Solves Multiple Machining Challenges on 5000 Lb. Pump Housings, While Saving Cost And 50% Of The Set-up Time
Weir Minerals North America, a Madison, Wisconsin manufacturer of large pumps for mining slurry applications, needed large 108" W x 108" H pump housing Class 40 iron castings machined, including milling, drilling and boring. Each pump housing consisted of a frame and cover section, each requiring an A and B load, which meant four set-ups for a complete housing assembly. The manufacturer contacted Advanced Machine & Engineering Co. (AME) of Rockford, Illinois, as well as several other contract manufacturers, to do the machining on these parts, approximately 2-3 sets per week. Each housing sections weighed well over 5000 pounds, presenting substantial challenges for the fixturing. Rigidity was key, as well as the vibrational distortion from the enormous load and tooling masses involved.
These slurry pumps are currently used in the Athabasca tar sand fields of Alberta, Canada, for oil extraction operations. Specifically, the pumps are being utilized for flue gas desulfurization (FGD)
Although AME began delivering high-quality machined FGD pump sets on time, by using non-dedicated fixturing, set-up was taking far too long per part, resulting in much higher costs per pump set, as Steve Schubert, AME vice president of operations, explained. Changeover took as long as six to eight hours, each time. Locating and clamping the pump housings was also quite tedious and the methods used raised safety concerns, both in materials handling, strapping and clamp positioning. Clamping forces were less than optimal, which had a negative effect on the manufacturing cycle time and the tool life. AME needed to significantly reduce the total set-up and machining time, plus improve operator safety.
As Schubert further explained, "The challenge was to design a fixture that was within the weight limitations of our machine tool table, without compromising the structural integrity & rigidity of the fixture itself. Too light a fixture would yield poor finishes, dimensions out of tolerance etc. We also needed a design that would allow for quick change of the workpiece, as we did not have a 2-pallet machine. So clever swing clamps were designed to 'get out of the way' so we could remove the completed part and put a new one on. Finally but most important of all, we were extremely concerned with safety. We needed a fixture that would allow safe usage for the operator to climb onto repeatedly, as well as being secure enough to not allow one of these massive parts to fall off of the table."
The solution to this challenge was devised, as AME designed a single, dedicated AMROK® fixture, measuring 120" W x 110" H, to hold each GFD pump section for both A and B loads that reduced set-up times to less than 50% of the previous method. Additionally, due to improved locating and clamping methods, milling and drilling operations were optimized, resulting in a 45% reduction in the overall machining cycle time per pump set.
The keys to these substantial savings were the adjustable jacks built into the fixtures, which allowed proper support for the sections during the machining process on a horizontal milling machine.
These savings were shared by AME with the customer. In addition, machining quality and surface finish improved by using only one fixture, instead of multiple, separate fixtures, thus allowing tighter tolerances to be repeated and maintained more easily. Machine operator safety was also enhanced due to the standardized lifting, locating and clamping methods that were employed with this fixture design.
In the end, the customer for this application, Weir Mineral North America, was so pleased with the results that they implemented a multiple vendor reduction process and awarded the entire project to AME. Production of these massive GFD pumps improved from three units per day to five per day at Weir.
Among the many features and benefits of these pumps for the end customer:
o Size range (discharge) 24" to 40"
o Capacities to 80,000 gpm
o Heads to 105 ft
o Pressures to 125 psi
Back pull out design
o Minimum number of larger diameter fasteners allows all rotating and wearing components, including the mechanical seal, to be inspected without disturbing the suction or discharge pipework.
Modular design bearing cartridge
o Allows simple removal of the entire assembly for maintenance in a clean environment. Split release collar fitted on bearing side of the shaft sleeve making impeller removal fast and simple.
Long wear life
o Specifically designed for handling abrasive and corrosive conditions found in FGD applications, the GSL design fully utilizes Weir Minerals' long experience in solids pumping and FGD with a design built to last.
Lower corrosion in impellers
o Specially designed high chromium irons, developed in Weir Minerals' material technology laboratories, combined with optimum impeller vane designs minimize wear in pumps.
No corrosion in liners
o Natural rubber liners are corrosion proof against acidic limestone / gypsum slurries, avoiding corrosion risks which can plague metal lined pumps, particularly when low pH slurries are left within the pumps when not operating.
Long bearing and mechanical seal life
Large diameter, very stiff shaft and short impeller overhand minimizes shaft deflection and so provides excellent conditions for the mechanical seal. Fully protected oversized heavy duty oil lubricated roller and taper roller bearings carry all the radical and thrust loads with unusually high service factors.
For more information on the fixtures detailed in this application story or the other workholding and fixturing capabilities of AME, please contact:
ADVANCED MACHINE & ENGINEERING CO.
2500 Latham Street
Rockford, IL 61103
Attention: Steve Schubert, VP of Operations
Advanced Machine & Engineering Co., located in Rockford, Ill., is a global manufacturer and distributor of precision machine components, fluid power components, fixturing/workholding devices, power drawbar and spindle interface components, plus saw machines and blades. The company also designs and builds special machines for a variety of industries and provides machine rebuilding, retrofitting and contract manufacturing services. AME has partners and customers around the world and across the U.S. To learn more, visit www.ame.com.