11312_10_Progressing Cavity Pumps, Downhole Pumps and Mudmotors

8/14/2019 11312_10_Progressing Cavity Pumps, Downhole Pumps and Mudmotors

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M any P C pum p startups are the culmination of months, if notyears, of work designing the process, machine or system, speci-fying com ponents, instrum entation , protective devices, review-ing and qualifying suppliers, etc . It is also the m ost vulnerabletime for any pu m p. T h is section describes cau tions, reviews,and inspections that should be conducted before startup tohelp ensure that all of those many gremlins of pumping sys-tems are found ou t and addressed in time.

T ho ro ug hly read the technical manuals and instructionsfrom the p um p, driver, and all auxiliary equipm en t suppliersto uncover requirements that may be specific to their equip-ment design. This is the easiest method to protect the systembut is overlooked more often than no t.Pipe and ValvesPiping and valving installation should probably be consideredfirst. Be sure all required valves have been installed. "Verify that

Chapter 10PROGRESSING CAVITY PUMPSTARTUPS


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none are installed backwards. An absent or reverse-mountedcheck valve, foot valve, or relief valve can cause some very seri-ous damage. Piping should have been inspected during fabrica-tion to en sure that weld bead, weld ro d, scale, etc. have beencompletely removed. Such hard particles can cause pum p dam -age should they lodge in the wro ng pu m p clearance. Tem po-rary or permanent pump inlet strainers should be considered ifthey are not presen t, and they should start in a clean conditionso that accumulation of dirt can be monitored. Obviously, ifthere is solids conten t in the liquid, strainers may not be neces-sary or desirable, but strainers offer inexpensive protection forthe pum p and valves in clean services.The piping system should be pressure tested. Avoid im-posing pressures in excess of any system component's designlimits. Many pumps can withstand discharge pressure only ontheir discharge side. Inlet piping systems are frequently suit-able only for low pressure. T h e pressure test medium shouldbe compatible with the components and system being tested.A low pressure (e.g., 15 psig) compressed air test may be ade-quate to find missing flange gaskets or other obvious leaksources.

Check and tighten all flange bolts to their specifiedtorque. The pump inlet and discharge piping should beginapproximately 20 feet (6 meters) away from the pum p to m ini-mize pipe strain on the pu m p. Pip ing should be independentlysupportedpumps do not make very good pipe anchors!When pipe flanges are unbolted from the pump, the flangebolts should be able to be installed or removed without fore-


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ing th e piping into position. T h e re should be a flange-to-pum p gap n ot exceeding the greater of twice the flange gasketthickness, or Yi6 in. (3 mm). If either is not true, rework thepiping until the gap meets this specification.

Positive displacement pumps will normally have a systempressure relief valve installed from the discharge piping toeither the source of the pum ped liquid, such as a supply tank,or to the pu m p inlet piping (a less desirable poin t due to thepotential for temperature buildup during relief valve opera-tion). This valve will normally be set slightly higher than themaximum anticipated normal system operating pressure. Ifpossible, verify that it has been properly set. If this cannot beverified, consider setting the relief valve to a very low pressureand adjusting it upward after pum p startup. Consu lt the reliefvalve vendor's technical data to be sure valve adjustment isdone in the correct direction to lower the pressure. Whenpumping high solids content liquids, relief valves may not befunctional and a pressure switch to shu t down the pum p drivemay be a better choice to protect th e pu m p, drive, and systemfrom the adverse effects of excessive discharge pressu re. R up -tu re (blow-out) disks are also a viable means of over-pressureprotection when handling high solids content liquids. Theseare one-tim e-use th in m etal disks designed to rupture a t a spe-cific pressure. T h e dow nstream side of the disk must be p ipedto a location tha t can accep t flow after disk ruptu re un til th epum p can be stopped.

Ideally, the entire piping and valve system will be thor-oughly flushed to remove all dirt and fabrication debris. This


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is normally done using a flush pump, not the normal systempu m p. As applicable, strainers and /or filters are installed a t ap-propriate locations; their dirt accumulation is m onitored untilthey show no accumulation for a period of 24 hours. F lushingusually uses light, fairly hot (1500F) liquid delivered at flowrates higher than system design. The higher flow rates causehigher liquid velocities within the piping system and are morelikely to dislodge deb ris. Som e systems use vib ration eq uip -ment to mechanically shake the piping, again to improve dis-lodging d irt. Very extensive p iping systems have been know nto still show debris accumulation after 30 days of flushing.

Before final startup, be sure valves are open or closed asrequired. Pump inlet and discharge valves are normally leftfully open . M anu al p um p bypass valves are also no rm ally leftopen on sta rtup. An air bleed valve in th e discharge piping at ahigh point near the pump will significantly improve thepump's ability to self-prime. The valve is left open duringstartup until liquid flows, and then it is shut. Be sure to knowwhere this flow will be directed to avoid inadvertent spillageor discharge to the atmosphere. Steam turbine valving is veryimportant. Turbine startup procedures should be thoroughlyreviewed as there are personal injury issues associated withthis equipm ent if started or operated improperly.Foundation, Alignment, and RotationIf horizontal pumps are used, be sure the foundation is level, thathold-down bolts are tight, and that grou ting, if used, has com-pletely filled the base plate (no hollows or voids) and has cured.


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has no thing to do with the shaft-to-shaft alignm ent of theequipment. Survival and longevity of the machinery, not thecoupling, are the objectives. If hot pumps and/or drivers areused, after they are at nominal operating temperature longenough for thermal growth to have stabilized (probably onehour or m ore), shut down the equipment and verify tha t align-ment is within proscribed limits.

Never rely upon the alignment that was produced where thepum p and drivetrain were assembled. Transp ortation , lifting,and h and ling, as well as foundation irregu larities, will impactalignmen t always in an undesirable direction. Final a lignmentshould be established as nearly the last step before actuallystarting the pu m p. If the equipm ent is to be dowelled in place,do so to the pu m p only after several hours, if not days, of goodoperation and alignment checks.

T he use of resilient moun ts is sometimes desired to reducevibration being transmitted into the underlying foundation.Such mounts must not be installed beneath the pump ordriver, but between the pum p/driver base plate or bracket andthe foundation. The pump and driver must be rigidly aligned,no t resiliency aligned, as the resilient mo un ts will no t m ain-tain adequate alignment under torsional reactions from thetransmitted torque.

T he direction of rotation is critical for m ost equ ipm ent. Itis usually indicated by arrow nameplates. Remember thatsome gearing will reverse rotation from the input shaft to theoutput shaft. M ost engines and turbines m ust be purchased fora specific direction of rotation, and this is also true of most


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pumps. Standard AC electric motors are frequently bidirec-tional; their direction of rotation will depend upon how thepower cables are connected. It is norm ally not possible to pre-dict their direction of rotation beforehand. It is recom mendedtha t the flexible coupling at the m oto r shaft be disconnectedand the mo tor mom entarily energized fogg ed on, then im me-diately off) to see if its rotation is correct for the rest of thedriven equipment. If it is not, two of the electric power cableswill need to have their connections reversed. Verify correctrotation after reversing, if necessary, before re-engaging theflexible coupling.LubricationMost rotating machinery has some form of lubrication for itsbearing systems. It may be as simple as a perm anently grease-packed, sealed ball bearing or as complicated as a separatelubricating oil-pump system complete with cooler, filter, in-strum entation , e tc. Be sure to verify tha t any required lubrica-tion has been addressed. Equipment having been in storagemay require draining and addition of fresh lubricant or evenflushing out of preservatives before fresh lubricant is added.Any gearing present (reduction drive gears, etc.) should bereviewed for the presence of the co rrec t type and quan tity oflubricant. Constant level oilers should be filled to their markwith clean, fresh lubricant of the correct type. Some flexiblecouplings are grease-lubricated and should also be checked.M os t electric m oto rs will have grease -lubricated antifrictionbearings that should be checked as well. P C pu m p eccen tric


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joints, if lubricated, are normally filled with grease or oil at thepump manufacturer's plant.

Almost all rotary pum ps should be able to be turned over byhand. They should generally turn over smoothly, with no catchesor uneven rubbing. Large pumps will need a helper bar butshould no t be difficult to tu rn . If not, consult the pum p vendor.Partial disassembly may be advisable to determine the cause ofsuch difficulty (foreign material, rust, etc.) before starting.Startup SparesWith care and planning, startups will generally go smoothly,without significant problems. However, it is prudent to havekey spare parts on hand in the event they are needed quicklyfor correction after some unanticipated p rob lem , m inor dam -age, or need to disassemble a piece of equipment for inspec-tion. Fo r P C pum ps, this would norm ally be a set of shaft seals,gaskets, O-rings, and bearings, frequently available as a minorrepair kit. For other rotating equipment, spare bearings, greaseand oil seals, gaskets, etc. should be on hand to avoid delay inthe pum p startu p. M ore extensive spares will depend on avail-ability from the vendor, criticality of pump operation, plantpractice and, perhaps, other issues specific to the installation. Ifthe startup goes well and the spares are no t consum ed, they arevery appropriate to be held on hand for future rou tine inspec-tions and service.ResourcesBe sure electric power, steam, cooling water, hot oil, instru-mentation power or air, or any other auxiliary resources are


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available and ready before startup. Be sure adequate pressureand temperature gages are in place so observations can bemade during startup. W itho ut th em , you are working blind.Speed indicators (tachom eters) m ay also be needed if the driveis no t a fixed-speed one , such as an A C electric motor.

Last-Minute Startup ThoughtsIt is good practice to initially fill the pump and as much of theinlet piping system as possible with the liquid to be pumped.This will assist in priming and reduce the risk of pump dam-age du ring an otherwise d ry start. A rotary pu m p will primem ore quickly if internal p um ping elements are at least wetted.Prim ing is noth ing m ore than pum ping air from the inlet sys-tem to th e discharge system. T h e ability of a rotary positivedisplacement pump to act as an air compressor is very muchrelated to having some interna l liquid presen t.Pump shaft seals, especially mechanical seals, should neverbe operated dry. Immediate, or at best premature, seal failureis the inevitable result. Again, filling the pump with the liquidto be pum ped and ha nd -rotating the pum p a few times he lpensure that liquid is present at the shaft sealing mechanism tocarry away frictional heat during startup. If the particularpum p has a seal cham ber access plug, remove the plug, fill thechamber with liquid, and reinstall the plug.

Have p hon e num bers of key vendo r service dep artm ents,the fire brigade, and medical emergency services on hand inthe event they are needed. Depen ding on th e liquid pum ped,there m ight be pollution and fire hazards presen t.


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Ensure that there is an adequate supply of liquid in thepum p inlet system (no half-empty supply oil tanks or the like).It is also prudent to confirm where the pump discharge flowwill be go ing to be sure th e discharge system is ready.

Loud or erratic noise at startup is an indication of cavita-tion (inadequate pump inlet pressure) or air being drawn intothe pump inlet system. It is frequently accompanied by in-creases in o r excessive vibration . If this is mild, troub lesho otthe cause. If it is severe, shut down the pump and find thesource of the prob lem .

Use the Rotary P um p Startup C hecklist (see page 201) ora similar control to help ensure that all contingencies havebeen addressed. Each pum ping system has unique features andrequ irem ents, some of which may interact w ith each othe r orwith other aspects of the overall plant operation. In addition,no allowance has been m ade here for regulatory requirem ents,specialized indus try or company guidelines, or the like. W hereoperational values are recommended, they are intended foruse in the absence of vendor or specifically eng ineered infor-mation. Always use the more stringent of either the recom-mendations herein or the vendor's or engineer's guidelines.


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1. PipingCleanBolts tightStrain removedGaskets in placePressure testedFlushedOther

2. ValvesNot backwardsCleanBolts tightGaskets in placeCorrect position (open/closed)Relief valve set pressureOther

3. FoundationLevelSolid (no voids)Bolts tightOther

Rotary Pump Startup ChecklistProject:TagNo.:_

Location:, Unit No.:,


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4. AlignmentAngular (cold & hot)Parallel (cold & hot)Other

5. RotationVerified (C W or CCW )Other

6. LubricationPumpDriverGearOther

7. Spares AvailablePumpDriverGearOther

8. Resources AvailableElectricSteamCooling waterHot oilAuxiliariesGages in placeOther


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9. Last-MinutePump filled with LiquidShaft seals wettedKey contact phone numbersInlet liquid supplyDischarge system readyAir bleed valve openPump hand-rotatedOther

10. Company- or Industry-Specific

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11312_10_Progressing Cavity Pumps, Downhole Pumps and Mudmotors