unto the establishments.
On account of its constant everyday use and service, the presence of water, steam, ammonia, brine and a variety of cleaning agents, the Dairy and Food plant equipment are more expensive to maintain than equipment in many other industries. In addition, the equipment is usually made demountable for sanitary reasons. This also increases the wear and tear. So whatever the size of the plant and type of equipment used, from simple milk cans to expensive machines like homogenisers, the dairy plant owner should be concerned with the length of service each particular equipment is going to give. This is important because it has a direct influence do the economic returns to investment and profits. This is more apparent with highly specialised and complicated equipment which are very costly. This together with the ever increasing labour costs requires that each piece of equipment be used continuously at peak efficiency and have a prolonged useful life.
Although the length of service one can expect from any given machinery or equipment will depend on the durability associated with its design and workmanship, the way it is used and handled will influence greatly whether or not its utility will extend as long as it was designed to last. The expected useful life of most dairy equipment is about 8 years, implying a depreciation of 12.5% per annum. With good care and optimum maintenance, the useful life of such equipment can easily be extended by 30-35% or more.
This brief guide has been put together by DTI/FAO training team under Project TCP/KEN/6611 to complement the short course instructions on Dairy Equipment Maintenance Module which has been designed for the Training Programme for Small Scale Dairy Sector in Kenya. It is not meant to be a substitute far detailed manufacturers maintenance manuals usually provided with each dairy equipment. Rather, the main intention is to draw the attention of dairy processing plant and equipment operators to the importance of proper procedures of dairy equipment maintenance and how the neglect of this important aspect can affect dairy product quality and profitability of the dairy processing plant. For more detailed treatise of Dairy Equipment Maintenance, the reader is referred to the bibliography at the end of this guide.
Mintenance is the upkeep of plant and machinery in proper working condition at all times
This is the persistent and systematic procedure for the care of all production, control and auxiliary machinery in a dairy factory including regular servicing, upkeep and overhaul, record keeping and stocking of essential spare parts for the purpose of preventing breakdowns and emergency shut downs for repair.
Preventive maintenance must begin with the purchase of the right type of equipment for any specific job. The machine must always do the job of its right capacity for high durability. If a machine that is of low capacity is consistently being called upon to do a job meant for a high capacity one, no amount of preventive maintenance will cure it!
Preventive maintenance is useful and necessary because it will prevent loss of money and profits due to:
The main objective of preventive maintenance is to:
A good preventive maintenance programme must include the following elements:
- Routine external inspection of all equipment
- Periodic internal inspection
- Systematic lubrication
- Prompt adjustment, repair or replacement of defective part(s)
- Record keeping system
- Periodic analysis of system(s) operating parameters
- Spare parts inventory and inventory control
- Scheduled major overhaul of machinery
- Economic basis for scrapping off of equipment
- Maintenance cast analysis and reporting to management
- Capable maintenance supervision
All the above elements are essential for an effective PM programme. None should be overlooked or ignored.
From the above, a more comprehensive definition of PM should be:
"Preventive Maintenance is a procedure utilising programmed and coordinated lubrication, internal and external inspections, timely adjustments, repairs and replacements performed by skilled and trained personnel under qualified supervision., fair the purpose of preventing unscheduled down time, preserving equipment, maximizing overall plant performance, minimizing maintenance costs, and thereby contributing to an improved profit position" (Newcomer, 1981).
Replacement of parts at preset time or service intervals may be prescribed for certain parts. They must be replaced when due for replacement. It may apply for gaskets, O-rings; oil and air filters.
The secret of economical upkeep is to train operators to handle the equipment as if it were their own, and to keep a continuous inspection for the small things that go wrong. This should be supplemented by a periodic general inspection. In small plants, it is advisable for each operator to take care of the equipment he/she runs, when minor repairs are needed since there is seldom an engineer around. In large plants, a trained engineer should usually be available for all required repairs.
The things which go wrong with equipment can often be easily solved by reference to the manufacturer's instruction manual. It is very unfortunate if equipment is unsatisfactory when a simple adjustment as explained in the instructions manual would solve the problem. Most manufacturers of dairy equipment furnish complete instructions that show exactly how the equipment is to be operated, especially on major items of the equipment e.g. pasteurizer, refrigeration machine, Ice Cream Freezer, homogenizer etc.
Most breakages of machinery and loss of efficiency, together with unsatisfactory operation can be traced from failure to follow the manufacturer's instructions. It is impossible for busy superintendent to carry around all detailed instructions for all his machineries. It is therefore important at all times that the instructions be available to the man who operates the machine. The superintendent/supervisor should occasionally check them over with the operator to make certain that the operator has absorbed the information in the instruction book.
Operators should be responsible for their machines.
The commonest maintenance problems include:
- Lack of proper lubrication
- Breakage due to operators not handling the machine properly and according to instructions or using wrong tools to open or service a machine
- Leaks due to rough handling of equipment or improper assembling or mounting
- Corrosion due to improper washing and cleaning methods (use of wrong detergents or too high concentrations and/or temperatures).
Care directed to the above items will pay dividends in the long run.
Lack of lubrication is one of the principal causes of equipment breakdown. The best solution is to have a regular lubrication schedule, and perhaps a lubrication chart for each machine, setting the frequency of lubrication, type of lubrication needed, and places to be lubricated.
Modern equipment calls for certain types of lubricants for certain types of bearings e.g. light, high speed bearing will require a light oil, whereas a heavy duty, low speed bearing will require heavier oil.
Bearings that are operated at high temperatures must have a lubricant specially adapted for this use, just as those bearings that operate at extremely low temperatures will require zero oil.
Many dairy plants have rather high humidity and for that reason the moisture problem should be considered. Certain lubricants are available that resist rusting and corrosion due to moisture. There are also oils that resist emulsification with water and are advantageous for flooded systems of lubrication where gears and chains run in oil.
The most tightly enclosed oiling system will with time allow moisture to accumulate. It is essential to occasionally check the oil in an enclosed drive to make certain it is not contaminated with water. Usually the water will collect at the bottom and may be drawn off easily.
220.127.116.11. Handling of Lubricants
In many cases, bearing failures may be traced directly to improper lubrication responsibility and to the handling of lubricants. Some of the factors concerned are:
18.104.22.168 Indications of Faulty Operations of Anti-friction Bearings
Faulty anti-friction bearing operation can sometimes be distinguished by abnormal noises. Accurate diagnosis, however, is possible only if the bearing is dismantled and inspected. Some of the defects that cause noisy bearing operations are:
22.214.171.124 Over or under-lubrication.
Over lubrication causes overheating and waste of lubricant.
Under lubrication results in excessive wear, overheating due to friction and as a result reduced bearing life.
If a high speed, antifriction bearing equipped with a grease fitting is pumped full of grease, the grease increases in volume, and excessive pressures and temperatures result because of the churning of the lubricant and the resulting rise in temperature.
It is recommended that a bearing be padded or filled not more than 1/3 or 1/2 full. This will allow the grease, under operating conditions, to expand without building up excessive internal pressure.
126.96.36.199 Contamination and Corrosion
The presence of abrasive contaminants such as dirt, dust, metal particles, hardened grease deposits and other foreign materials is probably the principal source of antifriction bearing damage and failure. The other important cause for bearing trouble is corrosion resulting from moisture introduced by handling or by exposure to excessively wet conditions and inadequate sealing.
Grease containers should be kept covered, grease dispensing equipment should be cleaned, grease fittings should be wiped clean before refilling.
The direction on how to lubricate equipment given by the manufactures should always be followed. Below is given some general facts of how to lubricate and what type of lubricants to use when lubricating the most common types of dairy equipment.
The key to caring for tools is to have a rack for each tool stacked and painted in distinct colour. If a tool is to be frequently used on a special machine, the tool rack should be near that machine.
The general purpose tools should be kept in a locked cabinet with the outline painted on the back of the wall cabinet for each tool. Small tools can be kept in a portable metal box.
To get best service from a tinned surface, two principal considerations are important:
- RETINNING OF SURFACES.
Tinned surfaces require occasionally retinning. This should be done by RETINNING experts with necessary equipment.
Great care should be observed in the handling of milk cans i.e. that they are not dented or damaged more than necessary. During cleaning of cans, the cleaning solution should be kept at the proper strength as alkali or acid cleaner of high concentration remove the tin and allow rusting. Thorough drying of cans will increase their life span and also improve on milk quality handled.
Various types of refrigeration equipment ranging from surface coolers, immersion coolers, ice-bank and direct expansion refrigeration systems are in use throughout the dairy industry. Whereas it is beyond the scope of this guide to go into detailed description of maintenance systems of each type of cooling system, it suffices to mention here that manufacturer instructions on service ice and scheduled repairs should be followed very strictly. Special attention should be paid to lubrication of compressors and detection and timely repair of refrigerant gas leakages.
Where brine is used as a coolant, its corrosiveness to dairy equipment should also receive particular precautions during its circulation and handling. In view of the importance of milk cooling vats in dairy industry from the producer cooperatives to the processing factories here we produced a summary of fault finding procure for direct expansion refrigeration vat:
Generally follow manufacturer's instructions and lubrication procedures outlined above (see section 2.2-2.5.2).
Table 2 below gives common pump problems and possible causes.
Table 2. Common pare problems and possible causes
Source. Alfa Laval Pump Guide.
Generally follow manufacturers instructions and preventive maintenance
programme (see section 2.2).
Pay particular attention to possibilities of under-pasteurisation, recontamination of pasteurised milk due to air leakages into the system, and milk leakages. Have in place manual product temperature indicating thermometers in addition to automatic monitors. Pay particular attention to the well functioning of the flow diversion valve.
There are basically two types of boilers; the Fire tube boilers and the water tube type. Which ever type of boiler is used, the proper functioning of the following controls and accessories are essential for efficiency and safety.
These have to be regularly checked and maintained for proper economical running of the equipment.
Smaller dairies now utilise hot water generators using electric coils. Whey dealing with steam boilers or hot water generators, generally follow manufacturers' instructions and preventive maintenance programme for dairy equipment (see section 2.2).
Air compressors are needed in the dairy plant for operation of pneumatic valves and presses. They consist of a compressor pump, motor, air receiver and electrical controls.
Generally follow manufacturers instructions and preventive maintenance programme (see section 2.2). Pay particular attention to the well functioning of the compressor and motor which are the heart of the machine.
Maintenance of dairy equipment cannot be complete without due attention to its cleaning and sanitation. This is necessary not only from the hygienic point of view but also in the prevention of mechanical damage (e.g. corrosion) to plant and equipment. Selection of the right type of detergent and its proper use (temperature and concentration) is important. Generally, the cleaning procedure should consider two types of equipment, those which can be cleaned in place and those that require manual clearing.
Even for those which use CIP methods, occasionally opening up connecting ends and seals for mechanical brushing cannot be avoided. For more guidelines on proper cleaning of dairy equipment, see Processing Guide No. 1 in his series.
In setting machinery, the equipment should be located, if possible in a lighted dry place with plenty of room to work around it for cleaning and repairs. The arrangement should be that the minimum amount of sanitary piping is used, consistent with efficient operation. Related equipment may be grouped together to facilitate supervision. Straight-line flow of product is usually desirable. If possible allow space for unit machine to be added later when the business grows.
Machines especially the heavy ones, are set directly on the floor or on concrete base and grated in thoroughly with a rich cement mixture (1 part cement and 2 1/2 parts sand) and sufficient water.
For improved sanitation, use is made of the ball foot mounting with equipment such as tanks, freezers, fillers etc, on a pipe legs 6-12 inches long having a round foot. Where machinery is bolted down, it is customary to see bolts in the concrete
1. Newcomer,J.L. 1981. Preventive maintenance manual for Dairy Industry Venus Trading Co. Anand, India.
2. IDF. 1990 Handbook of Milk Collection in Warm Developing Countries. IDF Special Issue 9002.
3.0'Mahony, F Rural Dairy Technology: Experiences in Ethiopia. ILCA Manual No 4 Publ. ILCA, Addis Ababa, Ethiopia.
4. Cowan, C.T. 1983. Avoiding Corrosion and damage to Homogenisers. In: Selected case of Corrosion in the Dairy Industry. Brochures 7-11. IDF Doc. 161
5. Ibid. Corrosion prevention in UHT Indirectly Heat Milk Sterilisers. In: Selected cases of Corrosion in the dairy industry. Brochures 7-11. IDF. Doc 161.