Posted at Tuesday, 16 June, 2020

Is this a wind up? No, it's a serious request

Paul Skade
By Mahesh Patel
Engineering Manager

During my years with WYKO and ERIKS, I have gained extensive experience and knowledge which has enabled me to maximise my present role as Engineering Manager work...

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Coiling 325 tons of coated piping onto a giant reel is a massive wind-up. But when a customer asked ERIKS to upgrade the machinery involved, with no existing engineering drawings and in under six months, it wasn’t a wind-up at all. It was a serious request.

 

The giant reels in question are moved from side-to-side on rails as newly-coated piping is coiled onto them, to ensure its even distribution. The movement requires traverse rim drive carriages and idler bogies running on the rails to transport the reels. Then once full, the reels are lifted by crane and loaded onto lorries, for delivery to cargo ships and transfer to offshore oil and gas rigs.

Originally the reels held 250 tonnes of piping, but the customer decided to increase this to 325 tonnes each reel, to allow a reduction in connections required for any given length of pipe. Because the pipes are used to transfer oil and waste from offshore rigs to land, that length can be substantial. So manufacturing longer pipe lengths means the efficiency increases and cost reductions can be substantial too.

 

The predicted benefits were more than enough to justify a £2.1m investment in a new, larger crane to lift the heavier reels. However the customer initially thought that the existing carriages and bogies would be able to cope with the 30% weight increase. It was only with less than six months to go before installation of the crane that they began to wonder if that really would be the case.

That was when they contacted ERIKS.

Weighing-up the odds

The customer’s current set-up of driven carriages and bogies had functioned perfectly well for around 15 years. Their worry was that the additional weight would cause a critical failure and prolonged downtime, potentially hard on the heels of the planned shutdown for installation of the crane.

Unfortunately engineering drawings of the set-up were unavailable, so understanding its design and construction, and calculating the effect of the increase in weight, had to be done from scratch, based on what was visible or accessible on site and what could be physically measured. The only figures the customer could provide were the weight of the new reels and the resulting load on each carriage wheel (450kN).

Based on the figures provided and measurements taken on site, ERIKS engineers made a number of calculations [see workings at end]. They could then advise the customer of the redesign required to ensure the carriages would continue to cope.

Modifying the existing carriages was considered, but ERIKS’ calculations proved it wouldn’t be cost-effective. The alternative, of installing new carriages, would allow phased production shutdowns over a week, rather than a complete shutdown for 4-5 weeks for modifications.

Simple, but effective

As well as the redesign to cope with the increased tonnage, ERIKS’ engineers took the opportunity to simplify the set-up.

The reduction gearbox which had previously split through two propshafts was eliminated from the new design, and replaced by individual drives and gearboxes for the driven wheels.

This means less engineering complexity, a lower component count, a potential reduction in mechanical wear, and an increase in overall efficiency. At the same time, the redesigned set-up is predicted to deliver a similar service life to the original, with no maintenance for the first three years of operation.

 

Lubrication of the original gearboxes required a technician to crawl underneath the equipment, with associated health and safety risks. ERIKS took the opportunity to incorporate additional piping into the new design, and the customer is currently considering connecting a lubrication system to these pipes.

With a £1.2m crane waiting in the wings, there was no room for manoeuvre around the deadline. To make sure they could meet it, ERIKS dedicated an entire engineering workshop to the manufacture of the new traverser rim drive. Despite the complete lack of engineering drawings, from initial customer approach to on-time delivery and commissioning took only a matter of months. And the drives were installed at the same time as the new crane: meaning only one shutdown and minimum loss of production for the customer.

So what could have been a wind-up was ultimately a “reel” success.

Showing our workings

Existing drive set-up

  • Primary Drive – 4.0 kW, 4 pole motor into a 7/1 gearbox. Output split via prop shafts into a secondary planetary gearbox meshing with a 68-tooth wheel, bolted to a flanged driven wheel.
  • It can be assumed power and speed at each driven wheel are approximately 1.0kw at 2.25rpm, producing an approximate torque (minus inefficiencies) of 4240Nm – providing the load is shared equally between the pairs of driven wheels at each end.

 

ERIKS’ redesign

  • The load on the carriage is to be increased by 30%, from 250 tons to 325 tons. The customer advised that 450kN (unfactored) would be acting on each of the 8 wheels (4 driven, 4 idlers).
  • It can be assumed a proportional 30% increase to existing primary drive power of 4.0kW would require an additional 1.2kW, resulting in a total of 5.2kW. This would result in a power increase of 1.3kW at each driven wheel.
  • Maintaining 2.25rpm at the driven wheels would increase the approximate torque (minus inefficiencies) to 5520Nm. In addition, the wheel bearing assemblies would be subjected to a new unfactored load of 450kN.

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