September 27, 2024: This article was originally published on July 26, 2024. Since then, the EPA has released guidance that clarifies applicability. The article has been updated to reflect those updates.
In March 2024, the Environmental Protection Agency (EPA) published new regulations (NSPS OOOOb) aimed at curbing methane and volatile organic compound (VOC) emissions from the oil and gas industry. In this article, we dive into the requirements of NSPS OOOOb for centrifugal and reciprocating compressors used at onshore natural gas processing plants, compressor stations, and centralized production facilities.
Who Needs to Comply with NSPS OOOOb for Centrifugal & Reciprocating Compressors?
The EPA’s rule states that any compressor constructed, modified, or reconstructed after December 6, 2022, is an affected facility. Construction is defined in NSPS general provisions as fabrication, erection, or installation of an affected facility. Based on our analysis:
- The rule applies to operators of centrifugal and reciprocating compressors.
- It affects compressors installed after December 6, 2022.
EPA updates its site with frequently asked questions that help explain the rule’s definitions and requirements. We encourage operators to continue to review the site for future updates.
NSPS OOOOb Requirements for Centrifugal and Reciprocating Compressors
As part of the new regulation, compressors now have three options for wet/dry seal and rod packing vent routing:
- Route them to a control device with at least 95% efficiency.
- Return them to the process. However, this option comes with a strict requirement. The design and operation of the process return system must be foolproof, eliminating any possibility of emissions escaping.
- Conduct routine volumetric monitoring
Centrifugal and Reciprocating Compressors Vent Limits and Monitoring
The rule establishes specific leak limits for each compressor type and requires facilities to maintain a low volumetric flow rate. These rates apply when compressors are in operating or standby mode.
To ensure compliance, facilities must implement routine monitoring and repair practices for all compressor seals. Additionally, they are required to conduct initial monitoring and flow rate measurements within 8,760 operating hours of the effective date (May 7, 2024).
Flexibility for Reciprocating Compressor Monitoring
The rule offers some flexibility for reciprocating compressors regarding the initial monitoring timeline. This flexibility allows facilities to align the initial monitoring with existing maintenance procedures, minimizing disruption. Facilities can choose the most convenient option for their maintenance schedule:
- Within 8,760 operating hours of the effective date.
- Whichever comes later: the last flow measurement or the most recent compressor rod packing replacement.
Repair Requirements for Compressor Vents
The EPA requires repair/overhaul of vents exceeding the allowed limit within 90 days. Following repairs, a verification of success must be completed within 15 days. The EPA allows a delay of repair justification if deemed infeasible due to safety concerns, vent blowdown requirements, or the next scheduled shutdown (whichever comes first). Additionally, a delay is allowed if the specific repair part is unavailable, but the part must be ordered within 10 days. Because most compressors will require a vent blowdown to replace packing or seals, the 15-day verification following repair will involve close coordination between equipment vendors, in-house mechanics, environmental departments, and contractors.
Recordkeeping and Reporting Requirements
NSPS OOOOb requires facilities to implement a reporting system for their compressors. There are two options to choose from:
- Closed-Vent Systems: Facilities utilizing closed-vent systems for their compressors must document and report on their operation. This includes maintaining records of each inspection, noting any emissions found, and recording the repair date or anticipated repair date if a fix is delayed.
- Performance-Based Standard: Alternatively, facilities can choose a performance-based standard for compressor seals. This approach requires tracking the total annual operating hours of each compressor and recording the results of any seal measurements. Any measurements exceeding the allowed threshold and the repair details (date and time) must be reported. If a repair is delayed due to parts availability, the entire process needs to be documented, including the reason for the delay and the anticipated repair date.
