Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link


Centers for Disease Control and Prevention. CDC twenty four seven. Saving Lives, Protecting People
Search
            ×
                        Mining
                        Mining
                            NIOSH
                            All CDC
                    Submit
                For a full list of topics:A-Z Index
                Advanced Search
            Advanced Search


The National Institute for Occupational Safety and Health (NIOSH)


Section Navigation
			
			CDC Home





Mining Publication: Technology News 490 - An Inexpensive Device for Monitoring Explosions in Sealed Areas of Underground Mines
Keywords: Explosions Gobs Monitoring Pressure Pressure measurement instruments
Original creation date: June 2001
Authors: National Institute for Occupational Safety and Health
Technology News - June 2001
Download PDF Document (0.28 MB)
NIOSHTIC2 Number: 20021624
U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Technology News 490, 2001 Jun :1-2
The objective of this study was to develop a passive, inexpensive technique for monitoring explosion overpressures within sealed areas in underground coal mines. From 1994 to 2000, seven explosions of methane and/or coal dust occurred within the worked-out, sealed areas (gobs) of underground U.S. coal mines. These explosions, believed to have been started by lightning, destroyed many seals and caused much damage external to the sealed area. One gob explosion went undetected until the mine operator reopened the sealed area and discovered the damage. Fortunately, these gob explosions did not cause any fatalities or injuries. Because lightning occurs in just about all mining areas, several questions arise. Could gob gas explosions be occurring in other sealed areas and going undetected? If so, what is the magnitude of the resulting explosion overpressures? The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) undertook a study to identify and evaluate passive measuring devices to monitor and quantify the overpressures associated with such explosions. This work was done in parallel with full-scale explosion experiments for evaluating the strength characteristics of seals used for isolating areas in underground coal mines. Evaluation studies were done in PRL's 20-liter explosion test chamber and in the full-scale Experimental Mine at Lake Lynn Laboratory to evaluate the response and accuracy of various commercially available automobile tire pressure gauges to overpressures generated from gas and dust explosions. The first series of tests was done in the 20-liter chamber, which is used to study the explosibility and inerting of fuel dusts and gases. Data from the tire pressure gauge tests were compared to the pressure-time data obtained from the 20-liter chamber 's traditional electronic strain gauge pressure transducer recorded on a high-speed data acquisition system. To evaluate the tire pressure gauges, the valved inlet (tip) of the candidate pressure gauge was removed and the body of the gauge was cemented with epoxy into a 0.25-in pipe elbow and attached to the outside of the test chamber. A second series of tire gauge evaluation tests was done at Lake Lynn during explosion-resistance testing of seals used in underground coal mines. Full-scale seals (20 ft wide by 8 ft high) were constructed as one wall of a 2,000-ft 3 chamber and exposed to a series of methane explosions. Average overpressures ranged from 20 to 80 psi. The seals were built with various strength materials ranging from 7 to 48 in thick. The modified tire gauges are attached on the outside of the chamber to a 0.25-in NPT pipe that extends into the chamber (figure 1). The axis of the gauge is mounted at a right angle to the plane of the seal to minimize the coupling of any seal movement to the stem of the gauge that may cause inaccurate readings. The internal explosion pressure history is recorded with a strain gauge pressure transducer mounted inside the chamber. Methane is injected into the chamber, mixed with air, and ignited with an electric spark located at the geometric center of the chamber. Maximum explosion overpressures are recorded and compared with the tire gauge pressure. Several constant volume explosions were conducted in the 20-liter chamber in order to vary the maximum pressure and the time-to-peak pressure. The comparison between the maximum pressure measured by the strain gauge and that determined by the tire pressure gauge is shown in figure 2. There is fairly good agreement over the pressure range from 5.9 to 18.7 psi. Maximum pressure comparisons from large-scale chamber tests are also very encouraging. Maximum pressures recorded with internal electronic strain pressure gauge agreed within 1 psi of the tire gauge reading for all tests without seal failure. Results show that this simple, in- expensive, passive device can be used to monitor overpressures contained within sealed areas of underground mines or to record the gob explosion overpressures if one or more seals fail during the explosion. For in-mine use, a single pressure gauge could be installed on one seal in a set of two to six seals. If desired, two gauges covering different ranges could be attached to the same seal. Existing sampling tubes could be used to attach the gauge where seals are already built. During the construction of a new seal, a dedicated or additional 0.25-in-diam pass-through tube could be installed. Any pressure rise can be identified during routine weekly examinations of the seals or shortly after a lightning strike in the area. Such an inexpensive device is useful as part of a surveillance study on the number and magnitude of undetected explosion events that occur in sealed areas of underground coal mines.
Image of publication Technology News 490 - An Inexpensive Device for Monitoring Explosions in Sealed Areas of Underground MinesTechnology News - June 2001
Download PDF Document (0.28 MB)
NIOSHTIC2 Number: 20021624
U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Technology News 490, 2001 Jun :1-2
See Also
Detonation Wave Propagation in Underground Mine Entries
Evaluation of Explosion-Resistant Seals, Stoppings, and Overcast for Ventilation Control in Underground Coal Mining
Explosion Pressure Design Criteria for New Seals in U.S. Coal Mines
Methane-Air Detonation Experiments at NIOSH Lake Lynn Laboratory
Mobile Roof Support Load Rate Monitoring System
Modeling the Effect of Barometric Pressure Changes on Spontaneous Heating in Bleederless Longwall Panels
Rapid (Grab) Sampling During Full-scale Explosions - Microscopic and Analytical Evaluation
Relationship Between Radiated Seismic Energy and Explosive Pressure for Controlled Methane and Coal Dust Explosions in an Underground Mine
Remote Gob Gas Venthole Monitoring and Cellular Telephone-Based Real-Time Data Transmission System
Technology News 489 - Reducing the Danger of Explosions in Sealed Areas (Gobs) in Mines
Page last reviewed: September 21, 2012
Page last updated: September 21, 2012
Content source: National Institute for Occupational Safety and Health, Mining Program
Facebook
        Twitter
        LinkedIn
        Syndicate Mining
        Site BrowserSafety and Health TopicsData & StatisticsMethodologyMine DisastersMSHA Data FilesMine & Mineworker ChartsTools & PublicationsTools You Can UsePublicationsNews & ArticlesResearch ProgramNORA Mining CouncilStrategic PlanMining Program, 2019-2023Miner Health Program, 2020-2030ProjectsContractsFunding OpportunitiesMining LinksAbout UsContact NIOSH MiningEmploymentFacilitiesHistoryVisitor Information NIOSH Homepage
 NIOSH A-Z
Workplace Safety & Health Topics
Publications and Products
Programs


About CDC
					Contact Us
					800-232-4636
 Facebook Twitter Instagram LinkedIn Youtube Pinterest Snapchat
 CONTACT CDC
				Contact Us
							Call 800-232-4636
							Email Us
			ABOUT CDC
				About CDC
							Jobs
							Funding
			POLICIES
				Accessibility
							External Links
							Privacy
							Policies
							No Fear Act
							FOIA
							OIG
							Nondiscrimination
							Vulnerability Disclosure Policy
			CONNECT WITH US
				Facebook
								Twitter
								Instagram
								LinkedIn
							Youtube
								Pinterest
								Snapchat
								Email
			LANGUAGES
				Español
							繁體中文
							Tiếng Việt
							한국어
							Tagalog
							Русский
							العربية
							Kreyòl Ayisyen
							Français
							Polski
							Português
							Italiano
							Deutsch
							日本語
							فارسی
							English


U.S. Department of Health & Human Services
			Accessibility
			External Links
			Privacy
			Policies
			No Fear Act
			FOIA
			Nondiscrimination
			OIG
			Vulnerability Disclosure Policy
			USA.gov


Exit Notification / Disclaimer Policy Close
 Links with this icon  indicate that you are leaving the CDC website. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website.
				Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
				You will be subject to the destination website's privacy policy when you follow the link.
				CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. Website Disclaimers
 Cancel Continue