Method and apparatus for protecting a flange

Flanges are often subject to corrosive marine environments and/or fire-prone environments when they are employed in applications such as offshore drilling and production platforms, or other marine applications. An apparatus and method to protect the flange from such corrosive environments and fire has been discovered. The apparatus is removable and reusable which allows the flange to be inspected and repaired when necessary.

FIELD OF THE INVENTION 
The instant invention relates to a method and apparatus for protecting a 
flange. More particularly, the invention relates to a method and apparatus 
for protecting a flange from corrosion or fire in the splash zone of a 
marine environment. 
BACKGROUND OF THE INVENTION 
Flanges, i.e. ribs or rims extending from a pipe, are often used when 
connecting two pipes together because of the ability to disassemble the 
pipes when necessary. The flanges may be part of the pipe itself, such as 
a flanged-end pipe, or may be connected to the end of the pipe via a 
variety of means. Flanges which connect to the end of the pipe include, 
for example, screw-on flanges, slip-on flanges, socket-weld flanges, 
lap-joint flanges, welding neck flanges, and blind flanges. These flanges 
are illustrated in, for example, Perry's Chemical Engineers' Handbook, 
Sixth Edition, McGraw Hill Book Company, 1984, p. 6-46, which is 
incorporated by reference. The flanges often have a gasket between them 
which, unfortunately, may be flammable and could result in a leak in the 
event of a fire. The flanges are bolted together. Typical gaskets and 
bolting means are illustrated in, for example, Perry's Chemical Engineers' 
Handbook, Sixth Edition, McGraw Hill Book Company, 1984, pp. 6-46 through 
6-50, which is incorporated by reference. 
Often pipes connected by flanges are to be utilized in applications which 
require that the pipes and flanges be subjected to an external environment 
which is corrosive and/or subject to fire. An example of such is offshore 
drilling and production platforms, or other marine structures, wherein the 
pipes and flanges are subjected to the corrosive salt water of the ocean 
and possible fires due to the flammability of the produced oil and gas. 
While methods and apparatuses have been developed which are used to 
protect the pipes from the corrosive environment and fire, the methods and 
apparatuses are generally not effective when used for a flange. Methods 
and apparatuses to protect pipes include those of U.S. Pat. Nos. 
5,087,154; 5,591,265; and 5,226,751. 
U.S. Pat. No. 5,087,154 relates to a protective coating which has two 
uninterrupted and encapsulating and superposed layers of a marine 
resistant epoxy composition and a thin layer of reinforcing composition 
between the layers. Correspondingly, U.S. Pat. No. 5,591,265 relates to a 
protective coating which has a formwork around a tube to be protected, an 
annular space between the tube and formwork, a means to apply a curable 
resin to the annular space, a seal means, and a support ring secured to 
the tube. Unfortunately, the protective coatings taught in these two 
patents are adapted especially for pipes and if used on a flange would be 
difficult to secure around the flange and completely encompass the flange 
due to the flange's shape. Therefore, the flange would not be fully 
protected in many instances. In addition, the protective coatings of the 
two patents are not adapted for removal and replacement. Therefore, if 
inspection, repair, or replacement of the flange becomes necessary after 
the protective coating is applied, then the protective coating would have 
to be removed at considerable cost or the entire flange would have to be 
cut from the pipe. 
U.S. Pat. No. 5,226,751 relates to a process for creating a controlled 
environment about a submerged pile by placing a jacket around the pile and 
then injecting air and a preheated gas into the jacket to dry the pile. 
After the pile is dry, the jacket is filled with a firm resilient 
non-corroding compound such as an expanding closed cell foam formed from 
liquid chemicals or epoxy resins. Unfortunately, if this process was 
employed on piling containing a flange, then the jacket would leave a very 
large annular space around the pipe where the flange is located. This 
would necessitate using a large amount of the very expensive filler. In 
addition, if the flange needed to be inspected, then it would require 
removing the protective covering which covers the pipe, as well as, the 
flange. 
Another method which is often employed to protect flanges is that of 
cathodic protection. Cathodic protection, as described in, for example, 
Encyclopedia of Science and Technology, Vol. 4, pp. 440-445, McGraw-Hill, 
1992, generally involves applying a cathodic potential, or current, to the 
flange. The cathodic potential prevents the flange from undergoing an 
anodic reaction, M.fwdarw.M.sup.n+ +ne.sup.-, which causes corrosion. This 
is often achieved by applying a cathodic current through an auxiliary 
electrode (impressed current) or by coupling the metal to be protected 
with a metal having a more negative open circuit potential (sacrificial 
anode). Unfortunately, such cathodic protection is often uneconomical. 
Additionally, cathodic protection is not particularly effective for 
flanges which are subject to both wet and dry conditions, such as flanges 
in a splash zone of an offshore drilling and production platforms, or 
other marine structures. 
It would be desirable if an alternate method and apparatus suitable for 
protecting flanges from corrosion and/or fire could be developed. It would 
be beneficial if such an apparatus was adapted to be removed so that the 
flange could be inspected and repaired when necessary. It would be 
advantageous if the apparatus could be reused after removal from the 
flange. It would further be desirable if such flange protection could be 
accomplished in an environment which is subject to both wet and dry 
conditions, impact, abrasion, or ultraviolet light. 
SUMMARY OF THE INVENTION 
An apparatus and method have been discovered which protects flanges from 
corrosion and/or fire. The apparatus comprises a corrosion-resistalnt 
housing which is adapted to encapsulate a flange to be protected. The 
housing comprises a first section and a second section which are attached 
to define a substantially air-tight annular space. A first port is located 
on the housing and is adapted for the injection of a corrosion-inhibiting 
substance into the annular space. A second port is located on the housing 
and adapted for the expulsion of fluids which are present in the annular 
space prior to injection of corrosion-inhibiting substance. 
Advantageously, the flange protection apparatus may be removed and reused. 
In addition, the flange protection device may be particularly useful in 
corrosive, wet-dry, and fire-prone environments.

DETAILED DESCRIPTION OF THE INVENTION 
The instant invention is particularly useful for protecting flanges in a 
corrosive environment. As used herein, "corrosive environment" means any 
environment which reacts with the flange to electrochemically degrade the 
flange. The corrosion reaction is often of the form M.fwdarw.M.sup.n+ 
+ne.sup.-, wherein M is the metal from which the flange is made, M.sup.n+ 
is an oxidized form of the metal after corrosion, e is an electron, and n 
is the number of electrons. Corrosive environments often include water or 
air which contains NaCl, high temperatures, alternate wet and dry 
conditions, acidity, or basicity. Among applications for which the instant 
invention is particularly useful are offshore drilling and production 
platforms, or other marine structures, which due to their location in the 
splash zone or tidal zone, subject a flange to a corrosive environment. In 
addition, the flange protection device is useful for applications which 
may subject the flange to a risk of fire. 
The apparatus of the instant invention employs a housing which is adapted 
to encapsulate a flange. The particular material of which the housing is 
comprised is not particularly important so long as the material is 
corrosion-resistant, i.e., the material does not electrochemically degrade 
substantially when subjected to a corrosive environment for extended 
periods of time. In addition, the material is preferably fire-resistant if 
the device is to be utilized for an application which may subject the 
flange to fire. It is also preferred that the material be impact and 
abrasion-resistant if it is to be subjected to such forces as waves, 
tides, or floating debris. Particularly preferred materials for the 
housing are steel, thermoplastics, thermoset composites, or mixtures 
thereof. A particularly preferred material is a thermoset composite due to 
its excellent ability to resist degradation by chemicals and ultraviolet 
light. 
The shape of the housing is not particularly critical so long as an annular 
space exists between the housing and the flange. Since the annular space 
will be injected with a corrosion-inhibiting substance, as described 
below, it is usually advantageous to select a shape for the housing which 
will minimize the volume of annular space. In this manner, the amount of 
liquid which is necessary to fill the annular space will also be 
minimized. A particularly preferable shape, therefore, is hemicylindrical 
as shown in FIG. 3. 
Another consideration in regard to shape is the type of material to be 
utilized. As one skilled in the art will appreciate some materials are 
more difficult to mold into certain shapes, or when molded into a certain 
shape are less strong. For example, many composite materials are difficult 
to mold into shapes having sharp edges or contours, for example, 
90.degree. angles, while maintaining the structural integrity of the 
shape. For this reason, it may be desirable to avoid such shapes having 
90.degree. angles and employ shapes which tend to be more circular or 
cylindrical when utilizing composite materials. 
The housing is comprised of two or more sections in order that the housing 
may be easily removed when inspection or repair of the flange is 
necessary. The sections are attached such that the annular space is 
substantially airtight and watertight. In this manner, no corrosive 
elements may enter the annular space and attack the flange. The means of 
attachment may be any means which facilitates a substantially airtight and 
watertight fit between or among the sections. While the actual number of 
sections may depend upon the size and shape of the flange to be protected, 
usually two mirror-image sections are most practical in order to 
facilitate the attachment, i.e., typically it is less burdensome to attach 
two sections as opposed to three or more. 
As stated above, the attaching means may be any means which facilitates a 
substantially airtight and watertight fit between or among the sections. 
It is also preferable that the attaching means be such that the sections 
may be detached relatively easily when inspection or repair of the flange 
becomes necessary. The actual attaching means employed is often dependent 
upon the type of material used for the housing, as well as, the number of 
sections in the housing. For instance, if the material is fairly rigid, 
such as steel, then a bolt and nut often adequately serve to attach the 
sections. However, if the material is pliable, for example, a 
thermoplastic such as rubber, then often a clamping means is most 
desirable to press the sections together. In some instances, a glue may 
even be utilized so long as the glue provides an airtight and watertight 
seal between or among the sections and yet still allows one to detach the 
sections relatively easily if inspection or repair of the flange is 
necessary. 
While it is usually not critical to the flange protection device if the 
sections of the housing are adequately attached, in some instances a 
sealing means between or among the sections of the housing may be useful. 
Such a sealing means is most often necessary when the housing is comprised 
of an inflexible material such as steel because an incomplete seal between 
or among the sections may exist due to the sections not fitting perfectly 
together. On the other hand, if the housing is comprised of a 
thermoplastic such as rubber, then often no seal is necessary. 
The sealing means should be corrosion-resistant and act to prevent leakage 
of air or water into the annular space. Along the same lines, the sealing 
means acts to prevent leakage of a corrosion-inhibiting substance from the 
annular space to the external environment. Such a sealing means may be 
simply a piece of rubber which contacts the lateral surface of a housing 
section at the point where the section is attached to another section. 
Such a means may be referred to simply as a seal or a gasket. 
A first port is located on the housing and is adapted to allow a 
corrosion-inhibiting substance to be injected into the annular space. A 
second port is also located on the housing and adapted for expelling any 
fluids, whether they be liquids or gases, which are present in the annular 
space prior to the injection of corrosion-inhibiting substance. The fluids 
which are present prior to injection often include seawater, freshwater, 
air, or combinations thereof when the flange is being utilized in the 
splash zone of a marine environment. The ports are preferably capable of 
being opened or closed by, for example, a valve. 
The first or second port is also useful for removing, for example draining, 
the corrosion-inhibiting substance when repair or inspection of the flange 
is necessary. In addition, either port or an additional port may be 
employed to reduce the pressure within the flange protection device in the 
event of a leak from the flange. If leaking from the flange is likely then 
it may be desirable to include a pressure sensing device within the flange 
protection device. In this manner, if a leak does occur, the port may be 
opened to prevent the flange protection device from bursting. 
The first and second port may be located anywhere on the housing so long as 
the existing fluids in the annular space are ejected upon the introduction 
of corrosion-inhibiting substance. Generally, it is most convenient and 
practical to orient the two ports such that gravity may be used 
advantageously. For example, when the first port is located below the 
second port, then the introduction of corrosion-inhibiting substance 
pushes the existing fluids upward and out of the second port into the 
external environment. When substantially all of the annular space is 
filled with the corrosion-inhibiting substance and, correspondingly, 
substantially all of the existing fluids have been expelled, then the 
ports are closed and the flange is protected. 
The corrosion-inhibiting substance for use in the annular space of the 
present invention may be any substance which either retards, slows, or 
reverses electrochemical degradation of the flange. Likewise, a 
corrosion-inhibiting substance may break down the corrosion product such 
that the flange is cleaned. The type of corrosion-inhibiting substance 
employed may be a solid liquid, gas, foam, gel or any other form which may 
be injected into the annular space. It is generally preferable that the 
substance be a liquid at 25.degree. C. such that the substance may be 
easily injected into the annular space, drained and replaced easily if 
such becomes necessary. It is also generally preferable that such a liquid 
does not freeze and expand at temperatures to which the flange protection 
device will be subjected. In this manner, the housing of the flange 
protection device will not be subjected to stress due to the expansion of 
the substance within the annular space. 
The corrosion-inhibiting substance may vary depending upon the amount of 
time the flange is to be protected, the susceptibility of the particular 
flange to corrosion, and the amount of corrosion which may have already 
occurred. One skilled in the art will readily recognize that if a flange 
is to be protected for a period of, for example, 10 years then a different 
corrosion-inhibiting substance may be chosen than if the flange is only in 
need of protection for a period of, for example, 1 year. Likewise, one 
skilled in the art will readily recognize that if a particular flange is 
very susceptible to corrosion then a stronger corrosion inhibitor may be 
necessary and if substantial corrosion of the flange has already occurred, 
then an inhibitor which breaks down the corrosion product and cleans the 
flange may be necessary. 
Corrosion-inhibiting substances useful in the invention may be prepared 
individually or may be obtained commercially. Among corrosion-inhibiting 
substances which are useful in the instant invention include citric 
acid-type metal conditioners and rust removers. These corrosion-inhibiting 
liquids typically comprise citric acid, esters, or mixtures thereof. Other 
corrosion-inhibiting liquids include Bioguard.TM. available from Royal 
Lubricants Company, Inc., Rusteco R-200-3.TM. available from TMT Services 
Corp., and other commercially available corrosion inhibitors or mixtures 
thereof. Alternatively, two or more substances which do not individually 
exhibit corrosion-inhibition properties could be injected into the annular 
space and react to form a corrosion-inhibiting substance within the 
annular space. 
FIG. 1 illustrates an unprotected flange located in the splash zone of a 
production platform. FIGS. 2 through 5 illustrate different views of a 
preferred flange protection device according to the present invention. 
There is illustrated a first pipe 10 having an extended rim 12 on each 
side and connected to a second pipe 11 having an extended rim 13 on each 
side. A bolt 14 and a bolt 15 extend through the rims and hold the pipes 
together. The flange protection device, 6, encompasses the flange and that 
part of the pipe, 16, immediately adjacent to the flange. The flange 
protection device, 6, is comprised of two mirror-image, hemicylindrical 
sections, 17 and 18. Each hemicylindrical section is comprised of a 
thermoset composite and has a top neck, 19, and a bottom neck, 20, which 
are at opposing ends of the flange protection device. The necks 
substantially conform to the shape of the pipe but are a bit larger in 
diameter than the pipe. In this manner, if the pipe has a corrosion 
protection substance on it such as ArmorGard.TM. or RiserClad.TM. 
available from Riserclad International Inc., then the necks of the flange 
protection device will still be large enough in diameter to surround the 
pipe. The necks are in communication with the pipe (a seal may be used if 
necessary) to prevent ingress of air and water, as well as, egress of 
corrosion-inhibiting substance. 
A first port, 21, is located immediately adjacent to the bottom neck, 20, 
of a hemicylindrical section, 18, of housing. The port is adapted such 
that when it is open, a corrosion-inhibiting substance may be injected 
into the annular space, 23. A second port, 22, is located immediately 
adjacent to the top neck, 19, on the mirror-image hemicylindrical section, 
17, of the housing. The second port is adapted such that when it is open, 
any fluid which are present in the annular space, 23, prior to injection 
of corrosion-inhibiting substance are expelled. Upon the filling of the 
annular space with corrosion-inhibiting substance and the expulsion of 
substantially all of the prior fluids, the first port 21 and the second 
port 22 are closed. A valve or plug is adapted to control the opening and 
closing of the port. 
A rubber seal, 24, is located between the two mirror-image hemicylindrical 
sections along the length. The seal acts to provide a cushion between the 
two sections and allow them to be fastened together firmly without harming 
the sections of housing. Rims, 25 and 26 extend the length of each section 
of housing in the z-plane direction, i.e., out of and into the plane of 
the figure. The rims are comprised of the same material as the housing and 
are part of each section of the housing. Five bolts, 27, extend through 
corresponding holes on each rim, 25 and 26, each bolt having a nut, in 
order to fasten the two sections of housing together such that the annular 
space is airtight. 
The flange protection devices and methods of the instant invention allow 
the flanges to be protected from corrosion for extended periods of time. 
Surprisingly, it is contemplated that flanges may be protected from 
substantial corrosion for as long as 2, preferably as long as 5, more 
preferably as long as 10 or more years. Periodically, it may be necessary 
to inspect and/or repair the flanges due to regulatory or safety 
requirements or harsh weather such as tropical storms, heat, or cold. When 
such inspection or repair becomes necessary, the bolts, 27, are removed 
and the sections, 17 and 18, of the housing are removed to reveal the 
flange. It may be desirable in some instance to open port, 21, in order to 
drain the corrosion-inhibiting substance before removing the bolts. 
Depending on the corrosion-inhibiting substance, it may be desirable to 
separate the substance from the oxidized material, e.g., rust, which may 
be present in the substance. This may be done by, for example, decanting 
if the substance is a liquid. in this manner, the corrosion-inhibiting 
substance may be reused. After the inspection and/or repair has been 
completed, the flange protection device may be reused on the same flange 
or an alternate flange.