Tube Skin Thermocouple How to measure the correct Tube Skin temperature in a Heater

Ing. Nils Bjørdal AS 0047 90962123 [email protected] www.bjoerdal.no

The Fan Tip thermocouple •  Drawing of the hot junction (Measuring Point)

Fan Tip Specifications •  •  •  • 

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 •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  •  • 

•  •  • 

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 methode Metal spraying At Statoil Mongstad a method of metal spraying was developed in cooperation with SINTEF Resurtch Institute around 1986

Welding •  •  •  •  •  • 

Time consuming Tube has to be preheated The weld must be annealed Risk for cracks in the tube X-Ray is sometimes a demanded Pressure testing

Metal Spraying •  •  •  •  •  • 

Very time efficient installation No damage or physical change in tube material Tube temperature only 100 ºC during installation No heat treatment No X-ray needed No pressure testing

Procedure for metal spraying •  •  •  •  • 

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 by blasting

Fixing the Fan Tip to the tube

First layer of metal Bond layer

Second layer of metal Thermal insulation layer

Outside layer of Aluminium Oxide Corrosion protective layer

Arc spray machine

References •  •  •  •  •  •  •  • 

Statoil Mongstad Statoil Kalenborg Preem Raff Gothenburg Preem Raff Lysekil ExXon Tønsberg Borealis Stenungsund Nynas Oil Refinery Nynashamn Neste Oil Rotterdam Neste Oil Singapore