AMERICAN MOBILE RESEARCH, INC.
1955 CBS COURT (307) 235-4590 OFFICE
CASPER, WYOMING 82604 (307) 265-4489 FAX
     SULFUR PASSIVATION STUDY ON VARIOUS METAL SAMPLING CYLINDERS
     IN DECEMBER, 2002, AMERICAN MOBILE RSEARCH, INC. CONDUCTED A CONTROLLED
STUDY OF THE REACTIVITY OF SEVERAL COMMON SULFUR SPECIES, FOUND TO EXIST IN
NATURAL GAS AND NATURAL GAS LIQUIDS, TO THE LINING OF VARIOUS METAL SAMPLING
CYLINDERS CURRENTLY USED TO OBTAIN THESE PRODUCTS. THIS STUDY WAS PERFORMED
SO THAT WE COULD BETTER UNDERSTAND THE REACTIVENESS BETWEEN THE CYLINDERS
AVAILABLE FOR PRODUCT SAMPLING AND VARIOUS SULFUR SPECIES. PASSIVITY IS A PROPERTY
SHOWN BY IRON, ALUMINUM, AND RELATED METALS INVOLVING THE LOSS OF THEIR
NORMAL CHEMICAL ACTIVITY WHEN SUBMITTED TO A CORROSIVE ENVIRONMENT.
     THE SCOPE OF THE STUDY WAS TO DETERMINE HOW EACH SULFUR SPECIES REACTED
WITH EACH DIFFERENT TYPE OF METAL CYLINDERS, OVER A PERIOD OF TIME. EACH OF THESE
PRIMARY TYPES OF CYLINDERS WERE USED FOR THIS STUDY:
1) CARBON STEEL
2) ALUMINUM
3) TEFLON-LINED ALUMINUM
4) STAINLESS STEEL
5) TREATED STAINLESS STEEL  (SULFINERT BRAND)
     EACH CYLINDER WAS FILLED TO A PRESSURE OF 1000 PSIG WITH AN NBS TRACEABLE
STANDARD GAS CONTAINING APPROXIMATELY 10 PARTS PER MILLION / VOLUME OF THE
FOLLOWING SULFUR COMPOUNDS:
SULFUR SPECIES CONCENTRATION
HYDROGEN SULFIDE  10.1 PPM/VOLUME
CARBONYL SULFIDE  10.2 PPM/VOLUME
METHYL MERCAPTAN  10.1 PPM/VOLUME
ETHYL MERCAPTAN  10.4 PPM/VOLUME
2-PROPYL MERCAPTAN  10.9 PPM/VOLUME
DIMETHYL SULFIDE  10.2 PPM/VOLUME
DIMETHYL DISULFIDE  10.4 PPM/VOLUME
   UPON FILLING THESE CYLINDERS WITH THE SULFUR MIXTURE, ANALYSIS WAS PERFORMED
ON EACH CONTAINER TO DETERMINE THE AMOUNT OF PASSIVATION OF EACH SULFUR
SPECIES, VERSUS THE AMOUNT OF TIME THE STANDARD GAS WAS IN EACH CYLINDER.
THE ANALYSIS OF THESE SULFUR COMPOUNDS WERE PERFORMED ON A SIEVERS MODEL 355
SULFUR CHEMILUMINESCENCE DETECTOR CHROMATOGRAPH* AT INTERVAL OF 1 HOUR,
2 HOURS, 24 HOURS AND 72 HOURS AFTER SUBMITTING THE SULFUR STANDARD GAS INTO
EACH TYPE OF CYLINDER.
     THE RESULTS OF EACH CYLINDER ANALYSIS WERE CALIBRATED AND COMPARED TO
TWO PRIMARY NBTS SULFUR STANDARDS, PRODUCED BY DCG PARTNERSHIP, LTD.
THE RESULTS OF EACH CYLINDER TESTED ARE OUTLINED BELOW:
TYPE OF CYLINDER.................... STAINLESS STEEL (304)
SAMPLE TIME IN CYLINDER
SULFUR COMPOUND

 1 HOUR

 % LOSS

 24 HOURS

 % LOSS

 72 HOURS

 % LOSS

HYDROGEN SULFIDE

 0.030 PPM

99.70%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

CARBONYL SULFIDE

10.175 PPM

0.25%

 9.913 PPM

2.81%

 9.841 PPM

3.52%

METHYL MERCAPTAN

 1.550 PPM

84.65%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

ETHYL MERCAPTAN

 2.593 PPM

75.07%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

2-PROPYL MERCAPTAN

 2.425 PPM

77.75%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

DIMETHYL SULFIDE

10.200 PPM

0.00%

 9.907 PPM

2.87%

 9.640 PPM

5.49%

DIMETHYL DISULFIDE

 10.306 PPM

0.91%

 9.758 PPM

6.17%

 9.447 PPM

9.16%

TYPE OF CYLINDER.................... ALUMINUM
SAMPLE TIME IN CYLINDER
SULFUR COMPOUND

 1 HOUR

 % LOSS

 24 HOURS

 % LOSS

 72 HOURS

 % LOSS

HYDROGEN SULFIDE

 2.806 PPM

72.22%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

CARBONYL SULFIDE

 9.991 PPM

2.05%

 9.163 PPM

10.17%

 8.734 PPM

14.37%

METHYL MERCAPTAN

 2.052 PPM

79.68%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

ETHYL MERCAPTAN

 0.363 PPM

96.51%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

2-PROPYL MERCAPTAN

 0.092 PPM

99.16%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

DIMETHYL SULFIDE

 10.030 PPM

1.67%

 9.571 PPM

6.17%

 8.420 PPM

17.45%

DIMETHYL DISULFIDE

 10.264 PPM

1.31%

 9.790 PPM

5.87%

 8.837 PPM

15.03%

TYPE OF CYLINDER.................... CARBON STEEL
SAMPLE TIME IN CYLINDER
SULFUR COMPOUND

 1 HOUR

 % LOSS

 24 HOURS

 % LOSS

 72 HOURS

 % LOSS

HYDROGEN SULFIDE

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

CARBONYL SULFIDE

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

METHYL MERCAPTAN

 3.018 PPM

70.12%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

ETHYL MERCAPTAN

 5.249 PPM

49.53%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

2-PROPYL MERCAPTAN

 4.826 PPM

55.73%

< 0.010 PPM

100.00%

< 0.010 PPM

100.00%

DIMETHYL SULFIDE

 8.154 PPM

20.06%

 0.916 PPM

91.02%

 < 0.010 PPM

100.00%

DIMETHYL DISULFIDE

 7.593 PPM

26.99%

 2.530 PPM

75.67%

< 0.010 PPM

100.00%

TYPE OF CYLINDER.................... TEFLON-LINED ALUMINUM
SAMPLE TIME IN CYLINDER
SULFUR COMPOUND

 1 HOUR

 % LOSS

 24 HOURS

 % LOSS

 72 HOURS

 % LOSS

HYDROGEN SULFIDE

10.086 PPM

0.14%

10.047 PPM

0.53%

10.022 PPM

0.77%

CARBONYL SULFIDE

10.169 PPM

0.30%

10.118 PPM

0.80%

10.102 PPM

0.96%

METHYL MERCAPTAN

10.020 PPM

0.79%

10.009 PPM

0.90%

 9.976 PPM

1.23%

ETHYL MERCAPTAN

10.355 PPM

0.43%

10.282 PPM

1.14%

10.091 PPM

2.97%

2-PROPYL MERCAPTAN

10.872 PPM

0.26%

10.790 PPM

1.01%

10.503 PPM

3.64%

DIMETHYL SULFIDE

10.147 PPM

0.52%

10.056 PPM

1.44%

 9.981 PPM

2.15%

DIMETHYL DISULFIDE

10.294 PPM

1.02%

10.173 PPM

2.18%

10.009 PPM

3.76%

TYPE OF CYLINDER.................... TREATED STAINLESS STEEL
SAMPLE TIME IN CYLINDER
SULFUR COMPOUND

 1 HOUR

 % LOSS

 24 HOURS

 % LOSS

 72 HOURS

 % LOSS

HYDROGEN SULFIDE

10.097 PPM

0.030%

10.090 PPM

0.100%

10.086 PPM

0.14%

CARBONYL SULFIDE

10.198 PPM

0.020%

10.196 PPM

0.040%

10.192 PPM

0.08%

METHYL MERCAPTAN

10.088 PPM

0.120%

10.079 PPM

0.210%

10.076 PPM

0.24%

ETHYL MERCAPTAN

10.391 PPM

0.090%

10.298 PPM

0.980%

10.275 PPM

1.20%

2-PROPYL MERCAPTAN

10.885 PPM

0.140%

10.878 PPM

0.210%

10.837 PPM

0.58%

DIMETHYL SULFIDE

10.200 PPM

0.000%

10.192 PPM

0.080%

10.141 PPM

0.58%

DIMETHYL DISULFIDE

10.399 PPM

0.010%

10.390 PPM

0.100%

10.368 PPM

0.31%

DISCUSSION OF RESULTS

     PRIOR TO SAMPLING A GAS OR LIQUID HYDROCARBON, WHETHER FOR TREATER DESIGN
OR ABSORBER ANALYSIS, THE ANALYST SHOULD HAVE SOME UNDERSTANDING OF WHAT
SULFUR COMPOUNDS MAY BE PRESENT IN THE SOURCE TO BE SAMPLED. THE RATE OF
PASSIVIATION, OR % LOSS AS EXPRESSED IN THE ABOVE REPORT, SHOWS HYDROGEN
SULFIDE IS MOST REACTIVE WITH CARBON, STAINLESS AND ALUMINUM.  WITHIN 1 HOUR OF
STARTING THE STUDY, MOST OF THE HYDROGEN SULFIDE WAS PASSIVATED IN CARBON STEEL
AND STAINLESS STEEL.  ALUMINUM LOST OVER 70% OF THE HYDROGEN SULFIDE THROUGH
PASSIVATION WITHIN 2 HOURS. ONLY TEFLON-LINED ALUMINUM AND TREATED STAINLESS
HELD THEIR HYDROGEN SULFIDE CONCENTRATIONS BEYOND 72 HOURS. BOTH SHOWED LOSSES
OF LESS THAN 1% H2S AT THE 72 HOUR TEST PERIOD.
    
     BOTH, TEFLON LINED AND TREATED STAINLESS SHOWED THE LEAST AMOUNT OF ABSORPTION
OF VOLATILE SULFUR COMPOUNDS DURING THIS TEST PERIOD. REGULAR STAINLESS, ALUMINUM
AND CARBON TYPE CYLINDERS SHOWED SIGNIFICANT LOSS OF VOLATILE SULFURS WITHIN HOURS
OF FILLING THEM. THIS STUDY WAS PRODUCED TO ASSIST ANALYST IN THE DECISION OF WHICH
CYLINDERS PROVIDE THE BEST DEFENSE AGAINST SAMPLE PASSIVATION.
     IT SHOULD BE NOTED THAT LABORATORIES USING THE TEFLON-LINED AND TREATED
STAINLESS SAMPLE CYLINDERS SHOULD PERFORM REGULAR PASSIVATION TESTING OF THEIR
CYLINDERS TO ASSURE THEMSELVES THAT THE CYLINDER WILL CONTINUE TO MAINTAIN
A MINIMAL PASSIVATION OF SULFURS. TESTING PERFORMED ON PURCHASED CYLINDERS HAVE
SHOWN FAILURES, OR SULFUR PASSIVATION, EVEN THOUGH THEY ARE NEW. ROUTINE TESTING
AND DOCUMENTATION OF CYLINDERS USED FOR SULFUR SAMPLING SHOULD BE MAINTAINED
TO DEVELOP A HISTORY ON THE CYLINDERS USEAGE AND TO CONFIRM THE CYLINDERS
ABILITY TO PREVENT PASSIVATION.  ALL SAMPLE CYLINDERS, INCLUDING NEW ONES, SHOULD
BE TESTED REGULARLY.
     ALSO, SAMPLES TAKEN IN THESE CYLINDERS SHOULD BE ANALYZED AS QUICKLY AS POSSIBLE
TO REDUCE THE CHANCE OF PASSIVATION. SAMPLES WHICH REQUIRE TRANSPORTATION TO A
LABORATORY FOR TESTING SHOULD BE SENT BY THE FASTEST METHOD AVAILABLE.  TESTING
LABS CAN NOT BE HELD RESPONSIBLE FOR SAMPLE DEGRADATION WITHIN A CYLINDER. AS THIS
STUDY SHOWS, SAMPLES REQUIRING MORE THAN 72 HOURS TO SHIP AND ANALYZE WILL RISK
AN INCREASED CHANCE FOR SULFUR PASSIVATION TO OCCUR.  TESTING LABS CAN ONLY REPORT
ACCURATE NUMBERS IF THEY RECEIVE THE SAMPLES WITHIN A REASONABLE AMOUNT OF TIME
AFTER SAMPLING.
     BEFORE SAMPLING, CONSULT YOUR LABORATORY TO DETERMINE WHICH SULFUR COMPOUNDS
MIGHT BE PRESENT IN THE TYPE OF GAS YOU ARE SAMPLING. THEN, CHOOSE THE PROPER METAL
TYPE CYLINDER TO STORE THE SAMPLE UNTIL TESTING CAN BE PERFORMED.
     AMERICAN MOBILE RESEARCH, INC. MAINTAINS A LARGE STOCK OF ALUMINUM, STAINLESS,
AND TEFLON LINED ALUMINUM CYLINDERS FOR YOUR SAMPLING NEEDS. CONTACT OUR
LABORATORY, AT 307-235-4590, TO REQUEST THESE CYLINDERS FOR YOUR NEXT SAMPLING
PROJECT.