A well known misunderstanding involving Kmf125 Hydraulic Motor Parts is that if the piston seal is leaking, the cylinder will drift. While a leaking piston seal could possibly be the real cause of cylinder drift, the physics involved are often misinterpreted. Fact is, f the piston seal is entirely taken off a double-acting cylinder, the cylinder is filled with oil and also the ports are plugged, the cylinder will hold its load indefinitely, unless the rod-seal leaks.
In this particular condition, because of the unequal volume on both sides in the piston, fluid pressure equalizes and the cylinder becomes hydraulically locked. Once this takes place, the cylinder can move only when fluid escapes through the cylinder via the rod seal or its ports.
Exceptions towards the Rule – The two main exceptions to this particular theory. The first is a double-rod cylinder (Figure 1) where volume is equal for both sides from the piston. The 2nd exception involves a lot hanging on a double-acting cylinder (Figure 2). Within this arrangement, the quantity of pressurized fluid on the rod side may be easily accommodated on the piston side. But since the cylinder drifts, a vacuum will experience on the piston side due to unequal volumes, and depending on the weight of the load, this vacuum may eventually lead to equilibrium that arrests further drift.
This is simply not the end of the cycle, but it’s vital that you at the very least grasp this theory before continuing. Notwithstanding those two exceptions, if a double-acting cylinder’s service ports are blocked by way of a closed-to-actuator spool (Figure 3), and also the piston seal does bypass, pressure will ultimately equalize for both sides of the cylinder. At this time, a hydraulic lock is effected without any further drift can happen, unless fluid is allowed to escape from your cylinder or cylinder circuit.
Lack of Effective Area – As a result of loss in effective area as a result of pressure now acting on the rod-side annulus area, the static pressure within the cylinder must increase to back up the identical load. Remember, force developed by a cylinder is a product of pressure and area. For instance, in the event the load-induced pressure on the piston side in the cylinder was 2,000 PSI and zero on the rod side if the directional control valve closed, assuming no leakage beyond the spool, the equalized pressure might be 3,000 PSI depending on the ratio of the piston and annulus areas.
New call-to-action – Now consider what can happen if the circuit includes a service port relief valve (Figure 4) set at 2,500 PSI. As pressure equalizes over the piston seal as well as the increasing static pressure on the piston side of the Truck Hydraulic Cylinder reaches the cracking pressure from the port relief, however the cylinder will still not retract. A comparable situation can occur in circuits with a load control (counterbalance) valve installed. Within this circuit, shown in Figure 5, the directional control valve has a float center spool (service ports A and B ready to accept tank).
As previously mentioned, in the event the piston seal leaks, unequal volumes of oil on the rod and piston sides from the cylinder indicates hydraulic lock will prevent any noticeable drift. But when again, due to the lack of effective area due to the same pressure now acting on the piston and rod-side annulus areas, the static pressure in the cylinder must increase to support the same load.
The magnitude with this pressure increase depends on the ratio of the cylinder’s piston and annulus areas. If the increase in static pressure exceeds the set maximum load from the counterbalance valve, the valve will open allowing oil from your piston side of the cylinder to flow towards the tank and the cylinder to retract.
Diagnosing Cylinder Drift – Therefore, as the cause from the symptom in both examples is definitely the leaking piston seal, the physics is fundamentally distinct from the typical belief. And in case the idea is understood, a pressure gauge can be quite a useful tool for establishing the reason for cylinder drift. In both of those examples, if the cylinder is drifting there is however no equalization of pressure throughout the piston seal, the directional control valve or load control valve will be the source of rldvub problem.
Exactly what is the maximum pressure range for the application? Keep in mind pressures can vary greatly depending on the specific job the system is performing. Cylinders are rated both for nominal (standard) pressure and test pressure to take into account variations. System pressure must not exceed the nominal rated design pressure of the cylinder.
Push or pull-or both (double acting)? The solution to this inquiry may need Cheap Hydraulic Hose when the hydraulic system is doing “double duty.” (Single-acting cylinders extend the piston under hydraulic pressure; double-acting cylinders extend and retract the piston under pressure.) In a push application, it is very important to size the rod diameter properly to avoid rod buckling. In a pull application, it is essential to size the annulus area (piston diameter area minus the rod diameter area) correctly to move the load in the rated design pressure in the cylinder.
Yongxiang Hydraulic Equipment Co., Ltd locates in Yangzhou, CN, and it covers an area of 143,500 square feet. Winning customer trust with innovation, Yongxiang has been aiming to provide customers with safe and reliable hydraulic products, services, on-time delivery, and customer satisfaction while ensuring employee safety, fostering employee relations and driving efficiency improvements.
Jiangsu Yongxiang Hydraulic Equipment Co. Ltd
Factory: Wujian Industrial Park, Jiangdu District, Yangzhou, CN
Office: 3107# No.2 Building, Global Financial Center, Wenchang East Road, Yangzhou, CN
E-mail: [email protected]