Cleaning and surface processing are important production stages in many manufacturing industries. For automotive applications, machined parts and subassemblies must be thoroughly cleaned before they move into subsequent stages of assembly or coating. Major automotive manufacturers avoid costly downtime by using industrial robotic washers from Ecoclean Inc. (Southfield, MI), equipped with Sirius 3RR monitoring relays from Siemens Industry Inc. (Alpharetta, GA).
Car and truck manufacturers as well as engine makers for those vehicles use the Ecoclean’s EcoCFlex and EcoCAgile robotic washer systems to clean powertrain, engine, and transmission parts with heated, water-based soap solutions. Cleaning cycles reach pressures of up to 10,000 psi (68.95 MPa) before parts move to assembly lines for installation. Downtime for this equipment can disrupt assembly lines, costing hundreds of thousands, if not millions, of dollars in lost production.
Early versions of the EcoCFlex Classic robotic washers were having sporadic problems heating water. That’s the job of up to two large immersion heaters located in the bottom of a tank holding as much as 1000 gal (3785 L) of water. Ecoclean uses various size heaters in its washers, drawing from 8 to 90 kW, three-phase 480 VAC. Each heater comprises several heating elements connected with a fuse and a simple on-and-off contactor to energize them. The washer tank water can take from 1.5 to 2 hours to heat, depending on the washer model’s tank size.
The challenge was to find a simple way to monitor heating elements in the Ecoclean robotic washers for any problems with excessive heating times. Due to the heaters consisting of several heating elements, the issue might have been a blown fuse or an open element pulling less current than it should. But operators were finding it hard to identify the offending element, forcing a technician to go inside the tank, drain all the water and do the needed troubleshooting and repair and refill the tank. The task could take the better part of an entire work shift, slowing down production, if not stopping it altogether.
According to Les Brumar, Ecoclean’s manager of controls engineering, the heater failures were occurring often due to damage from the coarse debris that would accumulate at the bottom of the tanks on top of the water heaters. “Our customers typically put two washers on a line,” he explained. “The first is a primary wash, which cleans a lot of large refuse, such as aluminum or cast-iron shavings, from rough broaching and drilling operations. The second provides more thorough cleaning at the end of the line, but also accumulates debris.”
While the Ecoclean washers have a pump and filter to remove suspended particle matter, heavier debris from objects like 500 lb (226.8-kg) engine blocks and cylinder heads fall through a grate to the bottom of the tank. The heavy debris is then cleared every few months as part of the washer’s maintenance schedule. “One or two workers enter an empty tank, remove the grate and shovel out the debris,” Brumar said.
“But in doing that, they can inadvertently damage the heaters. Even a small pinhole in their housings can cause trouble, so we installed shields. But, sometimes, too, a combination of soaps and oils or coolants from prior operations would create a tar-like sludge on top of the heater elements, causing excessive heat at the elements and damaging them.”
Clearly, Ecoclean needed a better indication of heater performance in their industrial washers. “Because the elements heat such a large tank of water, we initially just monitored the water temperature and when it reached the desired set point, the heaters automatically turned off,” Brumar explained. “Since we expect it would take a predetermined amount of time to heat a given volume of water, timers were the only way back then that we had to know the heaters were working properly,” he said. “But we realized we had to figure out how to alert operators to an impending heater failure, so they can manage the heating process with the other heaters inside a tank. That way, they could schedule preventive maintenance and repairs before an under-temperature situation slows down or shuts down an assembly line.”
Seeking a solution, Brumar first contacted Ecoclean’s heater supplier. They suggested that the thermocouple in each heating unit be connected to a temperature controller for monitoring. An alarm contact on the controller could then alert an EcoCFlex operator as to whether a heater was working or not. Brumar and his team tried this approach but found it didn’t work. “The problem was that the thermocouple device was mounted to only one of many elements inside each heater,” Brumar recalls. “So, while one element might be fine, others might not be, resulting in the heaters pulling less current and causing long heat-up times again. This delay would then create a bottleneck on the production line, causing customers to lose throughput.”
The solution to install a series of Simens Sirius 3RR current monitoring relays to monitor the power drawn by each heater to improve operating visibility was suggested by the local Siemens representative. “It worked,” Brumar said. “After all we had gone through to fix this issue we were elated to find a reliable way for our customers to tell if the heaters in our washers were working properly.” Ecoclean’s industrial washers are now using a three-phase standard version of the Sirius 3RR current monitoring relay. In addition to motor loads this relay can monitor multi-element heater loads and detect single element failures and alert maintenance prior to subsequent failures which lead to extensive downtime and repair. It provides a visual display for operating and diagnostic messages.
Today, Ecoclean uses the Siemens Sirius 3RR Current Monitoring Relays as standard components in all its robotic washers to keep operators informed of their unit’s water heating performance. But the big benefit of the Siemens Sirius 3RR relays goes to Ecoclean’s customers. “Now, if the Siemens 3RR relays show diminished or no amps being drawn, a plant electrician can check for blown fuses or open elements that are operating at reduced power and therefore causing long heat-up times,” Brumar explained.
Brumar noted the value that the added visibility provides: “By knowing some heaters have failed or are failing because their drawn amps are dropping, operators can then choose to nurse it along until a time when production is slack and doing maintenance and repair won’t impact the production line. That can save the plant a small fortune in lost output.”
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