ROV penstock inspection Golden Falls Hydroelectric Station Inspecting a live penstock on the River Liffey safely and efficiently, without putting a single diver at risk.

Getting eyes inside one of the most hazardous structures on a hydroelectric dam

A penstock is the steel tube that channels high-pressure water from a reservoir directly into a power-generating turbine. It is one of the most critical - and inherently dangerous - structures on any hydroelectric plant. Traditionally, getting a clear picture of its internal condition meant either a complete, highly disruptive dam drain-down or sending commercial divers into a hazardous confined space where the risks can be life-threatening.

The operators at Golden Falls, a hydroelectric station on the River Liffey in Co. Wicklow, brought their problem to Engineers With Drones. They needed a complete, reliable condition report on their penstock without the extreme risks and downtime of a traditional inspection. Our solution? Deploy a specialized underwater ROV.

Planning the inspection - drawings, egress, and engineering the approach

We are engineers first. Before any equipment leaves the office, we analyse the engineering drawings and detailed cross-sections provided by the client. This allows us to map out a clear access route and, critically, a fail-safe egress model. In ROV operations, especially in confined infrastructure, the primary question isn't just "how do we get the ROV in?" - it is "how do we guarantee we can get it back out?"

Our identified access path was an air shaft running from the top of the dam directly down to the penstock. At approximately one metre square, it was perfectly sized to deploy the ROV. Crucially, where the shaft met the penstock, the concrete featured a smooth radius rather than a sharp 90-degree corner, ensuring our tether could run cleanly without snagging. Because the penstock sits at an angle, the transition from the vertical shaft into the pipe was highly manageable for cable routing.

Safety is paramount. Strict mechanical and electrical isolations were implemented to ensure no gates could be opened and no turbines could start during the operation. We conducted thorough field-level risk assessments on-site, verifying our desk-based plan against reality before a single piece of equipment touched the water.

Inspecting the expansion joint, screens, and spiral casing

The expansion joint - targeting the focal point

The Golden Falls penstock features a bellows-style expansion joint. This is designed to accommodate longitudinal movement as the sheer volume of steel expands and contracts. Because these joints naturally accumulate material and are a primary focal point for corrosion, the client specifically needed eyes on this area.

The HD footage captured the joint in full detail: a continuous gap allowing relative movement between the steel sections. We identified significant silt buildup inside the joint, which is entirely consistent with the turbine being offline for an extended period prior to our inspection. Without flow, sediment settles. This clear visual evidence gave the client exactly what they needed: clear data to decide whether to authorise a costly drain-down and clean. They could now plan, budget, and justify the remediation properly before committing a single penny.

Screens and inlet gates

Our engineers extended the inspection up to the debris screens at the water intake, as well as the gate slots, gate seals, and the concrete seating surfaces. The screens were found to be in good condition, showing only minor, expected leaf and debris accumulation. The concrete integrity and steel condition around the gate slots were thoroughly verified.

The spiral casing at the turbine inlet

Finally, the ROV navigated downstream through the turbine outlet and straight into the spiral casing - the shell-shaped chamber where water rapidly accelerates into the turbine. Sitting at nearly 17 metres deep, this is one of the most inaccessible parts of the entire facility. The footage revealed significant vegetation growth on the bronze turbine castings, again confirming a prolonged period without water flow. We successfully inspected the turbine hub and blade arrangement, navigating through minor turbulence and bubbles caused by slight leakage past the isolated gate.

A complete condition report, zero downtime

The client received a comprehensive, plain-English HD video record of their penstock, expansion joint, screens, gates, and spiral casing. We successfully inspected and documented every critical area of interest. The primary findings - silt in the expansion joint and vegetation in the spiral casing - were directly tied to the turbine's inactivity and are now clearly quantified in footage the client can instantly review, share, and act upon.

What traditionally demands a planned drain-down operation - involving peat sealing, gate isolation, full dewatering, hazardous confined-space entry, and substantial costs - was instead executed in a single, safe field visit. We operated entirely from the roadside, delivering complete clarity with zero personnel entering the water.