How to Fit a Busch Vacuum Pump Inlet Filter Cartridge: Size, Seal and First Start

To fit a Busch vacuum pump inlet filter cartridge, stop the pump, lock it against restarting, let it cool and vent the connected lines to atmosphere. Then open the filter housing, lift the old cartridge straight out without tipping it, wipe the housing with the outlet covered, check the new cartridge against the old one for outer diameter, bore and height, and seat it square on its end caps before closing the cover. On first start the pump should pull its usual vacuum again. If it does not, the cartridge is the wrong size, is not sealing, or the problem was never the filter.

Most early failures of a new inlet cartridge come from two things: a cartridge a few millimetres off in height or diameter, so it never seals, and dust from the old cartridge dropped down the outlet during the change.

What the inlet cartridge does on a Busch pump

Busch describes the inlet filter on its R 5 rotary vane pumps as protection for the machine against dust and other solids in the process gas, and offers it with a paper or polyester cartridge. Its R 5 instruction manual for the RA 0165 to RA 0305 D pumps says that if the gas contains dust or other solid particles, a filter of 5 micron or less belongs upstream of the pump. The older manual for the R 5 0025 to 0100 F pumps gives 10 micron or less.

The cartridges we sell for Busch pumps that carry media data are paper cellulose rated at 5 µm with a media weight of 130 g/m2. That includes the Busch 0532000033 cartridge, which is sold as a 2 pack (see current price) and cross-references to Becker 909571, Elmo Rietschle 730123 and 765001, and Oxfil AF.2093.

Everything the cartridge stops is something that would otherwise end up in the oil and between the vanes and the cylinder. Busch's own troubleshooting table lists a defective inlet filter as a cause of black oil. A cartridge that does not seal is, for the pump, the same as a defective one.

Before you open the housing

Busch's maintenance chapter starts the same way for every job: let the machine cool, shut it down and lock it against an unintended start, and vent the connected lines to atmospheric pressure. On a pump that has been pulling vacuum, the housing is below atmospheric pressure until the lines are vented, and the cover will either fight you or let a rush of air through the cartridge the moment it lifts.

If the pump handles anything hazardous, Busch calls for the protective equipment that process needs.

Removing the old cartridge

In a cartridge inlet filter housing, the process gas comes into the housing, passes through the cartridge wall from the outside in, and leaves through the bore to the pump. The outside of the cartridge is the dirty side. The bore and the outlet underneath it are the clean side, and the clean side is the one you must protect during the change.

• Lift the cartridge straight up. Tipping it sideways in the housing scrapes the loaded outer surface against the housing wall and drops the dust into the bottom of the housing, right next to the outlet.
• Keep it upright as you take it away and put it straight into a bag.
• Look at the old cartridge before you throw it out. Dust on the inside of the bore, or a clean band on one end cap where the gasket should have been pressed, means the old one was not sealing. Find out why before you fit the new one, or the new one will do the same.

Cleaning the housing

Put a clean rag over the outlet before you clean anything. Then wipe or vacuum the inside of the housing, the seat the bottom end cap sits on, and the underside of the cover. Lift the rag out last.

Look at the sealing faces while they are clean. A dent in the seat or a hardened, flattened cover gasket will stop the best cartridge from sealing. Busch's R 5 manual also lists an inlet screen at the suction connection that can partially clog and stop the pump reaching its usual pressure. If you have the pump open, check the screen as well.

Check the size before it goes in

We list 58 cartridges under Busch numbers, and several of them are close enough in size that you can push the wrong one into a housing and close the cover on it.

Four pairs from our catalogue show how close they get:

• 13 mm in height. The 0532000022 and the 0532500008 are both 51 mm across with a 31 mm bore. The first is 162 mm tall, the second 149 mm. Put the shorter one in a housing built for the taller one and the cover never clamps the top end cap. Gas goes over the top of the cartridge instead of through it.
• 1 mm across and 2 mm in height. The 0532000015 is 64 mm by 72 mm. The 0532000005 is 65 mm by 70 mm. Both have a 38 mm bore and the same 34 m3/h flow rating.
• 2 mm across. The 0532000031 is 58 mm across, the D000103364 is 60 mm. Both are 40 mm tall with an 18 mm bore.
• Identical size, different rating. The 0532000004 and the 0532121864 are both 150 mm by 88 mm by 222 mm. One is rated for 450 m3/h, the other for 425 m3/h. Both fit. Fit the number your pump calls for.

Across the whole Busch range we stock, sizes run from 39 mm across and 39 mm tall (rated 11 m3/h) up to 302 mm across and 472 mm tall (rated 3,507 m3/h). Stand the new cartridge next to the old one and compare the three numbers: outer diameter, bore and height. If anything differs by more than you would expect from a used gasket, stop and check the part number before you go further.

Watch for a second, smaller bore. Our data lists a smallest inner diameter of 5.2 mm on the 0532000022 and D000103364, and 10 mm on the 0532000025, besides their main bore. That figure is a hole in one end cap, so those cartridges are closed at one end. Fit them the same way up as the cartridge that came out.

Busch part numbers also appear in several formats on old cartridges and invoices. Our 0532000002 cartridge (98 mm across, 60 mm bore, 71 mm tall, used on Busch RA 0025 F, RA 0040 F and RA 0063 F pumps) is also listed as 532002, 532002000, 532002002, 532002003, 532002030 and 053202030. If the number on your old cartridge does not match a listing exactly, try it without the leading zero or check the compatibility page.

Fitting the new cartridge

• Check both end caps and any gaskets on the new cartridge. They should be flat, complete and stuck down all the way round.
• Lower it straight down onto the seat. Do not slide it across the seat, which can roll or pinch the bottom gasket.
• Make sure it sits centred and square. On housings with a centre bolt or a spigot, it should drop on without being forced.
• Close the cover evenly. If the housing uses several screws, tighten them a little at a time in a cross pattern so the cover comes down flat on the top end cap.

First start and the first week

Start the pump with the process isolated if your system allows it, and let it pull down. Busch's troubleshooting table names a partially clogged inlet cartridge as one cause of a pump not reaching its usual pressure, so a pump that now pulls down as it did when the old cartridge was fresh tells you the new one is clear and sealing.

If it pulls down worse than before, the usual suspects in order are: the cover not clamping the cartridge (wrong height), a pinched or missing gasket, the wrong cartridge entirely, or a fault that was never the filter. Busch lists worn internal parts as another cause of poor ultimate pressure. Our guide to measuring rotary vane pump vane wear covers that check.

For the first week, look at the oil. Busch links black oil to a defective inlet filter. If the oil darkens quickly after a filter change, the cartridge is letting dust past and the seal is the first thing to check.

How often to check it

The current R 5 manual says to check the inlet filter cartridge monthly and replace it if necessary, and it warns that high dust loads in the process gas can make it necessary to shorten maintenance intervals significantly. The older R 5 F manual says that where powder, dust or grit is present, the cartridge should be cleaned weekly or as required. The monthly check is a minimum, not a target.

A cartridge change is a good moment to look at the rest of the service. Busch's schedule for the RA 0165 to 0305 D pumps calls for the oil, oil filter and exhaust filters every 2,000 hours, or at the latest every 6 months. Exhaust filters for Busch pumps sit with our separators, and the full range of inlet cartridges is under air filter cartridges. For vanes and other wear parts, see vacuum pump parts.

Frequently asked questions

Can I run a Busch pump without the inlet cartridge while I wait for a new one?
Busch's manuals call for an inlet filter of 5 micron or less (10 micron or less in the older F series manual) whenever the gas carries dust or solids. If your process carries dust, running without the cartridge sends it straight into the oil and the vanes. Fit the new one before restarting.

Can I blow out a paper inlet cartridge and reuse it?
The older R 5 F manual talks about cleaning the cartridge weekly in dusty use. The current R 5 manual says check monthly and replace if necessary. If you clean one, do it away from the pump so the dust does not settle back in the housing, and replace it if the media is torn, soft or oily.

My old cartridge has no readable number. How do I find the right one?
Measure the outer diameter, the bore and the overall height in millimetres, note whether both ends are open, and send the numbers with the pump model through our quote request form. As the pairs above show, a few millimetres matter.