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As concerns grow over mercury in the environment,
new regulations have been developed to measure,
and eventually reduce, mercury emissions from
coal-fired electric utilities. For example, the US
EPA will require all electric utilities to measure
mercury emissions starting on January 1, 2009.
The most popular methods of sampling will be
based on continuous mercury monitoring systems
(CMMS) and sorbent tube samplers. To ensure
quantitative storage and transfer, and accurate
analysis, of the low levels of mercury in streams
sampled from flue stacks, these sampling systems
must be inert.
Siltek
®
surface treatment has been used in a wide
variety of applications in which an inert surface is
of paramount importance. To measure the impact
of Siltek
®
treatment on adsorption of mercury dur-
ing storage, we compared the performances of 304
grade stainless steel gas sampling cylinders
(Swagelok
®
, Solon OH) with and without Siltek
®
treatment.
We filled each cylinder with 8µg/m
3
of elemental
mercury (approximately 1 part per billion) (Spectra
Gases, Alpha NJ) and assessed the mercury con-
centration in each cylinder over time to determine
changes in mercury concentration. Detection was
achieved by direct interface gas sampling to an
atomic adsorption detector. Sample pathway regu-
lator and tubing were Siltek
®
treated to ensure
accurate transfer.
The data in Figure 1 demonstrate that Siltek
®
treat-
ment provides a stable surface for elemental mer-
cury, and untreated stainless steel does not. Based
on these results, we conclude that Siltek
®
surface
treatment for steel or stainless steel components
and tubing in CMMS and sorbent tube mercury
sampling systems will improve analytical reliability.
For more information about Siltek
®
surface treat-
ment, visit us at:
www.restekcoatings.com•
16
•
2007 vol. 3
Restek Performance Coatings
Prevent Mercury Loss During Transport and Storage
Use Siltek
®
Surface Treatment on Steel Components
By Gary Barone, Restek Performance Coatings Division
• Rugged—withstands temperatures up to 400°C.
• Meets system inertness requirements.
• Eliminates costly retests.
thank
you
Ted Neeme and Steve Mandel from Spectra Gases for their contributions to this work.
Figure 1
Siltek
®
treated gas sampling cylinders show very good
inertness toward mercury.
Siltek
®
/Sulfinert
®
Treated Coiled Electropolished 316L Grade
Stainless Steel Tubing
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
lengths will be more than one coil. Note: required length in meters x 3.2808 = length in feet.
*0.020" wall thickness **0.035" wall thickness ***0.049" wall thickness
Price-per-foot
ID
OD
cat.# 5-24 ft.
25-99 ft.
100-299 ft.
>300 ft.
0.085" (2.16mm)
1
/
8
" (3.18mm)* 22538
$25.90/ft.
$20.70/ft.
$17.40/ft.
$14.50/ft.
0.180" (4.57mm)
1
/
4
" (6.35mm)** 22539
$25.90/ft.
$20.70/ft.
$17.40/ft.
$14.50/ft.
Siltek
®
/Sulfinert
®
Treated Coiled 316L Grade Stainless Steel Tubing
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
$19.40/ft.
$15.50/ft.
$12.90/ft.
$10.40/ft.
0.180" (4.57mm)
1
/
4
" (6.35mm)** 22509
$19.40/ft.
$15.50/ft.
$12.90/ft.
$10.40/ft.
0.277" (7.04mm)
3
/
8
" (9.52mm)*** 22914
$18.75/ft.
$15/ft.
$12.50/ft.
$10/ft.
Siltek
®
/Sulfinert
®
Treated Straight Seamless 316L Grade
Stainless Steel Tubing
6 foot Length
ID
OD
qty.
cat.#
price
0.055" (1.40mm)
1
/
8
" (3.18mm)**
ea.
22901
$233.40
0.180" (4.57mm)
1
/
4
" (6.35mm)**
ea.
22902
$167.30
0.277" (7.04mm)
3
/
8
" (9.52mm)***
ea.
22903
$192
Sulfinert
®
Treated Swagelok
®
Sample Cylinders
Size
qty.
cat.#
price
75cc
ea.
24130
$205
150cc
ea.
24131
$232
300cc
ea.
24132
$238
500cc
ea.
24133
$265
1000cc
ea.
24134
$440
2250cc
ea.
21394
$870
Sulfinert
®
Treated Alta-Robbins Sample Cylinder Valves
Specify dip tube length or % outage when ordering (maximum length = 5.25"/ 13.3cm)
Description
qty.
cat.#
price
1
/
4
" NPT Exit
ea.
21400
$180
1
/
4
" Compression Exit
ea.
21401
$180
1
/
4
" NPT with Dip Tube*
ea.
21402
$260
1
/
4
" NPT with 2850psi Rupture Disc
ea.
21403
$365
1
/
4
" NPT Male Inlet x
1
/
4
" Female Outlet with 2850psi Rupture Disc
ea.
21404
$365
United States patent 6,444,326 (Siltek
®
/Sulfinert
®
)
Untreated cylinders (n=2)
Siltek
®
cylinders (n=2)