Need a Lift?

Pratt & Whitney Canada engine plants in North America rely on hydraulic lift systems from The Marmac Co. to efficiently handle PW300 Series engines during manufacturing.

Edited By Heather Tunstall, Associate Editor Pratt & Whitney Canada engines have accumulated ½ billion flying hours - the equivalent of traveling to the sun and back more than 1,000 times.

"We currently have more than 42,000 engines in service in more than 190 countries," says Maria Mandato, a senior advisor at Pratt & Whitney Canada. "More than 9,000 aircraft operators around the globe depend on our engines to power their aircraft and helicopters." The company relies on many technologies, including large hydraulic lifts that carefully and reliably raise several hundred pounds of un-assembled engine components at a time for lengthy periods during engine manufacturing phases.

The quality of Pratt & Whitney Canada products depends on the careful assembly and construction of unique engines with their individual support systems. There are more than 10 models among the PW300 Series engines, each with its own unique configuration of technology and its supporting hardware. For example, the PW300 has an integrated propulsion system including engine, nacelle, and thrust reverser. Some of the engines have digital engine control, which include systems for monitoring engine health. Others are two-spool engines with five-stage, high-pressure compressors driven by two-stage, cooled high-pressure turbines and three-stage, low-pressure turbines driving advanced technology fans.

Moving these highly-engineered products around during their manufacture requires hydraulic lifting control that is smooth, reliable, and safe for lifting and positioning the engine assemblies. Individual engine assemblies can weigh up to 2,200 lb and often require installation of specialized components such as titanium blades, guide vanes, turbines, and digital controls.

"The lifts are used throughout the assembly process, so they can be used throughout the entire build of the engine," Mandato says. "They are part of the production build posts and are used for raising and lowering the engine assemblies at various stages of the build."

Lift Operation

During assembly and manufacturing, engines may be raised to a height of 8' and rotated 360°, depending on the needs during various stages of the builds. The lifts that Marmac provides to Pratt &Whitney Canada are freestanding lifts that include specialized versions of Marmac's patented Differential Column, which allows engine assemblers to raise and lower the engines as well as to rotate them around the vertical columns.

The Differential Column provides engineers at Pratt & Whitney Canada an alternate method of raising platforms without having to install cylinders below ground. This version of the patented lift is capable of raising and lowering loads up to 4,000 lb with the weight off-set 48" from the hydraulic lift cylinder center line through a stroke length of 5'. The lift raises and lowers at approximately 7fpm by means of hydraulic power.

Lift operators use a pendant to raise and lower the lift at their discretion. They also rotate and index the work pieces at eight equally-spaced positions about the lifting axis, allowing the lift operators to position the engines for proper assembly.

Besides lifting capabilities, floor space was also a factor considered. The Differential Column has a 36" diameter. A main reason for the compact footprint is that Marmac engineered the power unit into the lift. Hydraulic reservoirs are inside the free-standing columns and the power units are mounted at the tops, where they are all out of the way of assemblers.

Specialized Engineering

Marmac engineers modified their existing Differential Column for this application in several ways. In addition to the internal incorporation of hydraulic power units into the column, Marmac engineers designed rotational indexing and many other solutions into their finished product.

"Footprint orientation was key to the proper installation of the lift," says Marmac's Gary Walthall. "As a result, all components had to be designed with particular orientations about the cylinder axis and with respect to the mounting plate." Marmac engineers also have to take into consideration the clearance needed when lowering the engine sling assemblies to pick up the engines after the assembly. "It is necessary that the rectangular support tray for the hydraulic system be mounted on top of the column and offset from the axis of the column by the maximum possible amount parallel to the length of the tray," Walthall says.

"For the rotational requirements, we used custom bearings, which decrease rotational friction," says Marmac's Don Emerson. "In addition, the hydraulic fluid is specially formulated for this application." Although Pratt & Whitney Canada engineers specify the engine build stands with CSA-style components, the electrical circuit design is by Marmac. This design includes control functionality of the hydraulic circuit and the integrated Safety Leg.

Marmac also engineered machined "fixture attachment" areas that are adjustable.

Pratt & Whitney Canada employees use the attachment areas to attach their specific fixtures for their different engine series. Each area has multiple tapped holes, so that the fixtures can be attached at the most convenient heights for employees.

Combined, the engineering upgrades provide the capabilities of raising, lowering, and rotating the eccentric loads in the smooth and uniform manner the engine manufacturer requires. These features also enable adaptation into a stand for gas turbine engine build, pre-dressing, and packaging.

Safety Safely handling engines at every stage of production is critically important to all engine manufacturers, including Pratt & Whitney Canada. When considering the height and weight of the engines, Marmac designed numerous safety features into the lifts. For example, they attached an inverted version of their standard safety leg to each lift, which prevents the lifts from falling in the unlikely event of hydraulic pressure loss. Marmac engineers also helped Pratt & Whitney Canada achieve anti-fall requirements by applying flow-controls and a pilot-operated check valve into the custom designed hydraulic circuit.

There are also manual locks that enable engine assemblers to lock the engines in position once they have rotated them to the desired position. The joint Safety-Leg/locking mechanism allows the requested indexing by way of spring-loaded rotational locks located at the bottom of each lift.

The use of the Differential Column also requires very little oil. Consequently, manufacturers can use a much smaller motor/ pump system, which helps them meet dBA requirements for OSHA in the U.S.

The design maintains a 5:1 safety factor relative to 60,000 lb/in2 minimum ultimate material strength for all steel components.

The deflection at the top of the vertical column of the hydraulic lift with the 4,000 lb eccentric load at the top of its stroke does not exceed ¼".

Marmac Co.

Xenia, OH marmacco.com

Pratt &Whitney Canada
Longueuil, Quebec, Canada
pwc.ca