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Vacuum Tips: Beware Of The Pinched Vacuum Hose

Posted by Tim Collins on Aug 19, 2015 2:00:00 PM

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Industrial Process Troubleshooting: What Is Wrong With My Vacuum Gauge?

Many discussions surrounding vacuum pressure and loss of suction focus on the pump’s deficiencies and leaky chambers, but there is usually little thought or concern regarding another integral part the system’s functionality: the vacuum hose that delivers the suction. Are you sure the hose you are using is vacuum rated? Or, will it collapse under pressure?

 

Under Pressure

It's important to know the minimum pressure or maximum vacuum your vacuum system is pulling so you can purchase the appropriately rated industrial vacuum hose. If your hose can't handle the vacuum pressure then it can collapse or pinch, resulting in a loss of suction which may appear as a stalled evacuation. 

Pinched_Vacuum_Hose.1 

On-Site Client Troubleshooting Example:

We received a customer call stating that our vacuum gauge wasn't working. Each of our digital vacuum gauges are tested and calibrated under actual vacuum before it leaves our shop, so it is important for us to understand how a device performs in the field. We are quick to act when we hear that one of our devices are not working in the field. For this particular application, our customer was evacuating underground high power gas-insulation transmission line equipment. 

2 Things We Learned:

  1. Importance of using vacuum rated hose--one that can take the pressure of your vacuum system
  2. Importance of plumbing vacuum sensor close to the vacuum source--avoid placing the sensor too far away or the vacuum reading could be effected

Findings: the customer used hose that wasn't vacuum rated and it got sucked in, pinching off the actual chamber vacuum pressure, which hid the changing pressure from the vacuum sensor creating a false reading. The vacuum pump would start and the gauge reading would go down.  At some point the hose would pinch off, and the gauge would stop decreasing in value, even though it was obvious from the sound of the pump that the chamber was still being evacuated to a lower pressure. The customer was troubleshooting the system with his trusty McLeod gauge, but it was plumbed at a different place in the system and was not affected by the stalled vacuum caused by the pinched hose. Since the vacuum gauge readings didn't agree, the customer concluded that the digital vacuum gauge didn't work.

It is important to keep in mind that where the gauge is placed for readings is of vital importance, as it should be as close to the measurable area as possible. In our above example the technician performing this task plumbed the gauge to a point that prevented the vacuum gauge from doing its job of measuring vessel pressure leading to a false negative reading.  

If your evacuation appears to be stalled, verify that a collapsed hose didn't inadvertently create a closed valve between your vacuum gauge and the rest of the system.

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Topics: Manufacturing, Accuracy, Vacuum Pump Troubleshooting