N Document No. W STF-IR-95-0048

January 30. 1995 Date

National Aeronautics and Space Administration

Investigative Report

Evaluation of Solvent Alternatives to Trichlorotrifluoroethane (CFC-113) for Cleaning

of Gauges and Precision Instruments

Phase I

Lyndon B. Johnson Space Center White Sands Test Facility P. 0. Drawer MM Las Cruces, NM 88004 (505) 524-501 1

W STF-IR-95-0048

Investigative Report

Evaluation of Solvent Alternatives to Trichlorotrifluoroethane (CFC-113) for Cleaning of Gauges and

Precision Instrumentation

Phase I

Issued By National Aeronautics and Space Administration

Johnson Space Center White Sands Test Facility

Laboratories Office

' J Prepared By: A' d 7 Q L - L -

Paul Biesinger AlliedSignal Technical Services Corp. Team

Prepared By: Harold Beeson NASA Laboratories Office

Approved By: - Harold Eeeson NASA Laboratories Office

Contents

Page Section

1.0

2.0

3.0

4.0

5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9

6.0 6.1 6.2 6.3 6.4 6.5

7.0

Introduction

Objective

Background

Approach

Test Article Description and Procedures Test Article Test Hardware Test Solvents Test Contaminants Contamination Procedure Cleaning Method Description NVR Determination NVR Recovery Procedures Oxygen Compatibility Testing

Results Coupons Simulated Gauges Test Hardware NVR Recovery Results Oxygen Compatibility Results

Conclusions

References

Distribution

1

1

1

3

3 3 4 4 4 5 7 9 9 9

9 9 9 11 16 16

20

23

DIST-1

1.0 Introduction

Regulations regarding chlorofluorocarbons (CFC's) have mandated that CFC's will not be produced as of January 1996. Trichlorotrifluoroethane (CFC-113), used widely for cleaning aerospace hardware, is classed as a CFC with a limited production life. Because of the regulation, a search is being conducted among candidate solvents to replace CFC-113.

Most gauges used in aerospace systems, especially those gauges used in high-pressures and critical medias such as oxygen, breathing air, and rocket propulsion systems, which require extreme cleanliness levels, will be affected by the CFC ban.

The NASA Johnson Space Center (JSC) White Sands Test Facility (WSTF) was requested by the Kennedy Space Center (KSC), jointly with Naval Sea System Command (NAVSEA), to evaluate possible replacements for CFC 113 to be used in the cleaning of high-pressure gauges and instrumentation. The solvents considered were selected because of their property similarities to CFC 113 with compromises for flammability, toxicity, and solvent power. This report contains the results of testing to date for some of these select solvents. Other solvents are scheduled to undergo further testing, and the results will be reported in future investigative reports.

2.0 Objective

The purpose of this investigation is to evaluate CFC 113 replacement candidate solvents and their ability to be used to clean pressure gauges and precision instrumentation.

3.0 Background

The production of chloroflouorocarbons (CFC's) and methyl Chloroform (1,1,1- Trichloroethane, MCF) both used in cleaning, will end by January 1, 1996 because of concerns about stratospheric ozone depletion. This ban on production is being imposed by the Montreal Protocol and the resulting 1990 Clean Air Act amendments. Because of the production ban, a search is being conducted throughout the cleaning industry to identify alternative chemicals and processes for cleaning of machined parts and hardware. In general, four types of solvents are being used or are being considered for use as alternatives: (1) aqueous and semiaqueous, (2) nonhalogenated organic such as hydrocarbon or alcohols, (3) nonfluorinated chlorocarbons such as perchloroethylene and trichloroethylene, and (4) hydrochlorofluorocarbons (HCFC's), hydrofluorocarbons (HFC's), and perfluorocarbons (PFC's).

Although several alternatives have been identified that incorporate aqueous processes, a need still exists for nonaqueous solvents fcr cleming. A recent sOJdy by the Navy has identified the cleaning and verification of high-pressure gauges and precision instrumentation as one area where no aqueous alternative exists and a solvent alternative must be identified (Antin, 1994).

Properties that should be considered in the evaluation of alternatives for cleaning include the following:

e Ability of the solvents to remove contaminants

e Ability of the solvent to be removed from the cleaned part

0 Flammability of the solvent, especially for solvents musidered for use in oxygen systems

0 Toxicity

0 Residues left behind by the solvent on the cleaned part

0 Ability of the solvent to be used as a verification fluid

The types 'of contaminates that must be removed in the cleaning process varies depending on the component use. Typical contaminants include cutting oits, hydraulic fluids, gauge calibration fluids, thread lubricants, and greases.

The ability of the solvent to be removed from the part is key to its succzss as a cleaning fluid for gauges and instrumentation because residual solvent could react with the use fluid or become a toxicity issue. The difficulty in incorporating aqueous- or semiaqueous-based cleaning technology for cleaning of gauges and instrumentation, which have small orifices and channels, is that the water is not easily removed from the part and will concentrate any surfactants that are used to increase the solvent capabilities of the warn.

Flammability is especially an issue with nonhalogenated organic solvents including alcohols, keytones, and ethers which can be extremely flammable. This is not only a consideration for handling during the cleaning process, but in the case of parts for oxygen, oxidizer, and air service, if the solvent is not completely removed from the part or is abt-bed into sofigds, the part may ignite during operation. Flammability is not only a c o n m for organic solvents, but also for some chlorinated and fluorinated solvents that comain hydrogen.

One of the main advantages to CFC 113 is its low toxicity. Toxicity is a concern for solvent replacements not only for handling during the cleaning process, but also in the case where the cleaned components are being used to supply breathing air or oxygen.

The residue left behind by the solvent on the part must be limited because the residue could react with the use fluid or itself become a contaminant that interferes with the operation of the component.

The ability of the solvent to be used as a verification fluid is essential bemae, in many instances, the solvent used to clean the component is the same solvent used to verify component cleanliness. The typical verification procedure involves the measurement of the solvents nonvolatile residue (NVR) after rinsing &e cleaned part. Some solvents will d i s t i l l nonvolatile compounds during evaporation, which will result in inconsistent NVR results.

2

I

4.0 Approach

To accomplish the objective, a series of tests was conducted to evaluate the fluid properties of the candidate solvents as well as the ability of these solvents to remove contaminants. Toxicity and strict physical property testing was not accomplished; rather literature values were consulted for the evaluation.

Solvents were selected for evaluation after reviewing literature and consultating with KSC and NAVSEA personnel. Solvents were excluded from further testing, if during the evaluation, it was determined that the solvent would not make a feasible alternative. The solvents tested included a hydrocarbon, an alcohol, an ether, two nonfluorinated chlorocarbons, and an HCFC.

Fluid evaluation testing consisted of a determination of the solvents' NVR, an evaluation of the solvents' consistency in NVR determinations, and an evaluation of the compatibility of the solvent with oxygen. An evaluation of the solvents ability to be removed from the component was accomplished in a qualitative fashion based on the solvents boiling point and observations during the cleaning process; however, additional testing is planned to quantitatively determine the solvent removal from the part; this data will be presented in subsequent reports.

Contaminant removal testing was conducted using three test configurations. In the first configuration, the solvent was evaluated using small coupons that had been contaminated with a known amount of contaminant. The second configuration consisted of an evaluation using simulated hardware that could be weighed to determine the amount of contaminant removed, but allowed a more realistic challenge to the solvent. In the final configuration, actual test hardware was cleaned, and the contaminant removal was compared to CFC 113. The decision to test a particular solvent in a given test configuration was based on previous test data.

The test hardware used represented a variety of gauge and instrumentation types, including high- and low-pressure Bourdon tube-type pressure gauges (with and without bleed ports), pressure transducers, thermocouple sensors, vacuum gauges, and a rotameter-type flowmeter. The contaminants tested represent a variety of contaminant types and were chosen based on discussions with KSC and NAVSEA personnel. Not all contaminants were tested with all solvents as some solvents would not be appropriate.

5.0 Test Article Description and Procedures

5.1 Test Article

Two types of articles were tested: coupons and simulated gauges. The coupons tested were uncoated, 304-stainless-steel and aluminum couporls that were 2 x 4 x 2/16 in. thick. The simulated Bourdon tubes were constructed from a 1/8-in. stainless-steel tube, 16 in. long with fittings, and coiled in to a 4-in. coil.

3

5.2 Test Hardware

The test hardware were divided into two groups: gauges and instrumentation (Tables 1 and 2). The criteria for the selection of gauges included materials of construction, configuration, and range. The instrumentation included high- and low-pressure transducers, thermocouple transducers, differential pressure transducers, and a rotameter-type flowmeter. The Bourdon gauge shown in Table 2 was included to determine if cleaning processes used for these instrumentation could also be used for gauges.

5.3 TestSolvents

The properties of the solvents that were tested are listed in Table 3. To date, five solvents have been investigated: 95 percent ethanol (EtOH), a solution of tert-butylmethylether (TEME) in a-hexane, tetrachloroethylene (PCE), trichloroethylene (TCE), and a mixture of 45 percent 3,3dichloro-l, 1,1,2,2-pentafluoropropane (HCFC-225ca) and 55 percent 1,3- dichloro-l,l,2,2,3-pentafluoropropane (HCFC-225cb); the mixture is referred to as HCFC-225. In addition, CFC-113 was used for comparison purposes.

5.4 Test Contaminants

The test contaminants used in this investigation are listed in Table 4. The contaminants consisted of two hydraulic oils, a fluorinated grease, and two common gauge calibration oils. In addition, an aqueous-based gauge fluid was investigated.

Table 1 Pressure Gauge Descriptions

Gauge No. Manufacturer Material Range Configuration

1 2 3 4 5 6 7 8 9 10 -1 1 12 13

Bourdon Wecksler Wecksler Heise Heise Heise Martin Decker Wecksler Wecksler Bourdon Bourdon Bourdon Baurdon

SS' SS' ss' SS' ss' ss' SS' ss' ss' ss'

Brass Brass ss'

Low Pressure Odooo psig 0-100 psig 0-500 psig 0-2000 psig 0-30 psig 0-1500 psig 0-60oO psig 0-5000 psig High Pressure Low Pressure Low Pressure High Pressure

OEb CE' CE' OEb OEb OEb OEb OEb OEb CE" CE" CE" OEb

ss = s t a i n l e s s slcci OE = O p e n e n d d f l o w h g h CE = Closcdcndcd

4

Table 2 Instrumentation Descriptions

Instrument Manufacturer Type No.'

1 2 3 4 5 6 7 8 9 10 11 12 13

TD-Statham Teledyne Taber Bendix Televac Teledyne Teledyne KSC Work Station Televac Bendix Teledyne Tel ed y ne Wecksler Fisher Porter

Pressure Transducer Pressure Transducer Thermocouple Vacuum Gauge Vacuum Gauge Pressure Transducer Unknown Thermocouple Thermocouple Differential Pressure Transducer Differential Pressure Transducer Bourdon Gauge Flow meter

0-50 psia 0-30 psig NA' NA' NA'

0-2OOO psig NA' NA' NA'

0-15 psid 0-1 psid

04000 psig NA'

N A = Not Available

A standard solution of contaminants was prepared with the five organic compounds (Table 4). One gram of each compound was combined and diluted to 100 ml with CFC 113. The solubility of one contaminant, Krytox@' 240AC, was slight in CFC 113. Uniformity of this 5- component mixture was maintained with constant agitation of the nonhomogeneous mix. An aqueous-based standard was prepared using DwyeP fluid by diluting 10 grams of DwyeP concentrate to 100 ml with tap water.

5.5 Contamination Procedure

Each test article was cleaned using standard WSTF cleaning procedures, and the cleanliness level was verified to meet 50A per JSCM 5322 (NASA, 19S4). The cleaned and verified articles were weighed and contaminated with a known amount of standard solution. The solvent carrier for the standard solution was evaporated, the test article was reweighed, and the contaminated weight was recorded. The specimens were contaminated with 200,400, or 600 pl of the standard Samponent mix corresponding to 10, 20, or 30 mg of added contaminant, depending on the relative surface area. Test articles contamhated with the DwyeP fluid solution were contaminated by adding 200 pl of the standard solution.

Test coupons were contaminated on one side and then allowed to set overnight before recording the pretest weight so that the carrier solvent would evaporate. Simulated Bourdon ? u b a were contaminated and allowed to s d for a minimum of 48 hours before recording the contaminated weight. These tubes were not contaminated with DwyeP fluid because the water carrier could not be reliably removed to determine the contaiiinatd weight. For test hardware, weights were not taken because the weights of the test articles were too great and exceeded the capacity of the balance for the accuracy requirements.

5

Table 3 Candidate Solvents and their Properties

Solvent Chemical Formula

Surface NVR Toxicity Boiling F l z h Vapor (mg') PELb/TLVo Point Pressure Tension Point

("C) ("C) (mm Hg) (dyneslcm) OPm)

48 None 284 17 0.1 lo00 32 0.4 25 24 0.6 loo0

58 29 2.4 50

69 -22 124 18 N A ~ 50 NA 40

CFC-113 GF3C13 121 None 14 ' Tetrachloroethylene w 4

8.8 44.6 o\ Ethanol GH5OH 78 Trichloroethylene C2CI3H 8'7 None HCFC-225d C3FsC12H . 5 1-56 None 1371175 17 0.1 5@ n-Hexane ca,4 tert-Butylmethylether CH,WCH,), ' 55 -2 8 245 NA

' Measured average of two ample8 b Permissible oxposum ltnit

Threihold knit value ' 45% H C F C - m

55% IiCFC-225cb Interim value, fml value not edbliahed NA Not Available

Table 4 Contaminant Descriptions

Contaminant Description

m o x a 240AC Pdluoroalkylpolyether Grease Mil-H-83282 Synthetic Hydrocarbon Hydraulic Fluid Mil-H-5606 Petroleum-based Hydraulic Fluid Spinesstic 22 Petroleum Lubricating Oil Sebacate di-Z&yl hexyl sebacate, ester

(Gauge Calibration Fluid) DwyeP Indicating Fluid, Compound Mixture Used in Flow Measurement Fluorescent Green Concentrate Devices TypicaIly Diluted With Water in Use

To determine the accuracy of additions of the S-component mix for test hardware, a series of 17 coupons was contaminated with 200-4 additions, and the average contaminated weight was determined to be 9.64 & 1.06 mg.

5.6 Cleaning Mefhod Description

Following contamination, the coupons were cleaned by flowing 50 ml of the test solvent over the coupon and collecting the solvent in a clean beaker. The test coupon was then allowed to completely dry, and the coupon was rewzighed to determine the amount of contaminant that was removed. Aluminum coupons were used for the majority of testing except for testing ivith DwyeP fluid where stainless-steel ooupons were used because of concern that corrosion of the aluminum could occur with the fluid.

Simulated Bourdon tubes were cleaned by removing both end fittings and flowing 100 ml of the test solvent through the tubes. The solvent was collected for NVR determination. The tubes were allowed to dry, and the posttest weight was recorded.

Test hardware were cleaned using the portable gauge-cleaning station shown in Figure 1. This panel facilitated the cleaning of gauges with the test so!vents. The basic panel design was similar to those used at KSC and WSTF. The panel allows for either a one-time flow- through of solvents for verification or a recirculation of solvents for cleaning. The test article is either purged with nitrogen or evacuated to remove the test solvent. A separate spray wand i s attached for spray cleaning of componznts. The panel is placed in a fume hood that allows the testing of toxic solvents. The panel is equipped with 5-1 filters and variable pressure relief settings. For this effort, the cleaning panel pressure did not ex& 35 psig. Before tpsting, a series of verification tests was performed to establish procedures and ensure proper operation.

7

I

Figure 1 Gauge Cleaning Panel

Three techniques were used to allow for the different configurations of the test articles. These techniques are provided as follows:

Open-ended gauges were flushed with 500 ml of solvent. The last 100 ml was retained for NVR determination.

0 Closedended gauges were evacuated and filled with solvent five times. Each time the solvent was collected, and the flushes were combined for NVR determination.

Transducers, vacuum gauges, and other sensors were flushed with 500 ml of test solvent from the spray wand. The last 100 ml was collected for NVR determination.

After each device was experimentally cleaned with the test solvent, it was again flushed with 100 ml of CFC 113. This final flush was accomplished by either flowing the CFC-I 13 through the gauge in the open-ended configuration, including gauges that were cleaned in the closedended configuration, or by insetting a capillary tube in the end of the closedended gauge and flowing solvent through the capillary. The CFC 113 was collected for a NVR determination. The residue that was extracted from the final flush of CFC 113 was assumed to conb iu any remaining contaminant left behind by the test solvent. The percent removal was then determined by calculation using the following:

100 - 1100 x ((A - B)/C)] = percent removal

where: A = mg NVR CFC 113 rinse B = mg NVR Blank C = mg of.contaminant

8

5.7 NVR Determination

All NVR's were determined gravimetrically where 100 ml of the final rinse solvent was evaporated and condensed to 10 ml. The solvent was transferred to a tared, petri dish and then heated in an oven at 105 "C for 30 minutes. The final weight of the dish was recorded and the mass difference was calculated as the NVR. The high boiling solvents, TCE and PCE, were evaporated to 10 ml using a hot plate. NVR determinations were accomplished not only for the cleaning testing previously described, but also for the neat solvent to determine the as-received purity (Table 3).

5.8 NVR Recovery Pr&ures

To determine the ability of the solvent to be used as a verification fluid, 10 mg of the 5-component mixture was added to 100 ml of test solvent. The solvent was then subjected to the NVR procedure. The remaining weight of the residue was measured to determine the per cent recovery .

5.9 Oxygen Compatibility Testing

Two types of tests were conducted on the test solvents that were considered for cleaning of oxygen systems to determine the compatibility of the solvent with oxygen: Autogenous Ignition Temperature (AIT) and Standard Ambient Liquid Oxygen Mechanical Impact.

AIT was determined for the test solvents according to the procedures described in ASTM G 72 (ASTM, 1992a). The AIT for each solvent was determined at two pressures: 50 psig and 2000 psig.

Standard ambient liquid oxygen mechanical impact was accomplished for the test solvents according to the procedures described in ASTM D 2512 (ASTM, 1992b).

6.0 Results

6.1 Coupons

The average percent removal of the test contaminants from the coupons is given in Table 5. The results indicate comparable removal efficiencies for all of the candidate solvents in removing organic contaminants contained in the S-component mix. PCE, which has the highest surface tension (lowest wetting ability), yielded the lowest average removal efficiency for the organic contaminants. Results of testing with the aqueous-based contaminants in DwyeP fluid, showed a wide range of removal efficiencies (37 through 96 percent). Some corrosion was observed for test coupons contaminated with DwyeP fluid which resulted in skewed results for PCE.

6.2 Simulated Gauges

The percent removal by the candidate solvents of the 5 a m p o n e n t mix of test contaminants from simulated Bourdon tubes is shown in Table 6. Results of testing with the

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Table 5 Average Percent Removal of Contaminant from Coupons

Solvent Contaminant Contaminant DwyeP Fluid S-Component M U

CFC 113 Ethanol Tetrachloroethylene Tl3ME + Hexane HCFC 225 Trichloroethylene

80.P 96.3' m

85.3' 37.Q NAd

9 4 . v 86.9 76.5'

79.P 94.P

97 .r

' Average of 3 coopom Average of 6 covpons ND = Not Determintd (excess corrosion products Lrerfclpd with NVR ddermhtion) NA = Not Accompkhad

Table 6 Average Percent Removal of 5-Component Contaminant Mixture from Simulated Gauges

Test Solvent Removal

CFC 113 Ethanol Tetrachloroethylene TJ3ME + Hexane HCFC. 225 Trichloroethylene

96.8' 62.8' 78.7' 77.2'

95.5' 87.r

Average of 2 tcste

Average of 3 teats

10

simulated Bourdon tubes are much more comparable to actual gauges than the coupon results. The results indicate that the solvents can be divided into three groups based on their average percent removal of the organic mix. EtOH has the lowest removal efficiency followed by PCE and TBME/n-hexane, which removed approximately 75 percent of the contaminant. The best solvents based on the results of simulated Bourdon gauges are HCFC-225 and TCE, which cleaned with nearly equal efficiency to CFC-113. TBMEh-hexane was omitted from further testing because the results indicate marginal cleaning ability and high flammability and toxicity.

6 3 TestHardware

63.1 Pressure Gauges

Tables 7 through 11 contain the results of cleaning test hardware pressure gauges that were contaminated with organic contaminants contained in the standard S-wmponent mix. The results are for the four remaining candidate solvents and CFC-113. The gauges are identified as closed- or open-ended. Following testing with the first three solvents, the number of gauges cleaned in the study was reduced to seven: four open-ended and three closed-ended. However, during the cleaning operation for the CFC-I 13 study (Table 11) Gauge 9 failed. .

Table 7 Results for Cleaning of Gauges Contaminated with Organic Contaminants with

Tetrachloroethylene Solvent

Gauge' Pressure Configuration Contaminant Final NVR % (Psig) (mg) (mg) Removal

1 2 3 4 5 6 7 8 9 10 I t 12

LOW

6ooo 100 500

2000 30

1500 6OOo 5000 High L O W

L O W

OJ? CE" CE' OEb O F OJ? OE' OEb O F C F CE' CE'

20 20 20 30 30 30 30 20 20 10 10 10

0.3 13.1 9.0 2.6 1.1 0.4 0.4 0.4 0.4 0.3 0.3 1.4

98.5 34.5 55.0 91.3 96.3 98.7 98.7 98.0 98.0 97.0 97.0 86.0

' Full description of gauge is containcd in Table 1. ' OE = Opencndcd E CE = Closedendcd

I 1

Table 8 Results for Cleaning of Gauges Contaminated with Organic Contaminants with

Ethanol Solvent

Gauge' Pressure Configuration Contaminant Final NVR x @sig) (mg) (mg) Removal

1 2 3 4 5 6 7 8 . 9 10 11 12

LOW

m 100 500

2Ooo 30

1500 6OOo 5OOo High LOW

LOW

OEI CE' C F OE? OE? OJ? OJ? OF? OE? CE' CE' CE'

20 20 20 30 30 30 30 20 20 10 10 10

2.9 3.2 0.1 f .5 3.8 7.2 7.7 1.8 0.8 1.7 4.7 0.9

85.5 84.0 99.5 95.0 87.3 76.0 74.3 91.0 96.0 83 .O 53.0 91.0

Full dcscriptioa of gauge is containad in Table 1. OE = O p e n 4 CE = Closedcndod

~~~~ ~ _ ~ _ ~ ~

Table 9 Results for Cleaning of Gauges Contaminated with Organic Contaminants with

Trichloroethylene Solvent

Gauge' Pqessure Configuration Contaminant Final NVR X (Pa) "1 (mg) Removal

1 2 3 4 5 6 7 8 ? 10 11 12

LOW

6Ooo 100 500

2000 30

1500 6Ooo 5 m .

High LOW

LOW

OF? CF CE' OF OF O F OE O E @E+ C F CE? CF

34.8 34.8 34.8 52.2 52.2 52.2 52.2 34.8 34.8 17.4 17.4 17.4

0.3 15.6 2.8 1.2 1 .o 0.6 0.5 1.2 1.9 2.6 0.9 1.7

99.1 55.2 92.0 97.7 98.1 98.9 99.0 96.6 94.5 85.1 94.8 90.2

* Full description of gauge is contained in Table 1. OE = Opcncodcd CE = Closcddcd

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Table 10 Results for Cleaning of Gauges Contaminated with Organic Contaminants with

HCFC-225 Solvent

Gauge' Pressure Configuration Contaminant Final NVR '96 @sig) (mg) (mg) Removal

1 LOW OE' 20 0 100.0 2 6OOo CE" 20 0 100.0 3 100 CE" 20 1.3 93.5 8 6Ooo O P 20 0 100.0 9 SO00 OE' 20 0.1 99.8 12 LOW CE" 20 0 100.0 13 High O E 20 0 . 100.0

' Full description of gauge is contained in Table 1 . OE = Opcnendcd CE = Closedcndcd

Table 11 Results for Cleaning of Gauges Contaminated with Organic Contaminants with

CFC-113 Solvent

Gauge' Pressure Configuration Contaminant Final NVR % (Psig) (mg> (mg) Removal

1 LOW OEb 20 0.3 98.5 2 6OOo CE" 20 0.1 99.5 3 100 CE' 20 0.1 99.5 8 6OOo OE' 20 2.3 88.5 12 LOW CE' 20 0.3 98.5 13 High OEb 10 0.1 98.5

13

Full dcscription of gauge is contained in Table 1 . OE = Open-ended CE = Closedcnded

In general, all of the solvents tested were able to remove the organic contaminants. The high-pressure Bourdon tubes are configured with a very narrow tube which inhibits their ability to be cleaned, and therefore, gave the lowest removal effrciencies. Gauges cleaned in the closed-ended configuration also resulted in decreased removal efficiencies.

The data contained in Table 12 is a summary of average percent removal for each of the solvents and compares cleaning efficiencies in the closed- and open-ended configurations. EtOH, as expected, is the poorest of the solvents tested in removing the organic contaminants contained in the Samponent mix, with an average percent removal of 84 percent. Results of testing with EtOH show little dependance on configuration. An examination of the data in Table 8 reveals quite a bit of variability in the results from one test to the next.

PCE was determined to have an average percent removal of 87 percent; however, the cleaning results for PCE show a large dependance on configuration (74 percent removal for closed- ended gauges versus 97 percent removal for open-ended gauges). This dependance is most probably due to the high surface tension for PCE which hinders its ability to wet the inside of closed-ended gauges effectively. This same effect is seen in TCE which had an overall efficiency of 92 percent for the 12 gauges with 84 percent in the closedended configuration and 98 percent removal in the open-ended configuration.

HCFC-225 showed the best performance of the four solvents tested to date with a cleaning efficiency equal to or greater than CFC-113. In fact, the first data set run with HCFC-225, the results of which are not reported, the cleaning efficiencies were consistently greater than 100 percent due to the fact that the HCFC-225 was removing contaminants left behind in the previous cleaning with CFC-113. The cleaning effectiveness observed with HCFC-225 seems to be independent of configuration.

To further evaluate the effectiveness of each of the test solvents, a series of tests was performed where a gauge was rinsed with five 100-ml rinses of the test solvent, and an NVR was determined for each rinse (Table 13). The data were determined using Gauge 1, which was a low-pressure flow-through gauge. The results indicate the effectiveness of each solvent in removing contaminant during the cleaning process. EtOH is shown to remove a fairly

Table 12 Summary and Comparison of Solvent Cleaning Efficiencies

Solvent Average X Removal CF Gauges OEb Gauges Total

Tetrachloroethylene 73.9 Ethanol 82.1 Trichloroethylene 83.5 HCFC-225 99.7 CFC-113 99.2

97.1 86.4 97.7 98.4 95.3

87.4 84.6 91.8 98.9 97.2

CE = Closcdcndcd OE = Opcncnded

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Table 13 Solvent Rinse and NVR Recovery Results

Solvent NVR (mp) 1 st . 2nd 3rd 4th 5th

Rinse Rinse Rinse Rinse Rinse Total:

Tetrachloroethylene 12.8 2.1 0.9 1 .o 0.5 17.3 Ethanol 2.1 2.1 2.1 2.4 0.1 8.8 Trichloroethylene 15.0 0.5 0.4 0.1 0.1 16.1 H CFC-225 17.7 3.2 1.7 1.2 0.8 24.6 CFC- 1 13 16.5 0.8 0.5 0.3 0.3 18.4

small consistent amount of contaminant for each rinse, while the other solvents removed the majority of the contaminant during the first 100-ml rinse. This result may explain the wide variation in results for EtOH from gauge to gauge. The test results for this comparison are consistent with the results for the gauge study (Table 12), in that, HCFC 225 gave the highest NVR for the first flush and EtOH gave the lowest.

Table 14 contains the results of testing using DwyeP fluid as the contaminant. This testing was only performed for EtOH because it was felt to be the most effective at removing aqueous-based contaminants. The data shown in Table 14 was skewed because the corrosion products produced during the contamination process interfered with the NVR determinations. After the EtOH test, DwyeP fluid was omitted from further testing because of its incompatibility with the stainless-steel Bourdon tubes.

6.3.2 Instrumentation

Tables 15 through 17 contain the results of cleaning instrumentation that had been contaminated with the organic contaminants contained in the standard 5amponent mix. As previously mentioned, the instrumentation was cleaned using a spray wand rather than dipping or filling the transducer cavities with solvent. The use of the spray wand was facilitated for most of these gauges since the sensing unit, a metal diaphragm in most cases, was clearly visible. The exception were Gauges 12 and 13, which were the Bourdon tube-type gauge and a rotameter-type flowmeter, respectively. The cleaning efficiencies for these gauges are very low, and demonstrate that the technique used was inappropriate for this type of gauge, regardless of the solvent used.

In general, the three solvents tested all performed well in the cleaning of transducers and sensors; a comparison of average cleaning efficiencies is given in Table 18. The removal percentages do not include results obtain& for Gauges 12 and 13. EtOH shows the poorest performance while PCE shows the best performance; however, there is little difference between any of the three solvents when one considers the standard deviation between data sets. No testing was accomplished with HCFC-225 because this solvent was added late in the pogram, and previous results did not- indiate thdt the testing with transduczrs and instrumentation distinguished solvent ability.

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Table 14 Results for Cleaning of Gauges Contaminated with Aqueous Contaminants with

Ethanol Solvent

Gauge' Pressure Configuration Contaminant Final NVR %J (Psig) ( 4 (mg) Removal

1 2 3 4 5 6 7 8 9 10 1 1 12

L A W

6OOo 100 500

2000 30

1500 6Ooo so00 High LOW L O W

OE? CE' CF OEb OE? OF OEP OF OEb CE' CE' CE'

2 2 2 2 2 2 2 2 2 2 2 2

0.6 3.8

10.1 0.2 1.3 0.1 6.6 0.7 0.2 0.9 0.6 0.1

70.0 ND/ NDd 90.0 35.0 95.0 NDd 65 .O 90.0 55.0 70.0 95.0

' Full description of gauge is contained in Table 1. OE = Opcn-cndcd ' CE = Closcd-endcd ' ND = Not Determined (corrosion producf interfered with NVR ddcrmination) NOTE: Ekca~oe of Ihc physical propertics of DwyeP fluid, only 2 mg could be efficiently added to

each specimen.

Instrumentation was also contaminated with DwyeP fluid and cleaned with EtOH using a spray wand technique. The reiults of this testing are given in Table 19; the average for the data set given in Table 19 is 85.7 percent removal of the aqueous-based contaminants. As with the gauge testing, corrosion products were also observed in these tests.

6.4 NVR Recovery Results

The results of testing to determine the ability of the solvents to be used as a verification fluid are given in Table 20. The results indicate that with exception of PCE, the performance of the solvents is comparable to CFC-113. For PCE, there is some indication that the solvent could codistill contaminants during the NVR determination process, resulting in an artificially low NVR and a false-positive result. This result is consistent with the fact that PCE has a relatively high boiling point.

6.5 Oxygen Compatibility Results

Oxygen compatibility testing was accomplished for PCE, TCE, and HCFC 225. The results are provided in the following paragraphs.

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Table 15 Results of Instrumentation Contaminated with Organic Contaminants with

Tetrachloroethylene Solvent

Number? Description Contaminant Final NVR x (mg) Removal “1

1 2 3 4 5 6 7 8 9 10 1 1 12

Pressure Transducer 10 Pressure Transducer 10 Thermocouple 10 Vacuum Gauge 10 Vacuum Gauge 10 Pressure Transducer 10 KSC Work Standard 10 Thermocouple 10 Thermocouple 10

Bourdon Gauge, 60oO psig 10

Differential Pressure Transducer 20 Differential Pressure Transducer 20

0.2 0.2 0.8 0.1 0.1 0.1 0.1 0.1 0.8 0.3 0.1 4.8

98.0 98.0 92.0 99.0 99.0 99.0 W.0 99.0 92.0 98.5 99.5 52.0

’ Full description is contained in Table 2.

Table 16 Results of Instrumentation Contaminated with Organic Contaminants with

Ethanol Solvent

Number‘ Description Contaminant Final NVR !?I

(mg) (mg) Removal

1 2 3 4 5 6 7 8 9 10 1 1 12 13

Pressure Transducer Pressure Transducer Thermocouple Vacuum Gauge Vacuum Gauge Pressure Transducer KSC Work Standard Thermocouple Thermocouple Differential Pressure Gauge Differential Pressure Gauge Bourdon Gauge, 6OOO psig Flowmeter

10 10 10 10 10 10 10 10 10 20 20 10 10

0.3 0.1 2.3 0.2 1,. 1 0.1 0.1 0.5 2.7 5.1 1.9 8.2 4.7

97.0 99.0 77.0 98.0 89 .O 99.0 99.0 M.0 73.0 74.5 90.5 18.5 53.0

Full description is contained in Tabk 2.

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Table 17 Results of Instrumentation Contaminated with Organic Contaminants with

Trichloroethylene Solvent

Number' Description Contaminant Final N VR x fmg) (mg) Removal

1 2 3 4 5

7 8 9 10

6 .

Pressure Transducer Pressure Transducer Thermocouple Vacuum Gauge Vacuum Gauge Pressure Transducer KSC Work Standard Th ermocou p 1 e Thermocouple Differential Pressure Tran

17.4 17.4 17.4 17.4 17.4 17.4 17.4 17.4 17.4 34.8

11 Differential Pressure Transducer 34.8 12 Bourdon Gauge, 6OOO psig 17.4

duce

0.1 99.4 0.1 99.4 0.9 94.8 0.1 99.4 9.3 46.6 0.2 98.9 0.1 99.4 0.3 98.3 1.5 91.4 1.7 95.1 0.4 98.9

12.8 26.4

Full description is contained in Table 2.

Table 18 Average Percent Removal for Solvent Cleaning of Transducers and Instrumental Sensors

Contaminated with Organic Contaminants

% Removal Solvent

Tetrachloroethylene Ethanol Trichloroethylene

97.4 90.1 92.9

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Table 19 Results of Cleaning Sensors and Transducers Contaminated with Aqueous Contaminants

with Ethanol Solvent

Number Description Contaminant Final NVR 96 Removal (mg) (mg>

1 2 3 4 5 6 7 8 9 10 1 1 12 13

Pressure Transducer 2 Pressure Transducer 2 Thermocouple 2 Vacuum Gauge 2 Vacuum Gauge 2 Pressure Transducer 2 KSC Work Standard 2 Thermocouple 2 Th ennocouple 2 Differential Pressure Transducer 2 Differential Pressure Transducer 2 Bourdon Gauge, 6OoO psig 2 Flowmeter 2

0.3 0.1 0.1 0.1 9.1 0.1 0.1 0.3 0.3 3 0.3

29.4 3.4

85.0 95.0 95.0 95.0 95.0 95.0 95 .O 85.0 85.0 25.0 92.5 NDb NDb

Full description is contained in Table 2. ' ND = Not Determined (corrosion product interfcrcd with NVR d c t c d i o n )

Table 20 NVR Recovery Results

Solvent R NVR Recovered

Tetrachloroe-th ylene Ethanol Trichloroethylene CFC-113 HCFC-225

74.0 92.4 87.5 88.3 94.6

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The results of A I T testing for the three solvents evaluated are given in Table 21. An AlT was observed for both PCE and TCE, while HCFC-225 did not ignite under the test conditions. The AIT recorded for TCE is quite low compared to other compounds that are typically considered oxygen compatible. A slow temperature rise was observed during the 50 psi test for both the PCE and TCE, indicating that at that pressure both compounds burned rather slowly.

No reactions were observed for any of the solvents tested by mechanical impact at an impact energy of 72 ft-lbs. The results of mechanical impact indicate that none of the solvents evaluated are sensitive to ignition by mechanical impact when tested as a neat solvent.

7.0 Condusions

Based on the testing to date, the following conclusions regarding the solvents evaluated in this investigation are provided as follows:

e All the solvents tested are capable of removing organic contaminants; however, with the exception of EtOH, they have only limited capabilities in the removal of aqueous-based contaminants.

e Not considering cost or toxicity concerns, of the solvents evaluated, HCFC-225 shows the best cleaning performance followed in descending order by TCE, PCE, and EtOH. When cost and toxicity are considered HCFC-225 is similar in toxicity to TCE and PCE and is significantly more expensive.

. TBME/n-hexane, while demonstrating cleaning efficiencies similar to EtOH, which.is nontoxic, and perchloroethylene, which is nonflammable, is both toxic and flammable and was dropped from testing after the initial evaluation.

e Of the solvents tdted, PCE has the highest boiling point and is the most difficult to remove ftom the part. In addition, PCE may codistill contaminants during NVR determination, resulting in a false-positive NVR.

0 None of the solvents tested for compatibility with oxygen demonstrated gross incompatibilities. No reactions were observed for mechanical impact; however, an AIT was measured for both PCE and TCE, with the AIT for TCE being quite low. No AIT was recorded for HCFC-225 under the test conditions.

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Table 21 Autoignition Temperature Determination Results

Solvent AIT ("(3 50 psi 2000 psi

Tetrachloroethylene Trichloroethylene HCFC-225

136 108 NI'

161 77 NP

NI = No Ignition (did not ignitc at maximum tcst tempcra&~rr: of 450 'C)

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References

Antin, Neil. NAVSEA Report on: Aqueous Oxygen Cleaning Products and Processes. Naval Sea Systems Command, Arlington, VA, March 1994.

ASTM G 72. " AotogenousIgnitionTemperatureof Liquid and Solids in a High-Pressureoxygen- Enriched Environment." American Society ofTesting and Materials, Reapproved 1991, Volume 14.02, Philadelphia, PA, 1992a.

ASTMD 2512. "Compatibility of Materials with Liquid Oxygen (Impact Sensitivity Threshold and Pass-Fail Techniques." American Society of Testing and Materials, Volume 15.03, Philadelphia, PA, 1992b.

NASA. Contamination Control Requirements Manual. JHB 5322, Revision C, Institutional Safety and Quality Division, Lyndon B. Johnson Space Center, February 1994.

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Distribution

Organization No. of Copies

Kennedy Space Center

DM-MSL-1 / Gale Allen

Naval Sea Systems Command

NAVSEA 03Y12 / Neil Antin

NASA Johnson Space Center White Sands Test Facility

Laboratories Oftice

AlliedSignal Technical Services Corp. Team Johnson Space Center White Sands Test Facility

Publications Oftice Technical Library

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3

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