【机械类毕业论文中英文对照文献翻译】泵
【机械类毕业论文中英文对照文献翻译】泵,机械类毕业论文中英文对照文献翻译,机械类,毕业论文,中英文,对照,对比,比照,文献,翻译
外文原文 毕业设计外文原文Standard Handbook of Petroleum & Natural Gas Engineering by Lyons, William C.; Plisga, Gary S.Publication: Burlington, MA Elsevier, 20053.3 PUMPSPumps are a mechanical device that forces a fluid to movefrom one position to another. Usually a pump refers to themechanical means to move incompressible (or nearly incompressible)fluid or liquid. Pumps are our earliest machine and are to this day one of our most numerous mechanical devices. Pumps are a very essential part of the oil and gas industry. They are used throughout the industry, from drillingoperations through to final delivery to the customer.3.3.1 ClassificationsPumps are classified into two basic classes, displacementand dynamics. The most widely used pumps in the oil and gas industryare reciprocating displacement pumps (in particular pistonplunger type), the rotary displacement pump, and the centrifugaldynamic pump. Only these pumps will be discussed in detail.The reciprocating and rotary positive displacement pumpsprimary characteristic is that they have a nearly direct relationshipbetween the motion of the pumping elements andthe quantity of liquid pumped. Thus, in positive displacementpumps liquid displacement (or discharge from thedevice) is theoretically equal to the swept volume of thepumping element. Figure 3.3.3 shows the typical positivedisplacement plot of discharge rate Q (ft3/s) versus pressureP (lbs/ft2) 3. The discharge rate remains the same(assuming a constant rate of rotation for the system) regardlessof the pressure in the flow. The pressure in the flowis, of course, the result of resistance in the flow systemthe pump discharges to. If the resistance increases, rotationcan be maintained and more force applied to each strokeof the pump (i.e., power). This is why the reciprocating pistonplunger pump is also called a power pump. In practice,pressure does have some influence on the capacity of thesepumps. This is because as the pressure increases, there issome leakage of the seals in the system. This leakage issomewhat proportional to the pressure, particularly beyondsome characteristic pressure related to the seals. The differencebetween theoretical flow and the actual flow of a pumpis often referred to as slip. This slip is shown in Figure 3.3.3. In the dynamic pump, in particular, the centrifugal pump,the discharge rate Q is determined by the resistance pressureP in the flow system the pump discharges to (assumingsome given speed of the pump). This is illustrated in Figure 3.3.4. 3.3.3 Reciprocating PumpsThe piston plunger pump is the simplest form of a positivedisplacement pump. These pumps can be powered bya variety of prime movers, internal combustion engines, andelectric motors (and in some cases, powered by a gas turbinemotor). In such applications, the separate pump unit isconnected to the prime mover by a power transmission.The capacity of a pump is determined by the number ofplungers or pistons and the size of these elements (bore andstroke). A reciprocating pump is usually designed for a specificvolumetric rate capacity and pressure capability. Thesefactors are set by the application. Once the volumetric ratecapacity and pressure capability are known, a designer candetermine the plunger piston bore and stroke the rotationspeed range and the power of the prime mover needed tocomplete the system. Reciprocating pumps are fabricated in both horizontal andvertical configurations.3.3.3.1 Single-Acting PumpA single-acting pump has only one power (and discharge)stroke for its pistons. Such a pump brings fluid into its chamberthrough the inlet or suction value or the piston is drawnbackward to open the chamber. To discharge the fluid, theinlet valve is closed and the outlet valve opened as the pistonis forced forward to push the fluid from the chamber intothe discharge line. The piston motion is accomplished by arotating crankshaft that is connected to the piston by a pistonrod much like an internal combustion piston engine. Therotating crankshaft of the pump is rotated by the rotationalpower of the prime mover (through a transmission) 7.The single-action pump is usually available with three, fiveand even seven pistons. The odd number of pistons allowsthe pump to be rotationally balanced, and the use of at leastthree pistons reduces the discharge pulsation of these single-actingpumps. A three piston pump single-action pump iscalled a triplex pump. A five piston, or seven piston single -actingpump is called a multiplex pump.3.3.3.2 Double-Acting PumpDouble-acting pumps have two power strokes. As a pistonof the pump is pushed forward, the fluid is discharged fromthe forward chamber into the discharge line (much like asingle-action piston). But during this same stroke, the chamberbehind the piston (which contains the connecting rod)is being filled via that chambers inlet valve (Figure 3.3.5).When the forward power stroke is complete and the fluid dischargedfromthe chamber in front of the piston, the chamberbehind the piston is filled. The crankshaft continues to rotate,requiring the piston to begin a rearward stroke. During thisstroke the fluid behind the piston is forced from its chamberinto the discharge line via the outlet valve and the chamberin front of the piston refills via its inlet valve 7.Double-acting pumps are usually available with one or twopistons.A one-piston double-action pump is called a double-actingsimplex (since there are older single-action steam and pneumaticdriven simplex pumps).A two piston double-action pump is called a duplex pump.3.3.3.3 Flow CharacteristicsAll reciprocating pumps have a pulsating discharge. This isthe result of the piston motion as it stops and reverses. Atthis moment, the flow from that piston theoretically dropsto zero. Thus, the discharge curves as a function of timeare those illustrated in Figure 3.3.6.By having two or more pistons the pulsation of the discharge from the pump can besmoothed out and the magnitude of the pulsation reduced ifthe pistons motions are timed for proper dynamic balancingof the pump (Figure 3.3.7). For those pumps that have largepulsations, a cushion change (or accumulator) may be usedin the discharge line to reduce or eliminate the pulsations(Figure 3.3.8).Single acting mud pump pistonDisclosed is a single acting mud pump piston assembly adapted for use in a mud pump mechanism including a piston and having an end portion with a shoulder reciprocatingly mounted in a cylinder. The assembly includes a circular flange mounted on the end portion in abuttment with the shoulder. A hub is removably mounted on the end portion in abuttment with the flange. A piston cap is mounted about the hub in abuttment with the flange. The assembly is held together by a washer and a nut engaging the end portion.A piston assembly for use in a single acting mud pump including a cylinder and a piston rod reciprocatingly mounted in the cylinder, said piston rod including a cylindrical end portion and a radially outwardly extending shoulder, said piston assembly comprising: a circular planar flange having an outside diameter less than the inside diameter of the cylinder and having a bore through the center thereof, said bore having a diameter substantially equal to the diameter of said cylindrical end portion of said piston rod, said flange being adapted to be carried on said cylindrical end portion in abuttment with said shoulder; means for forming a seal between said flange and said piston rod; a circular planar hub having an outside diameter less than the outside diameter of said flange and having a bore through the center thereof, said bore having a diameter substantially equal to the diameter of said cylindrical end portion of said piston rod, said hub having an axial thickness, said hub being adapted to be carried by said cylindrical end portion of said piston rod in removable abutting relationship with said flange; a circular elastomeric piston cup having a body with an outside diameter substantially equal to the outside diameter of said flange and an outwardly flaring annular lip having an outside diameter greater than the inside diameter of the cylinder, said piston cup having a bore through the center thereof, said bore having a diameter substantially equal to the outside diameter of said hub, said piston cup having a central portion surrounding said bore having an axial thickness at least equal to the axial thickness of said hub, said piston cup being adapted to be removably carried about said hub in removable abutting relationship with said flange; a circular planar washer having an outside diameter greater than the outside diameter of said hub and an inside diameter substantially equal to the diameter of said cylindrical end portion of said piston rod, adapted to be carried by said cylindrical end portion of said piston rod in removable abutting relationship with said hub and the central portion of said piston cup; and a retaining nut adapted to threadably engage said cylindrical end portion of said piston rod to urge said washer into abuttment with said hub and said central portion of said piston cup.A single acting mud pump mechanism which comprises: a cylinder having an inside diameter; a piston rod reciprocatingly mounted in said cylinder, said piston rod including a threaded cylindrical end portion and a radially outwardly extending shoulder; a circular planar flange removably mounted on said end portion in abuttment with said shoulder and having an outside diameter less than the inside diameter of the cylinder and having a bore through the center thereof, said bore having a diameter substantially equal to the diameter of said cylindrical end portion of said piston rod; means for forming a seal between said flange and said piston rod; a circular planar hub removably mounted on said end portion in abuttment with said flange and having an outside diameter less than the outside diameter of said flange and having a bore through the center thereof, said bore having a diameter substantially equal to the diameter of said end portion of said piston rod, said hub having an axial thickness; a circular elastomeric piston cup removably mounted about said hub and in abuttment with said flange and having a body with an outside diameter substantially equal to the outside diameter of said flange and an outwardly flaring annular lip having an outside diameter greater than the inside diameter of the cylinder, said piston cup having a bore through the center thereof, said bore having a diameter substantially equal to the outside diameter of said hub, said piston cup having a central portion surrounding said bore having an axial thickness at least equal to the axial thickness of said hub; a circular planar washer removably mounted about said end portion and having an outside diameter greater than the outside diameter of said hub and an inside diameter substantially equal to the diameter of said cylindrical end portion of said piston rod; and a retaining nut threadably engaged with said cylindrical end portion of said piston rod to urge said washer into abuttment with said hub and said central portion of said piston cup.The basic difference between reciprocating motion and circular motion The piston or plunger works within a watertight cylinder. Thebasic difference between a piston and a plunger should be notedA piston is shorter than the stroke of the cylinder;the plunger is longer than the stroke. Another distinguishing featureis that the packing is inlaid on the rim of the piston for a tight seal.When a plunger is used, the packing is moved in a stuffing boxlocated at the end of the cylinder to provide a tight seal.Principles of OperationIn general (and with respect to the way that the water is handled),reciprocating pumps may be classified as lift pumps or force pumps,which in turn, are either single-acting or double-acting pumps.Lift PumpsA lift pump is a single-acting pump; it consists of an open cylinderand a discharge or bucket-type valve (see Figure 5-3). An opencylinder and a discharge or bucket-type valve in combination are thebasic parts of the lift pumpit lifts the water, rather than forces it.In the lift pump, the bucket valve is built into the piston and movesupward and downward with the piston.A four-stroke cycle is necessary to start the lift pump in operation(see Figure 5-4). The strokes are as follows:_ Air exhaustThe piston descends to the bottom of the cylinder,forcing out the air._ Water inletOn this upward stroke, a vacuum is created.Atmospheric pressure causes the water to flow into thecylinder. After the pump has been primed and is in operation, the workingcycle is completed in two strokes of the pistona downward strokeand an upward stroke (see Figure 5-5). The downward stroke of thepiston is called the transfer stroke, and the upward stroke is calledthe intake and discharge stroke, because water enters the cylinderas the preceding charge of water is being discharged.Force PumpsThe force pump is actually an extension of a lift pump, in that itboth lifts and forces the water against an external pressure. Thebasic operating principle of the force pump is that it forces waterabove the atmospheric pressure range, as distinguished from the liftpump, which elevates the water to flow from a spout. 4.4 MUD PUMPSMud pumps consume more than 60% of all the horsepowerused in rotary drilling. Mud pumps are used to circulatedrilling fluid through the mud circulation system whiledrilling. A pump with two fluid cylinders, as shown in Figure4.4.1, is called a duplex pump. A three-fluid-cylinder pump, asshown in Figure 4.4.2, is called a triplex pump. Duplex pumpsare usually double action, and triplex pumps are usuallysingle action. Pumps with six chambers are commerciallyavailable as well (Figure 4.4.3).Mud pumps consists of a power input end and a fluid outputend. The power input end, shown in Figure 4.4.4 transferspower from the driving engine (usually diesel or electric) tothe pump crankshaft. The fluid end does the actual work ofpumping the fluid. A cross-section of the fluid end is shownin Figure.4.4.5.4.4.1 Pump Installation4.4.1.1 Suction ManifoldThe hydraulic horsepower produced by mud pumps dependsmainly on the geometric and mechanical arrangement of thesuction piping. If suction-charging centrifugal pumps (e.g.,auxiliary pumps that help move the mud to the mud pump)are not used, the pump cylinders have to be filled by thehydrostatic head.Incomplete filling of the cylinders can result in hammering,which produces destructive pressure peaks andshortens the pump life. Filling problems become moreimportant with higher piston velocities. The suction pressureloss through the suction valve and seat is from 5 to10 psi. Approximately 1.5 psi of pressure is required foreach foot of suction lift. Since the maximum available atmosphericpressure is 14.7 psi (sea level), suction pits placedbelow the pump should be eliminated. Instead, suction tanksplaced level with or higher than the pump should be used toensure a positive suction head. Figure 4.4.6 shows an idealsuction arrangement with the least amount of friction and lowinertia.A poorly designed suction entrance to the pump can producefriction equivalent to 30 ft of pipe. Factors contributingto excessive suction pipe friction are an intake connectionwith sharp ends, a suction strainer, suction pipe with asmall diameter, long runs of suction pipe, and numerous fittingsalong the suction pipe. Minimizing the effect of inertiarequires a reduction of the suction velocity and mud weight.It is generally practical to use a short suction pipe with alarge diameter.When a desirable suction condition cannot be attained,a charging pump becomes necessary. This is a commonsolution used on many modern rigs. 4.4.1.2 Cooling MudMud temperatures of 150 can present critical suction problems.Under low pressure or vacuum existing in the cylinderon the suction stroke, the mud can boil, hence decreasingthe suction effectiveness. Furthermore, hot mud acceleratesthe deterioration of rubber parts, particularly when oil ispresent. Large mud tanks with cooling surfaces usually solvethe problem.4.4.1.3 Gas and Air SeparationEntrained gas and air expands under the reduced pressureof the suction stroke, lowering the suction efficiency. Gasin water-base mud may also deteriorate the natural rubberparts used. Gases are usually separated with baffles or bychanging mud composition.4.4.1.4 Settling PitsThe normally good lubricating qualities of mud can belost if cuttings, particularly fine sand, are not effectivelyseparated from the mud. Adequate settling pits and shaleshakers usually eliminate this trouble. Desanders are usedoccasionally.4.4.1.5 Discharge ManifoldA poorly designed discharge manifold can cause shockwaves and excessive pressure peaks. This manifold shouldbe as short and direct as possible, avoiding any sharps turns.The conventional small atmospheric air chamber, often furnishedwith pumps, supplies only a moderate cushioningeffect. For best results, this air chamber should be supplementedby a large atmospheric air chamber or by aprecharged pulsation dampener.4.4.2 Pump Operation4.4.2.1 PrimingA few strokes of the piston in a dry liner may ruin the liner.When the pump does not fill by gravity or when the cylindershave been emptied by standing too long or by replacement ofthe piston and liner, it is essential to prime the pump throughthe suction valve cap openings. 4.4.2.2 Cleaning the Suction ManifoldSuction lines are often partly filled by settled sand and bydebris from the pits, causing the pump to hammer at abnormallylow speeds. Frequent inspection and cleaning of thesuction manifold is required. The suction strainer can alsobe a liability if it is not cleaned frequently.4.4.2.3 Cleaning the Discharge StrainerThe discharge strainer often becomes clogged with piecesof piston and valve rubber. This may increase the pumppressure that is not shown by the pressure gauge beyondthe strainer. The strainer should be inspected and cleanedfrequently to prevent a pressure buildup.4.4.2.4 Lost Circulation MaterialsUsually special solids, such as nut shells, limestone,expanded perlite, etc., are added to the drilling muds to fillor clog rock fractures in the open hold of a well. Most ofthese lost circulation materials can shorten the life of pumpparts. They are especially hard on valves and seats whenthey accumulate on the seats or between the valve body andthe valve disc.4.4.2.5 Parts StoragePump parts for high-pressure service are made of preciselymanufactured materials and should be treated accordingly.In storage at the rig, metal parts should be protected fromrusting and physical damage, and rubber parts should beprotected from distortion and from exposure to heat, light,and oil. In general, parts should remain in their original packageswhere they are usually protected with rust-inhibitingcoatings and wrappings and are properly supported to avoiddamage. Careless stacking of pistons may distort or cut thesealing lips and result in early failures. Hanging lip-type orO-ring packings on a hook or throwing them carelessly intoa bin may ruin them. Metal parts temporarily removed frompumps should be thoroughly cleaned, greased, and storedlike new parts.
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