On the design of vapor recovery pipelines for vehicle loading
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\"Design Code for Automation Systems of Petrochemical Tank Areas\" SHT3184-2017 9.3.3.1 When closed filling with oil and gas recovery is used, a gas recovery on-off valve shall be installed on the oil and gas recovery pipeline at the loading crane. 9.3.3.2 Switch valves should preferably be ball valves, gate valves, or butterfly valves – valves that can be switched on and off. In the event of a failure, these valves should operate in the failed closed (FC) state, and control should be achieved through differential pressure. Is it required to install one at each crane position in the gas phase system? Is there also an emergency shut-off valve on the main gas phase line?
The provision specifies that it should be installed on each “oil and gas recovery pipeline at the crane position”. As for the main pipe, first examine the design, second check the specifications, and third make the installation based on actual needs.
Taking SH3184 as an example alone, it is sufficient to have a gas recovery switch installed at each crane position in accordance with the standard requirements; no specific requirements are set for the main pipelines. If other requirements are taken into account, there will be slight differences between various regions. For example, in Dongying, Shandong Province, the city requires gas-phase automatic interlock switches that will activate automatically when there is no flow reading, which represents a stricter requirement than that for ordinary on/off valves. Emergency shut-off valves have been installed 10 meters away from the loading pipelines; in other words, they are available for both the liquid and gas phases. However, such modifications are hardly feasible during operation, so if there is an opportunity for maintenance, it’s best to carry out the work in one go, without being overly constrained by regulatory requirements. After all, multiple modifications incur high costs and increase safety risks. The above are merely personal opinions for reference only.