Driving force: ports need to pay more attention to tyres
Ports can mitigate the huge cost headache of tyres with some clever choices, explains Stevie Knight
The man responsible for the 65 terminal tractors that support P&O’s Nordsea operation, Rene Lok, points out: “When you are made responsible for the budget, you soon find out where the money goes and have to start finding ways to stop it running out the door.” He adds: “After fuel, tyres are our second big expenditure.”
While terminal tractors clock up the highest mileage of all handling equipment, there are big differences between them and, say, a road-going trailer, and although some ports have been tempted to buy a general-purpose tyre, it’s probably a false economy if Mr Lok’s experience is anything to go by.
“The problem is our terminal tractors have to turn in tight spaces on the ship – in fact the front tyres especially suffer a lot of abuse and tend to wear down on the shoulders. However, it is the ramps which are the real tyre killers: these are often not flat and have harsh chevron grips on them.”
So, P&O has worked on a tailored retread solution with Alterever which has a formulation right for its northern European operations and also, critically, “has more substance on the shoulders”. Despite the long two years of development, he’s clear about the benefits: “It’s extended the lifetime by around 30% over and above our previous tyres, so well worth it.”
Retreading the balance
With price being such a big driver, it’s interesting that Howard Malcolmson of Alterever claims that retreads can provide an equivalent if not better tyre for a fraction of the cost of the known market leaders. It’s important because although everyone wants value for money, operators have often been left facing a big divide in the choices they face: “People have tended to either go for budget Chinese tyres or a big-brand named tyre like Michelin or Continental,” he says, with the upper end coming in at the £600 to £800 price mark. Alterever’s solution, he explains, opens up the debate by “aiming to bridge the gap... by providing a cost effective solution that also works for the client”.
However, not all retreads are born equal: Mr Lok previously evaluated another version but with less success: “We first tried out a cold layered tyre: the tread is pre-manufactured and glued onto the old tyre carcass, but these are specifically for maximum mileage on public roads whereas we are looking for grip as well, particularly on steel surfaces.”
A lot of effort goes into Alterever's hot cure retreads, explains Howard Malcolmson. For one, only high quality casings are sourced: these are then put through multiple inspection regimes which include non-destructive testing (NDT) processes designed to reveal the kind of internal flaws “which the human eye can’t see”.
Unsurprisingly, Alterever and new tyre supplier Continental have very different approaches to their rubber – but this makes for an interesting contrast. Julian Alexander of Continental explains: “Each port operation has a huge number of variables and the equipment usually has to deal with at least a couple of different kinds of surface, from asphalt on the roadways to brick sets in the yard plus variations in ambient temperature. Because of this our tyre compounds are formulated for optimal performance across a whole range of conditions… And frankly hotter terminals create more of an issue than colder ones, so if a tyre can deal with these, then much colder terminals will present no problem.” He adds: “While everything is possible and we can tailor compounds for particular circumstances, money comes into it and you have to ask if the operator is willing to pay the premium”.
Given this, it’s surprising that Alterever goes far more than the extra mile for its clients – free of charge.
“Each port has its unique characteristics,” says Mr Malcolmson, so Alterever offers to undertake a site survey which includes a cohesion test of the various tyre contact surfaces. “We then purchase five years back data of the weather specific to the client's location... so the port tyres are both compound and location specific, giving clients like P&O an added-value service.”
Alterever has another money spinning trick up its sleeve: “Terminal tractors are little grafters, and sidewall stiffening helps with overall stability,” explains Mr Malcolmson. It’s achieved by introducing extra material into the wall areas during the retreading process, raising the tyre’s capability. He says it’s an innovation that the company is particularly proud of as it brings improved machine operator safety while reducing unnecessary downtime: “The Alterever terminal tyre carries a load index rating of 175A8 - which is only matched by the likes of Michelin and high-end brand tyres.”
Piling on the pressure
When it comes to larger handling equipment, the sidewalls are just as important, if not more so. For example stability is “critical” for reachstackers, says Mr Alexander.
“If the tyres aren’t stiff enough then the boom can start bouncing around; at best this will slow operations down because the driver can’t engage with the container first time, at worst it can cause an accident. A stable tyre is absolutely necessary for a stable working platform.”
OTR tyres suitable for reachstackers have a lot more ply in the sidewall than truck tyres and are generally meatier all round in order to withstand typically heavy container loads plus all the foreign objects and knocks common to a port environment.
But here lies the rub, quite literally. “It’s not just the outside of the tyre that is in motion,” explains Mr Alexander. “Everything is moving within the tyre too, the nylon ply, the carcass and the rubber, all this builds up heat from internal deformation.” Any significant temperature rise is a large issue as it causes the rubber compounds to break down.
Of course one answer is to make the tyres thinner in order to dissipate the heat, but this is not an ideal solution as it tends to weaken the structure overall. “You need to strike a smart balance between thickness and surface area, but there’s other things you can do like changing the angle of the ply in the core construction which helps lower the potential deformation.”
Port tyres are subject to other quirks which means that predicting both wear and heat build up is not so easy: for example reachstackers are counterweighted to make up for the huge off-centre load at the front, “if a reachstacker is driving around empty you tend to see a lot more wear on the rear than you’d expect, even given that they are the steering tyres”, says Mr Alexander. Further ‘deflection’ bulges can result in the inside walls of a pair of tyres kissing if the dual spacing, air pressure or loads are outside recommended ranges, creating enough hidden wear to lead to a sudden failure.
Down to driving and maintenance
Despite all the efforts put into tyre manufacturing processes, the most significant wear and tear elements are down to how the vehicles are driven and maintained, particularly when it comes to tyre pressure.
“The biggest cost due to failure or increased wear of tyres is down to under inflation,” says Laurence Jones of TT Club. However, he also points out that not keeping an eye on the tyre pressure results in less stability, and as a consequence, there’s a lowered speed at which handling equipment – and especially straddle carriers - is safe to drive. Although Mr Jones doesn’t have the figures, he admits “it has been a contributing factor in some overturns”.
So Continental has developed a tyre check which monitors both pressure and temperature, pulling a signal up on the dashboard – something that will alert the driver that the tyres need attention. “Arguably though, you don’t only want the driver to see the warnings from the tyre sensor, it’s just as much the business of the operator; so we are developing something called the Flexbox which will transmit information to the terminal control room.”
This hopefully will result in planned maintenance instead of emergency intervention “and it keeps vulnerable personnel out of the yard’s danger zones”, points out Continental's Julian Alexander.
These developments are all part and parcel of the inexorable integration of every piece of kit, further signalling the fact that even when it comes to apparently simple choices, operators are now having to make decisions not on the more obvious cost-per-mile basis, but as part of the port’s total productivity calculations.
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