Technical Field of the Invention

The present invention relates generally to a flange gasket which is to be disposed between joined pipes for providing sealing between the pipes. More particularly the present invention relates to an insulating flange gasket of joined pipes that provides pressure sealing and electrical isolation between the joined pipes.

Background of the invention

Underground pipelines are subject to corrosion due to presence of moisture and water in the ground. Free Fe and Fe ions in the metallic pipe will react with hydroxide ion OH ^" in the moisture and water to form corrosion. Typically a method called cathodic protection (CP) is used to prevent the corrosion. In operation, the buried pipe is supplied with a negative potential via a transformer or galvanic anodes. The negative potential will repel the hydroxide ions in soil or water away from the pipe and thus keeps the pipe free from corrosion.

To connect the underground pipe that is under cathodic protection to an aboveground pipe which is not under cathodic protection, an insulating flange gasket is used. The gasket is disposed between the flanges of the pipes to provide pressure sealing and electrical isolation. The insulating flange prevents cathodic protection current from the buried pipe from electrically bridging to the aboveground pipe.

The connection between the gasket and the flange of the pipe may provide gaps or cavities inside the pipes. The gap or cavity may allow residue or contaminant from lose current and may start to corrode, starting at the flange section. A frequent clean up process may need to be carried out in order to remove the build-up which requires the pipeline to be shut down. This situation leads to unproductive pipeline operation. The existing insulating flange gasket may not prevent the contaminant build-up around the gasket inside the pipe since the connection between the flange and the gasket is still exposed. The connection area must be sufficiently insulated to prevent conductive fluid or contaminant to bridge the cathodic protection current to unintended areas. US patent 20090243290 (Pikotek) discloses a metal core backup seal and compression limiter gasket design that addresses flange material integrity under compression and fluid sealing reliability. This US patent does not disclose an insulating flange gasket or method to prevent/limit cathodic protection current leakage as per the present invention. The connection between the flanges may still allow contaminant to build up and result in current leakage.

Other existing methods of preventing cathodic protection current leakage for example are by using monolithic insulating joints (MIJs) and insulation spools, which are more expensive to use compared with insulating flange gaskets.

In light of the above, it is an aim of the present invention to provide an improved insulating flange gasket which can prevent contaminant build-up on the internal gap of the joined flanges and also be cost effective to produce compared to monolithic insulating joints and insulation spools. Furthermore, the installation of this insulating flange gasket does not require the existing pipe and/or flange to be cut or re-welded. Summary of the Invention

The present invention provides an insulating flange gasket for sealing and limiting current leakage of a pipe under cathodic protection (CP). According to the present invention, the gasket is provided with an inner perimeter lip wherein the lip is to be disposed around the inner perimeter of the pipe to prevent contaminant build-up that may occur between the gasket and the flange of the pipe and to provide a sufficient insulating area between the connection. According to the present invention, the gasket comprises a rim having a first planar surface on one side and a second planar surface on the other side wherein the planar surfaces are to be compressed between the flanges of the pipes. The connection between the flanges can be secured by bolts or clamps. The planar surfaces of the gasket have a central aperture. The inner perimeter lip extends outwardly from the central aperture forming a first annular protrusion on one side and a second annular protrusion on the other side. The lip is integrally formed from the planar surfaces wherein the planar surfaces also form shoulders or flanges of the annular protrusions. The annular protrusions form a sleeve which covers any gap or cavities between the flanges and provides a continuous surface. This allows any flowable media or fluid to pass the connection section without any restriction or blockage. The continuous surface also provides no space for the contaminant to accumulate or to be trapped. The annular protrusions include annular surfaces which are substantially in contact with the inner surface or inner perimeter of the pipe. The span of the sleeve or protrusion is suitably extended to provide sufficient insulated area and to prevent current leakage. The suitable length can be determined, for example by:

L = (400 / p) x D The provision of the inner perimeter lip also provides a self-centering adjustment during gasket installation. By having the inner perimeter lip, the planar surfaces no longer need to be adjusted to ensure the planar surfaces or bolt apertures of the planar surfaces align with the surfaces or bolt apertures of the flanges. When the inner perimeter lip is disposed inside the pipe, the annular surfaces of the annular protrusions are radially supported by the inside perimeter of the pipe.

The planar surfaces can be provided with a plurality of apertures to allow the planar surfaces be bolted between the flanges. A pressure sealing is not only provided by the planar surfaces, but also provided by the annular protrusions in which the annular surfaces of the protrusions are substantially in contact with the inner surface or inner perimeter of the pipe. The sleeve not only provides electrical isolation that can prevent cathodic protection current leakage between the joined flanges but also provide an added pressure sealing to the joined flanges.

Brief Description of Drawings

The present invention will now be described by way of example with reference to the accompanying drawings in which:

Fig. la shows a side view of a sample of conventional insulating flange gasket; Fig. lb shows a cross section view of the gasket of Fig. la installed between joined flanges;

Fig. lc shows contaminant build-up on joined flanges of Fig. lb;

Fig. 2a shows a perspective view of an example of the insulating flange gasket according to an embodiment of the present invention;

Fig. 2b shows a side view of the gasket of Fig. 2a disposed between joined flanges; Fig. 2c shows a cross section view of the gasket of Fig. 2a disposed between joined flanges;

Fig. 3a shows a side view of an example of the insulating flange gasket according to another embodiment of the present invention; and

Fig. 3b shows a cross section view of the gasket of Fig. 3a disposed between joined flanges.

Fig. 4 shows a perspective view of the gasket according to the present invention without bolt apertures.

Detailed Description of the Invention

Fig. la shows a side view of a sample of conventional insulating flange gasket (101). As shown in Fig lb, the installation of the gasket (101) between underground pipe (103) which is under cathodic protection and aboveground pipe (106) which is not under cathodic protection, leaves a gap or cavity (102) between cavity (102) arround the connection allows contaminant (109) to build up or conductive fluid to electrically bridge the underground pipe (106) to aboveground pipe (108) in which the current from the underground pipe (106) will enter the aboveground pipe (108). This current leakage will result in current loss from the underground pipe (106) and may corrode the underground pipe (106). A cleaning process needs to be carried out to remove the build-up which requires the pipeline system to be shut down. This situation is unproductive for pipeline operation. Further, since the build-up occurs internally, it is also difficult to know when the build-up has occurred unless severe corrosion on the flanges can be noticed.

A perspective view and side view of an insulating flange gasket (201) according to one embodiment of the present invention is shown in Fig. 2a and Fig. 2b respectively. The gasket (201) has first planar surface (203a) on one side and a second planar surface (203b) on the other side. As shown in Fig. 2a and Fig. 2b, an inner perimeter lip comprises a first annular protrusion (205a). A second annular protrusion (205b) on the other side is shown in Fig. 2c. The planar surfaces (203a, 203b) have a central aperture. As shown in Fig. 2a, the annular protrusions (205a, 205b) extend outwardly from the central aperture forming a sleeve. The formation of the sleeve covers the gap and/or connection between the joined flanges and provides a smooh continuous surface which allows any flowable material to pass without restriction that may allow contaminant to accumulate. The sleeve also provides sufficient insulated area around the connection of the pipes. The annular protrusion (205a, 205b) includes an annular surface configured to have an outer perimeter that substantially contacts the inner surface or inner perimeter of the pipe. The annular sufaces of the lip are radially supported by the inner surface or inner perimeter of the pipe to provide self-centring adjustment for installation of the gasket (201). 3b. The gasket (301) is configured to allow the annular protrusions (305a, 305b) to be flush with the inner perimeter of the flange. This provides a smooth continuous surface which allows any flowable material to pass without restriction that may allow contaminant to accumulate. The countersunk annular protrusions (305a, 305b) also provide sufficient insulated area around the joined flanges. The inner perimeters of the flanges are substantially in contact with the countersunk annular protrusions (305a, 305b) and radially support the countersunk annular protrusion (305a, 305b) to provide a self-centering adjustment for intallation of the gasket. The suitable length of the annular protrusions for the above embodiments can be determined, for example by:

L = (400 / p) D

where:

L = length of spool fern);

p = electrolyte resistivity (Oxm);

D = nominal pipe diameter (cm).

In order to to prevent crevice corrosion, a suitable epoxy sealant or filler is applied over the annular surfaces (205a, 205b, 305a, 305b) and planar surfaces (203a, 203b; 303a, 303b) of the gaskets (201, 301) prior to installation of the flanges. The planar surfaces (203a, 203b; 303a, 303b) are to be compressed between the flanges in a secured connection. The gasket (201, 301) can be secured by bolting the flanges wherein apertures (401) are provided on the planar surfaces (203a, 203b; 303a, 303b), as illustrated in Figs. 2a, 2b, and 3a, to allow bolts to be inserted. The gasket can also be secured by clamping the flanges in which the planar surfaces (203a, 203b, 303 a, 303b) can be optionally formed with no apertures as shown in Fig. 4. The gasket (201, 301) is made from material compatible with the pipeline fluid. According to the present invention, the gasket (201, 301) is made from suitable sealing material that can withstand compression exerted from the said secured connection and oressure within the pipes such as polvtetrafluoroethylene