Frequently Asked Questions – and Our Answers


What is the reason for a "washboarding effect" in the cylinder bore and what can I do to stop that?

From our experience a “washbording effect” (or corrugation) or wear in the bore is the main reason for a high noise level. For that reason you may find the following:

  • Lubricants are contaminated with particles from of the application. Recommendation: Filter the oil and investigate where these particles are from. It is recommended to replace filters and change the oil.
  • Insufficient lubrication due to too low differential pressure between inlet and exhaust side of the pump. The pump must be in operation within the recommended vacuum range. Details are explained in the operating instructions.  Recommendation: Contact our sales department concerning your special application.
  • Rotor blades are seized in the rotor slots and come out of the slots retarded. As a possible reason it could be detected as a contamination of the oil. Recommendation: Change oil and possibly replace the blades. The cylinder might be  re-bored and re-honed.

What is the percentage of oil in the exhaust air?

Elmo Rietschle is a manufacturer of oil lubricated pumps covering a lot of different applications and available with different lubrication systems. Mechanically it is not possible to separate 100% oil from the exhaust. If pumps are operating according to instructions for our products, we will expect to find 8 until 12 ppm (parts per million) or 10 until 15 mg/ Nm³ (Norm cubic meter) in the exhaust  air. If you want to avoid oil completely, we can offer a wide range of dry running pumps. Our sales staff will give support to any request from your side.

WPB/WVB: Oil-leakage at the gear shaft. Why?

All of our blowers from this range are equipped with a dynamic shaft seal,  i.e. there is no wear after longer operation and thus no leakage as should be expected with a normal shaft seal.  As this seal effects tightness only in operation, oil level may not exceed maximum. If in any case oil leakage can be found, drain a certain quantity of this oil to achieve a level between maximum and minimum.

WPB/WVB: What is maximum operating temperature?

The permissible operating temperature at the bearings of  SHARK - Blowers is 140 degrees Celcius. The max. temperature load for the oil in the gearbox is 180 degrees Celcius. A temperature safety-device can be adjusted at 95 degrees Celcius.

VC...: Having replaced the oil- separators, smoke was detected at the exhaust of the pump. What is the reason and how can I stop that?

During operation within the recommended vacuum range smoke should not occur at the exhaust port. If it happens, we assume that oil contaminated air by-passes the oil-separator filter. Presumably the o-ring is not in the correct position(slipped) or is damaged. This can happen by reassembling of the oil-separators. Please note also to use a torque wrench for fixing these elements.
The size of the torque depends on the size of the oil-separator.

  • Oil-separator 730937-0000 and 730936-0000 (WS = 10) demands a torque of 17 Nm (Newtonmeter) and 
  • Oil-separator 730946-0000 (WS =8) a torque of 12 Nm.

The newly designed oil-separators no longer require the plastic screw, but are equipped with thread. O-rings are also no longer necessary. The otimized version needs only one o-ring and this will be delivered preassembled together with the new separator. These elements are packed each of separately and equipped with assembly notes. The torque is fixed with 15 Nm and is the same for each size.
Comparision of id.no.:

  • 730936 replaced by  731400
  • 730937 replaced by  731401
  • 730946 replaced by  731399

SMV 500: After a repair the sealing ring position 115 (E561/2 1.7.98) came out and touched the impellor. How can I prevent that?

During disassembly the seat of the ring has possibly been changed. You can glue the sealing ring with Loctite 638 (Id.-No. 720117-0000) or calk the seat with a drift.

VC...: Pump is getting hotter after several months of operation and the amperage of the motor increases. What is the reason and how can I solve the problem?

Due to application, impurities can be sucked into the pump and oil can be contaminated  and / or due to high ambient temperature the oil can age. Both can lead to clogged oil separators and increase the backpressure. Hence it follows that the temperature of the oil increases and the same happens with the amperage of the motor. To solve the problem you should change oil and oil separators. Preventive measure could also be to install a gauge (Id.-No. 730673-000) for checking the backpressure.

KTA...: After several years of operation you hear a metal sounding noise during start and stop. How can I prevent that?

Between the pump and motor there are flexible elements (coupling rubbers) for absorbing shocks. They can have a natural wear, resulting in metal parts toucing each other. Replace coupling rubbers or both couplings, depending on their condition.

SAP..: After a longer operating period my blower has a reduced performance. What is the reason for?

The inlet silencer of our blower is equipped with a mesh. This mesh can be clogged from impurities and reduces the performance.This can prolong your operating cycles. Clean or replace the silencers.

VC..: After a longer operating period my blower has a reduced performance. What is the reason for?

In the opposite to other products - oil lubricated – in a vacuum pump the air passes the pump through the oil tank and through separators back into the ambient. Depending on vacuum level – including max. vacuum – air will be passed through the pump in different quantity, although a certain quantity by the gasballast device. This quantity in air mixes with oil and let create oil foam. This is not an advantage unless oil level does not fall under minimum. Please check oil level after pump has been switched off and foam has gone.

VSI..: After one week operation oil in gearbox changes colour into dark. What is the reason for and what should I do ?

The oil used in the gearbox is made of PAO basics and is clear shining like water. After couple of hours operation it changes colour into brown depending on temperature and contact to air. This is quite normal and has no influence to the lubrication, You keep oil in the pump acc. Interval being given in the operating manual.


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