SY/T 5921-2024 in English

SY/T 5921-2024 Standard In-depth Analysis and Technological Evolution

As an important technical standard in the oil and gas industry, SY/T 5921-2024 "Vertical Cylindrical Steel Welded Oil Tanks Operation, Maintenance and Repair Specifications" has been comprehensively upgraded based on the 2017 version. This revision fully absorbs the practical experience of oil tank safety management in recent years, combines technological progress and industry development needs, and puts forward more stringent and detailed requirements for all aspects of operation, maintenance and repair.

Comparative Analysis of Standard Framework and Technology Upgrade

Key technical requirements for oil tank operation management

Optimize the inspection system before commissioning

The new standard clearly divides the inspection before commissioning into The standard covers four subsystems: process inspection, tank inspection, accessory inspection, and auxiliary system inspection. The process inspection requires the tank root valve's remote emergency shutoff function to be intact, with a closure time of no more than 180 seconds, demonstrating a high level of emphasis on emergency response capabilities. Regarding oil inlet and outlet operations, the standard specifies flow rate control requirements: Before the inlet and outlet pipes are submerged, the flow rate must be controlled below 1 m/s; after submersion, the flow rate must be controlled below 4.5 m/s. This requirement, based on fluid mechanics principles, effectively prevents static electricity accumulation and liquid surface disturbances.

Maintenance System Construction and Implementation

Three-Level Maintenance Mechanism

The standard establishes a three-level maintenance system: daily, quarterly, and annual. Each level of maintenance has clear work content and acceptance criteria. Daily maintenance focuses on maintaining basic conditions, quarterly maintenance focuses on the performance of key components, and annual maintenance conducts systematic testing and evaluation.

Technical Requirements for Key Maintenance Projects

For external floating roof tank maintenance, the standard adds requirements for testing combustible gas concentrations in primary and secondary containment spaces. If the concentration exceeds the lower explosion limit of 23%, immediate rectification is required. This requirement, based on the analysis of numerous accident cases, effectively prevents the risk of oil and gas accumulation in sealed spaces.

Innovation and Practice in Repair Technology Systems

Scientifically Designed Repair Cycles

Based on the corrosion characteristics and environmental conditions of different oils, the standard provides differentiated recommended values for tank opening repair cycles. For high-sulfur or high-acid crude oil, the repair cycle is shortened to 8 years in humid coastal climates, reflecting a risk-based maintenance strategy.

Innovation in Online Repair Technology

For the first time, the standard systematically specifies technical requirements for online repairs, covering nine major categories of online repair projects, including seal replacement, ladder roller modification, and edge waterproofing. These technologies can repair defects without affecting the normal operation of the tank, significantly reducing maintenance costs.

Improvement of the inspection and evaluation technology system

Systematization of open-tank inspection items

The open-tank inspection specified in the standard includes eight major categories: macroscopic inspection, corrosion inspection, geometric dimension and deformation inspection, accessory inspection, weld inspection, corrosion protection and insulation inspection, tank foundation inspection, and tank settlement inspection, forming a complete inspection system.

Quantified corrosion evaluation standards

For tank wall corrosion evaluation, the standard specifies quantitative indicators: the minimum average thickness of each ring of wall plate should not be less than the calculated thickness of that ring of wall plate plus a corrosion allowance; the maximum depth of scattered pitting should not exceed 20% of the original design wall plate thickness and should not exceed 3mm. These quantitative indicators provide a scientific basis for repair decisions.

Strengthening and Expanding Safety Management Requirements

Refining Anti-static Requirements

The standard adds resistance requirements for oil sampling ropes (10³Ω/m to 10⁶Ω/m) and rope raising and lowering speed requirements during operations (ascending speed no greater than 0.5m/s, descending speed no greater than 1m/s). These requirements, based on research on electrostatic discharge mechanisms, effectively control static risks during sampling.

Tightening Special Operations Management

Special operations involved in the entire oil tank repair process must comply with the provisions of GB30871. The standard clarifies specific management requirements, such as the work permit system, gas detection requirements, and ventilation measures, establishing a comprehensive risk control system.

Standard Implementation Recommendations and Best Practices

Establishing a Risk-Based Maintenance Strategy

Companies are advised to establish differentiated maintenance cycles and inspection frequencies based on factors such as the tank's service life, fluid characteristics, and environmental conditions. For tanks operating for more than six years, online inspection and evaluation should be conducted annually to promptly identify potential risks.

Improving the Technical Archive Management System

The standard requires the establishment of complete technical archives for tanks, including design documents, construction records, operating data, maintenance records, inspection reports, and repair records. It is recommended to use digital methods to establish a full lifecycle management archive for tanks to provide data support for condition assessment and lifespan prediction.

Strengthening Personnel Training and Qualification Management

Oil tank operation, maintenance, and repair operations require a high level of professionalism. It is recommended to establish a systematic training system and qualification certification system to ensure that operators are proficient in the standard requirements and key technical points and possess the appropriate risk identification and emergency response capabilities.

Technology Development Trends and Outlook

With the development of technologies such as the Internet of Things, big data, and artificial intelligence, oil tank operation, maintenance, and repair are moving towards intelligence and digitization. It is recommended to focus on the application of intelligent detection technology, predictive maintenance algorithms, and digital twin technology in oil tank management to continuously improve the level of oil tank safety management. The implementation of SY/T 5921-2024 will effectively improve the operational safety and management standardization of vertical cylindrical steel welded oil tanks in my country, and provide important technical support for safe production in the oil and gas industry.