Testing an Air Compressor

Testing with the Airometrix LP Flow Meter is simple, quick, and repeatable. The ideal meter tie-in location is after the aftercooler and moisture separator and as close to the output of the compressor as practical. This can be on a bung in a receiver, at a drop leg or tap in the compressor room, or at a service port where a portable compressor is typically connected. The main requirement is that the compressor is capable of being isolated from the system with the full flow of the compressor going to the LP Meter. Note the installation diagram below:

Testing the Compressor Performance

Once the meter has been plumbed in and the compressor has been isolated from the rest of the system, the compressor is started and the different orifices on the meter are opened and closed until the compressor can just barely keep up at system pressure. Add the valves which are open and this is the Free Air Delivered (FAD) of the compressor at the test pressure. In order to build a performance curve for the compressor, flow tests are performed at various pressures to determine the compressor output over a span of loads. This is accomplished by opening or closing more or less orifices and noting the changes in pressure with flow. It is recommended to take simultaneous true power readings (kW) on the compressor at each load point to get a full picture of compressor performance (flow, pressure, and power).

The performance data obtained from the test can be used to diagnose control function and other hard to measure performance information. It can also be used to chart inlet valve control, and accurately determine compressor power and flow turndown.

Testing for Leak Volume

Additional testing can be performed to determine system leak volume and consumption of equipment and processes. To test a system for leaks, the system is brought on-line without any equipment operating (usually performed on lunch breaks, off shifts, maintenance shifts, or annual shutdown), and a second flow test is performed on the compressor at the previously tested system pressure. The results for the second test with the system pressurized will be a lower air flow through the meter, the difference in the two tests is the leak volume in the system. For instance, if an isolated compressor is tested at 100psig at 1000cfm, and then retested at 100psig with the system pressurized and a flow of 600cfm through the meter, then the leak volume in the plant is 400cfm. If areas of the plant can be isolated, a leak test for each section can be administered and effort focused in the sections with the greatest volume of leaks.

Consumption Testing

Consumption tests can be performed using the same approach as the leak test which is to test before and after equipment is turned on and off. The difference in flow readings between the on and off conditions is the consumption of that piece of equipment. The same procedure can be used to test building consumption, process lines, or any other end use which can be isolated. A similar procedure can be used to find overall system consumption plus leaks when the plant is fully operational by testing each compressor off line one at time to determine the flows at full load. With the plant running, the compressors are brought to full load by opening orifices on the LP meter and the flow through the meter is subtracted from the known maximum capacity of all the on-line compressors. This is the consumption plus leaks for the entire system. If the leak volume has already been determined, the leak volume can be subtracted as well and the remainder is the consumption of the plant equipment.

In most facilities, only one meter is required to test all of the compressors for the system. The meter can be quickly disconnected from one location and moved to test another compressor as long as the meter is sized large enough to accept the compressor flow. Actual testing time is limited by how fast the compressor can react to a load change. Typical test time for positive displacement compressors is 10 minutes or less,  and one hour or less for dynamic machines.

Buying Guide for Air Compressors

Air compressors can be used for more than pumping up tires. In fact, these versatile tools can power nail guns, spray guns, wrenches and many other tools. Lowe’s is happy to provide this information as a service to you.

When shopping for air compressors, you ‘ll come across two basic types:

Types Of Compressor

Compact

Compact Compressor

Piston-Type Compressor

Piston-Type Compressor

    * Piston-Type Compressors have tanks that store compressed air. The motor shuts off when the pressure in the tank reaches a specified level. As air is depleted from the tank, the pressure inside drops, and the motor restarts to build the pressure back up. The pressure settings are adjustable according to the operator’s requirements. There are two kinds of piston compressors:
    * Single-Stage Compressors have one piston that compresses and delivers air to the storage tank. The single-stage system is normally found on light-duty compressors with a maximum rating below 150 pounds of pressure per square inch (psi). Single-stage compressors are adequate for most home users.
    * Two Stage Compressors have two pistons that compress and deliver air to the storage tank. The first piston compresses the air and pushes it through a check valve to the second piston. The second piston further compresses the air and delivers it to the storage tank. The two-stage system is usually found on commercial heavy-duty compressors with maximum ratings above 150 psi. Two-stage compressors are good choices for continuous use or shop environments.
    * Compact Air Compressors are the smallest and lightest compressors available. These compressors don’t have storage tanks, so they must run continuously to supply air. Compact compressors power caulk guns, glue guns, small spray guns, and can inflate sports equipment and tires.

Other Considerations

Horsepower Ratings are a measure of the horsepower (HP) the compressor motor produces. Compressor motors generally range from 1.5 HP to 6.5 HP. More powerful units are available for industrial applications. Usually higher horsepower motors yield greater psi and are capable of carrying a heavier workload.

Compressor Storage Tanks are rated in gallons. Larger tanks store more compressed air at higher pressures. The amount of air a compressor delivers is measured in cubic feet per minute (CFM). Note that the CFM a compressor delivers changes at varying psi. Most air tools have specific requirements for volume and pressure. These requirements must be met for the tool to function properly. When choosing a compressor, consider the tools you want it to operate. Select the tool that requires the highest CFM at the highest psi, and add 50% to the required CFM for a margin of safety. For example if a tool requires 3 CFM at 90 psi, select a compressor that delivers at least 4.5 CFM at 90 psi. Use this formula to ensure that the tool receives enough air to function properly.

Maintenance:

    * Oil-Free Compressors have sealed bearings and require less maintenance than oil-lubricated compressors. Oil-free compressors have plenty of power for most noncommercial uses.
    * Oil-Lubricated Compressors require the user to change the oil regularly. (Consult the owner’s manual for specific intervals). Most industrial compressors are oil-lubricated.

Power Supply:

    * Electric-Powered Compressors are the most common and are easy to use in any area with a ready electrical supply.
    * Gas-Powered Air Compressors are a good choice for areas where electricity is limited or unavailable. Don’t use gas-powered compressors in confined or unventilated areas.

Different Air Tools for Use in Construction

There is a wide range of handheld hydraulic and pneumatic construction equipment available for use in breaking pavement and rock, drilling and sandblasting. These include pick and demolition hammers, light, medium and heavy breakers, rock drills, cut-off saws, core drills, water pumps, ground rod drivers, post drivers and post hole borers. The use of air compression for construction tools is very convenient because they will normally use the energy of compressed air as opposed to electricity. Of course, when using a pneumatic power tool, you will need an air compressor. An air compressor is quite a big, loud piece of equipment and when you are using it you will need to wear safety glasses, ear muffs, safety gloves and a hard hat. Most air compressors will run on diesel, and basic maintenance checks should always be conducted before operation. The power of compressed air can be dangerous, and caution must always be adhered when an air compressor is in use. There are strict safety rules to abide by when using pneumatic power tools. It is important to conduct inspections before operating the tool in question. The air hose must be checked for cracks or holes, and if anything suspicious is found, the hose must be replaced immediately. Before you connect the air hose to the air compression outlet, open the valve. You will want to be sure that the air is flowing smoothly and strongly. After doing this connect the tool’s hose to the outlet and then ensure that the hose is clear of any water or foreign objects before you connect the hose to the power tool. When doing this do not point the hose at another person, because the force of the air is dangerous. Remember to always turn the valve off at the outlet first before you disconnect the hose. Air breakers are designed for general demolition, and are probably one of the most popular pneumatic power tools on the market. An air breaker will be used to break medium and hard materials such as concrete and asphalt. Prior to operation of an air breaker, you must always check that all parts are securely fastened. The hoses and connections will then be checked for possible damage or leakage. The breakers shank must be greased to ensure that it glides smoothly through the material you are wishing to break. Lastly you must check the built in lubricator for air oil. Always be careful to ensure that the air supply is off before you remove the oil plug, because if you do not, you could end up with oil squirting in your face!A rock drill is probably another popular pneumatic power tool you will come across if you are using an air compressor to power your construction work. A rock drill is designed for heavier jobs such as bench and secondary drilling, and can also be used for drilling for smooth blasting. There are some rock drills that can drill holes up to 6 meters deep! Before operation of this tool, besides the normal hose checks, you must ascertain that the drill steel’s flushing hole is clean and open. The lubricator must be full, and remember that the air supply must be off when conducting this inspection! As mentioned before, there are a plethora of pneumatic air tools for you to use as an alternative to those powered by electricity. Safety clothing must be worn at all times and a pneumatic power tool must never be used by someone who has no experience or training in this area.