Static pressure resistance strength testing service

Static Pressure Resistance Strength Testing Service – Accredited ISO/IEC 17025 Pressure Integrity and Structural Assessment for the Croatian Market

Static pressure resistance strength is a critical performance parameter that evaluates the ability of components, systems, and materials to withstand internal or external static pressure without leakage, deformation, or structural failure. This property is essential for ensuring the safety, reliability, and regulatory compliance of products such as pressure vessels, pipelines, valves, pumps, heat exchangers, hydraulic systems, pneumatic components, and packaging materials used in the oil and gas, chemical, pharmaceutical, power generation, automotive, and construction industries. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo gospodarstva i održivog razvoja, the Državni inspektorat, the Agencija za zaštitu okoliša (AZO), and the Carinska uprava enforce strict quality, safety, environmental, and pressure equipment regulations aligned with EU directives (such as the Pressure Equipment Directive PED 2014/68/EU) and HRN EN (Croatian standards based on European norms), the accurate evaluation of static pressure resistance is essential for product certification, type testing, factory acceptance, supplier qualification, and import-export processes. Our laboratory offers a comprehensive static pressure resistance strength testing service, applying standardized methods such as hydrostatic testing, pneumatic testing, burst pressure testing, and pressure cycling testing to verify the integrity and safety of a wide range of pressure-containing components and systems. 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, equipment validation, and market access in Croatia and the European Union.

Test Samples and Equipment We Regularly Examine

Our laboratory receives a wide variety of pressure-containing components and systems for static pressure resistance testing. Typical samples include:

• Pressure vessels and tanks – storage tanks, reactors, separators, and accumulators for gas, liquid, and chemical storage.
• Piping systems and pipelines – welded and seamless pipes, fittings, flanges, and pipe joints for oil, gas, water, and chemical transport.
• Valves and actuators – ball valves, gate valves, globe valves, control valves, and pressure relief valves.
• Pumps and compressors – centrifugal pumps, positive displacement pumps, and compressors for various fluids.
• Heat exchangers and boilers – shell-and-tube heat exchangers, plate heat exchangers, and fire-tube boilers.
• Hydraulic and pneumatic components – cylinders, accumulators, hoses, and fittings for fluid power systems.
• Packaging and containers – drums, cans, bottles, and flexible packaging for hazardous and non‑hazardous materials.
• Prototype and new designs – submitted by manufacturers for validation of pressure resistance before series production.
• Field‑retrieved components – for failure analysis and remaining life assessment.

Hydrostatic Pressure Testing – Evaluating Resistance to Internal Pressure with Water

The hydrostatic pressure test is the most common and widely accepted method for evaluating the pressure integrity of pressure vessels, piping, and other components. The test item is filled with water (or another incompressible fluid) and pressurized to a specified test pressure (typically 1.5 times the design pressure) for a specified duration, and the item is inspected for leakage, deformation, or rupture. Our procedures follow the requirements of the Pressure Equipment Directive (PED) 2014/68/EU, ASME BPVC Section VIII, and the HRN EN standards.

• Hydrostatic pressure test – standard method (ASME BPVC Section VIII / EN 13445 / HRN EN 13445 / NTC 5800) – the test item is filled with water (or a suitable fluid) and pressurized to 1.5 times the maximum allowable working pressure (MAWP) using a hydraulic pump. The pressure is maintained for a specified duration (typically 10 to 30 minutes). The item is inspected for any visible leakage, permanent deformation, or rupture. We report the test pressure, the duration, the temperature of the water, and the result (pass/fail).
• Hydrostatic pressure test with stress measurement (NTC 5801 – for measuring the deformation) – we apply strain gauges to the critical areas of the test item to measure the deformation during the pressure test. The measured strains are used to verify the design and to detect any yielding. We report the pressure-strain curve and the maximum strain.
• Hydrostatic pressure test at elevated temperature (NTC 5802 – for components used in high‑temperature service) – we perform the hydrostatic test at the service temperature (e.g., 100 °C, 200 °C) using a heated pressure test system. The test pressure is maintained at the specified level. We report the test temperature, the pressure, and the result.
• Hydrostatic pressure test with volume change measurement (NTC 5803 – 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.
• Hydrostatic pressure test for pipelines (NTC 5804 – for field testing) – for installed pipelines, we perform a hydrostatic pressure test using a pressure test pump and a calibrated pressure gauge. The test pressure is maintained for a specified duration (e.g., 1 hour) and the pressure drop is monitored. We report the test pressure, the pressure drop (in kPa), and the result (pass/fail).

Pneumatic Pressure Testing – Evaluating Resistance to Internal Pressure with Air or Inert Gas

The pneumatic pressure test uses compressed air or an inert gas (e.g., nitrogen) as the pressurizing medium. This test is often used when the test item cannot tolerate the presence of water (e.g., for electronic components or for components that cannot be dried easily) or when the test pressure is low. It is also used for leak detection, as gas leaks are easier to detect than liquid leaks.

• Pneumatic pressure test – standard method (ASME BPVC Section VIII / EN 13445 / HRN EN 13445 / NTC 5810) – the test item is filled with air or nitrogen and pressurized to a specified test pressure (typically 1.1 times the MAWP) using a compressor. The pressure is maintained for a specified duration (typically 10 to 30 minutes). The item is inspected for leaks (by soap solution or by a pressure decay measurement) and for any permanent deformation. We report the test pressure, the duration, the test gas, and the result (pass/fail).
• Pressure decay test (NTC 5811 – for detecting small leaks) – we pressurize the test item to the specified test pressure and then isolate the pressure source. The pressure is monitored for a specified time (e.g., 5 to 15 minutes). A significant pressure drop indicates a leak. We report the pressure drop (in kPa) and the leak rate (in mbar·L/s).
• Pneumatic pressure test with leak detection by bubbling (NTC 5812 – for localized leak detection) – after pressurizing the test item with air, we apply a soap solution to the joints, welds, and seals. Bubbles indicate the presence and the location of leaks. We report the leak location and the severity of the leak.
• Pneumatic pressure test with tracer gas (NTC 5813 – for high‑sensitivity leak detection) – we pressurize the test item with a tracer gas (e.g., helium or 5 % hydrogen in nitrogen) and use a sensitive gas detector (a mass spectrometer or a hydrogen sensor) to detect even the smallest leaks. We report the leak rate (in mbar·L/s) and the location of the leak.
• Pneumatic pressure test at low temperature (NTC 5814 – for components used in cold service) – we perform the pneumatic test at a low temperature (e.g., -20 °C, -40 °C) to evaluate the effect of low temperature on the material's strength and the sealing integrity. We report the test pressure, the temperature, and the result.

Burst Pressure Testing – Determining the Maximum Pressure Capacity

The burst pressure test is used to determine the ultimate pressure capacity of a component, i.e., the maximum pressure that the component can withstand before it ruptures. This test is essential for establishing the safety margin and the design factor, and it is required for the certification of pressure components under the PED and other pressure equipment regulations.

• Burst pressure test – hydrostatic method (ASTM D1599 / ISO 1402 / NTC 5820 – for pipes, tubes, and hoses) – we fill the test item with water and increase the pressure at a controlled rate (e.g., 10 MPa/min) until the item bursts. The burst pressure (in MPa or bar) is recorded. We report the burst pressure, the failure mode (e.g., rupture, pinhole, or seam separation), and the failure location.
• Burst pressure test – pneumatic method (NTC 5821 – for low‑pressure and large‑volume components) – for large components or for components that cannot be tested with water, we perform the burst pressure test with air or nitrogen, using a controlled pressurization system. The burst pressure is recorded. We report the burst pressure and the failure mode.
• Burst pressure test at elevated temperature (NTC 5822 – 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 the burst pressure due to the temperature. We report the burst pressure at the elevated temperature and the derating factor.
• Burst pressure test with strain measurement (NTC 5823 – for measuring the deformation before rupture) – we apply strain gauges to the critical areas of the test item to measure the deformation and to detect the onset of yielding, which precedes rupture. We report the pressure‑strain curve and the burst pressure.
• Burst pressure test for composite and plastic components (NTC 5824 – for polymer and composite 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.

Pressure Cycling and Fatigue Testing – Evaluating the 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 5830 – 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 5831 – 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 5832 – 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 5833 – 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 5834 – 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.

Leak‑Tightness and Seal Integrity Testing – Evaluating the Sealing Performance under Static 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 pressure, using a combination of pressure holding, bubble detection, and tracer gas methods.

• Pressure holding test for seals (NTC 5840 – 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 for seals and welded joints (ASTM E515 / NTC 5841 – 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 5842 – 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 5843 – 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 for packaging (ASTM D3078 / NTC 5844 – for flexible and rigid packaging) – we test the leak‑tightness of packaging (e.g., drums, cans, and bottles) using a vacuum decay method or a pressure decay method. We report the leak rate and the pass/fail status.

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 5850 – 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 5851 – 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 5852 – 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 5853 – 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 5854 – 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 and Energy 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, etc.) 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 (ASME/EN/HRN EN/NTC standards, test pressure, duration, temperature, and medium).
• Numerical results: test pressure (MPa), burst pressure (MPa), pressure drop (kPa), leak rate (mbar·L/s), number of cycles to failure, fatigue limit (MPa), compression set (%), corrosion rate (mm/year), and hardness (HRC/HV).
• Graphical data: pressure vs. time curves, pressure‑strain curves, and S‑N curves.
• Comparative tables against the values specified by the client or against the limits of the PED 2014/68/EU, EN 13445, HRN EN 13445, ASME BPVC, 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.
• 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 safety and environmental compliance, by the Državni inspektorat for market surveillance, by the Agencija za zaštitu okoliša (AZO) for environmental protection, 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 chemical plants to the power generation and manufacturing sectors.