Cargotec-HIAB, Sweden

Suspended parts with greasy surface and blasting system

At an international manufacturer of material handling equipment and mobile lifting equipment, load-bearing components are made of canted and welded sheet metal structures. The company can pre-fabricate a large part of these modules in various works, including in several Eastern European countries. Despite uniform requirements for production and for the use of auxiliaries, such as cooling lubricants, cutting oils, release sprays, anti-corrosion oils, etc., the modules reach the finishing line with a much different level of quality in terms of cleanliness of the parts:
From virtually grease-free, up to dripping with oil and greasy.

Finally, these components must all receive a high-quality anticorrosive coating. For this purpose, the components are introduced into a fully linked production facility. In the first step the steel surfaces are peened in an overhead rail, continuous flow blasting system with 16 blasting wheels. As blasting media, high carbon round grain is used (S330). With the previous working method, no integrated pre-cleaning had been installed.

Oils and greases could accumulate in the blasting media. Depending on the soiling level of the components, the contamination of the blasting media was sometimes more and sometimes less prominent. This had the result that initially the filters had clogged up rapidly owing to the sticky blasting dust and that at the same time the cleaning performance of the two air separators had continuously subsided. The head of the surface finish department, Ola Jonsson, reports: : “The composition of the operating mixture changed gradually towards a grain size that was too small. Thus, the material removal rate and removal efficiency of the blasting system was reduced dramatically. The desired rough depth of at least 30 microns and the blasting degree SA 2.5 of the peened surfaces were not achievable anymore. Moreover, owing to the carryover of the oil, the blasting dust adhering to it was also introduced into the subsequent preparation processes and coating processes. This also led to problems there, for example frequent wetting problems already during primer application.”

Therefore, one was faced with the decision to invest in a pre-washing unit in order to bring the input conditions of the components to a consistently low level.

Within the scope of a service order, the manufacturer of a new additive, PantaTec GmbH, has examined the initial process conditions and documented them in order to be able to compare them later on directly with the improved process results.

First addition of additive to the separator for vaccination of the blasting process
Water repellant test and test ink on blasted surface clearly show contamination with oil

Jonsson goes on to elaborate: “Through the simple addition of the additive ULTIMATE directly in the blasting media, we could remove the strong contaminations from oil and grease practically completely from the process within 8 operating hours. Despite this, we have still continued to introduce very oily components into the blasting system. As process control, in addition to the test with test dye on the peened surfaces, we constantly repeated the water repellant test on the blasting media. This test shows the wettability of metal surfaces of the blasting media with ordinary tap water. Through the cleaning effect of the additive, we could reduce the permeation time with the water repellant test from 5 minutes to 20 seconds and stabilise it.”

Surface blasted with additive, test ink and wetting significantly better

“Our objective was the achievement of wettability with water-based coating materials. Our subsequent processes would thereby not be needlessly contaminated anymore with oils and greases and, even more importantly for process stability, not with large fluctuations. If successful, we wanted to save on the investment in a costly pre-washing unit” explained Jonsson. Checking the surfaces in terms of spray pattern, roughness and not least, the surface tension, values were stable throughout in the range of more than 40 mN/m. With appropriate adjustment of the blasting coverage and intensity, continuous values of 44 mN/m are achieved. These are surfaces that are even directly coatable.

Automatic dosing mixer maintains a constant operating point

As a final measure, the operating point for continuous operation of the blasting system has been identified and secured in the application. The aim was to determine the required addition levels of the additive and the pace of addition. With its high quality standards, process reliability is clearly in the forefront with HIAB. Now, due to the operating point selected, the blasting system is always able to handle the maximum expected contamination and to supply a definite reproducible blasting result. The task of observing the operating point has meanwhile been taken over by an automatic dosing unit. HIAB has achieved the desired process reliability in a simple and economical manner and, therefore, is very happy with the results of the PantaTec method.