1 A new concept for lifting spillway gates Bryan Leyland MSc, FIEE, FIMechE, FIPENZ Consulting Engineer New Zealand

2 I believe that spillway gates should have a backup operating system that does not need an external power supply or human intervention

3 The system Each gate has two independent sets of hydraulic rams in a novel configuration One set is powered by a conventional hydraulic system with electric pumps The backup set is powered by a pump driven by a water turbine If the lake level is too high, water overtops a weir and drives the turbine

4 Background Something like 30% of dam failures are caused by spillway gates failing to open* Dams have failed in less than a 10 year flood because all the gates failed to open Most modern gates are lifted by hydraulic rams Emergency backup operation usually involves manual intervention and, in many cases, manual lifting *Prof Raymond Lafitte

5 How many strong men do you need to raise a 30 tonne gate?

6 Typical conventional lifting gear Masjed es Soleyman, Iran

7 Typical pumping unit Clyde Dam, New Zealand

8 So what is wrong with current practice? Totally reliant on the integrity of a pair of tension cylinders and associated hydraulic system If one cylinder fails, most gates fail to open Must have one or more backup power supplies Cylinder and hydraulics are expensive >$1 m for a large gate Cylinders can have m stroke >$300,000 each Does not have 100% independent backup 8

9 The New Concept Duplicated rams and independent hydraulics Provides 100% backup Backup system operated directly by water level a system proven in New Zealand Uses low cost push rams instead of expensive tension cylinders any good machine shop can make them Does not require a mass of concrete to carry ram pivot Cost saving of 25% - 50% Lower cost - higher reliability!

10 Patea Gates NZ x 10m Use a single push ram Simpler and cheaper than than 2 tension cylinders Water turbine backup 10

11 Godwin Bootstrap gate at Yarrawonga

12 Chain Wheel Ram Ram and lifting chain Proof of concept

13 New Concept gate ram

14 Gate closed and open

15 Gate closed and open

16

17 Suitable Pelton Turbine to drive pump Made by Eco-Inn in New Zealand Cost ~$500 ~1 kW max

18 Other applications Backup system can be used as sole lifting system for small or less critical gates Same system can be used to raise vertical lift gates

19 Summary The only system that provides 100% independent backup Backup system operated directly by water level completely independent units Uses low cost push rams instead of expensive tension cylinders any good machine shop can make them One AC hydraulic pumping unit can serve several gates Lower cost: better reliability!