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A Study Determining Asbestos Fiber Release During the Removal of Valve Packing James R. Millette and Michael D. Mount MVA, Inc., 5500 Oakbrook Parkway, Suite 200, Norcross, Georgia 30093 Asbestos packing material used in valves is generally considered to be a nonfriable material unless cut or torn. In a controlled, contained area within a steam power plant, personal and area air samples were collected be fore and during removal of asbestos packing material from valves that had been used at the plant. The results of this study show asbestos fibers can be released into the air during the generally used procedures for the removal of asbestos packing material. Air concentrations were measured by phase contrast microscopy in the range of 0.2 to 1.3 fibers/cc and by transmission electron micros copy in the range of 1.5 to 4.2 fibers/cc for all diameter fibers greater than 5 fim in length. Millette, J.R.; Mount, M.D.: A Study Determining Asbestos Fiber Release During the Removal of Valve Packing. Appl. Occup. Environ. Hyg. 8(9)790 -793; 1993. Introduction Most piping systems use valves to regulate the flow of fluids or gases within them. The valves, especially in indus trial facilities, may contain asbestos packing material that acts as a seal to prevent fluid or gas leakage as the valve is turned. Periodically the values must be repaired or rou tinely maintained by removing the packing and replacing it with new packing. In some steam plants, it is common practice to perform the removal and repacking of a number of valves at one time. This effort may involve several workers and take a number of days to complete. A literature search showed only one published study reporting on the release of asbestos fibers from packing material. Asbestos Packing Material According to the U.S. Environmental Protection Agency (EPA), asbestos packing means an asbestos-containing product intended for use as a mechanical seal in circum stances involving rotary, reciprocating, and helical motions, and which are intending to restrict fluid or gas leakage be tween moving and stationary surfaces. In a valve, the packing is compressed against the bore of the box by a gland that is tightened down on the packing (Figure 1). The packing is forced against the throat of the valve box and the packing conforms to the valve shaft surface, forming a tight seal. Compression packings are manufactured from various types of fibers, such as vegetable, animal, mineral (asbes tos) or synthetic, and twisted or braided with binders and lubricants. One of the most commonly used types of compression packing in valves is a graphite impregnated packing material that has the appearance of shiny, stiff rope. Packings are not considered friable asbestos-containing materials (ACM) because they are not easily crumbled into fine or dusty material by hand pressure. However, the EPA states that products such as packing may release asbestos dust if cut or torn. Study Design Asbestos-containing materials are common in industrial steam plants, and because a maintenance activity often in volves the disturbance of more than one material, it is diffi cult to assess the contribution, if any of a particular ACM to the overall airborne asbestos concentration. Valve packing removal, for instance, may involve the removal or at least disturbance of asbestos-containing pipe insulation or fit ting "mud." Therefore, to determine the possible contribu tion of valve packing only special precautions were taken to isolate this material from other activities that might have contributed airborne asbestos from other sources. Study Site The study was conducted in an unused steam power plant in Manchester, New Hampshire. The study team con ducted the valve packing removal tests after an asbestos abatement contractor had prepared a double containment area around two valves attached to the main power plant turbine. Prior to the studies, the abatement contractor pre pared the valves by removing all pipe insulation from the valve area and thoroughIvcleaningeachwaIve lira sepaiuie area of the plant, the abatement contractor also prepared a third valve that had been disconnected from the steam plant piping system by similarly removing all the pipe insu- 790 1047-322X/93/0809-790$6.00/4 1993 AIH APPL OCCUP. ENVIRON. HYG. 8(9) SEPTEMBER 1993 VALVE SHAFT FIGURE 1. Diagram of steam pipe valve containing packing. lation and cleaning the valve thoroughly. This valve was later moved into the containment for packing removal. The containment barriers in the area consisted of layers of poly ethylene plastic sheets on a wooden frame and 2 layers of polyethylene plastic on the floor. A containment area (5 X 7 ft) around the valves was completely contained within a larger containment area (7Yi X 11 ft) (Figure 2). The study area had two high efficiency particulate absolute air filtra tion devices (AFD) used to clean the air of particulate in cluding asbestos before each valve packing removal activ ity The inner area AFD was turned off during each phase of testing. The outer area AFD operated throughout the tests. Study Procedures The study consisted of the collection of air samples be fore and during valve packing removal activities. A retired steam plant maintenance worker/supervisor using his own tools performed the valve packing removal in the same way that he had in his previous years of work on industrial valves and as is often done in power plants today. Although some lubricating oil was used to loosen the packing, the work was generally done in a dry manner. Three packing removal tests were performed. The first two packing re moval activities consisted of opening valves connected to 4- to 6-inch diameter pipes and reaching in with a variety of tools to pull out three to four rings of the old packing. The third test utilized the same valve that had been opened in the second test and duplicated the packing removal activity More packing was removed under the same conditions as the second test. Pieces of the removed packing were placed in plastic bags and stored for analysis. The packing removed from both valves appeared to be graphite impregnated packing material that had a shiny gray-black appearance. Each packing removal activity occurred for approximately 30 minutes. The study site was cleaned between activities. Prior to starting each part of the study four area air sam ples were collected to determine the background level of asbestos in the air of the study area. The sampling cassettes were located on the walls at the breathing zone, 5 feet from the floor. A volume of720 to 840 L ofair was passed through each cassette at a flow rate of 15 L/min. Two area air samples FIGURE 2. Diagram of enclosure for valve packing removal study. APPL. OCCUP. ENVIRON. HYG. 8(9) SEPTEMBER 1993 791 were collected during the valve packing removal in the same locations as two of the background air samples, ap proximately 5 feet from the gasket removal activity One was collected at 7.5 L/min; the other at 15 L/min. The person doing the packing removal was fitted with two personal air sampling devices as was a person observing and photo graphing the activity These personal air samples were col lected at rates from 2 to 3-5 L/min. All personnel inside the study area were protected by air purifying respirators and complete head and body cover ings. The decontamination system consisted of a changing room outside the testing area, a shower room and a clean suit-up room. The decontamination system was used each time a person exited the study area and the overall contain ment area. Analytical Methods Air samples were analyzed by the standard phase con trast microscopy (PCM) method using the "A" counting rules. Although the phase contrast microscope enhances the analyst's ability to see fibers over other types of light micro scopes, the standard procedure does not involve identifica tion steps that specifically determine how many of the fibers counted are actually asbestos. Because packing ma terial is known to contain other types of fibers, some of the samples were analyzed by transmission electron micros copy (TEM) following the NIOSH 7402 preparation proce dure. The TEM analysis method identifies asbestos fibers on the basis of morphology, crystal structure and X-ray ele mental analysis. Although many shorter fibers were seen, only asbestos fibers longer than 5 /rm were counted. Polarized light microscopy was used to determine the type of asbestos in the samples of packing material re moved from the valves. A friability test was performed on samples of packing material that had been removed from valves as well as on some unused asbestos packing mate rial found in a storeroom at the steam plant. The friability test to determine whether or not an asbes tos-containing material will potentiallyrelease asbestos is a field test in which an attempt is made to crumble the ACM by hand. If the material can be crumbled by hand, it is con sidered friable. The EPA distinguishes friable from nonfriable ACM in their regulations on handling asbestos prod ucts. Friable ACM is considered more of a potential hazard than nonfriable material. Results The results of the air monitoring are shown in Table I. During the second valve packing removal activity, which lasted approximately one-half hour, the asbestos fiber level tor the person removing the packing was in the range of 1 fiber/cc, the Occupational Safety and Health Administra tion excursion level. Personal samples on the person nearby the packing remover collected over periods from 25 to 40 minutes were over 0.1 fiber/cc. The area samples collected TABLE I. Results of Air Monitoring Prior to and During Asbestos Packing Removal Sample Description Test 1 Area before packing removal Area before packing removal Area before packing removal Area before packing removal Sample Duration (min) 54 56 56 56 Air Volume (L) 810 840 840 840 Concentration (libers/cc) 0.006A 0.006* 0.006* 0.006* Personal packing remover Personal packing remover Personal observer Personal observer 25 50 Pump failure 25 87.5 25 50 0.2 NA 0.1 (0.1)B 0.2 Area during packing removal Area during packing removal 26 390 Filter damage 0.06 NA Test 2 Area before packing removal 57 855 0.006* Area before packing removal 56 840 0.009 Area before packing removal 56 840 0.006* Area before packing removal 56 840 0.006* Personal packing remover 31 93 Personal packing remover 31 62 Personal observer 31 62 Personal observer 31 93 1.0 1.3 0.9 0.6 (0.5)B Area during packing removal 24 180 0.4 Area during packing removal 25 375 0.3 Test 3 Area before packing removal 48 720 0.007* Area before packing removal 48 720 0.007* Area before packing removal 48 720 0.007* Area before packing removal 48 720 0.007* Personal packing remover Personal packing remover Personal observer Personal observer 33 66 33 99 39 117 39 78 0.4 (0.5)B 0.7 (0.7)B 0.2 0.2 (0.4)B Area during packing removal Area during packing removal 35 35 525 0.2 262.5 0.2 *At detection limit. "Quality control by second analyst. NA = not available. in the vicinity of the packing removal activity were elevated over the background levels in all three tests. The TEM analysis results are shown in Table II. Only as bestos fibers longer than 5.0 /im were recorded. Chrysotile fibers were identified as the primary type of fiber. It is gen erally considered that fibers thinner than 0.25 fim would not be resolved by the light microscope used in the PCM method. Therefore, two TEM asbestos concentrations are listed. One ofall asbestos fibers greaterchan 5 -/n, and oncwhich includes only those fibers over 5 jim in length and also greater than 025 /tm in width. The latter value is con sidered a PCM equivalent count because these fibers counted in the TEM should be roughly equivalent to what would be counted under the PCM. The used packing, removed from the valve, was friable. Polarized light microscopic analysis showed it to be ap proximately 85 percent chrysotile, while the bulk of the re- 792 APPL. 0CCUP. ENVIRON. HYG. 8(9) SEPTEMBER 1993 TABLE II. Transmission Electron Microscopy Results on Personal Air Monitoring Samples During Packing Removal Asbestos Concentration (fibers/cc) Sample Description Test 2 Personal packing remover Personal packing remover Test 3 Personal packing remover Personal packing remover All > 5/im 2.2 4.2 1.5 2.1 PCM Equivalent1 1.5 2.6 1.2 1.5 'Phase contrast microscopy equivalent by transmission electron microscopy counting. Asbestos libers or bundles greater than or equal to 5gm in length and at least 0.25pm in width (3:1 aspect ratio). maining material was carbon. Similar looking unused as bestos packing found in the storeroom of the power plant was not friable. In an additional test, a piece of the unused packing was subjected to heating at 400C for 1 hour in a muffle furnace. The packing became friable after the treat ment by heat. Conclusions Asbestos packing, although not friable in original, un used condition, can become friable after use in valves and can release asbestos fibers into the air during valve packing removal operations. The levels of asbestos detected in the air were similar to the levels reported previously for valve packing activities and in some instances involving gasket removal activities.(7) Recommendations The results of these tests suggest that asbestos packing material, although not identified as a friable ACM, should be considered as such during packing removal activities. If possible, the packing should be wetted with water or oil before it is cut and torn with packing tools such as hooks during the procedures for removing old packing. References 1. McKinnery, W.N.; Moore, R.W.: Evaluation of Airborne Asbestos Fiber Levels During Removal and Installation of Valve Gaskets and Packing. Am. Ind. Hyg. Assoc. J. 53(8):531 -- 532 (1992). 2. U.S. Environmental Protection Agency: Title 40, Code of Federal Regulations, Part 763. Asbestos: Manufacture, Importation, Pro cessing and Distribution in Commerce Prohibitions; Final Rule. Fed. Reg. 54(132)(July 12, 1989). 3. Nelson, C.A.: Millwrights and Mechanics Guide, p. 236. McMillan Publishing Co., London (1986). 4. U.S. Environmental Protection Agency: Asbestos Waste Manage ment Guidance. EPA-530/SW-85-007. Office of Solid Waste, Wash ington, DC (May 1985). 5. Carter, J.W.; Taylor, D.G.; Baron, P.A.: Method 7400. In: NIOSH Manual ofAnalytical Methods, p. 7400-1-7400-8. National Institute for Occupational Safety and Health, Cincinnati, OH (1984). 6. Carter, J.W.; Baron, P.A.; Taylor, D.G.: Method 7402. In: NIOSH Manual ofAnalytical Methods, p. 7402-1 - 7402-7. National Institute for Occupational Safety and Health, Cincinnati, OH (1987). 7. Cheng, R.T.; McDermott, H.J.: Exposure to Asbestos from Asbestos Gaskets. Appl. Occup. Environ. Hyg. 6:588-591 (1991). Received 8/27/92; review decision 12/3/92; revision 11/19/92; accepted 01/28/93 APPL. OCCUP. ENVIRON. HYG. 8(9) SEPTEMBER 1993 793