CN103835987A - Low-temperature deep-well pump - Google Patents

Abstract

The development trend of a marine low-temperature deep-well pump is that the marine low-temperature deep-well pump is reliable at low temperature, necessary net positive suction head is low, efficient and energy-saving effects are achieved, and maintaining is convenient. According to the current status and the development trend, the structural design is broken through for the SCW low-temperature deep-well pump, a high-pressure self-tightening structure design is adopted, and magnetic suspension bearings are adopted. New material, such as high polymer material, is used so that the characteristics of safety, reliability, corrosion and leakage resistance and vibration and noise reduction of the marine low-temperature deep-well pump can be enhanced. In detail, a multi-stage impeller structure is adopted for achieving high lift, a mature inclined outlet deep-well pump hydraulic model is adopted, and a pump inlet is matched with an inducer, so that an expected hydraulic performance is achieved; a stainless steel casting, a stainless steel shaft, a PTFE sealing element, a graphite sliding bearing and other materials are used for being adaptive to the low-temperature environment below 104 DEG C; a mechanical seal cavity is matched with a booster, meanwhile, the gas pressure reduction effect of an upper sliding bearing is used so that it can be guaranteed that pumped liquid does not leak outwards in the high-pressure operation process of the pump, and safety can be guaranteed; a shutdown seal design is adopted so that the pumped liquid can not leak outward in the maintaining process of the pump, and then environment safety can be guaranteed. Pipe segmenting, pipe flange connection and shaft hard coupler connection are used for reaching the 5 m-22 m depth below the liquid.

Description

Low temperature deep-well pump

Technical field:

The present invention relates to a kind of low temperature deep-well pump peculiar to vessel, carry liquid under sea.

Background technique:

Deep-well pump requires few with its infrastructure device, be affected by the external environment little, and solve self-priming problem and advantage easy to maintenance and be aboard ship used widely, and because deep-well pump peculiar to vessel is mostly used in very important position, therefore mostly need Classification society to authenticate.As applicating medium has water, lubricating oil, natural, liquid gas, industrial chemicals and CO2 etc.Conventional range of flow be 150m3/h to 800m3/h, current LNG Liquefied natural gas deep-well lift of pump peculiar to vessel is mostly 120m.Current low temperature deep-well pump adopts receded disk impeller mostly, and efficiency is not the highest.Cylindrical shell dismounting difficulty, is not easy to safeguard.Pump Spit Section is yielding, and stress is large, poor rigidity, and stress deformation is large, and vibration is large, easily resonance.And domestic low temperature deep-well pump design method is difficult to meet completely the objective design requirements such as performance parameter that user proposes, weight profile, reliability, environmental conditions.Meanwhile, in view of at present domestic weaker without the technical foundation of the aspects such as leakages, high-cavitation-resistance aspect especially peculiar to vessel at low temperature deep-well pump, leak, " three leakages " phenomenon of leakage of oil, gas leakage stops not yet completely.In the time that suction vacuum is greater than permissible suction head, there is cavitation phenomenons in pump.Mainly occur in impeller outer edge blade and cover plate, volute or guide wheel place, can not occur in blade inlet.For example, when flow is greater than design discharge, occur in the face of blade place of blade import near front shroud.In the time that impeller eye place pressure drops to by liquor charging body the saturation vapour pressure under operating temperature, will there is part vaporization in liquid, the bubble generating will enter zone of high pressure from low pressure area with liquid, can sharply shrink at zone of high pressure bubble, condense, its liquid around rushes at the shared space of former bubble with high speed, produces high-intensity shock wave, impact impeller and pump case, noise occurs and cause vibrations.Owing to being subject to for a long time the chemical corrosion effect of trace dissolved oxygen in impact force repeated action and liquid, impeller local surfaces occurs that spot even becomes spongy damage with crackle.

Conventional low temperature deep-well pump peculiar to vessel has following two kinds of main Types at present.

1. vertical independent discharge opeing monoshell volute pump, is shown in Fig. 1

2. pump impeller and stator part are multistage radially stator centrifugal pumps, and it is vertical overhung construction that pattern is installed, and sees Fig. 2

The development trend of low temperature deep-well pump peculiar to vessel is the reliability under low temperature, low necessary NPSH, energy-efficient and be convenient to safeguard.For this present situation and development trend, my company determines the deficiency that research and development can supplement existing product, meets the SCW flanker of technology trends.We break through in structural design, adopt the design of high pressure self-tightening structure, magnetic bearing etc.; Use new material as with macromolecular material, to strengthen the characteristic such as safe, reliable, corrosion proof and leakproof, vibration and noise reducing of low temperature deep-well pump peculiar to vessel.We are adopting Novel transmission design, manufacturing technology in addition.Structure is shown in Fig. 3

The water absorbing properties of water pump is normally weighed by allowable suct lift, and Hs value is larger, illustrates that the water absorbing properties of water pump is better, and in other words, anti-cavitation performance is better.But, for axial-flow pump, large-scale mixed flow pump and deep-well pump etc., normally negative value of its setting height(from bottom), impeller often must be positioned on minimum underwater, conventionally adopts " net positive suction head " to weigh their water absorbing properties for this class pump.

In order to prevent the generation of cavitation phenomenons, the condition of effective net positive suction head NPSHa of centrifugal pump below must meeting in real work:

NPSH _a＝(P _A-P)/(ρg)-Z _g-∑h _A-S≥NPSH _r

In formula:

NPSHa---available NPSH when centrifugal pump work;

NPSHr---essential net positive suction head when centrifugal pump work;

PA---suction pipe liquid level upward pressure;

The saturation vapour pressure of Pv---liquid under inlet temperature;

ρ---fluid density;

The setting height(from bottom) of Zg---pump;

∑ h _a-S---suction pipe drag losses.

From above formula, prevent the generation of cavitation phenomenons, the available NPSH must improve centrifugal pump work time.Want to improve these situations, can consider to do following improvement:

1, increase inlet pressure, reduce rotating speed

Increase centrifugal pump inlet pressure, can improve suction pipe liquid level pressure P A, suction pipe is set up to pressurization system, to ensure that PA is enough large, make fluid after suction pipe arrives the energy reduction in centrifugal pump pressure minimum point process, fluid still has enough pressure to ensure that it is greater than the saturation vapour pressure Pv of fluid itself.Have experimental research to show, centrifugal pump is worked under lower negative pressure and high-speed state, and the cavitation of pump is inevitably, sometimes in the starting stage less than 1 second, will there is serious cavitation phenomenons.Therefore the rotating speed while reducing centrifugal pump work, improves centrifugal pump inlet pressure, can effectively prevent the generation of cavitation.

2, increase inducer

Before centrifugal pump impeller, increase an aial flow impeller that blade loads is very low, be conventionally referred to as inducer.Inducer is different from general axial-flow pump, and its wheel hub is smaller, and blade angle is also little, and the number of blade is also few, and leaf grating density is large, and these features make it to have good anti-cavitation performance.The lift that inducer produces can play pressurization for follow-up centrifugal impeller, makes Centrifugal Impeller Inlet not produce cavitation erosion.Except inducer itself has good anti-cavitation performance, add that it is very near apart from pump intake, the energy reduction value between significantly reducing from pump intake to impeller inlet.

3, reduce hold-up vapor tension

Reduce the saturation vapour pressure Pv of fluid itself, and saturation vapour pressure and temperature there is close relationship.In the time that temperature raises, Pv also increases, otherwise Pv reduces.Therefore in oil transportation places such as oil depots, more easily there is cavitation phenomenons in summer in centrifugal pump, and the measure that they generally take is oil transportation at night.In service in actual production, can reduce suck pot liquid temperature, before pump, increase condenser or reduce fluid temperature (F.T.) in the raw modes such as cooling water of spraying of suction line, thereby reach the object that reduces saturated with fluid vapor tension.

4, circuit design

Reduce the drag losses of pipeline, that just requires will ensure that pipeline is short and straight in the time of design suction line, reduces the middle equipment such as elbow, valve of pipeline.Preferably ensure that entrance pipe internal diameter is greater than export pipeline internal diameter.

5, rational setting height(from bottom)

Adjust setting height(from bottom), can reduce the setting height(from bottom) of pump or the setting height(from bottom) of raising entrance container, prevention cavitation.The setting height(from bottom) of centrifugal pump need meet the following conditions:

Z _g≤(P _A-P _v)/(ρg)-∑h _A-S-NPSH _r

Allow degree of suction vacu um

For centrifugal pump is normally worked, Hs need meet the following conditions:

$H_s=Z_g+\left(C_s^2\right)/\left(2g\right)+\mathrm{\Σ}{h}_{A-S}\≤H_{\mathrm{sc}}$

H _sc＝H _s+0.3

In formula:

H _s---degree of suction vacu um when centrifugal pump work;

C _s---fluid is in the speed of centrifugal pump ingress;

H _sc---the critical degree of suction vacu um of centrifugal pump;

0.3---the safe clearance that national Specification adopts.

For preventing the generation of cavitation, the degree of suction vacu um just must reduce centrifugal pump work time.

Setting height(from bottom)

The setting height(from bottom) that ensures pump meets:

Z _g≤H _sc-(C _s ²)/(2g)+∑h _A-S

Also can adopt the mode of pouring in down a chimney, pump intake will have enough large pouring head like this, and guarantee centrifugal pump entrance under positive pressure, can obviously reduce H all the time _svalue.

Reduce flow velocity

Reduce flow velocity, the flow can suitably reduce centrifugal pump work time, or before design suction line, select a suction line that diameter is larger, thereby can reduce the flow velocity of suction pipe inner fluid.Also can before centrifugal pump, set up lowspeed pump, reducing in flow velocity, offer the certain energy of fluid, can not cavitate at pump intake ensureing.Before centrifugal pump, increase bypass valve also can suitably be adjusted the flow velocity of pump intake.

Reduce drag losses

Reduce ∑ h _a-S, except above-mentioned method, also can regularly clear up impurity, the dirt of centrifugal pump entrance channel, to ensure the smooth of runner, reduce flow resistance coefficient.

Improve the anti-cavitation performance of centrifugal pump itself

The structure and material of suitable adjustment centrifugal pump, can improve the anti-cavitation performance of centrifugal pump, thereby reduces centrifugal pump and occur in production run the possibility of cavitation.

Improve the structural design of pump intake

Suitably increase impeller eye diameter and blade inlet width, reduce absolute velocity and the relative velocity of impeller eye, but also need to take into account the efficiency of pump; Entrance edge of blade is to impeller inlet extension and reduce front shroud and impeller axis angle, reduces liquid stream from axially to transition degree radially, and distance between having shortened from pump intake to impeller eye has reduced liquid stream from the axial corner loss to radially.

Improve runner smoothness

Strengthen the smoothness of impeller eye place runner and streamlined, can reduce its drag losses, thereby strengthen the anti-cavitation performance of centrifugal pump, but that the making of high smooth degree and stronger streamline channel all requires material and manufacturing technology is too high, need higher cost to drop into.

Adopt the good material of anti-cavitation performance

In recent decades, the research and development of cavitation erosion resistant material has made great progress, and the application of cavitation erosion resistant material has improved the performance and used life of fluid machinery greatly, becomes one of effective way of decreasing cavitation destruction.Practice shows, the intensity of material, hardness, toughness are higher, and chemical stability is better, and the performance of anti-cavitation is better.In conventional centrifugal pump material, the materials such as rare earth alloy cast iron, high nichrome, stainless steel 2Crl3, ampco 9-4, intensity and toughness are high, hardness is high, chemical stability is good, have good anti-cavitation performance.

Summary of the invention:

We consider that multi-stage impeller structure improves lift in the time of design low temperature deep-well pump, pump intake is joined inducer and can reach lift and the net positive suction head of expectation, then adopt stainless steel part, PTFE sealing, graphite sliding bearing adapts to low temperature environment, hydraulic part adopts heavy wall design simultaneously, and Seal cage adds depressor; Adopt pipe segment design to increase the degree of depth under liquid, simultaneously for easy to maintenance, adopt the structure of hand hole and large borehole jack aperture to make pipe quick detachable, specific as follows:

1. adopt multi-stage impeller structure to realize higher lift.Adopt ripe deep-well pump hydraulic model, inducer is joined in pump inlet, reaches expectation hydraulic performance: turn up 1788rpm, and flow reaches 600m3/h, and lift reaches 149.5m, and efficiency reaches 84.3%, necessary NPSH 3.7m

2. use stainless cast steel part, stainless steel shaft, PTFE Sealing, the materials such as graphite sliding bearing adapt to reach the low temperature environment of subzero 104 degrees Celsius

3. liquid lower bearing adopts the lubricated graphite sliding bearing of product that pump rotor can freely be turned round at low temperatures

4. hydraulic part adopts heavy wall design, and mechanical seal chamber adds depressor, utilizes the gap hypotensive effect of upper sliding bearing simultaneously, and pumping liquid does not leak when guaranteeing pump high-voltage operation, guarantees safety

5. the design of parking sealer does not leak pump pumping liquid in the time of maintenance, thereby ensures Environmental security

6. all axial forces that heavy roller bearing unit energy bearing pump operation or weight produce

7. use pipe segmentation, pipe flange connects, and axle connects to reach the degree of depth under the liquid of 5-22 rice with hard coupling

8. adopt hand hole and large pipe box Minute Tubule Structures that pipe is easily filled readily removable, make pump be easy to safeguard

9. the design of fan makes bearing unit and machine sealing chamber not overheated, makes the pump can long-play

In sum, SCW series pump is moved more reliable at low temperatures, possesses lower necessary NPSH (under 1480rpm, minimum 1.1m), and higher efficiency (approximately 84.3%), with energy-conservation, is convenient to safeguard simultaneously more.

Brief description of the drawings:

Below in conjunction with drawings and Examples, the invention will be further described.

The independent discharge opeing monoshell volute pump appearance assumption diagram that Fig. 1 is traditional

Another kind of traditional pump impeller and the stator part of Fig. 2 is multistage radially stator centrifugal pump, and it is the appearance assumption diagram of vertical overhung construction that pattern is installed.

Fig. 3 is appearance assumption diagram in the inventive example

Fig. 4 is the stator impeller External view in the present invention

Fig. 5 is the External view of the cylinder assembly in the present invention

Fig. 6 is the assembly that spues of the pump in the present invention

Embodiment:

Referring to Fig. 3-6,

Stator and impeller assembly adopt the vertical monoshell spatial guide blade centrifugal pump of many sliding bearings.Efficiency is higher, radial force minimum, and sliding bearing number is many, thus sliding bearing life is long, and end thrust direction is fixed, and thermal shock distortion is little, vibrates littlely, and lifting easily, is shown in Fig. 4; Cylinder assembly adopts detachable type single tube band sliding bearing supporting structure.Axisymmetric, temperature impact is consistent, difficult deformation; Can dismantle separately with mounting cylinder body component in single body parts, be convenient to safeguard; Adopt grooved seal pad, easy centering between pipe: coupling adopts key connecting, is difficult for killing: sliding bearing adopts pumped medium lubricated, operates simplyr, sees Fig. 5; The pump assembly that spues adopts bearings electric machine support to connect, and electric machine support has 2-3 part, and single part is short, has reinforcing, not yielding, is difficult for continuing distortion after installing.Integrated stress is little, good rigidity, stress deformation is little, vibrate little, be difficult for resonance, see Fig. 6.

Claims (3)

1. a low temperature deep-well pumping improves lift by multi-stage impeller structure (1), pump intake is joined inducer and can reach lift and the net positive suction head of expectation, then adopt stainless steel part, PTFE sealing, graphite sliding bearing adapts to low temperature environment, hydraulic part adopts heavy wall design simultaneously, and Seal cage adds depressor; Cylindrical shell (2) adopts pipe segment design to increase the degree of depth under liquid, simultaneously for easy to maintenance, adopts the structure of hand hole and large borehole jack aperture to make pipe quick detachable.

2. the vertical monoshell spatial guide blade centrifugal pump of the many sliding bearings of employing of stator and impeller assembly in claim 1.Efficiency is higher, radial force minimum, and sliding bearing number is many, thus sliding bearing life is long, and end thrust direction is fixed, and thermal shock distortion is little, vibrates littlely, and lifting is easily.

3. claim 2 cylinder assembly adopts detachable type single tube band sliding bearing supporting structure.Axisymmetric, temperature impact is consistent, difficult deformation; Can dismantle separately with mounting cylinder body component in single body parts, be convenient to safeguard; Adopt grooved seal pad, easy centering between pipe; Coupling adopts key connecting, is difficult for killing; Sliding bearing adopts pumped medium lubricated.

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