DB/DBW type pilot relief valve is used to control the hydraulic system

DB/DBW type pilot relief valve is used to control the pressure of the hydraulic system. Let's  introduce the solution work principle and troubleshooting detailedly.
1. The structure and working principle
DB type valve is pilot control type overflow valve; DBW type valve is pilot control type electromagnetic overflow valve. DB
Type of valve is used to control hydraulic system pressure; DBW type valve can also control hydraulic system pressure, and can at any time make system unloading.
DB type valve is mainly composed of pilot valve and the main valve composition. DBW type valve is composed by electromagnetic directional valve, pilot valve and the main valve composition.
DB type relief valve:
A cavity pressure oil role in the main valve core (1) of the bottom of at the same time, through the damper (2), (3) and channel (12), (4), (5) role in the main valve core top and pilot valve (7) of the cone valve (6). When the system pressure more than spring (8) setting value, cone valve (6) is opened. At the same time, the main valve core top pressure oil through the damper (3), the channel (5), spring chamber (9) and channel (10) flow back to B cavity (control oil inside exhaust type) or through the outer PaiKou (11) flow back to fuel tank (control oil effluent type). So, when the pressure oil through the damper (2), (3) in the main valve core (1) produced A differential pressure, the main valve core in the differential pressure under the action of open, so that in the setting of work pressure pressure oil from A cavity flow to B cavity (namely unloading).
DBW type electromagnetic relief valve:
This valve working principle and DB type valve the same, just can be installed in a pilot valve electromagnetic directional valve (14) make the system at any moment unloading.
DB/DBW type valve are equipped with control oil internal oil way (12), (4) and internal discharge way (10); Control the oil for the PaiKou mouth X and Y. In this way, can according to control oil supply and discharge of the different forms of combination for within in the row, row, the outside for inside and outside the inside for effluent for effluent 4 types.
2. Relief valve common fault and eliminate
Relief valve in use, common failure have noise, vibration, valve core radial clamping and surge failure, etc.
(a) noise and vibration
Hydraulic device easy to produce noise components generally considered pump and valve, the valve and relief valve and electromagnetic directional valve etc give priority to. There are many factors of produce noise. The noise of the relief valve is the sound velocity and mechanical sound two. The sound of a flow mainly by oil vibration, hole and hydraulic impact, etc of the causes of noise. The sound of a mechanical parts mainly by valve in the impact and friction of the causes of noise.
(1) uneven pressure caused by the noise
The guiding relief valve guide valve part is a YiZhen position as shown in figure 3 shows. In the high pressure cases relief, pilot valve axial open is very small, only 0.003 ~ 0.006 cm. The flow area is small, flow rate is very high, can reach 200 m/s, easy cause uneven distribution of pressure, make the cone valve radial force unbalance and produce vibration. In addition cone valve and cone valve seat processing is generated when ovality, guide valve port of dirt sticking and regulating spring deformation, etc., can also cause cone valve vibration. So generally think that pilot valve occurs noise vibration source site.
Due to the elastic element (spring) and exercise quality (cone valve) existence, form a produce oscillation condition, and guide valve front cavity and a resonant cavity effect, so the cone valve occurred after vibration easy cause the whole valve resonance and making noise, occur more commonly noise with severe pressure to beat.
(2) the hole of the noise
As a result of all sorts of reasons, air is inhaled oil, or in the oil pressure below atmosphere, dissolved in oil parts of the air will precipitation form bubbles, the bubbles in a low pressure area volume is larger, when with the oil to flow to the high, by compression, volume suddenly smaller or bubble disappear; On the other hand, as in the high volume was smaller, and when flow to a low pressure area, volume suddenly increases, the oil bubble volume this rapid change phenomenon. Bubble volume sudden change will produce noise, and because this happens in an instant, will cause the local hydraulic shock and vibration generation. The guiding relief valve guide valve port and the main valve port, fluid velocity and pressure change is very big, is easy to appear cavitation, which produce noise and vibration.
(3) the hydraulic impact of the noise
The guiding relief valve in the unloading, due to hydraulic circuit of pressure drop drastically and produce pressure impact noise. Is the high pressure and large capacity of the working conditions, the impact noise is big, this is because the relief valve unloading time is very short and produced by hydraulic impact in unloading, due to oil flow rate change sharply, causing pressure mutation, the impact of pressure wave. Pressure wave is a small blast, itself of the noise is very small, but along with the oil to the system, if any with a mechanical parts resonance occur, it is possible to increase the vibration and enhance noise. So in case of hydraulic impact noise, more commonly associated with the system vibration.
(4) mechanical noise
The guiding relief valve a mechanical noise, usually from parts of the impact and due to the processing error produces a part of friction.
The guiding relief valve in a noise, sometimes there will be the mechanization of the high frequency vibration sound, generally called it self-excited vibration sound. This is the main valve and guide valve for high frequency vibration and the sound that produce. The incidence of it with oil pipeline configuration, flow, pressure, oil temperature (viscosity), and other factors. Usually, pipe size small, less flow, high pressure, oil viscosity is low, self-excited vibration rate is high.
To decrease or eliminate the guiding relief valve noise and vibration measures, it is to be in commonly pilot valve parts add buy damping element.
Damping set of general fixed in the pilot valve front cavity, namely resonant cavity inside, not free activities. In the damping on the set has all kinds of damping hole, in order to increase the damping to eliminate vibration. In addition, due to the resonance cavity added parts, make resonance cavity volume decreases, and oil in the negative pressure increase when stiffness, according to the stiffness big element is not easy to happen resonance principle, can reduce the possibility of resonance occur.
Damping pad general and resonance cavity activities to cooperate, can free movement. Damping pad of positive and negative have a throttle slot, oil in flow can produce damping effect, to change the original flow situation. Due to the damping pad to join, added a vibration element, and disturbing the original resonance frequency. Resonance cavity increase the damping pad, also reduce the volume, increase the oil pressure of stiffness, in order to reduce the possibility of resonance occur.
In the damping screw up with air holes and throttling edge, air holes for with air, the air pressure in the compression, compressed air can absorb vibration, which is equivalent to a micro vibration absorbers. The pore air compressor, oil filling, expands, oil hydraulic out, thus adding to the an additional flow, to change the original flow situation. It can also reduce or eliminate noise and vibration.
If, in addition, relief valve itself assembly or use improper use, also can cause vibration, produce noise. Such as three concentric type relief valve, assembling with three concentric fit undeserved, when using flow too big or too small, cone valve abnormal wear, etc. In this case, shall carefully check the adjustment, or replacement parts.
(2) the valve core radial lock
Because of the influence of machining accuracy, causing the main valve core radial lock, the main valve opens the pressure or main valve closed don't pressure relief, and the other for pollution radial lock.
(3) surge failure
Relief valve in use can appear sometimes surge failure phenomenon. The guiding relief valve regulating failure phenomenon has two kind of situations: one kind is to adjust pressure regulating the handwheel can't afford to establish pressure, or pressure can not reach the rated value; Another kind of regulating the handwheel pressure don't fall, even constantly booster. Appear surge failure, in addition to the valve core for a variety of reasons cause radial lock outside, still have some of the following reasons:
The first is the main valve body (2) damper jams, hydraulic transmission is less than the main valve cavity and guide valve front cavity, pilot valve will lose to the main valve pressure to adjust action. For the main valve cavity no oil pressure, spring force and is very small, so the main valve becomes a spring force small straight moving type relief valves, in the inlet chamber pressure is very low, the main valve opens overflow, the system can't afford to establish pressure.
Pressure can not reach the rating reason, is the regulating spring deformation or choose mistake, regulating spring compression stroke is not enough, valve internal leakage is too large, or guide valve part of the cone valve excessive wear, etc.
The second is damper (3) jams, hydraulic transmission less than cone valve, pilot valve lost a main valve pressure to adjust action. Damper (holes) blocked, in any pressure cone valve will not open the overflow oil, valve inside always no oil flow, the main valve inferior vena pressure has been equal, the main valve core top circular confined area is greater than the bottom ring confined area, so the main valve is always closed, will not overflow, the main valve pressure increased along with the load. When actuator to stop working, the system pressure will increase infinite. In addition to these reasons beyond, still need to check the external control mouth is blocked, cone valve installation are in good condition, etc.
(4) other fault
Relief valve in assembly or use, the "O" ring, the combination sealing ring damage, or mounting screw, pipe joint looseness of, all may cause undue external leakage.
If the cone valve or the main valve core wear is too large, or seal face bad contact, but also will cause internal leakage is too large, and even affect the normal work.
Electromagnetic relief valve common fault have pilot electromagnetic valve work failure, the main valve regulating failure and unloading the impact of the noise, etc. The latter can add buy by adjusting the buffer to reduce or eliminate. If you don't take buffer, can in the main valve overflow mouth with a back pressure valve. (pressure general adjustment to 5 KGF/cm2 left and right sides, namely 0.5 MPa)
The obove: Hydraulic pump