TIPS AND RECOMMENDATIONS FOR PUMP USERS
This is a collection of tips and recommendations accumulated over years of pumping experience. Key words are in bold and color so scanning the text for a particular word or phrase is quick. If you have one to add, please click here to send us an e-mail. Keep your tip to less than 100 words, preferably less than 50. Specify whether or not to credit you and/or your company. No guarantees well use your tip but we encourage all to send in one or more. We may edit for clarity or brevity. Users of these tips/recommendations are cautioned to understand that not all of them are applicable under all circumstances and judgement is necessary to avoid property damage or personal injury. Neither Imo Pump nor persons or companies contributing these tips/recommendations warrant them as suitable for any particular purpose or use.
28 May 1999- If installation includes main and standby pumps, rotate their usage at least once a month. Pumps and drivers not operated for prolonged periods frequently fail on startup. Rust, water accumulation, sediment accumulation and other factors contribute to a lack of reliability. If pumps are frequently started and stopped, have each start use the next sequential pump.
28 May 1999- If main and standby pumps are operating in a hot liquid system, consider bleeding a small amount of discharge flow back through the non-operating pump to keep it at system temperature. Be careful to avoid pressurization of the system suction side.
28 May 1999- Do not expose a cold rotary positive displacement pump to hot liquids nor visa versa. Internal pump clearances cannot change uniformly very quickly and such operation risks pump seizure. Especially avoid cold liquid flush of a batch hot liquid pump. Thermal shock can cause serious pump damage.
28 May 1999- If applying heat tracing (thermal wire, steam/hot oil tubing, etc.), be sure to avoid heat tracing bearing areas and timing gears as these items usually need to operate well below about 200° F (98° C).
28 May 1999- Pipeline pumps and others may need "soft start" systems to allow a large volume of liquid within the line to accelerate in a controlled fashion until up to normal velocity. Soft start is most commonly achieved using an electric motor driven, open bypass valve around the pump or back to the supply tanks. It is closed slowly (30 to 60 seconds typical) so flow is gradually diverted from recirculation to entering the pipeline. Other soft start systems have used fluid couplings for slowly increasing pump speed as the pipeline can accept flow or other variable speed drive arrangements.
28 May 1999- Any loading or unloading facility (truck terminals, rail cars, barges, ships, etc.) should be sure they can detect when the supply of liquid ceases flowing to the transfer pumps. Dry running most pumps can cause damage, if to nothing else, then at least the shaft seals.
28 May 1999- Pipe strain can be particularly hard on rotary positive displacement pumps as their internal clearances are smaller than centrifugal type pumps.
28 May 1999- Be especially careful of low differential pressure/high viscosity operation if the pump design is such that it relies on differential pressure to provide shaft seal internal flush. Close running clearances may require alternate seal flush arrangements.
28 May 1999- Static testing of pumps under high vacuum may cause damage to mechanical seals. Consult pump or seal vendor before such testing.
28 May 1999- If field hydrostatic testing, either block out the pumps or be sure the pump suction side is rated for the test pressure. This is especially true for high pressure pumps as their inlet side may be designed to handle only several atmospheres of pressure.
28 May 1999- If at all possible, do not salvage/reuse antifriction bearings. Their removal usually entails some fairly heavy doses of pulling and pushing on the wrong races and internal damage or deterioration can appreciably effect the bearing life. New bearings are not so expensive that saving their cost is worth the unknown life reduction let alone the cost of premature downtime.
26 May 1999- If electric arc welding near pumps, be certain a sold ground is near to the weld location and away from the pump. Otherwise, arcing may occur inside close pump clearances. This can damage pump parts and cause catastrophic failure on startup. Jim Brennan, Imo Pump, Monroe, NC, USA
26 May 1999- Vent pump discharge on initial startup to help pump gain initial prime. If liquid is dangerous, arrange to contain any leakage from venting. Internally wetted pumps prime faster than dry. Jim Brennan, Imo Pump, Monroe, NC, USA