ON THE WATER FRONT

The water industry has seen major changes and developments in the utilisation of plant. The changes to the machines have been evolutionary rather than revolutionary, since apart from esoteric one-offs, virtually every unit used in the water industry is an adaptation of a standard model.

There has been significant development on two fronts; legislation-driven safety equipment is now taken very seriously on site, especially where deep trenching is involved.

Also, the days of exemption certificates when using an excavator as a crane without anti- drop valves are long past. The only remaining anomaly is that you can dig and lower pipes into the trench without an approved SLI, but you cannot unload the same pipes from a supply truck!

There has been considerable activity in the attachment sector with new portable power packs, trenchers, breakers and excavator front end equipment. Of no less importance to contractors is the detection side of any contract where digging around existing services is involved. Locating, identifying and logging underground infrastructure has become a sophisticated and important preliminary operation.

Yet for all its importance to both contractor and client, the latest available district maps remain disturbingly vague as to exactly what is down there and precisely where it is located. Indeed it not for nothing that most blue prints are stamped with the caveat that actual locations may vary from those indicated on the drawing.

Getting it wrong is always going to be hugely costly in terms of money, whether it be compensation, legal, reinstatement or time. There have been some highly publicised mistakes where cable layers have punctured water mains with disastrous results.

Good operators of either big or small excavators may stand a fighting chance of feeling an uncharted obstruction as long as it offers some initial resistance, but moles and chain trenchers will simply impact or saw their way through with little visible impediment to progress.

Only a few short years ago, moling was regarded as a last resort system of getting services from A to B under roads, bridges, railways and similar obstructions. Initially, moles were small diameter devices but the real breakthrough has been the dramatic increase in diameters now on offer.

Even though there have always been steerable moles or boring systems, aiming used the 'guess and God' method mainly because the electronic systems used to track the progress were so vague.

The stories of lost moles abound as they either careened off course, or, more usually, the ground cover became too thick or cluttered for the signals to penetrate. The latest generation of moles rarely get lost. The guidance and receiving systems now have the ability to be able to steer with complete accuracy through 6m-15m of cover, and hit the bullseye 100m-150m down the line.

Pipe cracking and ramming have grown from moling and both have saved contractors and clients significant sums in replacing existing and new laying pipe lines.

What may well be a record was recently completed by a Dutch company which pipe cracked an existing main and simultaneously pulled a 160mm high density plastic water pipe a distance of 285m in one pass.

Like moling, trenching is an art form rather than a science. The best operators don't need gauges to know what their machine is doing, they rely entirely on feel. One long term operator maintains that he can tell when the chain contacts a service pipe and stop it before it causes damage.

That may be just bravado, but his next point is well worth remembering. 'If you run a chain or rockwheel trencher at only 80% of its maximum, you reduce repair and maintenance costs by 100% and taking unscheduled downtime into account, production measured in linear metres will also be greater.'

When hydraulic excavators became generally available in the late 1950s they simply took over trenching and pipe laying from both rope machines and the even older fashioned navvy gangs. Then, early hydraulics left plenty to be desired in the way of reliability and efficiency, but the ability to crowd and dump the bucket independently of all other movements made it an instant winner.

Then came the attachments which made use of the hydraulics such as telescoping dippers with or without grabs to dig deep and vertical holes, boom mounted breakers, sheet pilers and hydraulically powered winches which were reeved over the boom and dipper for lifting, lowering and pulling duties.

The real revolution came less than 20 years ago with the launch of the first mini excavators. Once the construction industry made the discovery that although the machines were little they were still proper digging machines and not toys, they went on to infiltrate every sector.

As with all excavators, they started life with nothing but a bucket but even with just that it offered several major advantages over everything that went before. It is still the only excavator that can be run up onto a trailer, hauled to site by a Transit van, or similar, and then dig a 2.0m deep trench; a true fast response machine.

For its size, the mini offers the biggest and most powerful digging envelope in the business, and on street works and repairs size is of equal importance to ability. Finally, because it is a 360deg slew, it offers the huge advantage of digging over the front and dumping over the rear.

The development of rubber tracks enhanced the machine's appeal further with utilities and especially cable layers since it enabled the unit to operate without causing damage to soft pavements. Another distinct benefit that came to light for machines working in built-up residential areas was that rubber tracks absorbed noise and vibration. 'The reduction is quite dramatic even when digging and in lace curtain territory anything that reduces the environmental intrusion is a help,' added a crew boss.

It did not take the attachment manufacturers long to realise that the mini was the ideal machine to help to expand their markets. The result is that well over 80% of all minis now sold in the UK are fitted with auxiliary pipework to the front end. A smaller number are also equipped with a 'power beyond' circuit so that virtually any hand held power tool, breaker or pump can be plugged in to the machines hydraulic system.

While minis have become the most favoured machine with a number of trenching contractors, it does have its drawbacks. The major one being that it has no load and carry capability and on many in-street trenching jobs, that fact alone is enough to eliminate it from the machine shopping list.

Enter the ubiquitous 180deg backhoe loader that can do, within reason, everything a mini can do, except load over the rear. The standard size machine has to some extent been supplanted by compacts from various manufacturers, and with the addition of a side tip bucket it doubles as a backfiller par excellence.

On greenfield trenching, stockpiling material is no problem, in built-up areas it is. Having an excavator that can reach over the side of a conventional six or eight wheel on-off highway tipper is not enough, it must be able to distribute the load evenly in the body. That means a fair-sized machine which may be unacceptable on a restricted site, so why not consider dumpers?

Double handling of materials is anathema to contractors, but with the latest range of 'big' dumpers hauling to a designated rehandling station it could make economic sense. Also, importing selected backfill could be brought to site using the same system, and with the latest crop of power swivel dumpers, the job could even be more efficient.

Pipe repair and refurbishment has benefited greatly from the advances made in hydraulics, especially in the small power pack sector. These units may not be so glamorous as the big machines, but in terms of return on capital they are winners by a country mile.

In many cases, hydraulic power packs are regarded as another way to drive mainly road breakers and the odd power tool. An example of how far the concept has reached comes from Pat O'Connell of specialist tool supplier South & West (Pipe Tools) of Bristol, who was recently called in by Wiltshier Construction and Severn Trent to remove a section of pipe.

The pipe, a 600mm diameter 12mm-thick ductile iron, was lying in 300mm of water 2.5m below the very busy ring road to the centre of Derby. O'Connell arrived with the latest keel cutter and Falcon power pack from UK Tools and within minutes had the cutter set up and ready to go.

Some minutes later the cutter penetrated the pipe and progressed 230mm round the circumference. It became very obvious that there was still a large volume of water in the line which started flooding the working area. As the trench filled a general exodus ensued. Fortunately O'Connell had the answer with him in the form of a UK Tools hydraulically driven submersible pump.

The hydraulic hoses quick coupled to the pump and at around 800 litre/min, the area was soon clear and the cutter reconnected to the power pack. Excluding the pump-out time, it took 1.5 hours to complete both cuts and remove the old pipe section.

The advantages are overwhelmingly in favour of hydraulics, claims UK Tools. The keel cutter weighs just 13kg and the power pack, cutter and pump will all go into an average sized estate car or small van. Because of the hydraulic power, the unit can work in hazardous gas areas and it will also work under water.

The particular unit used on this exercise will handle pipes ranging from 75mm to 1200mm diameter and requires only 200mm clearance round the pipe. It can be set up to cut square, grooved or bevelled edges for welding in new pipe sections.

UK Tools adds that even windows can be cut in pipes by means of a special attachment that clamps to the pipe. The cutter runs along the axis of the pipe on the attachment and is controlled by a lead screw, similar to that on a lathe. When the longitudinal cuts are completed, the attachment is removed and the cutter reverts to its normal mode of operation and cuts out the ends to complete the job.

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