During the operation of construction machinery, rollovers happen from time to time for various reasons.

We will not discuss safe operation practices or insurance claims here — this is a focused discussion on restorative handling of machines after a rollover.

Whether small machines of a few tonnes or huge units of several hundred tonnes, any machine can suffer a rollover. In my past work for state construction units and while with a CAT dealer, I handled many rollover incidents involving many types of equipment — non-highway trucks, rollers, motor graders, excavators, bulldozers, truck cranes, and so on.

After a rollover, the best course of action is to right the machine and restore it to its correct position as soon as possible. However, due to site constraints, lack of lifting equipment, limited experience, or poor rescue organization, machines are sometimes left overturned for hours or even days before being righted.

Construction machinery is complex. In a rollover there are often obvious damages — bending, breakage, deformation — but there are also hidden problems that are not visually obvious. If these latent issues are not eliminated promptly, they can cause secondary failures and much larger losses. This deserves careful attention.

Common problems after a rollover include:

1. Structural member deformation, breakage, or cracking.

2. Bent or damaged tubes and pipe components, with loss of hydraulic fluid, fuel, or lubricating oil.

3. Failure of components that must not be inverted or placed on their side (for example, batteries and coolers) due to positional change.

4. Deformation and twisting of the cab, sheet-metal covers, and their mounts.

5. Stress damage, twisting, or deformation of housings and gearbox cases.

6. Damage to radiators, oil coolers and similar heat-exchange components.

7. Impact damage or catastrophic failure of the slewing (turntable) bearing or swing bearing.

8. Damage caused when engines that were not shut down were briefly run while the machine was overturned.

9. Damage to other external accessories (for example, filter assemblies).

Except for items 7 and 8, most of these issues can be detected by visual inspection. Items 7 (slewing bearing impact failure) and 8 (engine damage from running while inverted) are not directly visible and — if not identified and dealt with promptly — can seriously compromise future machine operation.

Modern internal-combustion engines are engineered to the limits of material performance to achieve maximum machine capability. You no longer see the old, heavy low-power engines (such as the vintage engine that weighed 1,400 kg for 100 hp). Because of this, certain components in today’s machines are more vulnerable in a rollover.

I have handled rollovers many times. When a machine has been overturned for more than an hour, no matter how inconvenient, I require the on-site technicians to carefully remove any fuel and lubricating oil that has entered the engine cylinders, following the direction in which the machine tipped. This prevents a condition where incompressible liquid inside a cylinder (a hydrolock) can cause severe damage to pistons and the crank-connecting-rod assembly when the engine is cranked.

On several engine models I’ve seen repeated cases where liquid hydrolock bent connecting rods. The result can be loss of cylinder compression, heavy white smoke on cold start, and poor cylinder output — faults that can be diagnosed by isolating cylinders but cannot be fixed by merely swapping fuel system parts.

During teardown investigations I have encountered connecting rods bent severely enough to damage cylinder liners or even the engine block. In some older engine designs with very robust crank-connecting-rod assemblies, rods may not bend, but after rollover the engine still will not start — when turned by hand you may find one piston cannot pass top dead center because of trapped liquid. This, too, is caused by liquid in the combustion chamber.

Therefore, when handling a rollover you must carefully analyze the accident characteristics and potential hidden hazards. Do not be casual about it.

Critical warning: Do not start the engine until a senior service technician has inspected the machine and confirmed it is safe to do so.