Air compressors power…
(1) industrial equipment and (2) construction tools
Examples of equipment powered by air compressor
pneumatic wrenches, lifts in auto service stations, paint spray booths
Air compressors enable…
(1) efficient repair of all types of vehicles; and (2) facilitate their safe operation on public thoroughfares
Permit is required for air compressor
that compresses air above 100 PSI
Types of air compressors
(1) reciprocating;
(2) centrifugal;
(3) solar; and
(4) rotary
*Difference is the way in which they compress air
How do air compressors work
take the air in a room and force it into a container UNDER PRESSURE. The more air forced into the container, the greater the pressure. Compressed air can be discharged from the container at a controlled rate.
Most common air compressor
Reciprocating
Air compressors are sometimes called
air pumps
Air compressors can be powered by:
(1) electric motors;
(2) internal combustion engines; or
(3) steam turbines
Explosions & air compressors
If there is a build up of flammable gases (ex: in service stations and workshops), those gases are heavier than air and fall to the floor before spreading outward. These gases are easily ignited by sparks and high temperatures–which INCLUDES the heat generated by an air compressor.
To avoid explosions w/ air compressors
Raise air compressor at LEAST 5 feet above ground level so that no flammable gases are drawn into the compressor. To meet the height requirement you can place compressor on a shelf or bench OR the air receiver tank may be turned and stood on end w/ the air compressor bolted to the top of the tank.
Power to air compressor
entire unit is driven by an electric motor. Motor activates a series of drive belts. Belts power the moving parts of the unit–like w/ power steering and alternator in automobile
Compression Chamber operation
Air is compressed in compression chamber which consists of a PISTON inside a CYLINDER. Piston moves up and down.
When piston moves down –>draws air into cylinder, through INTAKE VALVE (valve automatically opens when piston moves down).
When piston moves up–>air is compressed (intake vale automatically closes to avoid air escaping from cylinder).
Air Reciever Operation
When air pressure reaches a certain level, it forces open a DISCHARGE VALVE (which is spring loaded). This releases compressed air into air reciever (aka air tank), which is what supplies compressed air when needed.
Single Stage Air Compressor
with one cylinder and one piston
Multi Stage Air Compressor
with more than one piston and cylinder.
Each cylinder will increase the pressure of the air by taking air from the discharge side of the previous cylinder and increasing the pressure to a new level. Once it reaches the last level, the pressurized air is discharged into the reciever.
As air is compressed it becomes
heated.
This is why in a multi stage air compressor there is an intercooler between stages of compressor.
Exception to single stage/multi stage distinction
CAVEAT: there are air compressors with multiple pistons and cylinders that are single stage but these are only the ones where each cylinder discharges directly into air receiver (unlike a true multi stage air compressor).
Storage containers
some systems force the compressed air from the receiver into storage containers allowing it to be used later as needed.
System of Connected Air Compressors
Air forced from one compressor into another several time to increase pressure each time and ultimately forced into a hose line or storage container.
Used when there is a need for air under very high pressure.
Unloading Valve
safety component.
allows air to escape compression chamber when there is a strain on the electrical motor. This usually occurs in the first few cycles when the compressor is first started.
Automatic in most systems but it may be manual in older compressors. Follow instruction manual for old compressor.
Pressure Gauge
safety component.
Indicates pressure inside receiver. CF holder should pay close attention to reading. Must NEVER exceed manufacturer’s recommendations. If greater than recommended level there could be explosion. Pressure in the receiver is controlled by a switch; turn switch in the desired direction to adjust pressure.
Pressure Relief Valve
safety component.
Allows air to escape from the system when pressure is too great. Operate automatically. May operate manually by pulling on the ring attached to the pressure relief valve
Air intake valve
safety component.
Fitted w/ an air filter which prevents dust from being drawn into compression cylinder. Dust in the compressor could result in fire in the cylinder b/c of heat in the cylinder. Fire could case damage to air compressor.
This is why its important to make sure filter is always clean and securely connected to the compressor.
Filter & Moisture Separator Assembly (FMSA)
safety component.
Moisture can be a problem; this filter removes moisture from compressed air.
Installed between compressor and receiver.
Drain cock attached to FMSA to drain water and dirt.
Automatic Control Device
Attached to receiver.
Shuts down compressor when pressure in receiver is adequate and restarts when more pressure needed.
Safety Relief Valves
safety component.
keep compressor tank from bursting if pressures witch stops working
Constant Speed Control Switch
safety component.
Used when steady/constant demand for compressed air.
If demand drops excess compressed air is released through pressure release valve.
Cooling system
safety component.
compression chamber and compressed air must be cooled to avoid overheating.
Small compressors are air-cooled (fan).
Large compressors are water-cooled.
Low Oil Level Indicator Switch
safety component.
automatically shut down compressor if oil is low.
Serious damage can be caused if compressor is operated w/ low oil
Maintenance & Repairing Compressor- General Requirements
-always follow guidelines outlined by manufacturer.
Repair:
-always turned off
-electrical supply shutdown
-air drained
-made by qualified technician
Repairs by CF
-must know how to correct cooling system;
-may replace belts
-change air filter
-change lubrication oil
Leaks
CF must look & listen for leaks.
More prominent in colder months when sealing materials shrink.
Most leakage occurs at tubing and fittings at air reciever tank.
Heat & Compressor
-never place combustible materials nearby;
-do not use near devices that produce heat;
solar heat is not known to cause overheating
CF Responsibility
-visually inspect
-remain in area for a few minutes after compressor started
-do not operate at speeds above recommended ranged
Injury from Compressor
-Dust or debris blow off clothing can be driven under skin causing DEATH
-Eardrum ruptures at 40 PSI
-Air entering mouth can destroy lungs and internal organs
-Eyesight (always wear googles)
Hydrostatic testing
Fire Code no longer requires affidavit indicating reciever is hydrostactically tested and defect free.
HOWEVER, test every 5 years at a minimum is reccomended.
Cleaning Compressor
only using soap and water solution.
NEVER use benzene, kerosene or other light oils for this purpose. They may cause an explosion when mixed w/ air under pressure.
Both oil and water can cause an explosion if they actually enter the compressor tank.
Maintenance-Cooling System
Tested every 6 months.
Water supply control valves always open when compressor in operation
Maintenance-Air Intake Filter
Inspected/cleaned weekly.
Replaced every 6 months.
Replace if damaged
Maintenance-Lubrication Oil
Level checked weekly using dipstick
Replaced every 6 months
Refer to manufacturer manual for safe operating temperatures of oil and grade of oil needed.
Maintenance-Automatic Low level Oil Indicator Switch
Tested every 3 months by manually draining oil from compressor. Do not run compressor for a long period of time when testing this way.
Maintenance-Air Reciever
Tested every 5 years by qualified technician
Water buildup in moisture separator assembly and air receiver drained daily by opening drain valve EXCEPT when temperature below 40 degrees
Safety valves should be manually operated every week.
Maintenance-Hose Connections
Make sure tight, frequently.
Never twist, bend, curl to stop it.
Do not patch w/ duct tape.
Maintenance-Belts
Turn off compressor and disconnect power supply. If visibly damaged or frayed, replace.
To test tension, firmly press on belt. If it moves more than 1 inch, fly wheel needs to be adjusted. If this doesn’t work replace belts.
Maintenance-Electrical Connections
Visually inspect.
Notify electrician if evidence of defective parts. Special attention to motor starter (protects agst. thermal overload caused by excessive currents).
Maintenance-Pressure Switch
- Star compressor, allow air in receiver to build to normal operating levels while paying attention to gauge.
- When gauge indicates pressure above normal, compressor should shut down automatically. If not, pressures witch may be adjusted. If this doesn’t work switch is defective and MUST be replaced.
**SOME compressors operate continuously as their pressure switch device just prevents compressor from compressing air. to test this just make sure air is no longer compressing when level is reached.
Maintenance-Pressure Relief Valve
Run compressor w/ pressure switch fully open (when it is in this position it CANNOT shut down the compressor).
Should be set at NO LESS than 15 psi OR 10% above the operating pressure of the compressor (which ever is greater) BUT NEVER higher than max allowabe working pressure of receiver.
Maintenance-Operating Temperature
Acceptable temp are in the maintenance manual.
Overheating can cause damage to compressor and is a potential fire hazard.
If overheating discovered water cooling mechanism must be checked.
Lockout/Tagout Safety Procedures
Lock the device or the power source w/ a hasp and placing it in such a position that no hazardous power sources can be turned on. Also requires a tag to be affixed to the lockout device indicating it should not be turned on.
Know OSHA Standard for Control of Hazardous Energy (Lockout/Tagout) procedure.
Compliance w/ Lockout/Tagout
prevents 120 fatalities and 50,000 injuries each year.
Workers lose an average of 24 workdays for recuperation from exposure to hazardous energy.
The Cooling System
The cooling system should be tested every 6 months to make sure that it is working correctly.
The water supply control valves should always be open when the air compressor is in operation.
The Air Intake system
The air intake filter should be inspected and cleaned weekly. It should be replaced every 6
months. If at any time the filter is damaged it should be replaced.
The lubrication Oil
The Certificate of Fitness holder should refer to the manufacturer’s manual to determine the safe
operating temperatures of the lubrication oil. The level of the lubricating oil (lube oil) should be
checked weekly using the dipstick. The lube oil is designed to lubricate the moving parts on the
air compressor. The oil used must be of the grade specified by the compressor manufacturer.
The lube oil should be replaced every six months.
The Automatic low-level Inidicator
The automatic low-level oil indicator switch should be tested every 3 months. This is tested by
manually draining the oil from the air compressor when it is running. The indictor switch will
shut down the air compressor within a few minutes if it is working correctly. When testing the
compressor in this way, do not run the air compressor for a long period of time. If the switch is
defective, it should be repaired or replaced. The air
compressor should be refilled with oil before it is used again.
The air receiver
Water builds up in the moisture separator assembly and the air receiver must be drained daily;
however, there is one exception. Do not drain moisture from the air compressor when the
ambient temperature drops below 40 degrees Fahrenheit. This is done by opening the drain
valve and draining off the excess water. All safety valves should be manually operated every
week. This is to ensure that they will function correctly in case of an emergency. It is
recommended that the air receiver tank be pressure tested at a minimum of every 5 years by a
qualified technician.
The Hose Connections
All hose connections on the air compressor should be checked frequently by the Certificate of
Fitness holder to make sure that they are tight. Never twist, bend or curl an air hose to stop the
air hose. That’s the job of the air valve. You should not patch a leaking hose with duct tape. You
can replace the hose, or you can repair the leak by cutting out the bad section and joining the
hose back together with a connector and clamps. The safety valves and gauges should be
checked regularly to make sure that they are in good working order.
The belts
The belts must be inspected by the Certificate of Fitness Holder to make sure that the air
compressor is running at the correct speed. First turn off the compressor and disconnect the
power supply. If the belts are covered by a protective guard, remove the guard. If the belts are
frayed or visibly damaged they must be replaced. To test the belt tension, firmly press down on
the belt. If the belt moves more than one the inch, the flywheel may need to be adjusted. Make
the adjustments as needed. If the adjustment does not work replace the belts with the belts as
specified by the manufacturer.
The Electrical Connections
All electrical connections, fuses, and cables must be visually inspected by the Certificate of
Fitness holder. A qualified electrician must be notified if there is evidence of any defective
parts. The electrician must pay close attention to the motor starter. The motor starter protects
the compressor against thermal overload. Thermal overload is caused by excessive electrical
currents.
The Pressure Switch
It is essential that the Certificate of Fitness holder ensures the pressure switch is working
correctly. The pressure switch is a pressure regulating device. It shuts down the air compressor
when pressure in the air receiver reaches a certain preset level. Then it restarts the compressor
when the pressure falls below a certain level. The shut down and restart levels depend on the
size of the compressor and the demand for compressed air. The pressure switch prevents the air
pressure inside the tank from reaching dangerous levels. Dangerously high pressure levels may
cause the tank to rupture or explode. The steps to test the pressure switch are as follows:
What are air compressors used to power?
Industrial equipment and construction tools
What pressure compressor require a certificate holder to operate?
100+ psi
What are two examples of tools air compressors power?
Pneumatic wrenches and air lifts in automobile repair shops
What are the 4 types of air compressors?
Reciprocating, centrifugal, rotary, and solar
How can air compressors be powered?
Electric motors, internal combustion engines, and steam turbines
What can be done to prevent flammable gasses from entering air compressors?
Position the compressor 5 feet above ground
What does the compression chamber consist of?
A piston inside of a cylinder
When the piston moves downward, what happens to the intake valve?
It automatically opens and air is drawn into the cylinder
When air is compressed and the intake valve is close, which direction is the piston moving?
It is moving upward
When pressure reaches a certain level, what happens with the discharge valve?
It opens to allow air into the receiver
What is a single stage compressor?
A compressor that pumps air into the receiver after one step of compression from one or more cylinders and pistons.
What is a multistage compressor?
A compressor that discharges air between multiple cylinders before finally reaching the receiver, reaching a new level of compression after passing each cylinder
What happens to air when it is compressed?
It becomes heated
What cools the air after it’s been compressed?
An intercooler
What is the purpose of an unloading valve?
To allow air to escape when there is strain on the motor(usually during startup). Automatic in most cases manual on older compressors.
What ensures compressed air does not flow out when the unloading valve is activated?
The check valve
Where is the check valve located?
Between the compressor head air line and the unloading valve air line.
What can be read on the pressure gauge?
The pressure inside the air receiver
What allows air to escape when pressure is too great?
Pressure relieve valves
What is the purpose of the air intake valve?
It is fitted with an air filter and prevents dust from entering the compressor
What is the purpose of the filter and moisture separator assembly?
To remove moisture from the compressed air before it enters the receiver
What is the purpose of the automatic control device?
To start or shut down the device when desired pressure is reached or more pressure is needed.
What prevents the tank from bursting should the automatic control device malfunction?
The safety relief valve
When is a constant speed control switch necessary?
When a constant flow of compressed air is needed, it allows the compressor to run continuously at a safe speed
What is the purpose of the cooling system?
The compression chamber and compressed air need to be cooled. Small compressors are cooled by air and large ones are cooled by water.
What is the purpose of the low oil level indicator switch?
Shuts down the compressor if oil levels are low to avoid damage to the motor.
What should operators do before starting compressors?
Visually inspect the components to see if correctly installed and working
At what psi can an ear drum be ruptured?
40 psi
Are hydrostatic tests every 5 years required by the fdny?
No but they are recommended
Who should manage normal maintenance and small repairs to the compressor?
Operator
Who should manage major repairs to the compressor?
Qualified technicians
Who should manage electrical repairs?
A licensed electrician
What can be a cause of thermal overload?
Excess electric currents
How often should cooling systems be tested?
Every 6 months, water supply control valves open
How often should air intake filters be cleaned?
They should be cleaned weekly
How often should air intake filters be replaced?
They should be replaced every 6 months or if damaged at any time
How often should low oil level indicator switches be tested?
Every 3 months by draining oil manually while running
How often should fmsa be drained?
Should be drained daily unless surrounding temperature below 40 degrees
How often should hose connections be inspected?
They should be inspected for leaks regularly
How should belts be checked?
Check for any tears or physical damage. Push down firmly if moved more than an inch adjust flywheel. Replace if problem not solved.