Pressure Vessel Strain Test Using RE-Series DAQ

I. Project Background and Objectives

In October 2024, a Taihang machinery factory conducted a pipeline pressurization strain test using the RE-Series Rugged Data Acquisition System. The test aimed to evaluate the structural response of pressure vessels under different internal pressure conditions (10 MPa, 20 MPa, and 30 MPa) by measuring multi-directional strain distributions. Data obtained would validate design calculations, ensure safety margins, and identify potential stress concentration areas.

II. Test System and Methodology

1. Sensor Configuration

    Strain Rosette Layout:

• Both Ends: Two rectangular strain rosettes (0° and 90°) attached to capture axial and hoop strains.

• Middle Section: One rectangular strain rosette (0°, 45°, and 90°) to measure multi-axis strains and derive principal stresses.

• Orientation: 0° aligned with the pipeline axial direction.

2. Data Acquisition System

•     Core Equipment: RE-Series rugged data acquisition system with 8 channels for synchronous strain measurement.

•     Signal Conditioning: Built-in quarter-bridge completion and balancing capabilities for strain gauge measurements.

•     Sampling Rate: 100 S/s per channel to capture quasi-static pressure changes.

3. Test Procedure

•     Step 1: Gradually pressurize the vessel to 10 MPa, 20 MPa, and 30 MPa using water injection.

•     Step 2: Hold each pressure level for 5 minutes to stabilize strains.

•     Step 3: Record strain data at all rosette points simultaneously.

•     Step 4: Calculate principal strains and stresses post-test using Mohr’s circle theory.

III. Test Results and Data Analysis

1. Strain Data at Key Points

    10 MPa Pressure:

• Axial strain (0°): +180 με

• Hoop strain (90°): +420 με

    20 MPa Pressure:

• Axial strain (0°): +360 με

• Hoop strain (90°): +840 με

    30 MPa Pressure:

• Axial strain (0°): +540 με

• Hoop strain (90°): +1260 με

2. Principal Stress Calculation

At 30 MPa, the middle rosette (0°/45°/90°) revealed:

• Maximum principal stress: 250 MPa

• Minimum principal stress: 80 MPa

• Shear stress: 85 MPa

3. Safety Validation

•     All measured strains remained within elastic limits (yield strain: 1500 με).

•     Hoop strains were consistently ~2.3 times axial strains, aligning with thin-wall pressure vessel theory.

•     No significant stress concentrations were detected at the endpoints or middle section.

IV. Advantages of the RE-Series System

    High Accuracy

• 0.1% FSO accuracy ensured reliable strain measurements under varying pressures.

• Automatic temperature compensation minimized drift due to water temperature changes.

    Ruggedness

• IP67 rating protected against water splashes during pressurization tests.

• MIL-STD-810G compliance guaranteed stability in industrial environments.

    Efficiency

• Real-time strain display allowed immediate detection of anomalies.

• Exportable reports in PDF/Excel formats streamlined documentation.

V. Engineering Value

•     Design Verification: Confirmed the vessel’s safety factor met ASME BPVC Section VIII standards.

•     Cost Savings: Avoided over-design by precisely quantifying stress distributions.

•     Predictive Maintenance: Data provided baselines for future integrity assessments.

VI. Application Scope

This methodology applies to:

•     Pressure vessels and pipelines in petrochemical plants;

•     Hydraulic system components;

•     Aerospace fuel tanks and propulsion systems.