Many oil depots and gas stations face the challenge of upgrading their condensation recovery devices installed in earlier years due to emission standards upgrades or non-compliance with testing standards. Replacing the entire system would involve significant investment, and halting operations to wait for the new device would affect business. Installing a membrane control section behind the existing condensation device is a compromise modification approach - retaining the main condensation recovery section while using the membrane to capture emissions from the low-concentration section. This approach saves investment, shortens the construction period, and can reduce the downtime to a few days. This article clarifies the evaluation points, implementation process, and downtime arrangement of this modification approach, providing a reference for stations with upgrade plans.
First, assess whether it can be changed
Before the transformation, three things need to be done: First, assess the current situation - the processing capacity of the existing equipment, condensation temperature level, and compressor margin, to determine whether the subsequent stage with added membrane can withstand the pressure of the preceding stage; second, gather data - emission testing reports and operating condition records, to confirm the volume and concentration range of uncondensed tail gas, which are inputs for membrane area calculation; third, verify the site - the land occupation, power supply, and pipeline routing of the membrane skid, and whether there is enough space for layout within the station. After completing these three tasks, conclusions on whether to proceed with the transformation and how to proceed will be reached. Scheme comparison and investment estimation are all based on this set of data.
How to go through the transformation process
Five steps of the process: Based on actual measured data, determine the membrane area and number of stages for scheme design, and generate a configuration list and construction drawings; prefabricate skids and pipe sections in the factory to minimize on-site workload; complete on-site construction within the downtime window - opening old pipelines, connecting membrane skids, electrical and control wiring, which usually takes three to five days; conduct water testing followed by gas testing for commissioning, and perform emission testing after parameter setting; archive completion documents and calibration data during acceptance and delivery. Control logic is upgraded synchronously: the membrane section switches on and off according to the concentration of uncondensed tail gas, and is linked with the condensing unit without synchronization to avoid power consumption under no-load conditions.
How to arrange the business suspension window
The downtime window is a key constraint in the renovation plan: gas stations choose low-sales periods, and oil depots avoid concentrated receiving and dispatching periods; pipe sections and skid-mounted units are prefabricated in factories, with only on-site connections required, reducing the construction period from the conventional two weeks to three to five days; the construction sequence is well planned, and testing agencies are scheduled in advance. The business losses outside the window, along with the renovation investment, are calculated into the total account - when comparing and selecting plans, the overall replacement and retrofitting plans are presented on a single table, with investment, construction period, and downtime losses compared item by item, making the conclusion clear at a glance.
There are two supporting tasks that are easily overlooked during the renovation: First, explosion-proof zoning review - after adding membrane skids and electrical wiring, the zoning map needs to be updated, and the explosion-proof inspection records need to be supplemented simultaneously. Second, revision of operating procedures - membrane segments should be added to the inspection items, and pressure difference, dew point, and vacuum degree should be recorded in the existing ledgers. Old employees' operating habits should be reviewed according to the new procedures, so that there are no omissions during shift handover. Only when all supporting tasks are completed can the renovation be considered truly completed.
Comparison before and after transformation
| Comparison item | Complete replacement | Installing film quality control section |
|---|---|---|
| investment | Fully new purchase | Reusing the previous stage saves investment |
| construction period | Several weeks | "Three to five days window" |
| Business suspension impact | long-term outage | Controllable with short window |
| Emission capacity | Brand-new indicator | The membrane segment traps the low-concentration segment |
| Control System | Overall new configuration | Linkage logic upgrade |
| Applicable prerequisites | The front stage is severely aged | The previous stage is in a decent state |
Delivery and subsequent management
- The completion data and calibration data shall be archived in duplicate, with the station and the factory each holding one set;
- Operation training covers all on-duty personnel, and only those who pass the assessment can independently perform their duties;
- The inspection plan is incorporated into the existing ledger, and the pressure difference dew point is recorded daily;
- The emission testing report should be archived on schedule to maintain data continuity;
- Arrange a return visit in the first month of operation to promptly correct any parameter drift;
- During subsequent expansion, adjust the settings and verify to avoid redundant inspections.
Frequently Asked Questions
How can we determine whether the old device can be modified?
Focus on three aspects: the operational lifespan and maintenance records of the compressor and condensing unit, whether the temperature level can still stably reach the design value, and the concentration level of the uncondensed section in the emission test; if all three aspects are satisfactory, the economic benefits of retrofitting and upgrading will be significantly better.
Can the gas station still operate during the renovation period?
The collection and condensation pre-stage should remain operational in front of the window, with only the back-end interface being shut down for three to five days; the unloading and refueling operations should be arranged to avoid peak hours, so most stations do not need to shut down the entire site.
How much can the recovery rate be increased after the transformation?
It depends on the concentration range of the uncondensed section: after the membrane control section traps the low-concentration emissions, the overall recovery rate generally increases. The specifics should be based on the comparison of actual measurement data before and after the modification.
This article is compiled by Luoyang Wohong Petrochemical Equipment Co., Ltd. The company provides design and manufacturing, skid-mounted customization, installation and commissioning, as well as after-sales operation and maintenance services for three-time oil and gas recovery equipment to gas stations and oil depots. If you need on-site inspection or scheme configuration, please feel free to contact us for discussion.