Page 33 - MetalForming January 2020

Given the pump’s critical impor- tance in waterjet cutting machine oper- ation, should replacement or mainte- nance be required, it is best that it be planned, offer Kobzik and Dumas.
“A waterjet machine at an automo- tive-parts supplier may be running 24 hours/day and supporting multiple heads in robotic applications,” Kobzik says. “Should a waterjet cutting machine fail unexpectedly in such a high-production environment, costs spiral as other dependent downstream operations starve for parts. Continu- ous-flow operations in nonautomotive applications provide another example. Should a shop’s waterjet machine pump, in a continuous-flow operation, go down, all the in-process material becomes scrap until the waterjet is running again.”
In one example highlighting the ramifications of failure in a high-pro- duction environment, an automotive Tier One recently experienced a 25- minute pump failure. The seemingly minimal downtime translated to 41 worker-hours lost, ultimately made up via unscheduled weekend work.
“That’s why, as suppliers, our fab- rication customers always ask how long the pump seals will last...the impact on production can be enormous,” Dumas says.
Methods for Monitoring Pumps and Seals
Given the importance of pump-seal operation, how do fabricators monitor the life of these components?
Typically, according to Kobzik and Dumas, waterjet cutting machine oper- ators and/or maintenance personnel monitor the rate of drips coming from the seals.
“They might look at the pump every once in a while, and figure that if a seal has one drip per stroke, it’s time to change the seals,” Kobzik explains. “Or, a drop in water pressure might signal the need for replacement.”
But the pressure may not drop for long because a pump with a built-in mechanism would sense the drop in pressure, attributing it to the system
cycling too quickly.
“Sensing the ‘overcycle’ condition,
the pump would shut down,” says Dumas, “resulting in unplanned down- time.”
To avoid such fates, fabricators often decide that reaching a certain drip rate should trigger seal replacement, which allows operations to actually plan downtime and make arrangements to work around it.
But, Kobzik and Dumas caution, proactive seal replacement in such cir- cumstances can be costly.
“Even when fabricators change pump seals when reaching a one drip/stroke rate, they miss out on usable seal life, which could be as much as 40 percent,” Kobzik explains.
Be Proactive in Maintaining
Fabricators do have tools to properly maintain waterjet cutting machines and various system components. Equipment manufacturers provide spe- cific maintenance and troubleshooting tips and advice. Also available, software that monitors machine performance and various maintenance factors and schedules, and alerts users to issues. But, as Kobzik detailed to MetalForm- ing at FABTECH 2019, predicting pump and pump-seal issues can be tricky and costly. Challenges abound in main- taining waterjet machines, and in incorporating effective preventive maintenance to ensure continued reli- able performance and minimize unplanned downtime.
To provide for predictive mainte- nance, Kobzik provided a look at Hypertherm’s HyPrecision Predictive series of predictive-maintenance waterjet pumps, which the company displayed at the Chicago show. The new generation of pumps feature Hypertherm’s Advanced Intensifier technology, which includes sophisti- cated electronics providing smooth shifting for optimal cut quality and pump performance, he says. To ease servicing, the intensifier’s new design reportedly eases high-pressure end removal for seal maintenance. And, the check valve utilizes a screwless, low-
pressure poppet design that enables users to quickly evaluate key contact surfaces to speed routine servicing.
Other maintenance-helpful stan- dard features include closed-loop pro- portional pressure control that adjusts for pressure and temperature, oil vis- cosity, and hydraulic-system wear parts.
And, the pumps include color-coded junction boxes, electrical-cable har- nesses, quick-disconnect fittings, and easy-access bleed-down valves. The pump’s clear window cover lets the operator sees the intensifier and atten- uator. Also, Hypertherm’s Seal Main- tenance technology improves safety by keeping the top deck and shop floor free of oil and water, according to Hypertherm officials.
“The Predictive series provides a yellow-light signal to let users know that seals will fail in, say, the next 30 hours or so and then provides a final red-light signal of less than 1 hour before the system will go down,” Kobzik explains, noting that such signals also can be sent directly to a waterjet’s CNC. “That provides time to plan for main- tenance, but prevents early replace- ment of the seals.”
For users that require 24/7 operation of waterjet cutting machines, options abound.
“For example,” says Dumas, “one of our fabricator customers is installing three of these new pumps tied together, so that when the yellow light comes on, one of the other pumps automati- cally starts and achieves needed pres- sure, and the leaking pump will shut down—no lost production time.”
Development of the new pump arose from fabricator feedback, where waterjet cutting machine users felt challenged by serviceability and pre- ventive maintenance, according to Kobzik and Dumas.
“Whether they be automotive Tier Ones or job shops, the cost of down time in money, hours and late delivery can seriously impact fabricators,” sums up Dumas. “Anything that reduces unplanned downtime in waterjet cut- ting is a win.” MF
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MetalForming/January 2020 31
Fabrication: Waterjet Cutting