Figures 2 and 3 compare the transport proper-
ties of 100-foot (30.5-meter) lengths of the
three types of seamless 316L stainless steel
tubing,
1
/
8
" OD x 0.020" wall, using a gas stream
containing 0.500ppmvmethyl mercaptan in heli-
um as the test material.Testswere performed
at room temperature, using a gas flow rate of
40cc/minute.
Figure 2 demonstrates uptake of the sulfur com-
pound by the three surfaces.The performance
of the Sulfinert
®
treated, electropolished surface
is quite dramatic in comparison to that of
untreated electropolished tubing. Sulfinert
®
treated electropolished tubing did not adsorb
methyl mercaptan to anymeasurable extent,
delivering a representative samplewith no
delay.The untreated electropolished tubing, in
contrast, totally adsorbedmethyl mercaptan for
more than 75minutes, and the sulfur gas level
did not stabilize until approximately 130min-
utes. Conventional 316L seamless tubing totally
adsorbedmethyl mercaptan formore than 90
minutes, and the sulfur gas level did not stabi-
lize until approximately 140minutes.
Closely correlated to the adsorption of sulfur
compounds by system components is the subse-
Figure2
Sulfinert® treatedelectropolished
stainless steel tubing (red) doesnot adsorb
methylmercaptan (500ppbv).
Blue—untreatedelectropolished tubing,
violet—commercial grade tubing.
Figure3
Sulfurmemory isprolonged in raw
commercial grade stainless steel tubing (violet).
Red-Sulfinert® treatedelectropolished tubing;
blue-untreatedelectropolished tubing
(500ppbvmethylmercaptan inhelium).
quent release of the adsorbed compounds.
When adsorption of sulfur-containing com-
pounds is prolonged, desorption from the sur-
face also is slow.This “memory” of adsorbed
active compounds can cause long delays in
equilibrating a sample stream. Figure 3 demon-
strates thememory effects of the three types of
tubing used to transfer streams containing sul-
fur compounds.The Sulfinert
®
treated tubing
shows less retention of sulfur compounds by
several orders of magnitude, indicating very
high inertness.
Valueofan InertPathway
The value of surface treated sampling and
transfer equipment is twofold: more accurate
results and faster cycle times. Improved accura-
cy and reliability of data for sulfur, achieved using
Sulfinert
®
treated transfer and sampling equip-
ment, mean downstream processes can bemore
precisely controlled, with associated cost sav-
ings. Shorter cycles translate directly intomore
samples collected and analyzed in a given period
of time.Typical savings can be calculated by look-
ing at the average per-hour cost of operating a
process that relies on accurate quantification of
sulfur compounds.
1
Examplemonetary values are
reported on the front of this note.
InSummary
We obtained accurate data, with no delay
between samples, by using Sulfinert
®
treated
electropolished tubing in the sampling-storage-
transport system. In contrast, we obtained sig-
nificantly less accurate data, evenwith delays of
more than two hours between samples, by using
untreated tubing. Analysts chargedwithmoni-
toring sulfur levels in process streams can sig-
nificantly improve profitability by using
Sulfinert
®
treated system components and
Sulfinert
®
treated electropolished tubing
transport lines.
Reference
1.
Application of TrueTube
™
in Analytical Measurement
Cardinal UHPAugust 2004
Available at
or by contacting us at
800-356-1688, ext. 4. Request lit. cat.# 59088.
Acknowledgement
The authors thank the staff of the Shell Research and
Technology Centre, Amsterdam, for data used in evaluating
sulfur gas uptake andmemory effects of tubing substrates.
Sulfinert
®
-TreatedElectropolishedTubing
**0.035" wall thickness
1
/
8
" OD: 5 ft. to 100 ft. in one continuous coil;
1
/
4
" OD: 5 ft. to
300 ft. in one continuous coil. Longer lengthswill bemore than
one coil.
Note: (required length inmeters) x (3.2808)= length in feet.
Price-per-foot
ID
OD
cat.#
5-24 ft.
25-99 ft.
100-299 ft.
>300 ft.
0.085"
1
/
8
"
22538
$25/ft.
$20/ft.
$16.80/ft.
$14/ft.
0.180"
1
/
4
"
22539
$25/ft.
$20/ft.
$16.80/ft.
$14/ft.
CoiledSulfinert
®
-TreatedSeamless316GradeStainlessSteelTubing
please
note
An extra charge is applied
for cutting Sulfinert
®
tubing,
calculated from the total
number of pieces produced
for each line item:
Price-per-foot
ID
OD
cat.#
5-24 ft.
25-199 ft.
200-399 ft.
>400 ft.
0.055" (1.40mm)
1
/
8
" (3.18mm)**
22508
$18.75/ft.
$15/ft.
$12.50/ft.
$10/ft.
0.180" (4.57mm)
1
/
4
" (6.35mm)**
22509
$18.75/ft.
$15/ft.
$12.50/ft.
$10/ft.
Sulfinert
®
-TreatedSampleCylinders
D.O.T. rated to 1800psi at room temperature.
Size
qty.
cat.#
price
75cc
ea.
24130
$200
150cc
ea.
24131
$225
300cc
ea.
24132
$230
500cc
ea.
24133
$255
1000cc
ea.
24134
$425
2250cc
ea.
21394
$820
# of
Added
Pieces
Charge
5 to 15
16 to 30
31 to 75
76 to 99
100 to 200
Restek offersmany
Sulfinert®-treat-
ed fittings,
valves, sample
loops.
Formore information
and ordering, call us
or visit us online.
110Benner Circle • Bellefonte, PA 16823
800-356-1688•814-353-1300• fax: 814-353-1309
Restek
Performance
Coatings
Sulfinert
®
Treated
Electropolished
Tubing
Lit. Cat.#59082
© 2005 Restek Corporation.
free
literature
Learnmore about our
precisely applied, highly
durable surface treatments:
request our brochure lit.
cat.# 59493.
Restek trademarks:
Sulfinert, the RPC logo.
Other trademarks:
TrueTube (O'Brien Corp.)
