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A new concept for lifting

spillway gates

Bryan Leyland MSc, FIEE, FIMechE, FIPENZ Consulting Engineer

New Zealand

www.bryanleyland.co.nz

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“I believe that spillway gates should have a

backup operating system that does not

need an external power supply or

human intervention”

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The systemEach 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

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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

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

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Typical conventional lifting gear

Masjed es Soleyman, Iran

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Typical pumping unitClyde Dam, New Zealand

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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 15 - 20 m stroke

>$300,000 each

•Does not have 100% independent backup8

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The New Concept•Duplicated rams and independent hydraulicsProvides 100% backupBackup system operated directly by water level

a system proven in New ZealandUses low cost “push” rams instead of expensive

tension cylindersany good machine shop can make them

Does not require a mass of concrete to carry ram pivotCost saving of 25% - 50%

•Lower cost - higher reliability!

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Patea Gates NZ 2 - 10 x 10mUse a single push ram

Simpler and cheaper thanthan 2 tension cylinders

Water turbine backup

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Godwin “Bootstrap” gate at Yarrawonga

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ChainWheel

Ram

Ram and lifting chainProof of concept

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New Concept gate ram

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Gate closed andopen

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Gate closed and open

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Suitable Pelton Turbine to drive pump

Made by Eco-Inn in New Zealand

Cost ~$500

~1 kW max

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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

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SummaryThe 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!