SACRIFICIAL ANODES – CATHODIC PROTECTION

SACRIFICIAL ANODES - CATHODIC PROTECTION

SACRIFICIAL ANODES – CATHODIC PROTECTION

Installation in soil

  • Soil anodes are usually pre-packaged in backfill (gypsum/bentonite) in cotton bags. Pre-packaged anodes should be kept dry during storage. If individually pre-packaged anodes are delivered in waterproof containers, these containers must be removed before installation.
  • Prior to the installation, sacrificial anodes shall be inspected for defects, conformance with the anode specification and size and length of anode cable tails. Care must be exercised to avoid damaging anodes during handling and installation. Cable tails should be visually inspected for defects in insulation.
  • The location in relation to the object to be protected and the installation depth of the anode shall be checked against the design.
  • Before installation, the anode with backfill shall be soaked in water for at least 4 hours. Pre-packaged anodes shall be installed in augered holes, watered down and backfilled with native soil.
  • Where anodes and backfill are provided separately, anodes should be centred in the hole and surrounded by the special backfill. This backfill shall be fully wetted and compacted prior to backfilling with native soil.
  • Anode leads shall be terminated into a test station ( JUNCTION BOXES AND TEST FACILITIES &  CATHODIC PROTECTION ). The test station shall be located such that anode cables are kept as short as possible.
  • The checklist for recording the installation and commissioning test results ( CATHDIC PROTECTION SYSTEM COMMISSIONING ) should be used.

Marine anodes, above water installation

  • Anodes that are installed above water are for instance:

–    platform anodes during new construction;

–    ship’s anodes during new construction or retrofitting during dry docking;

–    internal tank anodes (storage tanks, ship’s ballast tanks) during maintenance shutdown or repair;

–    anodes for SBMs or mooring systems.

  • Location of the anodes and different anode types/sizes shall be checked against the design. For asymmetrical anodes, the design may specify which face of the anode should point towards the structure. In some cases certain anode faces need to be painted.
  • Anodes shall be fully welded to the steel structure unless the anodes are specifically designed to be replaced without welding during the life of the system (e.g. SBM anodes, some tank anodes). When anodes are to be bolted to supports, e.g. using U-bolts a tack weld shall be made between the anode core and the support to ensure low electrical contact resistance.
  • When retrofitting anodes, specially on coated surfaces, all old anode cores and supports that are not re-used should be removed where possible.
  • When replaceable anodes are installed, the distance between supports shall be as specified to allow the anodes to be interchanged without problems. All dimensions shall be recorded for future reference.
  • Installation on coated surfaces may require special precautions, such as:

–    Anode cores and supports may need to be coated to the same standards as the structure coating.

–    During installation of anodes on coated areas, coating damage by dragging or dropping anodes or by weld spatter, etc. shall be avoided.

–    If coating operations are required after the installation of the anodes is complete, the anodes shall be protected from painting by wrapping them in paper or covering them with soft soap. The paper wrapping shall be removed after painting. Plastic wrapping is not recommended, and grease shall never be used for the protection of anodes during painting.

The checklist for recording the installation and commissioning test results (CATHDIC PROTECTION SYSTEM COMMISSIONING) should be used.

Marine anodes, under water installation

  • Anodes that are installed under water are for instance:

–    Jetty anodes installed after piling;

–    Jetty and platform anodes for retrofitting;

–    retrofit anodes for SBMs or mooring systems;

  • The same procedures may be used when installing anodes above water where welding is not allowed.
  • Underwater installation is usually performed using divers.
  • Where possible, anodes should be installed using underwater welding. When welding to critical members of a structure, the welding procedures should be verified and approved.
  • Anodes may be installed using mechanical means such as bracelets or G-clamps to which they should be welded before installation. Bracelets should be provided with at least one contact bolt per half bracelet. In G-clamps the clamping bolts should serve as contact bolts. Contact bolts should have a rough flat face contacting the structure, providing sufficient friction to prevent loosening of the bolt and providing sufficient contact surface. Pointed bolts should not be used. Contact bolts should be tightened with sufficient torque to cut through any scale and paint. The contact of a clamped connection should be checked where possible. Normally, the resistance of the clamped connection is not greater than 0.01 W.
  • Specially designed anode-bolting attachments may be available. If mountings of this type are used, the contact faces should be clean and free of paint or scale. Serrated washers should be used to ensure a lasting electrical contact.
  • The checklist for recording the installation and commissioning test results (CATHDIC PROTECTION SYSTEM COMMISSIONING) should be used.

Subsea Pipeline anodes

  • Subsea pipelines are normally provided with bracelet anodes, supplied as two half bracelets. The half bracelets may be half shells of anode material or segmented anodes, consisting of slender anodes welded to a steel bracelet. Depending on the design the two halves are connected by bolting or welding. The anodes should be installed so as to prevent slippage.
  • It is recommended to apply a epoxy type coating on the inner surface of the bracelet anode facing the pipe, to the surfaces facing the concrete coating and to the exposed parts of the steel bracelet.
  • Electrical contact with the pipe may be made by installing an electrical cable between the bracelet and the pipe or by welding a steel strip between the bracelet and the pipe. When the two half bracelets are only bolted together, one cable per half bracelet is required. Welding to the pipe shall be done using approved welding procedures. Attachment of cables to the pipe shall be done in accordance with ( CABLE INSTALLATION OF CATHODIC PROTECTION ).
  • The anodes shall be installed over the anti-corrosion coating. Any cut-outs in the coating to attach electrical connections shall be repaired to standards similar to the original coating.
  • When installing anodes on concrete coated pipes, the gaps between the concrete and the anode shall be filled using a suitable type of concrete or mastic. Electrical contact between the concrete reinforcement steel and the anode is not permitted.
  • When installing non-tapered bracelet anodes on pipes without concrete coating, additional plastic tapers may have to be installed in accordance with the design.
  • The checklist for recording the installation and commissioning test results (CATHDIC PROTECTION SYSTEM COMMISSIONING) should be used.

 

paktechpoint.com

You may also like...

Leave a Reply

error: tected !!Content is pro
%d bloggers like this: