August 2021

Special Focus: Valves, Pumps and Turbomachinery

Keeping fugitive emissions costs down with low-E valves

Fugitive emissions have become an increasingly critical area of interest for chemical processing and refining facilities.

Hunsicker, S., Swagelok

Fugitive emissions have become an increasingly critical area of interest for chemical processing and refining facilities. If left unmitigated, these uncontrolled leaks can be detrimental to a facility’s bottom line—and not just in the form of lost system gases that can lead to waste. Fugitive emissions can also lead to fines if the facility is found to be noncompliant with current emissions regulations.

With the U.S. Environmental Protection Agency (EPA) and other regulatory bodies reaching agreements with companies to reduce fugitive emissions, it is imperative to increase understanding of these potentially costly leaks and to understand how to mitigate them within a plant’s fluid systems. Being proactive is critical, as part of the solution may require altering supply chains and upgrading systems. This article explores some essential strategies for actively addressing fugitive emissions to help reduce leaks, maintain compliance and keep costs low.

Fugitive emissions essentials

Fugitive emissions most often result from leaking process equipment, leading to the unwanted escape of volatile organic compounds (VOCs). These VOCs can include, but are not limited to gases such as benzene, methane and isopentane. When released, these substances endanger air quality and form ozone, which is why governmental regulatory bodies aim to control fugitive emissions. Plants that violate emissions regulations can have large fines levied on them, so it pays to remain in compliance (FIG. 1).

FIG. 1. The presence of bubbles during a leak test can reveal fugitive emissions escaping from valves. Technicians should be trained to decide whether to tighten or replace the fitting connection.

Often, the major sources of fugitive emissions—accounting for nearly 62% of the release of uncontrolled VOC emissions at a typical plant—are the dynamic and static seals on valves, pumps and flange connections. To combat fugitive emissions, facilities can install low-emissions (low-E) valves, which testing has proven will conform to low emissions standards. Sometimes, purchasing low-E valves is even mandated under a consent decree between the EPA and a processing plant, often as the result of a civil case.

EPA consent decrees

The role of the EPA in enforcing environmental requirements, laws and regulations (including U.S. laws like the Clean Water Act and the Clean Air Act) is clear. When voluntary compliance is impossible, the EPA can turn to the courts to make sure that plants comply with the applicable laws and/or regulations.

For chemical plants and refineries, the most common enforcement mechanism that the EPA will use is called a consent decree. A typical consent decree requires plant owners and operators to take specific actions to improve their fugitive emissions problems within a specified amount of time. If a plant does not meet these requirements, then civil penalties—including heavy fines—often follow.

Although refineries and processing plants have many available avenues to mitigate fugitive emissions, consent decrees will often require a plant to establish an enhanced leak detection and repair (LDAR) program. They can also mandate that the plant uses low-E valves in the future.

Enhanced LDAR tactics and low-E valves

Rigorous LDAR strategies are designed to mirror the leak detection and oversight methods that the EPA uses. In the case of valves, EPA audits include paper audits and field testing to quantify the levels of fugitive emissions. Once the leaks are identified, the plant will usually implement one or a combination of the following methods to reduce fugitive emissions levels:

  • Institute a comprehensive plan whereby leaks are identified through in-situ testing of valves and other connections using EPA Method 21
  • Identify, document and repair leaks within a defined time frame
  • Lower allowable leak limits for valves, connections and pumps.

Improved LDAR strategies often also include the stipulation that any new valves installed must be low-E valves. Interestingly, there is often no single specified method for determining what a low-E valve is in the EPA consent decrees—that determination is left up to the processing plant or refinery in question. In most cases, there are several options for deciding what a low-E valve is, and it frequently encompasses the plant accepting one of the two following methods for classifying valves as low-E:

  1. A written guarantee that the valve will not leak above 100 parts per million (ppm) for 5 yr
  2. A written guarantee, certification or equivalent documentation stating that the valve has been tested pursuant to generally accepted good engineering practices and has been found to be leaking at no greater than 100 ppm.

It can be challenging to understand the difference between those two options, so the following will examine them in greater detail, highlighting both the advantages and disadvantages of each.

Written guarantee by the manufacturer

To document the purchase of low-E valves, a plant could have the manufacturer provide a written guarantee that the valves will not leak more than 100 ppm for 5 yr. However, the problem with this idea is that the plant operator needs to think about what will happen if the valves do leak. Will any compensation be involved, or will the manufacturer simply replace the leaky valve? Can the plant operator recoup the costs associated with the valve replacement?

If the leakage incident triggers an EPA-levied fine (which can often be as high as $10,000/d per incident), what recourses would the plant operator have to cover all the costs involved? Would the manufacturer cover these costs, as well? Many uncertainties are involved with a manufacturer’s guarantee, especially when tests exist that can reveal if valves are working as promised.

Low-emissions testing

Industry associations like the American Petroleum Institute (API) and the International Standards Organization (ISO) have developed actual tests to certify valves as “low-emissions” equipment. These tests include the following:

  • API 624, Type Testing of Rising Stem Valves Equipped with Graphite Packing for Fugitive Emissions: This test covers rising stem valves, using methane as the test media. The valve must perform 310 cycles, along with three thermal cycles (where the valve is tested at ambient temperature, at an elevated temperature, and then again at ambient temperature), with a leak rate under 100 ppm methane.
  • API 641, Testing of Quarter-Turn Valves for Fugitive Emissions: This testing involves ball valves, using methane as the test media. Each valve tested must perform 610 cycles, along with three thermal cycles, with a leak rate of less than 100 ppm methane.
  • ISO 15848-1, Industrial Valves—Measurement, Test and Qualification Procedures for Fugitive Emissions: This standard provides the procedures and requirements for the mechanical and thermal cycle testing of valves, with leak tests at various points. Methane or helium is used as test media.

Unlike the uncertainty involved in standard manufacturers’ guarantees, the API’s test results are simple to discern: They are either pass or fail, meaning that the valve is clearly delineated as low-E or not. However, those purchasing low-E valves should understand that the ISO test methodology is more complicated, with different “class” ratings that reflect how the valves perform during testing.

For example, ISO standards allow class ratings of valves as low-E that do not meet the “100 ppm or less” threshold that the EPA requires. Tightness Class CM, for example, can mean that a valve can leak more than 100 ppm methane, but less than 500 ppm methane.

In addition, the ISO 15848-1 standard states that there is no correlation intended between tightness classes when the test fluid is helium (classes AH, BH and CH) and when the test fluid is methane. In part, this is because the data collected is different depending on which fluid is used. For helium, ISO reports the results as the leak rate proportional to the stem diameter in atmospheric cubic centimeters per second (atm cm3/sec). Since it is not reported in the more traditional “ppm” metric, this makes it difficult to determine whether the valves comply with the EPA’s “100 ppm or less” standard if helium is used. Unfortunately, it is impossible to convert atm cm3/sec to ppm because no formula exists.

Finally, third-party laboratories should conduct the tests, instead of the valve manufacturers themselves. Plant operators can feel confident that tests handled by independent third parties are not biased in any way. Therefore, manufacturers should provide valve certifications that include a seal from the third-party lab, along with the testing location and the results.

Get ahead of emissions requirements

Valves that are certified as “low-E” are ideal to reduce fugitive emissions, whether they are being specified for a new system or being added to enhance an LDAR program. Installing low-E valves before the EPA finds high fugitive emissions levels can save processing plants significant money in the long run by avoiding costly refits (FIG. 2). The valves also allow facilities to remain compliant with current environmental best practices. Therefore, it is helpful to ensure that plant personnel know which valves to order for low-VOC service, so that the plant can maintain operational and environmental integrity. When assistance is needed in determining what low-E solutions might work best for specific applications, it is best to consult with an experienced fluid system specialist to secure third-party-tested solutions that will keep the facility in compliance. HP

FIG. 2. Installing low-E valves before the U.S. EPA finds high fugitive emissions levels can save plants significant money in the long run by avoiding costly refits.

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