For petroleum refineries, gas plants, chemical plants and other operations subject to either a New Source Performance Standard (NSPS) or National Emission Standard for Hazardous Air Pollutants (NESHAP), minimization of fugitive emissions is likely part of the compliance regimen. Typically, these facilities are subject to some monitoring of valves, pumps, compressors, and other applicable equipment using either the Environmental Protection Agency’s (EPA)Method 21 (monitoring using instrumentation) or audio, visual, olfactory methodology. The primary key is to reduce the potential fugitive emissions of volatile organic carbons (VOCs) and hazardous air pollutants (HAPs).
The underlying regulation that most facilities are subject to is Subpart VV or VVa of the NSPS, i.e. Standards of Performance for Equipment Leaks of VOC in the Synthetic Organic Chemicals Manufacturing Industry. For the purposes of this discussion, Subpart VV is referenced. Under the definitions section, an open-ended valve or line means any valve, except safety relief valves, having one side of the valve seat in contact with the process fluid and one side open to the atmosphere, either directly or through open piping. This means that there needs to be a second block between the valve or closure in contact with the process fluid and the atmosphere, hence a valve and a plug or a double-block and bleed.
The reason for this is twofold. The first is common sense, i.e. an element of safety has been put into place between the process and the atmosphere. Thus, it does not matter whether or not the process fluid is subject to additional regulation, the owner/operator wants to keep the material in the pipe to prevent a safety or environmental incident. The second is related to EPA’s contention that VOC emissions through open-ended lines account for between 5and 10% of VOC emissions. (EPA’s LDAR Best Practices Guide http://www.epa.gov/compliance/resources/publications/assistance/ldarguide.pdf).
The standard or prohibition for open-ended lines can be found in 40 Code of Federal Regulations (CFR) 60.482-6. In this section, it is designated that for equipment in the applicable service that each open-ended valve or line shall be equipped with a cap, blind, flange, plug or second valve. (Although, there are exceptions for autocatalytic polymerizing materials, or other safety considerations.) It should be noted that there is no distinction for gas/vapor, light liquid, or heavy liquid material. Thus, if the equipment is in VOC service, open-ended lines are prohibited.
Open-ended lines have been troublesome for many facilities. EPA has included open-ended line provisions in many of the refinery and chemical consent decrees. Similarly, States and other jurisdictions have also placed an emphasis on open-ended lines.
While open-ended lines are generally easy to recognize, i.e. a valve at the end of the pipe that does not have a second closure; there are some instances where an open-ended line may not be as obvious. For example, a valve that is well removed from the end of the piping, sampling system configurations, and quills for drill-and-tap or other repairs.
Drill-and-tap is a repair method where a hole is drilled into the equipment being repaired for the injection of additional packing. This methodology is used to repair a valve, i.e. to prevent leaking above a threshold value. The quill used for the drill-and-tap is essentially a small valve that a packing gun can be attached to facilitate the injection of the packing. Thus, the quill is equipped with ports. These ports are general closed with a plug after the packing injection is completed. The question becomes if these plugs are not in place after the packing operation, are they considered an open-ended line? There have been mixed interpretations regarding this. From a very conservative point of view, the quill is now considered part of the valve and hence will be monitored, and the plugs on the quill have essentially the same function as plugs on other areas of the valve. Therefore, a missing plug on the quill needs to be treated in the same manner as a missing plug on the valve, i.e. it should be in place. A quick search of the available applicability determinations on the EPA website, does not reveal any specific determination by EPA about the status of missing plugs on quills, but it is clear that EPA has a focus on open-ended lines.
Open-ended lines are a challenge to facilities subject to leak detection and repair requirements. Minimization/elimination of open-ended lines requires the attention of all plant personnel not just those charged with the day-to-day LDAR monitoring and tracking. Managing open-ended lines requires constant diligence and cooperation.