Evaluation of tank vent systems and tank inerting practices.
CHEMICAL FACILITY TANK VENT SYSTEMS EVALUATION
The client owns and operates a batch chemical production facility that produces several specialty chemical products. Process Engineering Associates, LLC (PROCESS) was contracted by the plant engineering group to conduct an evaluation of the vent systems for four (4) process tanks that had been identified during process hazard analysis (PHA) as needing the design bases validated. More specifically, PROCESS was asked to complete two primary project tasks: (1) review the overall tank inerting and vent system design from the standpoint of applicable guidelines and regulations and good engineering practices, and (2) evaluate the capacities of the tanks’ pressure/vacuum relief systems versus calculated relief requirements.
PROCESS first requested all available engineering data for the tanks including P&IDs of the tanks and associated processes and manufacturers’ information for the tanks, vent system components (conservation vents, flame arrestors, rupture disks, and solvent condensers), and associated equipment and instrumentation that could be credibly involved in an overpressure/undervacuum scenario. PROCESS’ evaluation of the inerting and vent system design revealed that, though PROCESS would recommend inerting three of the four tanks, all tank vent systems met the requirements of applicable guidelines and regulations. This information was summarized in a verbal report to the client project manager.
During the relief systems capacity evaluation task, PROCESS used the available client engineering information, API-2000 and UL-142 guidelines for low-pressure tanks, andPROCESS’ in-house relief capacity evaluation and compressible flow programs to calculate relief requirements and relief system component capacities for all identified credible relief scenarios. (Credible relief scenarios included external fire, outbreathing with pump-in, inbreathing with pump-out, and steam coil rupture.) PROCESS’evaluation showed that three of the four tanks required relief system capacity upgrades, all due to the external fire scenarios. Options for capacity upgrades included the replacement/ addition of conservation vents, replacement of rupture disks, and condenser vent size increase. In addition, the option of adding insulation to the tanks for reducing the fire scenario relief requirements was offered as a potential solution. The results of this task were assimilated into a project report that included a letter summary; tabular summary of relief capacities, requirements, and recommendations; and backup computer program output and manual calculations.
- Batch Chemical Production
- API and UL guidelines interpretation
- Pressure relief vent or pressure safety vent sizing