A control method for a lubricating oil system without an elevated oil tank

Abstract

This invention discloses a control method for a lubricating oil system without an elevated oil tank. It primarily addresses the technical problems of existing control methods that rely on a DC oil pump as an emergency oil source, which suffer from startup lag leading to oil cut-off risks and slow interlocking logic response. This invention reduces the startup time to 2-5 seconds and triggers the threshold in advance, ensuring the DC oil pump establishes stable oil pressure before the spindle speed decreases, thus resolving the core safety hazard of not having an elevated oil tank. It employs a dual judgment mechanism of "rapid near-end response + far-end redundancy," ensuring both response speed (near-end signal) and safety (two out of three remote points), avoiding false starts or failures due to a single measurement point fault.

Description

Technical Field

[0001] This invention relates to a lubricating oil system control method, specifically a lubricating oil system control method without a high-level oil tank. Background Technology

[0002] In the lubrication system of large compressors, blowers and other rotating machinery, the elevated oil tank is a standard mechanical safety configuration. It uses gravitational potential energy to supply oil to the bearings when the main power supply of the unit fails or the main oil pump trips, ensuring that the unit continues to supply oil during coasting (inertial stop).

[0003] If the high-level oil tank is removed, the conventional alternative is to rely on the emergency oil pump (DC oil pump) as an emergency oil source. The existing control logic is usually as follows: unit trip signal trigger → interlock starts emergency oil pump → DC oil pump soft start establishes oil pressure.

[0004] However, the above alternatives have the following drawbacks:

[0005] 1. Risk of oil cut-off due to delayed start-up: DC oil pumps typically use a soft start method, with a start-up time of 2~10s. However, during the unit's coasting process, within the window period of oil pump start-up and oil pressure establishment, the system oil pressure will continuously drop, which can easily fall below the minimum allowable oil pressure of the bearing (such as 0.04MPa(G)), leading to bearing wear or even bearing failure.

[0006] 2. Slow response of interlock logic: Traditional low oil pressure interlock relies on a single measuring point. To prevent malfunctions, the pressure tapping point is usually from the farthest pressure of the main oil pipe near the machine (e.g., 60~80kPa). Due to the presence of the accumulator, the accumulator action will delay the rate of pressure drop, resulting in a sluggish emergency response. Summary of the Invention

[0007] The purpose of this invention is to solve the technical problems of existing control methods that rely on DC oil pumps as emergency oil sources, which have the risk of oil cut-off due to start-up lag and slow response of interlocking logic, and to provide a control method for a lubricating oil system without a high-level oil tank.

[0008] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0009] A control method for a lubricating oil system without a high-level oil tank, the lubricating oil system including a main pump and a DC oil pump whose input ends are connected to the lubricating oil station outlet; the output ends of the main pump and the DC oil pump are respectively connected to the bearing oil inlet of the unit to be lubricated through a local oil main pipe;

[0010] Its special feature is that it includes the following steps:

[0011] Step 1: Set the DC oil pump's start-up threshold to 100kPa~120kPa, set the DC oil pump's start-up and pressure build-up time to 2~5 seconds, and set the DC oil pump's oil supply to be at least 90% of the unit's maximum oil consumption;

[0012] Step 2: Construct the following control system:

[0013] A near-end sensor is installed at the outlet of the lubrication station, and a far-end sensor is installed at the end of the main oil pipe near the machine that is far from the DC oil pump; at the same time, logic units are installed that are electrically connected to the DC oil pump, the near-end sensor, the far-end sensor and the unit respectively.

[0014] Step 3: The near-end sensor and the far-end sensor respectively detect the near-end oil pressure value at the outlet of the lubricating oil station and the far-end oil pressure value at the end of the machine-side oil main pipe away from the DC oil pump, and feed it back to the logic unit.

[0015] Step 4: The logic unit determines whether the near-end oil pressure value and the far-end oil pressure value are lower than the start-up threshold. If either of them is lower than the start-up threshold, it controls the DC oil pump to start and controls the unit to perform interlock shutdown. The DC oil pump supplies oil to the bearings during the unit's inertial shutdown process until the unit stops, thus completing the control.

[0016] Furthermore, in step 2, there is one near-end sensor and M far-end sensors; M ≥ 3;

[0017] In step 4, the logic unit receives the near-end oil pressure value output by the near-end sensor and the M far-end oil pressure values ​​output by the M far-end sensors, determines whether the near-end oil pressure value and the M far-end oil pressure values ​​are lower than the start-up threshold, and controls the DC oil pump to start when the near-end oil pressure value is lower than the start-up threshold or when at least half of the M far-end oil pressure values ​​are lower than the start-up threshold.

[0018] Furthermore, in step 2, there are M near-end sensors and M far-end sensors;

[0019] In step 4, the logic unit receives M near-end oil pressure values ​​output by M near-end sensors and M far-end oil pressure values ​​output by M far-end sensors, determines whether the M near-end oil pressure values ​​and M far-end oil pressure values ​​are lower than the start-up threshold, and controls the DC oil pump to start when at least half of the M near-end oil pressure values ​​are lower than the start-up threshold or at least half of the M far-end oil pressure values ​​are lower than the start-up threshold.

[0020] Furthermore, M=3.

[0021] Furthermore, in step 1, the oil supply of the DC oil pump is set to be equal to the maximum oil consumption of the compressor or blower.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] 1. Eliminate the risk of coasting oil cut-off: By compressing the start-up time to 2~5s and triggering the threshold in advance, the DC oil pump is ensured to establish a stable oil pressure before the spindle speed drops, thus solving the core safety hazard of not having a high-level oil tank.

[0024] 2. Improve system reliability: The system adopts a dual judgment mechanism of "rapid response at the near end + redundancy at the far end", which ensures both response speed (near end signal) and safety (two out of three at the far end), avoiding false operation or failure to operate caused by a single measurement point failure.

[0025] 3. Reduced project costs and land occupation: It successfully replaced the high-level fuel tank, eliminating the need for high-level fuel tank supports, ladders and related civil construction, significantly reducing project costs and installation space requirements. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the lubricating oil system and the control system in an embodiment of the present invention (logic units are not shown).

[0027] Figure 2 This is a schematic diagram of the control logic of the logic unit in steps 3 and 4 of the embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0029] This embodiment discloses a control method for a lubricating oil system without a high-level oil tank. The lubricating oil system mainly includes a main pump and a DC oil pump, both with their input ends located at the lubricating oil station. The output ends of the main pump and the DC oil pump are connected to the bearing oil inlet of the compressor or blower to be lubricated via a local oil main pipe.

[0030] This embodiment provides a control method for a lubricating oil system without a high-level oil tank, specifically including the following steps:

[0031] Step 1: Equipment Selection and Parameter Optimization

[0032] Flow rate design: The DC oil pump must be designed to handle 90-100% of the unit's maximum oil consumption to ensure sufficient oil supply and provide a physical basis for quickly establishing system pressure. In this embodiment, the DC oil pump's oil supply is set to equal the compressor's or blower's maximum oil consumption.

[0033] Ultra-fast start design: The start-up time of the DC oil pump is strictly controlled within 2 to 5 seconds through the soft start device of the DC oil pump, minimizing the response blind zone.

[0034] Increase the interlock trigger threshold (early intervention): Breaking away from the conventional practice of setting the "low lubricating oil pressure" trip value to 60-80 kPa, this threshold is raised to 100-120 kPa. By widening the gap between the "low bearing lubricating oil pressure trip value" and the "minimum safe oil pressure," valuable startup time is gained for the DC oil pump. The corresponding low lubricating oil pressure alarm value is set at 150-160 kPa, corresponding to a main pipe lubricating oil pressure value of 250-300 kPa.

[0035] Step 2: Control Logic Optimization (Core Innovation)

[0036] Joint judgment based on dual signals:

[0037] See Figure 1 and Figure 2 Two independent low oil pressure interlock trip monitoring circuits are set up, and the shutdown protection is executed when either one is triggered.

[0038] 1) Remote Monitoring: A remote sensor is set up to collect the pressure signal at the farthest point of the main oil line near the machine. To prevent malfunctions from a single measuring point, a redundant logic of "two out of three" (2oo3) is used. That is, if any two of the three pressure transmitters detect low oil pressure (below the trip value), it is determined that the remote oil pressure is low. This ensures the safety of the system under complex operating conditions and avoids malfunctions. This also serves as an interlocking command to start the DC oil pump.

[0039] 2) Proximity monitoring: Install a proximity sensor to collect the pressure signal P at the lubrication station outlet. near Because the accumulator is installed near the gas station outlet, if the main pump loses power, the outlet pressure will drop instantly due to the loss of power, and the rate of drop will be much faster than the pressure in the distant main pipe. Utilizing this physical characteristic, P... near As the primary trigger source, it significantly shortens the logic response time. near Use single-point pressure or redundant logic of "two out of three" (2oo3).

[0040] 3) Set up the logic unit and connect the logic unit to the remote sensor, the near sensor and the unit respectively.

[0041] Step 3, see Figure 2 During normal operation of the unit, the oil pressure is 200kPa~250kPa. The near-end sensor and the far-end sensor detect the near-end oil pressure value at the outlet of the lubrication oil station and the far-end oil pressure value at the end of the oil main pipe away from the DC oil pump, respectively, and feed them back to the logic unit.

[0042] Step 4, Logic Execution: See Figure 2 Real-time comparison of P logic units near With the remote pressure signal. As long as P nearFirst, the pressure drops to 100~120kPa (main pump power failure / unit trip signal), and the logic unit immediately triggers the DC oil pump to start and interlock protection. If the near-end signal fails, the far-end "two out of three" signal is used as a fallback protection. The DC oil pump is used to supply oil to the bearings during the unit's inertial shutdown process until the unit stops, thus completing the control.

[0043] Simulation results show that after removing the high-level oil tank, the bearing inlet pressure remains above 0.6MPa and does not fall below the safety limit when using the 2-5s rapid start-up scheme of this logic.

[0044] In actual operation, the data shows that under the simulated main pump power failure condition, the system switching is smooth (oil pressure drops to a minimum of 0.8MPa), and there are no abnormal pressure fluctuations during the unit coasting process.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A control method for a lubricating oil system without a high-level oil tank, the lubricating oil system comprising a main pump and a DC oil pump whose input ends are connected to the outlet of a lubricating oil station; the output ends of the main pump and the DC oil pump are respectively connected to the bearing oil inlet of the unit to be lubricated via a local oil main pipe; characterized in that Includes the following steps: Step 1: Set the DC oil pump's start-up threshold to 100kPa~120kPa, start-up and pressure build-up time to 2~5 seconds, and oil supply to at least 90% of the unit's maximum oil consumption; Step 2: Construct the following control system: A near-end sensor is installed at the outlet of the lubrication station, and a far-end sensor is installed at the end of the main oil pipe near the machine that is far from the DC oil pump; at the same time, logic units are installed that are electrically connected to the DC oil pump, the near-end sensor, the far-end sensor and the unit respectively. Step 3: Detect the near-end oil pressure at the outlet of the lubricating oil station and the far-end oil pressure at the end of the machine-side oil main pipe furthest from the DC oil pump using the near-end sensor and the far-end sensor respectively, and feed them back to the logic unit. Step 4: Use a logic unit to determine whether the near-end oil pressure value and the far-end oil pressure value are lower than the start-up threshold. If either of them is lower than the start-up threshold, control the DC oil pump to start and control the unit to perform interlock shutdown. During the unit's interlock shutdown, the DC oil pump will supply oil to the bearings during the unit's inertial shutdown process until the unit stops, thus completing the control.

2. The lubricating oil system control method without a high-level oil tank according to claim 1, characterized in that: In step 2, there is one near-end sensor and M far-end sensors; M ≥ 3; In step 4, a logic unit receives the near-end oil pressure value output by the near-end sensor and the M far-end oil pressure values ​​output by the M far-end sensors, determines whether the near-end oil pressure value and the M far-end oil pressure values ​​are lower than the start-up threshold, and controls the DC oil pump to start when the near-end oil pressure value is lower than the start-up threshold or when at least half of the M far-end oil pressure values ​​are lower than the start-up threshold.

3. The lubricating oil system control method without a high-level oil tank according to claim 1, characterized in that: In step 2, there are M near-end sensors and M far-end sensors; In step 4, the logic unit receives M near-end oil pressure values ​​output by M near-end sensors and M far-end oil pressure values ​​output by M far-end sensors, determines whether the M near-end oil pressure values ​​and M far-end oil pressure values ​​are lower than the start-up threshold, and controls the DC oil pump to start when at least half of the M near-end oil pressure values ​​are lower than the start-up threshold or at least half of the M far-end oil pressure values ​​are lower than the start-up threshold.

4. A control method for a lubricating oil system without a high-level oil tank according to claim 2 or 3, characterized in that: M=3。 5. The lubricating oil system control method without a high-level oil tank according to claim 1, characterized in that: In step 1, the oil supply of the DC oil pump is set to be equal to the maximum oil consumption of the unit.

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