Please provide the content of the company news you would like translated. The working principle of a heavy oil station
The working principle of the thin oil stations is essentially the same: oil is extracted from the oil tank by a gear pump, passing through a one-way valve, a twin-chambered mesh filter, and a heat exchanger, before being directly delivered to the equipment's lubrication points. Each thin oil station is equipped withTwo oil pumps, one in operation and one in standby. The oil pressure output from the oil station pump is 0.4 MPa, with a flow rate of 2.5 L/h.
Lubrication Process: Work Oil Pump - One-Way Valve - Filter - Condenser(Summer Use) Pressure relay, main equipment lubrication point returns to oil tank — oil pump.
Two Existing Issues with Crude Oil Station Control
The electrical control circuit is complex, with a high number of intermediate relays (total of 6), resulting in a high failure rate and making troubleshooting and repair extremely challenging.
2) The control methods are outdated; the main and auxiliary switching of the two oil pump motors must be performed on-site, precluding centralized control operations. With a shortage of on-site staff amidst numerous equipment, delays in issue detection often lead to damage to the main equipment, impacting production.
3) The oil station measures pipeline oil pressure through pressure relays to reflect the equipment's lubrication condition, which has poor sensitivity and accuracy, making it difficult to ensure reliable lubrication monitoring. The lubrication status monitoring methods for the oil station are: first, pressure relays; second, pressure transmitters. Both have certain issues.
①Under oil passage blockage, the oil pipe pressure remains high, but the lubricant does not flow normally, resulting in insufficient lubrication for the equipment. However, the monitoring of the lubrication condition is to determine if the pressure inside the oil pipe is below the set value, so the monitoring circuit still indicates normal. Prior to the modification, due to the pressure relay of the thin oil station not accurately reflecting the lubrication condition, the reducers of the limestone crushing board feeder and the shaft bearings of the cement mill were damaged.
②Lubrication points of the main machine equipmentThe (shaft bearing or reducer) maintains a certain height difference from the oil tank of the oil separator to ensure that the lubricating oil flows smoothly back into the oil tank. This results in a height difference between the drain pipe outlet and the oil tank, and a one-way valve is installed in the outlet pipeline of the oil pump to prevent backflow. Therefore, even if the oil pump stops operating, there is still a certain static pressure of the lubricating oil in the pipeline, which may even exceed the set value of the pressure relay.
③The size of the oil pipe port at the lubrication equipment's oiling location also directly affects the oil pressure value of the pipeline, leading to incorrect judgments about the pressure size.
④Pressure relays provide switch signals only, which cannot be used to display pressure values on the central control. They can only trigger alarms or stop the system, and emergency measures cannot be pre-set.
Three Revamp Plan
After thorough investigation and deliberation, we have transitioned from monitoring oil pipe pressure to monitoring flow. This involves installing a flow transmitter in the oil line to measure the lubricating oil flow. Whether it's the size of the oil pipe outlet, blockages, static pressure in the pipeline, or the motor turning while the oil pump fails to supply oil, as long as there is flow, it meets the lubrication requirements.
3.1 Flow Transmitter Replaces Original Electrical Contact Pressure Gauge
Our company has selected a Differential Capacitance Flow Transmitter, which utilizes differential capacitance as the monitoring element. The transmitter is completely mechanical-free with no adjusting devices, and the measuring section features a fully enclosed, welded solid structure. As a result, the instrument boasts a simple structure, stable and reliable performance, and high accuracy.
The differential capacitance flow transmitter measures the changing pressure, i.e., the input differential pressure.Δpi. Only when the liquid oil is flowing can it act on the pressure-sensitive membrane of the measuring component, causing it to displace, thereby changing the capacitance of the differential capacitor composed of the pressure-sensitive membrane (i.e., the movable electrode) and the two fixed electrodes. This change in capacitance is converted into a DC current signal by a capacitance-to-current conversion circuit. The sum of the current signal and the zeroing signal is compared with the feedback model, and the difference is sent to the amplification circuit, which amplifies it to obtain the overall output current I○ (standard 4~20mA) for display and control in the control room.
Static pressure does not generate differential pressure, thus avoiding the misinterpretation of static pressure as normal lubrication by pressure transmitters when the pipeline is blocked.
3.2 The DCS program control replaces the original complex intermediate relay
With our companyThe改造 of Freelance 2000 DCS Distributed Control System has been completed, with all electrical controls at the on-site lube oil stations replaced by DCS program control. This has fully realized centralized control in the control room for the switch of main and auxiliary oil pump motors, as well as the display of process pressure, simplifying the control loop and significantly reducing the failure rate, ensuring the normal lubrication of the main equipment.
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