Rehabilitation and protection of internal tank weld seams

The Problem
During Ecopetrol’s integral maintenance service of its naphtha storage tank, the perimeters of the tank weld seams (#1 and #2) were determined as being the most critical areas, showing great loss of metal due to corrosion.

Ecopetrol, formerly known as Empresa Colombiana de Petróleos S.A. (Colombian Petroleum Co.), is the largest and primary petroleum company in Colombia. As a result of its continuous growth, Ecopetrol forms part of the Fortune Global 500. The company is among the 25 largest petroleum companies in the world and is one of the four principal petroleum companies in Latin America.

Defects and structural heterogeneities led to welded joint deterioration. These areas, exposed to aggressive conditions such as water, chlorides, sulfides, and high operating pressure, develop this form of localized corrosion.

For this situation, the variables that were present in the process were evaluated, as well as the characteristics of the process (dimensions, vibration, compression, bending, temperature, etc.).

Solutions that Work

Due to its excellent flexural, elongation and tensile properties, as well as its chemical composition providing a durable and protective solution against corrosion, it was proposed to apply MCOR 3115 | mClad mFill to the affected areas, using a minimum thickness of 1 mm (40 mils) for filling, reinforcing, and sectional lining. This product would be used to recover the lost metal, protect effectively under immersion, and avoid possible faults caused by movements.

With her experience and knowledge of NACE and SSPC standards, María Cathalina Jiménez, Chief Metallurgical Engineer for Imantt (MCOR Colombia), oversaw the project in order to ensure proper application and compliance with each of the steps stipulated by the MCOR 3115 specifications and process.

As with all Imantt solutions, the goal was to use MCOR products to reduce downtime and achieve excellent efficiency and product performance.

Products that Out-Perform
MCOR 3115 | mClad mFill is a two-component, high-strength epoxy paste. It is extremely forgiving and tolerant, vertical and overhead, is non-sag, and sets quickly. Packaged in a convenient 1:1 mix ratio, it can be used for general industrial grade repairs, reclaiming, resurfacing, and as patch filler for metal. Epoxy-based and highly modified with fibers and ceramics, the material is a durable, sealed protective solution to combat corrosion.

No-Nonsense Applications
In order to ensure the adhesion properties and the corrosion protection of the substrate, cleaning was carried out to the standards of NACE No. 1 / SSPC-SP 5, “White Metal Blast Cleaning.”

“White metal blast cleaning” welding 1 – 2

“White metal, blast cleaning“ welding 3- 4

During the entire application process, temperatures and environmental conditions were controlled and monitored in order to minimize the occurrence of condensation and to monitor relative humidity, making sure to comply with the ranges required by MCOR and industry standards.

Once the ambient and environmental parameters were recorded, the wet film thickness was measured throughout the entire process to ensure proper thicknesses and uniformity. This is key to the performance and efficiency of the product.

The quality and integrity of the coating was assured using an anchor profile test to confirm the desired cleaning and dry film thickness of 1 mm minimum (40 mils). Likewise, adhesion tests were performed in welding seams #1 and #2, according to the requirements of ASTM D4541, “Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers,” quantitative type, complying with the minimum requirements of SSPC and the manufacturer’s technical data sheet.

It is important to highlight the failure mode because no percentage of detachment of the product was observed.

Arbitrary thickness measurements were made in three areas of 25 m2 on weld seam #1, registering a minimum thickness of 1 mm (40 mils) and a maximum of 1.32 mm (52 mils).

Bond strength = 2,287 psi

“White metal, blast cleaning“ welding 3- 4

Arbitrary thickness measurements were made in three areas of 25 m2 on weld seam #2.

On weld seam #2, the failure mode also demonstrated zero percentage of MCOR 3115 bond failure or detachment of the product.

Bond strength = 2,496 psi

A Final Look
As a final inspection, a verification of film continuity was performed in accordance with ASTM D 5162, “Standard Practice for Discontinuity (Holiday) Testing of Nonconductive Protective Coating on Metallic Substrates.”

A final inspection of MCOR 3115 was carried out by the Reliability Department of Ecopetrol. They expressed their satisfaction with the application completed by the Imantt / MCOR team and confirmed its compliance. Once the quality control tests were completed, the application and presentation of the epoxy coatings were approved by Ecopetrol and the contractor proceeded to apply a final top coat to tie into the rest.

PROJECT: Rehabilitation and protection of internal tank welding
DATE: November 2018
OWNER: Ecopetrol S.A.
PRODUCT: MCOR 3115 | mClad mFill
APPLICATOR: Imantt Solutions, exclusive distributor for MCOR (Colombia)

Application overseen by: Eng. María Cathalina Jiménez, MCOR Specialist
Inspection completed by:  Imantt (Engineering Department)
Approved by: Imantt (Engineering Department) + Ecopetrol
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