As vital piece of Sydney’s infrastructure, Warragamba Dam is under constant maintenance and varying degrees of upgrade. The last year has seen a major undertaking to upgrade which includes improvements to the dam’s spillway gate braking system.
As a precaution against extreme flood conditions where the spillway gate can be impacted by fast flowing high water, the gates were required to elevate to a higher position than previously designed. To accommodate this new ‘open’ position, a new brake and hold mechanism was required. The new system enables the four radial spillway gates to be raised into the new, higher position and locked in place during an extreme flood event. The gates can then be returned to their normal operating position when the flood conditions pass.
Given the forces at play, the projects Engineering team determined that a braking force of not less than 490 kN per brake was required. In order to meet and exceed the specification, Twiflex VMH/2 brakes were selected for this project based on their previously successful implementation on the radial gates of a similar dam in NSW.
These brakes are designed for a maximum braking force of 433 kN at 110 bar hydraulic pressure so the challenge was to produce the extra 57 kN without over-stressing the brake at the higher operating pressure required.
Regal Rexnord Australia and Twiflex Engineers worked closely with the project Engineers and end user to review and agree to the braking specifications and test program. The test program, which is required to be witnessed by an independent, third party inspector prior to the brake units being shipped from Regal Rexnord’s Twiflex facility in Bedford, UK, needed to account for sustained hydraulic pressure, clamping force and, importantly, the Coefficient of Friction (CoF) between the asbestos free brake pads and the brake plate fixed to the gate.
The requirement was to demonstrate the higher braking force met the design stresses to the satisfaction of the inspector and end user, and to prove the braking performance could be achieved using modified 316 Stainless Steel braking plates affixed to the bottom of the Radial Gates. Results as witnessed by the inspector showed the VMH/2 could produce up to 531 kN braking force at 130 bar which exceeded he customer specification for all Radial Gates while fully meeting the design criteria for the Project.
As a result of the engineering efforts of those involved and the manufacturing capability of Regal Rexnord’s Twiflex production plant, 16 x VMH/2 hydraulically applied, spring-released Caliper Brakes will go into service during May 2024. To be installed on specially engineered pedestals, these units will mount either side of each radial gate and be equipped with tie bolt mounting kits, brake monitoring sensors and drain bottle kits.
This is the second such project that Regal Rexnord and Twiflex have been involved in and, at completion, a major damage mitigation project will have been performed to render the spillway gates operable after even the most extreme weather events.
