Engineering machinery hydraulic piston pump and maintenance of the use of the latest methods

Engineering machinery hydraulic system mainly depends on the efficiency of hydraulic pump volume efficiency, when the volume efficiency decreased to 72%, is the need for routine maintenance, replacement of bearing and aging seals, to replace or repair beyond the friction pair of fit clearance, make its performance restoration.

This article is given priority to with straight axis swash-plate plunger pump, introduces the use and maintenance method.

1 hydraulic pump oil form

Plunger pump can be divided into direct axis swashplate pressure oil supply type of imbibition oil type two kinds. Pressure oil supply type hydraulic pump pressure tank in most used, a hydraulic pump itself there is oil supplement offer hydraulic pump inlet pressure oil pump. Imbibition oil type hydraulic pump self-priming capacity is very strong, without external force oil supply.

On hydraulic pressure oil tank, after each start the machine, after must wait for hydraulic stains box to use pneumatic to operate machinery. If less than when the pressure of the hydraulic oil tank has served in the machine, can slip within the hydraulic pump on with a whip, pulled off phenomenon will cause return plate in the pump body and linking piece of abnormal wear. Replacement pump plunger pump oil, use after 3000 h, operators need of plunger pump to check daily 1 to 2 times, check the pump running sound is normal. When the hydraulic cylinder speed drop or stuffy car is found, it should be the disintegration of oil pump inspection, check the wheel rim for scratch phenomenon, the internal gear pump clearance is too large.

For imbibition oil plunger pump, hydraulic oil within the tank oil shall not be lower than the lower limit, to maintain a sufficient number of hydraulic oil. The higher the purity of the hydraulic oil, the longer service life of the hydraulic pump.

2 hydraulic pump bearing

Plunger pump is the most important components of the bearing, if the bearing clearance, not guarantee hydraulic pump internal three normal clearance of friction pair, at the same time also damage the friction pair of hydrostatic bearing oil film thickness, reduce the service life of the plunger pump bearing. The information provided according to the hydraulic pump factory, bearing an average service life of 10000 h, more than this value will need to replace new mouth.

Removed the bearing, no professional testing instrument is unable to detect the bearing clearance, can only use visual, if discover to there is scratches or roller surface discoloration, it must be replaced.

Should be paid attention to when change the bearing, the English letters and model of the original bearing, plunger pump bearings are mostly adopted the load bearing capacity, had better buy the original factory, the specifications of the products, if change another brand, should consult a look-up table to bearing experienced personnel exchange, the purpose is to keep the bearing level of accuracy and load capacity.

3 three of friction pair of inspection and repair

3.1 plunger rod and cylinder hole

According to the following method to repair:

(1) set of copper set of cylinder body, can adopt the method of replacement of copper set of repair. First put a set of piston rod diameter dressing to uniform size, with more than 1000 # sandpaper polishing outer diameter.

Block installing copper set of three ways:

(a) cylinder heating hot charging or copper set of cold extrusion, interference assembly; (b) have loctite adhesive assembly, this method requires copper coat outside diameter surface of groove; (c) cylinder hole tapping, processing copper sleeve diameter thread, tuliey Thai rubber after screwing in assembly.

(2) combining ways of cylinder body and copper tubes, repair method is as follows:

(a) using grinding rods, manual or mechanical lapping repair cylinder hole; (b) using coordinate boring machine, cylinder boring again; (c) the reamer repair cylinder body hole.

(3) using the surface engineering technologies, as follows:

(a) plating technology: a layer of hard chromium plating in the plunger surface; (b) the brush plating technology: in the plunger surface brush plating wear-resistant materials; (c) the thermal spraying or electric arc spraying or electric spray: spraying high carbon martensite wear-resistant materials; (d) laser deposition: in the plunger surface deposition of high hardness, wear resistant alloy powder.

(4) cylinder hole without copper set of materials are mostly of nodular cast iron cylinder body, in the preparation of amorphous thin film or coating on the inner wall of the cylinder block. Because cylinder hole wall with this special material, so hard to form hard - matching of friction pair. If blindly grinding cylinder body hole, dropped the cylinder hole wall this layer surface material research, the structure of the friction is more performance has changed. By removing coating friction pair, if forced to use, will be friction surface temperature rise sharply, the plunger rod and cylinder hole agglutination.

In the plunger rod surface preparation a unique film coating, coating contains antifriction + + wear-resisting lubrication function, this group of friction pair is actually a hard - soft pairing, once a person to change coating, also destroyed the best matching material of the friction pair, repair these special plunger pump, will be sent to the professional repair shop.

3.2 sliding boots and swash plate

Sliding boots and inclined plate of the sliding friction is inclined plate of plunger pump of friction pair of the most complicated of the three.

Table 1 lists the plunger rod ball head and sliding boots ball clearance, if the plunger and out-of-tolerance, sliding boots gap plunger cavity of high pressure oil from plunger ball head and emission in the sliding boots clearance, sliding boots with the inclined plate oil film thinning, caused serious static pressure bearing failure, sliding boots with the inclined plate metal contact friction, sliding boots ablation, plunger ball head scratching the swash plate. Plunger rod ball head and sliding boots ball beyond tolerance 1.5 times, must be replaced in groups.

Plunger rod and the cylinder piston rod diameter 16 phi phi is 20 to 30 35 phi phi phi phi 25 and 40

Standard clearance 0.015 0.025 0.025 0.030 0.035 0.025

Limit interval 0.040 0.050 0.060 0.070 0.080 0.090

Plunger rod ball head

With sliding boots ball socket standard clearance 0.010 0.010 0.015 0.015 0.020 0.015

Limit interval 0.30 0.30 0.30 0.35 0.35 0.35

Swash plate after a period of time, can appear inclined plate plane concave phenomenon, before using platform grinding, should first original size and hardness measurement. After grinding, to measure what is grinding, such as within the 0.18, use of plunger pump without hindrance; If you exceed more than 0.2 mm, should adopt the method of nitride to keep the original thickness of nitriding layer.

Swash plate plane piston ball head scraping out groove, the method of laser deposited alloy powder can be used to repair. Laser deposition technology can not only guarantee the bonding strength of material, can ensure the hardness of filling molten material again, and does not reduce the hardness of surrounding tissue.

Chromium also suitable to use for the manual welding, welding rod repair welding of the inclined plate surface need to heat treatment, had better use nitriding furnace heat treatment. No matter adopt what kind of method to repair inclined dish, must restore the original size precision, surface roughness and hardness.

3.3 with flow on the surface of the valve plate and cylinder repair

Valve plate with plane flow and spherical flow in two forms.

Spherical flow friction pair, lighter scratches on surface of the cylinder block with flow, by means of grinding to repair, Cylinder valve surface groove is deep, should be filled by "surface engineering technology" means groove, for grinding, grinding not blindly, and in case of copper layer thinning or leak out steel base.

Planar flow form of friction pair can be grinding precision higher platform.

Cylinder and valve plate before grinding, should first to measure the total thickness of the size of the size and should be stripped away, compensation to adjust the mat. Valve disc grinding amount is larger, should be back after grinding heat treatment.

Plunger pump parts hardness standard

Recommend hardware hs84 plunger rod

The plunger rod ball head recommended hardness > hs90

Swash plate surface recommended hardness > hs90

Valve disc recommended hardness > hs90

Valve plate and cylinder after repair, can use the following method to check with the leakage situation, namely in the valve disk coated with vaseline oil, exhausted, the drainage way with good oil valve plate flat on the platform or on flat glass, and then put the block valve tray, in the cylinder hole injection diesel, want interval oil, namely, filling a hole a hole not oiling, observe more than 4 h, piston diesel leakproof and complicity in the hole, cylinder and valve disc grinding is qualified.

4 conclusion

The length of the service life of the plunger pump, and the usual maintenance, quality and quantity of hydraulic oil, the oil cleanliness and so on. To avoid the oil particles of plunger pump friction pair wear, etc., is also an effective way to extend the life of the plunger pump.

In maintenance replacement parts should try to use the original factory production parts, these parts are sometimes price is more expensive than other fake parts, but the quality and stability is better, if the purchase price cheap imitation parts, saving the cost seems to be in the short term, but it brings hidden trouble, may also use of plunger pump cause even more damage.