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 APPLICATION BULLETIN - AUGUST 1994 | BACK TO INDEX  


Controlling heavy metal fans has always been a major challenge

Steve Griffiths (Project Engineer, McClunie Birch) shows Hamish Robertson (PDL Electronics Ltd) over the installation of the MVR fans at Anchor Products site, Waitoa.


PDL Electronics are no strangers to the dairy industry, but their involvement with Anchor Products' Waitoa milk powder plant has broken new ground both for New Zealand's premium drive manufacturer and for one of our leading process engineering companies, McClunie Birch Ltd of Hamilton.

For PDL, the breakthrough follows some months of strong campaigning aimed at convincing Waitoa's European contractors, Stork Friesland and Schiele that New Zealand-made drives are not only competitive with the best in the world, but also offer the sort of superior technology and backup international customers expect from leading suppliers. "Basically there's never been an application like this before in New Zealand," says Tom McClunie of McClunie Birch. "Our brief from Anchor for the Waitoa project was the supply and construction of a complete milk powder plant capable of producing 11.7 tonnes of instant whole/skim milk powder per hour around the clock. To give some idea of the scale of the plant, the nearest plant in production size in New Zealand would be Kiwi Co-Operative Dairies down in Hawera, which has a throughput of 10 tonnes per hour - we were also involved in that project."

"The fans, motors and drives for a plant of this size have to meet some very demanding standards. The evaporator fans weigh over three tonnes, run at 3000 rpm and take nearly an hour to coast to a halt, so we're talking about a very high inertia factor coupled to specifications that call for spin start and dynamic braking capabilities in the motor drives. Then there's the fact that this plant has been built to continuously process three million litres of milk every 24 hours into milk powder, which means there's no latitude for breakdowns or unplanned stoppages. In fact there are very severe penalties built into the contract to avoid this. So reliability can't be stressed enough."

"In the past in similar projects throughout New Zealand, the motor drives have all come from Germany - either Siemens or Asea Brown Boveri. In fact all the major technology is European and the main supplier, Stork Friesland of the Netherlands, give very strong guarantees covering the total plant, so any supplier has to prove themselves against some very exacting standards."

"As far as we were concerned PDL were the preferred drive supplier on grounds of quality, service and backup and we promoted them quite heavily to the Europeans. Drives from overseas are never quite the same in our experience. A New Zealand operation needs New Zealand backup and support on the spot when you need it and PDL have built a reputation for the speed and reliability of their response."

Richard Scrivener, PDL's sales manager, worked intensively on the drive project from Day 1. "We established from the start that the best configuration for the Waitoa situation would be three of our latest UDi-1140s, which enclose the actual inverter in a completely sealed environment. The UDi-1140s are a parallel drive based in this case on six UDi-660s and we released the series for the first time at the Hannover Trade Fair last year, so they've already had some international exposure."



The PDL UDi-1140 controls one of the MVR fans on the Waitoa site.		 "The parallel configuration in this heavy industrial application is something we'd already successfully sold to an earlier European customer, the Leipzig North power station authority. The Leipzig application was actually identical in many respects to some of the main demands of the Waitoa evaporator project - controlling a high inertia three tonne fan with speed control, spin start and energy saving characteristics."

"Factors like inertia, weight and power are extremely important in a plant of this size. You need to realise that each of the three tonne fans on the Waitoa evaporators is 2.4 metres across and is being driven by a 630 kW electric motor - say the equivalent in horsepower of two Mack trucks! So our application engineers at Napier had to look at the spin start and dynamic braking feature of the job very carefully. This is a very skilled area as the calculations involved demand a lot of technical expertise as well as a practical knowledge of drive behaviour under high industrial loads. In this respect our Napier applications team are definitely world class."


"Another significant point I'm sure the Europeans gave a lot of weight to was the fact that we'd already done a lot of work with local dairy companies proving the reliability of PDL drives and our service backup. For example, we'd already successfully installed a similar drive configuration to Waitoa's - based on our ASDi series - at the Tui milk powder plant several years ago. In fact we've supplied millions of dollars worth of drives of various sorts and other technology to the New Zealand dairy industry over the years and this along with the fact that we're manufacturing to the ISO 9001 quality standard means we had a pretty impressive track record to show the Europeans."

The Waitoa project was something of a milestone for McClunie Birch also, explains Tom McClunie.

"Waitoa presented us with quite a unique configuration based on the demands of round the clock production - one big drier and three evaporators. Normally at some point in the milk evaporating cycle you have to stop the production cycle so the evaporators can be cleaned - conventionally you operate for twenty hours and close down for three so that cleaning can take place. Stork's design configuration permits the closing down of each evaporator in turn for cleaning while the other two maintain production. This is why the drives play such a vital role in the whole plant concept. They have to keep the production cycle running, otherwise we lose production - and of course we've got millions of litres of milk coming in which can't be burned off just like that."

In the arcane world of dairy processing Stork Friesland specialise in the design, construction and commissioning of multislage evaporators. The Stork Group, of which it is part, is a billion dollar Netherlands-based industrial conglomerate specialising in design and manufacturing services for the printing and coating industries as well as the food processing and packaging industries. Stork usually sub-contract the actual plant manufacture and in the case of Waitoa, the supply of evaporator fan units, motors and drives was under the control of Schiele GmbH in Germany, where PDL already have their own registered company.

Even with this advantage, Northern Area sales manager Richard Williams explains, PDL still had a lot of ground to make up in convincing Schiele that the UDi drives could perform to the same exacting standards they were used to in Siemens and ABB equipment.

"The biggest problem we had, I suppose, was the fact that New Zealand is mostly known of as a tourist destination rather than as a nation with an industrial capability. So we really had to be bring Schiele up to speed with a lot of detail about PDL and its history that would probably have been unnecessary had we been, say, an American or a UK company." Steve Griffiths, project electrical engineer with McClunie Birch, confirms that PDL's business style impressed the Germans.

"The Germans were blown away by the speed of the PDL response to their queries. The giants in the business tend to dictate to the clients what they need. PDL listened and proved to the Germans that they could offer a much better service as well as a better drive."