Atmospheric metal tanks are essential equipment used in oil refineries, chemical plants, power plants, and fuel distribution terminals. They store oil, chemical liquids, and other fluids under standard atmospheric conditions. These tanks are constructed from metal sheets that are joined and welded together to achieve the required structural integrity. The thickness, material type, and other tank specifications depend on factors such as the chemical properties, volume, and characteristics of the stored liquid. Common material standards for these tanks include ASTM A36, ASTM A283, ASTM A516, and ASTM A572.
Atmospheric metal oil tanks require two main categories of maintenance: preventive maintenance and overhaul maintenance.
- Preventive maintenance involves the regular inspection of tank components—such as thickness, shape, distortion, and coating condition—according to relevant standards.
- If any part of the tank is found to have defects such as corrosion, erosion, cracking, dents, or buckling, overhaul maintenance becomes necessary
This article provides a brief overview of the overhaul maintenance and repair practices for atmospheric oil and chemical storage tanks constructed from metal materials. Key standards related to these tanks include API 650, API 651, API 652, API 655, and API RP 575, among others.
Work Breakdown Structure (W.B.S) for Maintenance and Repair of Atmospheric Oil Tanks
Note: This list is general and brief. The practical and final list must be determined based on each specific pipeline and its applicable standards.
Note: All steps of the work must comply with relevant standards, safety requirements, security protocols, and other applicable regulations.
Item()()() | Job Description |
| 1 | Review maintenance scope, drawings, technical documents and standards (API 650, 651, 652, 655; API RP 575; ASME Section IX; AWS D1.1). |
| 2 | Depressurize, purge, and shut down all relevant systems. Obtain the required work permit. |
| 3 | Drain all pipes and equipment for safety. Open drain valves and vent lines. Ensure all pressure gauges indicate zero pressure. |
| 4 | Install scaffolding and access platforms. |
| 5 | Isolate and disconnect instrument devices and electrical wires & cables. This activity must be performed by an instrumentation expert. |
| 6 | Conduct visual inspection of piping and connected equipment; then prepare a technical report. |
| 7 | Prepare special tools for opening and dismantling the piping system. Note: Before dismantling, ensure all parts (pipes, fittings, gaskets, etc.) are available for reassembly after maintenance. Create a Bill of Materials for this purpose. |
| 8 | Isolate the tank from process lines. |
| 9 | Internal cleaning and gas freeing (per API RP 2016 and OSHA Confined Space requirements). Clean inside the tank using water and steam. |
| 10 | Sandblasting to achieve standard surface roughness for inspection. |
| 11 | Clean sandblasted surfaces and prepare for inspection. |
| 12 | Perform visual inspections for corrosion, erosion, dents, cracks, buckling, bending, holes, etc. Conduct additional tests as required: • Ultrasonic Thickness Testing (UTM) • Magnetic Particle Inspection (MPI) • Dye Penetrant Testing (PT) • Ultrasonic Testing (UT) • X-ray Testing |
| 13 | External visual inspection (API 653 / API RP 575). |
| 14 | UT thickness mapping (shell and bottom). |
| 15 | Internal visual inspection (per API 653 acceptance criteria). |
| 16 | Prepare inspection report. |
| 17 | Repairs (welding, patching, replacement per API and ASME IX). Remove defective parts as required. All activities must comply with standards. |
| 18 | Prepare a new metal sheet and fit it to the tank body. Note: Specifications must comply with API 650, API 653, API 620, API 570, and all other relevant standards. The material for the new sheet must conform to the applicable standards. |
| 19 | Weld the new sheet onto the tank. |
| 20 | Perform post-weld inspections and testing as required, including: • Penetrant Testing (PT) • Magnetic Particle Inspection (MPI) • Ultrasonic Testing (UT) • X-ray Testing • Pressure Testing (hydrostatic or pneumatic) • and more |
| 21 | Maintain cathodic protection system per standard API 651. |
| 22 | Perform post‑maintenance testing, including hydrostatic testing if required, in accordance with API 653. |
| 23 | Surface preparation and coating/lining (SSPC/NACE and API 652). Apply coating and painting per standards. |
| 24 | Curing process. |
| 25 | Perform curing test. |
| 26 | Install and box up all components, including instrumentation, electrical parts, and other related equipment. |
| 27 | Documentation and recertification (API 653). |
Material Requirements for Maintenance of Atmospheric Oil Tanks:
Note: This list is general and brief; the practical and final list must be determined based on the specific pipeline and the applicable standards.
| Item | Specification |
| 1 | Replacement sheets as required, in compliance with applicable standards |
| 2 | Gaskets |
| 3 | Coating materials |
| 4 | Cathodic protection components |
| 5 | Paint cleaner |
| 6 | WD-40 (lubricant) |
| 7 | Anti-seize compound |
| 8 | Additional materials as required |
Tool Requirements for Maintenance of Atmospheric Oil Tanks:
Note: This list is general and brief; the practical and final list must be determined based on the specific pipeline and the applicable standards.
| Item | Specification()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()()() |
| 1 | Hand wrenches in various sizes |
| 2 | Hydraulic wrenches |
| 3 | Flange jacks |
| 4 | Crane (if required) |
| 5 | Lifting belts |
| 6 | Hydraulic flange spreader |
| 7 | Hammers (iron, brass, and Teflon) |
| 8 | Air compressor |
| 9 | Welding machine with accessories |
| 10 | Additional tools as required |
