A protection system for a single-screw pump to prevent high and low pressure operation and dry friction

Abstract

The present invention relates to a single screw pump high and low pressure operation and dry friction protection system, including a single screw pump and a solenoid valve of the single screw pump, and also including a pressure monitoring device and an electrical control box; the pressure monitoring device is installed at the outlet of the single screw pump and connected to the electrical control box; the pressure monitoring device is provided with a pressure switch and a pressure gauge, the pressure gauge monitors the outlet pressure of the single screw pump, and the pressure switch is triggered to open / close according to the value of the pressure gauge; the pressure switch includes a low pressure pressure switch and a high pressure pressure switch; the trigger pressure of the low pressure pressure switch is P1, and the trigger pressure of the high pressure pressure switch is P2; the electrical control box is provided with a solenoid valve control switch, and the control switch is connected to the low pressure pressure switch and the high pressure pressure switch. The system of the present invention can effectively prevent the occurrence of dry friction of the single screw pump during the startup stage and normal operation, and improve the reliability of the operation of the ship engine system.

Description

Technical Field

[0001] The invention belongs to the technical field of shipbuilding, and in particular relates to a single screw pump high and low pressure operation prevention and dry friction protection system. Background Art

[0002] In the ship engine system, the engine room often produces some oily sewage and accumulates in the bilge water tank. The diesel engine discharges waste oil and the oil residue separated by the oil separator often accumulates in the oil residue tank. These sewage and oil residue often contain solid particle impurities and are not suitable for gear pumps and multi-screw pumps. Single screw pumps are often used to transfer this type of oily sewage and oil residue to the incinerator system or discharge to the shore. In the ship engine room structure, the oily sewage tank and the oil residue tank are generally arranged at the bottom of the engine room, and the single screw pump is usually installed on the top of these compartments for operation.

[0003] When the single screw pump is working, the screw rotor and the rubber stator directly rub against each other to form a closed space to pump liquid. In order to prevent the rubber from decomposing and deteriorating due to high temperature, the single screw pump needs liquid to cool and lubricate when working. The ship system often uses solenoid valves to control the injection of fresh water for lubrication. The outlet pressure of the single screw pump cannot be too high, and too high pressure will also damage the pump body. Therefore, preventing the single screw pump from overpressure and dry friction is the premise for the normal operation of the single screw pump and is also the key to extending the working life of the single screw pump.

[0004] To prevent dry friction of single screw pumps, it is mainly to control the injection of fresh water into the pump body. At present, the main ways for marine single screw pump manufacturers to control fresh water injection are: 1) Delayed start mode, inject fresh water before the pump works, start the pump after a delay of 20-30 seconds, and stop fresh water injection at the same time; 2) Fresh water non-stop mode, inject fresh water when the pump starts, and the fresh water does not stop when the pump works, and the fresh water injection is stopped only after the pump stops running. 3) Pressure switch control mode, inject fresh water before the pump works, start the pump after a delay of 20-30 seconds, and stop fresh water injection when the pump outlet pressure reaches the set value.

[0005] The above methods of preventing dry friction of single screw pumps all have certain disadvantages. For example: Method 1) If the pump fails to pump water at the end of the delay, dry friction will occur; Method 2) The fresh water does not stop when the pump is working, wasting a lot of fresh water; Method 3) The pressure switch can ensure that the fresh water stops after the pump starts to suck liquid, but when the pump is emptied of the chamber or the liquid contains a lot of air, the pump cannot be stopped, causing low outlet pressure. At this time, dry friction will also occur and damage the pump. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a single screw pump protection system to prevent high and low pressure operation and dry friction, which is jointly controlled by a pressure monitoring device and a set of electrical control elements. The system can not only solve the dry friction problem during the startup process of the single screw pump, but also solve the high-pressure overload, low-pressure pumping and idling dry friction problems during the operation of the single screw pump, and provide all-round protection for the single screw pump during the operation of the pump.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] A single screw pump high and low pressure operation and dry friction protection system, comprising a single screw pump and a solenoid valve provided with the single screw pump, and also comprising a pressure monitoring device and an electrical control box;

[0009] The pressure monitoring device is installed at the outlet of the single screw pump and connected to the electrical control box; the pressure monitoring device is provided with a pressure switch and a pressure gauge, the pressure gauge monitors the outlet pressure of the single screw pump, and the pressure switch is triggered to open / close according to the value of the pressure gauge; the pressure switch includes a low-pressure pressure switch and a high-pressure pressure switch; the trigger pressure of the low-pressure pressure switch is P1, and the trigger pressure of the high-pressure pressure switch is P2;

[0010] The electrical control box is provided with a solenoid valve control switch, and the control switch is connected to the low-pressure pressure switch and the high-pressure pressure switch;

[0011] The system control process is as follows:

[0012] Press the start button to open the solenoid valve immediately to start water injection. After a delay of S1 seconds, the single screw pump will be started. After S2 seconds from the start of the single screw pump, the solenoid valve will be closed, the water injection will be stopped, and the high-pressure pressure switch and the low-pressure pressure switch will be connected to the control circuit. When the outlet pressure of the single screw pump is normal and between P1 and P2, the high-pressure pressure switch contacts will be closed and the low-pressure pressure switch contacts will be closed, and the single screw pump will keep running. When the outlet pressure of the single screw pump is abnormal, when it is greater than P2, the high-pressure pressure switch contacts will open and the pump will stop. Or when it is less than P1, the low-pressure pressure switch contacts will open and the pump will stop.

[0013] As a preferred embodiment, the electrical control circuit of the single screw pump includes a time delay relay KT1, a time delay relay KT2 and a main contactor KM1;

[0014] The high-pressure switch and the low-pressure switch are connected in series and then connected in parallel to the two ends of the first delay contact of the delay relay KT2. The first delay contact of the delay relay KT2 is connected in series with the instantaneous contact of the delay relay KT1 and then connected in parallel to the two ends of the start button. The start button is used to control the operation of the system. One end of the start button is connected to the power line, and the other end is connected to the stop button.

[0015] The solenoid valve is connected in series with the second delay contact of the delay relay KT2 to form a first branch; the coil of the main contactor KM1 and the coil of the delay relay KT2 are connected in parallel and connected in series with the delay contact of the delay relay KT1 to form a second branch; the first branch, the second branch and the coil of the delay relay KT1 are connected in parallel, one end of the parallel circuit is connected to the ground wire, and the other end is connected to the start button through the stop button; the stop button is used to control the system power off;

[0016] The normally open contact of the main contactor KM1 serves as a control switch for the single screw pump motor. When the main contactor coil is energized, it closes, so that the single screw pump motor is connected to the circuit and drives the single screw pump to work.

[0017] In the electrical control circuit, the high-pressure switch is normally closed, and the low-pressure switch is normally open; the delay contact of the delay relay KT1 is set to close after a delay of S1 seconds, and the instantaneous contact is closed after power is supplied; the delay contact of the delay relay KT2 is set to open after a delay of S2 seconds.

[0018] As a preferred implementation, the range of S1 is (0, 30s].

[0019] As a preferred implementation, S2 is adjusted according to the pressure monitoring status to ensure that after running for S2 seconds, the pressure of the single-screw pump is higher than the pressure setting value of the safety valve, thereby closing the low-pressure pressure switch contacts. At this time, the low-pressure switch and the high-pressure switch are connected in series in the control loop.

[0020] As a preferred embodiment, the motor of the single-screw pump is connected to the main power supply and powered by the main power supply; a transformer is connected in parallel to the main power supply, and the power line and ground line are connected to the output end of the transformer to power the delay relay KT1, the delay relay KT2, the main contactor KM1, the pressure switch and the solenoid valve.

[0021] As a preferred implementation, P1<Ps<P2<Pmax, wherein Ps is the pressure setting value of the safety valve provided in the single screw pump, and Pmax is the maximum working pressure of the pump.

[0022] As a preferred implementation, the pressure gauge is a liquid-filled, vibration-resistant mechanical pointer pressure gauge.

[0023] As a preferred implementation, the pressure monitoring device and the electrical control box are installed in the turbine piping system where the single screw pump is located.

[0024] The system of the present invention can effectively prevent dry friction from occurring during the startup phase and normal operation of the single-screw pump, which not only saves fresh water resources but also prevents dry friction caused by high and low pressure failures during pump operation, providing technical support for the long-term safe operation of the single-screw pump, improving the reliability of the ship's engine room system operation, extending the service life of the equipment, and increasing economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the piping electrical system diagram of the present invention.

[0026] Figure 2 This is the schematic diagram of the pressure monitoring device of the present invention.

[0027] Figure 3 This is the schematic diagram of the working control principle of the pump of the present invention.

[0028] Figure 4 This is the electrical schematic diagram of the electrical control box of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] As Figure 1 shown, this is the piping electrical system diagram of the present invention. The main components of the system include a single-screw pump 1, a pressure monitoring device 2, an electrical control box 3, a solenoid valve 4 driven by the single-screw pump 1, and other necessary valve parts and pipe fittings. The pressure monitoring device 2 is installed at the outlet of the single-screw pump 1 and is connected to the electrical control box 3; the pressure monitoring device 2 is provided with a pressure switch and a pressure gauge 7. The pressure gauge 7 monitors the outlet pressure of the single-screw pump 1, and the pressure switch triggers opening / closing according to the value of the pressure gauge 7. As Figure 2 shown, two high-pressure pressure switches 6, a low-pressure pressure switch 5 and a pressure gauge 7 are fixed on the pressure gauge board, and a three-way test valve, a copper capillary tube for the pressure gauge and an instrument valve are correspondingly installed to form a gauge board assembly as the pressure monitoring device 2, which is installed at the outlet of the single-screw pump 1 and is connected to the electrical control box 3 to output signals for pressure monitoring control.

[0031] When starting the single-screw pump 1 through the electrical control box 3, at the beginning, first control the solenoid valve 4 to open to inject fresh water. After a delay of S1 seconds (the time is adjustable), the single-screw pump 1 starts. After another delay of S2 seconds and when the outlet pressure of the single-screw pump 1 (the pressure monitored by the pressure gauge 7) is greater than the set value P1 of the low-pressure pressure switch of the pressure monitoring device, the solenoid valve 4 closes and the fresh water injection stops. When the single-screw pump 1 is working normally, when the pressure is greater than the set value P2 of the high-pressure pressure switch of the pressure monitoring device 2, the single-screw pump 1 stops working; when the pressure is less than the set value P1 of the low-pressure pressure switch of the pressure monitoring device 2 during the normal operation of the single-screw pump 1, the single-screw pump 1 also stops working.

[0032] like Figure 3 The schematic diagram of the pump working control principle of the present invention is shown. Press the electrical control box 3 to start the startup procedure. The first step is to control the solenoid valve 4 to open and inject fresh water. After a delay of S1 seconds (the time is adjustable), the single screw pump 1 is started. After another delay of S2 seconds, the solenoid valve 4 is closed to stop the water injection. The high-pressure switch 6 and the low-pressure switch 5 are connected to the control loop. At this time, the outlet pressure of the single screw pump 1 should be greater than the set value P1 of the low-pressure switch of the pressure monitoring device 2. If the pressure does not reach the P1 value at this time, the low-pressure switch 5 is not closed, and the pump stops. If the pump and the pipeline are normal, the time of S2 needs to be adjusted so that the time is enough for the pump to reach the normal pressure. The pressure value of the single screw pump 1 during normal operation is between 0 and the maximum working pressure Pmax of the pump. The single screw pump has its own safety valve, and the safety valve pressure setting value is Ps; the pressure value of the single screw pump 1 during normal operation should be between P1 and Ps. When the working pressure of the single screw pump 1 is lower than the P1 value, it means that the pump is faulty or there is no water in the system. At this time, the single screw pump 1 is controlled to stop working through the electrical control box 3; when the working pressure of the single screw pump 1 is higher than the P2 value, the pump's own safety valve is damaged, and the single screw pump 1 is abnormally working. At this time, the single screw pump 1 is also stopped by the electrical control box 3.

[0033] The electrical schematic diagram of the electrical control box 3 of the present invention is as follows Figure 4 As shown, it includes a time delay relay KT1, a time delay relay KT2 and a main contactor KM1;

[0034] The high-pressure switch 6 and the low-pressure switch 5 are connected in series and then connected in parallel to the two ends of the first delay contact of the delay relay KT2. The first delay contact of the delay relay KT2 and the instantaneous contact of the delay relay KT1 are connected in series and then connected in parallel to the two ends of the start button. The start button is used to control the operation of the system. One end of the start button is connected to the power line, and the other end is connected to the stop button;

[0035] The solenoid valve (4) is connected in series with the second delay contact of the delay relay KT2 to form a first branch; the coil of the main contactor KM1 and the coil of the delay relay KT2 are connected in parallel and then connected in series with the delay contact of the delay relay KT1 to form a second branch; the first branch, the second branch and the coil of the delay relay KT1 are connected in parallel, one end of the parallel circuit is connected to the ground wire, and the other end is connected to the start button through the stop button; the stop button is used to control the system to power off;

[0036] The normally open contact of the main contactor KM1 serves as the control switch of the single screw pump 1 motor. It closes after the main contactor coil is energized, so that the single screw pump 1 motor is connected to the circuit and drives the single screw pump 1 to work.

[0037] In the described electrical control circuit, the high-pressure pressure switch 6 is normally closed, and the low-pressure pressure switch 5 is normally open; the delay contact of the time-delay relay KT1 is set to close after a delay of S1 seconds, and the instantaneous contact closes when powered; the delay contact of the time-delay relay KT2 is set to open after a delay of S2 seconds; there is no pressure in the unpowered state, the low-pressure pressure switch 5 is open, and the high-pressure pressure switch 6 is closed. The motor of the single-screw pump 1 is connected to the 440V main power supply and is powered by the main power supply; a 440V / 220V transformer is connected in parallel to the main power supply, and the power line and ground wire are connected to the 220V output terminal of the transformer to supply power to the time-delay relay KT1, the time-delay relay KT2, the main contactor KM1, the pressure switch, and the solenoid valve.

[0038] In this embodiment, the delay range of the time-delay relay KT1 and the time-delay relay KT2 is set to 0 - 30 seconds.

[0039] Install the pressure controller and the electrical control box in the engine room piping system where the pump is located, connect each device in the system with corresponding pipes and cables, adjust the pressure setting values of the high and low pressure switches in the pressure controller according to the head parameters of the pump, set the time parameters of the time-delay relay in the electrical control box, and adjust the system to the working state.

[0040] Since the single-screw pump is installed above the cabin and works, when the pump starts to run, it first evacuates the air in the pipeline in front of the pump inlet before it can suck in oily sewage. Fresh water is pre-injected before the pump starts to prevent dry friction when the pump starts; after the pump starts, water is injected after a certain delay. When it is ensured that the pump fully sucks in liquid and can lubricate itself (the pump outlet pressure exceeds the set value of the low-pressure switch in the pressure controller), the solenoid valve is closed to stop the fresh water injection, thus completely preventing dry friction during pump startup and initial operation; the solenoid valve closing signal simultaneously controls the control functions of the high and low pressure switches in the pressure controller to ensure that the pressure switch can perform the next control work; the high-pressure pressure switch in the pressure controller prevents the pump body from being damaged by high pressure due to blockage at the pump outlet during pump operation, and the low-pressure pressure switch in the pressure controller can prevent dry operation at low pressure after the pump evacuates the liquid, ensuring that the pump will not have dry friction phenomena due to faults, etc. The pressure gauge can clearly display the pump outlet pressure state.

[0041] The normal P1 value of the commonly used single-screw pump on the ship is set at 1 bar, and the P1 value should be less than the set value Ps of the safety valve. The P2 value is usually 1 bar larger than the Ps value and less than Pmax.

[0042] The above is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those of ordinary skill in the art, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention shall be regarded as the protection scope of the present invention.

Claims

1. A single screw pump protection system for preventing high and low pressure operation and dry friction, comprising a single screw pump (1) and a solenoid valve (4) provided with the single screw pump (1), characterized in that: It also includes a pressure monitoring device (2) and an electrical control box (3); The pressure monitoring device (2) is installed at the outlet of the single-screw pump (1) and is connected to the electrical control box (3); the pressure monitoring device is provided with a pressure switch and a pressure gauge (7), the pressure gauge (7) monitors the outlet pressure of the single-screw pump (1), and the pressure switch triggers on / off according to the value of the pressure gauge (7); the pressure switch includes a low-pressure pressure switch (5) and a high-pressure pressure switch (6); the triggering pressure of the low-pressure pressure switch (5) is P1, and the triggering pressure of the high-pressure pressure switch (6) is P2; The electrical control box (3) is internally provided with a control switch for the solenoid valve (4), and the control switch is connected to the low-pressure pressure switch (5) and the high-pressure pressure switch (6); The electrical control circuit of the single-screw pump includes a time-delay relay KT1, a time-delay relay KT2, and a main contactor KM1; The high-pressure pressure switch (6) and the low-pressure pressure switch (5) are connected in series and then connected in parallel across the two ends of the first time-delay contact of the time-delay relay KT2. The first time-delay contact of the time-delay relay KT2 and the instantaneous contact of the time-delay relay KT1 are connected in series and then connected in parallel across the two ends of the start button. The start button is used to control the operation of the system. One end of the start button is connected to the power supply line, and the other end is connected to the stop button; The solenoid valve (4) and the second time-delay contact of the time-delay relay KT2 are connected in series to form a first branch; the coils of the main contactor KM1 and the time-delay relay KT2 are connected in parallel and then connected in series with the time-delay contact of the time-delay relay KT1 to form a second branch; the first branch and the second branch are connected in parallel with the coil of the time-delay relay KT1. One end of the parallel circuit is grounded, and the other end is connected to the start button through the stop button; the stop button is used to cut off the power supply of the system; The normally open contact of the main contactor KM1 serves as the control switch for the motor of the single-screw pump (1), and closes after the main contactor coil is energized, so that the motor of the single-screw pump (1) is connected to the circuit to drive the single-screw pump (1) to work; In the electrical control circuit, the high-pressure pressure switch (6) is normally closed, and the low-pressure pressure switch (5) is normally open; the time-delay contact of the time-delay relay KT1 is set to close after a delay of S1 seconds, and the instantaneous contact closes after being energized; the time-delay contact of the time-delay relay KT2 is set to open after a delay of S2 seconds; The system control process is as follows: Press the start button, immediately open the solenoid valve (4) to start water injection. After a delay of S1 seconds, start the single-screw pump (1). After the single-screw pump (1) starts running for S2 seconds, the solenoid valve (4) closes, stops water injection, and the high-pressure pressure switch (6) and the low-pressure pressure switch (5) are connected to the control circuit; when the outlet pressure of the single-screw pump (1) is normal, the contacts of the high-pressure pressure switch (6) and the low-pressure pressure switch (5) close to form a closed loop, and the single-screw pump (1) keeps running; when the outlet pressure of the single-screw pump (1) is abnormal: when it is greater than P2, the contact of the high-pressure pressure switch (6) opens and the pump stops; or when it is less than P1, the contact of the low-pressure pressure switch (5) opens and the pump stops.

2. The system according to claim 1, wherein The range of S1 is (0, 30s].

3. The system according to claim 1, characterized in that, The S2 is adjusted according to the pressure monitoring status to ensure that after running for S2 seconds, the pressure of the single screw pump (1) is higher than the pressure setting value of the safety valve provided in the single screw pump (1).

4. The system according to claim 1, wherein The motor of the single screw pump (1) is connected to a main power supply and powered by the main power supply; a transformer is connected in parallel to the main power supply, and the power line and the ground line are connected to the output end of the transformer to supply power to the time delay relay KT1, the time delay relay KT2, the main contactor KM1, the pressure switch and the solenoid valve.

5. The system according to claim 1, characterized in that, P1<Ps<P2<Pmax, where Ps is the pressure setting value of the safety valve of the single screw pump (1), and Pmax is the maximum working pressure of the pump.

6. The system according to claim 1, wherein The pressure gauge (7) is a liquid-filled, vibration-resistant mechanical pointer pressure gauge.

7. The system according to claim 1, characterized in that, The pressure monitoring device (2) and the electrical control box (3) are installed in the turbine piping system where the single screw pump (1) is located.

Images