We undertake work for most of the UK's major Gas users and specialise in all aspects of gas handling

Frequently Asked Questions

Central Compressors FAQ

Where are you based?

We are based on the Daniels Industrial Estate, just off the A46 south of Stroud, within 4 miles of the M5. For maps and more information on how to reach us visit our “contact us” page.

What companies do you do business with?

We supply compressors to organisations with many different needs such as county fire brigades, universities, hospitals, gas companies, the Ministry of Defence, water companies - anywhere a supply of compressed air or gas is needed.

Where can you supply and maintain compressors?

We can supply compressors to any location in the UK and worldwide.

Do you do overseas projects?

Yes we do, our engineers have travelled to Dubai, India, the Falkland Island and many other countries to supply and maintain compressors.

Do your compressors come with any guarantees?

Yes, all at a minimum of one year and some have a five year guarantee depending on the application and the needs of the company.

When buying a compressor does it need to be continually serviced?

When buying any mechanical piece of equipment it is good practice to have it serviced and maintained, this not only increases the life of the equipment but reduces the chance of a major expensive failure.

Whose compressors do you supply and maintain?

We have completed works with many leading compressor manufacturers including:

  • Gardner Denver, (Hamworthy, Belliss & Morcom, Bristol Pneumatic, Williams & James)
  • Compair Reavell
  • Hydrovane
  • Boge
  • Donaldson
  • Beko
  • JP Sauer & Sons, Germany
  • Lenhardt & Wagner, Germany
  • Bauer Compressors
  • Peter Brotherhood
  • Atlas Copco
  • Mehrer, Germany

Do you offer loan compressors while repairing a company’s compressor?

We offer loan compressors for any need and for any amount of time your compressor is offline.

What is the breathing air standard?

The breathing standard we use is the European standard EN 12021 for quality of air you breathe. The standard uses the following limits:

  • Carbon monoxide (CO) max. 15 ml/m3
  • Carbon dioxide (CO2) max. 500ml/m3
  • Water vapour and condensate max. 25 mg/m3
  • Air must be without odour or taste.
  • Maximum pressure, depending on the cylinder type is 200/300 bar at 15 °C.
  • Safety valves must be adjusted to 225/330 bar respectively to account for increased pressures at higher temperatures.

Technical terms

Absolute Pressure

Total pressure measured from zero.

Absolute Temperature

See Temperature, Absolute.

Actual Capacity

Quantity of gas actually compressed and delivered to the discharge system at rated speed and under rated conditions. Also called Free Air Delivered (FAD).

Atmospheric Pressure

The measured ambient pressure for a specific location and altitude.

Cubic Feet Per Minute (cfm)

Volumetric air flow rate.

Cfm, Free Air

Cfm of air delivered to a certain point at a certain condition, converted back to ambient conditions.

Actual Cfm (acfm)

Flow rate of air at a certain point at a certain condition at that point.

Inlet Cfm

Cfm flowing through the compressor inlet filter or inlet valve under rated conditions.

Standard Cfm

Flow of free air measured and converted to a standard set of reference conditions (14.5 psia, 68oF, and 0% relative humidity).

Dew Point

The temperature at which moisture in the air will begin to condense if the air is cooled at constant pressure. At this point the relative humidity is 100%.

Free Air

Air at atmospheric conditions at any specified location, unaffected by the compressor.

Gauge Pressure

The pressure determined by most instruments and gauges, usually expressed in psig. Barometric pressure must be considered to obtain true or absolute pressure.

Humidity, Relative

The relative humidity of a gas (or air) vapour mixture is the ratio of the partial pressure of the vapour to the vapour saturation pressure at the dry bulb temperature of the mixture.

Piston Displacement

The volume swept by the piston; for multistage compressors, the piston displacement of the first stage is the overall piston displacement of the entire unit.


Force per unit area, measured in pounds per square inch (psi).

Pressure Dew Point

For a given pressure, the temperature at which water will begin to condense out of air.

Pressure Drop

Loss of pressure in a compressed air system or component due to friction or restriction.

Pressure Range

Difference between minimum and maximum pressures for an air compressor. Also called cut in-cut out or load-no load pressure range.

Rated Capacity

Volume rate of air flow at rated pressure at a specific point.

Rated Pressure

The operating pressure at which compressor performance is measured.

Required Capacity

Cubic feet per minute (cfm) of air required at the inlet to the distribution system.


A vessel or tank used for storage of gas under pressure. In a large compressed air system there may be primary and secondary receivers.

Standard Air

The Compressed Air & Gas Institute and PNEUROP have adopted the definition used in ISO standards. This is air at 14.5 psia (1 bar); 68F (20C) and dry (0% relative humidity).

Temperature, Absolute

The temperature of air or gas measured from absolute zero. It is the Fahrenheit temperature plus 459.6 and is known as the Rankine temperature. In the metric system, the absolute temperature is the Centigrade temperature plus 273 and is known as the Kelvin temperature.


  • High Pressure Air and Gas Compressors to a maximum of 6000psi
  • Installation and commissioning, high and low Pressure Systems
  • Oil free air for instrumentation
  • Medical Air, Pure Air System
  • Breathing Air to British Standards
  • Compressor valve replacement schemes
  • Re-conditioned Compressors with warranty
  • Compressors available for hire
  • Gardner Denver, Hamworthy Belliss and Morcom approved service agents
  • Air Purity Analysis

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