What are some common problems in pressure vessel inspection?

I. Problems with Inspection Tools and Equipment

1. Inherent Errors in Inspection Tools

The use of measuring tools such as vernier calipers, micrometers, and tape measures without regular calibration leads to inaccurate dimensional measurements.

Traditional "homemade" measuring tools are still used in welding inspections, lacking unified accuracy standards, affecting the judgment of key parameters such as weld height and undercut depth.

2. Inappropriate Pressure Gauge Selection

Inappropriate pressure gauge range selection, not configured to be 1.5–3 times the test pressure, leads to inaccurate readings or damage due to exceeding the range.

Problems such as broken dial glass and bent pointers are common, affecting the reliability of on-site readings.

3. Non-standard Use of Non-destructive Testing Equipment

Radiographic inspection is not operated according to process requirements, resulting in substandard film quality;

Poor coupling of ultrasonic probes affects defect location and quantitative judgment.

II. Inconsistent Inspection Standards and Implementation

1. Lack of Standardization in Inspection Standards

Different units have inconsistent understandings and measurement methods for indicators such as "edge angle" and "misalignment," leading to differences in evaluation criteria.

 Lack of standardized testing procedures and reliance on personal experience for judgment can easily lead to subjective errors.

2. Incorrect timing of non-destructive testing (NDT)

Testing was not performed 24 hours after welding, missing the optimal window for delayed crack development; materials prone to reheat cracking were not subjected to an additional surface inspection after heat treatment.

3. Insufficient testing coverage and areas covered

100% magnetic particle or penetrant testing was not performed on critical areas such as T-joints and fillet welds as required by GB150.4-2011; dissimilar steel joints and weld overlay surfaces were often overlooked, creating blind spots in the testing.

III. Personnel qualifications and operational standards issues

1. Unqualified or mismatched testing personnel

Personnel performing NDT did not hold valid qualification certificates, or their registered employer did not match the actual operating unit.

Unlicensed welders or incorrect welding current parameter settings affected weld quality and thus interfered with the test results.

2. Subjective Judgment Affects Inspection Results

Inspectors rely on experience to visually assess weld quality, failing to strictly adhere to standards; psychological state and fatigue can lead to missed inspections or misjudgments.

IV. Negligence in Safety Accessory Management

1. Safety Valves and Pressure Gauges Not Regularly Calibrated

Safety valves have not been calibrated for a long time, some are rusted and cannot be opened, losing their overpressure protection function; Pressure gauges have exceeded their service life, with pointer malfunctions or reading deviations, affecting operational monitoring.

2. Missing Calibration Records

Calibration dates are stuck at the last scheduled inspection date, actually 2-5 years without inspection, posing a serious safety hazard.

V. Practical Challenges in Inspection Implementation

1. Difficulty in Removing the External Insulation Layer

Users are unwilling to remove the insulation layer, making it impossible to conduct a comprehensive macroscopic inspection of the shell and determine the wall thickness; Delayed or poor-quality restoration after removal affects subsequent corrosion protection and insulation effects.

2. Annual Inspections Perfunctory

Most units did not conduct annual inspections, and operators were unaware of relevant regulations; The large number of containers and insufficient management personnel led to inadequate inspections and difficulty in timely detection of potential hazards.

3. Insufficient Inspection Time

Inspections were concentrated during the factory's annual maintenance period, resulting in tight schedules and heavy workloads, making it difficult to guarantee inspection quality; Inspectors were overworked, increasing the risk of missed inspections.

VI. Disconnect Between Reporting and Information Transmission

1. Frontline Operators Cannot Access Inspection Reports

Reports are only kept at the factory-level management department and cannot be accessed by workshops and work teams, making it difficult to implement corrective measures; Operators are unaware of the actual condition of the containers, lacking a basis for daily maintenance.

2. Incomplete Repair Records

Defect removal, welding processes, heat treatment, and other processes were not recorded in detail, affecting subsequent inspection, evaluation, and traceability.