Fluid handling – Processes – Affecting flow by the addition of material or energy
Patent
1994-12-27
1997-02-25
Chambers, A. Michael
Fluid handling
Processes
Affecting flow by the addition of material or energy
137896, 251148, F17D 116
Patent
active
056051743
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a device for the conveyance of thick substances rich in solid material with a conveyor pipe filled with the thick substances under pressure, and at least one injection place opening into the conveyor pipe for the introducing of a lubricant into the region between the pipe wall and the surface of a thick substance plug flow that is formed in the pipe.
BACKGROUND OF THE INVENTION
Pipelines are often used for the conveyance of solid/liquid mixtures having a high solid substance constituent, such as, for example settled sludge or mud. Such thick substances have a great internal friction, so that in their pressing through a conveyor pipe no speed gradient develops transversely to the direction of spreading. A relative movement takes place essentially only between the surface of the thick substance strand and the pipe wall, the sliding friction being reduced by the injected lubricant. In the conveyance of partially dehydrated settled sludge, it is already a known
practice (DE-OS 36 05 723), for the reduction of the wall friction to inject at the beginning of the pipe line heating oil, water or an aqueous solution of a high-polymer lubricant between the settled sludge and the wall of the conveyance line. This occurs mostly continuously and proportionally to the conveyance flow in dosed amount with the consequence that between the pipe inner wall and the thick substance strand a boundary layer forms, by which the conveyance pressure can be reduced by 80% and more. However, especially in the case of relatively long conveyance stretches of several hundred meters there are still yielded very high conveyance pressures, since the sliding layer along the conveyance stretch gradually disappears.
SUMMARY OF THE INVENTION
This invention is the problem of improving the known conveyance device of the type mentioned above that along the pipe there is maintained a uniform lubricant layer with the least possible use of lubricant.
Underlying the invention is the insight that a low pressure decline in the conveyance line is achievable only if the thick substance plug flow is transported largely free of wall contact through the entire conveyance pipe. This is the case when a sufficiently thick lubricant layer can be maintained over the entire conveyance pipe. In order to achieve this, it is proposed according to the invention that the conveyance pipe have an annular cross section construction located downstream at a distance from the injection point. This cross section constriction has the function of a boundary layer barrier which provides that the lubricant is not dragged unnecessarily by the thick substance plug flow. Furthermore, at the cross section constriction there occurs a limitation of the thick substance plug flow to a correspondingly small diameter. Further, there is achieved thereby a centering of the thick substance plug flow inside the conveyance pipe, which leads to the result that the lubricant layer remains largely equally thick over the circumference. Advantageously the inside diameter of the conveyance pipe in the region of the cross section constriction is i mm preferably 2 to 3 mm smaller than outside this region.
A preferred embodiment of the invention provides that the cross section constriction is formed by a bulge or collar-type annular raised part, on the inside of the conveyance pipe, which can be generated, for example, by an annular weld bead protruding into the pipe interior or by a tapping or boring of the pipe. Optionally it is also possible to equip the most welded-on flange rings of the pipe line with a diameter reduced in comparison to the pipe interior diameter. This can be the case on one or on both flange halves. Further, the cross section constriction can be formed by a collar ring protruding into the pipe interior, preferably clamped between two pipe flanges.
In horizontal or diagonal conveyance pipes, because of the mostly higher specific gravity of the conveyance material in comparison to the lubricant, there occurs a displacement of
REFERENCES:
patent: 2821205 (1958-01-01), Chilton et al.
patent: 3099993 (1963-08-01), Smith
patent: 3414004 (1968-12-01), Bankston
patent: 3892252 (1975-07-01), Poettmann
patent: 4510958 (1985-04-01), Coursen
patent: 5361797 (1994-11-01), Crow et al.
Rockstroh Axel
Schlecht Karl
Schuster Ulrich
Chambers A. Michael
Putzmeister-Werk Maschinenfabrik GmbH
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