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A section of the steel roof of a large steel tank being inspected.

Ethanol tank inspection

Using a confined space drone to inspect an ethanol tank
Overview

The Job at a Glance

A confined space drone inspection of a 13.5-metre diameter ethanol tank at a gas processing plant in Ireland, using an Elios 2 drone with 4K camera to examine the internal walls, roof structure, and floor — eliminating the need for costly internal scaffolding and confined-space entry.

Irish gas processing plant

Medium-sized facility supplying natural gas to the Bord Gáis grid. One 13.5m diameter plate steel ethanol tank requiring inspection.

Completed in one site visit

Inspection completed in a single coordinated site visit with a team of confined-space trained drone pilots and an independent API-certified tank inspector.

Elios 2 confined space drone

Small, lightweight drone with 4K camera, dust-proof oblique lighting, and GPS-denied stabilisation sensors for operation inside the steel tank.

High-resolution visual record

Complete 4K imagery of the tank's internal walls, roof rafters, floor, stand pipes, and foam filling ports for detailed post-inspection analysis.

Comparative methodology

Why they chose a confined space drone

For this inspection, we chose a confined space drone because it delivered complete visual data on the tank's internal condition without the extreme costs, risks, and downtime of erecting scaffolding inside a hazardous confined space.

Time required
Single field visit vs multi-day scaffold erection

The drone inspection was completed in one day. Traditional methods require days to bring materials through a 50cm hatch and erect internal scaffolding.

Safety
Reduced confined-space entry vs full inspector entry

Only the drone operator enters (confined-space trained). No need for multiple inspectors to climb internal scaffolding inside the tank.

Data quality
4K HD imagery vs limited visual inspection

The Elios 2 captured high-resolution imagery of every internal surface — roof rafters, walls, and floor — with GPS-denied stabilisation and dust-proof lighting.

Efficient option Our method

Using a drone

A safe, efficient, and highly targeted solution using confined space drone technology.

  • No internal scaffolding required The drone accessed every area of the tank — walls, roof structure, and floor — without erecting any access equipment inside the tank.
  • Confined-space trained operators All operators are trained in confined space entry and rescue, ensuring safe operation when flying from inside the same space as the drone.
  • Atmosphere made safe The ethanol atmosphere was purged and verified safe before any equipment entered, eliminating the ATEX-rated drone requirement.
  • Real-time client monitoring An independent API-certified tank inspector directed the inspection live from a dedicated monitoring station on site.
  • GPS-denied stabilisation The Elios 2 maintained precise orientation and stability inside the steel tank using onboard sensors, despite having no satellite positioning.
  • Single-day completion From site induction to data capture, the entire inspection was completed in one efficient field visit.
Project status Complete and verified
Manned approach Traditional method

Without a drone

The expensive, hazardous, and time-consuming traditional approach.

  • Full internal scaffolding required All materials must be brought through a 50cm hatch and assembled inside the tank — a multi-day operation involving significant manual handling.
  • Inspectors working at height inside tank Personnel must climb the internal scaffold to inspect upper walls and roof structure — introducing fall risks in a confined space.
  • Hazardous confined-space entry Multiple inspectors must enter the tank, requiring full confined-space protocols, gas monitoring, and rescue planning.
  • Substantial cost and downtime Scaffold erection, inspection, and dismantling takes days — far more expensive and disruptive than a single drone deployment.
  • Limited photographic record A physical inspection cannot produce the same comprehensive, high-resolution visual record that engineers can review in detail afterwards.
Operational impact Higher cost, risk and downtime
The challenge

Using drones to remove the burden of tank inspections

Inspections of large steel ethanol tanks on natural gas processing plants are critical for ensuring the safe operation of the facility. Traditionally, inspectors perform these inspections by physically entering the tanks and conducting the inspection. However, this method is both dangerous and time-consuming. As a result, many facilities are turning to confined space drones to perform these inspections.

Background

The facility and the tank

The natural gas processing plant in question is a medium sized facility located in Ireland. The processing plant has been in operation for over 10 years and is one of the largest in the country. The facility produces natural gas which it supplies to the Bord Gáis gas grid.

The processing plant has several large steel tanks on site, which are used to store ethanol. These tanks are essential for the operation of the facility, and their integrity must be maintained at all times. For this a regular inspection schedule is implemented by the plant operators. For this project they had a single 13.5m diameter / 10 meter high plate steel ethanol tank that required inspecting.

A detailed photo of the wall-to-roof interface including one of the wall -to-rafter bolted joints.
This shows the detail of the wall-to-roof interface including one of the wall-to-rafter bolted joints. Note the scale rust present on the rafter surfaces.

In the past, inspections of these tanks were performed by inspectors entering the tank and physically access all areas internally. For the tank floor this is not too difficult but for the upper walls and roof structure this is extremely costly and cumbersome. It involves erecting a large scaffolding structure inside the tank to facilitate the inspectors surveying the upper inner structure of the tank. Keep in mind that all materials for this must be brought in through a standard ~50cm access hatch. Clearly, this method was both time-consuming, costly and dangerous. The processing plant management decided to explore the use of confined space drones to perform these inspections instead.

The Methodology

Pre-work planning and preparation

One of the anti-rotation wire attachment points in the roof used to keep the internal floating roof orientated correctly.
One of the anti-rotation wire attachment points in the roof used to keep the internal floating roof orientated correctly.

The processing plant contacted Engineers With Drones as we had both experience and the specific drones required for confined space inspections. Typically our first step when dealing with a new client is to manage expectation regarding what is and is not possible with a drone. This is especially important when dealing with ATEX environments in highly regulated and hazardous sites such as gas processing facilities. For this reason we clarified the following points for the facility operators before going any further:

These two points and more were discussed in a pre-work online meeting with all stakeholders in order to build a plan around the work on the day. As soon as everybody was satisfied with the aim and outcomes of the work a date was set for work to commence.

Overview of the central attachment point for the rafters in the roof. In the original high-resolution version of the photo the treads on the bolts are easily identifiable.
Overview of the central attachment point for the rafters in the roof. In the original high-resolution version of the photo the treads on the bolts are easily identifiable.
Execution

Field work — deploying the confined space drone

Engineers With Drones sent a team of trained drone pilots to the processing plant to perform the inspection. The team arrived on-site and went through the inductions. They then sat down with the site operators for an in depth planning meeting to go through exactly what sort of data they were looking for. This meeting included going through engineers drawings of the tank and assessing suitable point of reference such as hatches and stand pipes. It also included a site visit to the target tank to conduct a FLRA and make sure there were no unseen issues with the plan.

The drone used was a small, lightweight Elios 2 drone equipped with a high-resolution 4K camera and oblique dust proof lighting system. The drone was also equipped with sensors that allowed the drone to orientate and stabilise itself while operating in the GPS denied environment inside the tank.

For this project the drone team was also accompanied by an API certified tank inspector who could direct the inspection based on what he was seeing "on the ground". The team gained entry into the tank through a small 50cm access hatch. Once inside the tank, the operators orientated themselves using pre-designated reference points, in this case a set of three floor-to-ceiling steel stand pipes. The tank itself had a conical steel roof structure with an internal aluminium floating roof. The team found a suitable access hatch in the floating roof that allowed them to see the entire area to be inspected. They then deployed the drone and began the process of inspecting the walls and floor of the tank for any signs of corrosion or damage.

Stand pipe within steel ethanol tank as taken bya drone
This shows one of the three floor-to-ceiling stand pipes used by the inspection team for orientation, Having a clear orientation point ensures that no area of the tank is not inspected. It also allows for efficient and precise identification of defect locations when reviewing data back in the office.

Because the drone team was accompanied by an independent tank inspector it was important for this person to be able to monitor the live feed from the drone at all time to check for defects that would warrant deeper investigation. For this reason we deployed a client monitoring station on this job. This consists of a high-resolution screen about the size of a laptop screen that shows exactly what the drone sees. This can be used by the client to monitor the inspection process without encumbering the drone operator.

Video footage

Ethanol tank drone inspection

A short video showing the drone taking off to conduct another part of the tank inspection. This gives you a sense of scale and size of the tank and the drone.

A short video showing the drone taking off to conduct another part of the tank inspection. This gives you a sense of scale and size of the tank and the drone.
Outcome

Safe, efficient tank inspection completed

The use of confined space drones to inspect large steel ethanol tanks on gas processing plants is a safe and efficient method of inspection. Drones are able to complete the inspection quickly and without the need for inspectors to enter the tanks. This reduces the risk of injury and increases the safety of the inspection.

Detail of foam filling port high up on the internal tank wall.
Detail of foam filling port high up on the internal tank wall.

The gas processing plant in Ireland was able to use a confined space drone to inspect their ethanol tanks quickly and safely. The drone was able to provide high-resolution images of the tank's interior, allowing the inspectors to identify any potential problems. The use of drones for inspections is becoming increasingly popular in the oil and gas industry, and it is likely that more facilities will begin using drones in the future.

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You can find out more about our confined space drone services and our tank and silo inspection services. Alternatively you can contact us here.

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