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 APPLICATION BULLETIN - JULY 1994 | BACK TO INDEX  


PDL's microvector at Pacific Steel - "The sparkies like working with it" 


View of the molten steel plant where temperatures soar past 50°C at Pacific Steel Ltd, Otahuhu, Auckland.

 

Steel making is not for the faint-hearted. Ambient temperatures soar beyond 50°C in the cavernous building the main furnace occupies at Pacific Steel's Otahuhu steel manufacturing complex and the roar and cascade of flame and sparks that erupt as molten steel is poured are a volcanic experience.

It's a testing environment for sensitive control equipment, but one which PDL Electronic's Microvector motor drive series has no difficulty coping with. A recently installed Microvector i-170 is helping to keep steel flowing to New Zealand industry high up on the main gantry crane running the length of Pacific Steel's massive plant.
Pacific Steel, a member of the Fletcher Challenge Steel Sector, has played an innovative role in giving New Zealand its own independent steel supply. A three strand Rokop casting machine gave the Otahuhu plant its first continuous casting capability in 1979 and an upgraded 35MVA transformer for the gutsy electric arc ladle furnace has not only increased the steel plant's capacity but also improved its quality capability.

Important to these environmentally conscious times, Pacific Steel are now major recyclers of scrap steel. Robert Ferris, Pacific Steel's area plant engineer, explains the production process. "We grade the steel scrap according to its expected chemistry and then load blends of this graded scrap into the furnace. As the melting down proceeds we analyse liquid steel samples from the furnace and then put in additives like silicon, manganese and carbon so as to get the chemistry right for the particular quality of steel we're aiming at.

The steel we make has to meet a certain spec and our analysis continues right through to the cast billets. No steel leaves the plant unless it's inside spec. On a good day we make a thousand tonnes of steel in a 24 hour periods. We're producing merchant bar quality steel - as reinforcing steel, angles, channels and flats. What you'd call mild steel through to high tensile steel, which we supply to Wiremakers down the road for turning into farm fencing wire. So we're an important part of New Zealand."

The up-swing in the economy is naturally feeding through to the steel industry.

"Demand and production is up and climbing so it's important to keep the plant working." says Robert. "This is an in-line process so if we have holdups at any point the whole plant comes to a halt. The gantry crane is an essential part of the production process, but we were having continual problems with the resistor banks of the old 60hp slip ring motor driving the auxiliary hoist, which has a 10 tonne capacity. Now, we needed that hoist all the time to lift all the bits and pieces involved in the steel making process - tun dishes (the refractory-lines containers for molten steel), moulds, bags of material and the like. We couldn't have it failing on us."



The Microvector-i with it's sealed electronics compartment, perfect for harsh industrial environments.		 "We were interested in PDL's Microvector-i drive because we wanted better speed control, fewer moving parts and low maintenance. The drive is actually positioned on a switchboard right up near the roof on the main body of the crane and temperatures get so hot up there you burn your hands if you touch bare metal. It's also pretty dirty up there, so the drive had to be pretty robust to be able to cope with all that."

The Microvector-i high temperature rating and dust/splash proof protection makes it ideal for this environment, explains Auckland sales engineer Joe Stanczyk.

"For a start," says Joe, "the electronics in the Microvector-i series are sealed into an inner casing so they're isolated from industrial dirt, heat and moisture - which makes the Microvector ideal for the Pacific Steel application. But the main reason for the popularity of these drives in the crane application is you've got no worries about stalling - you can reliably get up to 200% torque when they're sized correctly. That's why the engineers at Pacific Steel wanted this type of drive. You can have maximum torque at zero speed, which makes the Microvector ideal for a heavy lifting gantry application where you may need some precision holding and positioning of a load before delivery. This drive gives you very precise torque control with very fast response times, because you've got constant shaft speed feedback and the drive can flick from zero to full torque in a few milliseconds - in fact faster than you can blink an eye. That's the sort of control every plant engineer is looking for in a crane."


"In fact, the Pacific Steel application is a very good example of what a modern motor drive can do for an existing plant. Instead of going for a totally new crane, hoist or elevator with all the modern add-ons, all you need to do is buy a Microvector and a standard, off-the-shelf induction motor and convert into the latest technology at a fraction of the cost. With one of our drives you won't need a programmable controller or other external logic. That's all built into the package along with PDL Electronics' service backup and reliability."

Like all PDL drives, the Microvector keeps plant staff right up to date with the current status of the drive via a two-line, 32 character, plain language message display. Messages include status, commissioning adjustments, faults and operating parameters and staff can readily key in new operating parameters "on the run".

Robert Ferris has the final word on reliability and operator friendliness. "We're seeking gear which is reliable and troublefree and the Microvector gives us that. We find it easy to work with, easy to fault find and very user friendly with excellent documentation. The sparkies like working with it. What more can you say."