By Lance Osborne, P.E.
Know how to select the right lifting device and practice safety measures when lifting precast concrete products.
If you’ve ever tried a “one-size-fits-all” solution, you understand why people often describe it as “one size fits none.” Oversimplification leads to a solution that doesn’t work perfectly for anyone. In the precast concrete industry, everything about lifting devices is the antithesis of one size fits all. Whether you’re talking shape, size, placement or quantity, what works for one product many not work for another and, more importantly, may not be safe. Understanding the differences, how to select the proper lifting device, and how and where it needs to be installed is vital for a safe and successful lift.
Safety is the main concern with lifting anchors. It can be ensured through proper device selection, installation, engagement and rigging for the specific application. How precast is removed from the form, handled at the plant, placed in storage, placed and removed during transport, and lifted into final position are all actions that must be considered. Bob Siver, operations manager at Jefferson Concrete of Watertown, N.Y., said larger products such as custom boxes or panels require a lifting plan to be sent to the general contractor prior to installation. Wingwalls, for example, are difficult to lift due to their odd, trapezoidal shape, so proper lifting device position is important.
“Our products are heavy and you don’t want to see failures,” Siver said. “So, being ahead of the game and knowing your lifter capabilities and taking advantage of engineers’ advice and vendor tech support avoids unnecessary damage.”
Lifting device suppliers can often share expertise and make recommendations on how to install, engage and load devices through installation and rigging diagrams. Not following the supplier’s recommendations and/or failing to consider all the different loads devices and precast structures will experience during a lift may lead to cracking, spalling or an unsafe situation. Jefferson Concrete will often call a vendor for advice when the product manufactured is seldom cast. Support is readily available and responsive to questions.
“It’s easy to send an initial drawing from our CAD staff and say, ‘This is what we are proposing, are we correct?’” Siver said. “They may come back with a simple yes or recommend a better option. It’s a very good resource to use.”
Create an effective plan
Planning how precast products will be moved from place to place is the first step to consider. Thoroughly reviewing the different loads lifting anchors will experience and referring to the manufacturer will lead to a successful lift. Siver said Jefferson Concrete takes two factors into account when selecting a proper lifting device – the weight and design of the product. Weight is considered due to the plant having multiple crane options and the design determines where lifting devices are positioned. Once those are planned, the proper lifting device is selected.
“For instance, for a flat slab, the contractor does not want an exposed lifter placed right in the middle of the slab, so you have to consider what your final product will look like,” he said. “And secondly, when choosing a lifter, you have to look at the weight charts and the capability of different types of lifters.”
Next, planning proper installation of the lifting device is also extremely important. This can be rushed, overlooked or taken for granted during form setup. Quality control personnel should take extra care during pre-pour to validate that the dimensions of the form, placement of reinforcing steel, blockouts and spacers are in position and within applicable tolerances. The placement and installation control the application of lifting and handling loads on the structure.
For Jefferson Concrete, lifting device installation planning is especially important during the winter. The company can only pick up to 40,000 pounds inside the plant and it requires two cranes.
“We have to watch where we are putting our lifting devices because we need to have the capability of placing both cranes close together to make the pick,” he said. “If we have the picking devices too close together, we can’t use the cranes.”
Attaching lifting devices to the form with a void or recess member or tying them to reinforcing steel is always a wise decision. However, you must be sure you are attaching or tying the lifting device in the correct location and in the proper orientation. Proper placement of the lifting device is critical as the precast product may not hang properly from the rigging, which could cause structural damage or placement issues in the field. Misplacement of the lifting device could also create an unbalanced load and cause the lifting device to fail due to overloading. Check and double check the lifting device installation and location while making other pre-pour checks. When in doubt, consult your lifting device manufacturer.
Removing lifting inserts
Once you have cast the precast product, you need to properly remove the void or recess member from the lifting device. Some devices may have a screw-in plug or a removable half-circle recess. Proper removal of these parts from the lifting device is important as you may damage the piece or even spall the concrete where you will engage the lifting device for handling. Remember to be cautious and also consult the manufacturer for additional references as there may be specific recommendations for removal.
Double check before lifting
The condition of the lifting device is also something that should not be overlooked. The manufacturer usually has instructions and/or photographs and diagrams showing how the device should look prior to the actual lift. If it does not look correct, stop and double check the shop tickets. If the void is damaged or has spalls, the manufacturer has recommendations for proper repairs and alternate lifting methods. Taking time to ensure the lifting device is acceptable for use is critical.
When you are ready to remove the precast piece from the form or from the yard for shipment to the job site, be sure the hook or clutch fits the lifting device properly and is oriented in the correct direction for lifting. Hook and clutch engagement should not be difficult and extreme force with a hammer is a significant reason to stop. Check to ensure the engagement location is free of debris and that the hook and clutch do not have excessive wear.
Always remember if the hook and/or clutch are not in good working condition, stop and check them or get an alternate piece. Once the lifting device is exposed and secured by the hook or clutch, ensure it is oriented properly in the direction of the pull. Review the rigging to see that the lifting points are equally loaded and roll through the pulleys properly. Make sure clutch bails are not pinned from underneath to eliminate damaging the clutch, spalling the concrete around the lifting device or breaking the lifting device. All scenarios could be very dangerous.
Rigging and delivery
When the rigging is determined, sling angles and the use of pulleys should be considered. Shallow sling angles can significantly increase the load for the lifting device. A lack of pulleys can increase the load for some while not for others. Consult with rigging diagrams and configurations to ensure the load distribution is equalized. Your lifting device manufacturer can help provide these diagrams and make suggestions for each unique lifting case. Equipment availability and clearances are understandable hurdles; therefore, review all options to obtain the safest lift of the precast structure.
Delivery from the plant to the yard for short-term storage without damage is a good indicator that appropriate operator education and device application was made. However, transportation to the final destination and placement should still be reviewed. When the precast piece is hanging by the rigging while being carried to storage or final placement in the field, the condition of the travel surface also needs to be taken into consideration. Large bumps and holes need to be avoided as the hanging precast piece could bounce, creating significant impact load to the lifting devices. Impact loading during transportation needs to be minimized or eliminated to avoid overloading the device.
Siver also recommends precasters hold regular safety meetings or take advantage of National Precast Concrete Association’s live education and webinars to help new employees learn the proper use of lifting devices. He said it’s not right to assume every employee understands how to find the center of gravity on an odd-shaped product or knows where to place lifting devices.
A critical link in the chain
Lifting devices are a very important part of the process of moving precast. Checking the selection, application, installation, orientation, hook or clutch engagement, rigging and surface condition of the suspended load will help eliminate issues and product failures.
Lance Osborne, P.E., is the director of sales at Structural Technologies in Columbia, Md.