A tightness test is not just recommended but essential after installing a Self Bunded Tank—especially given its role in storing liquids, often hazardous, flammable, or corrosive, and the integrated double-walled design that relies on intact containment to prevent leaks. This test verifies that both the inner tank, which holds the liquid, and the outer bund, which acts as a secondary barrier, are free from gaps, cracks, or faulty seals that could compromise safety post-installation.
Purpose of Tightness Testing
- The primary purpose is to catch issues introduced during installation.
- Even with careful construction, steps like connecting fittings, sealing access hatches, or attaching pipes can create hidden vulnerabilities.
- These flaws may not be visible but can lead to slow, gradual leaks over time.
- For example, a poorly sealed valve connection might allow small amounts of liquid to seep out.
- The test identifies these issues before the tank is put into use, avoiding costly cleanup and regulatory penalties.
Testing Methods
- Common methods include pressure testing and vacuum testing.
- Pressure testing involves filling the tank with a non-hazardous fluid or pressurized air.
- Inspectors monitor for pressure drops over a set period.
- Vacuum testing involves creating a vacuum inside the tank.
- A loss of vacuum signals a breach in the structure.
Leak Detection Systems
- For tanks with integral leak detection systems, testing includes verifying these systems function correctly.
- Inspectors may introduce test fluid into the outer bund to ensure sensors detect it.
- This ensures monitoring systems will alert operators promptly if a leak occurs.
Testing Procedures
Pressure Testing
The tank or specific components like the inner shell is filled with a non-hazardous fluid such as water or pressurized with air to a specified level. Inspectors then monitor for pressure drops over a set period—any drop indicates a leak, which can be traced using tools like soapy water to identify bubbles at leak points or specialized detection equipment.
Vacuum Testing
This method involves creating a vacuum inside the tank or the space between the inner and outer walls. A loss of vacuum signals a breach in the structure. This is particularly useful for identifying very small leaks that might not be detected through visual inspection alone.
Sensor Verification
For Self Bunded Tanks with integral leak detection systems such as sensors in the outer bund, the tightness test also includes verifying that these systems function correctly. Inspectors may introduce a small amount of test fluid into the outer bund to ensure the sensors detect the presence of liquid and trigger alarms as intended.
In summary, a tightness test is a critical post-installation step for Self Bunded Tanks. It safeguards against leaks, verifies the integrity of the tank's containment system, ensures the functionality of leak detection tools, and keeps operations compliant with safety regulations—ultimately protecting the environment, personnel, and equipment from potential harm.