Phone: 800-356-1688 or 814-353-1300
13
Oven
Some canister cleaning systems are incorporatedwithin an oven. The supply
line for the humidified air stream and the line to the vacuum system are
plumbed directly into the oven. In this arrangement the entire canister,
including the valve,will be heated, and thiswill help remove contaminants if
both the valve and the canister aredirty.Typically,whenusingheat, it is help-
ful to create steam from thehumidified air stream.Anoven temperatureof at
least 120°C is required, but higher temperatures often are used. Remember
that heat can shorten the lifetime of theNupro valve on a SUMMA® canister
(see step3 inCleaningMethod, below).
Space is a concern with oven systems. Most commercial ovens are not very
largeand this restricts thenumberof canisters that canbecleanedatone time.
However, clean-up times are shorter with heat than without heat, so more
cleaning cycles canbe completed in aweek.
Heat Bands
Abandheaterplacedaround theequatorof thecanister typicallywill becapa-
ble of heating the canister to approximately 130°C. There is a heat gradient,
and the valve might only receive radiant heat (approximately 70-100°C). In
most sampling situations, however, this lower temperature should be suffi-
cient for effectively removing contaminants from the valve.
InsulatedHeat Jackets
Insulated heat jackets can be obtained to surround and heat each canister.
These jackets typicallyhave a siliconeorTeflon®-coated fiberglass fabric exte-
rior and a fiberglass insulation interior. Some operate at a fixed temperature;
others can provide variable temperature, up to 400-500ºF. Restek’s heating
jacket, described at right on this page, offers significant advantages overmost
other commercial designs,whichdonot encompass the valve area.
InfraredHeat
An infrared heating system includes an infrared heat source and a reflective
panel similar to thecylinderdrying rackonagascylinder system.The infrared
source and the reflective panel are placed on opposing sides of the canisters.
Infrared rays from the source heat the canisters; rays that pass the canisters
strike the reflective panel andheat the canisters from the opposing side.
TheCleaningSystem
Thecleaning systemmustprovideahumidifiedair streamand includeagood
vacuum source, acold trap tocollect impuritiesduringcleaning, andaccurate
gauges to read vacuum and pressure. A heat source is optional, but is highly
recommended in some circumstances, as discussed above. The system canbe
designed toclean4 to24 six-liter canisters.Figure8 (page14) shows anexam-
ple of a “homemade” system designed to clean 24 six-liter canisters. This
designdoesnot employheat,but aheater easily canbe added (seeHeat orNo
Heat, page 12). It provides a humidified air stream to all canisters and the
roughing pump on the bottom shelf is the vacuum source. This system is
computer operated tominimize labor, but this is not necessary.
CleaningMethod
1. Connect all canisters to the cleaning system, then release anypressure
within anyof the canisters. Put the systemunder vacuum, to evacuate the
canisters.USEPAMethodTO-14A/15 recommends evacuating the sys-
tem to50mTorr for 1hour, but a reducedpressure of 23-25"Hg is suffi-
cient for general cleaning.
2. After the canisters have beenunder vacuum for approximately 1hour,
pressurize the canisterswithhumidified air or nitrogen*. Pressurization
will dilute the impurities and themoist airwill hydrolyze them.
Pressurize canisters to5psig if theywill beheatedor to30psig if they
will not beheated. Proceed to step3when the systemhas equilibrated at
the designatedpressure.
Theultimate in controlledheating,
for reliably cleaningyour air canisters!
Description
qty.
cat.#
Air Canister Heating Jacket (110 volt)
ea.
24123
AirCanisterHeatingJacket
• Closely simulates oven environment—heats
entire canister.
• Two temperature settings, 75°C and150°C.
• Prevents sample condensation, for accurate sub-
sampling.
• Easily fits canister up to6 liters.
• Lightweight; comfortable to the touchwhen
heated.
• Connect up to fiveCanisterHeating Jackets to
one 15 amp circuit.
The Restek Canister Heating Jacket will help you
cleanyour canisters faster andmoreefficiently.The
novel design ensures the entire canister, including
the valve, is heated during the cleaning cycle, to
remove contaminants most effectively. It also can
be used to keep the sample heated during aliquot
removal, which helps prevent condensation and
assure accurate data for largermolecules. The two
heat settings let youmatch the temperature to the
volatility of your sample components. If you try
one in your system,we think you’ll wantmore.
*
please
note
If you are cleaning SilcoCan
TM
canisters, andwill be using heat,
use humidified nitrogen, not air.
