SURVEYOR'S NOTEBOOK

A Loadout Cautionary Note

By Rik van Hemmen


As noted in an earlier blog, we love loadouts, they are a uniquely satisfying engineering exercise and often bring out the best in all participants.

Loadouts are complex projects that need to be designed and guided by experienced personnel, but even the highest level of experience cannot always prevent a mishap.

For a number of years we have been involved in the resolution of such a mishap and our involvement resulted in the discovery of a potential loadout failure mode that needs to be further disseminated in the industry to prevent a reoccurrence.

This failure mode relates to the use of SPMT’s, Self Propelled Modular Transporters. SPMT’s are brilliant tools that, almost like swiss army knives, solve a multitude of loadout problem. SPMT’s allow a load to be moved across all types of terrain and onto barges in a fashion that is almost impossible to achieve with conventional trucks or wheel sets.

Many companies have a huge amount of experience in the use of these transporters and they generally employ skilled operators who have also amassed a tremendous amount of operational skill and experience on this equipment.

These operators can move these transporters with big unwieldy loads along complex paths and over adverse terrain and do this carefully and successfully. In most cases the main objective is to keep the transporter beneath the load, and the transporter deck can be tilted to allow that to occur. As such, on solid land, a transporter may be moving along a transverse incline, but the load sits upright on the transporter deck. This makes sense, and is an almost reflective behavior for an SPMT operator.

But once the transporter moves onto a floating barge, reality changes rather dramatically. The transporter is no longer on solid land and, instead, the barge will respond to the transporter load. This can induce a heel or list on the barge. These small heel or list excursions are normal, and help in centering the load. (It is imperative that these heel angles stay well below the tipping point of the transporter and load though) However, aboard a barge, the platform tilt feature is not helpful in keeping the load above the transporter. There is only one way to obtain an even load, and that is to carefully drive the transporter to the high side of the barge to reachieve even heel.

Tilting the transporter deck to maintain a load at horizontal when there is a heel excursion on a barge has a number of negative consequences such as:

  1. 1. Loss of situational awareness (driving a transporter with a tilted deck makes it impossible to establishes the proper location of the transporter on the barge with regard to the centerline).
  2. 2. The tilt feature allows much more rapid lateral center of gravity shifts than simply driving the transporter side to side. And fast cargo movements on a barge are undesirable.
  3. 3. In certain cases tilting the load towards the high side of the barge can even result in increased list towards the low side.
  4. 4. The operation of the platform tilt feature actually increases the risk of equipment malfunction and thereby increases failure risks in the system.
  5. 5. The interaction between tilt valve engagement and hydraulic gauge readouts is different on a barge than it is ashore, since a barge takes time to respond to load shifts, while terra firma should not. This can result in operational confusion.

During the loadout kick off meeting is important that the SPMT operators are specifically instructed not to engage the platform tilt feature while on the barge unless everybody agrees there needs to be a specific platform tilt. This is more difficult than may be expected, since SPMT operators almost reflexively make tilt adjustments when they drive an SPMT. Therefore prior to, or during the barge move another reminder may be required.

Bottom Line: Ashore, it makes sense to keep the transporter deck parallel to the horizon. On a barge, it only makes sense to keep the transporter deck parallel to the barge deck unless the load out team has a specific reason to engage the platform tilting feature.

Let’s be safe; spread the word: No SPMT platform tilting on the barge.  

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Photo caption: Transporter to barge move that was successfully completed.