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2
Extensions (E)
An Extension is used where it is not necessary to have the alloy pipe extend through the cool part of the furnace. By using a steel
extension (or balance pipe), the total cost of the protection tube can be reduced. The extension also keeps the connection head out of
any corrosive gases and away from excessive heat. Extensions can be added to metal or ceramic protection tubes.
To add an extension to a metal or ceramic assembly, add (
E
) and the number of inches to the end of the part number.
Examples:
Metal: 8K4-722-18-E-12-SH (18”, #7 alloy metal tube assembly, and a 12” extension.)
Ceramic: 8K4-P11F-18-E-12-SH (18”, Mullite tube assembly, and a 12” extension.)
1
Adjustable Flange (AF)
An adjustable flange is used to adjust the protection tube’s depth of insertion. In most cases the tube should extend into fluids at
least six times the out side diameter of the tube. If the tube is going into a gas, it should extend a minimum of eight times the outside
diameter of the tube. The adjustable flange can also be used to extend the connection head away from excessive heat or corrosive
gases. A flange will not give a gas tight seal. If a gas tight seal is required, a Threaded Fitting (
TF
) or a Welded fitting
(W
) should be
used. On Ceramic tubes it is necessary to have a metal sleeve to mount the flange. This will prevent the tube from breaking when the
set screw is tightened. This sleeve is normally made from high temperature #9 alloy (600).
To add an adjustable flange to a metal or ceramic assembly, add (
AF
) to the end of the part number.
Examples:
Metal: 8K4-722-18-SH-AF (18”, #7 alloy metal tube assembly, and an adjustable flange.)
Ceramic: 8K4-P11N9-6-18-SH-AF (18”, Mullite tube assembly, 6” #9 alloy sleeve, and an adjustable flange.)
Metal Tube
Ceramic Tube
Ceramic Tube
Metal Tube
3
Threaded Fitting (TF)
A Threaded Fitting has three threads; it is screwed on to the open end of a protection tube and then screwed into the furnace to
give a gas tight seal. The third thread permits the tube to be extended beyond the fitting for mounting a terminal head. The replace-
ment of a protection tube with a threaded fitting is less expensive than one with a welded bushing since only the tube needs to be
changed. The standard outside thread size is 1 1/4” NPT. 1/2” NPT threaded fittings are standard outside threads on 1/4” and 1/8”
pipe sizes. Other sizes can be ordered by specifying the size in 1/16ths of and inch.
Example:
A 1 1/2” x 1/2” 1/2” NPT thread fitting would be a
TF2408
. See under “Accessories” for more details.
To add a threaded fitting to a metal assembly, add (
TF
) to the part number.
Example:
Metal: 8K4-722-18-TF-6-SH (18”, #7 alloy metal tube assembly, Threaded Fitting and a 6” extension.)
Metal Tube
Straight Assemblies - Mounting Attachments
Page 30
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