Checking the Life Left in an Underground Methanol Tank
A company needed to assess the safety and remaining lifespan of an underground methanol tank after 26 years of continuous use. CorroSafe conducted a Remaining Life Assessment, discovering internal corrosion, metal thinning, and weld damage but no structural cracks. Despite an inability to inspect the outer surface, they concluded the tank has 10–12 years of safe life left if immediate repairs and protective linings are applied. The case highlights how proactive, data-driven inspections can replace reactive maintenance and enable safe, planned asset management.
About Case Study
The Problem
A company had an underground tank used to store methanol. The tank could hold 20 kiloliters. It had been working non-stop since the year 2000. After 26 years of use, the company wanted to know: Is the tank still safe? How much longer can it be used?
So they asked CorroSafe to do a detailed study called a Remaining Life Assessment.
What CorroSafe Did
CorroSafe checked the tank’s metal, which was a type of steel known as IS 2062 Grade B. They looked for damage and tried to find out how fast the metal was wearing out. Their goal was to give the company a clear plan: keep using the tank safely or replace it.
What CorroSafe Found
The main reason for damage was that the tank had been storing methanol for many years without any protective layer on the inside. This caused the inner metal surfaces to slowly rust and react with the chemical.
Here are the specific problems CorroSafe found:
- Widespread rust and peeling of metal on the inside walls and end plates.
- Small holes and gaps near the welded joints, especially around the pipe and nozzle areas.
- The metal had become thinner. It started at 10 mm thick. Now it was losing about 0.10 to 0.11 mm every year.
- The metal structure looked normal under a microscope. No tiny cracks or major breakdown.
- The hardness of the metal was also normal. No unusual hardening.
- A big unknown: The tank was buried in a sand-filled underground space. So CorroSafe could not check the outside surface. This means there could be hidden damage from the soil side.
How CorroSafe Did the Inspection
They followed clear and standard rules:
- ASME rules for measuring thickness using sound waves.
- IS 2062 rules for checking steel properties.
- Good Engineering Practice for tanks where no specific design code existed.
The Solution Suggested by CorroSafe
CorroSafe recommended both short-term and long-term actions.
For the long term:
- Clean the inside by blasting it with abrasive material.
- Apply a strong protective lining that can resist methanol.
- Repair all holes and gaps found in the welds by grinding and re welding properly.
- Dig out some sand around the tank to check the outside surface for damage.
For immediate safety:
- Do the next thickness check within 3 to 5 years, especially in areas that wear out faster.
- Keep testing the methanol to make sure no harmful chemicals are speeding up the damage.
The Final Result
CorroSafe concluded that the tank still has about 10 to 12 years of safe life left. But this is true only if the company takes quick action to fix the problems.
By using advanced testing methods and metal analysis, CorroSafe helped the client move from fixing things only after they break to managing safety in a planned way. This means the tank can be used safely for now, and the company can also plan for a future replacement without sudden emergencies.