Happy New Year! In a recent article we discussed the basics of how air brake systems work. I would like to pick up where we left off by discussing some of the problems you may encounter with your air brake system.
Compressors The compressor is the part that builds up air pressure, which is then delivered throughout the system to supply tanks that are used for service brakes, emergency brakes and trailer brakes. Because the compressor is lubricated and cooled by the engine, there is the possibility of oil and coolant leaking into the air system.
How do I find an air leak ?
This can cause damage to the compressor and the rest of the system. Another cause could be that the oil return line to the engine is blocked. Make sure this line is free of kinks or sharp bends.
The drive gear or pulley could be loose and need tightening. The drive gear could also be worn and need to be replaced. Another important point to remember is that air compressors need to have clean air going into them. In some systems, the compressor has its own air cleaner. Air dryers Once the air leaves the compressor, it goes through the air dryer, where all the impurities in the air are removed.
However, the air dryer falls subject to many factors that can cause it to malfunction.
If working properly, the dryer should cycle on and off to exhaust impurities out of the system. If the dryer is constantly cycling, inspect the system for air leaks. If you notice the dryer is not purging or exhausting air, check the line to the compressor to make sure it is in good shape and not plugged.
A faulty purge valve can also cause the dryer to fail. Make sure to service air dryers periodically to avoid having dirty air circulate through the system and end up in the supply tanks. In the winter, any moisture trapped in the system can cause freeze-ups. In the summertime, gunk and debris can clog up the system.
Some air dryers have desiccant cartridges that absorb moisture. These cartridges can become too contaminated to function properly and must then be replaced. Reservoir supply tanks The supply tanks throughout the air system must be monitored closely.
Air must be available in the supply tanks in order for the brakes to be applied, which occurs with the help of relay valves. Why do we need that reservoir air waiting in the supply tanks? You do not want to wait for air pressure to build up and reach the supply tanks, especially if you need the brakes to work quickly. Therefore, supply tanks should always work as efficiently as possible. Water accumulation can occur from time to time in reservoir tanks. As the air is compressed, it heats up, causing any moisture to evaporate, pass through the compressor and air dryer and then condense in the supply tanks.
Make sure to drain the supply tank if there is an accumulation of water. If coolant is present inside the reservoir tank, check the compressor cooling system to identify and repair the problem. These valves are very sensitive to oil, moisture, dirt, rust and debris. Always repair or replace any valves that are faulty.Forums New posts Search forums. Media New media New comments Search media. Members Registered members Current visitors New profile posts Search profile posts.
I will gradually change all to brass. I know cab air bags are on Secondary air and I know at least 2 of quick connects where on Primary air Now in hours parked the Primary air will drop from down to - I think that is ok. Use to drop down to before repaired leaks. Secondary air when parked will drop from that's all the higher it will build up based on gauge down to Use to drop to 0 prior to repairs. Now everything has been spray soaped and only minor leak still see is Fan Hub - very small bubbles which could account for Secondary air loss in hours from down to 50 I guess??
Am I right? I will replace the fan hub soon but mechanic small shop not dealership told me to just run it for now because the leak their is so minimal according to him. Also I hear pretty good and don't hear any other leaks when truck is parked.
When driving the truck Primary air stays right at doesn't move unless braking then builds right back up and stays right on money. It has been doing this since I bought truck and the repaired leaks haven't changed anything. The previous truck owner told me they replaced the front?? Most importantly - what do you guys think is the problem why my Secondary air keeps doing this two minute bleed down and build up when driving?????
Thanks in advance for any help!! I believe your leak is so severe your truck should be out of service. But you can check your cdl handbook I think no more than 10 psi in 1 minute is allowed. Having said that, the way to solve the problem is as you have, spray the whole system with soapy water and check again.
Spray down everywhere not just connectionns, wet the hose and the tanks, wet down the connections in your air seat as well as the hoses. Also, check the spring brake housing, they contain rubber bladders which fill with air to release the springs. If you don't leak when parked, but do leak when the parking brake is released the leak is most likely in the spring brake housing or hoses which feed it.Forums New posts Search forums.
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Seems to go down to around 50 psi. Sometimes the primary tank loses pressure as well, but not everytime. I wonder what the best way to discover the source of the air leak? Any tips or suggestions for this mechanically inept driver would be appreciated. Also : During normal operation, the air pressure is as it should be.
I cannot hear any obvious leaks. Last edited: Aug 29, The Enemy Veteran Expediter.
Look for bubbles after you spray and you might find your air leak. The Enemy said:. Deville Not a Member. Pin hole air leaks are like trying to find needles in a hay stack. The Enemy's way is most likely the best way.
Deville said:. Mdbtyhtr Expert Expediter. I used freon at the air compressor out port and quickly tightened it back up and used my freon leak detector to find the leaks. I even found a screw into the air line leading to the roof mounted air horns that was behind interior trim, it was one you could never hear. The soapy water in a spray bottle works for the more obvious leaks. Spray all connections, exhaust ports on brake valves and any where air lines are retained by clamps.
Last edited: Aug 30, Mdbtyhtr said:.The Governor controls compressor output by cycling and keeping air in a predetermined range. It monitors the supply tank and sends a signal to Air Compressor.
Cut in pressure is 85 and cutout is The Governor is mounted on the compressor or may be mounted remotely. The Compressor unloaded mechanism controls the loading and unloading of air during the compressor cycle.
During loading or pumping the piston moves downward creating a vacuum on top of the piston. Next, the piston moves upward compressing the air in the cylinder. This closes the inlet valve and opens the compressor inlet valve building pressure in the system. When the system cut out pressure is reached - the unloaded port is pressurized by the governor signal. This moves the Sliding leaf valve and uncovers the inlet cap.
During the pistons upstroke, the air returns to the inlet port and no compression occurs once the pressure in the system is depleted to cut in level. The Governors signal to the Compressor is exhausted. The Sliding leaf valve returns to the loaded position and compression resumes.
STOPPING WITH AIR BRAKES
The type of air dryer depends on application and the type of compressor being used. Compressed air enters air dryer thru inlet port and passes thru drying material called desiccant. Desiccant captures moisture as well as oil and other contaminants. When the system cutout pressure is reached, a signal from the Governor opens the Air Dryer purge valve to expel moisture and contaminates.
This same signal also unloads the compressor after the purge cycle. The supply tank is first tank in system and moisture tends to collect in it more than others. Supply tank has pressure relief valve if system becomes over pressurized.
The Relief valve vents excess air to prevent and damage to system. The Supply tank includes a low pressure indicator which monitors over all system pressure. If pressure falls below 60 PSI — an alarm will sound and light will come on to notify the driver of a low pressure condition. Air from the supply tank flows to the primary and secondary tanks. These tanks are protected by check valves to prevent the total loss of air in the event of a failure between the service tank and compressor.This is page two of an article about I need more air!
Page one about I Need More Air is here. Page one begins our discussion about the benefits of adding another air tank.
If an air tool draws more air than the air compressor can deliver even when running full out the supply and pressure of compressed air to the air tool will decrease to the point where the air tool will not do the job it was designed to do.
When you add another air tank, when you are not using compressed air, your air compressor will run and fill both tanks — the one that came with the compressor and the one you have just added. This means that the air compressor motor will run longer before reaching cut out pressure and stopping. The compressor pump is now filling a larger volume. Note that you must make sure that your air compressor will handle the increased run time. The manuals for the lower cost DIY air compressors may not even show you what your compressor duty cycle is.
If your air compressor manual does not indicate the duty cycle of your brand and model, then our rule of thumb is that your air compressor should only run for a maximum of ten consecutive minutes. If it needs to run longer to fill the tanks, the we shut it down and let it cool for fifteen minutes before running the compressor again. After the compressor motor has cooled down, we will run the compressor again for the maximum ten minutes or until both tanks are full to the cut out pressure setting and the compressor stops automatically, whichever comes first.
Just watch out for compressor overheating. Plumbing would need to be modified so that air from the compressor pump would flow both into the main tank on the compressor and this new tank at the same time.
Plumbed this way the one pressure switch on the air compressor would monitor the pressure in both tanks and shut the air compressor off when the pressure reached in both tanks reached the normal cut out setting of the original compressor and tank.
To add a tank to your DIY type air compressor, the simplest way is to add a tee to the tank. See the sketch below. Another benefit of having a secondary tank is that the secondary tank can be placed nearer the job site more easily. More convenient to move around and more air supply closer to the nail gun are significant benefits. If you add another air tank to your air compressor, you will be able to use higher demand air tools for a longer period of time.
If, however, the air supply and pressure diminishes still, and your air tool starts to wind down, then stop, take a break, and let the air tanks come back up to cut out pressure. Wanting to know if installing a 50L Receiver is large enough for a Compressor that operates but with power surges will stop that compressor however want to continue the pressure flow with the Receiver?
Question is how long to hold above 1bar when releasing pressure at 2 ltrs per min? Do we need a bigger Receiver than a 50Ltr? Sure you can. Thanks for a very informative and useful set of articles. The information assisted in updating a couple of small portable hobby and light work compressors.Discussion in ' Trucks [ Eighteen Wheelers ] ' started by ptwn1Jul 31, Log in or Sign up. Find Trucking Jobs. Jul 31, 1.
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Jul 31, 2. Pablo-UAJul 31, Jul 31, 3. Jul 31, 4. The first thing I would be checking is for air leaks. It is easier to find with shop air, connected to the system, chock the tires and release the brakes wet you hand and see if there is air from the relay between the axles, if there is a leak you need to remove the service brake lines from the brake pots and look for the leaker. Use a soapy solution, on every connection and tank.
A multiple of little leaks can add up to a large leak. Just a thought! JohnP3Jul 31, RocketScott Thanks this.
Jul 31, 5. KansasJul 31, Aug 1, 6. Fill it with water and add soap. Pump it up and you can spray for a long time. I also use one for brightener but you can leave in there very long as it will eat the seal.
Aug 2, 7. Many times you will find a lot of leaks when you are washing the truck, all you have to do is look. JohnP3Aug 2, Show Ignored Content. Draft saved Draft deleted.
Your username or email address: Do you already have an account? No, create an account now. Yes, my password is: Forgot your password?Learn more…. What is a compressed air receiver tank —and how do you know if you need one?
Our guide to compressed air receiver tanks explains how they work, what they do, and how you can use them to maximize the efficiency of your compressed air system. An air receiver tank sometimes called an air compressor tank or compressed air storage tank is exactly what it sounds like: a tank that receives and stores compressed air after it exits the air compressor. This gives you a reserve of compressed air that you can draw on without running your air compressor. An air receiver is a type of pressure vessel ; it holds compressed air under pressure for future use.
The tanks come in a range of sizes and in both vertical and horizontal configurations. An air receiver tank provides temporary storage for compressed air. It also helps your air compression system run more efficiently. The air receiver tank has three main functions in your compressed air system:.
The primary role of an air receiver tank is to provide temporary storage for compressed air. Storing compressed air allows the system to average the peaks in compressed air demand over the course of a shift.
You can think of your air receiver tank like a battery for your compressed air system, except it is storing air instead of chemical energy. This air can be used to power short, high-demand events up to 30 seconds such as a quick burst of a sandblaster, dust collector pulse, or someone using a blowgun to dust themselves off.
The air in the tank is available even when the compressor is not running. Storing compressed air reduces sudden demands on your air compressor, prolonging the life of your system.
Using an air receiver tank may also allow you to use a smaller horsepower compressor for larger jobs. The air receiver tank provides a steady stream of air to compressor controls, eliminating short-cycling and over-pressurization. Uneven compressed air utilization causes uneven demand on the air compressor, resulting in rapid cycling of the compressor controls as the compressor turns on and off to meet moment-by-moment demand.
Over time, frequent short cycling will lead to premature failure of switches and other compressor components. Rapid cycling can result in excessive wear of the motor contactor or even a direct motor short because of winding insulation. The air receiver tank eliminates short cycling and provides more consistent system pressure to controls. As air is compressed under pressure, its temperature increases; this is a simple law of physics known as the Pressure-Temperature Law.
This is too hot for most air-operated equipment to use directly.
Air Receiver Tanks: Full Guidelines 2020
Hotter air also contains more moisture, which will result in excess water vapor that will condense in control lines and tools if it is not removed. The condensed air must be cooled and dried before it is utilized. A heat exchanger is used to remove excess heat caused by compression. The air receiver tank acts as a secondary heat exchanger; as air sits in the tank or slowly flows through it, it naturally cools over time. Adding an air receiver tank significantly improves the efficiency of your compressed air system.
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