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FAQ
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Frequently Asked Questions

1.1  What is the water vapors handling capability of a pump? Top 
Water vapor handling capability is an indication of the ability of a vacuum pump to cope with water vapor that has been drawn into the pump sump oil. If it is not sufficient, the oil and the water will build up to an emulsion, which can damage the pump. A gas ballast valve increases the vapor acceptance.
1.2  What is purging a pump? Top 

Purge purpose: at deep vacuum, there is no sufficient airflow to carry over the water vapor that can be located in the pump. The two main reasons why this water can be found in the pump are: 1) because the process air is very damp and/or 2) the compressing action of the lobes or vanes in the pump. If the pump is stopped at the end of its cycle and not purged, this water (in vapor or liquid form) remains in the pump (in addition to the water which can condense in the piping and drop down into the pump), which can cause the internals of the pump to rust. It is therefore important to evacuate this excess water before the pump is completely shut down. To produce an efficient purge, a flow of air dryer then the processed air is required.

Purge is possible when the pump does not operate at full vacuum (ie 0 cfm). Isolating the pump from the process, and opening a vent valve to atmosphere will do this.

Please note the following: in the case of dry pumps (Seco, Mink and MM pumps) there is no problem with running them constantly in that vacuum range (close to atmospheric pressure). But in the case of an R5, running the pump constantly to a vacuum level that is not deep will create too much flow in the pump and the oil might be entrained in the flow of air, out of the pump.

1.3  What is important to consider when a pump is placed outside a building? Top 
Depending on the outside temperatures, type of pump etc, it might be necessary to choose another oil-type. Wet paper-filters can freeze and totally block the pump. Water cooled pumps can also freeze if no precautions are taken. Again, depending on the end location of the pump (inside/outside, very hot or cold environment, etc.), various components of the pump (such as oil and motor) can be selected accordingly. Ideally, vacuum pumps should be placed indoors, in an environment where the ambient temperature should range between 10 deg C to 35 deg C.
1.4  How much clearance distance do I need around the pump? Top 
We recommend at least 3 feet all around the pump. If this cannot be achieved, two main constraints must be respected. 1) At least 1.5 feet on the fan motor side to permit it to have sufficient cool ambient air to maintain a reasonable temperature; 2) for R5 pumps, on the exhaust end, at lest 1.5 times the length of the exhaust filter rack to allow easy servicing on the pump.
1.5  Tips on piping. Top 

Things to avoid are 90 deg tight bends and thinner pipes attached to larger pumps along with diaphragm valves, which tend to suck themselves shut when worn. Never attach a pipe that is smaller than the inlet size of a pump is a good rule of thumb for reducing backpressure. Backpressure is the most common problem encountered. Once you get below 500 mbar, the size of pipe becomes very important. Too large a pipe may cause longer pump down times as well. Bends and elbows build a flow resistance, which can, dependent on the type, equal a straight pipe of several meters of length.

'Soft' bends (D>3d) are better than 'sharp' 90°elbows. Less restriction is created.

If the pump is placed inside a building where rigid piping is used, it is recommended to use a flexible bellow connector to connect the inlet of the pump. This will prevent any vibration to be transmitted from and to the centralized piping. (Also recommended at the exhaust if applicable). Such flexible bellows are available as additional accessories through Busch Vacuum Technics Inc.

If the exhaust of the pump is to be piped, we recommend you place a T shaped piping at the exhaust of the pump. This will prevent any condensation from the piping to flow back in the pump. At the same time, place a ball valve to empty out the accumulation in the T-shape pipe.

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