Tube Skin Thermocouple
How to measure the correct
Tube skin temperature in a Heater
The Fan Tip thermocouple
• Drawing of the junction
Fan Tip Specifications
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Calibration: Type K or N
Sheath Material: Hastelloy X
Diameter: 6.0 or 8.0 mm
Accuracy: +4°C
The most common used thermocouples
• Fan Tip
• Pad Style
• Knife-edge
Comperison of accuracy
Surface measurements are always trublesom and usually
inaccurate. There are many methodes used for measuring tube surface
temperatures. This is usually a difficult measurement becouse of the temperature of
the air or flame around the tube is higher than th tube itself, leading to a positive error
The ” Fan” Aproache is both more accurate and has a faster response then other
designs. Using Hastelloy X material this also give long life
A test has been carried out compering the thre different types
In this test the real tube temperature was 500ºC and the ambient gas temperature
was 800ºC resulting in the following data:
Syle
Indicated temperatur ºC
Error ºC
%
Knife-edge
521
21
4.35
Pad Style
520.9
20.9
4.0
Fan Tip
504.5
4.5
0.7
Hastelloy X material
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PRINCIPAL FEATURES
Strength and Oxidation Resistance
HASTELLOY® X alloy is a nickel- chromium-iron-molybdenum alloy that possesses an exceptional combination of oxidation resistance, fabricability
and high-temperature strength. It has also been found to be exceptionally resistant to stress-corrosion cracking in petrochemical applications. X
alloy exhibits good ductility after prolonged exposure at temperatures of 1200, 1400, 1600F (650, 760 and 870C) for 16,000 hours.
Haynes International Inc X alloy
Easily Fabricated
HASTELLOY X alloy has excellent forming and welding characteristics. It can be forged and, because of its good ductility, can be cold worked. X
alloy can be welded by both manual and automatic methods including shielded metal arc (covered electrodes), gas tungsten arc (GTAW) and gas
metal arc (GMAW). The alloy can also be resistance welded.
Haynes International Inc X alloy
ASME Boiler and Pressure Vessel Code
HASTELLOY X alloy plate, sheet, strip, bar, tubing and pipe are covered by ASME specifications SB-435, SB-572, SB-619, SB-622 and SB-626
under UNS Number N06002.
Haynes International Inc X alloy
Heat-Treatment
Wrought forms of HASTELLOY X alloy are furnished in the solution heat-treated condition unless otherwise specified. X alloy is solution heattreated at 2150F (1177C) and rapid cooled. Bright annealed products are cooled in hydrogen.
Haynes International Inc X alloy
Available in Convenient Forms
HASTELLOY X alloy is available in the form of plate, sheet, strip, billet, bar, wire, covered electrodes, pipe and tubing.
Haynes International Inc X alloy
Useful for Aircraft, Furnace and Chemical Process Components
X alloy has wide use in gas turbine engines for combustion zone components such as transition ducts, combustor cans, spray bars and flame
holders as well as in afterburners, tailpipes and cabin heaters. It is recommended for use in industrial furnace applications because it has unusual
resistant to oxidizing, reducing and neutral atmospheres. Furnace rolls of this alloy were still in good condition after operating for 8,700 hours at
2150F (1177C). HASTELLOY X alloy is also used in the chemical process industry for retorts, muffles, catalyst support grids, furnace baffles,
tubing for pyrolysis operations and flash drier components.
Haynes International Inc X alloy
Specifications
For information on specifications to which this alloy can be ordered, please contact one of the locations shown on the Haynes Home Page and ask
for bulletin H-1034 Applicable Specifications.
Installation of the Fan Tip
• This drawing shows a typical
general installation with
expasion coil
ARI Installation drawing
Fan Tip installation ExXon
Installation Statoil
ATEX Installation
Mounting methodes
• Welding
Welding has been the
traditional method for this
application
• Metal spraying
At Statoil Mongstad a method
of metal spraying was
developed around 1986
Welding
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Time consuming
Tube has to be preheated
The weld must be annealed
Risk for cracks in the tube
X-Ray is sometimes a demanded
If performed properly it is a god solution
Metal Spraying
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Very time efficient installation
No damage or physical change in tube material
Tube temperature only 100 ºC during installation
No heat treatment
Procedure for metal spraying
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Cleaning the tube by blasting
Fixing the Fan Tip to the tube
First layer of metal
Second layer of metal
Outside layer of Alumina Oxide
Cleaning the tube
Fixing the Fan Tip to the tube
First layer of metal
Second layer of metal
Outside layer of Aluminium Oxide
Arc spray machine
References in Nordic Countries
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Statoil Mongstad
Statoil Kalenborg
Preem Raff Gothenburg
Preem Raff Lysekil
ExXon Tønsberg
Borealis Stenungsund
metal spray
metal spray
metal spray