APPLICATION BULLETIN - AUGUST 1995 | BACK TO INDEX  

Energy savings from drive in Hazardous Area impress Petrocorp

Brent Sheridan, PDL Sales Engineer, discusses the application with Charlie Holm and Noel Butler from Petrocorp Exploration.

The New Plymouth-based electrical maintenance co-ordinator for one of our leading players in New Zealand's fast -developing petroleum industry, is more than a little pleased with the energy savings and the greater plant efficiency he's been getting over the past two years since the company decided to install PDL motor drives on its key production plant motors.

So far Petrocorp have installed eight PDL motor drives of various capacities at various installations in the Taranaki region including McKee and Waihapa fields where hazardous area applications are involved.

An export shipping pump located at the McKee production station provides Noel Butler with a good example of what can be gained from converting fixed speed installations to variable speed drive control. The shipping pump is a key unit in the production line, driving crude petroleum through Petrocorp's pipeline to their tank farm at Omata in New Plymouth.

"Previously the flow rate was throttled with a control valve", explains Noel. "The pump itself is driven by a 187kW motor and was put in ten years ago. When we did our original power readings it was about 100kW. Then twelve months ago, after talking with the guys from PDL, we installed a UDi 340 drive on the motor and we estimate energy consumption has dropped back to 20 to 30kW. That sort of savings means we're talking about a 12 month payback period on probably $60,000 worth of equipment and installations, which is very significant in this business.

"We had a bit of trouble identifying what the energy savings would be prior to the changeover, but estimates we received from Ingersoll-Dresser, who supplied the pump originally were virtually spot on."

The McKee field has been in production for the past ten years and during that time has yielded over 30 million barrels of oil. During the 1993/94 year a production rate of 6,400 barrels of oil and 19 terajoules of gas a day was achieved and last year the company announced it would spend $30 million extending its activities on what it believed was an under-developed resource.

McKee is believed to have reserves of 13 million barrels of oil and 78 petajoules of gas so it is an important asset in any calculation.

The success of the McKee installation convinced Noel Butler on the safety issue. "We've set up the same arrangement at our Waihapa production station where we've got a UDi on another pump in a hazardous area. The thing that applies here is that PDL have got certification from Brook-Hanson for various types of motors and that's what a design engineer is really looking for with hazardous area installation".

PDL Electronics General Manager David O'Donoghue stresses the importance of the energy efficiency argument in light of the overall increase in power charges New Zealand can expect over the next few years.

"You have to always bear in mind that running a pump at a constant speed, particularly when demand fluctuates - as it usually does - is inherently inefficient and results in substantial energy costs. Savings achieved by introducing a variable speed drive to a pumping application can exceed 50% of running costs, which provides very rapid payback of the initial capital expenditure required."
Clearly the advantages to be obtained by installing a motor drive on a pump rather than using any of the conventional control options - on-off switching, throttling, or use of a by-pass system - make the drive the preferred solution in every case.

With the energy savings inherent in being able to vary motor speed over a stepless power gradient come other added advantages which are in-built characteristics of the drive package - intelligent control from a central control board, improvement in system efficiency, reduced starting current, smooth acceleration and deceleration resulting in less wear and tear on the power train - advantages which in themselves carry a cost benefit.

The same advantages naturally carry over into other drive applications, explains Noel Butler. "We've also installed PDL drives on our vapour recovery compressors and we've got one on a cooling fan that's automatically controlled via temperature control which gives us the advantages that we can alter our cooling via the variable speed characteristics rather than getting into more inefficient alternatives like changing the pitch on fan blades or altering shutters." Noel is convinced that the PDL drives are the way to go.

"They just sit there and keep going. The one in McKee we put in nearly 12 months ago and I've never been back to it. It's a vast improvement on our previous situation because we get the added advantage of flexibility of control as well as energy savings."