Posts Tagged ‘air compressor’

We get this question a lot – so we developed a step by step set of directions to help you.

Download your PDF instructions here…

What does a pressure switch do?
Answer:  An air compressor pressure switch is a valuable part of your equipment.  The pressure switch tells your compressor when to stop and when to start and can help you save money and energy.

Need to order a pressure switch? Call us – 1-888-229-9999

Tommy McGuire McGuire Air Compressors
“Real People with Real Air Compressor Experience”



Ask a Question:
What are some good trouble shooting tips to help me maintain my compressed air system?

Here are some great Air Compressor Trouble Shooting Tips
to help you or anyone providing the regular maintenance for your compressed air system.

Below are listed several very common problems, their probable cause and some usual remedies for the trouble.

Of course, there can be multiple problems and unique circumstances to every compressor issue…but these tend to solve the most common situations.

Low pressure at point of use

Probable Cause: Remedial Action
Leaks in distribution piping: Check lines, connections and valves for leaks
Clogged filter elements: Clean or replace filter elements
Fouled dryer heat exchanger: Clean heat exchanger
Low pressure at compressor discharge: See below

Low pressure at compressor discharge

Probable Cause: Remedial Action
For systems with modulating load controls, improper adjustment of air capacity system:
Follow manufacturer’s recommendation for adjustment of air capacity system

Worn or broken valves Improper air pressure switch setting:  Check valves and repair or replace as required
Follow manufacturer’s recommendations for setting air pressure switch

Improper air pressure switch setting: Follow manufacturer’s recommendations for setting air pressure switch

Water in lines

Probable Cause: Remedial Action
Failed condensate traps: Clean, repair, or replace the trap
Failed or undersized compressed air dryer: Repair or replace dryer.  If you do not have an Compressed Air Dryer, consider adding this equipment.

Liquid oil in air lines

Probable Cause:  Remedial Action
Faulty air/oil separation: Check air/oil separation system; change separator element
Compressor oil level too high:  Follow manufacturer’s recommendation for proper oil level

Dirt, rust or scale in air lines

Probable Cause: Remedial Action
In the absence of liquid water, normal aging of the air lines: Install filters at point of use

Excessive service to load/hour ratio

Probable Cause: Remedial Action
System idling too much:
For multiple compressor system: consider sequencing controls to minimize compressor idle time
Adjust idle time according to manufacturer’s recommendations

Improper pressure switch setting: Readjust according to manufacturer’s recommendations

Elevated compressor temperature

Probable Cause: Remedial Action
Restricted air flow: Clean cooler exterior and check inlet filter mats

Restricted water flow

Remedial Action:
Check water flow, pressure, and quality; clean heat exchanger as needed

Low oil level

Remedial Action:
Check compressor oil level, add oil as required

Restricted oil flow

Remedial Action:
Remove restriction, replace parts as required

Excessive ambient temperature

Remedial Action:
Improper ventilation to compressor; check with manufacturer to determine maximum operating temperature.

Owned & Operated by
Tommy McGuire
McGuire Air Compressors, Inc.
“Real People with Real Air Compressor Experience”

For Champion Air Compressors…

For Reelcraft Hose Reels for Air, Water, Oil & fluid
plus Electric Cord Reels & Welding Cable Reels…

For Arrow Refrigerated Air Dryers
to remove moisture from your compressed air system…

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Call us:

Mailing address:
McGuire Air Compressors,Inc.
P.O. Box 1100
Graham NC  27253


Compressed Air Safety Tips

Compressed Air Safety Tips from

  • ­­­Does your air pressure keep dropping while you are using your tools & equipment?
  • Have you added or are planning to add new equipment which uses air?
  • Are your air compressors working hard all the time- but you just aren’t sure how to figure how much more horsepower you need?

When your business counts on air – you need to know the valuable formulas and steps to help accurately determine how many CFM you use. You also need to know how to accurately figure how much additional CFM and horsepower you need when considering a new air compressor?

Here are some specific formulas that can help you determine how many CFM you presently use and how many more CFM you need to meet your desired PSIG. We will show you how to take this information and use it to determine how much air compressor horsepower you actually need.

Find out how many CFM your air compressor delivers

1. STOP the compressor unit

2. CLOSE the outlet valve on the tank/air receiver

3. DRAIN the condensate from air receiver until there is 0 PSIG –
then close the drain valve

4. NOTE THE TIME- in minutes & seconds (Best to write it down.) Then START THE UNIT.
When the compressor unit stops and unloads – then NOTE THE TIME again – in minutes & seconds. Convert the minutes into seconds and then total the number of seconds it takes between START and STOP/UNLOAD.

5. NOTE the GUAGE PSIG reading

6. NOTE the Air Receiver/Tank GALLON SIZE


TANK GALLONS x .538* x PSIG divided by SECONDS


You have an 80 gallon tank, your total start to stop/unload time was
3 minutes and 30 seconds. Change the minutes to seconds timed
(60 x 3= 180 seconds plus 30 seconds which totals 210). You will use the total number of seconds (210) and the noted 175 PSIG within the formula as shown below:

80 multiplied by .536 = 42.88
42.88 multiplied by 175 (Example PSIG) = 7504.00
7504.00 divided by 210 (total seconds)= 35.74 CFM delivered

The example shows that the air compressor is delivering 35.74 cfm

Your Response to this evaluation should be to compare this number with what your air compressor manufacturer says your CFM should be and evaluate how efficiently your compressor is running.
If your air compressor is within 10% of manufacturer’s specifications, then the unit is OK, if not – repair unit and recalculate your needs.

Find out how many more CFM you need to
raise your PSIG

1 What is your desired pressure ______?
(Our Example125 psig)

2. What is your present operating pressure_______?
(Our Example 70 psig)

3. Divide desired pressure by present operating pressure
(125 psig divided by 70 psig = 1.79)

4. This gives us the X-factor needed for this formula (1.79 )

Multiply present air compressor cfm (35.74) by your X-factor (1.79)
(35.74 X 1.79= 63.98 This gives you the total cfm needed –
which is 63.98 for our example)

6. Deduct your present cfm from the needed cfm
(63.98 minus 35.74 present cfm = 28.24)

7. This gives you the additional cfm needed to raise your psig to the level you actually need. (which is 28.24 additional cfm for our example)

Translate your answers into how much horsepower
you actually need to operate

Divide your additional cfm needed by 3.5* (see the chart for your *actual compressor type & horsepower)
(28.24 ÷ 3.5 = 8.07 hp, which would be the additional horsepower needed for our example)

This will give you the additional horsepower you actually need.

(We will need to round up the 8.07 hp to 10 hp needed for our example. You will have to round up to the nearest standard
horsepower also.)

*CFM per compressor horsepower chart:

3.5.cfm per hp for small piston compressors ½-30 hp

4 cfm per hp for large piston 40 hp up & small screw compressors
2 hp-30 hp

4.5 cfm per hp for 40 hp-150 hp medium hp screws

5 cfm per hp for 200 hp-2000 hp large screw & centrifugal compressors
Note: Always buy CFM of delivered air at the PSIG you need…not horsepower.

Note: Always invest in at least 20% more CFM than your equipment needs. This will cover extra air usage for such things as air leaks and wear.

Follow these formulas and you can figure just how much more CFM and air compressor horsepower you really need to get the job done!

Compressor Terms you should know:

Cubic Feet Per Minute (cfm) – Volumetric air flow rate.

“psig” means pounds per square inch, GAGE pressure. Gage pressure is the absolute pressure of something, with the atmospheric pressure subtracted. In practice, when someone gives a pressure in just “psi” they probably mean gage pressure. If they mean absolute, they should be using “psia.”

Gauge Pressure – The pressure determined by most instruments and gauges, usually expressed in psig. Barometric pressure must be considered to obtain true or absolute pressure.

Load Time – Time period from when a compressor loads until it unloads.

Unload – (No load) Compressor operation in which no air is delivered due to the intake being closed or modified not to allow inlet air to be trapped.

Receiver – A vessel or tank used for storage of gas under pressure. In a large compressed air system there may be primary and secondary receivers.

Tommy McGuire

McGuire Air Compressors, Inc.
“Real People with Real Compressor Experience”


Here’s one of the most used formulas you should keep on hand…
How to find how many CFM your air compressor delivers.

Follow these steps to find how many
CFM Your Air Compressor delivers

1. STOP the compressor unit

2. CLOSE the outlet valve on the tank/air receiver

3. DRAIN the condensate from air receiver until there is 0 PSIG -then close the drain valve

4. NOTE THE TIME– minute & second. Then START THE UNIT.
When unit stops/unloads – then NOTE THE TIME again – minute & seconds. Convert minutes into seconds and then total number of seconds it takes between START and STOP/UNLOAD.

5. NOTE the GUAGE PSIG reading

6. NOTE the Air Receiver/Tank GALLON SIZE


TANK GALLONS x .538* x PSIG divided by SECONDS
You have an 80 gallon tank, your total seconds timed were 189 and you noted 175 PSIG.

80 multiplied by .536 = 42.88
42.88 multiplied by 175 (example PSIG) = 7504.00
7504.00 divided by 189 (total seconds)= 39.71 CFM delivered

You now know that your air compressor is delivering 39.71 CFM

Your Response to this evaluation should be to compare this number with what your air compressor manufacturer says your CFM should be and evaluate how efficiently your compressor is running.

Tommy McGuire

McGuire Air Compressors, Inc.
“Real People with Real Compressor Experience”


Leaks can be a big source of wasted energy in an industrial compressed air system, sometimes wasting 20 to 30 percent of a compressor’s output. A typical plant that has not been well maintained will likely have a leak rate equal to 20 percent of total compressed air production capacity. On the other hand, proactive leak detection and repair can reduce leaks to less than 10 percent of compressor output.

In addition to being a source of wasted energy, leaks can also contribute to other operating losses.
Leaks cause a drop in system pressure, which can make air tools function less efficiently, adversely affecting production. In addition, by forcing the equipment to run longer, leaks shorten the life of almost all system equipment (including the compressor package itself).

Increased running time can also lead to additional maintenance requirements and increased unscheduled downtime. Finally, leaks can lead to adding unnecessary compressor capacity.

Q. Where do most leaks usually occur?

While leakage can come from any part of the system, the most common problem areas are:

• Couplings, hoses, tubes, and fittings

• Pressure regulators

• Open condensate traps and shut-off valves

• Pipe joints, disconnects, and thread sealants.

Q. How much can compressor leaks cost my business?

A small leak – no larger than 1/16″ can cost an extra $523 a year*.
Add a few other small leaks here and there until you have leaks equal to a 1/4″ opening…and now that “small leak” can cost you $8,382 a year.*  It is easy to see that what seems like a small leak comes with a very high price tag over time.

*Costs calculated using electricity rate of $0.05 per kilowatt-hour, assuming constant operation and an efficient compressor.

Q. How do you estimate the SIZE of AIR LEAKS?
It’s not very hard.  We’ll use the “TIME METHOD” to estimate percentage % of loss due to air leaks in your plant. 

1-    Turn OFF all air operated end-user equipment.
2-    Start your air compressor and let it cycle 3 times
3-    Time the OFF-LINE / UNLOAD TIME (not pumping time) using your watch. (Example: 5 minutes)|
4-   Time the ON-LINE / LOAD TIME (pumping time) using your watch. (Example: 2 minutes)
5-   Calculate total percentage of air leaks as follows:

Add the OFF / UNLOAD and the ON / LOAD times together:

Example: T(5 minutes)  +  T (2 minutes)= 7 minutes
Divide  ON / LOAD time T (2 minutes) by the total minutes: 2 ÷ 7 = 0.29

The result tells you 29% of your air compressor’s CFM’s are maintaining your AIR LEAKS.
This would mean that you are losing almost ONE THIRD of your compressed air to air leaks. 

Q. What’s the best way to detect and fix compressor leaks?

Since air leaks are almost impossible to see, other methods must be used to locate them.

The best way to detect leaks is to use an ultrasonic acoustic detector, which can recognize the high-frequency hissing sounds associated with air leaks. These portable units consist of directional microphones, amplifiers, and audio filters, and usually have either visual indicators or earphones to detect leaks.

A simpler method is to apply soapy water with a paint brush to suspect areas. Although reliable, this method can be time consuming.

Click here to see how to estimate the SIZE of AIR LEAKS.

Q. How To Fix Leaks

Leaks occur most often at joints and connections. 

Stopping leaks can be as simple as tightening a connection or as complex as replacing faulty equipment, such as couplings, fittings, pipe sections, hoses, joints, drains, and traps. In many cases, leaks are caused by failing to clean the threads or by bad or improperly applied thread sealant. Select high quality fittings, disconnects, hose, tubing, and install them properly with appropriate thread sealant.

Non-operating equipment can be an additional source of leaks. Equipment no longer in use should be isolated with a valve in the distribution system.

Another way to reduce leaks is to lower the air pressure of the system. The lower the pressure differential across an orifice or leak, the lower the rate of flow, so reduced system pressure will result in reduced leakage rates. Stabilizing the system header pressure at its lowest practical range will minimize the leakage rate for the system. Once leaks have been repaired, the compressor control system must be re-evaluated to realize the total savings potential.

Establishing a Leak Prevention Program

There are two basic types of leak repair programs:

1. The leak tag program
2. The seek and repair program.

The” seek and repair” method is the simplest. As it states, you simply find the leak and repair it immediately.

With the leak tag program, the leak is identified with a tag and logged for repair at a later time. This is often a two-part tag; one part stays on the leak and the other part is turned into the maintenance department, identifying the location, size, and description of the leak to be repaired. The best approach depends on the type, size, and the culture/work practices of the facility. It is more likely that the best solution will be a combination of the two.

*SOURCE:  Based on definitions taken from “Improving Compressed Air System Performance” published as a cooperative effort of the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) Best Practices and the Compressed Air Challenge®.


Tommy McGuire
Owner of McGuire Air Compressors
“Real People with Real Air Compressor Experience”

Offering you Quality Industrial Equipment at a Savings…





Ask a Question:
What causes pressure drop in my compressed air system?

Any type of obstruction, restriction, or roughness in the system will cause resistance to air flow and cause pressure drop.



In the distribution system

, the highest pressure drops usually are found at the points-of-use, including undersized or leaking hoses, tubes, disconnects, filters, regulators and lubricators (FRLs).


On the supply side of the system

, air/lubricant separators, aftercoolers, moisture separators, dryers and filters can be the main items causing significant pressure drops. The maximum pressure drop from the supply side to the points-of-use will occur when the compressed air flow rate and temperature are highest.
Your Compressed Air System components should be selected based upon these conditions and the manufacturer of each component should be requested to supply pressure drop information under these conditions.

When selecting filters, remember that they will get dirty.
Dirt loading characteristics are also important selection criteria. Large end users who purchase substantial quantities of components should work with their suppliers to ensure that products meet the desired specifications for differential pressure and other characteristics.



The distribution piping system

often is diagnosed as having excess pressure drop because a point-of-use pressure regulator cannot sustain the required downstream pressure. If such a regulator is set at 85 psig and the regulator and/or the upstream filter has a pressure drop of 20 psi, the system upstream of the filter and regulator would have to maintain at least 105 psig. The 20 psi pressure drop may be blamed on the system piping rather than on the components at fault. The correct diagnosis requires pressure measurements at different points in the system to identify the component(s) causing the excess pressure drop. In this case, the filter element should be replaced or the filter regulator size needs to be increased, not the piping.


How to Minimize Pressure Drop

Minimizing pressure drop requires a “systems approach” in design and maintenance of the system.   
Air treatment components, such as aftercoolers, moisture separators, dryers, and filters, should be selected with the lowest possible pressure drop at specified maximum operating conditions.
When installed, the recommended maintenance procedures should be followed and documented.

Additional ways to minimize pressure drop are as follows:


• Properly design the distribution system.


• Operate and maintain air filtering and drying equipment to reduce the effects of moisture, such as pipe corrosion.


• Select aftercoolers, separators, dryers and filters having the lowest possible pressure drop for the rated conditions.


• Reduce the distance the air travels through the distribution system.


• Specify pressure regulators, lubricators, hoses, and connections having the best performance characteristics at the lowest pressure differential. These components must be sized based upon the actual rate of flow and not the average rate of flow.