Belzona Test Report
With the introduction of ISO / ASME compliant SuperWrap II repairs onto manually prepared substrates it is imperative to ensure the repair area is prepared to the required standard, SSPC-SP11. Therefore, we are investigating power tools which can provide the necessary standard, whilst also ensuring safe use in explosive environments. The following report details the results from profile testing, adhesion testing and hydrostatic testing relating to a non-spark tool and values gathered from previous testing when using the rotary wire brush during the ISO / ASME SuperWrap II compliance testing.
• Sapeg’s RUST ATEX Grinder with tungsten carbide disk attached.
• Twist knot wheel rotary wire brush.
• PosiTest AT-A with 14mm dolly.
• Elcometer Digital Profile Gauge.
On first impressions the non-spark tool looks like a well manufactured, air driven, 4” grinder with a grinding disk attached, plus an additional 4 different shaped burrs within the kit. The grinding disk houses 24 tungsten carbide teeth which are incredibly tough, resulting in a long working lifetime. The burrs, which are also manufactured from tungsten carbide, look of a standard type and along with the grinding disk, do not produce many sparks. The reasons for this being the slow speed of rotation and the properties of the tungsten carbide teeth, which reduces the surface heating and spark temperature, ensuring the temperatures involved are kept below the limits to obtain the ATEX approval. The tool has an option to supply, however this is not necessary to achieve the ATEX approval.
From the testing undertaken it is certainly non-spark but whether this could be proven and accepted on sites is another matter.
It was decided to do a direct comparison between the rotary wire brush and the non-spark tool to give us some form of meaningful valuation. The key areas that were focused on were:
• Preparation Rate
• Surface Cleanliness
• Profile Testing
• Adhesion Testing
• Hydrostatic Testing
There was not a large difference in the speed of preparation between the rotary wire brush and the non-spark tool. However, it was much easier for the operator to achieve the required rough and clean surface using the non-spark tool when applying comparable force. The rotary wire brush seemed to require more pressure to be applied to remove mill scale. The non-spark tool creates the desired cleanliness and roughness.
Both the tools can obtain the required near white metal surface cleanliness, however as mentioned above, it requires an increased amount of pressure to achieve the necessary cleanliness using the rotary wire brush compared with the non-spark tool.
Only the non-spark tool was used on a flat steel panel, however both the rotary wire brush and the non-spark tool spool was used in the process of hydrostatic testing of the Belzona SuperWrap II system.
It was found that both the tools achieved the required surface preparation standard of SSPC-SP11 even on complex geometries. The maximum profile achieved using the non-spark tool was 234-microns. These deep grooves were cause by excessive pressure being applied by the operator. The profile depth was variable over the repair area, with the average value equaling 73-microns, which is greater than the required 25-microns stated by the standard. Also, this figure is just less than the 75-micron roughness profile that Belzona specifies for a coating application.
The average profile achieved using the rotary wire brush equaled 30-microns, which is within the requirements. However, more effort is required to achieve a reduced roughness value, compared with the non-spark tool. The reduced roughness values could occur due to the superior mechanical properties of the tungsten carbide, compared with the steel wire brush.
A 10mm thick carbon steel plate was prepared by the non-spark tool. One section coated with Belzona 1161 and the other coated with Belzona 5831. 14mm dollies are bonded on with Belzona 1321, left to cure for 24 hours then pulled at a rate of 100 psi/second.
The results of these tests can be found in the table and graph below:
Adhesion Testing of Belzona 1161 and Belzona 5831
The values obtained show that the non-spark tool successfully provides a mechanical profile to achieve the necessary adhesion with two of our Belzona surface-tolerant paste and coating products. Most of the results from the adhesion testing can be described as glue or cohesive failure. Images of this testing is shown in the Appendix.
Multiple spools were prepared, one set using the rotary wire brush, the other set prepared using the non-spark tool, before then applying the Belzona SuperWrap II system. The system was left to cure according to the curing regime before conducting the hydrostatic testing.
Below is the average failure pressure from the hydrostatic tests undertaken on pipe spools prepared using both the rotary wire brush and the non-spark tool.
Hydrostatic Testing of SuperWrap II repairs
The data gathered show that the spools prepared by the non-spark tool obtained a much higher average failure pressure, almost double the failure pressure when compared with the spools prepared using the rotary wire brush.
Both tools can achieve the required level of surface preparation, however from the testing it has shown that the non-spark tool obtains the SSPC-SP11 surface preparation easier than using the rotary wire brush, plus the non-spark tool has the added benefits of the ATEX rated and certain approvals.
As we already know, manual preparation is inferior to abrasive blasting, even under the most controlled environments. However, from the results gathered, the non-spark tool that produced the surface preparation enabled the Belzona SuperWrap II system to withstand the largest amount of pressure prior to failure of a pipe spool prepared to SSPC-SP11 standard.
For the reasons stated above my recommendation would be that we can promote this equipment as a surface preparation method for Belzona products, including ISO / ASME compliant manually prepared SuperWrap II repairs.