Heraeus Assists Metsa to Improve Output, Quality and Reduce Operating Costs
“What is really important to METSA is to have the peace of mind that we build stellar products. Great attention to detail is given in selecting the best materials and equipment to ensure the best quality and design for each of our tanks. Heraeus was an instrumental partner in setting up our revolutionary and automated paint line. We look forward to working with them on other projects.”
The CEO of Metsa, Humberto Garza
LPG Cylinder Powder Coating Case Study. Propane tank manufacturer Metsa, is a family-owned and operated propane tank manufacturing company. For more than 50 years, they have been involved in the sale and distribution of propane tanks, so Heraeus completely understands the high level of quality and specifications required on every pressure vessel. Increased Sales, Insufficient Space and the need for Quality Improvements Due to US expansion, the company was running out of room in the powder coating department at a time when sales were increasing. The existing process required hand applied powder coatings that were cured using a propane powered, batch convection oven system. Unfortunately, this oven was only partially curing the larger tanks due to uneven air flow which caused large temperature differentials from top to bottom of the tanks. The problem occurred especially around the heavier collars and angular support feet. Potentially, this could lead to quality issues in shipments, poor resistance to sunlight and even color variances. With the increased level of business and competition, shorter lead times were being demanded by distributors along with a marked increase in output and overall quality improvements of the cured coating.
Change from Batch to In-Line Powder Coating
The decision was made to change the batch process into an in-line system. Space was at a premium, and with a required line speed of .75 – 1 m/min, depending on product size, the oven length was a major factor in the decision making process. Testing was initiated at the Heraeus plant in Buford GA. and it was quickly determined from testing of full scale 115 kg tanks, that a dwell time of 15 mins would be required for the catalytic IR oven and small tanks would cure in 10 mins. A 10m IR oven was designed to meet the line speed requirement and an overhead conveyor was installed. The existing powder booth was re-configured to fit the in-line system.
Process Benefits of the new line
The use and control of the 10 zones along the length of the oven permitted precise temperature control from the bottom to the top of the oven as well as from entrance to exit. This exceptional level of zone control allows extra intensity to be applied at the bottom of the tanks where the extra angular metal feet are located. This completely eliminated the under cured and over baked areas Due to the fact that the longwave IR is emitted in a half hemisphere – (see diagram), there are many waves of IR radiating from the panel from the multitude of catalytic reaction sites. The ray trace shows the radiation from a group of heaters (see diagram), ensures an even distribution of radiation that encapsulates the entire tank. Additional benefits that ensured an 18 month return on investment. Besides achieving an evenly, well cured powder coating, there were a number of additional benefits that have been realized since production started:
- By switching to Natural Gas from Propane, the monthly operating costs dropped from $4,000 to $1,000.
- Faster cycle times over the batch process reduced not only operating costs but production volume has increased with no increase in labor overheads.
- Maintenance costs were substantially reduced – there was a constant maintenance factor on the old burner system and cleaning the batch oven to stop powder contamination from one batch to the next.
- Faster cool down time – because IR heats the coating, the entire tank does not have to reach the cure temperature. This allows for reduced dwell time in the IR oven and ensures that the tanks cool much more quickly than the old process.
- With the faster cool down, external fittings could be added to the tank while it was still on the production line. Previously the tanks were moved outside as they took so long to cool down.
- Reject rates have been significantly reduced, which frees up the blasting/cleaning system from processing the quality rejects.
All of these gains permitted a ROI of less than 18 months on the oven and line upgrade costs.