A smiling worker in a red coverall and helmet sits on a walkway atop a series of large horizontal pipelines, surrounded by welding equipment and cables. The forested landscape stretches in the background, with scaffolding visible at the edge of the frame.

Penstock Inspection

Hydroelectric or hydroelectric energy has been a part of New Zealand’s energy system for over 100 years, providing more than half of the country’s electricity needs. Hydroelectric energy and our hydro stations are currently the primary renewable energy sources in New Zealand, and frequent inspection, repair, and ongoing maintenance are key to protecting our energy sources.

Penstocks are pipes or long channels that carry water from the hydroelectric reservoir to the turbines, making them critical infrastructure. Abseil Access has provided specialist services to maintain penstocks for major hydro facilities and clients across NZ, including Meridian Energy & Trust Power NZ, since 1996.

Our penstock integrity inspection services include:

Confined Space Entry (CSE)
Industrial Rope Access
Concrete Condition Inspection
Coating & Corrosion Surveys
Cathodic Protection Surveys
Non-Destructive Testing (NDT)
Concrete & Coating Remediation
Anode Replacement
Spillway Inspection & Maintenance
Shutdown Service & Support

Penstock Specialist Access Services

Abseil Access offer comprehensive specialist access services to penstocks and hydro facilities, including industrial rope access and confined space entry (CSE). Since 1992, the Abseil Access team has provided specialist access solutions to the hydroelectric market, such as surveying, NDT and inspection, industrial maintenance, and current cathodic protection and coating repairs.

Penstock Integrity Inspection

Deterioration of concrete or coating protection systems in penstocks can quickly become a real challenge for hydroelectric plant operators, costing significant amounts in remediation and repair if not identified and dealt with early. Abseil Access provides comprehensive inspection of concrete and steel penstocks, as well as detailed reports and recommendations to enable our clients to manage the integrity of their assets or structures proactively.

Our Group’s inspection pedigree, access services, and concrete or coating protection maintenance capabilities ensure the Abseil Access team can provide safe, high-quality, and cost-effective solutions for penstocks.

Penstock Remediation & Repair

Corrosion, erosion, and degradation of steel and concrete penstocks can occur for various reasons, such as incorrect application, wear, surface damage from scouring, or lack of cathodic protection.

The Abseil Access team has provided a range of magnesium sacrificial anode installations, coating surveying and remediation, and concrete inspection, maintenance, and repair services to penstocks across New Zealand to ensure our client’s assets’ continued protection and operations.

Case Studies

Impressed Current Cathodic Protection

The Cobb Power Scheme was constructed in the 1940s. The twin penstocks are 2.2km long and approximately 1m in diameter. Abseil Access Ltd was selected for the initial coatings & corrosion survey and a further corrosion pit analysis inside the pipe. The upper section of the penstock was chosen for a trial run of magnesium sacrificial anodes. Attachment to the inside surface is with welded studs. Additional resistance and reference probes were also installed to monitor the cathodic protection. Thirty-five anodes were successfully installed in the first 130m section within the 10-day shutdown period.

Manapouri Hydroelectric Powerstation

This underground station has 7 200m vertical penstocks that feed the underground turbines through rock. The penstocks required a concrete condition survey as part of the 30-year Half-Life Refurbishment Project. They are lined with slip-formed concrete and steel. Abseil Access mapped the internal surface, measuring and logging all defects over 200m in height. For further analysis, 100mm core samples were taken up to 300mm deep. Marker pins were installed at key positions for future laser measurements. The inspection project required rope access, lasers, Dyna and core drills, lighting, and CSE 200m down a shaft.

Kaimai Hydroelectric Powerstation

Abseil Access provided a coatings and corrosion survey of the interior steel surface of the twin penstocks. Each penstock descends 700m down a steep slope to feed the main turbines. All corrosion sites and adhesion and DFT testing of the existing coating were marked and recorded. Work began immediately on the corrosion sites with power tools working to ST2. All sites had two coats of high-build epoxy applied. Each of the 80 joints was water-blasted clean with filler applied. Projects like this involve confined spaces, working at heights, poor ventilation, power tools and epoxy paints.

Wheao Hydroelectric Powerstation

Abseil Access provided coatings and corrosion survey and repairs of the interior steel surface of the twin penstocks. The penstocks drop 170m down a steep slope to feed the main turbines. Due to operational requirements, the project had to be completed within a 5-day period during the turbine overhaul. Remediation was completed on corrosion sites working to ST2. All sites had two coats of high-build epoxy applied following an Altex specification. Projects involving confined spaces, working at heights, poor ventilation, power tools and epoxy paints present a unique combination of problems and hazards.

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Capability Statement

Reference Project

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