Hydraulic burst test of the pressure reducing valve

Hydraulic Burst Test for Pressure Reducing Valves – Validating Overpressure Safety for Brazilian Systems

As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised hydraulic burst testing services for pressure reducing valves (PRVs) used across Brazilian oil and gas, petrochemical, water supply, power generation, and industrial processing systems. A hydraulic burst test subjects the valve body, bonnet, and sealing components to a controlled internal pressure exceeding the maximum allowable working pressure (MAWP) to verify that the valve can withstand short‑term overpressure events without rupture or leakage. Our procedures strictly follow ABNT NBR standards, ASME B16.34, API 598, ISO 5208, and EN 12266, and are recognised by ANP (oil and gas regulator), ANEEL (electricity sector), and INMETRO for equipment safety certification. We issue detailed, traceable burst‑test reports that provide compelling evidence of structural integrity, helping Brazilian project owners, EPC contractors, and valve manufacturers meet both local regulatory requirements and international project specifications.

Valves and Components We Regularly Test for Hydraulic Burst

Our high‑pressure test bay accommodates pressure reducing valves of various sizes, materials, and pressure ratings. Typical test articles include:

• Direct‑acting spring‑loaded PRVs – for low‑pressure water, air, and gas applications
• Pilot‑operated PRVs – for high‑pressure natural gas, steam, and process fluid systems
• Hydraulic and pneumatic PRVs – for industrial automation and mobile equipment
• Stainless steel and carbon steel body valves – in sizes from DN 15 to DN 600 and pressure classes 150 to 2500
• Valve assemblies with flanged, threaded, or welded ends
• Reconditioned or repaired valves – requiring re‑certification after overhaul
• Prototype and custom‑engineered valves – for new product qualification

Hydrostatic Proof Test (Shell Strength Verification) – Pre‑Burst Integrity Check

• Test pressure and hold duration – We first perform a hydrostatic shell test at 1.5 × design pressure (or as specified by the applicable code, e.g., ASME B16.34 requires 1.5 × MAWP for shell test). The valve is filled with water, all internal air is vented, and the pressure is gradually increased using a computer‑controlled hydraulic pump. The test pressure is maintained for a minimum of 5 minutes (or 15 minutes per API 598 for larger valves) while we monitor the body and all joints for any visible leakage or weeping.
• Leakage detection and measurement – We use a calibrated pressure transducer (accuracy ±0.1 %) and visual inspection with white tissue paper applied to all joints, flanges, and bonnet seals. Any drop in pressure exceeding 2 % of the test pressure, or any visible wetting, is recorded and classified as a leakage failure. For high‑risk applications, we also employ a helium tracer or acoustic emission monitoring to detect micro‑leaks that are not visible to the naked eye.
• Pressure‑time recording – Our data acquisition system records the applied pressure versus time, generating a profile that reveals any sudden pressure drops or spikes. We include this chart in the final report as objective evidence of the valve’s ability to hold pressure without deformation or seal failure.
• Dimensional verification after proof test – We measure critical external dimensions (face‑to‑face, flange thickness, and stem extension) before and after the test using calibrated callipers. Any permanent change greater than 0.2 % of the original dimension is reported as a sign of yielding, which automatically disqualifies the valve from passing the proof stage.

Hydraulic Burst Test – Ultimate Pressure Capacity Determination

• Incremental pressure ramp to failure – Following a successful proof test, we continue to increase the internal water pressure at a controlled rate (typically 1‑2 % of expected burst pressure per second) until the valve either ruptures, develops a through‑wall leak, or reaches the maximum capacity of our test system. This ultimate burst test determines the actual safety margin above the rated MAWP, following the guidelines of ASME PTC 25.3 and ISO 5208 for shell burst testing.
• Burst pressure and location documentation – We record the peak pressure achieved before failure (the burst pressure) and note the exact location and type of failure (e.g., body rupture, bonnet fracture, flange splitting, or gasket extrusion). High‑speed video recording (frame rate 1,000 fps) is used to capture the failure event, enabling frame‑by‑frame analysis of fracture initiation and propagation. This footage is invaluable for root‑cause analysis and design improvement.
• Minimum burst ratio calculation – We compute the burst ratio as: Burst Ratio = Burst Pressure / MAWP. The result is compared to the code‑required minimum (e.g., ASME B16.34 requires a minimum burst ratio of 4:1 for carbon steel and 3:1 for stainless steel, depending on design). Our report clearly states whether the valve meets or exceeds the required burst ratio, and we provide the actual measured value with its measurement uncertainty (±2 % of reading).
• Failure mode classification – We classify the failure as ductile (yielding with visible necking), brittle (sudden fracture with minimal deformation), or gasket/seal extrusion. For ductile failures, we measure the percentage of circumferential and axial elongation; for brittle failures, we examine the fracture surface using stereomicroscopy to identify any casting defects, inclusions, or weld flaws. This information helps Brazilian valve manufacturers improve their foundry and welding procedures.

Post‑Burst Leakage Test – Seat and Seal Integrity Evaluation

• Pressure decay test after burst – In cases where the valve body does not rupture completely but develops a leak path, we perform a pressure‑decay leakage test to quantify the internal seat leakage. The valve is re‑pressurised to its rated pressure, and the pressure drop over a 5‑minute period is measured with the valve in the closed position (if closure is still possible). This follows API 598 and ISO 5208 “rate of leakage” criteria for soft‑seated and metal‑seated valves.
• Water and air leakage combination – For valves that fail the hydraulic integrity check, we also conduct a low‑pressure air test (at 0.6 MPa) using soap‑solution to pinpoint the precise leak location. The leakage rate in bubbles per minute is recorded and compared to the allowable limit per the applicable standard; any visible bubbles indicate non‑conformity.
• Seat deformation measurement – For valves whose seats remain intact, we measure the seat diameter and roundness using a bore gauge before and after the burst test. Any ovalisation or reduction in seat diameter greater than 0.1 mm is reported, as this would affect sealing performance in service.
• Gasket and O‑ring inspection – After the test, we remove the bonnet and inspect all internal seals for extrusion, cold‑flow, or thermal degradation. Photographs are taken, and the condition is rated as “intact”, “partially deformed”, or “failed”. This assessment is critical for ensuring that the valve can maintain a tight shut‑off even after a pressure excursion.

Hydrostatic Burst Testing with Thermal Soak – Simulating Elevated Service Conditions

• Temperature‑conditioned burst test – For valves intended for high‑temperature service (e.g., steam lines, hot oil systems), we offer burst testing at elevated temperatures. The valve is heated in a circulation oven to the service temperature (e.g., 250 °C or 400 °C) and held for 2 hours to achieve thermal equilibrium. The burst test is then performed with heated water or a high‑temperature thermal fluid, following ISO 7507 and API 6D annex requirements for temperature‑dependent burst verification.
• Material property shift assessment – We compare the burst pressure at elevated temperature to the value obtained at ambient temperature; a significant reduction (> 20 %) may indicate that the material’s creep strength or fracture toughness has degraded. We include both values and the reduction factor in our report, helping Brazilian operators select valves with adequate thermal derating.
• Cyclic thermal‑pressure preconditioning – For valves that experience daily thermal cycling, we optionally perform 10 low‑pressure cycles (0‑50 % MAWP) at temperature before the burst test, to simulate service ageing. This preconditioning may reveal thermal fatigue effects that lower the actual burst capacity – a critical consideration for Brazilian petrochemical plants with frequent start‑up and shut‑down cycles.

Report Acceptance & Compliance with Brazilian Regulatory and Industry Standards

All hydraulic burst tests described above are conducted under our ISO/IEC 17025:2017 accreditation, using calibrated pressure transducers, certified dead‑weight testers, and traceable dimensional instruments. Our final burst‑test reports provide: a complete test plan with reference standards, pre‑test and post‑test dimensional records, proof‑test pressure‑time curves, burst‑test pressure‑time curves with peak value and failure mode, high‑speed video stills, leakage assessment results (if applicable), and a clear conformity statement against the required burst ratio and code tolerances. We also supply an uncertainty budget for pressure and dimension measurements. These reports are universally accepted by ANP for offshore and onshore pipeline valve qualification, by ANEEL for hydroelectric and thermoelectric plant pressure equipment, by INMETRO for valve type‑approval, and by Brazilian EPC contractors and insurers for project risk assessments. Bilingual (Portuguese/English) versions are available to facilitate submissions to local authorities and to ensure clear communication with your engineering, procurement, and quality teams. With our rigorous hydraulic burst testing, you can confidently demonstrate that your pressure reducing valves possess the structural margin required to withstand emergency overpressure events, thereby enhancing safety, reliability, and compliance in Brazilian installations.