Claims
An insulating pipe joint for incorporation into a pipeline, the said joint comprising two mutually insulated steel components with a spark gap located between the outer edge of the first steel component and a disk attached to the second steel component facing an insulating separator, wherein the gap is enclosed in insulating material and the surface of the disk facing the insulating separator is irregular, preferably in the form of V-shaped hump or projections according to Patent Application P-361606, characterized in that an insulating and sealing sleeve (2) is positioned between two tubular steel components (D an d (3), wherein the entire inner surface of the sleeve (2) and the outer surface of the contracted end portion of one of the tubular components (3) is furnished with circumferential notches the height of which is equal to one half of the difference between outer and inner diameters of these components. |
ELECTRICALLY INSULATING PIPE JOINT
The subject of the invention is an insulating pipe joint designed for incorporation into a pipeline, said pipe joint having a spark gap.
Insulating pipe joints for incorporation into pipelines, with spark gaps used to discharge electric charges, especially those caused by atmospheric electrical discharge, are known in the art.
High voltage generated during an atmospheric electrical discharge causes an uncontrolled discharge of electrical potential in the pipeline. In order to prevent such undesired incidents, a controlled spark discharge is induced at a precisely defined point.
A tubular insulating element for incorporating into a pipeline with two segments of a pipe provided with a spark gap in the form of an annular flange positioned over the collar of an insulating element in such manner that it projects freely into a cavity that separates two collars and a bell enclosing these collars is known form Austrian Patent Specification No. 389367.
Also known from Polish Patent Specification No. 181068 is an insulating pipeline joint in the form of a cylindrical body with two insulating separators inside, wherein two flanges are permanently attached to end faces of pipes and one of said flanges has in its perimeter zone a spline for receiving a permanently attached shaped lock and the other of the flanges has on its face an annular spline the cross section outline of which has a close-to-triangular shape. The flanges are positioned one opposite the other so that an air gap exists between the inner
surface of one flange and the edge of the annular spline. In the case of an atmospheric electrical discharge to a relay station and consequent current surge in the pipes, due to the presence of sharp edge on the annular spline, a high-voltage spark-over occurs between the flanges, protecting thereby the insulating separators against charring.
The Polish Patent Application No. P-361606 discloses an insulating pipe joint for incorporation into a pipeline, said joint comprising two mutually insulated steel components with a spark gap between outer edge of one steel component and a disk attached to the other steel component on its side facing the insulating separator, wherein said spark gap is enclosed in insulating material. The surface of the disk facing the insulating separator is irregular, preferably in the form of a V- shaped hump or protrusions.
Essential feature of the present invention is an insulating element for the two steel components, said insulating element comprising an insulating and sealing sleeve, the entire surface of which has mutually parallel circumferential saw-tooth notches, the arrangement of which is described by the following equations:
(dcz-dcw) x 1/2= X 0
(dtz-dtw) x 1/2=x t
Xc=Xt where: dcz - outer diameter of steel component dtw - inner diameter of steel component dtz - outer diameter of insulating and sealing sleeve dtw - inner diameter of insulating and sealing sleeve
x c - height of notch in steel component
X t - height of notch in insulating and sealing sleeve
The application of the insulating and sealing sleeve provides an equivalent contact surface area of steel pipes forming the insulating pipe joint, due to which the pipe joint strength is increased, enabling the disclosed joint to be used in high-pressure pipelines.
In the case of an atmospheric electrical discharge to a relay station and formation of a high difference of potentials along the steel components of the pipeline, a spark-over occurs between the disk and the first steel component. This protects the insulating separator against breakdown and consequently protects against shorting two steel components. The spark gap is set so that the surface area between steel component and the disk ensures maximum heat to be carried away during electrical surge. The installation of the disk on the external face of the pipe joint enables, in the case of damage caused by electrical surge, its reconditioning or replacement without having to disassemble the pipe joint itself and to stop the operation of the pipeline.
One embodiment of the invention is shown in drawings, where Fig. 1 presents a schematic arrangement of two steel pipes which together with the insulating and sealing sleeve form an insulating pipe joint, the joint being prior to assembly, Fig. 2 presents a schematic structure of the insulating pipe joint having the form of a union with the insulating and sealing sleeve during the assembly of the joint to permanently form such union, and Fig. 3 depicts half-section of the complete joint with structural details of saw-tooth notches.
The insulating pipe joint according to this invention consists of two tubular steel components 1, 3 and of an insulating and sealing sleeve 2 positioned
between the said steel components. Spark gap 4 is located beyond the outer edge of the first steel component 1 and has the form of a gap between the edge of the steel component 1 and disk 5 attached to the second steel component 3 facing the insulating and sealing sleeve 2. The height of notches in the steel component 3 and in the insulating and sealing sleeve 2 is set to satisfy the following relationship: one half of the difference between outer and inner diameter of these components is equal to the height of the notches.