QUALITY AND CERTIFICATION
USING CERAMIC TUBES IN A HORIZONTAL TUBULAR
OVEN UP TO 1600°C
Yu. V. Shevelev
and Yu. O. Malyshev
Translated from Novye Ogneupory, No. 5, pp. 48 – 50, May, 2008.
Original article submitted March 30, 2007.
Ceramic tubes from various sources have been tested in a high-temperature horizontal tubular furnace
developed at this company, which is used for checking thermocouples of TPR (V) type. The tubes should not
deform at 1600°C. It is found that ceramic tubes can be used in a horizontal furnace up to 1600°C if they are of
At the current level of industrial development, tempe-
rature measurements constitute about 40% of the total
volume of all measurements. Consequently, a wide range of
means of measuring temperature is in use, which requires
periodic checking. Resistance thermometers and thermo-
electric detectors working up to 1200°C provide a wide
range of test facilities, while to check thermocouples of type
TPR (V) there is no metrological equipment in regular
production in this country, in particular ones in which one
can realize the method of comparison in accordance with
GOST 8.338 – 2002. The main problem is difficulty in
making the heat, which must work reliably in air at
temperatures above 1600°C, together with the heat-resisting
ceramic tube, which must have adequate mechanical strength
at that temperature, and also the insulating material, which
should have low thermal conductivity in the working
temperature range. Leaving aside the heater and the thermal
insulation, in this paper we consider the choice and use of
ceramic tubes up to 1600°C in a horizontal furnace (Fig. 1).
A ceramic tube is needed to protect the high-purity metal of
the thermoelectric detector from contamination by
substances arising from the heater and the thermal insulation.
There are advantages in a horizontal oven over a vertical
one: little heat leakage into the working zone because there is
less convection in the air, scope for placing the junctions of
the standard and test thermoelectric devices adjacent to one
another, placing of the thermocouples on different sides of
the oven, and ease of obtaining an isothermal area in the
central zone. A shortcoming of a horizontal system, parti
cularly at 1600°C, lies in the mounting of the ceramic tube as
a rod with gripped ends. The basic specification for the
ceramic tube is thus that it should not deform at 1600°C
under its own weight.
At this company we have developed a horizontal system
with the working temperature range up to 1600°C. Origi-
nally, we used a KVPT ceramic tube of length 600 mm and
diameter 50 mm, wall thickness 5 mm from the Bogdano-
vichi Ogneupory Company. The tube material contained not
less than 97% Al
, and the open porosity was not more
than 5%. The ceramic tube had good mechanical strength at
1600°C and operated for more than 600 h (Fig. 2).
However, the Bogdanovichi Company has ceased to
produce KVPT tubes, so subsequently we attempted to use a
grade MK-821 ceramic tube made by the Polikor Company.
Tube length 620 mm, diameter 50 mm, wall thickness 5 mm.
content was not less than 82%, open porosity not
more than 27%, apparent density 2.4 g/cm
. The tube was
installed in the oven and kept at 1600°C for 4 h. However,
Refractories and Industrial Ceramics Vol. 49, No. 3, 2008
1083-4877/08/4903-0219 © 2008 Springer Science+Business Media, Inc.
Etalon Scientific Company, Russia.
Fig. 1. Horizontal tubular oven: 1) ceramic tube; 2) heater; 3) thermal