Daily Inspections (Operator Rounds)
Every day, trained operators should visually inspect:
Tank exterior: Check for visible deformation, bulging, or discoloration of the shell.
Weld seams and joints: Look for signs of leakage, staining, or crystallization around welds and flange connections.
Anti-corrosion coating: Note any blistering, peeling, or rust spots on coated surfaces.
Leak detection system: For double-wall tanks, verify that the interstitial monitoring system shows normal status and no alarms.
Valves and fittings: Check for drips, leaks, or unusual vibrations.
Vents and breather valves: Ensure they are unobstructed and functioning freely.
Monthly Maintenance Tasks
Calibrate level gauges and pressure transmitters against manual readings.
Clean debris from tank dikes, spill containment areas, and drainage systems.
Verify that fire protection equipment (foam chambers, monitors, hydrants) is accessible and functional.
Check lightning protection and static grounding connections for continuity.
Quarterly Preventive Maintenance
Test emergency shutoff valves and excess flow valves for proper operation.
Inspect cathodic protection system rectifier output and anode bed condition.
Sample and test stored product for water content, microbial growth, or contamination.
Lubricate gate valves, butterfly valves, and actuator mechanisms.
Annual Comprehensive Inspection
At least once per year, engage qualified personnel to perform:
Ultrasonic thickness measurement (UTM): Map wall thickness at critical locations to identify corrosion thinning.
Vacuum box testing: For tank bottom plates, apply vacuum to detect pinhole leaks.
Hydrostatic or pneumatic retesting: For pressure vessels, repeat original test at prescribed intervals.
Internal visual inspection: Empty and clean the tank, then inspect interior surfaces for pitting, cracking, or lining degradation.
Structural integrity assessment: Evaluate foundation settlement, anchor bolt condition, and shell stability.
Decommissioning and Temporary Shutdown Procedures
If a tank must be taken out of service temporarily:
Drain and purge all product and vapors.
Clean interior surfaces thoroughly.
Apply nitrogen blanketing to prevent internal corrosion.
Seal all openings with blind flanges or caps.
Tag out electrical and instrumentation systems.
When to Call a Professional
Contact your tank manufacturer or a qualified inspection service if you observe:
Sudden increase in leak alarm frequency
Visible product sheen on rainwater in containment dikes
Unexplained loss of tank inventory
Corrosion rate exceeding 0.2 mm/year on UT measurements
Any crack or deformation in shell or roof structure
Zhongneng Huajian offers annual inspection and maintenance service contracts for all types of storage tanks. Our technicians are factory-trained and equipped with portable NDT instruments for on-site assessment. Contact us to schedule your next tank inspection.
