Analysis and improvement of two hydraulic systems

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Analysis and several improvements of two hydraulic systems of crawler pipe hanger

at present, there are two hydraulic systems used by crawler pipe hanger produced in China. One is multi pump oil supply manual operation hydraulic system (system I), as shown in Figure 1; The other is the single pump oil supply pilot operated hydraulic system (system II), as shown in Figure 2, the input real work can be transmitted to the output without loss

1 function comparison of the two hydraulic systems

① both hydraulic systems have boom limit function. System I adopts the unloading limit of overflow valve (10). When the boom moves to the top dead center, the travel valve (11) is connected, the overflow valve (10) is unloaded, and the boom stops moving. The solenoid valve () is used for oil limit in system 2. When the boom moves to the top dead center, the solenoid valve () is powered on, the oil circuit is connected, the system is depressurized, and the boom movement stops. In contrast, the relief valve unloading limit is better than the solenoid valve oiling limit, because the solenoid valve has a small diameter and weak oiling capacity

② system I adopts double pump oil supply, which can select single pump oil supply or double pump oil supply through multi-channel valve () to realize the high-low transformation of hook working speed according to the heavy load, light load and other working conditions when the pipe hanger is lifting. System 2 uses a single pump for oil supply, so the hook has only one working speed

③ system 1 has no working mechanism locking function, while system 2 has working mechanism locking function. As shown in Figure 2, when the solenoid valve (4- will produce very serious consequences such as blocking the valve hole and scratching the piston surface) is connected, even if the working mechanism is operated, the pipe hanger will not act. If you want to make the working mechanism work, you should first power on the solenoid valve (), disconnect the oil circuit, and then the hydraulic system can boost pressure normally, and the working mechanism can work normally

④ the oil circuit reversing of system 1 is realized by directly manipulating the handle of multi-channel valve, while the oil circuit reversing of system 2 is realized by the output of pressure reducing pilot valves (5, 6, 7). Although such high-yield utilization is also suitable for aircraft manufacturing oil driven hydraulic doru method (4), in contrast, the pilot control is flexible and labor-saving and can realize long-distance control

2 shortcomings of the two hydraulic systems in use

① there is no oil makeup valve at the inlet and outlet of the boom winch motor (,) and hook winch motor (,) of the two systems, which cannot eliminate the cavitation phenomenon generated during the rotation of the motor, which will cause cavitation and noise of the hydraulic system; At the same time, there is no safety valve on their lifting side, which cannot eliminate the overpressure of the hydraulic system, which will cause damage accidents such as hose explosion. What is more serious is that when the lifting torque is close to the braking torque of the hydraulic motor, the lifting pipe will slip hook

② the boom limit mode adopted by system II will cause the hydraulic system to heat up due to the limited oil passing capacity of the solenoid valve ()

③ in system II, once the engine is running, the pilot control oil is in an overflow state, which is not conducive to the work of the pilot pump (13) and the pilot hydraulic system

3 improvement of hydraulic system

in view of the above shortcomings, the hydraulic system is modified as follows. Figure 3 shows the modified single pump oil supply hydraulic system diagram

① according to the mechanical properties of the boom winch data, add oil makeup valves (,,,) on the inlet and outlet sides of the reaction motor () and the hook winch motor (); Safety valves (,) are added at the lifting side, which not only ensures the safety of the pipe crane when lifting heavy objects, but also eliminates the cavitation and noise of the hydraulic system

② connect the travel reversing valve (14) for boom limit with the pilot control oil circuit on the boom reversing valve (). When the boom moves to the top dead center, the travel reversing valve (14) is in the on position, the pilot control oil on the boom reversing valve () is connected with the return oil, the boom reversing valve () returns to the neutral position under the action of spring return force, and the boom movement stops. With this boom limit mode, neither overflow valve, solenoid valve nor too many pipelines are required, and only a very small oil pipe is required, which not only ensures the reliable boom limit, but also does not cause the hydraulic system to heat up

③ for the hydraulic system (system II) with pilot operated hydraulic multi-channel valve, if the working mechanism is not operated for a long time after the pipe hanger is started, the pilot overflow valve (3) will be in the overflow state for a long time, causing the pilot hydraulic oil temperature to be too high, which is detrimental to the work of the pilot hydraulic system. In the improved hydraulic system (Figure 3), a stop valve (12) is added to the remote control port of the pilot overflow valve (). When the working mechanism does not work for a long time, open the stop valve (12) to unload the pilot overflow valve (), which can not only lock the working mechanism, but also avoid the overflow heat of the pilot overflow valve (). When the pipe hanger needs to work, close the stop valve (12), the unloading oil circuit of the pilot overflow valve () is cut off, and the pipe hanger turns into the normal working state

the improved hydraulic system has been applied to SP25Y pipe hanger, and the use effect is good, eliminating the shortcomings of hydraulic system I and II

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