بدضعیفمتوسطخوبعالی (بدون رتبه)


A measurement of pressure, 100kPa = 1 bar. This corresponds very closely to 1 atmosphere and the two are often confused. 1 bar = 14.504 psi. 1 atmosphere = 14.7 psi.

Bar(a) also bara:
The pressure of a system or device measured from absolute zero.

Bar(g) also barg:
The pressure of a system as viewed on a pressure gauge, which does not include atmospheric pressure.

A compressor that is designed to operate at lower pressures. Usually a blower is an air compressor that operates below 2 barg, although this figure is quite loose and depends upon the respective manufacturer.

Brake horsepower:
In our metric terms this is obsolete. However, it refers to the amount of power that is available from the drive shaft of the electric motor connected to the compressor.

The relatively new UK (1999) regulations require that the bund must be capable of containing 110% of the liquid contained in a single tank. Multiple tanks must be bunded so that 110% of a single tank plus 25% of each of the remaining tanks can be contained. If these regulations are applied to a packaged screw compressor, then the enclosure should be designed so that it will contain 110% of the oil capacity without releasing discharge to the ground.


An Americanism which refers to the amount of compressed air delivered by a compressor or required by a system. The term capacity is usually qualified by something else, such as SCFM, ICFM etc.

CDM Regs:
See Construction (Design & Management) (Amendment) Regulations 2000, and also see Planning Supervisor.

CFM: (Cubic feet per minute)
The imperial method of describing the volume flow rate of compressed air. It has to be defined further to take account of pressure, temperature and relative humidity. For example:

* CFM (FAD). Cubic feet per minute, free air delivered. This is the amount of compressed air measured in cubic feet per minute, converted back to the actual inlet (free air) conditions before it was compressed.

* ACFM. Actual cubic feet per minute. This is the flow rate measured under stated operating conditions. This would be the actual volume flow rate that you could observe if the pipework after the compressor was transparent and you measure the actual flow rate under pressure. However, some American compressor manufacturers use the same term to describe the amount of air entering the compressor under Normal conditions. Always check what the supplier means.

* ICFM. Inlet cubic feet per minute, this appears to be the same as CFM (FAD) but it may hold a trick up its sleeve depending upon the type of compressor that’s being offered. If the compressor uses labyrinth seals, the ICFM figure is probably 1% or 2% higher than the true air volume coming out of the other end. This is because the labyrinth seals inside the compressor will be wasting about 1% or 2% of the volume flow.

* SCFM. Standard cubic feet per minute. This is the actual flow rate, converted back to standard inlet conditions. Also see Standard Reference Atmosphere.

This term is used for turbo compressors and represents the maximum flow condition. It is sometimes also referred to as stonewalling.

Climate Change Levy:
Announced in March 1999, this is to be introduced in April 2001. The target is to save 1.5 million tonnes (UK only) of carbon (emission) per annum. Essentially the ‘Carbon Tax’ will be structured to bring in £1.75b to the exchequer and will be returned to employers via a proposed 0.5% reduction in employers NI contributions, (now reduced to 0.3%).

Competent Person:
The Pressure Systems Safety Regulations 2000 requires that a compressed air system is inspected by a person, and once it has been inspected the same named person signs a document declaring that the system is safe. The signatory is required by law to be ‘Competent’, in practice this means a person with a Higher Qualification in Mechanical Engineering together with a minimum of 5 years experience in the relevant field of engineering. Ask to see the ‘Blue Card’ which would have been issued to a prospective ‘competent person’ by the Engineering Council. The competent person is responsible in law if the system is subsequently found not to be safe. See Safety of Pressure Systems Regulations.

A machine which usually sucks in air and compresses same so that it ultimately occupies a smaller volume. The resulting air will not only occupy a smaller volume, it will have a higher pressure and a higher temperature. See blower.

The liquid that forms when compressed air is cooled, or when air is compressed at constant temperature. The condensate produced by compressed air is water, although it may be contaminated with oil, dirt or other materials. See mayonnaise.

Condensate Management:
A relatively new term that has come into force because of the Water Resources Act 1991. The condensate from a compressor, dryer or filter has to be treated before it can be discharged down a foul drain (sewer). The level of permissible contamination varies from one regional Water Authority to another. It is absolutely prohibited to discharge condensate, treated or otherwise, down a rain water drain.

Construction (Design and Management) (Amendment) Regulations 2000:
The original 1994 Regulations have been amended in light of a decision by the Court of Appeal, which was contrary to the HSE’s original intention of the law. This now means that designers who arrange for employees or other persons to prepare a design, still have a duty under the revised CDM Regulations. These Regulations also place duties upon clients to ensure that construction & demolition is carried out under prescribed conditions by competent persons. These regulations specifically apply to compressed air systems and not only include design and installation, but are also applied to service work and maintenance. The Regs require…

* Appointment of a Planning Supervisor
* Allocation of adequate resources.
* Production of a Health & Safety Plan.
* Appointment of a Principle Contractor.
* Development of an ongoing H&S File (based upon the initial H&S Plan).

CIMAH Control of Industrial Major Accident Hazards Regulations.
European Community (EC) Directive adopted in the UK in 1984 and called the CIMAH Regs. Operators of certain hazardous industrial installations must prepare a written safety case, similar to a Risk Assessment. Such installations may include the use of compressed air plant and equipment in ‘zoned’ areas. The operator must…

1. Identify nature and scale of hazard.
2. Outline arrangements for safe operation.
3. Identify and evaluate type and consequences of a major accident.
4. Demonstrate appropriate controls are in place.

Note: The safety case did not focus on management systems, after Piper Alpha disaster, the regs changed to COMAH 1994.

COMAH Control of Major Accident Hazards Regulations 1994.
Administered by the Competent Authority. (The H&S plus the EPA). Based upon CIMAH but to include…….

1. Identify major hazards. Ensure that risk to personnel has been analysed and appropriate controls provided.
2. Adequate provision for evacuation, rescue etc in the event of a major emergency.
3. The Safety Management System (SMS) is adequate and the design operation of the installation is safe.

COSHH Control of Substances Hazardous to Health.
This requires a Risk Assessment. However, it only applies to chemicals, for example molten lead would not require a COSHH assessment. The five outcomes suggested by H&SE are…

1. No risks now, unlikely to change in the future.
2. Risks are high, there is inadequate control.
3. The risks are controlled, but may increase in the future.
4. There is a hazard, the risks are uncertain.
5. There is insufficient data to ascertain the risks.

The response to any risk assessment must be one of…

1. No action if substances/activities do not change.
2. Immediate action.
3. No action now, but future changes should minimise risk.
4. More info needed.

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