On 30 April 1998 Dutch heavy lifting specialist Van Seumeren decided it needed a heavy lifting platform ringer crane that could be disassembled and transported in standard sized containers. The reason: deadly rival Mammoet looked to have stolen a lead with its MSG-50 Mammoet Sliding Gantry (Serious lifting Jun98, p25).
The MSG-50 lifts 3,000t and is specially designed to be packed into standard-sized containers for transportation. The logistics of getting such a big piece of kit to sites around the world are key to submitting the lowest bid for a contract.
Van Seumeren set about designing its new crane immediately and engaged neighbouring engineering company Huisman Itrec to build it.
By 12 February 1999 the Platform Twinring Containerised (PTC) crane was not only built, but had been fully tested and was ready to be shipped to its first project. On 15 March the PTC starts on site near Edmonton, Canada placing reactor vessels at a Shell MEG petrochemical works.
The PTC then has another project in Canada and has more than 12 months of lifting contracts booked in North America, where it can be transported by railway with relative ease.
With a basic capacity of 1,600t and a maximum capacity of 2,000t, the PTC does not lift as much as Mammoet’s MSG, but it claims other benefits.
It can lift 1,600t with 1,500t of counterweight on the ring, thus giving a small tailswing. With 960t of floating counterweight, or superlift, the capacity is still 1,600t and the lifting chart remains the same but less counterweight needs to be transported. There is, though, a tailswing of 24m radius. Maximum capacity of 2,000t is achieved with 800t floating counterweight and 300t on the crane.
On longer booms, configured with its 180m luffing jib, the PTC will outlift the ostensibly stronger MSG, Van Seumeren claims. The luffing jib is needed for the second job so Huisman Itrec has only now started building it.
But the chart is not what makes the PTC different from other platform mounted or twin boomed cranes in Van Seumeren’s rapidly expanding heavy lift fleet. It is its transportability. The whole crane can be stowed away into 88 containers, including elements for boom and ballast. For its first trip, where it is going with 100m of main boom and 960t of counterweight, the whole crane will be packed into 72 containers: 42 of 20ft length and 30 of 40ft length.
In fact, the MSG requires significantly fewer containers to transport it, as no counterweight is transported. Counterweight is created by filling the containers in which the system is transported with locally sourced ballast, such as sand or water.
Van Seumeren’s approach is to design counterweight sections that form part of the container. A boom section with a slim piece of counterweight fixed at each end creates a container unit of 30.4t.
This means that though transportation costs may be higher for Van Seumeren, it can claim the advantage of speed over the MSG. Maarten de Graaf, Van Seumeren’s project manager for platform ringer cranes, says that it takes six men five days to unpack the PTC and assemble it.
Van Seumeren’s greatest claim for the PTC over the MSG is not so much speed of assembly, though, but speed of operation. As de Graaf points out, the MSG is not a crane at all, but a slewing strand jacking system and so can take eight to 10 hours to make a lift.
In contrast the PTC has two hoist winches, each with 1,450m of wire rope with a line pull of 60t on each. A runner to go on top has a 50t capacity. The line speed of the hoist for the runner is 80m/min. The line speed of the big hoist is 27m/min. The PTC turns 360O in eight minutes.
Ultimately, the MSG is unquestionably the stronger of the two lifting machines. By using a double or triple boom lifting capacities can be increased quite simply to 4,000t, even 10,000t. But Van Seumeren offers versatility. As well as making the one big lift that made it worthwhile shipping it over for, the PTC can also quite practically make other smaller lifts around the site for which the MSG would be too slow.
Van Seumeren also makes the point that a rope wrapped around a drum, as on the PTC, suffers less wear and tear than a rope that is being clamped in jacking, as on the MSG.
According to De Graaf, the PTC is clearly the best thing Van Seumeren has ever produced.
And such is the company’s faith in the design, it plans to build one a year for the next four years, to have a fleet of five PTCs.
