Gast vacuum pumps and blowers: filters, vanes and inspection

The advice is taken from Gast's operation and maintenance manuals for the Regenair blowers, the oil-free rotary vane pumps in the 23 series and the oil-free piston pumps and compressors. The diaphragm pumps are not covered here, and the blower manual does not apply to belt-driven SDR blowers without a motor or to blowers with explosion-proof motors.

Before you start

• Disconnect the power. If the pump is hard-wired, cut the power at the fuse or circuit breaker
• Some motors have thermal protection and restart automatically when it resets
• Release pressure and vacuum
• Let the surfaces cool down, and wear safety glasses. The airflow may contain particles or liquid

Regenerative blower: filter and silencer

After the first 500 operating hours, the filter elements and the foam in the silencers should be checked, and the motor and blower cleaned. Replace the filter elements, and decide how often the silencers should be checked from then on. According to Gast, this one step helps to ensure performance and service life.

If the pressure difference across the inlet filter increases, it has started to clog. Replace the cartridge when the filter can no longer be cleaned. Gast recommends two vacuum gauges, one before and one after the filter, so you can see how much the filters are restricting the flow. Clogged filters reduce efficiency.

Filters are required. The blower must be installed with correctly sized inlet and in-line filters, gauges and relief valve, and the impeller runs very close to the housing. The filter elements in Gast's accessory range have 10 micron filtration.

Regenerative blower: operation, temperature and noise

Do not throttle the pipes on the suction or pressure side to reduce capacity. That increases the pressure difference, the power requirement and the operating temperature.

Run the blower for an hour after start-up, and check the room temperature and the exhaust air temperature. The exhaust air must not exceed 102 °C on blowers under 3.5 hp and 135 °C on blowers over 3.5 hp.

If the noise increases, the foam in the silencer may be damaged and should then be replaced. If the impeller is rubbing against the housing, the blower must go to a Gast-authorised service centre. As causes of unusual noise, Gast lists a damaged or dirty impeller, which should be cleaned or replaced, and bearings that are about to fail. If it is the bearings, the blower must go to a Gast-authorised service centre.

Regenerative blower: lubricating the bearings

Motors under 5.5 hp have bearings that do not need grease. Larger motors have grease nipples and should be given one or two shots of Exxon Polyrex grease from a grease gun. Gast specifies these intervals for blowers with grease nipples:

• 5 000 operating hours a year: every three years
• Continuous, normal operation: every year
• Seasonal operation, where the motor stands idle for 6 months or more: every year, at the start of the season
• Continuous operation at high ambient temperature, or in dirty or damp surroundings: every 6 months

Oil-free rotary vane pump: filter and silencer

The oil-free rotary vane pumps in the 23 series must not be lubricated. The vanes run dry, the bearings are sealed and grease-packed, and petroleum or hydrocarbon products shorten the life of the carbon vanes. Do not put oil in an oil-free pump. The 23 series also comes in an oil-lubricated version with its own operating instructions, so check the rating plate before you do anything. Routine maintenance:

• Remove the end cap and filters, and look for tears, cuts, brittleness and heavy soiling
• Clean filters that are in good condition with compressed air and check them again
• Check the filter/silencer section for compacted dirt, and replace it if you find any
• The O-ring should be soft and elastic. If it is not, replace it
• Remove and clean the silencer box on the models that have one, and replace the gasket if it has cracks or tears

The vanes

When you remove the end plate, the vanes should move freely in and out of the slots. Replace them if more than 50% of the vane sticks out of the slot. Note which way the bevelled edges face before you remove the vanes, and refit them the same way.

Check the end plate, rotor and housing for scoring. Heavy scoring or worn bearings require servicing at a Gast-authorised workshop, and the rotor and motor bolts must not be loosened.

The motor must run in the right direction. If it runs the wrong way, the vanes can break or be damaged, and if the motor does not run as it should, the life of the vanes is greatly reduced.

The service kit usually contains vanes, gaskets and filter parts. The end plate and silencer box are tightened to 90–120 in-lb. Gast does not guarantee the performance of pumps that have been reconditioned in the field. For guaranteed performance, the pump must go to a Gast-authorised workshop.

The pump can also be flushed to remove dirt, particles, moisture or oil picked up from the surroundings, so that the vanes work as they should. Use only a flushing agent recommended by Gast, or one that is not petroleum-based. Do not use paraffin or other flammable solvents, and flush in a well-ventilated place.

Oil-free piston pump

The piston pumps are also oil-free. The rings are Teflon-filled and self-lubricating, and the motor bearings are grease-packed for life. Here too, no oil should be added.

Check the inlet and outlet filters after the first 500 operating hours, clean them, and decide how often they should be checked from then on. Replace the filter felt when it is full of dirt or when the pressure difference across it increases.

If the pump runs at full load in a reasonably clean environment at 18–24 °C and 35% relative humidity, the first inspection and maintenance should be done after 4 000 operating hours. Other conditions may require maintenance sooner.

Measure the thickness of the rider ring. It should be more than 0.055 inches. If it measures 0.055 inches or less, all the rings must be replaced.

The service kit usually contains head and cylinder gaskets, valves, piston rings and seals, rider rings and filter felt. Clean the parts with water or a non-petroleum-based solvent, such as Gast AH255B.

Tank-mounted piston pump

• Check the air filter cartridge. A dirty filter restricts the airflow, and the unit runs hotter and for longer
• Check the tank for moisture at regular intervals. Humidity determines how quickly water collects
• Keep the pump and motor clean. Dirt and deposits on the outside make it harder for them to dissipate heat
• If the pump cycles on and off more often than when it was installed, drain the water that has collected in the tank
• If the pump runs more often than when it was installed, look for air leaks or new equipment that uses air, clean the filters, look for deposits of foreign matter on the head and check the valves and rings for wear and damage

Shutdown and storage

For both the rotary vane and the piston pumps, Gast has a shutdown procedure to prevent damage. The piston pumps are made of ferrous metals or aluminium, which rust and corrode when they pump vapour that condenses, such as water. Before storage and between periods of operation:

• Disconnect the pipes
• Run the pump for at least 5 minutes with no pipes connected
• Run it at maximum vacuum for 10–15 minutes
• Run it again for at least 5 minutes without pipes
• Disconnect the power
• Plug the open ports so that no dirt gets in

Ordering parts

Gast asks for the full model and serial number when ordering parts. You can reach industry parts sales on mobile +47 900 44 148, and the workshop on +47 969 13 856 during the day. You can also order parts using the parts order form on Spare parts.