Pressure Testing / Hydrostatic Testing in Belgium
Pressure testing, including hydrostatic and pneumatic testing, is a mandatory proof test used to verify the structural integrity and leak-tightness of pressure equipment, piping systems and vessels. It is a critical step in commissioning new installations and requalifying in-service equipment.
What is Pressure Testing?
Pressure testing is a proof test method used to verify the mechanical integrity and leak-tightness of pressure-containing equipment by subjecting it to a pressure higher than its maximum allowable working pressure (MAWP). The test pressure is typically 1.25 to 1.5 times the design pressure, depending on the applicable code and the type of test. There are two principal types of pressure test: hydrostatic testing, which uses water (or another liquid) as the test medium, and pneumatic testing, which uses air or an inert gas such as nitrogen.
Hydrostatic testing is the preferred and most commonly specified method because water is essentially incompressible, meaning that any failure during the test releases relatively little stored energy compared to a pneumatic test. The equipment is completely filled with water (ensuring that all air is vented), pressurised to the specified test pressure, held at that pressure for a defined duration (typically 30 minutes to 2 hours depending on the code), and then visually inspected for leaks, deformation or other signs of distress. Pneumatic testing is used when hydrostatic testing is impractical — for example, when the equipment cannot support the weight of water, when water contamination is unacceptable, or when the system cannot be adequately drained and dried. Pneumatic tests carry a significantly higher risk and require additional safety precautions due to the stored energy of compressed gas.
LCNDTEST performs pressure testing services across Belgium for new fabrications, modifications, repairs and periodic requalification of pressure equipment. We provide the complete service including test preparation, pressurisation equipment, calibrated pressure gauges, test supervision and comprehensive documentation in compliance with PED, ASME and EN standards.
Test Methodology
The pressure testing process begins with thorough preparation. A detailed test procedure is developed that specifies the test medium, test pressure, hold time, acceptance criteria, safety perimeter and the sequence of pressurisation steps. All temporary closures (blinds, test flanges, caps) are installed and rated for the test pressure. Pressure gauges are calibrated and traceable, with a range typically between 1.5 and 4 times the test pressure for optimal accuracy. Vents are positioned at high points to ensure complete air removal during filling for hydrostatic tests, and drains at low points for subsequent drainage.
For hydrostatic testing, the system is filled with clean water (with corrosion inhibitors if necessary for carbon steel equipment) and all air is vented. The pressure is raised gradually in defined steps, typically to 50%, 75% and 100% of the test pressure, with holds at each stage to check for leaks and allow for thermal stabilisation. Once the full test pressure is reached, it is maintained for the specified hold duration while the system is visually inspected at all joints, connections and welds. Any observable leakage, pressure drop (beyond that attributable to temperature variation) or visible deformation constitutes a test failure.
For pneumatic testing, additional safety measures are mandatory: the pressurisation rate is controlled and slower, a preliminary leak test at a lower pressure (typically 10-15% of the test pressure) is performed first, and personnel are excluded from the immediate vicinity during the hold at full test pressure. After successful completion of the pressure test, the system is depressurised in a controlled manner, temporary closures are removed, and a comprehensive test report is issued documenting all parameters, observations and the test result.
Industrial Applications
- Hydrostatic testing of new pressure vessels, heat exchangers and columns prior to commissioning
- Pressure testing of new and modified piping systems in petrochemical plants, refineries and chemical facilities
- Periodic requalification testing of pressure equipment in accordance with Belgian and European regulations
- Leak testing of flange connections, valve assemblies and mechanical joints
- Pneumatic testing of systems where water is not permissible (oxygen systems, instrument air, cryogenic piping)
- Proof testing of repaired or altered pressure equipment before return to service
Advantages of Pressure Testing
- Definitive proof of structural integrity and leak-tightness under conditions exceeding normal service pressure
- Mandatory regulatory requirement for pressure equipment under PED, ASME and EN codes
- Detects leaks at joints, connections and welds that may not be identifiable by other inspection methods
- Provides documented evidence of equipment fitness for safe operation at the rated working pressure
- Applicable to a wide range of equipment types, sizes and pressure ratings across all industrial sectors
Reference Standards
PED 2014/68/EU • EN 13445-5 • EN 13480-5 • ASME Section VIII Div.1 • ASME B31.3 • EN 12952 • EN 12953
Frequently asked questions
Hydrostatic testing uses water (or another liquid) as the test medium and is the preferred method because water is essentially incompressible, meaning any failure releases relatively little stored energy. Pneumatic testing uses air or an inert gas such as nitrogen and is employed when hydrostatic testing is impractical, for example when the equipment cannot support the weight of water, water contamination is unacceptable, or the system cannot be adequately drained. Pneumatic tests carry significantly higher risk due to the stored energy of compressed gas and require additional safety precautions.
Pressure testing is required at several stages: before commissioning new pressure vessels, piping systems and heat exchangers; after repairs or modifications to pressure-retaining components; during periodic requalification of in-service pressure equipment as mandated by Belgian and European regulations; and when required by fabrication codes such as PED 2014/68/EU, EN 13445, EN 13480 and ASME Section VIII. The test demonstrates that the equipment can safely withstand pressures exceeding its maximum allowable working pressure.
Pressure testing in Belgium is governed by the European Pressure Equipment Directive (PED 2014/68/EU) and its Belgian implementation, along with harmonised design codes including EN 13445-5 for unfired pressure vessels, EN 13480-5 for metallic industrial piping, EN 12952 and EN 12953 for boilers, and ASME Section VIII and ASME B31.3 where applicable. These standards define the test pressure, hold time, acceptance criteria, safety requirements and documentation to be produced.