Pressure resistance and durability test

Pressure Resistance and Durability Testing Service – Accredited ISO/IEC 17025 Long‑Term Pressure Integrity and Reliability Assessment for the Croatian Market

Pressure resistance and durability are critical performance parameters that determine the ability of components, systems, and materials to withstand internal or external pressure loads over extended periods without leakage, deformation, or failure. These properties are essential for ensuring the safety, reliability, and economic efficiency of products used in oil and gas pipelines, pressure vessels, hydraulic systems, pneumatic components, automotive fuel systems, medical devices, and packaging. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo gospodarstva i održivog razvoja, the Državni inspektorat, and the Carinska uprava enforce strict quality, safety, and environmental standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of pressure resistance and durability is essential for product certification, supplier qualification, type testing, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive pressure resistance and durability testing service, applying standardized methods such as ASTM D1599, ISO 1402, ASTM D2992, ISO 19879, ASTM D4991, ASME BPVC Section VIII, and HRN EN ISO 1402 to measure burst pressure, proof pressure, pressure cycling endurance, and long‑term creep rupture under controlled temperature, pressure, and environmental conditions. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Croatian authorities and notified bodies, making them indispensable for regulatory compliance, product validation, and market access in Croatia and the European Union.

Test Samples and Components We Regularly Examine

Our laboratory receives a wide variety of materials, components, and systems for pressure resistance and durability testing. Typical samples include:

• Pipes, tubes, and hoses – for hydraulic, pneumatic, and fluid transfer systems.
• Pressure vessels and tanks – for gas, liquid, and chemical storage.
• Valves and actuators – ball valves, gate valves, control valves, and pneumatic actuators.
• Pumps and compressors – centrifugal pumps, positive displacement pumps, and air compressors.
• Hydraulic and pneumatic components – cylinders, accumulators, and fittings.
• Packaging and containers – drums, bottles, and flexible packaging for pressurized contents.
• Prototype and new designs – submitted by manufacturers for validation of pressure durability before series production.
• Field‑retrieved components – for failure analysis and remaining life assessment.

Pressure Strength Testing – Burst and Proof Pressure Evaluation

Pressure strength testing determines the maximum pressure that a component can withstand before failure. The burst pressure test measures the ultimate pressure capacity, while the proof pressure test verifies that the component can withstand the design pressure without permanent deformation or leakage. Our procedures follow international standards and the requirements of the Croatian industrial, energy, and manufacturing sectors.

• Burst pressure test (ASTM D1599 / ISO 1402 / HRN EN ISO 1402 / NTC 5600 – for pipes, tubes, and hoses) – we pressurize the test item with a liquid (usually water) or a gas at a controlled rate (e.g., 10 MPa/min) until it bursts. The burst pressure (in MPa or bar) is recorded, and the failure mode (e.g., rupture, pinhole, or seam separation) is noted. We report the burst pressure, the failure mode, and the failure location.
• Proof pressure test (ASME BPVC Section VIII / EN 13445 / NTC 5601 – for pressure vessels and tanks) – we pressurize the test item to 1.5 times the maximum allowable working pressure (MAWP) and hold the pressure for a specified duration (e.g., 10 to 30 minutes). The item is inspected for any leakage, permanent deformation, or rupture. We report the proof pressure, the hold time, and the result (pass/fail).
• Burst pressure test at elevated temperature (NTC 5602 – for high‑temperature applications) – we perform the burst pressure test at the service temperature (e.g., 100 °C, 200 °C) to evaluate the reduction in pressure capacity due to the temperature. We report the burst pressure at the elevated temperature and the derating factor.
• Burst pressure test for plastic and composite components (NTC 5603 – for polymer materials) – we perform the burst pressure test at a slower rate (e.g., 1 MPa/min) to account for the viscoelastic behavior of polymeric materials. We report the burst pressure and the failure mode.
• Hydrostatic pressure test with volume change measurement (NTC 5604 – for detecting volumetric expansion) – we measure the volume of water required to pressurize the test item to the test pressure. An excessive volume change may indicate a loss of stiffness or a potential weakness. We report the volume change (in mL) and the test pressure.

Pressure Cycling and Fatigue Testing – Evaluating Resistance to Repeated Pressure Cycles

Pressure cycling and fatigue testing evaluate the resistance of a component to repeated pressure cycles, simulating the conditions of start‑up, shut‑down, and pressure fluctuations that occur during service. This test is essential for determining the service life of components that are subject to cyclic pressure loads, such as pressure vessels, pipelines, and valves.

• Pressure cycling test (ISO 19879 / NTC 5610 – for pipes, tubes, and fittings) – we subject the test item to repeated pressure cycles (e.g., from 0 to the maximum operating pressure, or from 10 % to 100 % of the maximum operating pressure) at a specified frequency (e.g., 1 to 5 Hz) for a specified number of cycles (e.g., 10,000 to 100,000 cycles). The test item is inspected for leakage, deformation, or fatigue cracking. We report the number of cycles, the pressure range, the frequency, and the result (pass/fail).
• Fatigue pressure test (ASME BPVC Section VIII / NTC 5611 – for evaluating the fatigue life) – we perform a series of pressure cycling tests at different pressure amplitudes (e.g., 30 %, 50 %, 70 %, 90 % of the design pressure) to construct an S‑N curve (pressure amplitude vs. cycles to failure). The fatigue limit (the stress below which failure does not occur) is determined. We report the S‑N curve, the fatigue limit, and the predicted service life.
• Pressure cycling at elevated temperature (NTC 5612 – for high‑temperature applications) – we perform the pressure cycling test at the service temperature (e.g., 100 °C, 200 °C) to evaluate the effect of temperature on the fatigue life. We report the fatigue life at the elevated temperature.
• Pressure cycling with fluid contamination (NTC 5613 – for simulating real‑world conditions) – we add contaminants (e.g., solid particles, water, or corrosive agents) to the test fluid to simulate the effect of contamination on the pressure cycling life. We report the fatigue life under contaminated conditions.
• Pressure cycling with hold time (NTC 5614 – for evaluating the creep‑fatigue interaction) – we include a hold time (e.g., 10 minutes) at the maximum pressure during each cycle, to simulate the combination of pressure cycling and creep. We report the creep‑fatigue life and the failure mode.

Long‑Term Durability and Creep Rupture Testing – Evaluating the Performance under Sustained Pressure

Long‑term durability and creep rupture testing evaluate the resistance of a component to sustained pressure over extended periods, simulating the conditions of continuous service. These tests are essential for predicting the service life of components that are subject to constant pressure loads, such as pipelines, pressure vessels, and hoses.

• Creep rupture test (ASTM D2992 / ISO 1167 / NTC 5620 – for pipes and hoses) – we subject the test item to a constant internal pressure (typically 30‑50 % of the burst pressure) at a specified temperature (e.g., 23 °C, 60 °C, 80 °C) for a specified duration (e.g., 100, 500, 1000, or 5000 hours) until failure occurs. The time to failure is recorded. We report the creep rupture time, the applied pressure, the temperature, and the failure mode.
• Long‑term pressure holding test (NTC 5621 – for evaluating the seal integrity) – we pressurize the test item to the maximum operating pressure and hold the pressure for a specified duration (e.g., 24 hours, 100 hours, 1000 hours). The pressure is monitored for any drop, and the item is inspected for leakage and deformation. We report the pressure stability and the condition of the item.
• Creep strain measurement (NTC 5622 – for evaluating the dimensional stability) – we measure the deformation (e.g., the diameter change, the length change) of the test item during the creep rupture test. The creep strain (in %) and the creep rate (in %/hour) are calculated. We report the creep strain and the creep rate.
• Creep rupture test at different temperatures (NTC 5623 – for the temperature dependence) – we perform the creep rupture test at different temperatures (e.g., 23 °C, 60 °C, 80 °C, 100 °C) to evaluate the effect of temperature on the creep rupture life. We report the creep rupture life at each temperature and the activation energy.
• Creep rupture test under corrosive environment (NTC 5624 – for the corrosion‑creep interaction) – we perform the creep rupture test in a corrosive environment (e.g., with a salt spray, with an acidic solution, or with a corrosive gas) to evaluate the combined effect of corrosion and sustained pressure. We report the creep rupture life and the corrosion‑creep interaction.

Leak‑Tightness and Seal Integrity Testing – Evaluating the Sealing Performance under Pressure

Leak‑tightness is a critical requirement for all pressure‑containing components. Our leak‑tightness tests evaluate the ability of seals, joints, and closures to prevent leakage under static and cyclic pressure, using a combination of pressure holding, bubble detection, and tracer gas methods.

• Pressure holding test for seals and joints (NTC 5630 – for gasketed and bolted joints) – we pressurize the test assembly (e.g., a flange joint) to the specified test pressure and monitor the pressure for a specified duration (e.g., 1 hour). A drop in pressure indicates a leak. We report the pressure drop and the leak rate.
• Bubble leak test (ASTM E515 / NTC 5631 – for detecting local leaks) – after pressurizing the test item with air, we apply a soap solution or a bubble‑forming solution to the seal area. The formation of bubbles indicates the presence and the location of a leak. We report the leak location and the severity of the leak.
• Helium leak test for hermetic seals (ASTM E493 / NTC 5632 – for high‑sensitivity leak detection) – we pressurize the test item with helium (or use a helium leak detector) and measure the helium leak rate (in mbar·L/s). We report the leak rate and the pass/fail status.
• Seal compression and recovery test (ASTM D395 / ISO 815 / NTC 5633 – for evaluating the long‑term sealing performance) – we measure the compression set (the permanent deformation) of the seal material after it has been compressed for a specified time at a specified temperature. A high compression set indicates a loss of sealing force. We report the compression set and the sealing performance.
• Leak‑tightness test after pressure cycling (NTC 5634 – for the fatigue‑induced leakage) – we perform a leak‑tightness test (using the pressure holding method or the helium leak method) after the pressure cycling test to evaluate the effect of the cyclic loading on the sealing integrity. We report the leak rate after cycling and the change in the leak rate.

Environmental and Aging Effects on Pressure Resistance – Evaluating Long‑Term Durability

The pressure resistance and durability of materials can change over time due to thermal aging, UV exposure, chemical attack, and environmental exposure. Our environmental and aging tests evaluate the long‑term stability of the pressure performance, ensuring the reliability of the product over its service life in the diverse Croatian climate (coastal, continental, and mountainous).

• Thermal aging effect on pressure resistance (ASTM D573 / ISO 188 / NTC 5640 – for the heat‑aged materials) – we age the material in an oven at a specified temperature (e.g., 70 °C, 100 °C) for a specified duration (e.g., 7, 14, or 28 days), and then we perform the burst pressure test or the pressure cycling test. The residual burst pressure and the remaining life are reported.
• UV aging effect on pressure resistance (ASTM G154 / NTC 5641 – for the outdoor‑exposed materials) – we expose the material to UV radiation (UVA‑340) and condensation cycles for a specified duration (e.g., 500 hours), and then we perform the pressure resistance test. The burst pressure after UV exposure and the change are reported.
• Chemical exposure effect on pressure resistance (ASTM D543 / NTC 5642 – for the chemically exposed materials) – we immerse the material in various chemicals (e.g., mineral oil, 10 % HCl, 10 % NaOH, or a solvent) for a specified duration (e.g., 7 days), and then we perform the pressure resistance test. The burst pressure after chemical exposure and the compatibility are reported.
• Humidity and moisture effect (NTC 5643 – for the moisture‑exposed materials) – we condition the material at a high‑humidity environment (e.g., 40 °C, 95 % RH) for a specified duration (e.g., 7 days), and then we perform the pressure resistance test. The burst pressure after humidity exposure and the moisture uptake are reported.
• Freeze‑thaw effect (NTC 5644 – for the cold‑climate applications) – we subject the material to repeated freeze‑thaw cycles (e.g., -20 °C to +20 °C) and then we perform the pressure resistance test. The burst pressure after the freeze‑thaw cycles and the effect are reported.

Complementary Tests – Materials, Corrosion, and NDT for Integrity Assessment

To provide a comprehensive assessment of the pressure resistance and to ensure the long‑term reliability of the component, we complement the pressure tests with material characterization, corrosion testing, and non‑destructive testing (NDT).

• Hardness testing (ASTM E18 / NTC 5650 – for verifying the material strength) – we measure the hardness (Rockwell, Brinell, or Vickers) of the component material to verify its strength and to detect any localized softening or hardening that could affect the pressure resistance. We report the hardness values and the uniformity.
• Corrosion testing (ASTM G31 / NTC 5651 – for evaluating the corrosion resistance) – we perform corrosion tests (e.g., immersion test, salt spray test) on the component material in the process fluid (or a simulant) to evaluate the corrosion rate and the type of corrosion, which can affect the pressure resistance. We report the corrosion rate (in mm/year) and the corrosion type.
• Ultrasonic thickness measurement (ASTM E797 / NTC 5652 – for detecting wall thinning) – we use ultrasonic testing (UT) to measure the wall thickness of the component at multiple points, to detect any thinning caused by corrosion or erosion. We report the thickness profile and the minimum thickness.
• Radiographic testing (RT) – ASTM E94 / NTC 5653 – for detecting internal defects) – we perform radiographic testing (X‑ray or gamma‑ray) on the welds and the critical sections of the component to detect internal defects (cracks, porosity, inclusions). We report the RT results and the defect classification.
• Dye penetrant and magnetic particle inspection (ASTM E165 / NTC 5654 – for surface defect detection) – we perform dye penetrant inspection (for non‑ferromagnetic materials) and magnetic particle inspection (for ferromagnetic materials) to detect surface cracks and other discontinuities. We report the location and the size of any defects.

Test Report and Recognition in the Croatian Industrial, Energy, and Manufacturing Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (pressure pumps, pressure transducers, leak detectors, NDT equipment, and thermal chambers) and traceability to international standards (NIST, PTB). Our test reports are issued in English (with a Croatian summary available on request) and include:

• Full identification of the test item (component type, material, dimensions, design pressure, and manufacturer).
• Detailed description of the test methods applied (ASTM/ISO/ASME/HRN EN/NTC standards, test pressure, duration, temperature, and medium).
• Numerical results: burst pressure (MPa), proof pressure (MPa), fatigue life (cycles), creep rupture time (hours), leak rate (mbar·L/s), pressure drop (kPa), and property retention after aging (%).
• Graphical data: pressure vs. time curves, S‑N curves, creep rupture curves, and pressure drop vs. time curves.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (ASME BPVC, EN 13445, HRN EN ISO 1402, and the requirements of the HZN, Ministarstvo gospodarstva, and Državni inspektorat).
• Photographs of the test setup, the item before and after the test, and the NDT images.
• Recommendations for design improvement, material selection, and quality control measures to achieve the required pressure resistance and durability.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98‑3 Guide.

These reports are fully accepted by the Hrvatski zavod za norme (HZN) for the verification of product conformity, by the Ministarstvo gospodarstva i održivog razvoja for industrial and energy compliance, by the Državni inspektorat for market surveillance, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of pressure equipment and components. Additionally, we offer consulting services for the design of pressure‑resistant systems, the selection of appropriate materials, and the implementation of pressure safety programs, contributing to the safety, reliability, and competitiveness of industrial operations in the Croatian market, from the oil refineries and power plants to the manufacturing and construction sectors.