ML18153A122

Test Rept, Compatibility of Mine Safety Appliances Custom 4500 Self-Contained Breathing Apparatus w/Oxygen-Enriched Breathing Gas.

ML18153A122
Person / Time
Site:	Surry, North Anna
Issue date:	08/30/1991
From:	Dobbin D, Webb K, Williams J NATIONAL AERONAUTICS & SPACE ADMINISTRATION
To:
Shared Package
ML18152A072	List: ML18152A071 ML18153A121 ML18153A122
References
TR-597-001, TR-597-1, NUDOCS 9704070316
Download: ML18153A122 (34)

Text

I Document No. TR-597-001 N/\5/\

National Aeronautics and Date August 30, 1991 Space Administration SUPERSEDES ALL PREVIOUS VERSIONS Test Report Compatibility of the Mine Safety Appliances Custom 4500 Self-Contained Breathing Apparatus with Oxygen-Enriched Breathing Gas Lyndon 8. Johnson Space Center White Sands Test Facility P. 0. Drawer MM Las Cruces, NM 88004

• 9704070316 970327280 PDR ADOCK 05000 p PDR (505) 524-5011

TR-597-001

• Test Report SUPERSEDES ALL PREVIOUS VERSIONS Compatibility of the Mine Safety Appliances Custom 4500 Self-Contained Breathing Apparatus with Oxygen-Enriched Breathing Gas Issued By National Aeronautics and Space Administration Johnson Space Center White Sands Test Facility Laboratories Office Prepared By: ~~ Z CJ '7f'ff Doug D bin Lockheed-ESC

~~

Prepared y ~ lz,."'J1 Lockheed-ESC

.,...._/ I -f J .() /'J *_ "

Prepared By: '-N. L U ~

JaesH.Wiiliams NASA Engineering Office Reviewed By: 7f .ww-J. D ~ 7o In /'1 1 Howard Gabel Lockheed-ESC Reviewed By:

Harold D. Beeson NASA Laboratories Office u~ o'f;, 4'iJ

• Approved By:

jn Frank J. Benz, Chief NASA Laboratories Office

(This page intentionally blank) ii

Abstract

• The NASA White Sands Test Facility (WSTF) was requested by Virginia Power to evaluate the compatibility of the Mine Safety Appliances (MSA) Custom 4500 self-contained breathing apparatus (SCBA) with oxygen-enriched breathing gas. To do this, the flammability of the Custom 4500 was assessed using three types of tests. Promoted ignition tests determined that the aluminum alloy 6061 used in the regulator body of the Custom 4500 would not sustain combustion in an atmosphere up to 52-percent oxygen at 31.03 MPa (4500 psig). Regulator combustion tests determined that the combustion of hydrocarbon contamination within the test article would not ignite the aluminum alloy 6061 in the regulator body;.however, nonmetal parts in the regulator and the high-pressure flexhose did ignite, and metal components did melt. Compressive heating tests determined that compressive heating of uncontaminated systems does not promote ignition of the high-pressure flexhose or the regulator assembly softgoods at the use conditions; however, at elevated temperatures, there may be a risk of softgood failures, as evidenced by some non-catastrophic o-ring failures at 330 K (135 °F).

The MSA Custom 4500 SCBA, therefore, is compatible (based on flammability hazards) for use with the intended breathing gas of 35-percent oxygen at 31.03 MPa (4500 psig), provided that: 1) the Custom 4500 is cleaned to remove all hydrocarbon contamination; 2) the Custom 4500 is maintained to preclude introduction of contamination; and 3) the temperature of the system is not above 330 K (135 °F) (the conditions tested) when the regulator is first activated. This testing does not indicate that the Custom 4500 is safe to use with an oxygen-enriched breathing gas in all circumstances. For example, it is recommended that tests be conducted to determine the effects of the user exhaling the oxygen-enriched mixture into a

'fire-charged' environment if the Custom 4500 is to be used during fire-fighting operations .

• iii

(This page intentionally blank) iv

Contents

• Section Figures Page vi 1.0 Introduction 1 2.0 Objective 1 3.0 Background 1 4.0 Approach 2 5.0 Promoted Ignition Tests 7 5.1 Test Samples 7 5.2 Test System 7 5.3 Procedure 7 5.4 Results and Discussion 7 6.0 Regulator Combustion Tests 10 6.1 Test Articles 10 6.2 Test System 10 6.3 Procedures 10 6.4 Results and Discussion 12 7.0 Compressive Heating Tests at Room Temperature 12 7.1 Test Articles 12 7.2 Test System 15 7.3 Procedures 15 7.4 Results and Discussion 17 8.0 Compressive Heating Tests at Elevated Temperature 18 8.1 Test Articles 18 8.2 Test System 18 8.3 Procedures 18 8.4 Results and Discussion 20 9.0 Conclusions and Recommendations 25 References 27 Distribution DIST-1

• V

Figures Figure . Page 1 Custom 4500 Regulator Assembly 3 2 Model 401 Regulator Assembly 5 3 Promoted Ignition Test System 8 4 Regulator Combustion Test System 11 5 Custom 4500 after Ignition 13 6 Compressive Heating Test System, Room Temperature 16 7 Compressive Heating Test System, El~vated Temperature 19 8 Audi-Alarm Showing Location of Failed 0-Ring 21 9 Close-Up of Extruded 0-Ring 23 vi

1.0 Introduction

• The NASA White Sands Test Facility (WSTF) was requested by Virginia Power to evaluate the compatibility of the Mine Safety Appliances (MSA) Custom 4500 self-contained breathing apparatus (SCBA) with breathing gas* at an operating pressure of 31.03 MPa (4500 psig).

The Custom 4500 is being considered for use in nuclear power stations to provide a breathable mixture in sub-atmospheric-pressure environments that may contain airborne radioactive particulate.

Since 1976, Virginia Power has successfully used the MSA Model 401 SCBA in this environment. The Model 401 is no longer manufactured and is to be replaced with the Custom 4500. The present evaluation is required because the Custom 4500 operates-at higher pressures and is constructed of different materials than the Model 401.

This test program was originally described in an amended test plan produced at WSTF (Williams 1989, Williams and Bamford 1990).

2.0 Objective The objective of this program was to determine if the MSA Custom 4500 SCBA is compatible, based on flammability hazards, with an oxygen-enriched breathing gas of 35-perce~t oxygen and 65-percent nitrogen at an operating pressure of 31.03 MPa (4500 psig) .

• 3.0 Background The Custom 4500 (Figure 1) and Model 401 (Figure 2) provide breathable gas to users working in an atmosphere that is otherwise not breathable. The breathing gas is stored in a compressed gas cylinder, sent through the cylinder valve, audi-alarm, and high-pressure flexible hose, reduced to breathing pressure in a regulator, and finally sent through a low-pressure hose to the facepiece.

The Custom 4500 is operated at a higher pressure than the Model 401 (31.03 MPa

[4500 psig] vs. 15.28 MPa [2216 psig]). The Custom 4500 regulator body is constructed of aluminum alloy 6061, while the regulator body in the Model 401 is constructed of ASTM B 124 brass. Aluminum alloy (alloy 2219) has been shown to be more flammable than Red Brass (Stoltzfus et al. 1988); therefore, the flammability hazards associated with the Custom 4500 are inherently greater.

The flammability hazards associated with using an SCBA with an oxygen-enriched breathing gas involve ignition caused by frictional heating, particle impact, and compressive heating (ASTM 1990a, 1990b). Frictional heating and particle impact could ignite the metallic materials in the SCBA; therefore, the flammability of the metallic materials must be evaluated, and if the materials are found to be flammable at the use conditions, then further

• . Breathing gas refers to a mixture of 35-pcrcent oxygen and 65-pcrcent nitrogen.

testing is required to assess hazards associated with frictional heating and particle impact.

Contamination (e.g., particles, hydrocarbons) within the SCBA could also ignite from frictional heating and particle impact and promote the combustion of the SCBA. Finally, compressive heating could ignite the SCBA soft goods or contamination in the SCBA.

The only SCBA components that are flammability hazards due to high-pressure breathing gas are the regulator, flexhose, and audi-alarm.

4.0 Approach To evaluate the compatibility of the Custom 4500 with an oxygen-enriched gas, the flammability of Custom 4500 regulator body and components-was assessed using thr"ee types of tests. For comparison, some tests were conducted to evaluate the flammability of the Model 401 regulator body and components.

• Promoted ignition tests* were conducted on the aluminum alloy 6061 and ASTM B 124 brass. This testing determined whether the metal used to construct the regulator body would sustain combustion when ignited in an oxygen-enriched atmosphere. In the promoted ignition test, a rod of the test material is suspended vertically in a chamber containing the test gas and is ignited at the bottom with a promoter. The material is considered to be nonflammable at the test conditions if three rods do not sustain combustion for more than half their length. Testing was conducted as a function of oxygen concentration (varying from 20.9 to 100 percent), chamber pressure (31.03 MPa [4500 psig] and 15.28 MPa [2216 psig]), and promoter material (aluminum, magnesium, and nitrile rubber).

Regulator combustion tests were conducted on components from both the Custom 4500 and the Model 401. These tests were used to determine if the combustion of hydrocarbon contamination within the assemblies would ignite the internal components at the use conditions. The hydrocarbon contamination was introduced at very high levels. Catastrophic failure or ignition of components within the regulator assembly would indicate that further testing, simulating ignition hazards in use conditions, would be required.

• Compressive heating tests were conducted on the Custom 4500 to simulate ignition hazards in use conditions. These tests involved rapidly pressurizing the Custom 4500 with the oxygen-enriched breathing gas. The testing was conducted with the regulator in each of the three possible operational modes. The testing was conducted at room temperature (294 +/- 11 K [70 +/- 20 °F]), and then in the worst-case operational mode at 330 K (135 °F) to assess ignition hazards when the breathing gas and regulator were at elevated temperatures at activation.

Compressive heating tests were accomplished in two phases. In Phase 1, gaseous nitrogen was used as the test gas at 31.03 MPa (4500 psig). These tests were conducted to determine the pressurization rates and pressurization times for the Custom 4500 in the manufacturer's recommended operating mode. Tests were

• Presently, the_ accepted title of this test is, "Promoted Combustion Test." This test is similar to Test 17 in NHB 8060.IC (NASA 1990).

2

, High-Pressure Flexible Hose w

Audi-Alarm

./ Inlet from High-Pressure Cylinder

.,. ',.*. Custom 4500

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'::'jf:,*

Figure 1 Custom 4500 Regulator Assembly

(This page intentionally blank) 4

.~STF

• 0320

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Figure 2 Model 401 Regulator Assembly

conducted using the Custom 4500 high-pressure cylinder valve and using a fast-opening valve that had been used in previous testing at WSTF. In Phase 2, testing was conducted with the breathing gas, using the fast-opening valve to simulate the worst-case condition.

5.0 Promoted Ignition Tests 5.1 Test Samples The promoted ignition test samples were 0.318-cm (0.125-in.) diameter rods fabricated from aluminum alloy 6061 (31.8-cm [12.5-in.] long) and ASTM B 124 brass (6.033-cm [2.375-in.J.

long). Three types of promoters were used: aluminum, magnes"ium, and nitrile rubber.

5.2 Test System The promoted ignition test system consisted of a high-pressure chamber, a high-pressure gas supply," an ignition source, and instrumentation to measure chamber temperature and pressure (Figure 3). The test event was recorded on standard video.

5.3 Procedure The test sample was cleaned in a detergent and water solution, rinsed with deionized water, and blown dry with nitrogen. A promoter was attached to the bottom of the sample and a Pyrofuze initiator was wrapped around the promoter. The sample was installed in the test chamber and wire leads from a power supply were connected to the Pyrofuze initiator. The test chamber was closed, pressurized with nitrogen, and decay leak-checked.

Following the leak check, the chamber was purged with the test gas and filled to the test pressure. The videotape recorder was started anJ the' Pyrofuze initiator was ignited, which then ignited the promoter. Visual data were recorJ~d on video, and test chamber gas temperature and pressure were recorded, but are not reported. After testing was complete, the unburned sample length was measured and recorded.

5.4 Results and Discussion

• Table 1 contains the results of the ignition tests, based on the flammability criteria described in the Approach. The tests indicate that ASTM B 124 brass is not flammable in 100-percent oxygen at either pressure. Aluminum alloy 6061 was flammable in 100-percent oxygen at use pressures. At lower oxygen concentrations, the aluminum promoters did not ignite, and thus neither did the aluminum rods. Magnesium promoters, which will ignite at low oxygen concentrations, were used at oxygen concentrations lower than I 00 percent, and the concentration threshold at which aluminum alloy 6061 combustion occurred was determined .

. The oxygen met the requirements for United States Pharmaeopeia medical oxygen (USPC 1985). The nitrogen met the requirements for National Formulary medical nitrogen (USPC 1985). Breathing air met the specifications set forth in the Compressed Gas Association Pamphlet G 7.1 for Type I, Grade D compressed air (CGA 1973). All gas mixes were analyzed prior to use to ensure that they met the above specifications.

7

Test Gas In Test Gas Out Test Sample Pyrofuze Wire Promoter Figure 3 Promoted Ignition Test System Aluminum alloy 6061 was flammable at oxygen concentrations greater than 60 percent but was not flammable at oxygen concentrations of 52 percent or lower. Tests indicate that the aluminum alloy 6061 is not flammable at the intended use conditions of 35-percent oxygen, 65~percent nitrogen, and 31.03 MPa (4500 psig).

Many of the nonmetallic components in the regulators are made of nitrile rubber. Additional testing was conducted with nitrile rubber promoters to determine if the rubber could promote combustion of the aluminum alloy 6061 or ASTM B 124 brass rods. Although these results indicate that the nitrile rubber promoter would not promote combustion of the metal even in 8

Table 1 Promotaj Ignition Test Results __

Pressure  % Concentration Results (MPa) (psig) 02 N2 Brass Aluminum Aluminum Promoter a

31.03 4500 100 0 No burn 35 65 b No promoter ignition 20.9 79.1 b No promoter ignition 15.28 2216 100 0 b Complete burn 35 65 b No promoter ignition 20.9 79.1 b b Magnesium Promoter 31.03 4500 70 30 Complete burn 60 40 Complete burn

. 52 48 No burn 35 65 No burn 20.9 79.1 No burn Nitrile Rubber Promoterc 31.03 4500 100 0 No burn No burn 35 65 b No burn 20.9 79.1 b b 3

Not tested because samples burned at 15.28 MPa (2216 psig) bNot tested because samples didn't burn under more severe conditions.

cResults with nitrile rubber prc,,noters are configurationally dependent and should not be used to make conclusions about aluminum flammability (see text).

100-percent oxygen, subsequent testing at WSTF has concluded that promoted combustion of aluminum alloy using nonmetallic promoters is configurationally dependent (Steinberg, Rucker, and Beeson 1989). (There also exists a configuration dependence of metal promoters, but it is understood well enough to use test results to assess flammability).

Therefore, the conclusion that nitrile rubber will not promote combustion of aluminum alloy 6061 in a 100-percent oxygen atmosphere cannot be made. Additionally, tests conducted at WSTF have shown that as little as 1.5 mg of nitrile rubber will ignite Inconel 718, which is much less flammable than aluminum alloy.*

• *WSTF results to be published.

9

6.0 Regulator Combustion Tests 6.1 Test Articles The regulator combustion test articles were assembled using the following components from the Custom 4500 and the Model 401: the high-pressure cylinder valve, the audi-alarm, the high-pressure flexhose, and the regulator. Ten test articles were assembled: six with Custom 4500 components and four with Model 401 components.

6.2 Test System The regulator combustion test system (Figure 4) consisted of a high-pressure test-gas supply, an ignition source (Pyrofuze wire) capable of igniting the contaminant, and necessary instrumentation. The ignition source was placed in an igniter block assembly upstream of the test article inlet. Pressure transducers and thermocouples (type K) were used to monitor pressure and internal heating of the regulator. The ignition of the Pyrofuze and visible light emission were monitored using photocells. An infrared (IR) video camera was used to monitor the temperature gradient along the test article. The test event was also recorded with standard video.

6.3 Procedures The test articles were inspected and photographed. Obvious contamination was removed from each test article. The audi-alarm/flexhose assembly and the regulator were separated and each was weighed. Approximately 0.5 ml of hydrocarbon oil (Mobil DTE 30) was injected into the audi-alarm/flexhose assembly. Approximately 1 ml of hydrocarbon oil was injected into the inlet port of the regulator, which was configured with the bypass and mainline valves open. The test articles were reassembled and 3 .45-MPa (500-psig) nitrogen was flowed through the regulator assembly for about 30 seconds to disperse the contamination. The test articles were allowed to drain for approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. Each test article *was weighed to determine how much contaminant remained.

The regulator assembly was secured into the test system. Data acquisition and video equipment were started. The test system was pressurized with the breathing gas to the operating pressure of tl-ie model being tested. Gas flow through the test article, which had the mainline and bypass valves open,* was established and allowed to stabilize for approximately 3 seconds.

The Pyrofuze initiator was energized, which ignited the contamination. The test system was monitored and any resulting reaction was allowed to proceed until it had subsided, and the thermocouples and IR video indicated that the temperature inside the regulator had stabilized.

When the reaction became too violent, the test conductor shut off the oxygen flow to prevent damage to the test system. Following the test, the test articles were disassembled, including disassembling the regulator, and visually inspected to determine the extent of damage.

+This represents a free-flow condition in excess of 300 liters/min, per the manufacturer's specifications.

10

• High Pressure Test Gas Source 68.9 MPa (10,000 psi) Maximum Primary Isolation Valve Secondary Isolation Valve Low Pressure Oxygen Purge Test System Vent Supply Pressure Transducer Monel Fire Stop Test Assembly Thermocouple f

r- Up~~-

Photocell Igniter Block Assembly <t' I

I I

Downstream Photocell Test Article Test Artiqle Emergency Vent I

I Preset I I Metering Burst Disk I

Valve I I L--------------'

Figure 4 Regulator Combustion Test System 11

6.4 Results and Discussion The hydrocarbon contamination in the high-pressure flexhoses on two of the Model 401 test articles and one of the Custom 4500 test articles ignited and caused the flexhoses to burst.

The regulators attached to these three flexhoses suffered internal damage, as evidenced by ignition and melting of the nylon valve seats, damage to the inlet filters, and melting of some of the regulator metal. Flow through the Custom 4500 regulator ceased during the test, and the regulator body broke apart from the valve assembly (Figure 5). A second Custom 4500 test article displayed signs of internal hydrocarbon combustion, but was not functionally damaged. There was no evidence in any of the damaged test articles that metal ignition or combustion had occurred. There was no apparent damage to the other four Custom 4500 test articles and two Model 401 test articles even though there was evidence that the hydrocarbon contamination had ignited.

This testing showed that the metal regulator body or metallic components within the regulator would not ignite even if an ignition source were provided and the system was grossly contaminated with hydrocarbon oil. However, the high-pressure flexhose and the nylon valve seats did ignite and sustain combustion, so further ignition testing was necessary under more realistic conditions.

7.0 Compressive Heating Tests at Room Temperature Compressive heating is known to cause oxygen system fires, and these regulators are constructed and operated in a manner that causes compressive heating. Normal operation consists of donning the system and then opening the high-pressure cylinder valve to pressurize the audi-alarm, the high-pressure flexhose, and the regulator. Compressive heating, caused by rapidly pressurizing gas, could cause mainline-valve-seat ignition, bypass-valve-seat ignition, or high-pressure flexhose ignition. A hazard analysis conducted on the system determined that there are three possible operations that could cause compressive heating:

• Opening the high-pressure cylinder valve with the mainline and bypass valves closed

• Opening the high-pressure cylinder valve with the mainline valve open, the bypass valve closed, and the regulator outlet capped

• Opening the high-pressure cylinder valve with the mainline valve closed, the bypass valve open, and the regulator outlet capped.

Although the last two operations are not recommended by the manufacturer, both are likely scenarios in actual use. The final operation, with the bypass valve open and the regulator outlet capped, is an off-limits, but feasible, regulator operation. It is likely that this operation would mechanically damage the low-pressure diaphragm; however, it was not known if this operation could ignite the diaphragm.

7.1 Test Articles Ten compressive heating test articles were assembled from the following Custom 4500 components: the audi-alarm, the high-pressure flexhose, and the regulator.

12

NASA-IISTF

• 0351 Regulator Internal Parts

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Flexhose Burst Point  : 1 i \",

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i Threads from Valve Assembly Figure S Custom 4500 after Ignition

7 .2 Test System

• The compressive heating test system consisted of a high-pressure test-gas supply, a method of rapidly pressurizing the test components (impact valve), and instrumentation (Figure 6).

Static and dynamic pressure transducers were used to monitor pressure and pressurization rate, respectively. Thermocouples (type K) were used to measure the temperature of the test gas upstream of the test article (TT-325 in Figure 6) and the temperature of the regulator body (taped-on thermocouple IT-326 in Figure 6). An IR video camera was used to monitor the temperature gradient along the test article. The test event was recorded using standard video.

7 .3 Procedures 7.3.1 Phase 1 In Phase 1, the test article was connected to the compressive heating test system. The test system was pressurized with nitrogen to the impact valve. The impact valve was opened to rapidly pressurize the test article with the mainline and bypass valves closed. A data-acquisition system was used to monitor the nitrogen pressure and the regulator pressurization time.

The first series of tests were conducted to determine the.pressurization rate resulting from manual operation of the cylinder valve. For these tests, the impact valve shown in Figure 6 was a cylinder valve from the Custom 4500. Three technicians, certified to use an SCBA, opened the cylinder valve as they normally would (normal rate). Then the technicians opened the valve as fast as they could (rapid rate). The test was repeated five times by each technician at each rate. This test was repeated for three cylinder valves. Typical pressurization rate profiles were established and average pressurization times were calculated for each rate.

In the second series of tests, the cylinder valve was removed and a high-speed automatic valve was installed in its place. The regulator assembly was pressurized ten times using this valve.

Typical pressurization rate profiles were established and the average pressurization times were calculated. Data from the two test series were compared and the faster of the two valves (the automatic valve) was ustd in Phase 2 testing to provide a worst-case compressive-heating scenario.

7 .3.2 Phase 2 In Phase 2, the test article was reinstalled in the test system. The test system was decay leak-checked with the breathing gas and then vented. The impact valve was closed and the breathing-gas pressure upstream of the impact valve was increased to 31.03 MPa (4500 psig).

The impact valve was remotely opened to rapidly pressurize the test article with the mainline and bypass valves closed. The regulator assembly remained pressurized after each pressurization (impact), until the IR camera indicated that the regulator assembly outside temperature had stabilized and begun to decrease. The breathing gas was then vented and the regulator assembly was allowed to cool before the next impact. This test was repeated a total of ten times, after which a functional check of the regulator was performed to determine if any damage had occurred. This sequence was repeated with the mainline valve open and the regulator outlet capped, and then with the bypass valve open and the regulator outlet capped.

15

PT-82 MV-01 INTtNSlrIER PT-8' ACCIMULATaR High Pr*ssUI"* T*st Gas Supply IHPACT VALVE I-'

(J\

MSA REGULATOR BYPASS VALVE PT-IOI

<PCB>

HAIN VALVE HSA HOSE AUDI ALARM Figure 6 Compressive Heating Test System, Room Temperature

Upon completion of the test matrix (10 impacts in each of the three configurations), the test article was functionally tested, disassembled, and visually inspected for signs of ignition or mechanical damage. The above procedures were repeated for each of the ten test articles.

7 .4 Results and Discussion 7.4.1 Phase 1 Manually opening the high-pressure cylinder valve resulted in average pressurization times of 480 milliseconds (normal opening speed) and 274 milliseconds (rapid opening speed), while the impact valve resulted in an average pressurization time of 155 milliseconds. The pressurization rate profiles were nearly identical for both valves. Based on the pressurization*

times and the fact that the rate profiles were similar, the fast-opening impact valve was used in Phase 2.

7.4.2 Phase 2 The average pressurization times for 100 impacts from 0.101 to 31.03 MPa (12.8 to 4500 psig) are shown in Table 2 for the three operational modes tested. The worst case of the three configurations is when the mainline valve and bypass valve are both closed, which is the intended use configuration.

The pretest temperature of the test article, measured using the IR camera, varied from 296 to 302 K (73 to 83 °F). The posttest temperature of the test article, measured using the IR camera, varied from 303 to 307 K (85 to 92 °F). Because these temperatures were measured using an IR camera, they do not represent actual temperatures of the test article or test gas but give a measure of heat generation and heat transfer within the test article. Although the pretest temperature of the gas was not measured, it was assumed to be the ambient temperature of the system (297 +/- 8 K [75 +/- 15 °F]). A functional check performed on the regulator assemblies after each set of 10 impacts showed no signs of mechanical damage.

Posttest functional checks, disassembly, and inspection, conducted after the test matrix was complete, revealed that all test articles operated within the manufacturer's specifications, and no signs of ignition or mechanical damage were found.

Table 2 Fast-Opening Impact Valve Results Configuration Pressurization Time (milliseconds)

Mainline Valve - CLOSED Bypass Valve - CLOSED 155 Mainline Valve - OPEN Bypass Valve - CLOSED 160 Mainline Valve - CLOSED Bypass Valve - OPEN 170 17

8.0 Compressive Heating Tests at Elevated Temperature The compressive heating tests described previously were repeated at a higher initial temperature of 328 to 333 K (130 to 140 °F). (See Section 7.0 for a more complete description.) Only the first of the three operations was used in this test, because flow was dead-ended into the valve seat, and because this operation had the highest pressurization rate.

8.1 Test Articles Three compressive heating test articles were assembled from the following Custom 4500 components: the audi-alarm, the high-pressure flexhose, and the regulator. These thre*e test articles h~d previously been used in the* compressive heating tests at room temperature.

8.2 Test System The compressive heating test system consisted of a high-pressure test-gas supply, a method of rapidly pressurizing the test components (impact valve), and instrumentation (Figure 7).

Static and dynamic pressure transducers were used to monitor pressure and pressurization rate, respectively. Thermocouples (type K) were used to measure the temperature of the test gas upstream of the test article (1T-BZ222 in Figure 7) and the temperature of the regulator body (taped-on thermocouple TI-BZ223 in Figure 7). Heater tape was used on the accumulator to warm the test gas and heat lamps were used to heat the test article to 328 to 333 K (130 to 140 °F). The test event was recorded using standard video.

8 .3 Procedures 8.3.1 Phase 1 In Phase 1, the test article was connected to the compressive heating test system. The test system was pressurized with nitrogen to the impact valve. The impact valve was opened to rapidly pressurize the test article with the mainline and bypass valves closed. A data-acquisition system was used to monitor the nitrogen pressure and the regulator pressurization time.

The regulator assembly was pressurized ten times using this valve. Typical pressurization rate profiles were established and were compared to the profiles from the earlier compressive heating tests (see Section 7.4.2).

8 .3 .2 Phase 2 In Phase 2, the test article was installed in the test system. The test system was decay leak-checked with the test gas and then vented. The impact valve was closed and the breathing-gas pressure upstream of the impact valve was increased to 31.03 MPa (4500 psig). The impact valve was remotely opened to rapidly pressurize the test artic~e with the mainline and bypass valves closed. The regulator assembly remained pressurized after each pressurization (impact), until the regulator assembly surface temperature (as measured by thermocouple IT-BZ223) had stabilized and begun to decrease. The breathing gas was then vented and the regulator assembly was allowed to cool and then stabilize at 328 to 333 K (130 to 140 °F) before the next impact. This test was repeated a total of 20 times, after which a functional check of the regulator was performed to determine if any damage had occurred. Upon 18

ACCUMULATORS TT-B2221

!Mpoct Volve TT-BX222 PT-B2300

<PCB)

AUDI MSA REGULATOR TT-BZ223 TAPE ON BYPASS VAL VE Figure 7 Compressive Heating Test System, Elevated Temperature

• 19

completion of the test matrix, the test article was functionally tested, disassembled, and visually inspected for signs of ignition and mechanical damage. The above procedures were repeated for each of the three test articles.

8.4 Results and Discussion 8.4.1 Phase 1 The high-speed automatic valve was used, because the earlier compressive heating tests demonstrated that the automatic valve produced the worst-case scenario due to its fast actuation time. The pressurization times averaged 140 milliseconds and the pressurization rates for the 330 K (135 °F) tests followed profiles similar to those of the earlier compr~ssive heating tests at 305 K (90 °F).

8.4.2 Phase 2 The pretest temperature of the test article, measured using the thermocouple taped to the test article, varied from 315 to 341 K (108 to 154 °F). The posttest temperature of the test article, measured using the same thermocouple, varied from 319 to 344 K (114 to 159 °F).

The pretest temperature of the gas in the accumulator was measured and ranged from 327 to 339 K (129 to 151 °F). Tests were initiated when the gas temperature was approximately 328 to 333 K (130 to 140 °F). The first test article developed a leak at the fifteenth impact and the audi-alarm started ringing. Disassembly revealed the failure of one a-ring (part # 69667) on the audi-alarm (Figures 8 and 9). Neither the damaged o-ring nor the audi-alarm body showed signs of combustion. Two audi-alarm o-rings were replaced, the test article was reassembled and functionally checked, and it was then retested. Testing of the remaining 2 test articles proceeded without incident. Posttest functional checks conducted after the 20 impacts were complete revealed that all test articles operated within the manufacturer's specifications and no signs of ignition were found.

Posttest inspection did reveal some mechanical damage. The second test article was leaking slightly at the pressure adjustment cap on the audi-alarm with the cylinder pressure at 13.79 MPa (2000 psig) .. Leakage was detected by spraying a soap bubble solution onto the audi-alarm pressure adjustment cap and noting bubble formation. The leak was undetectable during normal operation. Leakage was caused by the a-ring in the same location as the one that failed on the previous test article. This o-ring had extruded where it rubbed against the piston in the audi-alarm body (Figures 8 and 9). The polytetrafluoroethylene (PTFE) plain washer on the mainline valve stem was crushed, but was functional, on the second and third test articles. The MSA procedure requires this washer to be replaced each time the regulator is disassembled. The filter in the audi-alarm assembly on the third test article was dislodged and was protruding into the flow path. The filter was not damaged.

8.4.3 Flcxhose Ignition None of the high-pressure flexhoses in the compressive heating tests ignited. Previous testing of PTFE-lined flexhoses determined that four variables influence the hazard of ignition due to compression heating (Martos and Williams 1990):

• The type of gas introduced into the component or system (specifically, the percentage of oxygen in the gas) 20

Figure 8 Audi-Alarm Showing Location of Failed 0-Ring

(This page intentionally blank) 22

• WSH 1468 Figure 9 Close-Up of Extruded 0-Ring

• The rate at which pressurization occurs The final pressure of the gas The configuration at the end of the component or system.

In that testing, flexhoses rated at 20.68 MPa (3000 psig) ignited as a result of compressive heating from an impact of 100-percent oxygen at 25.86 MPa (3750 psig) with a 146-millisecond pressurization time (25,700 psi/sec pressurization rate). In comparison, the high-pressure flexhoses of the Custom 4500s were pressurized to 31.03 MPa (4500 psig) in 140-155 milliseconds (29,000-32,000 psi/sec pressurization rate). The present testing was performed in 35-percent oxygen, and the Custom 4500 had a larger heat sink (the regulator) at the end of the high-pressure flexhose than did the flexhoses in the previous testing. It is not known what impact these two variables had on the testing, but they likely reduced the danger from compressive heating. In the present study, the nitrile-rubber-lined flexhoses would increase the ignition hazard. Testing showed that the Custom 4500 flexhoses and the internal regulator assembly softgoods would not ignite due to compressive heating even when subjected to successive pressurization cycles. There was, however, some damage to the audi-alarm o-rings at higher temperatures. This failure is consistent with changes in the properties of the material (less viscous, more elastic) at elevated temperatures. This damage caused leakage but no failure of the regulator to operate. Because the final temperature of the system is dependant on the initial temperature, the result reported cannot be extrapolated beyond the maximum initial temperature condition tested (330 K [135 °F]) .

• 9.0 Conclusions and Recommendations Based on the testing, the following conclusions are made for the MSA Custom 4500 SCBA:

• The aluminum alloy 6061 used in the regulator body would not sustain combustion in an atmosphere up to 52-percent oxygen at 31.03 MPa (4500 psig).

• Combustion of hydrocarbon contamination within the test article, which was pressurized to 31.03 MPa (4500 psig) in 35-percent oxygen, would not ignite the aluminum alloy 6061 in the regulator body; however, nonmetal parts in the regulator and high-pressure flexhose did ignite, and metal components did melt.

• Compressive heating of uncontaminated systems does not promote ignition of the high-pressure flexhose or the regulator assembly softgoods with a breathing gas of 35-percent oxygen at 31.03 MPa (4500 psig) and an initial temperature up to 330 K (135 °F). At elevated temperatures, there may be a risk of softgood failures, as evidenced by some non-catastrophic o-ring failures at these conditions.

The MSA Custom 4500 SCBA is compatible, based on flammability hazards, for use with the intended breathing gas of 35-percent oxygen at 31.03 MPa (4500 psig), provided that: 1) the Custom 4500 is cleaned to remove all hydrocarbon contamination; 2) the Custom 4500 is maintained to preclude introduction of contamination (ASTM 1990c); and 3) the temperature of the system is not above 330 K (135 °F) when the regulator is first activated .

• 25

Periodic maintenance, such as whole-regulator leak checks and flow tests, should also be performed to reveal small leaks and damaged parts.

This testing does not indicate that the Custom 4500 is safe to use with an oxygen-enriched breathing gas in all circumstances. For example, if the Custom 4500 will be used during fire-fighting operations, it should be tested in external fire conditions (NFPA * /Lawrence Livermore National Laboratory). This test will determine the effects of the user exhaling the oxygen-enriched mixture into a 'fire-charged' environment.

• National Self-Contained Breathing Apparatus Fire Research Project, National Fire Protection Association Research Foundation, Quincy, Mass.

26

• References ASTM. "G63-87: Standard Guide for Evaluating Nonmetallic Materials in Oxygen Service."

Annual Book of ASTM Standards, Vol. 14.02, American Society for Testing and Materials, Philadelphia, Penn., 1990a.

ASTM. "G88-84: Standard Guide for Designing Systems for Oxygen Service." Annual Book of ASTM Standards, Vol. 14.02, American Society for Testing and Materials, Philadelphia, Penn., 1990b.

ASTM. "G93-88: Standard Practice for Cleaning Methods for Materials and Equipment Used in Oxygen Enriched Environments." Annual Book of ASTM Standards, Vol. 14.02, American Society for Testing and Materials, Philadelphia, Penn., 1990c.

CGA. Pamphlet G 7.1: Commodity Specification for Air-ANSI ZJJ6.1. Compressed Gas Association, Inc., Arlington, Va., 1973.

Martos, L., and J. Williams. Oxygen Pneumatic-Impact Testing of Stratoflex Carbon-Impregnated PIFE-Lined Flexible Hoses. TR-595-001, NASA White Sands Test Facility, Las Cruces, N. Mex., April 24, 1990.

NASA. Flammability, Odor, Offgassing, and Compatibility Requirements and Test Procedures for Materials in Environments that Support Combustion. NHB 8060.lC, NASA Office of Safety and Mission Quality, Washington, D.C., 1990.

Steinberg, T. A., M. A. Rucker, and H. D. Beeson. "Promoted Combustion of Nine Structural Metals in High-Pressure Gaseous Oxygen; A Comparison of Ranking Methods." Flammability and Sensitivity of Materials in Oxygen-Enriched Atmospheres:

Fourth Volume, ASTM STP 1040, Joel M. Stoltzfus, Frank J. Benz, and Jack S.

Stradling, editors, American Society for Testing and Materials, Philadelphia, Penn.,

1989, pp. 54-75.

Stoltzfus, J.M., J.M. Homa, R. E. Williams, and F. I. Benz. "ASTM Committee G-4 Metals Flammability Test Program: Data and Discussion." Flammability and Sensitivity of Materials in Oxygen-Enriched Atmospheres: Third Volume, ASTM STP 986, D. W.

Schroll, editor, American Society for Testing and Materials, Philadelphia, Penn., 1988, pp. 28-53.

USPC. The United States Pharmacopeia, 2F1 Revision, and The National Formulary, J(Jh Edition. United States Pharmacopeial Convention, Inc., Rockville, Md., January l, 1985.

Williams, J. Determination of O? Compatibility and Reliability of the Mine Safety Appliance Breathing Apparatus Custom 4500 and Model 401. TP-WSTF-597 A, NASA White Sands Test Facility, Las Cruces, N. Mex., February 27, 1989 .

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References (continued)

Williams, J. and L. Bamford. Determination of 0 2 Compatibility and Reliability of the Mine Safety Appliance Breathing Apparatus Custom 4500 and Model 401 (Amendment 1).

TP-WSTF-597A, NASA White Sands Test Facility, Las Cruces, N. Mex., May 17, 1990.

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Distribution Organization No. of Copies Virginia Power Innsbrook Technical Center/Tom Szymanski, David Sommers 2 North Anna Power Station/Erich Dreyer 1 Surrey Power Station/Barry Garber 1 Mine Safety Appliances Field Sales, Texas/Neil West 1 Field Sales, Pennsylvania/Richard F. Graham 1 Product Planning/Bill Lambert 1 Safety Products Engineering/Richard Erth 1 NASA White Sands Test Facility Laboratories Office 2 Engineering Office 1 Lockheed-ESC White Sands Test Facility Laboratory Programs Section 2 Publications and Photo/Video Section 1 Technical Library 1

• DIST-1

Attachment 3 Lawrence Livermore National Laboratory Test Report Virginia Electric and Power Company Surry and North Anna Power Stations