Coal Silo Inspection with Zenith

SAFETY

Zenith allowed inspectors to stay out of confined space and helped prevent chances of falls or other injuries seen during traditional inspections.

data

The clarity from Zenith’s 18MP camera along with the Add-on Lighting Payload provided the inspectors with the critical data they were looking for, even at a distance.

savings

Since Zenith does not require confined space entry or scaffolding, the silos were inspected in under 30 minutes per silo, saving time & money.

Customer Needs

Omaha Public Power District (OPPD) was seeking a safer and more cost efficient alternative for some non-destructive evaluation (NDE) inspections of the cone-to-skirt welds in their coal silos at the Nebraska City Station. The weld is a union of the stainless-steel liner to the carbon-steel structure. The inspection was needed to prevent any potential silo failures, specifically due to corrosion or defects in this specific weld, which was the root of the collapse of a coal silo at an Indiana power plant in 2016.

The use of carbon steel with stainless-steel liners produces a configuration that is prone to corrosion degradation. Failure Mode Effects Analysis (FMEA) would identify this type of weld as requiring the highest level of quality assurance, however due to the geometry of these suspended cones, they are not easy to inspect.

OPPD needed to obtain two main things out of their inspection with Zenith: the quality data of the weld to ensure structure integrity, and also a safer and more efficient way to conduct these preventative inspections that are critical to the infrastructure of the entire plant. The coal industry has seen the damage that one silo failure can cause, and OPPD took the measures in order to maintain safety and standards.

Our Solution

Interactive Aerial’s Inspection Service team completed the coal silo inspections with Zenith. The Zenith utilized many advanced systems and as well as an additional payload, allowing for safe and fast inspections of the confined assets. The unit used its stabilized camera capable of capturing 4K video and 18MP photos with a 30x optical zoom. Hanging from a cable and free spinning bearing allows for unlimited rotation, which enables the operator to see any spot needed inside the silos. With the ability to drop in the middle of the asset that had no internal barriers, Zenith’s automation feature sped up the inspection time to a mere 25 minutes per silo (with set-up and tear down of entire system).

OPPD’s main request was to get high quality visual data of the cone-to-skirt weld inside each coal silo. Zenith’s 10,000 Lumen LED thrives inside confined, vertical spaces. Due to the wider nature of the coal silos and the reflectivity of the stainless-steel liner, the LED on the Zenith gimbal wasn’t quite able to reach the distance needed for the quality expected in the inspection. The service team attached the Add-On Lighting Payload under Zenith to get the results they needed. The welds were then 100% captured with high definition visuals.

Zenith Inspects Coal Silo Cone-to-Skirt Weld

The results

How had the cone-to-skirt welds been holding up? Were there any defects that could be seen as immediate problems? Did the data from Zenith provide enough for routine use in preventative maintenance inspections? Zenith was able to provide these results, establishing a safer and more cost efficient method to carry out NDE inspections.

OPPD had originally scheduled two full days for the inspection of 7 coal silos. Once the appropriate setup was established, the Inspection Service team was able to swiftly carry out the entire inspection in under one business day.

Omaha Public Power District has determined that Zenith and inspection robotics are a viable alternative to traditional confined space entry. Tools like Zenith are saving the company time, money and the safety of their inspectors.