29 March 1996

Coming clean on coupling

Semi-automatic couplers on vacuum tankers save time and avoid one of the more unpleasant aspects of slurry disposal. They can also make the job safer. Peter Hill describes the systems available and how users are getting on with them

Slurry tankers feature all too often in Health & Safety Executive reports on farm machinery accidents. Loose clothing becoming caught up in the pto shaft is usually to blame, often the result of the tanker operator leaning across to switch the pump from vacuum to pressure once it has got a load on board.

Which is probably why tanker manufacturer Alan Tomlinson emphasises the safety aspect of his auto-coupling system as much as the convenience aspects. It can fill safely and cleanly without the operator leaving the tractor seat, which means he keeps away from pto shafts, and also from the edges of lagoons and manholes.

The safety of others around the farm is another consideration. Remote filling using one of the many auto-coupling devices available, allows access to lagoons without first having to dismantle a section of safety fence or constantly open and close access gates – or, more likely, leave them open.

Where a replacement manhole cover is available for the filling system (as it is with the TST design), this is another potential danger trap which can be kept covered during tanking operations.

The idea of equipping a slurry tanker with some form of self-filling system is not new. But early designs, mostly comprising a hydraulic arm to dunk the filling hose into the lagoon or manhole, were bulky, added a lot of weight to the tanker, and were expensive.

The latest crop of designs are generally simpler and cheaper, and display some imaginative thinking on the part of the engineers that devised them. All allow remote filling without the driver having to grapple with slurry-laden pipework, and improve work rates by enabling a faster turnaround.

A TST coupling is part of a revised tanking system designed to make slurry spreading quicker and easier for Brian Knight and his son David at Hill Farm, Walgrave, Northants.

There, Brian Knight houses 100 beef cattle over winter and runs a pedigree Landrace breeding herd. These generate a fair amount of dirty water, both from the yards and surrounding concrete areas which get the inevitable spillages of silage as it is carted between store and cattle.

"Yard run-off is collected in a reception pit before being pumped into a 909,000 litre (200,000-gal) above-ground storage tank," explains Mr Knight. "But we dont fill the tanker from the reception pit because its not near enough the roadway for quick turn-rounds."

Submerged tank

Instead, there is a 9100 litre (2000-gal) submerged tank next to the roadway connected to the reception pit by feed and return pipes. A pump circulates the store contents between the two.

"The system works well," says Brian Knight. "It gives us a quick turn-round with no hassle for the driver who no longer has to mess about pulling on gloves to handle messy pipes. I think it will be a huge advantage when we have a full store to empty later in the year."

The TST Mk3 filling system uses clamps rather than suction to connect the tankers filling pipe to the feed hose. These are located on a steel male coupling on the tanker which can be moved out by hydraulic ram to meet up with either 150mm (6in) or 200mm (8in) Bauer female flanged couplings.

Flexible hose runs into the side of the tank from the male coupling which can be tilted through 45í for transport to prevent slurry dripping on to roadways. The female coupling is suspended 60cm (24in) above the ground to form a stand-pipe, and is connected to a flexible hose that can be run into a lagoon or passed through a manhole cover into a reception pit or underground store.

As the tanker approaches the stand-pipe, the filling pipe is extended into position, and the clamping jaws can be operated to firmly hold them together.

It sounds complicated but is easily mastered with a little practice, says Brian Knight.

"Its important to have a hard-standing for the tanker because the coupling has to match the height of the stand-pipe," he notes.

Once the tanker is full, operating the hydraulic control to uncouple the clamps first opens an air valve that flushes out any slurry remaining in the pipe.

Northern Ireland manufacturer S &#42 Watterson also uses a stand-pipe and tanker-mounted coupling hose but relies on suction and a rubber seal rather than physical clamping to get a secure connection.

The filling pipe is lowered from its vertical parked position into a funnel-shaped female connector. A flexible rubber skirt provides a tight seal once the vacuum pump starts running. The cone is attached to flexible hose so there is some movement to allow the two parts to come together if the tanker is not positioned with pin-point accuracy.

Controls are limited to a single lever for simplicity – one pull sets the sequence in motion. Firstly, the filling pipe lowers into place, then the inlet valve opens and another hydraulic ram sets the pump to suction.

Once the tanker is full, the sequence releases the vacuum – so that slurry remaining in the filling pipe drains out – the pipe is raised (so there is no spillage in transport) and the valve and pump are set ready to empty the load.

Fellow Irish tanker maker Tullow Farm Machinery has developed a similar system but with a length of flexible hose on the tanker pipe to help make the final coupling. Two spool valves are used, one to operate the hydraulically raised and lowered filling pipe which uses a rotary seal as the knuckle, another as a remote control for the filling valve.

Hi-Spec Engineerings Slurry Autofill is more versatile in that it can be operated on either side of the tanker. It comprises a length of flexible hose attached to right-angle coupling on the side of the tanker, supported by a parallel lift hydraulic arm.

By mounting this arm on pivots and providing a duplicate coupling, the system can be operated on whichever side of the tanker is most convenient for the store layout. The design also eliminates what Hi-Spec describes as potentially troublesome rotary connections.

At Westerton, a 65ha (160-acre) all-grass unit near Dunecht, Aberdeen, Stewart Youngson finds the time-saving aspect of the Marshall Auto Loader a particular benefit. He runs the farm and its dairy herd on his own.

Quicker task

"Im spreading pretty much every day during the winter, fitting it in whenever I can between milking and other jobs," he says. "The Auto Loader just makes the job that bit quicker; I can now cart four tank loads an hour instead of three."

An automatic scraper system is used in the sawdust-bedded cubicle house to clear passages into an underground storage tank which is emptied whenever necessary.

His 6800 litre (1500-gal) Marshall vacuum tanker is fitted with the companys Auto Loader, an option on all the companys tankers. It comprises a vertical square-section filling pipe, mounted to one side of the tanker, with a rubber seal on the end.

The pipe is raised and lowered by hydraulic ram, and a length of flexible tubing feeds slurry into the side of the tank. An on-off valve is incorporated into the coupling between the rigid and flexible pipes.

The female half of the system is a shallow galvanised steel ramp with an inlet coupling on one side from which a feed hose runs to the slurry store. The ramp can be slung from a blank coupling on the side of the tanker to move it between different slurry stores.

A ramp is also part of the self-filling system developed by Wootton Trailers. But in this case it only protects the feed pipe, which runs through it, from being run over.

Instead of deploying a hydraulically controlled filling pipe, the Wootton Trailers design makes use of the tankers existing structure by sucking slurry through a hole on the underside of the units drawbar. That way, very few extra components are added to the standard specification tanker. &#42

Slurry tanker self-fill systems

Hi-Spec Slurry Autofill (01952-502180)

Horizontal flexible pipe with rigid vertical end section links with female stand-pipe for filling; duplicate tanker coupling and swing-round hydraulic support arm allows operation either side. Tanker sizes 3636 to 13,630 litre (800 to 3000 gal). Option price £1750 for original or retro-fit.

Marshall Auto Loader (01224-722777)

Vertical filling pipe lowered onto suction feed coupling ramp. Tanker sizes 3860 to 10,230 litre (850 to 2250 gal). Option price £1450 for new tankers or retro-fit.

Tomlinson TST Mk3 Automatic Pipe Coupler (0161-7641951)

Horizontal filling pipe aligned by hydraulic ram with female stand-pipe coupler and secured by hydraulically operated clamps. Stand-pipe free-standing or on manhole cover. Tanker sizes 4550 to 13,630 litre (1000-3000 gal). Option prices £1640 for 150mm (6in), £1840 for 200mm (8in) for new or retro-fitment to TST or other makes of tankers, plus £200 for fitting.

Tullow Automatic Filler (01242-890418)

Hydraulically operated filling pipe with flexible end connects with female standpipe. Tanker sizes 5230 to 13,630 litre (1150 to 3000 gal). Option price £1350 as original fitment or retro-fit kit.

Watterson Star Automatic Fill Unit (01648-32251)

Hydraulically lowered filling pipe locates into female cone on support frame via rubber seal. Tanker sizes 2600 to 13,600 litre (575 to 3000 gal). Option price £1382 as original fitment or retro-fit.

Wootton Auto-Fill (01400-230568)

Suction coupling on underside of drawbar lowered by tractor pick-up hitch on to female coupling. Tanker sizes 5000 to 16,000 litre (1100 to 3500 gal). Option price approximately £2000 as original or retro-fitment.

Hi-Specs self-filling system can be operated on either side of the slurry tanker. Controls are limited to a single spool – one pull sets off sequence.

Easy does it – David Knight couples up the Hill Farms TST tanker to the stand-pipe to fill another load. The farm runs beef cattle and pigs.