The huge Chicago Bridge & Iron (CB&I) Island Park fabrication shop in Beaumont, TX, specializes in large-scale process modules, shop-built vessels, and large steel plate subassemblies. Nonetheless, this job was a little bit like building a ship in a bottle and then having to remove the ship from the bottle.
CB&I workers had built a massive petrochemical process module weighing almost 200 tons. The completed module was so large that insufficient headroom precluded using the facility’s bridge cranes to lift it onto a transporter.
Digitally Controlled Hydraulics Solve the Problem
The CB&I staff aren’t like the cartoon guy who sits on a limb he is sawing off. They already knew there would be enough headroom to lift the module the four feet or so needed to crib it and roll a transporter underneath. The question was how best to lift it, and lift it uniformly.
Lifting by hydraulic jacks would certainly be required, so the module was fitted with six I-beam stringers that were reinforced with gussets and bolted to the main frame of the module so as to project on each side. This resulted in 12 lift points, one at each end of each stringer beam. Twelve 25-ton jacks were placed, providing an ample margin of capacity.
Controlling the lifting process manually would have meant using a lot of reliable people to individually control each jack. It would also have meant a lot of radio chatter among the jack operators, since none of the lift points was visible from all the other points. There would be a lot of possibilities for confusion and error, raising concerns about safety and the possibility of damage to the module.
The solution lay in a combination of traditional hydraulics with a digital controller, sensors, and actuators — "synchronized lifting." In the Enerpac Integrated Solutions sync-lift system deployed by CB&I, a PLC controller monitored load position at each lift point to within a millimeter (0.040 in.) by means of a cylinder displacement sensor associated with each jack.
The position sensors, with mechanical construction analogous to that of a tape measure, unwind a fine wire from a spool to a fixed reference point. Rotation of the spool is monitored with high angular resolution, and the resulting signal goes to the digital controller, which operates solenoid valves at each jack as needed.
Additionally, the controller accurately sensed the load at each jack, in essence providing a load cell at each lift point. The controller’s touch screen gave the operator position readouts and also load readouts (by point and total). The digitally controlled hydraulics afforded significant advantages to CB&I:
- Increased safety — The digital controller eliminated the possibilities for confusion and error inherent in a multi-operator manual control approach. This is particularly significant if an unexpected event occurs, such as a load shift, and the controller also had warning and stop capabilities
- Increased productivity — Considerably less staffing is required than for a manually controlled lift. The actual raising process can also proceed more rapidly because the status of every lift point is constantly displayed.
- Less chance of property damage — With all lift points constantly monitored and automatically controlled, concerns about overstressing some part of the module due to uneven lifting were eliminated.
The four-foot lift was accomplished with no problems. CB&I had selected 12-inch stroke cylinders as the most versatile considering other, future applications for the sync-lift system, so this lift was done in approximately one-foot increments using cribbing. With the hardware and factory-provided training for synchronized lifting in hand, CB&I expects to be using the system regularly.
Pete Crisci is the Americas Business Leader for Integrated Solutions (www.Enerpac.com)