The vintage DC motor-generator set controls on a 200 ton crane at a NASA facility in Huntsville, Alabama, USA, have been replaced with a new state-of-the-art DC digital control system and cab, thanks to Atlanta Crane & Automated Handling.
It is no secret that NASA is developing a long-term Mars exploration program that charts a course for the next two decades. This facility is expected to be integral to these missions. “This visionary program will build on scientific discoveries from past missions and incorporate the lessons learned from previous mission successes and failures,” a NASA spokesman says.
It remains committed to creating additional ‘Scout’ missions, such as the Phoenix lander, which would be selected from proposals submitted by members of the science community. Such missions might involve airborne vehicles, such as airplanes or balloons, or small landers that serve as investigation platforms. This approach could open up exciting new vistas by increasing the number of Martian sites visited. The next Mars Scout is planned for launch in 2013.
NASA?is upgrading its facilities as it plans the Mars program. The upgrade of an AmClyde Inc. 200 ton stiff leg derrick crane, installed in the 1960s, is part of a larger refurbishment project at a National Aeronautics and Space Administration (NASA) facility in Alabama, where rockets and the new generation space shuttle “Aries” will be loaded onto a shake test stand to simulate the return back into the earth’s atmosphere.
There were originally two cranes on site. The other was used to load shuttle engines into a similar, albeit older, test stand, but that duty has now been moved to another location.
The crane is part of a newly refurbished building which will be used to load shuttles onto the test stand as early as later this summer. The crane is currently being used to put the finishing touches to the building itself.
NASA awarded Tennessee Valley Contractors (TVCC) the contract to install a new control building, concrete work and wiring. Atlanta Crane & Automated Handling, Inc. (ACAH) was contracted to remove the old control panels with motor-generator set controls, which made DC power for the old DC motors. They then supplied new DC digital drives to control the DC motors and controls, along with a new control panel, new cab and new controls.
The first stage of the process required the demolition of the old contact controls, which were replaced with modern technology variable frequency drives with DC controllers. ACAH has provided a similar control set-up in the past but only to the automotive sector, another unique dimension to the project.
Jeff Daugherty, ACAH’s Alabama division manager, recalled that the bidding process required about 25 visits to the site. A restricted budget meant that, despite repeated attempts from the ACAH controls engineers, NASA insisted that the motors were retained. “We urged them to replace them but they wanted them rebuilt. They only had so much money, which wasn’t flexible,” Daugherty explains. NASA also decided to re-use the existing winches.
The project itself took in excess of two years so, including the pre-contract site visits, the job has already taken three years. In context, ACAH has had a working relationship with NASA for about 20 years.
ACAH installed new 120v AC controls and new encoders on every movement for position accuracy, and tachometer feedback for speed accuracy. An Allen Bradley panel view touch screen was fitted for position and lift information, and an Allen Bradley PLC, a programmable logic control in the main control panel. It shows load, load location, boom location, boom angle as well as programmable alarms. Also included were Allen Bradley friction type joysticks with dead-man triggers.
Service manager Phillip Payne and technician Greg Lawhorn fought through “miles of wire and hundreds of terminations to complete this massive undertaking,” Dennis Bethel, ACAH president recalls.
The crane and its new controls will be put to random usage, typically operated by a single operator who will liaise via radio remote control with 6-7 spotters. That said, Bethel says there could be as many as 300 people witnessing every precise lift, so high is the profile of the work. Any time there is a lift of space flight hardware, it is considered a critical lift, requiring the presence of not only maintenance people, but subcontracted certified operators ands project engineers, says Daugherty.
“This was one of the most unusual and exciting projects that we have worked on in a long time,” says Phillip Payne. There were numerous hurdles to overcome; all the old wiring had to be ripped out from the ground floor to the top of the tower, a distance of some 450ft. New wires were labelled and pulled through the existing conduit. “Integration of the new with the old was definitely a challenge,” he says, “Thanks to Greg Lawhorn’s abilities, skills and patience the terminations were completed in a timely manner.”
When in operation, the load (a shuttle, for example) will be brought in on a platform used for hauling any high capacity products. The lift is slow and methodical with the shuttle raised at less than 7ft per minute.
The entire process, from the load leaving the transport platform to locking into the test stand takes around two hours, at which point the crane controls are turned off and NASA’s equipment takes over. The controls are switched on and the load lowered upon completion of each test.
- Atlanta Crane & Automated Handling, Inc. is a complete material handling systems integrator based in the Southeastern States. It handles projects from a few ounces to over 300 tons. It offers sales, design, and service.
