Design-Construction

Introduction

One thing often ignored by designers is: material handling. Figure 1 below is picture sent by my friend Rendra. It shows beams which were being transported by trailer truck. What’s wrong in Figure 1?

Fig. 1. Structural beams transported by trailer truck.

The Forgotten Padeye

Besides being poorly secured to the trailer body, the beams have no padeye at all. Padeye, or sometimes called lifting lug, is a plate with hole attached to a structure, into which you can insert shackle or hook when you need to lift the structure. Figure 2 shows a padeye on undercarriage of Komatsu PC 2000 mining excavator. Figure 3 is a little bit different lifting lug integrated into the ribs in the superstructure of Terex RH 30-F mining excavator.

Fig. 2. Padeye on undercarriage of Komatsu PC 2000 mining excavator.

Fig. 3. Lifting lugs integrated into ribs of Terex RH 30-F superstructure.

Transportation of Structures

Some designers only focus on what the structure does after it is constructed and ignore the other processes: fabrication, transportation and installation. Why padeye is very important? When we put padeyes into the design, we make sure the padeyes are welded to the part of structure which is strong and rigid enough so it will not deform or buckle when we lift the structure. We also make sure the padeye itself is strong enough to hold the pull force from the lifting hook or shackle. In this way, we can guarantee the safety during transportation and installation of the structures. We don’t want the structure collapse during lifting and squeeze someone to death.

What happen if the structures don’t have any padeye? We cannot expect the truck driver or the crane operator to have deegree in engineering. They will just lift the beams by any means they think OK and as fast as possible so they can go home earlier after work.

In the process, they probably attached hook or sling to parts of the structure which are not properly reinforced and have no strength at all. If you take a good look at Figure 1, you can see some plates are bent and permanently deformed due to mishandling. Can you imagine how pissed off the people in construction site who will receive the deformed beams? In workshop, with good collection of tools, you can fix the deformed beams. But in construction site, fixing that small deformed part is not easy due to limited tools. This costs extra time and delay in schedule.

Installation of Structures

When we install those beams, which serve as columns, we will need to erect them first. Most probably with crane. If the beams have no padeyes, the construction engineers will get creative and improvise by welding some plates or bars onto the beams as emergency padeye while they erect the beams. This will hurt the coating a bit. But even worse is: there is no strength calculation and safety measure. Who can guarantee the emergency padeye has sufficient strength and proper welding? Things always can go wrong and shit always happens

Never Forget the Padeye

Figure 4 shows the padeyes of LIMOV STM-50T mainframe during sand-blasting. You know we at LIMOV care for details and safety . If we provide some simple padeyes, the crane operator or construction engineer will easily spot them and understand that he should bolt the shackle into the padeye. This makes his job easier, faster and safer. It also keeps the structure in good condition. No buckled plates and scratched coating.

Fig. 4. Padeyes on mainframe of LIMOV STM-50T.

So, when you design something heavy, always pay attention to how it will be transported and installed. Never forget to put padeyes onto it. If you are not the designer, warn them when you see the padeye is forgotten. I wish you safe and reliable works always.

** End of Article **