First of Two Parts
Operators in refineries or chemical/petrochemical plants must keep greenhouse gas (GHG) and environmental regulations for fugitive emissions in mind. One area in which this is extremely important is the processing of oil sands in Canada.
Fugitive emissions are any chemical in physical form that can leak unanticipated within an installation. Knowing how to select valves that will meet or exceed volatile organic compound fugitive emission limits is critical. The costs are exorbitantly high if an operator fails to meet the requirements.
End users should obtain test data that will allow for direct comparisons between valve packing, gaskets and other sealing components. Without data, end users are guessing which options are best for their applications. The operations/field data, including past experience, helps analyze the valve and packing options.
Most companies require real-time testing, which will provide comparable fugitive emissions in parts per million (ppm) of hydrocarbons and chemicals. These tests include multiple test cycles that represent the plant conditions within a laboratory. These tests can be conducted at reasonable costs and within a reasonable timeframe.
A few laboratories in North America are qualified and have developed a simple test procedure that can be adjusted to accommodate any off-the-shelf valve and provide the fugitive emissions in ppm, which is needed to understand how a valve will perform once it is in service.
Part One of this series discusses how to eliminate fugitive emissions in valves already in service. Part Two will cover the current standards and testing procedures to ensure compliance with these standards.
Why Focus on the Fugitive Emissions of Valves?
The industry statistics indicate the importance of discussing the fugitive emissions of valves specifically. Valves account for more than 51 percent of fugitive emissions, and GHGs are part of this (see Figure 1).
Figure 1. Sources of fugitive emissions
Compliance standards should be created by valve manufacturers that minimally include the following:
- Design of sealing components
- Selection of materials
- Prototype qualification of valves
- Production test of valves
- Fugitive emission compliance onsite
To maintain consistency, each standard should be quality checked. If any anomalies occur, the whole test cycle must be repeated. The steps to eliminate or limit valve fugitive emissions that can lead to global warming include leak detection and repair and basic control and monitoring strategies.
Leak Detection and Repair
The U.S. Environmental Protection Agency (EPA) aggressively pursues fugitive emission violations. It requires Method 21 Department of Energy (DOE) monitoring of valves, and it mandates the repair of leaks. To minimize hazardous or toxic air pollutant emissions, the EPA also mandates the use of low emission (Low-E) valves or Low-E packing.
Valves and packing are considered Low-E if they have the following characteristics:
a) They are type tested (by the valve/packing manufacturer) and have a written warranty not to leak above 100 ppm. The manufacturer will replace the valve if it emits above this limit at any time during the first five years.
b) They are type tested and did not leak more than 500 ppm and, on average, leaked less than 100 ppm.
c) Valves that are extensions of the qualified types above, provided temperature, pressure and all major characteristics affecting the valve sealing performance are the same, are also considered Low-E.
The requirements and standards for testing will be covered in Part Two.
The key elements for effective, long-term control of fugitive emissions are:
- The application of the best available technology and standards, including the development of monitoring programs, operating procedures and performance objectives for controlling fugitive emissions Implementation of management systems
- Corporate commitment to the implementation and maintenance of a directed inspection & maintenance (DI&M) program to detect and prevent leaks
- The first step in controlling fugitive equipment leaks should always be to minimize the potential for leaks at the beginning by applying proper design and material-selection standards, following the manufacturer’s specifications for the installation, using and maintaining the components, and implementing practical control technologies (such as reduction, recovery and treatment systems).
A management system is needed to establish objective performance targets and to implement ongoing monitoring and predictive maintenance programs to ensure that leaks are detected and remain well controlled.
The first step is to determine which types of components will be targeted for regular leak screening. The objective is to minimize the potential for leaks in the most practical way possible. This is accomplished by focusing the efforts on the types of components and service applications most likely to offer significant cost-effective control opportunities. Non-target components are subjected to coarse or less frequent screening.
Typically, a facility will phase in the DI&M program across a certain number of years by progressively adding to the list of targeted components until all key components are targeted. Once a leak is detected, regardless of whether it is a target or non-target component, the decision must be made whether to repair the leak.