Air Compressors (1)

The compressed air powering your equipment has many essential properties. Pay attention to these properties, and you’ll be rewarded with smooth, trouble-free performance of the air compressor itself as well as the productive machinery being powered by the compressed air. Ignore them, and you’ll be leaving yourself open to lost production time, higher utility costs, and more frequent repairs.

COMPRESSED AIR CAN BE DANGEROUS!
BEFORE ATTEMPTING ANY MAINTENANCE TO YOUR AIR COMPRESSOR OR COMPRESSED AIR SYSTEM, BE SURE THE ELECTRIC POWER IS OFF, NO SAFETY DEVICES HAVE BEEN DEFEATED, AND THERE IS NO AIR PRESSURE LEFT IN THE COMPRESSED AIR SYSTEM

MAJOR COMPONENTS
ELECTRIC MOTOR– Provides the torque required to operate the pump. There are two types of motors, a single-phase motor and a three-phase motor. Single-phase motors are typically used in compressors that require lower levels of horsepower (typically 7.5 HP or less) or when three-phase power is unavailable. These motors are generally capacitor start/capacitor run and are easily identified by the protrusions on top of the motor containing the capacitors. Fortunately, most compressor motors do not require maintenance unless grease fittings are on the end bearings (these fittings are generally found on larger motors in exceeding 7.5 HP).
PUMP– The heart of the compressor, which converts the rotational energy of the electric motor into the potential power of pressurized air. There are several families of compressor pumps. However, I’m limiting the family of compressor pumps under discussion to only the reciprocating type. This family of compressors is the most common in our industry and uses pistons moving inside cylinders coordinated with associated valves to compress the air. In an air compressor, the electric motor provides rotary force linked to a fly-wheel (usually via belts) which rotates a crankshaft. The crankshaft translates this rotary motion into reciprocating (up and down movement), sliding a piston inside a cylinder. At the top of the cylinder there is a set of reed valves, an intake and an exhaust. On the piston downstroke the intake valve opens, allowing air to be sucked into the cylinder while the exhaust valve shuts, isolating the pump cylinder from the stored compressed air in the receiver. On the upstroke of the piston, the intake valve closes, and the exhaust valve opens, enabling the rising piston to compress the air in front of the piston head while also providing an exit path from the cylinder into the receiver (tank). As you can imagine, there are many moving parts in this portion of the compressor, along with seals and gaskets requiring lubrication. All this linear and rotary motion must occur in an oil bath to reduce friction and wear. The oil is engineered for the type of lubrication service required for air compressors (DO NOT USE MOTOR OIL IN AN AIR COMPRESSOR). Keep in mind that not only must the oil be designed to be compatible with the rubber, plastic and metal parts in the compressor it must not degrade components in the machinery that will be using the compressed air. The oil level contained in compressors should be checked weekly. There’s generally a small round sight glass or a dipstick located towards the bottom of the compressor pump. With the compressor shut off, a level of about ½ way up the height of the sight glass or at the proper marking on the dipstick should be visible; if it’s low or not visible, add oil. The oil itself should be drained and disposed of properly and then replaced at least once annually. Fill and drain plugs are usually located near the sight glass or dipstick.
A second maintenance point is the belts coupling the electric motor to the compressor pump. They are subject to wear and need to be monitored at least monthly. You’ll know when they begin to fail because you’ll hear them squeal when the compressor starts. Do not use “belt dressing” to avoid adjusting or replacing failing belts.

BE SURE THE ELECTRIC POWER IS OFF BEFORE ATTEMPTING TO ADJUST OR REPLACE BELTS, AND ALWAYS REPLACE THE BELT GUARD WHEN FINISHED

When the belts are properly adjusted pressing your thumb against the outside surface of the belt about ½ way between the motor pulley and fly wheel should result in about a ½ inch deep arc on the belt. When adjusting belt tension do not overtighten the belts, this causes premature belt wear and bearing failure. Look carefully at you belts. If there are loose threads, separations between layers of rubber or cracks across the face of the belt don’t wait, replace them. Belts should always be replaced in sets with the same specifications as the originals.

RECIEVER– Also called a tank, stores the compressed air serving as a reservoir to store the compressed air. Additionally, it damps pulsations from the compressor’s discharge line, resulting in essentially steady pressure in the compressed air system. It also prevents frequent cycling (the starting and stopping of the compressor). Water vapor condenses, and oil carries over into the receiver, where it accumulates. Therefore, it’s necessary to drain the accumulated water and oil from the receiver regularly. Draining the receiver is accomplished by opening a drain valve located at the bottom of the receiver while the receiver is pressurized, allowing pressurized air to blow the water and oil out the bottom of the receiver.