Terminal Series – Article Five
Terminal Series – Article FiveContributed by Isaac Smith, Principal/District Manager, PPM Consultants
Applicable Regulations: NSPS Subparts XX and XXa and NESHAP Subparts R and BBBBBB (6B)
In EPA’s most recent Technology Review (TR) of the NSPS and NESHAP regulations applicable to gasoline terminals, vapor collection and combustion efficiency were a major focus. PPM’s Ned Coleman summarized the changes in an article entitled, EPA’s New Gasoline Distribution Rules are In Effect – What Existing Terminals Need to Know RIGHT NOW!
The performance of the vapor collection/recovery system is instrumental for both operational efficiency and regulatory compliance. This article provides a comprehensive, operations-focused framework for maintaining vapor recovery performance as rack volumes increase.
Introduction: Throughput Is Rising Faster Than Vapor Systems Can Keep Up
In addition to the updated NSPS and NESHAP regulations, bulk terminals today face intensifying operational pressures—more trucks per hour, expanded loading windows, tighter turnaround expectations, and product variability that shifts with seasonal demand. Yet amid these changes, vapor recovery systems (Vapor Recovery Units (VRUs) and Vapor Combustion Units (VCUs)) are often the last equipment to be evaluated when throughput expands. What operated smoothly under last year’s conditions may now struggle under higher throughput, leading to odors, instability, alarms, or unexplained bypass periods.
Drawing on PPM’s direct experience supporting facilities across the Southeast, we outline how hydraulics, hardware, monitoring, and operator habits interact to determine VRU reliability. Terminals that proactively adjust all four areas maintain compliance more consistently and avoid the downstream impacts of insufficient vapor control.
The Hidden Bottleneck No One Budgets For
Vapor recovery rarely appears on the capital planning radar until symptoms become unavoidable. As loading rack throughput increases, terminals often observe subtle shifts before major deviations appear. These early warning signs include:
- Intermittent odors at the rack
- Irregular or elevated backpressure across loading arms
- Spike-driven VRU instability during peak periods
- Inconsistent sensor readings or unexplained alarms
- Operators making informal setpoint adjustments during maximum loading
EPA’s petroleum storage and transfer guidance highlights a central challenge: vapor behavior is non-linear. As vapor generation increases, system friction, line losses, and knockout loading rise disproportionately. Even small pipeline restrictions magnify under higher loading scenarios, causing VRUs to see unstable flow or starvation during busy hours.
This operational reality places vapor recovery at the center of a facility’s compliance profile—whether or not leadership has intentionally planned for it.
Three Layers of Vapor Recovery Performance
Long-term VRU stability is never the product of one fix or one upgrade. It emerges from the integrated performance of hydraulics, hardware, and operator habits—three layers that reinforce or undermine each other.
- Hydraulics: The Unforgiving Backbone of Vapor Control
Hydraulics determine whether a VRU receives a steady, predictable vapor stream or a chaotic one. When headers are undersized or overly complex, the VRU experiences inconsistent suction and pressure, which complicates recovery efficiency.
EPA’s AP-42 Chapter 5 emphasizes the importance of minimizing pressure fluctuations in vapor systems to maintain consistent control efficiency. Terminals with long, narrow headers or multiple sharp elbows experience friction losses that increase exponentially at higher throughput.
Practical improvements include:
- Conducting hydraulic modeling based on peak hour—not average hour—scenarios;
- Increasing header diameter at known friction points;
- Adding or resizing knockout pots to prevent media saturation; and
- Removing routing obstructions and reducing sharp or unnecessary turns.
These adjustments often require less investment than facilities expect while delivering significant improvements in stability.
- Hardware & Setpoints: Matching System Design to Real Operating Conditions
A VRU’s internal condition—media health, valves, seals, flame arrestors—determines the system’s ability to handle load variability. EPA’s Control Techniques Guidelines for VOC control reiterate that control devices must be operated “within the manufacturer’s recommended limits” and tuned for real-world variability.
However, the challenge is rarely the physical equipment alone. It is the clarity of design intent.
Terminals perform best when they maintain a concise, operational document (a “why sheet”)—that explains:
- The rationale behind each critical setpoint;
- Expected normal ranges and seasonal adjustments;
- Alarm conditions that require shutdown vs. monitoring; and
- Recovery expectations during high-volatility product transfers.
- Habits: The Operational Glue That Holds the System Together
Even the best hardware will destabilize without proper operation. EPA’s accident prevention and documentation guidance under the Clean Air Act Section 112(r) underscores that consistent operational practices, especially for environmental control systems, reduce the probability of deviations and improve audit defensibility.
Effective terminals rely on:
- Simple, repeatable daily checks;
- Defined roles for alarm response; and
- Documented owners for daily, weekly, and monthly tasks.
These habits ensure vapor control remains consistent even as staffing or product profiles change.
Strengthening Monitoring and Recordkeeping
Vapor recovery documentation comes under increasing scrutiny as throughput rises. EPA has repeatedly emphasized that accurate operational records are crucial for demonstrating compliance and verifying that control devices are operating as intended.
A practical, defensible monitoring program includes:
Daily Checks
- One-screen review of key pressures, temperatures, alarms, and drains
- Quick, but thorough walkdown for visible leaks or abnormal noise
Weekly Checks
- Flame arrestor cleanliness
- Auto-drain verification
- Header leak survey
Monthly Checks
- Throughput vs. VRU runtime reconciliation
- Trend analysis on key operating variables
- Seasonal setpoint assessment
Deviation Log
EPA encourages the use of consolidated deviation records to clearly document corrective action. One log—complete with cause, action, and closeout—provides a defendable trail during inspections.
Commissioning and Change Management: Where Vapor Recovery Stability Lives or Dies
Whenever terminals add a bay, change products, or modify rack operations, vapor generation characteristics change as well. EPA’s permitting guidance for storage and transfer operations notes that apparent “minor changes” in throughput can meaningfully impact vapor control expectations.
To safeguard stability, facilities should treat every operational expansion as a mini-startup:
Pre-Startup
- Validate header capability against new throughout rates/volumes;
- Confirm knockout capacity under revised conditions;
- Update setpoints and the operational “why sheet”; and
- Refresh operator job aids.
Startup Week
- Increase monitoring frequency
- Conduct daily cross-functional check-ins between Operations, Maintenance, and EHS
Stabilization Month
- Finalize optimized setpoints
- Review near-misses
- Incorporate lessons learned into SOPs and training
This structured approach prevents surprises and aligns the vapor recovery system with real-world operations.
How PPM Helps Terminals Achieve Long-Term Vapor Recovery Operational Efficiency and Environmental Compliance
PPM consultants integrate hydraulics, equipment performance, operational behavior, and documentation into a single Vapor Recovery operational efficiency and environmental compliance strategy that combines:
- Header and hydraulic loading assessment;
- VRU/VCU capability evaluation;
- Control logic and setpoint optimization;
- Monitoring and recordkeeping upgrades;
- Job-aid and operator alignment support; and
- Air permitting and commissioning guidance.
Terminals that apply this approach consistently see fewer alarms, more efficient VOC control, and more predictable compliance during peak throughout.
Conclusion: Vapor Recovery Performance Begins with System Alignment
As throughput increases, vapor recovery systems must be reevaluated and realigned. The most stable terminals are not the ones with the newest VRUs—they’re the ones that treat vapor control as an integrated system requiring coordinated updates to hydraulics, hardware, monitoring, and habits. By applying these principles proactively, facilities protect compliance margins, reduce operational stress, and maintain stability even during their busiest periods.