Noise Analysis of Hydraulic Piston Pump

When hydraulic rams used in construction machinery emit excessive noise during operation, this is a harbinger of damage to the pump. Hydraulic ram pump (hereinafter referred to as pump) there are the following eight kinds of noise conditions. Hydraulic plunger pump noise analysis 1. Inherent noise pump inherent noise that pump manufacturing technology has not yet reached the required. For pump mode of operation, each revolution of the pump spindle, each pump plunger to make a suction to the oil cycle. Plunger in the completion of the suction, pressure oil in the distribution process, the cylinder piston cavity overshoot of high-pressure dead-end high-pressure oil will cause a pressure relief moment of liquid explosion, the continuous pressure plunger fluid chamber transient Burst is a stable, high-pitched sound, and every pump has a high or low splash of water. Hydraulic pump manufacturers all over the world adopt various forms of noise reduction units in the pressure transition area of ​​the distribution plate. From the traditional "triangular throttle groove" to "unloading hole", "oblique groove" and other methods, but still not satisfactorily solve the pump output pressure fluctuations caused by fluid noise. For high-pressure pumps with large displacement pressure sudden changes on construction machinery, the liquid explosion noise produced by the pressure relief valve in the dead volume zone is stronger. 2. Cavitation noise When the hydraulic oil contains bubbles, the bubbles with oil is sucked into the cylinder bore, the plunger in the cylinder bore pressure oil into the cylinder with the drain pan window, under the action of these bubbles Will suddenly squeeze rupture, the size of the bubble is almost the same concentration of high pressure oil and then sudden collapse, will form a strong gas burst. Another high-pitched noise produced when the bubble explodes emits a sharp, jarring howl. This sharp, jarring noise varies with the pump pressure. This noise is also highest when the pump output pressure reaches its maximum; as the pressure in the pump drops, the noise declines. Noise generated when the pump sucks in a small amount of air sounds like a rattling, clicking sound, a bit like the sound of bearing damage. When the pump pressure rises to high pressure, it will produce a strange weird bursting noise. 3. Mechanical noise The main part of the mechanical noise emitted by the pump: the coupling of the pump spindle and the engine; If the pump spindle and the engine output shaft is not the heart or the top dead, damaged flexible coupling or loose bolts, will produce mechanical noise. Bearing damage will be issued a continuous "rushing sound", the higher the pump speed the greater the noise, while the pump will appear trembling phenomenon. The mechanical noise of the pump can be heard in the human ear. When the pump runs at low speed, it can be heard in various parts of the pump with an industrial stethoscope or a screwdriver. Sudden noise In the inclined axis pump piston rupture or swash plate plunger sliding off the back plate burst burst of noise is a ring per revolution of the ring loud and clear continuous impact noise Like fireworks. Pump but a sudden noise, pump must be stopped immediately to prevent further expansion of the fault. The most critical is that hydraulic system pressure can not be increased because of the fragmentation of the pump shell pieces of metal slag with the pressure oil into the system, can not be completely removed, will cause lifelong hazards to the hydraulic system. 5. After maintenance noise pump repair noise than before the repair, for the following reasons: (1) If the pump oil hose hardening, installation has been drastically swinging, hose and hard pipe connections will loose leak. (2) If the assembly method is improper, double cylinder pump before and after (or left and right) two cylinder bore symmetry, there will be resonant noise. (3) If the replacement of excessive bearing clearance will produce noise. Pump bearing high level of precision (large bearing capacity), can not use plain bearings. (4) There is a problem with the quality of the replaced parts, and the low precision of parts coordination will produce the resonance frequency of the operating frequency. (5) The pairing of the cylinder body and the counterplate friction pair arc surface bias, there will be excess friction between the friction oil leakage. (6) Oblique shaft pump The new valve plate and the old pump cover variable sliding arc offset, will result in the back of the face plate high pressure port at the back of the pump and the high pressure area between the plane leakage, resulting in air loss noise. The same noise also appears on the back of the new swash plate pump and the backpack compression area of ​​the old pump. 6. Noise after oil change: The new replacement oil in the air is not fully escaped, when the pump suction bubbles at the pump outlet under the action of high pressure, these bubbles will suddenly be compressed rupture caused by gas explosion sound; newly replaced hydraulic oil Poor quality, long storage time, the defoamer oil or oil in a variety of chemical additives adverse reactions, has played a role in the elimination of air in the oil. 7. Progressive noise (1) pump in the long-term use of the process, the noise from small to large. The reason is: the distribution plate and the cylinder with the wear surface, and the distribution plate with the arc cylinder surface with a static pressure oil film balance, if the film contains metal particles will have erosion wear and tear, long-term erosion wear will be in the plate Arc formed on the wear of a certain width of the region, so that the distribution of the inner and outer ring with the arc curve curve Xuan mysterious, leading to leakage from light to heavy, the emergence of throttling noise from small to large. (2) pump suction hose aging, the air hose and hose from the connection was inhaled, the air leak from zero to micro leakage to excess leakage, the pump inhaled air caused by "cavitation" noise with the working hours Extend from small to large. It is a mistake to assume that there is no air infiltration in the pump if it is not leaky. When the pump suction pipe flow rate exceeds the standard (international standards for the steady flow state, the oil rate of 0.5m / s, the absolute pressure of not less than 0.08MPa, in fact, the suction side of the oil pump up to 2m / s, turbulent state ), The absolute pressure on the suction side of the pump will be lower than the atmospheric pressure and a negative value. At this time, there is not enough pressure to accelerate the flow into the rotating components of the pump, which will generate siphon phenomenon, which is fatal to the pump. 8. Cavitation noise pump during operation if the over-flow part of the local area (such as the pump outlet) the absolute pressure of the liquid reduced to the current temperature of the vaporization pressure, the liquid will be vaporized to produce a lot of steam to form bubbles, when containing a lot of bubbles When liquid flows through the high pressure zone outside the cylinder's distribution window, the high pressure liquid drastically reduces the bubble until it suddenly breaks and creates a high temperature. According to statistics, when the bubble is compressed from zero pressure to 20.7MPa, the temperature can be increased to 1149 ℃. High temperature combustion of the oil, generating resinous substances, accelerate the oxidation of oil deterioration. (Editor: Li Juan)