CB series gear pumps are commonly used in agricultural machinery hydraulic system. After a period of gear pump performance, its performance will decline, the survey shows that the main form of gear pump damage is uniform sleeve and gear wear and scratches, the average wear is generally between 0.02-0.50mm, The depth of the mark is usually between 0.05-0.50mm. Due to agricultural time constraints, the urgent need to repair in a short time after damage, but also must take into account the service life of the gear pump after the second life and maintenance costs and maintenance work site operability. This article describes techniques for arc spraying and sticking in quick fixes. Gear pump arc spraying repair technology 1, the principle and characteristics of arc spraying Arc coating technology in the past 20 years in materials, equipment and applications developed rapidly, its working principle is to be two sprayed metal wire as a melting electrode, the motor Variable speed drives, which create a short circuit at the intersection of the gun mouth and cause an arc to melt, are atomized into fine particles with compressed air and sprayed at high velocity onto the pre-treated work surface to form a coating. It is a spray high efficiency, high bonding strength, good coating quality spraying method, with high energy efficiency, equipment investment and low cost, simple equipment, convenient and flexible operation, easy site construction and safety advantages. 2, gear pump arc spray repair process Bushing bore, bushing outer, gear shaft and pump casing uniform wear and scratches between 0.02-0.20mm, should adopt high hardness, and the body with a combination of strong , Good wear resistance arc spray repair process. Arc spraying process: the working surface pretreatment → preheat → spray bonding the bottom → spraying the working layer → cooling → coating processing. Spraying process, the requirements of the workpiece without oil, no rust, surface roughness, preheating temperature is appropriate, the bottom combined with a solid, smooth working layer, the material particles melt-bonded reliable, good wear resistance and corrosion resistance. Spray coating quality and workpieces surface treatment and spraying process has a great relationship, therefore, choose the appropriate surface treatment and spraying process is very important. In addition, the spraying and spraying process should be thin metal or copper skin adjacent to the coated surface of the non-sprayed part of the bundle ⑴ workpiece surface pretreatment coating and the basic bonding strength and the substrate cleanliness and roughness related. Before spraying, the basic surface cleaning, degreasing and surface roughening and other pretreatment is an important process spraying process. The first part of the spray should be sprayed with gasoline, acetone degreasing treatment, with a file, fine sandpaper, whetstone will remove the fatigue layer and the oxide layer, exposing the metal color. Then roughening treatment, roughening treatment can provide surface compressive stress, increase the bonding area and clean the surface of the coating and the substrate, reduce the stress when cooling the coating, ease the internal stress of the coating, it is conducive to the increase of adhesion . Sandblasting is the most commonly used roughening process, sand to sharp, hard as well, the choice of quartz sand, emery and so on. Rough fresh surface easily oxidized or polluted by the environment, it should be timely spraying, if placed more than 4h will be re-roughened. ⑵ surface preheat treatment The temperature difference between the coating and the substrate surface will produce shrinkage stress coating, causing the coating cracking and peeling. Preheating of the substrate surface can reduce and prevent the above adverse effects. But the preheating temperature should not be too high, so as not to cause the substrate surface oxidation and affect the bonding strength of the coating and the substrate surface. Preheat temperature is generally 80-90 ℃, commonly used to complete the neutral flame. $$ Div $$ Bonded Backing Pre-sprayed with a thin layer of metal prior to application of the working coating provides a clean, roughened surface for the subsequent coating to improve the bond strength and shear strength between the coating and the substrate. Bottom bonding materials generally use ferrochrome nickel alloy. The main principle of choosing the spraying process parameters is to increase the bonding strength between the coating and the substrate. Spray gun and the workpiece during the relative movement speed is greater than the flame moving speed, the speed of the size of the coating thickness, spray wire feeding speed, arc power and other parameters determined jointly. Spray gun and the surface of the workpiece is generally about 150mm. Other specifications for arc spraying are determined by the characteristics of the coating equipment and the coating material. ⑷ spraying working layer should be first wire brush to remove the adhesion of the bottom surface of the sediment, and then immediately spray coating. Materials for the carbon steel and low alloy wire, the coating has a higher wear resistance, and lower prices. Spray coating thickness should be based on the amount of wear and tear of the workpiece, machining allowance and other relevant factors (diameter shrinkage, clamping deviation, spray coating diameter uneven amount, etc.) to determine. ⑸ cooling spray temperature after the workpiece is not high, the general can be directly air-cooled. ⑹ spray coating processing machinery processing to the required size of the drawings and the provisions of the surface roughness. Gear pump sticky surface repair technology 1, surface sticky coating principle and characteristics In recent years, surface sticky coating technology in China's equipment maintenance has been widely used for a variety of materials, parts and equipment repair. Its working principle is to add molybdenum disulfide, metal powder, ceramic powder and fiber and other special filler adhesive, directly applied to the surface of materials or parts, so that it has a wear-resistant, corrosion and other functions, mainly for surface strengthening and repair . Its process is simple, convenient and flexible, safe and reliable, does not require specialized equipment, just a good glue coated on the surface of the cleaned parts to be cured after curing can often operate at room temperature, will not make the parts Produce thermal equivalent effect and deformation. 2, sticky coating coating process Cylindrical sleeve, sleeve end face fit, gear end face or pump housing bore small area uniformity of wear between 0.15-0.50mm, scratch depth of 0.2mm or more When, should use sticky coating repair process. Adhesion coating coating process: initial cleaning → pre-processing → final cleaning and activation → preparation of repair agent → coating → curing → finishing, cleaning or post-processing. Although the sticky coating process is relatively simple, but the actual construction requirements are quite strict, just choose a good adhesive, not necessarily able to obtain high viscosity strength. It is necessary to choose the right adhesive, but also strictly in accordance with the correct process of adhesive coating the right adhesive, but also strictly in accordance with the correct process of law line viscosity coating in order to obtain a satisfactory effect. $$ Div $$ ⑴ clean the surface of the first parts must not have grease, water, rust, dust and so on. Wash with gasoline, diesel or kerosene first, then acetone. ⑵ pre-processing fine sandpaper into a certain trench mesh, exposing the base color. ⑶ final cleaning and activation treatment with acetone or special cleaning agent. Then sandblasting, flame or chemical treatment to improve the surface activity. ⑷ preparation repair agent repair agent in use should be strictly in accordance with the provisions of the ratio of the agent (A) and curing agent (B) fully mixed to the same color as well, and within the prescribed time, run with the use. ⑸ coated with the first repair agent in the repair surface coating a thin layer, repeated scratching and parts fully infiltrated, and then evenly coated to the specified size, leaving a finishing allowance. As much as possible in the coating to move in one direction, the reciprocating coating will wrap the air in the gel to form bubbles or pores. ⑹ curing coated with a release agent in the steel pressure in the work, the general room temperature curing takes 24 hours, heating curing (about 80 ℃) required 2-3 hours. ⑺ finishing, cleaning or post-processing fine boring or with a file, fine sandpaper, whetstone will be finishing surface finishing to the required size.
Check Valves
A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball check Valves, the ball is spring-loaded to help keep it shut. For those designs without a spring, reverse flow is required to move the ball toward the seat and create a seal. The interior surface of the main seats of ball check valves are more or less conically-tapered to guide the ball into the seat and form a positive seal when stopping reverse flow.
Ball check valves are often very small, simple, and cheap. They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. Although the balls are most often made of metal, they can be made of other materials, or in some specialized cases out of artificial ruby. High pressure HPLC pumps and similar applications commonly use small inlet and outlet ball check valves with both balls and seats made of artificial ruby, for both hardness and chemical resistance. After prolonged use, such check valves can eventually wear out or the seat can develop a crack, requiring replacement. Therefore, such valves are made to be replaceable, sometimes placed in a small plastic body tightly-fitted inside a metal fitting which can withstand high pressure and which is screwed into the pump head.
There are similar check valves where the disc is not a ball, but some other shape, such as a poppet energized by a spring. Ball check valves should not be confused with Ball Valves, which is a different type of valve in which a ball acts as a controllable rotor to stop or direct flow.
A diaphragm check valve uses a flexing rubber diaphragm positioned to create a normally-closed valve. Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. Once positive pressure stops, the diaphragm automatically flexes back to its original closed position.
A swing check valve or tilting disc check valve is check valve in which the disc, the movable part to block the flow, swings on a hinge or trunnion, either onto the seat to block reverse flow or off the seat to allow forward flow. The seat opening cross-section may be perpendicular to the centerline between the two ports or at an angle. Although swing check valves can come in various sizes, large check valves are often swing check valves. The flapper valve in a flush-toilet mechanism is an example of this type of valve. Tank pressure holding it closed is overcome by manual lift of the flapper. It then remains open until the tank Drains and the flapper falls due to gravity. Another variation of this mechanism is the clapper valve, used in applications such firefighting and fire life safety systems. A hinged gate only remains open in the inflowing direction. The clapper valve often also has a spring that keeps the gate shut when there is no forward pressure. Another example is the backwater valve (for sanitary drainage system) that protects against flooding caused by return flow of sewage waters. Such risk occurs most often in sanitary drainage systems connected to combined sewerage systems and in rainwater drainage systems. It may be caused by intense rainfall, thaw or flood.
A stop-check valve is a check valve with override control to stop flow regardless of flow direction or pressure. In addition to closing in response to backflow or insufficient forward pressure (normal check-valve behavior), it can also be deliberately shut by an external mechanism, thereby preventing any flow regardless of forward pressure.
A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
An in-line check valve is a check valve similar to the lift check valve. However, this valve generally has a spring that will 'lift' when there is pressure on the upstream side of the valve. The pressure needed on the upstream side of the valve to overcome the spring tension is called the 'cracking pressure'. When the pressure going through the valve goes below the cracking pressure, the spring will close the valve to prevent back-flow in the process.
A duckbill valve is a check valve in which flow proceeds through a soft tube that protrudes into the downstream side. Back-pressure collapses this tube, cutting off flow.
A pneumatic non-return valve.
Multiple check valves can be connected in series. For example, a double check valve is often used as a backflow prevention device to keep potentially contaminated water from siphoning back into municipal water supply lines. There are also double ball check valves in which there are two ball/seat combinations sequentially in the same body to ensure positive leak-tight shutoff when blocking reverse flow; and piston check valves, wafer check valves, and ball-and-cone check valves.
Check Valves, Water Check Valves, Brass Check Valves, Sanitary Check Valves
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