An air compressor is a valuable piece of equipment for operating power tools. They are better in terms of efficiency and are easier on you. The type you need depends on the tools you will be using. Good choices include a Copeland compressor, Husky air compressors or Quincy compressors.
Factors to Consider in an Air Compressor
Consider how often you will use air compressors and how it will be used. What tools will you be using and how much power will be needed to operate them? Some tools, like nail guns, don’t need high volume compressor. Others, such as drills or sanders do need high volume because they require steady air flow.
Set a budget for your purchase. The price for these machines varies significantly from brand to brand. Buying a used compressor is one way to make your budget stretch further.
The style of the pump is another consideration. The most common are direct drive and belt drive. Direct drive pumps will last up to five hundred hours. These take up less room in your workshop. They are well suited for moderate uses. Another benefit of these is that no oil changes are needed. Belt drive pumps require oil changes every five hundred hours and will last for about fifteen hundred hours. These are good for do it yourself as well as professional use.
Consider the power of the compressor. Consider both the horsepower and pound per square inch (PSI) pressure. Make sure it is more powerful than the most powerful tool you will be using. Check your tools before purchasing the compressor.
The tank size is another important consideration. These come in sizes from two to one hundred gallons. The more you will use the equipment, the larger the tank you will need. Always go a little larger than you think you will need. This will ensure that you can get the optimum use from the compressor.
Finding an Affordable Air Compressor
Shop around before purchasing air compressor systems. Compare brands and read reviews on the internet. Compare the machines and features of each. Similar machines can differ by hundreds of dollars.
Consider a reconditioned machine. In these, the machines have been completely inspected. Worn or damaged air compressor parts are replaced. Many of these have gotten very little use and are in nearly new condition. You can find equipment at a considerable savings. Look for a model with a one year warranty to be sure you are getting a quality product.
Consider shopping online. Often, the prices are considerably less than in some stores. Many ship straight from the factory, saving retail mark up. This savings can be significant. In many cases, you won’t need to pay sales tax on the equipment, which can add up. Many sites offer free shipping on these purchases, so it won’t cost any additional money for shipping.
OTHER RISKS
28 Refrigeration systems often have associated risks which may require attention, These include the risk of trapping in cold stores and chills, the handling of very cold products and microbiological problems associated with cooling towers used for the condenser.
ENFORCEMENT APPROACH
29 Enforcement officers should advise that ammonia refrigeration plant should comply with the guidance in BS 4434: 1980 as amended and augmented by the information in this circular. They should however bear in mind:
(1) ammonia presents a toxic risk at concentrations far below those at which it presents any fire or explosion risk. There have been 2 gassing fatalities between 1977 and 1983 in the UK but only 3 incentive ammonia/air explosions in the last 20 years;
(2) the potential consequences of an incident in terms of injury to personnel, and the general public should be assessed;
(3) BS4434 was first published in 1969 and was not intended to be retrospective, although improvements in installations which pre-date the standard should be recommended, where reasonably practicable;
(4) analysis of the l983 visits strongly suggest that where poor conditions of the plant are found there is often inadequate attention to evacuation and emergency action; and
(5) where enforcement officers encounter maintenance contractors they should make enquiries about their working practices and training. Further advice
30 This is a complicated technical subject and there are strong trade pressure groups. Enforcement officers are recommended to seek the advice of HSEs Field Consultant Group (FCG) via the Local Enforcement Liaison Officer (ELO), before considering enforcement action.
Ammonia is used as a refrigerant because of particular thermodynamic properties which enable it to move heat far more efficiently than other refrigerant gases such as halogenated hydrocarbons. It is particularly suited to working in the range approximately OoC to -30oC and hence is widely used for food preservation, the chilling of liquids such as milk, beer and soft drinks, and in the chemical industry. New systems continue to be installed.
2. A simple system theoretically needs 4 components:
(1) evaporator;
(2) compressor;
(3) condenser; and
(4) reducing valve
In practice other components such as oil separator, intercooler, liquid receiver, surge drum and liquid pumps are often found.
3 The useful refrigeration is produced at the evaporator. Liquid ammonia at low pressure, and hence low temperature, takes in heat by vaporising. This vapour is removed by the compressor which, in compressing it, raises the temperature from below to above ambient. The hot compressed gas gives up the heat by condensing to a liquid in the condenser. The high pressure liquid then passes through the pressure reducing valve to the evaporator. At the valve the liquid is cooled as some vapour flashes off. The remaining liquid is available for use in the evaporator.
4 In a practical system it is likely there will be other items of plant. An oil separator removes suspended oil carried over from the compressor and either returns it to the (pressurised) crank-case or holds it for draining in some way. There may be a multi-stage compressor with an intercooler. This is cooled by bleeding high pressure liquid into the low pressure side.
Downstream of the condenser is generally a liquid receiver. Downstream of the reducing valve is often found a surge drum which acts as a reservoir of cold liquid and evens out demand on the compressor and condenser. The liquid ammonia is drawn from the surge drum by a pump. Oil drains may be found on surge drums, liquid receivers, and elsewhere on large plants. There is also likely to be an automatic control system on all but the oldest and smallest plants.
A simple practical refrigeration system
1 The aim was to collect information about a cross section of installations. One hundred and forty eight returns were used in the analysis which used the Edinburgh FCG microcomputer.
2 Returns covered a wide range of processes in the food and drinks industries. The largest single sector was dairying (chilled water supply) with substantial returns also from frozen food producers and cold stores. In the drinks sector cooling and soft drinks carbonators were the principal uses.
There were a wide range of other uses reported; most parts of the food industry require controlled temperatures below ambient at some part of their process. A wide range of sizes of installations from 45 kg to 45 tonne chargeweight were reported, 13% were over 5 tonnes, 40% between 1 and 5 tonnes, 35% between 100kg and 1 tonne and 12% 1 00 kg or below. The oldest component reported was pre-war and there was a fairly even spread of age from 1960 to the present.
3 Eighty-nine per cent of installations had a separate compressor room. Forty-nine percent had the system charging point in the compressor room and 38% had it outdoors. Twenty-seven per cent of the sample could positively be identified as having doors to the outside of the building only. Thirty-six per cent of the other compressor rooms did not have self-closing doors and 17% did not have well-fitting doors. With compressors in a separate room this is a surprisingly large number where even the most rudimentary precautions to prevent the spread of escaping gas has not been taken. Fifty-five per cent had condensers mounted above ground level outside - typically on the roof.
This raises questions of safe access and also escape in the event of an emergency.
4 Thirty-six percent, had the evaporator in the workroom. (These were usually product freezers in the frozen food sector and carbonators at the soft drinks plants). This points to the need for effective emergency procedures in the event of leakage, particularly if it is in the workroom.
5 Only 3% of installations were identified as having pipework or plant capable of being damaged by, for example, fork lift trucks. Half of the entire survey however had unmarked pipework. (Notes of many proformas suggested that this would receive early attention).
6 lt proved impossible to carryout meaningful analysis of the ventilation provided in compressor rooms. A common installation seemed to rely largely on natural ventilation (perhaps assisted by a small fan) for normal ventilation. Where there was provision of ventilation specifically for emergencies, it tended to be a separate system rather than a 2 speed fan on the normal ventilating system. Only 23% of the installations had 2 ventilation rates available and only half the ventilation systems of any kind could be controlled from outside the compressor room. Only half of these ventilation systems were automatically controlled.
7 Only 16% of all system charging was done by a person on his own; the usual arrangement was 2 men. Oil draining was done by one man on his own at 30% of all Installations. At 51 % of all installations it was carried out more than once a month. Only 26% of installations had spring-loaded valves or a catchpot system at oil drains. Most of the rest had simply a short stub of pipe from a vessel containing liquid ammonia closed by a single valve. In 71 % of cases where the oil drain was unsatisfactory inspectors considered that the reasonably practicable improvement was the fitting of self-closing valves. The 30% of installations where one man did the oil draining on his own included 6 which had no respirator of any kind.
8 Forty-two per cent of compressor houses had no gas detectors. Sieger was by far the most common supplier (60%) of all detection systems. The most common service period of twice per year reflects that companys normal service contract. Nineteen per cent of detector systems were never checked.
Approximately half of the detector installations only had one operating level. Twenty-seven per cent of systems did not shut down the plant but merely raised the alarm. Ten per cent of the systems had no separate alarm.
9 Sixty-six percent of compressor room electrical installations were not fully equipped to Zone 2 standard even where much of the plant was under the control of detectors. Seventy-five per cent of all compressor installations could be switched off elsewhere outside the compressor room (even if only at the main supply). Of the remainder, the main switchgear was either in the compressor room or access to it was through the compressor room.
10 Eighty-eight percent of all sites had 2 or more sets of respiratory protection of some kind. Six installations (4%) had none at all. At 83% of sites there was said to be some sort of training in the use of respiratory protection but only 43% had some sort of systematic examination. At only 5 installations (3.4%) were there possible limitations of space which conflicted with provision of respiratory protection and the main problem seemed to be access up ladders or around congested items of plant.
11 Forty-seven per cent of sites had reviving apparatus available usually for general first aid rather than specifically because of the ammonia.
12 Twenty-seven percent of sites had Draeger (or similar) detector tubes for measuring low concentrations of ammonia. Many others had sulphur sticks or hydrochloric acid for detecting small leaks.
13 Fifty-nine percent of installations were maintained at least partly by contractors. Apart from a few major suppliers and installers of equipment there were many local refrigeration engineers who only appeared once or twice in the survey. No information is available about the standard of training or workmanship of these contractors.
14 Fifty-five percent of all sites appeared to have emergency evacuation procedures (43% used the fire alarm) but slightly fewer (50%) appeared to give any training in these procedures. Only 24% appeared to have detailed rescue arrangements. Twenty-two per cent had written systems of work which appeared comprehensive and only 34% had what appeared to be effective plant operator training.