new source. Plants subject to valve stem LDAR requirements generally adhere to the following program on a quarterly or annual

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2 There is a new criterion on the horizon for selecting and maintaining valves: stem leakage. Not the stem leakage criteria of the past, which was often no more stringent than the attitude if you can t see it or smell it, it s not leaking. Because of the 1990 Clean Air Act (Table I), many plants will face frequent valve stem leak monitoring and the elimination of even the slightest leak. This will lead to changes in valve selection and repair procedures to minimize monitoring and repair costs. Fugitive emissions Valve stem leaks are a major component of a large category of air pollution sources called fugitive emissions (Figure 1). Encompassing a wide range of non-point sources, including leaks from valves, pumps and gaskets, as well as evaporation from sewers and waste treatment facilities, fugitive emissions account for approximately one-third of all air pollution. Fugitive emissions are regulated today in some plants, in some parts of the country. But the patchwork of federal and state regulations can vary depending on the air quality of the region, the type of chemicals being handled, and whether the facility is classified as new. The new Clean Air Act will change all that (Table 2). Most large chemical plants will soon have to monitor valve stem leakage on a regular basis and make quick repairs. And if too many leak, they ll have to monitor and repair the valves more frequently and/or implement a government-regulated valve quality program. Present regulations Leak Detection and Repair (LDAR) programs for valve stems aren t new to the chemical process industry. They have been used on a limited basis since 1975 and are practiced primarily in two circumstances. First, some states require LDAR in non-attainment areas - regions of the state where the ambient air quality does not meet federal standards for protecting human health and welfare. These tend to be metropolitan regions heavy with industry and auto trafic. Second, the federal EPA requires an LDAR program for valves in toxic service. But even though the EPA was authorized to identify toxic air pollutants and regulate their emission more than 20 years ago, only two organic chemicals have b<en listed as toxic - benzene and vinyl chloride. Many new and modified facilities also require LDAR for valves in chemical service. But, whether for economic reasons or to avoid applying costly New Source Performance Standards, few companies build or modify chemical facilities to fall under the category of a new source. Plants subject to valve stem LDAR requirements generally adhere to the following program on a quarterly or annual basis: Identify valves requiring LDAR. Unless the plant is new, this generally includes valves in volatile organic chemical service if the plant is in a non-attainment area. Otherwise, LDAR is required only for valves handling vinyl chloride or benzene. (Coke ovens and coke chemical operations, because of the high benzene content of their process streams, are included in the benzene regulations.) At the required frequency, the air around the valves is sniffed using a hydrocarbon detector. If the hydrocarbon detector detects a concentration greater than 10,000 ppm, the valve is identified as a leaker and repair is required. The new requirements Requirements for the Clean Air Act s Recent legislation and EPA regulations are increasing the importance ojstem seals in the selection of process valves. by Meredith ~ j l l ~ ~ Figure I. Valve stem leaks are a major source of fugitive emissions, which account for about one-third of all air pollution. DECEMBER POLLUTION ENGINEERING 81

3 POLLUTION ENGlNEERiNG valve stem LDAR were developed much earlier than That s because the EPA anticipated the nature of the new law and solicited the help of industry and environmental groups to negotiate the regulations. As a result, the regulations are all but certain to be promulgated in their present form. The regulations should also survive any possible court challenges with little or no significant changes. Even if procedures within EPA and other agencies delay promulgation, it is expected that the regulations will still be imposed, albeit using different administrative procedures. This means plants can prepare LDAR programs confident the regulations will indeed take effect in their present form. Although the new requirements for controlling fugitive emissions also encompass gaskets and pumps, regulations on valves will have the greatest impact on emissions and on plant maintenance programs. First, there are about 15 to 20 times more valves in a typical chemical plant than there are pumps. Second, the potential for leakage from the static seal in flange faces is so much less than from valves or pumps that continuing and frequent monitoring programs generally will not be required. Specifics The 1990 Clean Air Act and the EPA Plants can prepare LDAR programs conjident the regulations will take effect in their present form. regulations supporting it will expand and tighten present requirements for monitoring and repairing fugitive emissions from equipment leaks. The number of volatile organic chemicals regulated will immediately increase from two (vinyl chloride and benzene) to 149. This list includes many common materials, such as chlorobenzene, methanol and methyl chloride acid, as well as phosgene, dioxin and other more lethal chemicals. The threshold for identifying a valve stem as a leaker will decrease from 10,000 ppm to only 500 ppm (Figure 2). And, third, states will have to do more in their non-attainment areas than just prevent the air from getting worse. They must apply stringent measures to ratchet down emissions, including reducing fugitive emissions from existing valves. The new valve LDAR regulations consist of a four-step procedure. First, it must be determined if and when the plant, process unit and valve are covered by LDAR regulations. Second, beginning six months after promulgation in early 1992, sniff each covered valve once each quarter. (The requirements for sniffing methods and equipment are described in detail in EPA document , Protocols for Generating Unit-Specific Emission Estimates for Equipment Leaks of VOC and VHAP. ) Third, if the level of contamination detected is greater than the threshold, repair the valve. The threshold level initially will be 10,000 ppm; after oneyear, the threshold will drop to 500 PPm. Fourth, after another year and a half, increase or decrease LDAR frequency depending on the number of valves leaking above the threshold level. If the number of leakers is less than I percent, LDAR frequency can be cut to semiannually; if less than 0.5 percent, LDAR can be cut to annually. But, if the number of leakers exceeds 2 percent, then LDAR must either be increased to monthly or the plant must institute a government-mandated valve quality improvement program. These regulations will apply under any of three categories - hazardous, non-attainment, or new source. If not, the Federal LDAR regulations will not apply, but each state may impose its own LDAR requirements. To fall under the hazardous category, all of the following criteria must be met: The valve is intended to operate in hazardous service for more than 300 hours or more in a year. The specific process is listed by the EPA in one of their five groups of covered processes. About 450 spe- Original Clean Air Act applies 10,OOO ppm LDAR No additional source categories (industry may elect to monitor Phase I Phase II Phase 111 Additional source Starts one year after Starts years after categories begin group applicability date group applicability date Starts on group New screening value ppm LDAR applicability date 500 ppm LDAR Options for monthly 10,000 ppm LDAR Quarterly monitoring monitoring 8, QIP Quarterly monitoring Rule proposal - Federal Register Publication Promulgation 82 POLLUTION ENGINEERING DECEMBER 199 1

4 Q cific processes will be covered eventually; they will be phased in in three month intervals. The specific valve must carry a fluid that contains at least 5 percent of designated hazardous materials. To fall under the non-attainment category, the plant must be located in a region where ambient air quality is substandard. To fall under the new source category, the plant or process unit must be classified as new according to EPA rules. Financial impact The new LDAR regulations for valves are unusual in that the threat of fines isn t the primary incentive to reduce emissions. Rather, frequency of monitoring is determined by the number of valves that leak; thus, the incentive is to reduce the frequency of LDAR to avoid or minimize manpower and record-keeping costs. An indication of LDAR costs is provided by one of the nation s largest oil refineries. An LDAR program was mandated several years ago because the plant is in a non-attainment region. Presently, only a portion of its units are required to have valves monitored. Most of the valves require only annual monitoring, and the threshold leak rate is a generous 10,000 ppm. Yet the cost of the valve LDAR program approaches $400,000 annually. Typical of many process plants, valves in the refinery constitute about 85 percent of the fugitive emission sources from equipment, and 85 percent of these valves are 2 inches or smaller. Because a valve s potential for leakage depends on the stem diameter and the line pressure, not the line size, even a small valve can be a major emission source. When the refinery instituted an LDAR program 8 years ago, more than 10 percent of their valves produced stem leakage in excess of the 10,000 ppm threshold. Now, about 50,000 valve tests are performed each year, with about 4 percent of the valves failing the test, even after the testing crew attempts to tighten the packing. The total costs for testing, record keeping, repairing the leaking valves and reporting amount to about $7 per valve. As the new regulations are phased in, many more of the refinery s valves will be subject to LDAR, and quarterly rather than annual monitoring will be the norm. This could increase annual LDAR costs to more than $2 million. If a plant has less than 250 valves it need not perform LDAR monthly, even if more than 2 percent of its valves leak. If up ta 1 percent of the valves in a plant are noa-repairable because of their design or location, they need not be included in determining LDAR frequency. Ib determine whether to switch to monthly, quaflerly or semi-annual LDAR, the average number of leakers for the last two measuring periods is used as the qfiteria. (However, changing to or fm m annual LDAR requires an average of three out of In lieu of required monthly LDAR, a plant may elect to implement a three-year, governmentmandated quality improvement plan. In the first year, the plant collects detailed information on valve performance, equipment specs and maintenance methods. In the see ond, it uses data it has collected to plan and begin trial studies on lowleak equipment. It develops and applies purchasing, quality assurance and maintenan% programs for equipment in the third year. Figure 2. The threshold to identify a valve stem as a leaker will drop from 70,000 ppm to 500 ppm. By reducing the number of valves leaking above the threshold level to below 1 percent, monitoring frequency could drop to twice a year and thus cut annual LDAR costs by $1 million. A further reduction to 0.5 percent leakers could cut yearly LDAR costs by an additional $400,000. Reducing monitoring costs isn t the only potential benefit; savings from preventing product loss is another. The EPA estimates that a typical valve in light hydrocarbon service now leaks at the rate of kg per hour. Thus, a single valve will lose about 100 pounds of product per year. If the lost material costs 20 cents per pound, each valve could be losing $20 a year in material. Strategies Reducing valve stem leakage requires a three-part strategy of valve selection, maintenance and retrofitting. Since sliding stem seals are often more prone to leakage than rotary seals in the same application, many plants may turn to quarter-turn valves (ball, plug, butterfly and rotary control) to reduce emissions and the required frequency of LDAR. However, it is economically impractical to replace all existing rising stem valves with rotaries, and for many applications a quarter-turn or rotary con- DECEMBER POLLUTION ENGINEERING 83

5 . POLLUTION ENGINEERING Reducing valve stem leakage requires a three-part strategy of valve selection, maintenance and retrofitting. Figure 3. Some new packing systems can eliminate leakage for many applications. trol valve will not provide the required process performance. Also, for severe service applications such as high temperature, high pressure, high pressure drop or frequent thermal cycles, it can be more difficult to effect a tight, longlasting stem seal with a rotary valve than with a sliding stem valve. A bellows stem seal, of course, can provide an essentially zero-leak valve. However, bellows seals can be quite expensive and have a limited life. Most bellows eventually fail due to metal fatigue, which is difficult to predict, however, because it depends on the frequency and distance of movement of 84 POLLUTION ENGINEERING DECEMBER I99 1 the bellows. Service life can also be limited by corrosion on the thin metal walls of the bellows. Newly available packing systems can, or many applications, provide nearzero leakage for either rotary or sliding stem valves (Figure 3). Expanded graphite packing, while more sensitive to installation procedures than the asbestos it replaces, is compatible with most process fluids, applicable for high temperature applications and fire safe, and can provide low leak rates and long life when properly applied to the particular valve. Live loaded packing can further im- prove on the performance of graphite packing. Using springs, such as belleville washers, to maintain a constant force on the packing, live loaded systems don t depend on resiliency of the packing material and frequent tightening of the packing gland to produce a good seal. Polytetrafluoroethylene (PTFE) packing material, although less expensive than graphite, must be used with caution in many applications since it tends to cold flow. Anticipating the increased need for long-life, low-leak valve stem packing, valve and packing manufacturers have developed complete valve packing retrofit systems. These systems utilize anti-extrusion rings to retain the PTFE, minimizing the tendency for cold flowing and extrusion, thus maintaining the integrity of the seal. Control valves can provide special challenges to preventing stem leakage. Control valves are stroked more frequently than most other types of valves, resulting in a greater potential for wear on packing and more fatigue on bellows seals. In addition, today s microprocessor-based controls can be tuned so tightly that a control valve can be in a constant, low-amplitude hunting motion, further reducing packing and bellows life. Although control valves constitute only about 5 to 10 percent of the valves in a typical chemical plant, their greater potential for leakage mandates that they be given extra attention in selection and maintenance. By concentrating valve selection and maintenance efforts on minimizing stem leakage, chemical plants will be able to minimize LDAR costs while decreasing product losses. This will require advance leak testing of existing valves, studies and tests of new valves, and testing of retrofit packing techniques or products for those existing valves that have poor LDAR performance. Meredith Miller is marketing manager for the Chemical Industry Group of Fisher Controls, Marshalltown, Iowa Reader Interest Review Please circle the appropriate number on the Reader Service Card to indicate your level of interest in this article. High 456 Medium 457 Low 458