Pipes and tubular conduits – Distinct layers – With intermediate insulation layer
Patent
1997-03-04
1998-05-26
Lewis, Paul C.
Pipes and tubular conduits
Distinct layers
With intermediate insulation layer
138155, F16L 914
Patent
active
057552657
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a discharge pipe for discharging hot substances, which discharge pipe consists of an outer pipe, and an inner pipe placed coaxially inside the outer pipe, the inner pipe and the outer pipe enclosing a space, which space contains two concentric layers of different material, the first layer surrounding the outside of the inner pipe and the second layer surrounding the first layer and which second layer is surrounded on the outside by the outer pipe.
From the U.S. Pat. No. 1,709,844 a discharge pipe is known, which pipe is covered by insulating means so the pipe can be laid in the ground and discharge hot and cold liquids or gases such as hot steam or liquids and cool brine, ammonia or other liquids which are at a temperature lower than that of the surrounding earth. The insulating means consists of a first layer which can be any approved insulating material, such as air-cell, wool felt, magnesia or cork chips. The second layer consists of a fluent self-hardening material such as asphalt. This known discharge pipe is especially designed to be used with substances with a temperature lower than about 100.degree. C. and can not be used to carry gases and liquids with a temperature above 100.degree. C. such as flue gasses with a temperature over 1000.degree. C. In that case a very thick first layer would be needed to prevent the second layer of asphalt to become too hot. The first layer is of thermally insulating material and is needed to prevent that the asphalt layer will be heated above the melting temperature of asphalt, which is considerably lower than 100.degree. C. However, the thickness of the heat-insulating material of the first layer depends on what temperature the substances can reach and on the maximum permissible outer wall temperature of the first layer. It has been found that such discharge pipes must be surrounded by a very thick first layer of insulating material, if materials flow through the pipes with a temperature far above 100.degree. C., in order that the outside temperature of the first layer will not reach the melting temperature of asphalt. This makes such pipes very expensive, and they have an undesirably large external diameter.
If such discharge pipes are used for chimneys, the discharge pipes must meet all kinds of regulations. For example, in some areas there are standards in which the temperature at the outside of a chimney flue must not rise more than 75.degree. C. if hot combustion gases at a temperature of about 1000.degree. C. are discharged For a certain short period through the discharge pipe or chimney, or if hot combustion gases at a temperature of about 600.degree. C. are discharged for a period of three hours. If insulating materials such as ceramic wool are used, the external dimensions of the discharge pipe or chimney then become too large. However, if insulating materials such as concrete, which could have much better heat-insulating properties, are used, with the result that the external dimensions of a discharge pipe can be reduced to within desired dimensions, yet other problems then emerge. The inside of the discharge pipe ought to be gastight and must therefore be, for example, a smooth, thin metal pipe. However, such a metal inner pipe has a different coefficient of expansion from the layer of insulating concrete, with the result that the inner pipe cannot expand and can consequently buckle, bend and even crack.
The object of the invention is a discharge pipe for hot substances such as combustion gases, in which the outer wall of the discharge pipe will not rise above a desired temperature which is in general lower than 100.degree. C. if very hot substances are conveyed through the discharge pipe, and of which the external dimension of the pipe is much smaller than usually until now. Another object of the invent on is a discharge pipe with an inner pipe which is surrounded by a insulating layer which is made of a material with very high thermal insulating properties of which the coefficient of expansion is smaller than the coefficient of
REFERENCES:
patent: 1709844 (1929-04-01), Durant
patent: 4130140 (1978-12-01), Cerny et al.
patent: 5186217 (1993-02-01), Kallinich et al.
Lewis Paul C.
Stoutenbourg Beheer B.V.
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