29 results about "Pressure buildup" patented technology

The invention discloses a while-drilling pressure measurement fluidity correction method under a multi-factor interaction effect, and the method comprises the steps: constructing a while-drilling pressure measurement numerical simulation model of an anisotropic stratum inclined shaft, and deducing the model as a while-drilling pressure measurement finite element model of the stratum inclined shaft; performing stratum fluidity inversion analysis on the stratum inclined shaft pressure measurement while drilling finite element model, and identifying key factors influencing the logging pressure measurement while drilling fluidity based on an analysis result; carrying out numerical simulation on the basis of the identified key factors to obtain a pressure response result of the pressure measurement while drilling, analyzing formation fluidity characteristics under the interaction of the multiple factors, and further determining a fluidity response rule expression of the pressure measurement while drilling under the interaction of the multiple factors; and substituting key factor values in the actual measurement while drilling pressure measurement process into the corresponding while drilling pressure measurement fluidity response rule expression, and further calculating to obtain the while drilling pressure measurement fluidity of the vertical well, thereby realizing the correction of the while drilling pressure measurement fluidity. The method provided by the invention provides a theoretical basis and a technical support for the use of the pressure measuring instrument while drilling.

The invention provides a transient productivity prediction method based on a fracture-vug reservoir pressure recovery well test model, and relates to the technical field of oil and gas reservoir development. The prediction method comprises the following steps: S1, through fracture-vuggy reservoir pressure recovery well test interpretation, establishing a fracture-vuggy reservoir well test geologic model, and obtaining reservoir parameters; s2, establishing a bottom hole pressure calculation equation under a constant flow condition, and calculating bottom hole pressure by adopting a multi-stage flow superposition principle; s3, establishing a yield calculation equation under the condition of the fixed bottom hole pressure to obtain data of flow changing along with time under the fixed bottom hole flow pressure; s4, forming a productivity prediction method that both the yield and the bottom hole pressure change along with well testing, and establishing a productivity calculation equation of the yield and the pressure when both the pressure and the flow change based on a Duhanm principle to realize transient productivity calculation prediction; therefore, a new productivity prediction method suitable for the fracture-cavity type oil reservoir is formed. The long-term production pressure and yield change of the oil well can be predicted more accurately, and development and production allocation are guided.

This application relates to a hydraulically controlled water supply on / off device and its control method. The device includes a pressure reducing valve, a pilot valve, and a solenoid valve. The solenoid valve is disposed on the connecting pipeline between the outlet side of the pilot valve and the outlet side of the pressure reducing valve. When the solenoid valve is open, the valve plate of the pressure reducing valve separates from the valve body under the pressure of the water at the inlet side of the pressure reducing valve, and the pressure reducing valve opens. When the solenoid valve is closed, the pilot valve controls the valve plate of the pressure reducing valve to move downward, and the pressure reducing valve closes. This device controls the opening and closing of the solenoid valve by receiving the unit's operating status signal to isolate or open the pilot valve channel, thereby automatically controlling the opening and closing of the pressure reducing valve using hydraulic action. This achieves reliable on / off control of the technical water supply system, effectively avoiding the opening and closing failures caused by pressure buildup in traditional electric isolation valves. Furthermore, by replacing the high-energy-consuming electric valve with a low-power solenoid valve, the system's energy consumption is significantly reduced.

The invention discloses an integrated braking system and a detection method. The integrated braking system comprises a liquid storage pot; the liquid storage pot is connected with the pedal simulation unit and the pressurizing unit, and the pedal simulation unit is connected with the braking unit through a first hydraulic loop and performs hydraulic braking control on the braking unit; the pressurizing unit is connected with the first hydraulic loop through a second hydraulic loop and is used for loop detection; the first hydraulic loop and the second hydraulic loop which are connected through the pedal simulation unit and the pressurization unit are used for detecting the hydraulic loop of the integrated braking system, whether the pressure buildup capacity, the air amount and the sealing performance of the integrated braking system meet preset threshold values or not is judged, a vehicle with problems can be detected in a whole vehicle manufacturing plant, and the integrated braking system can also be used for an after-sale maintenance end. And detecting the brake system after the brake system is maintained.

The first aspect of this application provides a distribution plate, including a mixing chamber, a first inner hole, and a second inner hole. The mixing chamber is disposed within the distribution plate and is used to provide mixing space for an accelerator and compressed air. The first inner hole communicates with the mixing chamber and is used to deliver compressed air into the mixing chamber. There are three second inner holes, one of which is used to deliver the accelerator to the mixing chamber, and the other two are used to connect the mixing chamber to a mixer. The inner diameter of the mixing chamber is larger than the inner diameters of the first and second inner holes. The large space of the mixing chamber provides sufficient mixing space for the compressed air and the accelerator, allowing them to mix thoroughly, reducing the probability of pressure buildup, and thus ensuring the uniformity of the mixing medium and concrete. This ensures the continuity and stability of the concrete head sprayed by the wet shotcrete machine, thereby reducing the concrete drop rate and rebound rate. The second aspect provides a wet shotcrete machine that includes the distribution plate of the first aspect.

The invention discloses a braking system of a vehicle and the vehicle, and relates to the field of vehicles, a main braking unit comprises a first control valve, a second control valve, a first driving part and a pressurizing part, and a redundant braking unit comprises a third control valve, a fourth control valve, a second driving part and a liquid pumping part; the pressurizing piece, the first control valve and the third control valve are sequentially connected to form a first oil way, and the first driving piece is configured to press oil in the first oil way into the wheel brake; the liquid storage container, the second control valve and the fourth control valve are sequentially connected to form a second oil way, the liquid pumping part is arranged on the second oil way, and the second driving part is configured to pump oil in the liquid storage container into the wheel brake. Therefore, by selectively conducting one of the first oil way and the second oil way, decoupling of the main braking unit and the redundant braking unit can be achieved, the pressure buildup response speed of the main braking unit and the redundant braking unit is increased, and improvement of the braking performance of the vehicle and the driving safety of the vehicle is facilitated.

The invention provides a rock fracture permeability calculation method and device, electronic equipment and a storage medium, and belongs to the technical field of oil-gas exploration and development. The method comprises the steps that the rock fracture average opening degree of a target interval is calculated according to imaging logging interpretation; analyzing and calculating the dynamic rock fracture opening degree of the target interval according to the pressure recovery well test; calculating a crack opening correction coefficient according to the rock crack average opening and the dynamic rock crack opening; and calculating the rock fracture permeability according to the fracture opening correction coefficient and the rock fracture density. According to the method, dynamic and static data such as imaging logging, pressure recovery well testing and testing are integrated, the crack opening correction coefficient is introduced, the rock crack permeability is calculated, and the rock crack permeability can be obtained more accurately.

This utility model provides a splash-proof and corrosion-resistant drying oven, including a drying chamber with a component chamber inside. A cover plate is fixedly installed at the top of the drying chamber. A material corrosion-resistant tank is located inside the component chamber, and a connecting pipe is installed at the top of the material corrosion-resistant tank, extending upwards and penetrating the cover plate. This design utilizes a tapered input cavity with a gradually decreasing cross-sectional area to increase the material flow rate and create a negative pressure zone, suppressing pressure buildup. The symmetrically arranged exhaust pipes on both sides can directionally discharge the overpressure steam generated by material vaporization, preventing excessive pressure from causing material to splash from the input port. Furthermore, the material corrosion-resistant tank is made of 316L stainless steel or titanium alloy and undergoes electrolytic polishing to eliminate microporous corrosion sources on the inner wall, significantly improving its resistance to corrosive materials and extending the equipment's service life.

The invention provides a compressed air energy storage container pressure buildup stage model building and simulation method and system, and the method comprises the steps: dividing an energy storage process into an initial pressure buildup stage, an initial pressure buildup stage and an air compressor pressure supplement stage after multiple cycles; a steam-water mixing container and a high-pressure gas storage container are divided into four parts, namely a gas control body, a liquid control body, a device wall control body in contact with gas and a device wall control body in contact with liquid, and six assumptions are combined; mathematical models (including a gas state equation, a water body control body energy equation, a device wall control body energy equation and the like) of all stages are established on the basis of the law of conservation of energy and the law of conservation of mass respectively, curves of pressure and liquid level changing along with time are obtained through simulation calculation, and the curves are compared with experimental results for verification. According to the method, the multi-physical field coupling effect is comprehensively considered, the dynamic characteristics of the gas storage container can be accurately reflected, and a reliable theoretical basis is provided for system design and engineering application.

The utility model provides a wellhead blowout preventer pressure testing device which comprises a pressure testing device body, a pressure testing channel and a pressure releasing channel which are not communicated with each other are defined in the pressure testing device body, the pressure testing device body is provided with a pressure testing connector installation part and a pressure releasing connector installation part, and an inlet channel is arranged in the pressure testing connector installation part. A side wall through hole is formed in the side wall of the pressure testing device body, the pressure testing channel is communicated with the inlet channel and the side wall through hole, and the pressure releasing channel is communicated with a pressure space in an original well pipe column well. The contact sleeve sleeves the outer wall surface of the pressure testing device body and is used for being in sealed connection with a semi-sealed flashboard of the blowout preventer; the pressure test inlet joint is arranged on the pressure test joint mounting part and is used for connecting a pressure test pump; and the pressure release joint is arranged on the pressure release joint mounting part. The blowout preventer pressure test device can perform pressure test operation on the blowout preventer in the workover operation, and can release the pressure in the well in the pressure test process, so that pressure accumulation is avoided, and the safety of the workover operation is improved.

We propose a rust-preventive cover for outdoor tanks equipped with vent pipes, to prevent rust from occurring at the vent pipe mounting area due to rainwater. [Solution] A rust-preventive cover for a vent pipe mounting portion, characterized in that it is made of resin, for covering the vent pipe mounting portion, which is the part where the vent pipe is attached to the boss, in order to prevent pressure buildup inside the outdoor tank used outdoors at normal pressure, the boss attached to the vent pipe, and the vent pipe mounting portion attached to the boss, in order to prevent rust from occurring at the vent pipe mounting portion.

The device comprises a hot melting metal packer connected between adjacent sleeves, the hot melting metal packer comprises a hot melting metal cylinder, the annular area of the hot melting metal cylinder is provided with a circulation hole used for allowing fluid to pass through, and the annular area of the hot melting metal cylinder is provided with a circulation hole used for allowing fluid to pass through. The hot melting metal cylinder is used for being heated and melted into fluid, filling the fluid into a to-be-sealed area and conducting sealing through volume expansion in the curing process. According to the device, potential gas migration and annulus pressure can be prevented, and the effectiveness of cement sheath sealing can be ensured on the basis that well repairing or cement squeezing operation is not needed in the oil and gas well production process. The invention further discloses a method for preventing and controlling annulus pressure of the oil and gas well. The method has the same advantages.

The invention provides a compressed air energy storage container pressure building and energy storage stage model building and simulation method, and aims at solving the problems that in the prior art, multi-physics field coupling is ignored, and dynamic characteristic analysis is insufficient. According to the method, the energy storage process is divided into an initial pressure buildup stage and an energy storage stage, aiming at the initial pressure buildup stage and the energy storage stage, an energy storage container and an acting container are divided into a gas control body, a liquid control body, a device wall control body in contact with gas and a device wall control body in contact with liquid, and six assumptions are combined, so that the energy storage process is optimized. Mathematical models (including a gas state equation, a water body control body energy equation, a device wall control body energy equation and the like) of all stages are established on the basis of the law of conservation of energy and the law of conservation of mass respectively, curves of pressure and liquid level changing along with time are obtained through simulation calculation, and the curves are compared with experimental results for verification. According to the method, the multi-physical field coupling effect is comprehensively considered, the dynamic characteristics of the gas storage container can be accurately reflected, and a reliable theoretical basis is provided for system design and engineering application.

This utility model relates to the field of motor manufacturing technology, specifically an explosion-proof NMP recovery emergency pressure relief device, comprising an outer protective shell, a storage tank, and a telescopic rod. Pressure gauges and vent pipes are respectively installed on both sides of the outer protective shell. A flange and a switch valve are provided on one side of the vent pipe. A discharge valve is installed on one side of the outer protective shell corresponding to the bottom of the pressure gauge via a pre-drilled port and bolts. A control panel is located on the front of the outer protective shell, and a support frame is located at the bottom of the outer protective shell. The control panel moves the telescopic rod and piston upwards to above the connection point between the exhaust pipe inlet and the pressure relief pipe, allowing the pressure inside the storage tank to be released into the exhaust pipe, preventing excessive pressure buildup inside the storage tank and potential damage. An activated carbon filter purifies and filters harmful substances or odors in the exhaust gas, and the filtered gas is then discharged, improving environmental friendliness.

A hydraulic leakage diagnosis method and system for a full-active suspension system belong to the technical field of automobile chassis control, and comprise the following steps: respectively carrying out leakage diagnosis on pipeline leakage, energy accumulator leakage, electromagnetic valve leakage, motor pump leakage and shock absorber piston leakage, and carrying out diagnosis by using the pressure, height and acceleration sensor data of the full-active suspension system; and hardware cost does not need to be increased. Comparing the reference pressure before starting with the actual pressure root-mean-square value for pipeline leakage; energy accumulator leakage is based on cavitation phenomenon times and pressure buildup capability; the electromagnetic valve leakage is based on a P-Q characteristic curve; motor pump leakage is based on rotating speed difference; shock absorber piston leakage is based on flow differences. Introducing a temperature compensation mechanism to correct pressure characteristics, and recording initial pressure data as a reference; early warning and accurate grading of leakage of the hydraulic system are achieved, diagnosis accuracy and reliability are improved, and the false alarm rate is reduced.

The invention discloses a fault diagnosis method and system for a power-assisted pressure buildup loop of a brake control system. The diagnosis method comprises the steps that brake working condition parameters are obtained; on the basis of the obtained brake working condition parameters, a self-inspection liquid drainage process is judged and executed to empty brake liquid; executing a self-inspection pressure buildup process and a self-inspection back-suction process to actively create a back-suction working condition and obtain an evaluated air content, and judging the working state of a power-assisted pressure buildup loop; the diagnosis system comprises a simulation main cylinder loop composed of a liquid storage pot, a first isolation valve, a simulation main cylinder, a first pressure sensor, a second isolation valve, a third isolation valve and a pedal simulator. And the power-assisted pressure buildup loop consists of a liquid inlet valve, a liquid outlet valve, a fourth isolating valve, a pressure buildup main cylinder, a liquid supplementing valve and a second pressure sensor. When the liquid supplementing valve cannot be closed after being opened and the liquid storage pot lacks brake liquid, the problem that the power assisting performance is reduced when the whole vehicle cannot assist or mechanical backup occurs can be avoided, and the driving safety of a driver is effectively guaranteed.

This application relates to a self-locking ball stop valve, comprising a valve body, an inlet connector disposed on the valve body, a rotating shaft cavity formed within the valve body, and a valve core disposed within the rotating shaft cavity for controlling the opening and closing of the inlet connector; a valve seat disposed within the rotating shaft cavity, the valve core rotating and being limited on the valve seat; a pressure relief groove disposed on the outer circumferential surface of the valve seat, and a pressure relief hole disposed on the inlet connector, one end of the pressure relief hole communicating with the interior of the inlet connector, and the other end of the pressure relief hole communicating with the pressure relief groove. This application has the effect of reducing the aging and fatigue rate of sealing components, effectively mitigating the adverse effects of pressure buildup on sealing components, extending service life, and improving safety.

An electronic brake system, comprising a valve body (10), a pressure buildup unit (20), a pedal input unit (30), a pedal feeling simulation unit (40), a control unit (50), a liquid storage tank (60), a pedal position sensor (70), an electromagnetic valve (80), and a pressure sensor (90). The liquid storage tank (60) is mounted on the top of the valve body (10); the pressure buildup unit (20) and the control unit (50) are respectively mounted on two side surfaces of the valve body (10); the pedal input unit (30) is mounted on one end surface of the valve body (10); the pedal feeling simulation unit (40) and the pedal position sensor (70) are both mounted on the same side as the control unit (50); the control unit (50) is in electrical signal connection with the pressure buildup unit (20) and the pedal position sensor (70); the electromagnetic valve (80) and the pressure sensor (90) are arranged on the valve body (10); and the electromagnetic valve (80) is connected to the pressure sensor (90), the pressure buildup unit (20), the pedal input unit (30), the pedal feeling simulation unit (40), and the liquid storage tank (60) by means of a hydraulic circuit in the valve body (10). The electronic brake system can implement decoupling between a pedal and a booster mechanism, has low noise and a high response speed, has a vehicle body stability control function, can implement braking by means of a mechanical device when an electronic control system fails, and has a small size and a high degree of integration.

A fast fill system is provided. The fast fill system includes first and second high flow roll-over valves, each coupled to flexible tubes. The system includes a replacement fuel tank with first and second inserts on top. The high flow roll-over valves couple to the replacement fuel tank through the respective inserts. The valves with flexible tubes allow the replacement fuel tank to expel up to 400% more air when refueling than without them. This enables filling by high-flow truck stop pumps at rates of 25+ gallons per minute without pressure buildup or spillage.

This invention relates to the field of concrete mixing plant technology and discloses a concrete mixing device with a dust collection structure, comprising: a mixing tank, in which a mixing rod is rotatably installed, the mixing rod being driven to rotate by a servo motor fixedly installed on the top of the mixing tank, the servo motor being connected to a controller, and a cartridge dust collector being provided on one side of the mixing tank. This invention utilizes the filter screen at the bottom of the dust discharge pipe to achieve dust classification and interception, intercepting large particles of powder and returning them to the mixing tank for reuse, reducing the loss of effective powder from the source. When the filter screen is clogged, the pipeline wind resistance increases, and the negative pressure suction drives the sleeve and filter screen to rise. The controller drives the drive component to push the vibrating motor against the sleeve, and the accumulated dust falls off and falls back through resonance, achieving real-time self-cleaning, avoiding the problem of delayed dust cleaning, eliminating the hidden dangers of pipeline pressure buildup and dust collection failure, and the vibrating motor does not directly contact the filter material, avoiding damage and deformation of the filter material.

The invention discloses multifunctional intelligent dynamic carbon removal equipment and a cleaning method thereof, and relates to the technical field of automobile engine maintenance equipment.The multifunctional intelligent dynamic carbon removal equipment comprises an ECU controller, the ECU controller is installed in a main body case, and a built-in buzzer and a built-in indicator light are integrally installed on one side of the interior of the main body case; the built-in indicator lamp is arranged on one side of the built-in buzzer, the oil way liquid storage tank is installed on one side of the main machine box, the air inlet liquid storage tank is installed on one side of the oil way liquid storage tank, and the pulse cup is installed on one side of the air inlet liquid storage tank. Carbon deposits at multiple parts of an engine fuel system, an air inlet system and a combustion chamber are intelligently and dynamically cleaned, an original vehicle fuel pipeline does not need to be cut off or blocked, oil pump insurance does not need to be pulled out, oil pump damage caused by pressure building is not needed, and continuous operation without flameout of an engine is achieved by adopting a serial oil way connecting device and an online mixing technology; and an original vehicle oil way is always kept smooth in the cleaning process.

The present application discloses a POCT hematology analyzer and a hematology analysis method. In the POCT hematology analyzer, a pressure buildup mechanism performs pressure detection on a test chamber during testing of a reagent cartridge; a processor determines, on the basis of the pressure detection result from the pressure buildup mechanism, whether the gas tightness of the test chamber is abnormal. Thus, the reagent cartridge can be processed in a timely manner when the gas tightness of the test chamber is abnormal, thereby reducing damage to the POCT hematology analyzer caused by problems such as gas leakage or port blockage of the reagent cartridge, and improving the test accuracy and reliability of the POCT hematology analyzer.

The application belongs to the field of petroleum industry devices, and discloses a low-voltage intelligent control device for controlling layer-by-layer emptying of residual liquid and collecting liquid samples based on downhole electric control. The device is composed of a sampling module, an electric control module and a liquid discharge module. The device can quickly realize rapid discharge of residual liquid between two seals and rapid pressure drop between the two seals by controlling the opening of the liquid discharge channel on the ground. The device is of great significance for data collection in the initial stage of pressure buildup testing. Compared with the traditional electric control liquid discharge pump and electric control sampler, the device is simple to operate, and the safety performance and reliability are doubled.

This invention discloses a directional and horizontal well extension tool, comprising a housing, an impeller rotatably connected inside the housing, a turntable connected above the impeller, a rack eccentrically connected to the turntable, the rack meshing with a gear, a steering gear connected below the gear via a gear shaft, a driving wheel connected to the bottom surface of the steering gear, and the axis of the driving wheel being offset from the axis of the gear; a driven wheel is connected to the lower rear of the housing. The driving principle of this invention is based on the centrifugal force law and the curvilinear force law. The driving wheel oscillates periodically, and the frictional force between the bottom wall and the edge of the driving wheel generates a forward propulsion effect. The alternating lateral component of the frictional force gives the extension tool a unique serpentine movement, thereby solving the technical problems of high drill string friction, severe pressure buildup, and low mechanical drilling speed in directional and horizontal wells.

The present disclosure relates to a technical field of analysis, and provides a flash evaporator and a gas chromatograph including the flash evaporator, which can avoid pressure buildup of a sample after vaporization and completely vaporize a sample by a heating module. The flash evaporator is applied to sample pretreatment of a gas chromatograph. The flash evaporator includes a sample inlet, a gas sample outlet, a heating module, and a flow restriction device. The heating module communicates with the sample inlet and the gas sample outlet, performs flash evaporation on a liquid sample entering the sample inlet to obtain a gas sample, and delivers the gas sample to the gas chromatograph through the gas sample outlet. In particular, the flash evaporator also includes the flow restriction device disposed in a pipeline between the heating module and the sample inlet.

This invention relates to a venting device for a fuel tank, comprising: a venting pipe having a port section extending toward the upper wall of the fuel tank; a floating venting member having a through hole, disposed around the port section and floating along the port section in response to changes in the fuel level in the fuel tank; and a limiting structure disposed at the port section and housed between an upper stop and a lower stop of the floating venting member. When the fuel level in the fuel tank decreases to the lower limit position of the floating venting member, the limiting structure contacts the upper stop; when the fuel level increases to the upper limit position of the floating venting member, the limiting structure contacts the lower stop. This increases the height preventing fuel from overflowing into the venting pipe, prolongs the venting time of the fuel tank, and also preserves the fuel flow capacity of the venting pipe, effectively preventing fuel tank pressure buildup. This invention also provides a fuel tank for an aircraft, which may include the venting device described above.

The invention relates to the technical field of simulation test devices, in particular to a test device and method for simulating pressure accumulation and discharge of deep brine, and the test device for simulating pressure accumulation and discharge of deep brine comprises a test box body and a crack simulation assembly arranged in the test box body, the crack simulation assembly comprises a base, an actuating part and a plurality of simulation strips; a pore pressure cavity with an opening in the bottom is formed in the simulation strip, and the pore pressure cavity is communicated with the interior of the test box body; the actuating part is arranged on the base, is connected with the simulation strips and is used for driving the simulation strips to move on the base so as to change the width of a crack between every two adjacent simulation strips; the technical limitation that an existing test device is single and isolated in function, and cannot simulate a lateral water replenishing, internal gas production and upper salt plugging coupling mechanism, so that the whole process of pressure accumulation and pulse type discharge disasters cannot be truly represented is solved.

This invention discloses a phosphoric acid purification device, relating to the field of waste gas treatment technology. It includes: a purification tower and multiple sets of spray structures disposed inside the purification tower; a control auxiliary device, located inside the purification tower, used to adjust the spray space of each set of spray structures to adapt to different air intake volumes. The control auxiliary device includes multiple support plates disposed inside the purification tower. This invention utilizes layered pressure sensors and PLC closed-loop control to drive a variable-pitch screw to move the support plates of each layer when the air pressure inside the purification tower increases sharply, achieving differentiated lifting and lowering with maximum displacement at the bottom layer and progressively decreasing displacement upwards. This not only extends the residence time of waste gas by expanding the bottom layer to ensure the purification efficiency of characteristic pollutants such as fluorides and reduces the pressure drop inside the tower to eliminate safety faults caused by pressure buildup, but also maintains a stable gas-liquid contact environment through small-scale adjustments at the upper layers, ensuring the consistency of purification efficiency and operational stability of the entire tower.

To provide a control valve unit that can prevent pressure buildup in the oil passage upstream of the check valve when the control valve is operated to the neutral position, while also preventing the actuator, which is stopped in the neutral position, from operating against the user's intention. [Solution] The control valve unit 2 includes a pump oil passage 41, a first control valve 31, a second control valve 32, a first oil passage 42 connecting the first control valve 31 and the first actuator 61, a second oil passage 43 connecting the second control valve 32 and the second actuator 62, a pilot-operated first check valve 33, a pilot-operated second check valve 34, a tank oil passage 44 connected to the tank port 22, and pilot oil passages 45, 461, and 471 through which pilot hydraulic fluid flows. The pilot oil passages 45, 461, and 471 are not connected to the tank oil passage 44 and are not in communication with the tank port 22.