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Vacum Gear Pump Contamination

Vacum Gear Pump Contamination

Vacum Gear Pump Contamination

Hello all,
we have 2 vacuum HORIZONTAL GEAR PUMP in poly ethylene plant that run in low speed. they are sealed with pickings and oil rings. In order to prevent the contamination of product by Oxygen The engineering company decided to build a steel enclosure around the pump with Nitrogen injection points so NO leak in or out. However, the 2 pumps produce off-spec product due to the contamination of product. we have 36 injection points, the manufacturer is Maag. ( http://www.maag.com/cache-buster-1491991140/brochu... ) , we aew using same model.

-What could be the cause of contamination and what is the best approach to find out the leaking points , any recommended action ?


RE: Vacum Gear Pump Contamination

Hello Fahadshehri,

Are all of the flanges inside this metal box? How about the suction and discharge piping leading up to the pump, is it flanged or all butt-welded? Just trying to understand what declared the pump as the contamination point.


"If it rotates, it vibrates."

RE: Vacum Gear Pump Contamination

Your "steel box" is likely not itself completely sealed, given that it encloses the motors of the pumps too, and the wires feeding those motors... It's possible that the enclsoure is not adequately pressurized with nitrogen of adequate quality, or is not being swept with a sufficient amount of nitrogen after it is closed to sweep out all the oxygen that it is initially filled with. Analyse your nitrogen for oxygen content as a first step to see if that's the problem.

A pump like these likely requires true double mechanical seals with proper seal plans, not just "packings and oil rings". The enclosures are a bandage on a more serious wound.

RE: Vacum Gear Pump Contamination

Hello Guac,
The flanges are all inside the enclosure. The pipings lead to suction and discharge are flanged.
Thanks for the help

RE: Vacum Gear Pump Contamination

Hello molten metal,
Thanks for your feedback.
The enclosure is only surrounding the pump starting at the the shaft seal.

RE: Vacum Gear Pump Contamination


Do you have any ultrasound capabilities? You could pinpoint where the leak is using ultrasound. Such as the SDT ultrasound unit.

If not, I like what Molten said about the nitrogen not being of adequate pressure or quality. Like he said, that is a good place to start and if the steel box enclosure isn't sealed properly and your nitrogen pressure isn't high enough, then you have access for ambient air to be sucked into the steel box and into the vacuum pump.

Check your nitrogen quality and if it is sufficient, raise your nitrogen pressure and see if the issue stops. Be aware that if the steel box isn't sealed properly, you have the potential of having a nitrogen enriched atmosphere in that area where personnel could be walking by. Remember safety!


"If it rotates, it vibrates."

RE: Vacum Gear Pump Contamination

Thanks for the feedback, I will let you know guys what the updated later.
Thanks again

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