One of the most visually captivating activities in the heavy manufacturing industries involves the use of bridge cranes. Watching these cranes operate is intriguing—not just for their sheer power, but because of their potential for damage. Slips, bumps, and drops can cause costly disruptions and inflict irreparable damage to equipment, infrastructure, and personnel.
At the center of this crossroad of brute force and precise control is Trutegra, a Charlotte, N.C.-based developer and integrator of control and automation systems for bridge cranes.
Trutegra develops bridge crane control systems for many of the large metal fabrication and treatment plants that supply the auto industry with high-strength steel for stamping into auto body parts. Referencing one such client facility in this industry, Mike Martin, Trutegra’s information technology manager, says this plant uses four giant bridge cranes. The bridge for each crane in this facility spans 120 feet, while running overhead on two rails that are 2,000-feet long. This particular plant specializes in the continuous annealing and galvanizing of thin steel sheeting, which gets rolled into coils weighing up to 40 tons for shipping.
Though most bridge cranes of this type are now fully automatic, there are many older models still in operation that are manual or semi-automatic. Manual controlled cranes can be operated from an onboard operator cabin or remotely from a control room via video cameras. “But no matter what their operating mode, real-time communications between the operator and the crane’s components is vital to their efficient, safe operation,” Martin says. “That’s what prompted this particular customer to call us for help.”
For years this customer’s bridge cranes had been using 900 MHz leaky coax cable communications that ran along the rails to guide the bridge and trolley. A plan to put cameras on the cranes to better see their operation from a remote control room, while also recording to a DVR in case of mishaps, was one of the reasons the company sought to upgrade its wireless system. The company also wanted to collect operational data from the cranes, which couldn’t be done with the leaky coax. For these reasons, the crane’s wireless bandwidth needed to be increased.
The company determined that it was best to upgrade the facility to 802.11n wireless broadband to handle its plan for camera additions and data collection. And though 802.11n wireless is capable of handling the applications the client wanted, the wireless solution provided by the initial vendor on the project was not up to the task.
“The crane’s vehicles would lose communication long enough that it would stop production eight to twelve times per shift,” Martin says. “When these outages occurred, they’d have to send someone out there with a belly box remote control, and manually drive the crane to a maintenance location. They’d then shut off the crane’s power and reboot it so that the radio would come back on. These disruptions probably cost the plant hundreds of thousands of dollars in lost productivity.”
To correct the problem, Trutegra recommended an industrial 802.11n wireless LAN comprised of Siemens Scalance W788 access points and W748 client modules.
Martin says Trutegra prefers the Siemens Scalance W family of wireless products because of their solid-state reliability, security, and their ruggedized aluminum housing that makes them well-suited for industrial applications. Using MIMO (multiple-input, multiple-output) technology to multiply the capacity of their radio channels, the Scalance W wireless products can achieve bandwidth throughputs of up to 450 Mbit/s—more than enough for this customer’s requirements.
After the customer’s previous wireless upgrade experience, Trutegra wanted to prove that the Siemens Scalance W wireless LAN products would work. To do this, Trutegra designed a redundant system for one of the plant’s cranes, placing one Scalance W788 access point high on the wall at each end of the plant’s building. Connected via Ethernet cabling and powered via Power over Ethernet, these access points communicate via Profinet back to the plant’s SCADA (supervisory control and data acquisition) system and also bring video signals to the control room and DVR. The crane’s vehicle control box was outfitted with a Scalance W748 client module.
Martin says this particular installation took about eight hours to mount the units, hook them up to the network, and tune everything. Trutegra set the units to their highest security encryption.
Since the installation, Martin says this customer has “not had a single outage,” saving them the “hundreds of thousands of dollars in productivity they were losing with their previous wireless system. And they don’t have the safety issue of putting a person out on the floor 12 times a shift to manually drive the crane to its maintenance position and reboot it.”
The implementation was successful enough that the customer decided to upgrade the three other cranes at this facility to the Siemens Scalance W system, as well as five more cranes in another location.
Plus, after having seen the simple installation requirements involved in the initial installation, the company had its own plant personnel handle the subsequent installations.
“We documented the installation steps for them and their own staff took care of installing the units, connecting them to the network and setting them up,” says Martin.