Part II Pneumatic Conveying Troubleshooting Series:
Is your system performance not what you’re used to? Have your pounds per hour dropped or your power consumption increased, but you don’t know why? Air leakage in your convey line may be the problem.
Whether your system is vacuum or pressure driven, leaks are very problematic. Line leaks can be detrimental to successful conveying because it reduces the air pressure in the conveying line below optimum levels. As line leaks get worse, or more leaks develop, the drop in pressure can be significant which increases the power required to maintain the desired pressure/vacuum until production results can’t be met. Decreases in the velocity and increases in the material-to-air ratio in the system may result in product stalling/plugging or higher convey pressures. Leaks in a pressure system will allow contaminants (i.e., dust, oils, product, etc.) to escape into process areas where they can cause issues. Leaks in a vacuum system allow air that may be contaminated to be pulled into the piping and the product stream.
In Part II of our Pneumatic Conveying Troubleshooting Series, we will explain air leakage issues and how to check for line leaks.
One of the most common mistakes you can make when checking for a line leak is not creating pressure in the line. If there isn’t a difference in pressure, then it won’t leak. So you must first create pressure in the line. It’s like checking your hose for a leak when it’s not turned on. If water isn’t running through it, then you can’t tell where the hose is leaking. The same goes for your convey line, if you aren’t running air pressure in the line, then you won’t be able to tell where it is leaking.
Any leak that you can feel or hear is bad. In fact, there is no such thing as a “small” leak. It’s best to identify the leak right away to prevent any further issues. You should perform regular leak inspections or inspect as problems arise. In general, leaks closest to the blower are the most detrimental. So what do you do if you can’t feel or hear the leak?
If you suspect you have a leak, it makes sense to start with the source. When a line isn’t operating as expected, make sure all connections from the blower to the destination are fully inspected. It is important to be aware of all possible areas that could be leaking, so check the following parts and components:
- Morris couplings
- Tri-clover clamps
- Airlock flanges
- Pressure or vacuum gauge ports
- Blower silencers
- Blower flanges
- Butterfly valves (bypass in blower)
- In-line diverters
Besides checking parts and components, here are some of the most common possibilities for leaks in pressure and vacuum systems:
Pressure System:
- Air leaks at pipe joints
- Couplings not properly installed (tightened) or gasket worn
- Holes in conveying and/or air line
Vacuum System:
- Airlock at discharge of system is worn allowing excessive air leakage into the system at the receiver which results in “starving” the pickup point
- Air leaks at pipe joints
- Couplings not properly installed (tightened) or gasket worn
- Holes in conveying and/or air line
There are two options we suggest when it comes to leak inspection. One way is to spray any area that could be leaking with a mixture of water and dish soap. This method is for pressure systems only, because the soap solution would be drawn into a vacuum system, thus contaminating the lines. Again, it is important that, at the very least, the blower is running at this time. It is even better if some back-pressure is applied to the system, so that the couplings and seals are under some positive pressure. Once a leak has been found, repair the leak until no more bubbles are produced in this area.
The second option is checking for leaks with an ultrasonic leak detector. This method works for both pressure and vacuum systems. This device is easy to use and finds leaks quickly. A high ultrasonic frequency is generated when an air leak occurs; thus, the larger the leak, the greater the ultrasound level. All leaks make noise, but hearing them with the human ear may not be possible, so scanning the production line from start to finish with the detector is a must. Since vacuum systems leak inward, an ultrasonic detector is the best option for finding leaks.
For more information on line leaks and how to find them, watch our second video in our Maintenance Series “Checking for Line Leaks”.
At Horizon Systems, we are committed to safety and stand behind our service. Our Field Service Technicians are experienced and knowledgeable as well as OSHA trained. If you’d like to talk with a technician or schedule an on-site audit or evaluation, please contact Jeff Koch, Field Service Manager, at (785) 856-8159 or jkoch@horizonsystemsinc.com.