Glossary of Terms
The air cooled compressors are the most common type of compressors and rely on a flow of fresh air that is pushed by the built in fan across the compressor block and over the inter stage cooling pipes. The compressor needs a very large amount of air to cool it and the rule of thumb for this requirement is 300 m³ /hour flow for each kW of motor power. example:
- 450E, 11 kW Motor need 11 x 300 = 3,300 m³/hour
If the air flow is restricted on the inlet or outlet side, this causes the compressor to run unnecessarily hot and will immediately reduce the filter duration and the life of the compressor. For this reason, the compressor must have a sufficient supply of fresh air to the compressor and the possibility to let the warm air exiting the block to dissipate naturally or even better to be extracted with an extraction fan.
If the compressor is not supplied with a high enough flow of air through an opening in the wall or a correctly positioned open window or door, then a ventilator will be necessary to artificially provide the amount of air necessary.
Time and money invested in the correct cooling requirements will pay off if efficient filter duration.
Air Filling connections
The air filling connection on filling hoses or direct filling connections is a customer specification which needs to be stipulated in the order. The following fittings are available as standard
- DIN 477: 200 bar, 300 bar.
- INT/Yoke/A Clamp: 200/232 bar.
- CGA 346/347: 3000 psi, 4500 psi.
If you have special requirements, please contact us, we will be happy to give you a quote on a special charging connection.
Anti Whip Safety connections
When a filling hose is used as the connection between a lever filling valve and the filling connection, there is the danger of inadvertently opening the valve without the filling attachment being fitted to a cylinder. This results in a free flow of high pressure air which causes the hose and connection to whip around out of control. Needless to say, that the operator is in the immediate area and that this is a major cause of injury and may even be fatal (head injury etc..).
To prevent this, L&W has developed and patented safety connections for DIN 200 and DIN 300 filling connections. These are highly recommended for lever valves fitted with filling hoses.
A compressor with an auto Stop will switch itself off automatically when a pre-set end pressure is reached. This is particularly useful if the compressor is not attended throughout the filling process. If the compressor does not switch off automatically and an attendant does not switch the compressor off when the final pressure is reached, the over pressure safety valve will be activated to prevent the pressure exceeded the safety limits. The over pressure safety valve is normally purely for safety and should not open/close with each filling procedure, if this happens then it will ultimately need servicing. Due to the safety consideration, these valves cannot be serviced by anyone except the manufacturer (L&W).
The automatic condensation bleed or "auto drain" is an electrically controlled circuit with magnetic valves and timers which automatically opens the drain valves on the oil/water separators. This is particularly important if the compressor is running for exended periods, i.e. to fill storage tanks, or when the compressor is attached to a multi point filling ramp. The condensation should be bled every 15-30 minutes manually if an auto dump is not fitted. This option can only be fitted to compressors with an electrical supply or 12V circuit.
Breathing Air Standards
The air that leaves the compressor´s final stage is contaminated with oil, has an unpleasant smell and a relatively high level of humidity. Before it is used for breathing or laboratory applications it needs to be filtered. After the filter, the Air meets the following international purity standards:
- EN 132 & 12021
- DIN 3188
- ISO 2533
- BS 5001 & 4275
- CGA Grade D & E
The most effective and economical method of controlling the quality of the air is by using a humidity controller such as the L&W Puracon.
Cross design filling valves
These simple filling valves are fitted at the end of the filling hose from a compressor and have hand wheel valves for opening and closing the valves and a hand wheel venting valve. Repair kits are available. The Valves have a port for a glycerine filled pressure gauge if required and can be equipped with almost any filling connection.
Delivery Rate or Capacity
Each compressor has a specific delivery rate which is the amount of free air that the compressor delivers (sometimes referred to as FAD). From the delivery rate, the speed at which a cylinder is filled can be calculated, for example:
- 450E compressor, 450 Liters/min filling 4 12 liter cylinders from 30 to 215 bars:
- 12 x (215 – 30) x 4 = 8800 Liters of air required.
- 8800 / 450 = 19 minutes 45 seconds, or approx. 20 minutes.
Direct filling connections
Direct filling connections are usually used for SCBA applications or where lightweight carbon fibre cylinders are filled. The cylinders are screwed directly on to a charging connection. Because of the design, we can only offer this feature on our filling panels or the 300/450 series compressors.
Emergency off switch
This is a over size switch which can be hit and activated to immediately stop the compressor if there is a problem or an accident.
Filling hoses are supplied for filling cylinders which are two large or heavy to attach directly to direct connections. The L&W hoses are pressure tested with certification and a burst pressure of 4000 bars (58,800 psi)! the hoses have a standard M16 x 1,5 mm Fitting, but can be supplied with any customer requirement on request.
L&W has 2 type of valves for filling cylinders. The self venting lever operated filling valve and the cross design filling valve with a separate vent screw.
The final pressure is the desired working pressure of the cylinders to be filled and is secured by a pressure relief valve.
Hours Counter (highly recommended for the 160E & 225E)
An hours counter monitors the running hours of a compressor. There are 2 basic types of hours counter, the vibration type and the electrically activated type which are 100% accurate. L&W only fits the electrical type for reliability and accuracy which means that they can not be fitted to compressors without any power supply, (190B, 245B). If no hours counter is fitted, the running hours should be registered in a log book with maintenance intervals.
Lever operated filling valves
The lever operated filling valves are fitted as standard to the L&W filling ramps and the 210ES and 260ES compressors. The valves are self venting with a rubber seal around the lever preventing contamination or sand entering the working parts. The valves are fitted with a sinter filter in the inlet side which protects the working parts from any damage.
The valves are extremely easy to service and maintain, they can be dismantled form the outside without the need to remove them from the housings. Repair kits are available for the valves. There is a special tool necessary for the filling panel valves, please contact us for more information.
The lever valves in the filling ramps are particularly quiet as the venting outlet is inside the filling ramp housing. This outlet can either be equipped with a purpose built silencer to further reduce the noise level during venting, or with a piping to allow the vented air to exit the filling ramp and be piped outside, (recommended if cylinders are frequently vented via the filling ramp and refilled with fresh air).
Motor Protection Switches
Extra electrical switches which monitor the current to the electrical motor and cuts the motor off if this current exceeds pre set levels. This provides extra protection for the electric motor and prevent overheating in the event of excessive load.
Nitrox Filling connections
The Nitrox filling connection on filling hoses fitted to Nitrox/Trimix filling panels or on special filling ramps is a customer specification which needs to be stipulated in the order. The following fittings are available as standard:
- DIN 477 Oxygen G ¾“
- EN 144 Nitrox M24 x 2.0 (Draeger/Scubapro)
Standard Air Connections, please refer to local gas regulations/guidelines.
A non return valve is a valve which allows the flow in one direction only. The pressure maintaining valve is also a non return valve and in nitrox/trimix filling panels are installed to prevent unwanted gas supply from one area to another for safety reasons. Another recommended application is immediately after the puracon sensor to prevent humidity getting to the sensor if a filling valve is left inadvertently open.
L&W compressor oil is a full synthetic oil safe for use in breathing air applications. We have done extensive testing to develop the right oil for our units which reduces the carbon build up and moisture build up. This ensures the valves have a very long life. We guarantee our compressors only if the original oil is used and changed according to the maintenance schedule. The L&W compressor oil is particularly good for warm climates where mineral based oil produces carbon and reduces valve life.
Oil pressure monitoring
Monitors the oil pressure and automatically stops the compressor if the oil pressure is under the pre-set level preventing damage to the compressor. Although L&W compressors use a low oil pressure lubrication system, this option offers additional safety especially for compressors which are running for extended periods in separate compressor rooms.
Oil temperature monitoring
Monitors the oil temperature and automatically stops the compressor if the oil pressure exceeds the pre-set level preventing damage to the compressor. Although L&W compressors use a low oil pressure lubrication system, this option offers additional safety especially for compressors which are running for extended periods in separate compressor rooms.
Paint Finish & Powder Coating
The steel plate housings and panels of L&W Compressors are powder coated, the most environment friendly method of colour finishing metal components off with a sturdy abrasion resistant finish. This method is becoming more and more popular in the automotive industry. The standard L&W Colour is Opal Green RAL No. 6026.
The Compressor Blocks and Cooling Pipes and coated with a corrosion protection finish where applicable but we do not spray paint our blocks after they are assembled. The reason for this is twofold:
- the paint would reduce the cooling efficiency of the pipe work which cools the air down between the stages, and
- any repair or maintenance work can be carried out without leaving traces of tools on paintwork.
Piston with Piston Rings
The efficiency of the compression and therefore of the compressor is dependant on the seal between the piston and the cylinder. The final stage of the compressor is the most important stage where the efficiency is vital. All our compressors are fitted with steel piston rings for vary long life times. This allows the compressor to run on a normal low pressure oil system which is much more reliable and less prone to failure that a high pressure lubrication system, found in some compressors with floating pistons in the final stage.
Pressure Maintaining valve
The pressure maintaining valve is a device which maintains a minimum pressure in the filter housing. The valve which is situated after the filter housing opens at approx. 170 bars (standard, can be set to individual requirements). The function of the valve can be periodically checked by observing the pressure gauge when the filling valves are closed. The compressor will start up and the pressure gauge will show 0 bars and will then suddenly show an increase in pressure when the valve opens at around 170 bars.
Pressure relief valve
Pressure relief, or safety valves are used to ensure that a certain pressure is not exceeded. The valves are fitted to each stage of the compressor and when they open, this indicates that there may be a problem with the following stage in the compressor. The final pressure is also secured with a pressure relief valve. There are 2 types of pressure relief valves, the standard L&W valve and the type tested L&W valve. The valves are manufactured and set up in our factory and then sealed to prevent unauthorised tampering. Because of the regulations, we are not able to supply spare parts for these valves, they must be returned to us for repair/replacement.
The final pressure safety valves are set slightly above the final filling pressure to ensure that the valve does not open in normal operation (assuming the compressor is cut off when the final pressure is reached). L&W safety valves can be supplied for all applications from 100 through to 350 bars. The standards setting for filling pressures are as follows:
|Filling pressure (bars)||200||232||300|
|Safety Valve setting (bars)||225||255||330|
A EEC Certificate of conformity is available for the type tested safety valves. These type tested valves are required for units with manufacturer’s certificate or certification.
Star Delta Start
The 260 and 450 series compressors from L&W are fitted with a star delta start cycle as standard. This circuitry allows the compressor to run up slowly at first to reduce the strain on the electric motor and on the power supply. The power is fed initially to each of the 3 poles in turn and then a timer cuts in and provides power to all 3 phases for the full speed. The star delta start cycle can be heard when the compressor starts up.
3 and 4 Stage Compressors
The compressors have a number of stages where the air is compressed from atmospheric pressure up to the final working pressure. A stage compressor accomplishes this in 3 and 4 stages. Between each stage, the air is cooled down before entering the next stage for compression. By using large dimension cylinders and long stroke pistons, the L&W compressors can provide a high capacity even at relatively slow running speeds with 3 and 4 stages.