Is the three-time oil and gas recovery device closed during oil unloading? How does the oil unloading match the operation of the device?
Release date: 2026-10-13
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Is the oil and gas recovery device closed three times when unloading oil? Direct answer: In most scenarios, it is recommended to suspend the three-time device during the oil unloading period, or set up pressure linkage according to the working conditions of the station-a large amount of oil enters the tank during oil unloading, the oil and gas in the tank is compressed and the pressure rises rapidly, and the oil and gas will be pushed back to the tank car through the air return pipeline. At this time, if the three devices suck at the same time, the suction of the suction of the vacuum pump when the tank is close to the tank, the failure of filter components by oil immersion is not uncommon in the investigation record. During oil unloading, the tank car and the oil tank form a self-contained loop, and the oil and gas have a place to go. The three devices do not need to work at the same time. In this paper, the oil unloading and the device with a clear relationship.
What happened in the tank during unloading?
Oil unloading is the process of oil flowing from the tanker into the buried tank. The replaced oil and gas enter the tanker along the return pipeline and are taken away. This circuit is the body of oil and gas recovery. When the oil inlet speed is fast, the pressure in the tank rises for a short time, and both the breathing valve and the circuit are under pressure. If the device sucks at the same time, it is equivalent to adding an external suction force under the condition of full tank high pressure, the gas-liquid interface fluctuates, and the risk of liquid carrying is obviously increased. The tanker took away the oil and gas and returned to the oil depot for centralized treatment. The three devices in the station could not have helped in the oil unloading window.
Cost of oil intake of the unit
Liquid oil enters the tertiary device, soak the filter components first, and the cleaning and repair costs are high. If the oil goes deeper, the vacuum pump and sensor may be damaged, and the downtime is calculated on a weekly basis. This kind of failure mostly occurs in the working condition of "nearly full tank is still unloading oil", which is a typical loss that can be avoided by operation sequence. In addition to direct losses, the tank pressure was not managed during the outage of the unit, the number of breather valve trips increased, emissions and oil losses rose simultaneously, and there was one more on the books.
How to match the oil unloading with the device
Three methods are selected according to site conditions: manual mode, stop the device on site before unloading oil, and confirm that the tank pressure will fall back and then resume after unloading, which is suitable for stations with low unloading frequency and special personnel on duty; Pressure linkage, oil unloading interlock or pressure upper limit locking is added to the device control logic, and the device will automatically suspend and resume automatic operation when the tank pressure is higher than the set value, which is suitable for unattended scenes; Time stagger, the unloading of oil is arranged in the low load period of the unit to reduce the overlap. Either way, the operation should be written into the oil unloading operation process, so that the oil unloader can know the state of the device during oil unloading, and the oral explanation during shift change is not as reliable as black and white.
Scene Processing Reference
| Scene | Recommended practice | Key points |
|---|---|---|
| Conventional oil unloading | Suspension device or linkage locking | After unloading, confirm that the tank pressure drops and then recovers. |
| Close to full tank unloading | must be suspended | Working condition with highest liquid risk |
| No oil unloading at night | Pressure linkage locking | Interlocking function measured monthly |
| high frequency oil unloading station | Time Staggering Arrangement | Unloading window to avoid device full load |
| Renovation construction period | Device outage tag-out | Prevent accidental startup |
| Tank car gas return failure | Stop unloading prerepair circuit | Do not continue to unload oil when the circuit is blocked. |
Operation arrangement steps
- Check the overlap between the unloading period of the station and the operation of the unit;
- Determine whether to adopt manual suspension or pressure linkage scheme;
- Write the device status confirmation into the oil unloading operation ticket;
- Confirm that the tank pressure drop device automatically recovers after oil unloading;
- Check the effectiveness of linkage function monthly;
- Record of abnormal oil feed events shall be archived and rewritten.
Frequently Asked Questions
When unloading oil, turn off the device. What if the tank pressure rises too high?
The oil and gas in the tank enters the tanker along the return pipeline, and the tank pressure will not be out of control when the circuit is unobstructed. If the tank pressure continues to rise, check whether the return circuit is blocked first, instead of opening the device three times in a hurry.
What is the set value of pressure linkage?
Combined with the setting of the breather valve in the tank farm and the setting of the upper limit of the inlet pressure of the device, in principle, it is lower than the take-off pressure of the breather valve and higher than the upper limit of the normal operation interval. During debugging, the operating point is verified by simulating the unloading working condition.
What if I forget to resume the operation of the device?
The status of the device shall be included in the shift change checklist, and the "recovery confirmation" signature item shall be added to the oil unloading operation ticket; For stations equipped with remote monitoring, reminders will be automatically pushed when the outage expires.
This article is compiled by Luoyang Wohong Petrochemical Equipment Co., Ltd., which provides design, manufacturing, and operation and maintenance services for condensation recovery, membrane separation recovery, and complete solvent recovery equipment to chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please feel free to contact us for discussion.
