001 Front Cover

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Straight Thermocouple Assemblies - Mountings and Attachments

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Adjustable Flanges A adjustable flange is used to adjust the protection tubes depth of insertion. ln most cases the tube should extend into fluids at least six times the outside diameter of the tube. lf the tube is going into a gas, it should extend a minimum of eight times the outside diameter of the tube. The adjustable llange can also be used to extend the connection head away from excessive heat or corrosive gases. A flange will not give a gas tiglrt seal. f a gas ilght seal is required, a threaded (IF) or welded fitting W) should be used. On ceramic tubes it is necessary to have a metal sleeve to mount the tlange. 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 a adjustable flange to a mekl or ceramic assembly, add AF to the end of the paft number.

Examples:

MeIal 8K4-722-1S-AF (18" #7 alloy metal tube assembly, and a adjustable flange) Ceramic- 8K4-P11N9A6-18-AF (18" mullite tube assembly, and a adjustable flange)

Extensions A extension may be used where it is not necessary to have the alloy pipe exend through the cool part of the furnace. By using a steel extension, 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 a extension to a metal or ceramic assembly, add E and the number of inches of ertension to the end of the parl number

Examfles:

Metal- 8K4-722-18-E-1 2" extension) Ceramic- 8K4-P11F-18-E-12 (18" mullite tube assembly, and a 12" extension) 2 (1 B" #7 alloy metal tube assembly, and a 1

Tlrreaded Fittings A threaded fitting 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 replacement of a protection tube with a threaded fitting is less epensive than one with a welded bushing since only the tube has to be changed. The standard outside thread size of a threaded fittingisl l/4"NPT 1/2"NPTthreadedfittingsarestandardoutsidethreadsonl/4"andl/8"pipesizes. Othersizescanbeorderedby specifying the size in 1/16ths of an inch.

Example: A 1 112" x1/2" x112" threaded fitting would be a F2408.

To add a threaded fifting to a medl assembly, add TF to the paft number.

Examfle:

Metal- 8K4-722-18-TF-O (1 8" #7 alloy metal tube assembly, threaded fitting, and a 6" nipple)

Welded Fittings A welded fitting is welded directly on the the protection tube. The tube than can be screwed into the furnace to give a gas tight seal. Protection tubes with a welded fitting are more epensive than threaded fittings since the alloy extends outside the furnace. Also the fitting must be replaced with the tube. The standard outside thread size on a welded fitting is 1 114" NPT 1/2" NPT outside thread welded fittings are standard on 1/4" and 1/8" pipe sizes. Other sizes can be ordered by specifying the size in 1/16ths of an inch. ',lexample: A1 112" x112" xl12" welded fitting would be a W2408. To add a velded fitting to a metal assembly, add W follofied by the immersion length ( -*) to the paft number. Example: Metal- 8K4-734XH€6-W-24 (36" #7 alloy metal tube assembly, 1 1/4" welded fitting, 24" immersion length measured from the tip of the tube to the bottom of the fitting) The immersion length is shown as (U) on ligure 4. ln most cases the tube should extend into fluids at least six times the outside diameter of the tube. lf the tube is going into a gas, it should extend a minimum of eight times the outside diameter of the tube. Page 30