Hydraulic motor performance reasons for the decline

Date:2016-04-14
1) hydraulic motor wear
WTZ-150 series and WTZ-200 installed on the drilling rig is mainly 6K-195 6K-310 and two models of the hydraulic motor. After dismantling it found that the friction surface of the hydraulic motor and valve plate valve plate badly worn, wear a maximum depth of 0.15 mm; an output shaft seal leakage.
(2) Assignment wears reasons
From this kind of hydraulic motor works, valve plate and connected by a small cycloid rotor axis linked together, while doing the slide valve plate is rotated in the valve disc. This friction causes excessive wear for the following reasons:
Just install the new hydraulic motor, the hydraulic oil in the absence of filling the motor housing, the friction surface of the friction caused by the lack of sufficient lubrication and wear. Especially with the beginning of work on a large load, exacerbated by the valve plate wear.
Filter hydraulic system failure of the hydraulic oil mixed with particulate impurities, small particles into the friction surface of the port plate rotation, the friction surface abrasive wear.
Friction surface valve plate and valve plate due to wear roughness deteriorates, the friction between the vice substance storage space increases, the surface of the particles into the friction with the grinding down of the metal particles rotate with the valve plate, increasing the wear and tear.
Since the valve plate and wear between the valve plate, the hydraulic oil in the feed, resulting in a gap between the return oil passage and communication, under high pressure, the sealing of hydraulic oil, cleaning, thermal performance, oil temperature increase, according to the Canadian wear.
Inability to reason (3) of the hydraulic motor
According to the valve plate wear Cause Analysis shows that the main cause of the inability to reason hydraulic motors as follows:
Since the valve plate wear, forward, back to the oil channel in the port plate at communicating, some high pressure oil discharge flowing through a given pair of hydraulic rotor decline, reduced flow, eventually leading to the motor output speed and torque down.
Since the valve plate wear, which occurs in the relative position of the valve body changes, on the body of the spring preload and stick together to reduce the valve plate and the valve disc between the intensified hydraulic oil leak, causing the hydraulic motor performance.
Improve the hydraulic oil temperature, resulting in its overall performance, its ability to rotate the drive gerotor decline further.
The inspection rotor and its deputy sides with binding surface of the bearing housing and the valve disc no significant wear. No motion normal catching and will not cause performance degradation.
(4) the reasons for the output shaft seal leakage
Dismantling the detection test, the output shaft axial and radial clearance in line with standard surface, the output shaft seal and no significant wear. But we found that aging rubber seals hard, elastic variation. After the seal lip wear and seal oil preload performance degradation, high oil temperature accelerates the oil seal lip wear; In addition, since the inner vent the hydraulic motor, causing back pressure within the housing is too high, so that oil seal lip wear and oil spills further.
Repair method
From the above analysis, as long as the restoration of the complex relationship between the valve plate and valve disc friction pair, you can restore the performance of the hydraulic motor. And matching the right output shaft seal, to eliminate the oil leakage of the hydraulic motor.
(1) Valve Plate repair
After the valve plate clean, blown clean with compressed air. With an outside micrometer or dial indicator measuring the oil pan thickness h1 and no amount of wear wear at (h1 measure is to provide the basis for the adjustment of the valve plate and preload spring force).
Valve plate due to wear serious (0.10 mm ~ 0.15 mm), if more laborious by hand grinding, decided to adopt the surface grinder grinding. Grinding, end valve plate to the inlet side of the reference plane, the choice of 60 # white corundum grinding wheel.
(2) repair of the valve disc
Same disc grinding and polishing requirements of the port plate, not just the amount of grinding, without its thickness measured. When the grinding disc and the formation of friction with oil pan mating surfaces, an abrasive surface symmetry plane.
Because local disc has an outer surface of the paint and its edge by the external force locally uneven, it affects the accuracy of the polished surface. So before polishing should be cleaned and trimmed, conditions can be exposed at the chamfer 45 ° (width 1 ~ 1.5mm), and then check the flatness, flatness grinding plane should ≤0.01mm. It should be to ensure compliance with the requirements of the reference plane, and then the end face of its symmetrical polished.
Optional (3) of the output shaft seal
ETN 6K series hydraulic motor output shaft oil seal skeleton without using spring-type seal (VC type). Seal initial preload by rubber material and the amount of interference between the shafts produced when the seal lip or shaft wear, sealability decreased, resulting in oil spills, leakage of the hydraulic motor which is the main reason. ETN 6K series hydraulic motor in accordance with the United States EATON CORPORATION product design and manufacturing technology to produce products, and its products with inch size standard. Through the journal, seal mounting base hole and seal thickness measurements, the journal size φ44.43 mm, seal installed base pore size φ 63.5 mm, seal thickness 4 mm.
Seal of wearing parts, the seal is not good English standard procurement, and long lead times. To improve service performance and general performance of the output shaft seal, we decided to follow the principle of change does not change the size or less, which was changed to metric standards to ensure its original performance and strength.
Crude oil seal using VC (ie a single outer rubber lip seal skeleton without spring) type, its poor sealing, short life. According to the working conditions and structural dimensions of the hydraulic motor, the available SC (single lip with In spring outer rubber skeleton SEAL) or SB (single outer lip with a spring steel skeleton SEAL) oil seals in place, these two types of VC-type seal than the seal sealing effect, long service life.
Choose its compatibility, operating temperature range of adaptability and lip seal materials work force to follow the axis of rotation of the decision. Typically lip temperatures than its hydraulic oil temperature high 20 ~ 50 ℃, the linear velocity <15 m / s. Commonly used sealing materials NBR, compound rubber, fluorine rubber, silicone rubber, polypropylene acid ester rubber, ethylene propylene rubber, PTFE, nylon, POM, chloroprene rubber, fluoro silicone rubber and polyurethane.
6K-195 hydraulic motor maximum speed is 866 r / min, and the size of the output shaft seal mating surfaces as φ44.43 mm, its maximum line speed = C × n / 60, where C is the circumference of the journal, n is maximum speed of the shaft.
Maximum line speed = C × n / 60 = 44.43 × 3.14 × 866/60
= 2013.6 mm / s
≈ 2 m / s
Normal operating temperature of the hydraulic system is 82 ℃, since the drilling rig in the late stage, the hydraulic system technology performance, coupled with the impact of hydraulic component failure of the hydraulic oil temperature, oil temperature should consider the value of increasing the height of 20 ℃, which the lip temperature above the temperature of the working medium 20 ~ 50 ℃ (maximum value 50 ℃), finalize the temperature tolerance of the lip seal 152 ℃.
According to the above analysis of the oil seal working environment, compared to the performance of various sealing materials, fluorine rubber seal material selection decisions.
The output shaft journal size as the original φ44.43 mm grinding φ44 + 0.05 mm, the diameter of seal housing bore original φ63.5 mm Turning to 64 mm. Since the seal mounting position wide margin, seal thickness as 8 mm. All data (see table) is selected as an integer, help seal selection.
Overall output shaft is quenched and tempered treatment, after grinding its hardness and seal mating surface of oil and more than 30HRC (general requirements for taking the rotating shaft surface hardness 30 ~ 40HRC).
According to the above analysis of the optional seal, we decided to use SC or SB type, size, fluorine rubber seal φ44 × φ64 × 8 alternative to the original VC-type seal. Interference and the amount of interference with the journal seal lip seal between the outer diameter of the seat between the holes is determined by the manufacturer in accordance with relevant standards.
Assembly and test (4) of the hydraulic motor
6K-195 type cycloid hydraulic motor in the assembly, in addition to the provisions and requirements of the assembly, but when you install the valve plate should be separately mounted in the port plate thickness Δh three preload spring seat hole (Δh = h1-h2) steel adjustment shims to ensure preload valve plate and the valve disk between.
Repair completed by a hydraulic motor, to carry (out) were injected into the oil port T46 # anti-wear hydraulic oil 100 mL, and bi-directional rotation of the output shaft several turns rotating smoothly without lag card, a port will keep the air flow, another oil through the mouth into the 0.6 ~ 0.8 MPa compressed air to drive the hydraulic motor commissioning. After commissioning normal, the hydraulic motor to complete the repair work.
(5) Effects and Benefits
Repair using the above method, rehabilitated 6K-195,6K-310 type hydraulic motor 14, have been normal use, and has been for more than three months of work, extend the old hydraulic motor cycle. Single hydraulic motor repair costs less than $ 300, if the replacement of a new hydraulic motor need funds about 6,000 yuan, only 14 of the hydraulic motor which can save money 70,000 yuan, the unit has made significant economic benefits.

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