Power Generation

'UK Power Generator invests in new CW system operating equipment after 40 years to generate spot on, in just 6 days.'

The Project
To replace a Circulating Water Pump Discharge Valve Operating system that was causing reliability, productivity and environmental problems for a major Power Generator.

The Problem
The existing system was becoming increasingly unreliable and unable to meet spot generation demand. Valuable operations staff’s time was being spent visually checking the valve position indication system prior to generation.
Components were badly corroded, obsolete and leaking oil, causing increasing environmental concern.
Complete the project within a 6 day outage window!!.

The Solution
To remove the existing system and replace with a new system, manufactured, installed and commissioned by Varley Hydraulics own team of specialist engineers.
The new system which had been specifically designed by Varley Hydraulics incorporated;

• A Control and Telemetry system designed to fully interface with the existing system without modification.
• All hydraulic valves designed into a single bespoke circuit manifold assembly eliminating many potential leak paths.
• A new design of hydraulic cylinder interfacing directly with the existing mounting and incorporating stainless steel piston rod and the latest sealing technology.
• A paint system requiring no maintenance for 20 years.
• A valve position indication system incorporating ‘sub-sea’ proximity switches in place of existing troublesome mechanical limit switches.
• A new control cubicle constructed from GRP with heavy duty Stainless steel locks and hinges, incorporating an anti-condensation heater and interior lighting.
• Stainless steel pipework installed by Varley Hydraulics own qualified coded welders.

Sewage & Water Treatment

'United Utilities eliminates sewage outfall with a ‘Varley’ Failsafe Self Contained Hydraulic Actuator'

The Project
To provide a solution for an unreliable Emergency Failsafe Penstock system, with a reliable and cost effective replacement.

The Problem
The main inlet Penstock at a rural sewage treatment works had been failing to open as required, in an emergency or power failure, causing sewer backup and overflow.

The original system consisted of an electric actuator supported by a costly and hazardous battery back-up system. Due to the duty of operation, the electric actuator system could no longer keep up with demand.

Design Brief

• A reliable system that will provide many years of trouble-free operation.
• Minimal operator input due to rural location of site.
• A fully self-contained unit for simple direct mounting to Penstock.
• To interface directly with existing telemetry and power supply.
• Unit to failsafe, opening the Penstock on demand or power failure.

• A self-contained linear actuator utilising ‘Accumulator’ technology to store hydraulic fluid under pressure for fail-safe operation.
• Incorporation of both local and remote control and indication to enable position and status monitoring from a central control room.
• System designed to operate using environmentally safe ‘food grade’ hydraulic fluid.

The Outcome

• All sewer channel overflows are now eliminated with reliable, simplified and cost   effective Failsafe Self Contained Hydraulic Actuator.
• Valuable plant room space has been gained and safety improved, with the removal of the dangerous battery back-up system.
• Client now operates and monitors the system 24 hours a day without the need to travel to site.

Hydro Power

'Alstom Hydro & Scottish Power go for ‘Varley Skid' to operate MIV & Guide Vanes

The Project
Cruachan power station is Scotland’s largest pumped-storage scheme and is located beneath    Ben Cruachan 18 miles east of the town of Oban. The station has four 100MW pump/turbine-generator units supplying power to the National Grid, 2 of these units were to be refurbished and upgraded over the course of 2005.

Varley Hydraulics Ltd was awarded the contract by Alstom Power Hydro to design and manufacture 2 No. high pressure Hydraulic Turbine Governor and Main Inlet Valve (MIV) systems for Units 3 & 4 at Cruachan.

The Specification
Provide a high pressure system utilising the latest hydraulic technology incorporating electronic proportional control.

New system to mechanically interface with existing machinery.

Design a fully integrated hydraulic power unit incorporating all directional control and monitoring systems.

An Accumulator system to be capable of responding very rapidly to generating mode changes and to changes in demand.

Hydraulic cylinders to be of the ‘multi-stage’ type to give a 3 stage closing characteristic, 1 of each pair of cylinders to incorporate a mechanical locking facility

Incorporate a position monitoring system for precise feedback of Guide Vane movement.

The Solution                                                                                                                                       A fully integrated control system using the latest technology in electronic proportional hydraulic control.

• System designed using a bespoke 18 tonne Accumulator support and reservoir fabrication accommodating 2400 Litres of hydraulic fluid.
• Accumulator system with the capability of storing in excess of 400 Litres of fluid under pressure to respond to system demand.
• Bespoke designed hydraulic control Manifolds to minimise pipework and maximise ease of maintenance.
• Hydraulic cylinders designed using the latest sealing technology and incorporating all the system requirements including position monitoring using LVDT’s and proximity switches.

Marine

‘Mobile drilling rig kept a float with Ballast Semi-Rotary Actuator upgrade’

The Project
To overhaul and upgrade the ‘Sovereign Explorer’ drilling rig’s 84off Ballast system hydraulic semi-rotary actuators and incorporate IP68 position indication.

The Problem
The semi-rotary actuators had been in service on a mobile off-shore drilling rig and had become very badly corroded over time.The position indication system had failed completely leaving no means of monitoring valve status.The Actuator units were leaking hydraulic oil and most of the seals had become obsolete.

Design Brief

• Treat corroded surfaces to extend service life of units.
• Design a valve position indication system suitable for IP68 submersion in a salt water environment.
• Modify Actuator seal housings to accommodate latest sealing technology

The Solution

•Shot blast and paint all external surfaces with a 25year life paint system to suit environment.
• Design and fit a valve position indication system incorporating two adjustable limit switches in a bespoke IP68 housing directly connected to the Actuator shaft.
• Fully recondition actuator components, rebuild with new design seals and fully electrically and hydraulically test.

The Outcome

Obsolete Actuator service life extended.

Position indication system now reliable and suitable for many years service in a hostile off-shore environment.

Spares are now readily available.

Power Generation Hydro

‘Helicopter lift to critical equipment in Highlands’

The Project
To design and manufacture an automated valve operating system for a remote eight megawatt hydro power station at Loch Sloy in the Highlands.

The Problem
The existing system was a hand operated arrangement requiring operators to travel up the hillside to the valve house by off-road vehicle to physically open or close the valve.

Design Brief

• Eliminate operator input.
• Facilitate remote control operation.
• A unitised construction is required to simplify installation and achieve a demanding commissioning programme.

The Solution

• Design a system using a motor driven pump unit.
• A suitable control system incorporating alarms for remote monitoring of system status.
• Integrate system in to bespoke hydraulic circuit manifold assembly

The Outcome
Client no longer has to make the long journey to site to operate the valve; the new hydraulic system is operated from central control.
Environmental concerns have been eliminated with the new leak-free system.
New system shall provide many years of trouble free operation.
The equipment was of course completed for the scheduled Helicopter delivery.