Compressed Air Transmission and Treatment:Commissioning and safety

Commissioning and safety

Pressure testing of the system

After the installation of the main and branch lines and immediately before connection of the compressor, the whole system should be subjected to a hydraulic test (making sure that the water has an added anti-corrosion agent) to 1.5 times the working air pressure, and all leaks remedied. The date of the test should be recorded and attached to the pipe system where it connects to the air receiver. This test should be repeated, for convenience at the time the air receiver is similarly checked, and when substantial changes are made to the layout of the system. After test, the whole system must be thoroughly blown out with low pressure air.

The reader is referred to the BCAS publication “Guide to the selection and install­ation of compressed air services” which gives useful information and data. It should be used to complement the information in this chapter. There are also a number of publications of the Health and Safety Executive which give information specific to industries using compressed air. A list of these and other safety publications are given at the end of the chapter.

General safety guidelines

• Compressed air can be dangerous unless straightforward precautions are taken.

These are mostly common sense, but nonetheless worth listing. In a place where compressed air is used, consideration should be given to placing these or similar guidelines in a prominent place.

• Only approved pressure vessels built to the correct standards should be used. Refer to the chapter on Air Receivers.

• It is essential that a non-return valve and shut-off valve are fitted into the delivery line when the compressor is to be coupled in parallel with another compressor or connected to an existing air supply system; in such cases a safety valve must be provided upstream of the valve, unless one is already fitted to the compressor.

• Distribution pipework and hoses must be of the correct size and be suitable for the expected maximum working pressure. The tightness of compression fittings must be checked regularly.

• Do not use frayed or deteriorated hoses; always store hoses properly and away from heat sources or direct sunlight. A hose failure can cause serious injury.

• Use only the correct type and size of hose end fittings and connections; use only clamps or robust construction made specially for compressed air and rated at the maximum pressure in the system.

• Use eye protection if using compressed air for cleaning down equipment. Do so with extreme caution. Take care never to blow dirt at people or into machinery. Always use a blow gun never an open hose.

• When blowing through a hose or airline, ensure that the open end is held securely; a free end will whipandcauseinjury; open the supply cock carefully and ensure that any ejected particles will be restrained. A blocked hose can become a compressed air gun.

• Never apply compressed air to the skin or direct it at a person; even air at a pressure of 1 bar can cause injury. Never use compressed air to clean clothing.

• Do not use air directly from a compressor for breathing purposes, unless the system has been specifically designed for such a purpose and breathing air filters and regulators are fitted- see chapter on Breathing Air Filtration.

Precautions during commissioning

Before installing air line filters, pressure regulators and lubricators, low pressure air should be blown through the system to remove any foreign matter.

• Before removing any blanking flanges and plates from the compressor, it is important to make sure that the pressure in the compressor is released.

If an isolating or non-return valve is fitted into the compressor discharge, it is essential to check that an adequate safety valve is fitted between this valve and the compressor and that the isolating valve is open.

• Before starting up the compressor plant it is essential to carry out the instructions issued by the supplier in respect of the initial charge of lubricating oil (if any) , the setting of the lubricator feed (if a force feed lubricator is used), and the cooling water supply (if applicable).

Before starting any machinery, all protective guards should be in position and secure.

• On the initial start, the directions of rotation of the compressor must be checked; severe damage may be caused if the compressor is allowed to turn in the wrong direction.

• Before connecting any equipment to an airline lubricator, the pipe or hose should be allowed to discharge freely to atmosphere until visible traces of lubricant are obtained; then equipment can be connected and the lubricator adjustment set. Initially, oil from the lubricator does little more than line the pipes.

• During the first few hours of operation, the performance of the plant should be monitored carefully, in particular the operation of any automatic drains from the intercoolers and aftercoolers.

Precautions during running

• It is always good practice to keep a log of oil consumption, temperature and pressure, interstage and final temperatures and pressures and water inlet and outlet temperatures, so that any deviation from normal running may be noticed quickly. When an abnormality is noticed, the compressor must be stopped and the matter investigated. Power consumption should also be recorded.

• Suppliers’ recommendations regarding filters and elements should be observed during and after the initial running-in period.

• The system should be checked regularly for leaks (see the chapter on Compressed Air Distribution).

• Never operate any part of a compressed air system – compressor, pipework or pneumatic appliance- at a higher pressure than for which it was designed or rated. If any equipment has a design pressure less than the maximum output pressure of the compressor, it shall be protected by suitable fail-safe means against over pressure.

• Shut off the adjacent upstream isolating valve and release the air pressure before disconnecting a hose or line, unless there is an automatic valve to give protection at the upstream joint.

Precautions during operation

• Keep doors shut on silenced plant. On other plant, check whether it should be run with doors open or shut.

• Check that all pressures and temperatures are correct; refer to the operating instructions.

• Stop the plant if warning lights show or if gauges register outside the normal limits; untrained personnel must not attempt adjustments. Call in a plant fitter to investi­ gate.

• Do not make adjustments inside the canopy when the machine is running, unless appropriate precautions are taken.

• Do not remove guards.

• Do not use the machine in a fire hazard area unless it is suitably designed; do not operate in the vicinity of toxic fumes.

• Ensure that all pneumatic control equipment and air line accessories are operated below the maximum rated pressure and temperature.

Precautions during maintenance and overhaul

• Ensure that all air pressure is completely released from the system and that it is isolated from any other air systems. In multi-compressor installations, repairs to any of the compressors shall not be carried out whilst the other compressors are working, without first closing the isolator valve and venting and disconnecting the delivery pipe of the compressor to be repaired.

• Ensure that a machine cannot be started inadvertently; isolate the unit and lock the isolator in the safe position; place warning notices on isolator.

• Ensure that any door that opens upwards is securely fastened when open, and that no door can slam shut.

When working on plant:

• Use correct lifting gear of adequate capacity.

• Examine condition of lifting gear before lifting plant.

• Use correct tools for the job.

• When using a chemical or solvent cleaner, follow the manufacturer’s instructions.

Be sure that any fluid used cannot cause any chemical reactions or explosion in combination with high pressure. Do not use halogenated hydrocarbons on equip­ ment where aluminium or galvanised parts come into contact with solvent or coating material. Trichloroethane and methylene chloride react violently with such parts, causing corrosion and very high pressures if entrapped.

• Do not weld or perform any other operation involving heat near the electric or oil systems. Oil and fuel systems must be purged completely, for example by steam cleaning before any welding repairs are carried out.

• Do not weld or in any way modify any pressure vessel.

Precautions before clearing the machines for use

• Check that the sump is filled with the correct grade of oil. Before using synthetic lubricants ensure that they comply with the compressors manufacturer’s instruc­ tions and are compatible with all downstream equipment. The long intervals between oil changes permitted by synthetic lubricant manufacturers may lead to neglect of essential servicing of compressors, including filter changes, unless the maintenance schedule is strictly followed.

• On water cooled units check that the coolant is flowing.

• Check direction of rotation.

• Check that the operating pressures, temperatures and speed are correct and that the controls and shut down devices work correctly.

• Every six months examine the discharge pipe and discharge pulsation damper for carbon deposits; if excessive, the deposits should be removed.

• Isolating valves which should be of the self-exhausting type, should be designed for locking in the “off’ position. When servicing pneumatically-operated machines, Jock the isolating valves so that air pressure cannot be applied inadvertently while the machine is being worked on.

• Maintain filters in accordance with the supplier’s instructions, as a reduction in air pressure caused by choked filter elements could result in a malfunction.

• Inspect hoses, flexible lines and plastic pressure-containing components at regular intervals and replace if signs of cracking, crazing, or any form of mechanical damage are evident. If sight glasses or filter bowls are becoming obscured due to internal contamination or scratching, these should be cleaned or replaced.

Portable compressor safety

In addition to the general rules listed above, the following apply to portable compressors:

Towing the compressor

• Check the towbar, braking system and coupling. Check that the wheels are secure that tyres are in good condition and correctly inflated.

• Connect lighting cables to towing vehicle if applicable. Check correct operation of lights.

• On two-wheel plant, raise propstand and jockey wheel fully and lock.

• Ensure breakaway cable is secured to towing vehicle.

• Release the hand brake.

Before starting the compressor

Check that:

• The machine is secure with brakes applied and level within 15 degrees.

• The machine is clean internally.

• All air pressure is released from the machine.

• All hoses and tubing are in good condition, secure and not rubbing.

• No fuel or coolant leaks.

• All fasteners are tight.

• Oil and coolant levels are correct; top up only with correct oils.

• All electrical leads secure and in good condition.

• Fan belt tension correct.

• All guards in place and secure.

• Engine exhaust system in good condition, and no combustible material lying on or against it.

• Start and stop procedures must be understood and carried out. Before starting close the air discharge cocks. Refer to the operating instructions.

During operation

Do not fill with fuel while the machine is running. Keep fuel away from hot pipes.

• Ensure that the engine exhaust is freely vented to atmosphere.

• Do not remove the oil filler cap or the radiator cap.

• Do no adjustments inside the canopy when the machine is running, other than where instructed.

• Do not disconnect the battery.

After stopping

• Ensure that all air pressure is released from the system.

• Allow radiator to cool before removing the radiator cap. Allow engine to cool before adding coolant.

• Remove starting key if fitted and close panel doors.

Maintenance and overhaul

Before starting work on any machine:

• Ensure that all air pressure is released from the system.

• Stand the plant on a level ground.

• Apply the brakes. Securely fix propstand and jockey wheel on a two wheeled plant.

• Chock wheels securely if jacking-up or if working on the brakes.

• Support towbar on a two-wheel plant.

• Support axles securely if working underneath or removing a wheel. DO NOT RELY ON JACKS. Support tow bar on a four-wheel plant.

• Ensure that the machine cannot be started inadvertently.

• Disconnect battery. When working on the plant:

• Use lifting gear of adequate capacity.

• Examine the condition of the lifting bale before lifting machine by it.

• Use the correct tools for the job.

Maintenance and repair and tools

• Disconnect the machine from the air supply before doing any work on it.

• For dismantling, hold the machine tirmly in a vice or fixture.

• Use the correct tools for dismantling and assembling.

• When using a solvent or chemical cleaner, follow the manufacturer’s instructions.

• Ensure that any components that require replacement are those recommended by the manufacturer.

• Before clearing the machine for use, make sure that it has been assembled correctly with all fasteners correctly tightened.

Use of machines and tools

• Use only approved tools. Make sure that the tool shank is the correct size for the machine.

• Do not use blunt tools or those which are worn excessively or damaged in any way on the shank or stem. A TOOL WHICH BREAKS IN USE CAN CAUSE SEVERE INJURY.

• Do not use frozen tools. In freezing conditions, store tools undercover, preferably in a warm building. Freezing temperatures cam make hardened steels brittle and cause breakage.

• Lubricate the machine as instructed. Use an approved lubricant.

• Blow through the air supply hose with compressed air before connecting to the machine.

• Connect the hose to the machine before turning on the supply. Ensure that the machine controls are in the “Off’ position.

• Position the machine correctly and hold it firmly before operating the controls.

• Persons operating, assisting or working near the machine should position them­ selves so that they will not be struck or lose their balance if the machine slips or if the drill steel or tool breaks or sticks.

• Do not operate the machine from an insecure footing or staging.

• Where dust is a hazard in rock drilling, use the appropriate dust suppression methods, either dust collectors in quarrying or wet drilling underground.

Wear ear muffs or plugs when operating noisy equipment. The use of silenced equipment, even to EEC standards is no guarantee that the hearing will not be damaged with continued use.

• Noise reduced mufflers fitted to machines lessen the health hazard and reduce environmental noise. Detachable mufflers must be fitted correctly and replaced when damaged. On no account modify the exhaust ports.

• When using vibrating tools continuously and particularly in cold weather, wear suitable protective gloves and keep the hands warm.

• Use vibration reduced equipment where available. Avoid holding the tool bit to guide the work without the use of gloves. Do not start work until the hands are warm. These precautions will help to reduce the incidence of vibration induced white fingers (sometimes known as occupational Raynaud’s disease).

• Always turn off the compressed air supply and release the air pressure in the supply hose before changing the tool, removing the oil filler plug or disconnecting the hose.

• When handling lubricants regularly, wear suitable gloves of impervious material.

Clothing contaminated by lubricants should be changed.

• Should any lubricant be ingested, seek medical advice immediately.

• When using pneumatic tools, ensure that the area is adequately ventilated. Concen­tration of oil mist in the air can be dangerous.

• Do not operate a machine at full power without the drill rod or breaker steel securely retrained in the chuck and the steel or bit in contact with the ground.

Safety publications

• For Safety Regulations on the use and manufacture of pressure vessels refer to the chapter on Air Receivers

The following publications should be referred to for detailed advice on safety:

• The Factories Act 1961. Sections 36 and 37 deal with air receivers and are of particular interest to users of compressed air equipment.

• Control of Pollution Act 1974. Section 68 deals with noise from plant and machinery

• Health and Safety at Work Act 1974. Section 6 deals with the general duties of manufacturers and suppliers of equipment. Under Section 15 of the Act, the Secretary of State may make Health and Safety Regulations and a number of these have already been made, in particular:

• Noise at Work Regulations SI 198911790

• Control of Substances Hazardous to Health Regulations SI 1994/3246.

• Protecting Hearing at Work, published by CBI.

The following books published by Health and Safety Executive and obtainable from HSE Books contain useful material for those involved in the use of pneumatic equipment:

• Safety in pressure testing GS 4.

• Safety in the use of abrasive wheels HS(G) 17.

• Compressed Air Safety HS(G) 39.

• Noise at work HS(G) 56 Noise Guides 1 to 8.

• Hand Arm Vibration HS(G) 88, gives useful advice on the purchase of equipment and means of reducing vibration.

• The assessment of pressure vessels operating at low temperature HS(G) 93.

• Control of Noise in Quarries HS(G) 109.

• Noise from pneumatic systems PM 57.

• Occupational exposure limits EH40. To be used with the Control of Substances Hazardous to Health Regulations. These limits are updated every year and so the latest issue should be used.

Other miscellaneous publications:

• Compressed Air Safety. Guidelines for the safe use of compressed air in quarries, published by British Quarrying and Slag Federation.

• BS 4575-2 Code of practice for pneumatic equipment and systems.

• BS 6244 Code of Practice for stationary air compressors.

• Recommendations for the Proper Use of Hand-held or Hand-operated Pneumatic Tools. Pneurop Publication, available from BCAS.

• A guide to compressor noise reduction BCAS.

Related posts:

Applied Pneumatics:Flow analysis for cylinders and valves
Valves and Sensors:Control valves
Compressed Air Transmission and Treatment:AIR DRYERS
Energy and Efficiency:Experiments with two level operation
Coarse material:Procedure and Operating point.
COMPRESSORS:Axial Compressors
Preventive maintenance.
The air relay and the force balance principle.
Compressor types:Piston compressors,Screw compressors,Rotary compressors and Dynamic compressors.
Air Compressors, Air Treatment and Pressure Regulation:screw compressors

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