Shijiazhuang Zhengzhong Technology Co., Ltd (Center Enamel) is recognized globally as a specialized and premier API 620 Welded Steel Tanks Manufacturer. While API 650 covers tanks operating at atmospheric pressure, API 620, "Design and Construction of Large, Welded, Low-Pressure Storage Tanks," governs vessels designed to operate at internal pressures greater than atmospheric but generally within the low pressure range. These low-pressure tanks are essential for storing fluids that are moderately volatile or require slight pressurization to prevent evaporation loss or maintain process integrity, such as certain volatile crude oils, liquefied petroleum gases stored just above their boiling point, or large refinery intermediate products. The safe and verifiable containment of these fluids is mission-critical, requiring an unparalleled level of design and fabrication precision.
Our expertise is concentrated on fabricating customized API 620 Welded Steel Tanks solutions that meet the demanding specifications for low-pressure service, setting the industry benchmark for structural integrity, operational safety, and leak prevention. We focus on delivering solutions that integrate superior structural strength for pressure containment, comprehensive corrosion protection, specialized systems for thermal and volatility control, and unyielding adherence to the complex rules of API 620. Through meticulous engineering, certified automated welding techniques, advanced Non Destructive Testing NDT, and deep material science knowledge, our Welded Steel Tanks are essential assets of maximum capacity, safety, and verifiable quality, securing the vital low-pressure petroleum and chemical storage segments globally.
API Standard 620 is the definitive construction code for large, field-erected, vertical, low-pressure storage tanks. It imposes significantly more complex design and fabrication requirements than API 650, primarily due to the internal pressure loading the tanks must withstand. As a premier API 620 Welded Steel Tanks Manufacturer, Center Enamel adheres strictly to the standard’s mandates:
Design for Pressure and Vacuum: Unlike API 650, API 620 requires rigorous design calculations to ensure the shell, roof, and bottom can safely contain specified internal pressures and full or partial vacuum conditions. The code dictates complex stress analysis and fatigue considerations for cyclically loaded tanks.
Complex Geometry and Roof Types: API 620 often involves spherical, ellipsoidal, or other specialized dome roof geometries to efficiently manage pressure loading, in contrast to the simpler cone roofs common in API 650. This complexity necessitates precise fabrication and fit-up.
Materials Selection and Thickness: The internal pressure requires thicker, higher-strength carbon steel plates than typically used in atmospheric tanks. API 620 demands specific material toughness and weld qualification for the intended minimum design metal temperature MDMT.
Advanced Welding and Testing: The required joint efficiencies for API 620 tanks are often higher, demanding near-perfect full-penetration welds. The standard mandates extensive Non Destructive Testing NDT, including full radiography or other advanced volumetric testing methods, to ensure zero-defect seams capable of holding pressure.
Seismic and Wind Loads: The standard provides rigorous methods for analyzing the impact of seismic forces and wind loads on these taller, heavier, and pressurized structures.
Our commitment to API 620 compliance ensures that our Welded Steel Tanks provide absolute safety and reliability in critical low-pressure service.
The manufacturing process for Center Enamel's API 620 Welded Steel Tanks is a highly specialized and controlled operation focused on achieving the structural integrity necessary for pressure containment.
Achieving pressure integrity starts with meticulous material handling and forming.
Precision Plate Preparation: Plates are cut and machined to extremely tight tolerances. Due to the thicker materials often required for pressure service, advanced forming techniques are used to roll the carbon steel plates into precise cylindrical or specialized geometries, guaranteeing perfect fit-up for the demanding pressure welds.
Automated Welding for Pressure Integrity: We utilize certified, high-grade carbon steel with specialized automated welding systems to execute all critical seams. This technology ensures the high-quality, full-penetration welds required for API 620 joint efficiencies. Every critical weld on the Welded Steel Tanks undergoes mandatory Non Destructive Testing NDT, often including full radiographic examination and magnetic particle inspection, to confirm flawless structural integrity capable of holding pressure.
Reinforcement and Nozzle Design: All nozzle and manway penetrations are designed with specialized reinforcement pads and stress relief features, calculated precisely according to API 620 rules to manage stress concentrations induced by both hydrostatic and pressure loads.
Pressure tanks often store complex, volatile, or hot fluids, necessitating specialized internal defenses.
Sloped Bottom Design: The tank floor is fabricated with a precise sloped bottom leading to a dedicated sump or draw-off point. Although the primary concern is pressure, this feature remains vital for separating water and sediment BS W from the stored product, which is critical for corrosion mitigation and product purity.
Advanced Internal Linings: For aggressive or corrosive contents, the interior receives specialized, high-solids internal linings selected for their chemical resistance and durability under temperature and pressure cycling, isolating the carbon steel from the process fluid.
Integrated Heating and Cooling Systems: API 620 tanks often require temperature control. We specialize in the structural integration of internal heat exchange systems, including specialized heating coils or jackets, ensuring efficient thermal transfer without compromising the pressure boundary integrity.
Insulation Provisions: Robust, pre-engineered attachment points are integrated into the shell and roof to accommodate thick, external thermal insulation and weather jacketing, preventing heat loss or gain as required by the process.
The roof system is integral to the pressure boundary and product protection.
Aluminum Dome Roofs: For large diameter API 620 Welded Steel Tanks where the internal pressure is minimal (just above atmospheric) but a robust, maintenance-free, weather-tight cover is required, we may integrate Aluminum Dome Roofs. These self-supporting geodesic structures are lightweight, corrosion-resistant, and can be designed to cover the primary tank structure, offering superior protection against environmental loads (rain, snow) and reducing atmospheric maintenance compared to heavier steel structures.
Pressure Relief and Safety: The tank design incorporates reinforced nozzle connections for essential pressure vacuum relief valves PRVs VVRs and emergency venting systems, which are calibrated and sized meticulously to comply with API 2000 and ensure the pressure boundary is protected from over-pressurization or vacuum conditions.
Internal Structures: Any internal structures, such as baffles or supports, are welded and designed to withstand the operational pressure, flow turbulence, and thermal cycling required by the process fluid, adhering to the stringent structural rules of API 620.
Center Enamel’s API 620 compliant Welded Steel Tanks are critical assets across specialized segments of the energy and chemical industries:
Volatile Crude Oil Storage: Tanks storing specific crude oil grades that are slightly more volatile than atmospheric conditions allow, requiring low-pressure containment.
Refinery and Petrochemical Intermediates: Storage of intermediate products (e.g., light naphtha, volatile distillates) that are typically held above atmospheric pressure to minimize evaporation and control volatility.
Liquefied Gas Storage: Tanks storing certain liquefied gases (such as large LPG storage) at temperatures just above their boiling point, requiring a robust low-pressure boundary.
Asphalt and Hot Product Storage: While often atmospheric, tanks storing high-viscosity products that require significant heating may be slightly pressurized to assist with transfer, necessitating API 620 compliance for structural integrity under combined thermal and pressure loads.
Our distinction as a leading API 620 Welded Steel Tanks Manufacturer is founded on our ability to handle the geometric and fabrication complexity inherent in pressure vessel construction while maintaining the scale of field-erected tankage.
Unwavering API 620 Compliance: Our engineering and fabrication processes are driven by the complex requirements of API 620, ensuring every tank provides verifiable structural and leak-tight integrity under low-pressure conditions, simplifying client acceptance and long-term regulatory compliance.
Expertise in Aluminum Dome Roofs: We offer the integration of advanced, self-supporting Aluminum Dome Roofs to provide superior, corrosion-resistant external protection, extending the life of the pressure-retaining carbon steel shell and minimizing external maintenance.
Advanced Welding and Testing Technology: The use of certified, full NDT (radiography, ultrasonic) protocols and automated welding systems guarantees the highest metallurgical quality and structural integrity of the high-strength welds required for pressure service.
Comprehensive Process Integration: Our tanks are precisely engineered for complex process needs, including the safe and reliable integration of heating coil systems, insulation provisions, and instrumentation required for low-pressure, temperature-controlled operations.
Verifiable Quality: Our commitment to quality provides documented proof of all materials, welding procedures, and inspection results, a non-negotiable requirement for tanks operating under pressure.
For major energy companies, petrochemical manufacturers, and EPC firms who require the highest level of safety and structural integrity for their low-pressure bulk liquid assets, Center Enamel is the definitive API 620 Welded Steel Tanks Manufacturer.
Our Welded Steel Tanks solutions offer:
Certified Pressure Integrity: Guaranteed compliance with the rigorous design, fabrication, and testing mandates of API Standard 620.
Superior Protection: Option for robust, corrosion resistant Aluminum Dome Roofs for exceptional environmental defense and reduced maintenance.
Maximum Reliability: Verifiable NDT-confirmed welds and comprehensive corrosion defense systems for multi-decade service life under pressure.
We invite you to partner with Center Enamel to secure your critical low-pressure storage needs with API 620 Welded Steel Tanks built for the global standard of excellence, safety, and operational longevity.