What is an Oil Storage Tank?

Oil Storage Tank, or industrial oil storage tank, is equipment used to store crude oil, fuel oil, industrial oil, or other liquids related to the energy, petrochemical, and industrial manufacturing sectors. Depending on the intended use, oil storage tanks can be designed as vertical tanks, horizontal tanks, flat-bottom tanks, low-pressure tanks, or tanks with special requirements for corrosion resistance, leak prevention, and operational safety.

In oil refineries, chemical plants, thermal power plants, fuel ports, or heavy industrial zones, oil storage tanks are not merely storage devices but also critical components within the entire technological system. Therefore, the manufacturing process for oil storage tanks requires strict control from material selection, thick plate processing, plate rolling, welding, non-destructive testing, to leak testing and surface finishing.

Why is thick steel plate processing capability required for manufacturing oil storage tanks?

Industrial oil storage tanks typically have large dimensions, large diameters, and high capacities. To ensure structural integrity, hydrostatic load bearing capacity, operational pressure resistance, and long-term stability, the tank body is often fabricated from thick steel plates.

Processing thick steel plates for oil storage tanks is significantly more challenging than processing conventional thin steel plates. As thickness increases, so do cutting forces, rolling forces, welding energy, and the risk of deformation. If not properly controlled, the product may encounter defects such as diameter deviation, ovality, warping, weld cracks, porosity, lack of penetration, or leaks during hydrostatic testing.

Therefore, an oil storage tank manufacturing unit needs to possess the following capabilities simultaneously:

Manufacturing Process for Thick Steel Plate Oil Storage Tanks

The manufacturing process for oil storage tanks from thick steel plates typically involves many closely linked stages. Each stage directly impacts the final quality of the product.

1. Receiving Technical Requirements and Oil Storage Tank Design

Before manufacturing, the engineering department needs to receive complete information from the customer or project documentation, including:

• Tank capacity

• Tank diameter and height

• Type of liquid to be stored

• Operating temperature and conditions

• Fabrication material

• Steel plate thickness

• Design and acceptance standards

• Requirements for corrosion protection, coating, or internal lining

• Requirements for NDT inspection, leak testing, pressure testing, or hydrostatic testing

For industrial oil storage tanks, the design must consider not only capacity but also hydrostatic loads, wind loads, seismic loads (if applicable), foundation conditions, corrosion potential, and installation methods.

2. Thick Steel Plate Material Selection

Steel used for oil storage tanks must have suitable mechanical properties, good weldability, and meet the project's technical standards. Some factors to control include:

• Material yield strength

• Tensile strength

• Impact toughness if operating under special conditions

• Chemical composition

• Weldability

• Material certificates

• Plate thickness and dimensions

For thick steel plates, material selection directly affects cutting, rolling, welding capabilities, and deformation control. The higher the material's yield strength, the greater the rolling force and processing energy required. Therefore, before rolling steel, the company needs to calculate equipment capacity based on material type, thickness, plate width, and rolling diameter.

3. Cutting Steel Plate Blanks According to Drawings

After design completion, steel plates are divided into blanks according to sizes suitable for each tank shell course, tank bottom, tank roof, and auxiliary components.

The cutting stage needs to ensure:

• Blank dimensions are correct according to drawings

• Clean cut edges with minimal thermal distortion

• Tolerances are within permissible limits

• Rational blank division to minimize material waste

• Clear marking of part codes for convenient assembly

For thick steel plates, common cutting methods include CNC cutting, plasma cutting, or oxy-fuel cutting, depending on thickness, material, and cut surface requirements.

4. Weld Edge Preparation and Joint Edge Preparation

After cutting, weld edges need to be processed according to the designed joint configuration. Beveling helps ensure proper weld penetration, especially with thick steel plates.

Common types of weld edge preparation include:

If weld edges do not meet requirements, the weld may suffer from lack of penetration, improper gap, undercut, or internal defects. Therefore, before rolling and assembly, the cleanliness, bevel angle, gap, and straightness of the blank edges must be thoroughly checked.

5. Steel Rolling Technology in Large Tank Manufacturing

Steel rolling is the process of forming flat steel plates into circular arcs or cylindrical shells according to the tank's designed diameter. This is one of the most critical stages in manufacturing the body of an oil storage tank.

When rolling thick steel plates, the following factors need to be controlled:

• Steel plate thickness

• Steel plate width

• Inner diameter of the tank body

• Material yield strength

• Springback after rolling

• Number of rolling passes and correction methods

• Roundness after rolling

• Straightness along the tank body height

Springback is a common issue in steel rolling. After leaving the rolling machine, the steel plate tends to open up slightly compared to the formed diameter. Therefore, engineers and operators need experience in adjusting the rolling radius, number of passes, and diameter inspection methods to achieve the precise shape.

6. Assembling Steel Plates into the Tank Body

After rolling, the steel plates are moved to the assembly stage. Depending on the tank size, the tank body can be assembled course by course or ring by ring.

Important requirements for tank body assembly include:

• Ensuring the roundness of each shell course

• Controlling the gap between weld edges

• Controlling edge misalignment between two plates

• Temporary fastening using jigs, braces, or tack welds

• Checking dimensions before final welding

• Ensuring proper assembly sequence to limit deformation

If the assembly stage is inaccurate, subsequent welding will be difficult to control, easily leading to deformation or overall dimensional deviations.

7. What Technical Requirements Does Oil Storage Tank Welding Entail?

Welding is the stage that directly determines the strength and tightness of an oil storage tank. Welds on oil storage tanks must simultaneously meet requirements for mechanical properties, tightness, shape, and defect resistance.

Key technical requirements for oil storage tank welding include:

Welding Procedure Control

Before welding, a suitable welding procedure must be determined based on the material, thickness, welding position, and applicable standards. The welding procedure needs to clearly specify:

• Welding method

• Welding material

• Current, voltage, welding speed

• Preheating temperature if required

• Interpass temperature

• Number of weld passes

• Welding sequence

• Cleaning requirements between passes

Welder Control

Welders must have skills appropriate for the weld type, welding position, and project standards. For industrial oil storage tanks, many welds have long lengths, complex welding positions, and high-quality requirements, making welder experience a very important factor.

Welding Deformation Control

When welding thick steel plates, concentrated heat at the weld can cause shrinkage and deformation. Without control measures, the tank body may suffer from ovality, warping, or dimensional deviations.

• Symmetrical welding

• Dividing weld sections appropriately

• Welding sequentially from inside out or from the center outwards

• Using jigs and braces

• Controlling heat input

• Checking dimensions after each stage

8. NDT Inspection in Oil Storage Tank Manufacturing

Non-destructive testing, or NDT, is a crucial stage for detecting internal or surface defects in welds without damaging the product.

Common NDT methods applied include:

Depending on project standards, weld locations, and tank criticality, the NDT inspection rate may vary. For high-requirement oil storage tanks, critical welds often require more thorough inspection to ensure safety before leak testing or operation.

9. Leak Testing Procedure for Industrial Oil Storage Tanks

After completing welding and NDT inspection as required, the oil storage tank needs to undergo leak testing to ensure no leakage occurs during use.

A typical leak testing procedure includes:

Step 1: Visual Inspection

Inspect all welds, the surface of the tank body, tank bottom, tank roof, nozzles, manholes, flanges, and auxiliary components. Defects such as cracks, undercuts, surface porosity, or incomplete welds must be addressed before leak testing.

Step 2: Dimensional Inspection

Measure diameter, height, roundness, inclination, tank bottom flatness, and other critical dimensions. Dimensional inspection helps ensure the tank is not only leak-tight but also conforms to the designed shape.

Step 3: Weld Leak Testing

Depending on the tank type and technical requirements, oil testing, vacuum testing, low-pressure air testing, or local leak detection methods at the welds may be used.

Step 4: Hydrostatic Testing or Water Filling Test

For many industrial storage tanks, water testing is a crucial step to check overall tightness and stability. During the test, water level, tank body deformation, and leakage at welds, tank bottom, and connection points must be monitored.

Step 5: Preparing Acceptance Documentation

After successful leak testing, inspection results must be recorded in the quality documentation, including dimensional inspection reports, NDT results, leak test reports, water test reports (if applicable), and relevant material certificates.

10. Surface Finishing and Anti-Corrosion Coating

Oil storage tanks often operate in environments with high corrosion risk, especially in outdoor areas, coastal regions, chemical plants, or areas with oil vapor, salt spray, and high humidity. Therefore, the surface cleaning and coating stage plays a very important role.

The finishing process typically includes:

• Cleaning weld slag, burrs, grease

• Shot blasting or sand blasting for surface cleaning

• Checking surface roughness

• Anti-corrosion primer application

• Intermediate coat application if required

• Final topcoat application

• Checking paint film thickness

• Checking adhesion if required

A suitable coating system helps extend the lifespan of oil storage tanks, reduce maintenance costs, and ensure operational safety.

Advantages of LILAMA 10 in Industrial Oil Storage Tank Manufacturing

With experience in heavy industrial projects, LILAMA 10 has an advantage in manufacturing and installing tanks, steel structures, and non-standard equipment for the energy, oil refining, chemical, and thermal power industries.

Key strengths include:

• Experience in manufacturing steel structures and industrial equipment

• Capability to participate in oil refining, chemical, thermal power, hydropower, and cement projects

• Factory system for manufacturing equipment and steel structures

• Capability for thick steel plate processing, plate rolling, assembly, and large structure welding

• Experienced team of welders, engineers, QA/QC, and construction personnel

• Capability for quality control at each stage

• Experience in on-site equipment and structure installation

• Capability to meet technical requirements for domestic and international projects

For customers seeking an oil storage tank manufacturing unit in Vietnam, LILAMA 10 is a potential choice due to its combined capabilities in design, manufacturing, quality inspection, and industrial installation.