50 Years - 50 Stories: Luggage Point - The beginning.

50 Years - 50 Stories - Luggage Point WWTP Clarifier Greg Johnston

The following is a story about Aquatec Maxcon's first Luggage Point project experienced first-hand by Greg Johnston, ex-Managing Director of Aquatec Maxcon Group. At the time, Greg was a young engineer just starting his career at Aquatec Maxcon.. He was also the only engineer!

In the late 1970s (about 1977), Brisbane City Council called for tenders for 8 x 140 ft. (42.7m) diameter suction lift secondary clarifiers for Luggage Point. Our company had built a few suction lift clarifiers and drew the tender documents, but we were initially dissuaded from tendering because the specification required many features that seemed to be specific to a competitor and were very unusual. These included 3 bridges for each clarifier constructed from aluminium while the scrapers, sludge collection troughs and feedwell were all to be constructed from glass reinforced plastic - materials of which our firm had limited or no experience at that time. The feedwell was also to be fixed with a siphon to transfer sludge from the collection channels on each bridge to a channel in the feedwell and eventually the outlet pipe, while our usual design used direct gravity flow and required a rotating feedwell. Given that the client seemed to have a specific competing technology in mind, it was initially decided not to bid, especially given the scale of the project and the fact that another significant order appeared imminent. Unfortunately, that order fell through and with only 1 week until the tender closing date, Mr. Peter Maxwell decided that our company would bid and demanded that a complying design be produced ...immediately.

I did a rough design for the hydraulics, structural and mechanical components of the clarifiers quite literally overnight which was quite a challenge as in those days I was the only engineer. The design was sufficient to issue enquiries for the kilometres of aluminium sections and to find a fibreglass manufacturer willing to embark on the project with us.. as well as all the usual mechanical and electrical components, some of which were “super-sized” – the centre bearing for each mechanism was a slewing ring 1,000mm in diameter. There was also the complexities associated with having 3 bridges driven by a single drive unit.

After a very, very taxing week, the tender was delivered and we attended the tender opening. The first bid read out was that of the company whose technology appeared specified and it was more than double our tendered price. I thought at that point that I must have made some terrible errors, but this appeared not to be the case as later bids were lower. The second last bid was that of a company that was usually a little dearer than us. Our tender was read out last and appeared to be the lowest offer by around 10%.

Brisbane City Council invited us to attend a tender interview which was recorded and chaired by Fred Greehalgh, the Head of the Water and Sewerage Department at the time. Mr Greenhalgh made it plain that he was concerned by our company’s limited experience with this type of equipment and the fact that we had never built a mechanism of similar design, especially given that Luggage Point was Brisbane’s largest facility and one of the largest in Australia. He had approximately 20 engineers in attendance, each one was a specialist in some specific aspect of the clarifiers (hydraulics, structural, bearings, sliprings, gearboxes, motors, corrosion, electrical etc.) each of whom had a series of questions. Peter Maxwell dealt with the manufacturing and commercial questions while I dealt with all the technical enquiries. After some gruelling hours of detailed questioning, Peter Maxwell said that he thought that we had demonstrated that we knew what we were doing, but that one young engineer having to deal on the spot with very detailed questioning from 20 experts seemed a bit one sided, so he requested that any remaining questions be put in writing and that we be given a week to answer. We were able to satisfactorily answer all the enquiries and after a second (much more friendly) meeting, we were awarded the project. This was the largest project that the company had been awarded up to that time.

The Letter of Acceptance was duty stamped and attached to the updated tender schedules and correspondence which, together with the Specification and Commercial Conditions, resulted in a Contract document only about 10mm thick in total. This is in stark contrast to the reams of paper that are typically consumed in contracts today that frequently seem almost too large for one person to carry.

Calculations for all flow and load cases were undertaken manually which was quite some undertaking, (some of which was completed on Saturday mornings in the rose garden outside Geyer’s Pharmacy in Inglewood where Tammy was a relieving pharmacist). The design resulted in our requiring dies to be produced for 80 x 80 x 5 box section as no aluminium sections were available in such large sizes, which seems hard to believe today. On inspection when the first delivery was made to our factory, chatter marks were evident in the material resulting in the entire batch (over 500m of material) being rejected. The jig on which the bridges were made was also the subject of some controversy as it was precambered differing amounts on each side, causing considerable consternation among the workshop staff who insisted on trial loading a number of load cases on the first bridge completed in the workshop. Much to everyone’s delight, it performed exactly as designed and the remaining bridges and components were rapidly produced.

The bridges were configured something like a “Mercedes star” hinged from a central bearing and steel pylon, platform and feed pipe with one bridge having an innovative peripheral drive unit which also drove the remaining 2 trailing bridges and resulted in a drive system which was very easy to access and maintain compared to conventional centrally driven designs typically used on large multi-bridge clarifiers of this type.

The glass-reinforced plastic components were produced to an excellent standard by Rapid Fibreglass, commencing a relationship that continued for many years. The siphon priming system was automated to detect impending loss of siphon prime and automatically reprime.

The concrete structures were built by day labour by Brisbane City Council under the supervision of Alan Ginn and were also built to a remarkably high standard with all dimensions and levels accurate to only a very few millimetres. This level of accuracy and meticulous attention to detail resulted in installation proceeding very smoothly as well as commissioning and proving trials, demonstrating the care and attention to planning that had been initiated from the project commencement.

The project proved to be very successful in all respects, being delivered on time and the smooth delivery resulting in costs well under budget, despite the very short time spent preparing the tender. The mechanisms have operated continuously other than expected maintenance, for well over 40 years, demonstrating the high standards maintained throughout.

Since this time, Aquatec Maxcon have enjoyed a long and very productive relationship with Queensland Urban Utilities, with our partnership resulting in many successful ventures through the decades.