--- title: Closed Vent System Evaluation description: 'EPA regulations under 40 CFR Part 60, Subparts OOOOa and OOOOb, require operators to demonstrate that closed vent systems are designed and sized to route…' canonical: 'https://bellengr.com/services/cvs-evaluation/' url: 'https://bellengr.com/services/cvs-evaluation.md' post_id: 1130 post_type: page last_modified: '2026-04-15T22:08:46-05:00' last_converted: '2026-04-27T08:42:00-05:00' --- # Closed Vent System Evaluation ![](https://bellengr.com/wp-content/uploads/2026/04/cvs-tank-battery.jpg) ## Closed Vent System Evaluation & PE Certification EPA regulations under 40 CFR Part 60, Subparts OOOOa and OOOOb, require operators to demonstrate that closed vent systems are designed and sized to route all emissions from storage vessels to a control device without exceeding tank protection setpoints. A qualified Professional Engineer must certify the assessment. Bell Engineering® provides independent CVS evaluation and PE-stamped certification for surface facilities across the Permian and Delaware basins. With over 100 PE-certified reports delivered and 57+ facilities evaluated, our team brings the process engineering expertise and field experience to get your sites certified efficiently and correctly. --- ## Initial OOOOb Site Evaluation Bell conducts complete field audits, process simulation, and PE-stamped certification for new or previously unevaluated facilities. Our engineers document vent line configurations on-site, develop process flow diagrams, and build ProMax steady-state models using the OOOOb Vent Assessment Tool. The evaluation determines whether the facility's vapor control system can handle all predicted flash gas and working vapors without exceeding the setpoint of tank protection equipment. If the system passes, a PE-stamped certification report is issued ready for regulatory submittal. If it does not pass, Bell provides a detailed gap analysis identifying specific deficiencies and the remediation path to achieve compliance. Turnaround is two weeks from receipt of data for groups of one to five sites. Field work capacity is five sites per day, with one day per site for calculations and report preparation. - Complete on-site field audit and vent line configuration documentation - Process flow diagram development and equipment inventory - ProMax steady-state simulation using the OOOOb Vent Assessment Tool - Pass/Fail determination with full vent system pressure profile - PE-stamped certification report ready for regulatory submittal - Detailed gap analysis and remediation path (if applicable) - Two-week turnaround for groups of one to five sites ![](https://bellengr.com/wp-content/uploads/2026/04/cvs-engineering-simulation.jpg) ![](https://bellengr.com/wp-content/uploads/2026/04/cvs-technical-report.jpg) ## Report Revalidation After Modifications When equipment changes at a previously certified site, such as new VRUs, flares, combustors, or piping modifications, the existing OOOOb certification must be updated. Bell revises the ProMax model to reflect the current configuration, recalculates pressure profiles through the vent system, and reissues the PE-stamped report. Bell retains simulation models for all previously evaluated sites, enabling rapid revalidation without a return field visit when modification details are provided. Turnaround is 24 hours from receipt of required data, with capacity for two revalidations per day. ## Engineering Methodology Bell uses ProMax, the industry-approved process simulator, with the OOOOb Vent Assessment Tool to perform steady-state evaluations of facility vent systems. The model calculates flash gas rates from storage tanks, determines the pressure profile through vent lines to the control device, and compares the resulting tank pressure against relief device setpoints. The fundamental result is a Pass or Fail determination. Pass indicates the required pressure to move gas through the vent system to the vapor control device is below the tank relief setpoint. Fail indicates gas could be emitted to the atmosphere through the protection devices. The tool also reports flow rates, a full pressure profile, and the percent overdesign of the system. Steady-state evaluations are appropriate for facilities with throttling-type dump valves, open flare configurations, or where the peak vapor flow to control system capacity ratio is at or below one. ![](https://bellengr.com/wp-content/uploads/2026/04/cvs-vapor-recovery.jpg) ![](https://bellengr.com/wp-content/uploads/2026/04/cvs-oilfield-aerial.jpg) ## Operating Regions Bell's CVS evaluation team has conducted field audits across the Permian and Delaware basins in both Texas and New Mexico. Facilities evaluated include central processing facilities (CPFs), compressor stations, tankless CPFs, and well sites with major production equipment. Texas coverage includes Midland, Howard, Glasscock, Reeves, Loving, Yoakum, Gaines, Ector, Ward, Crane, and Coke counties. New Mexico coverage includes Eddy and Lea counties in the Delaware Basin. Site types include facilities equipped with VRUs, single and multiple VCUs, open flares, enclosed combustors, and various combinations of vapor control equipment. ## Qualifications Bell Engineering® has provided process studies, certifications, engineering, and construction services to industrial clients since 1984. All CVS reports are certified by Bell's in-house registered Professional Engineer. Texas Firm #7594. Our field personnel are ISNetworld and Avetta qualified, PEC SafeLand USA Basic certified, and trained in general industrial safety awareness through the ISTC & ARSC Basic Orientation Plus program. Our process engineering team averages over 25 years of experience, bringing the technical depth required for accurate simulation modeling and the practical field judgment to document complex vent system configurations correctly the first time. ![](https://bellengr.com/wp-content/uploads/2026/04/cvs-engineering-team.jpg) ## Put Our Engineering Expertise to Work for You Rather talk than type? Call now for a consultation (409) 745-2877 [View our Capabilities Statement](https://bellengr.com/wp-content/uploads/2026/04/Bell_Engineering_Capability_Statement_2026.pdf). [Submit A Request](/contact/)