Vacuum pumps and systems are one of the widely used equipment in process plants. It is very important to correctly size and select the vacuum pump as it is to lay down the right specifications. Understanding the fundamentals of vacuum as well as the system and its integration would enable the operators to deal with the day to day problems, which are inevitable.
This article highlights various trouble shooting guidelines for some of the most commonly used vacuum machines like liquid ring vacuum pumps, rotary piston vacuum pumps, dry vacuum pump, rotary vane vacuum pump and vacuum blower.
Several factors govern and influence the performance of a vacuum system. It is important to periodically inspect the vacuum system and all its accessories including the upstream and down- stream piping and equipment for leakages as it plays a major role in the performance of a vacuum system.
Some of the common problems faced in vacuum systems could be on account of the following major factors:
- Process conditions and variations
- Variation in utility specs
- Equipment malfunction
The suction load, temperature, leakage rate and other process parameters including the composition of suction gas are crucial for proper functioning of a vacuum system. These parameters can be estimated as per the standards of the Heat Exchange Institute and other standards. These standards can also be applied for testing the performance of the vacuum system. Once the external step is to evaluate and solve the problems associated with the vacuum unit.
Some of the most commonly observed problems in different kinds of vacuum pumps along with suitable trouble-shooting guidelines are discussed in this article.
Causes of high horsepower can be various. Comparing actual data with performance curve is the best starting point. Probable causes are:
- V-belt misalignment and improper tensioning of the
- Pump is severely overloaded with
- Restriction at the pump inlet or pump discharge
- Motor problem
- Pump running at a speed above the required
If the seal water is leaking from the pump, a careful observation of the exact location of the leak and the quantity of the leakage should be carried out. Most likely areas of leakage are:
- Gland packing area – It can be resolved by tightening the packing and if leak still persists, replace the
- Leakage at body gasket – Torque the body bolts evenly, if leak does not stop, then replace the body
- Leakage at the body plugs – Tighten the plugs. If leak still persists, check for corrosion on plug threads and body threads. Replace plug if corrosion is
- Leakage through castings – Causes can be erosion, corrosion or insertion of a hard object into the
Noisy Pump Operation
Noisy pump operation could be due to:
- Foreign object trapped into the pump – This is a very serious case and is usually accompanied by erratic noise and
- Pump severely overloaded with water – Causes groaning and hydraulic
- Cavitations – Sounds like marbles in the
- Bearing noise – Possibility of bearing
- Lots of carryover to the pump – This is accompanied by high
Vacuum Problems Could be due to:
- Vacuum surges – Surging is often caused by carryover from separators, or from low points in the line that accumulate water that burp over periodically into the pump. Look for piping problem in the inlet
- Restriction in the pump inlet piping – This could be due to closed or partially closed valves, object in the line, plugged inlet screen, etc. This restriction will cause pressure drop that gives low vacuum in the system and a higher vacuum in the
- Check for correct seal water flow – Excessive or inadequate seal water flow will adversely affect vacuum
- Variation in seal water temperature – If temperature of the seal water is too high, the pump may operate at a reduced capacity. The higher the vacuum level, the more important it is to have cool water in sufficient
- Variation in pump rpm – If rpm is low, pump will run at a lower capacity. Check motor and V- belt.
- System leaks – Sources of leaks can include open drain valves, blown gaskets, loose flanges, poorly packed valves, inadequate barometric drop legs on separator, broken pipes etc. Higher leakage will result in lower
- Warn pump – This is indicated if vacuum loss has been gradual over a period of time. Check to see if any before the vacuum problem
Vibration problems could sometimes be due to system problems but at times could also be related directly to the pump. They can be broadly classified into two categories, namely intermittent and continuous.
- Check for liquid slugs or carry-over from
- Check for low pockets in inlet piping where liquid can accumulate and burp over into the vacuum pump at irregular
- Check for irregular sources of vibration originating. Piping or separators can be the source of vibration if they are not properly secured in place or
- Look for constant carryover and / or excessive seal water to the
- Look at discharge piping or level indicator to be sure that the pump is not operated when in flooded
- Check coupling or V-belt alignment and
- Make sure pump is not started against blank suction subjecting it to immediate high vacuum. This does not allow the ring to form
- If the unit is gear driven, make sure vibrations are not from gear
- Check pump mounting and alignment. Loose feet, improper shimming, resonating bases and improper grouting can set up unwanted
- Check bearings and lubrication and replace failed
- Check the inlet piping for
- Check pump for excessive