Simple Vacuum Pump Maintenance

Many oil-filled rotary-vane vacuum pumps are in service 24 hours a day, 7 days a week. With proper maintenance, these pumps have a service life of many years. Vacuum pump maintenance should be part of your regular lab operations.

Pump Basics

Oil-filled mechanical high vacuum pumps consist of two primary parts: an electric motor and a vacuum pump. The electric motor spins the pump. The pump consists of rotating parts and valves to create the vacuum. There is a certain amount of regular maintenance required to get the best performance and longest life from your pump. To understand vacuum pump maintenance, think of the pump as your car's engine, without the internal combustion.

Backup Pump

To minimize the downtime of your system, keep a spare operational pump in your lab as a backup. If your in-service vacuum pump fails, swap in your backup and have your failed pump repaired. This lets you get your system back in service ASAP, with minimum stress. Get your failed pump repaired in a timely manner. If you use many pumps with different capacities, you may want to have multiple backup pumps. If you have pumps that have been taken out of service due to water contamination or unknown reasons, it may be in your best interest to know the condition of the pump. If a pump with water contamination sits too long, then oxidation may render it not worthy of repair. Gaver Services will tear down a pump for diagnosis at no charge. If applicable, customer pays shipping charges.

Oil Change

Contaminated rotary pump oil is by far the major performance and failure problem. You need to create your own maintenance schedule, based on how and what applications you run in your lab. The industry standard is to change the oil at least every 3000 hours. For a pump that runs 24x7, that's 125 days or approximately 4 months. Some labs synchronize pump oil changes with the preventative maintenance of their other precision scientific equipment, which is usually every 6 months. This is acceptable if the application is clean and dry.

For some applications the oil may need to be changed much more often. In some cases, the pump oil may need to be changed every week or after every run. Vacuum pump procedures for wet chemistry are discussed in a separate document.

If the oil is discolored or contaminated, the pump may not pull a good vacuum. Failure to change the oil per an appropriate schedule will result in eventual failure that can have several forms, including irreparable damage to the pump.

Oil Change Procedure

• Run the pump until it reaches normal operating temperature. This may take a few minutes. The oil will drain faster and more fully when warm. Turn off the pump.
• Arrange the pump and drain bucket so that you catch all the oil as it comes out. One way is to place the pump on a workbench with the drain plug is just over the edge and a bucket (e.g. plastic paint bucket) placed on a chair below the oil drain plug.
• Tilt the pump up at the end opposite the drain plug for a more complete oil drain.
• Remove the oil filler plug at the top of the pump to let air in so that the oil will drain freely and smoothly.
• Holding the bucket closely underneath, open and remove the drain plug with the o-ring. The oil will squirt out a few inches, then the flow will move to under the plug. Place the bucket back on the chair. When the stream becomes a drip, the oil is out. Replace the oil drain plug with the o-ring. If you drop the drain plug and/or o-ring into the bucket, it should be easy to pull them out.
• Refill the pump with oil to the maximum level indicator. Replace the oil filler plug.
• If the drain oil is very dirty, you may want to repeat the drain process until the drain oil is cleaner. Very dirty oil means that you need to change the oil more often.

Temperature Control

The pump must be well ventilated. Install the pump in an open-air area, or ventilate with a fan if the pump is enclosed. Keep the pump away from hot equipment and out of hot rooms. Too much heat will cause premature pump failure. Excessive heat makes the oil less viscous, so that the pump may not pull a good vacuum. If your pump does not pull a good vacuum, your other expensive scientific equipment works harder and fails sooner. Excessive heat also makes the rubber parts in your pump become brittle and fail. An excessive external oil leak is often a sign of rubber parts failure.

Overheated Oil

Unintended application conditions can make a pump work beyond its capacity and overheat the oil. When the oil is overheated, it often has a burned odor. Overheated oil can harden when it cools, which will lock-up the pump.

A common cause of overheated oil is a gross vacuum leak. Most of these pumps are not designed to run continuously at higher pressures - typically 10 Torr or greater. The applications that these pumps serve run at lower pressures. A gross vacuum leak can bring the pressure up to a level that is unacceptable in the long term. Use a gauge on your application and/or be wary of the smell of overheated oil. Gross vacuum leaks are common at demountable equipment joints. Check your hoses, fittings, and o-rings.

Intake Control

The intake port of the pump will suck in anything available; it does not discriminate. Please take care that only filtered gases enter the pump. Liquids and/or solids entering the pump, especially water, will cause premature pump failure. If a pump fails due to water entry, it should be repaired ASAP. The water will destroy the pump's internal metal parts due to oxidation. Unavoidable vapor contamination requires more frequent oil changes.

Oil Leaks

All oil-filled vacuum pumps will leak. Pumps often sit on fabric or paper towels in cafeteria or small cookie trays to prevent small leaks from making a mess. Excessive oil leaks often happen with age. This may mean that the pump needs an overhaul. Running too low on oil will cause catastrophic pump failure. Pumps with excessive oil leaks should be repaired in a timely manner.

Noises

A vacuum pump should quietly hum. Some pumps that have been in service for years may chatter a little, but still pull a good vacuum. Pumps that make loud noises should be taken out of service and repaired. Noises may be coming from the pump and/or the electric motor. Loud noises mean problems that may become much more serious and expensive if not repaired soon.

Unknowns

Sometimes, despite your best efforts, a pump may stop running or seize with no warning. Gaver Services can evaluate what happened. We will tear down your pump for diagnosis at no charge. If applicable, customer pays shipping charges.

Monitoring

Sometimes maintenance is not done properly or on schedule. Some simple monitoring can save you downtime and expense. Access may be limited and you may get dusty, so wear clothing that is appropriate. Refer to the sections above if you find questionable conditions.

• Is the pump making any loud noise? Loud noises should be fixed for the health of the pump and anyone who is near the pump.
• Is there enough oil in the pump? Check the sight glass on the pump. Top up if necessary.
• Is the oil clean? Check the sight glass on the pump. There should not be visible contaminants. The oil should be nearly the same color as new oil. The sight glass gives a limited view of the oil, so any visible discoloration usually means that the oil should be changed.
• Is the pump well ventilated? If not, move to a more open area or ventilate with a fan.
• Does the oil smell burned? If so, then find out what is making your pump run too hot.
• Is the pump leaking excessively? Other than making a mess, this may mean that your pump needs to be overhauled.

The use of scientific laboratory equipment involves risk of personal liability and property damage. Gaver Services provides suggestions to improve the efficient use of high vacuum pumps and assumes no responsibility for how an individual may interpret or apply this information.