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Converted Recycling Process Improves Sealing Productivity

Honeywell’s diecasting impregnation sequence underwent a quick revamp, achieving considerable savings in operating costs and a significant increase in throughput

Honeywell is a highly visible brand of commercial and consumer products, a name that fronts a variety of industrial and manufacturing programs, including diecasting: for decades, Honeywell Environmental and Combustion Controls NA has operated an aluminum diecasting operation in Dublin, CA, producing combustion control valves on eight diecasting (500-900 ton) machines. The same location includes all the necessary finishing and machining operations, too, and supplies 100% of Honeywell’s diecasting requirements.

The group has championed a “vertical integration” approach to manufacturing for many years, as well as a corporate focus on improving productivity and efficiency, reducing operating costs and inefficient use of resources.

All of these objectives were relevant in the effort to improve the impregnation process that follows diecasting, to seal any pores or fissures that develop on the surface of the part and may negatively affect the functionality of a valve.

Morray Ysaguirre, the Honeywell division’s principal manufacturing engineer, is responsible for six machining work centers and the impregnation system. For over 18 years, the plant has used an automated impregnation system to process more than 2,000 castings per day. According to Ysaguirre, the impregnation process had two consistent problems: the products from the process displayed some “stickiness,” indicating excess sealant residue remained on the parts’ surface; and the plant endured high environmental costs as a result of the impregnation process.

Ysaguirre contacted Ultraseal Intl. to assess the system and recommend improvements.

Situational Analysis — Analyzing the manufacturing system data, the Ultraseal America team found the impregnation system was consuming about 200 gallons of sealant per month and 1,000 gallons of water per day on the wash tank. Due to discharge restrictions, the contaminated process water was treated on site, then filtered. An evaporation system also was required, adding an additional effluent treatment cost of $0.21 per gallon of process water.

In addition to the high volumes of water and sealant usage,
Ultraseal engineers concluded that the excess sealant on the castings meant that Honeywell had to use even more fresh water in the tanks for cleaning, which increased process downtime and reduced productivity— capable of processing five carriers per shift.

This is the general outline of a casting impregnation system: First, sealant is applied to the casting under vacuum in an autoclave. Once components are immersed in sealant the vacuum is released, so that the sealant is drawn into any microporosities and leak paths thanks to the resultant change in pressure. Applying the sealant to the casting can take as little as 30 seconds to two minutes for components like engine blocks, or up to 30 minutes for compressor parts.

Second, a cold wash module removes excess sealant from component surfaces and tapped holes.

The third stage is a hot-cure cycle, exposing components to heat for a predetermined time using a hot water bath, which polymerizes the sealant so that it changes from liquid to solid.

Both the cold wash and hot cure stages produce an effluent stream. During the cold wash stage with conventional, non-recycling sealants, up to 90% of the sealant consumed is lost to effluent, which is a chemical pollutant that must be disposed of according to local environmental regulation. After a few cycles the washwater also must be replaced to prevent unwanted sealant contamination of components. The emulsified wash water cannot be discharged and requires disposal by a specialized waste-management process.  This is the cause of wasteful process water and sealant consumption (as at Honeywell) and associated environmental treatment and disposal costs (as at Honeywell prior to the process update.)

Proposed and Resolved — Following a full system review and assessment, Ultraseal America recommended converting the conventional impregnation system to the Ultraseal Sealant Recovery System (SRS) and using Ultraseal Rexeal 100 recycling sealant. Now, Honeywell’s system is fully closed-loop on the cold-wash operation and requires no changes in the application of the impregnation process. The new sealant offers a faster gel time and better process stability than the previously used sealant.

Converting to the Ultraseal technology was achieved by adding the SRS module and modifying two of the wash-and-cure tanks to meet more modern specifications and improve component washing, eliminating the previous post impregnation problems with “sticky” components. This meant Honeywell could also eliminate one of its three wash tanks which reduced the time required for processing.

Ultraseal engineers were able to reuse most of Honeywell’s existing equipment in the system conversion, and also updated the programs in the PLC and CNC controllers. The PLC updates led to much faster processing cycle times, made possible by the new sealant. The conversion work was completed within a two weeks.

The SRS technology provides cost-effective processing while avoiding process-chemical effluent treatment costs, and it eliminates solids disposal, reducing the associated evaporation costs.

Since implementing the system in 2016, Honeywell has recorded significant cost savings, productivity improvements and environmental benefits, including:
• A 98% reduction in water consumption, saving $172,000 per year;
• A 93% reduction in sealant consumption;
• Reduced cycle times (from 110 to 40 min./carrier, increasing from five to nine carriers/shift) and 37% lower processing costs.
• Increase in process productivity, allowing for elimination of two shifts and redeployment of operators elsewhere on site, saving of $100,000 per year.
• Eliminated off-line wastewater-treatment costs, saving $70,000 annually.
• Also, because the system no longer has sealant building up on process tanks, $16,000/year is saved by eliminating biannual cleaning via an outside contractor.

Overall, conversion to Ultraseal recycling technology delivered Honeywell consolidated cost savings of $19,000 per month, and significantly improving productivity and environmental performance.

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