CA2973986A1

CA2973986A1 - Method and apparatus to install and remove a sacrificial anode

Info

Publication number: CA2973986A1
Application number: CA2973986A
Authority: CA
Inventors: Mitchell Chibri; Albert Canning
Original assignee: Cool Zone Oilfield Services Ltd
Current assignee: Cool Zone Oilfield Services Ltd
Priority date: 2017-07-20
Filing date: 2017-07-20
Publication date: 2019-01-20

Abstract

A tool is provided for installing and removing a sacrificial anode in a vessel at least partially filled with a fluid, without need for interrupting the operation of the vessel. The tool has a housing and an anode attached to a rod moveable within the housing. The tool may be attached to the vessel via a valve and the rod used to insert an anode into the vessel. The tool may then be secured with a cap.

Description

METHOD AND APPARATUS TO INSTALL AND REMOVE A SACRIFICIAL ANODE
TECHNICAL FIELD
[0001] Tool for installing and removing anodes in a vessel.
BACKGROUND

[0002] Sacrificial anodes are used for the cathodic protection of metal liquid storage vessels, including oilfield tanks and production vessels. Conventional metal liquid storage tanks are susceptible to corrosion during use. Sacrificial anodes are inserted into the tank to inhibit this corrosion. Sacrificial anodes have a limited service life and must be replaced when the corrosion process depletes the anode. Conventionally, replacement of the anode requires an interruption in the operation of the vessel.
SUMMARY

[0003] An apparatus for installing and removing an anode from an operating vessel containing a fluid without disturbing the operation of the vessel. In an embodiment, the apparatus comprises a rod, a housing with a forward opening for connection to a valve and a rearward opening for slideably supporting the rod, the rod being movable relative to the housing between a forward position at which the rod extends through the forward opening and a rearward position, an anode connected to the rod at a portion of the rod forward of the rearward opening; and the apparatus being arranged to form an electrically conductive path between the anode and the operating vessel when the rod is in the forward position. These and other aspects of the device and method are disclosed herein.
BRIEF DESCRIPTION OF THE FIGURES

[0004] Embodiments will now be described with reference to the figures, in which like reference characters denote like elements, by way of example, and in which:

[0005] Fig. 1 is a cross-section of an embodiment of a tool for installing and removing a sacrificial anode.

[0006] Fig. 2 shows a cross-section of the tool of Fig. 1 during installation or removal with a cap removed.

[0007] Fig. 3 is a cross-section of the tool of Fig. 1 disconnected from the vessel.
DETAILED DESCRIPTION

[0008] Immaterial modifications may be made to the embodiments described here without departing from what is covered by the claims.

[0009] Referring to Fig. 1 there is provided a tool 10 for installing and removing a sacrificial anode 12 in a vessel 14 at least partially filled with a fluid 40, without need for interrupting the operation of the vessel. The sacrificial anode 12 operates to cathodically inhibit corrosion of components of the vessel to which the anode is electrically connected.
Vessel 14 may be a tank or pipeline, or may be any container through which a process fluid is flowing or moved. Vessel 14 may be under pressure. Tool 10 allows an anode to be installed or removed for inspection or replacement without process shut down or interruption of production of the vessel.

[0010] Referring to Fig. 3, the tool 10 has a housing 20 adapted to receive a rod 18.
The housing 20 has a vessel end and a free end and may be cylindrical and substantially hollow with a forward opening 56 at the vessel end of the housing and a rearward opening 54 at the free end of the housing. The rearward and forward openings may slidably support the rod 18 and allow the rod to move relative to the housing 20. The rod 18 may be movable between a forward position where the rod extends through the forward opening and a rearward position. The forward opening 56 at the vessel end of the housing is large enough for the anode to pass through, the rearward opening 54 at the free end of the housing is preferably large enough for the rod to pass through, but may not be large enough for the anode to pass through.

[0011] Anode 12 is connected to the rod preferably at a portion of the rod forward of the rearward opening. The rod 18 may be adapted to be reused and to be removably connected to the anode, for example via a threaded connection at anode connector 48.
Alternatively, the rod may be replaced when the anode is replaced, and the rod 18 may be attached to the anode 12 permanently or in such a way that the anode would be difficult to remove or the anode or rod would be damaged upon separation. In an embodiment the anode may be shaped as an elongated rod and may function as the rod 18.

[0012] The rod 18 may have a gripping area 42 where the rod may be gripped by hand or by a tool to control and move the rod, preferably at the opposing end of the rod to the anode. The anode may be any shape, for example the anode may be substantially cylindrically shaped as shown in Figs. 1 and 2. Rod 18 may be longer than the housing so that it may extend from both ends of the housing simultaneously.

[0013] The anode must be electrically connected with the portions of the vessel to be cathodically protected, for example the inner layers of the tank walls 16.
Preferably the tool is configured to form an electrically conductive path between the anode and the desired portion of the vessel when the rod is in the forward position. At least part of the tool may be electrically conductive to achieve this connection. For example, the rod may be at least partly electrically conductive and contact a metallic portion of the tool, for example the housing.
The electrical connection may also be made through a wire or other metallic connection placed between the anode and the vessel part to be protected. A wire (not shown) may be for example connected between the anode and the housing. Where a conductive path is formed between the anode and the housing, the housing and valve may be electrically conductive to form a conductive path to the tank walls. The anode may be made of any material suitable to develop an electrochemical potential between the anode and the metal surface to be cathodically protected.

[0014] When the tool is installed on the vessel a central bore of the housing 20 may be in fluid communication with the tank. Tool housing 20 may have a seal 36 near the free end of the housing which contacts the rod 18 to create a fluid tight seal and prevent fluid 40 from leaking out the rearward opening. There may be a drain valve 24 connected to the housing 20. The drain valve is preferably located at a low point of the tool, for example on the underside of the tool when it is installed to facilitate drainage of any fluid within the housing. A container may be positioned below drain valve 24 to collect any fluid flowing out of the drain valve.

[0015] The housing 20 is configured to attach directly or indirectly to the vessel at an opening in the vessel. As shown in Figs. 1 and 2, the housing 20 is configured to attach to a valve 30 which is connected to the vessel. The valve 30 may be opened and closed by handle 46. A flange 22 on the vessel end of the housing may be removably connected to a corresponding flange 44 on valve 30. Housing 20 may also be threadably connected to the valve 30 with or without a flanged connection. With a threadable connection flange 22 may be secured onto the valve 30 and the housing twisted onto and off of the flange attach and remove the tool to the vessel. Valve 30 may be removably connected to the vessel by another flange 52 which aligns with a corresponding flange 50 on the vessel. In another embodiment the housing 20 may include valve 30 and the valve end of the housing may have flange 52 which may be attached to the vessel. The flanges may be removably attached using bolts or other removable attachments.

[0016] The housing attaches to the vessel at opening 26 in the wall 16 of the vessel 14. Opening 26 may be a nozzle, and may be 4" and be installed with a repad or other reinforcement. The opening is preferably installed at the desired height for the anode to rest in the vessel 14, and may be installed by a welder or tank manufacturer. The opening 26 may be installed in the field while the tank is producing.

[0017] In one method of inserting an anode into a vessel, anode 12 may be connected to rod 18. Rod 18 may then be pulled so anode 12 clears flange 22 and is in a rearward position relative to the housing as shown in Fig. 2. Tool housing 20 is removably attached to a valve 30 mounted on the vessel 14, for example by bolting flange 22 on the tool housing to valve 30. Drain valve 24 on tool housing 20 is closed and may be sealed, for example with a plug. Valve 30 is opened and rod 18 is moved into a forward position relative to the housing.
To move the rod into the forward position, the anode 12 moves through valve 30 and nozzle 26 into vessel 14. Rod movement may be limited at a predetermined position by a stop 28 on rod 18 which contacts an end of the tool housing 20 and prevents the rod from moving further through the tool housing 20. When the anode is positioned a cap 32 may be installed onto the free end of the tool housing. Cap 32 may be configured to sealably connect around the rearward opening of the housing and may prevent movement of the rod when the anode is in place and further prevent leakage of fluid 40. There may be a cap valve 34 on cap 32, which may be closed after the cap is installed and may be further sealed, for example with a plug.

[0018] In another embodiment, when installed on the vessel 14 the anode 12 may remain within the tool 10 and function as a sacrificial anode. In this position valve 30 is open allowing fluid 40 to contact anode 12, and anode 12 is electrically connected to the component of the vessel to be protected either through tool components or an added metallic connection such as a wire.

[0019] In one method of removing an anode from a vessel for inspection or replacement, cap valve 34 is opened to check if any fluid has leaked by the seal 36. Cap 32 is removed and rod 18 is pulled back so the anode 12 clears valve 30 and may rest within tool housing 20. Valve 30 is closed then drain valve 24 is opened to drain any fluid in tool housing 20. When the liquid is drained the tool housing is unattached from the valve at flange 22 and the tool is removed from the side of the vessel. The rod may then be pushed into a forward position so the anode clears the flange 22 allowing inspection or removal of the anode if necessary, as shown in Fig. 3.

[0020] When installing or removing an anode from a vessel the tool may be positioned to radially extend from the vessel.

[0021] Housing 20 may include an internal slope 38 to aid in directing the anode or rod to the opening of the vessel end of the housing.

[0022] If tool 10 is installed in the field while the vessel 14 is producing a hot tap may be required through a valve and nozzle, for example a 4" hot tap. Once this is completed only maintenance crews will be required to finish installation or for later inspections or anode changes.

[0023] In the claims, the word "comprising" is used in its inclusive sense and does not exclude other elements being present. The indefinite articles "a" and "an"
before a claim feature do not exclude more than one of the feature being present. Each one of the individual features described here may be used in one or more embodiments and is not, by virtue only of being described here, to be construed as essential to all embodiments as defined by the claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An apparatus for installing and removing an anode from an operating vessel containing a fluid without disturbing the operation of the vessel, the apparatus comprising:
a rod;
a housing with a forward opening for connection to a valve and a rearward opening for slideably supporting the rod, the rod being movable relative to the housing between a forward position at which the rod extends through the forward opening and a rearward position;
an anode connected to the rod at a portion of the rod forward of the rearward opening; and the apparatus being arranged to form an electrically conductive path between the anode and the operating vessel when the rod is in the forward position.

2. The apparatus of claim 1 in which the rod is at least partly electrically conductive and contacts the housing to form the electrically conductive path.

3. The apparatus of claim 1 or claim 2 further comprising a drain valve connected to the housing.

4. The apparatus of any one of claims 1-3 further comprising a cap configured to sealably connect around the rearward opening of the housing.

5. The apparatus of claim 4 in which the cap has a cap valve.

6. The apparatus of any one of claims 1-5 in which the housing has a seal for slideably sealing with the rod at the rearward opening.

7. The apparatus of any one of claims 1-6 in which the anode is removably connected to the rod.

8. The apparatus of claim 7 in which the anode is threadably connected to the rod.

9. A method for installing an anode into an operating vessel, the method comprising the steps of:
connecting a forward opening of a housing to a valve connected to the operating vessel, the housing having a rearward opening slideably supporting a rod, the rod having an anode connected t o the rod at a portion of the rod forward of the rearward opening;
opening the valve; and moving the rod to a forward position at which the rod extends through the forward opening and is electrically connected to the operating vessel.

10. The method of claim 9 further comprising the step of installing a cap around the rearward opening of the housing.

11. The method of claim 9 further comprising removing the anode from the operating vessel by the steps of:
moving the rod to a rearward position at which the rod does not extend through the forward opening;
closing the valve; and disconnecting the housing from the valve.

12. The method of claim 10 further comprising removing the anode from the operating vessel by the steps of:
removing the cap;
moving the rod to a rearward position at which the rod does not extend through the forward opening;
closing the valve; and disconnecting the housing from the valve.