Penstock Inspection

Hydroelectric power 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 source of renewable energy in New Zealand, and frequent inspection, repair, and ongoing maintenance is key to protecting our energy sources.

Penstocks are pipes or long channels that carry water down from the hydroelectric reservoir to the turbines, making them critical pieces of 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 have provided specialist access solutions to the hydroelectric market such as surveying, NDT and inspection, industrial maintenance, impressed 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 providing detailed reports and recommendations to enable our clients to proactively manage the integrity of their asset or structure.

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 both steel and concrete penstocks can occur for a host of reasons be it 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 as well as concrete inspection, maintenance, and repair services to penstocks across New Zealand to ensure the continued protection and operations of our client’s assets.

Case Studies

Impressed Current Cathodic Protection

The Cobb Power Scheme was constructed in the 1940’s. The twin penstocks are 2.2km long and approx 1m diameter. Abseil Access Ltd were selected to do 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 assist with monitoring the cathodic protection. 35 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 through rock to feed the underground turbines. As part of the 30 year Half Life Refurbishment Project the penstocks required a concrete condition survey. They are lined with slipformed concrete and steel. Abseil Access mapped the internal surface measuring and logging all defects over the full 200m height. 100mm core samples were taken up to 300mm deep for further analysis. 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 for 700m down a steep slope to feed the main turbines. All corrosion sites were marked and recorded as well as adhesion and DFT testing of the existing coating. Work began immediately on the corrosion sites with power tools working to ST2. All sites had 2 coats of high build epoxy applied. Each of the 80 joints were water blasted clean with filler applied. Projects like this involving confined space, working at heights, poor ventilation, power tools and epoxy paints.

Wheao Hydroelectric Powerstation

Abseil Access provided a 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 completed within a 5 day period during turbine overhaul. Remediation was completed on corrosion sites working to ST2. All sites had 2 coats of high build epoxy applied following an Altex specification. Projects like this involving confined space, 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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