EMERGENCY POWER FUEL TANKS

By Larry Bush

One of my responsibilities as Foreman of the emergency generator maintenance unit for Saudi Arabian Oil Company was the diesel fuel tanks supplying the diesel engines of the generator set. The Company Dental Clinic in Dhahran is built in a restricted space area. The Level 1 emergency generator sets (start and assume the emergency load in less than ten seconds) were installed in a separate outbuilding with the diesel fuel tank underground.

One of my ongoing projects was to keep extremely close check on the level of fuel in the underground tanks in order to determine if the tanks were leaking. Nearly all of the ESG (Emergency System Generator) fuel tanks throughout the Company had been installed in a hurry and were single-walled with no leakage alarm system.

I suspected the Dental Clinic fuel tank of leaking due to the amount of fuel being put into the tank as compared to what was used and what was remaining in the tank. After a few short weeks, the crew reported that the level in the tank was indeed dropping.

There is a test to determine for certain if the tank is leaking. First, we had to bring a portable tank to the site, disconnect the existing tank, and connect the portable tank to the ESGs. The underground tank was then pumped dry.

The tank pipes, fill lines, and vent had to be sealed. One opening was connected to an air supply with a gauge and supply valve. A low pressure of around 5 psi was then put into the underground tank.

According to the standards, the pressure had to be maintained for a set period of time, around 24 hours. The pressure bled off to zero within 6 hours.

I informed my boss and the Dental Clinic Supervisor that the tank was out of commission. No more fuel could be put into the tank. It would have to be replaced with an approved underground, fuel tank installation.

Saudi Arabia had no standards for this installation at the time. The company was using US standards. Again, the standards were from several different organizations and were hard to understand and follow.

I used pertinent US Standards excerpts to produce a scope of work guideline that I wanted the construction contractor to follow. The contractor had to purchase a double walled tank with leak detectors. The installation was according to US standards for underground fuel tanks.

Shortly after we identified the leaking tank at the Dental Clinic, we located another leaking tank at the Al Hasa residential camp family clinic. This time, the test setup with the temporary fuel tank went very quickly.

After it was determined that the tank would have to be replaced, I sat down with the Clinic maintenance supervisor and discussed the options. The clear choice was to build the tank above ground in a double wall setup with a containment berm also hiding the tank.

The installation proceeded quickly and was put into service within a month. A six-foot high concrete-block wall enclosed the fuel tank. The wall was spray-coated and then painted the same color as the generator set building. It looked good and worked.

Larry Bush

Also watch for more articles by Larry Bush at ...

http://www.Reliability-Consultant.com/Industrial_Articles.htm

About the Author: Larry Bush has been an electrician for 47 years, and in maintenance management for 22 years. Download his e-Book "Emergency Diesel Electric Generators" and the "Maintenance Policy and Procedures Manual" !!