High temperature test

A test that verifies whether a test object (e.g. valves, swivels, seals) continues to function properly at high temperature and meets requirements for operability and internal/external leak tightness. Usually testing is done first at ambient temperature, followed by the high temperature phase and a short final test at room temperature.

High temperatures cause, among other things, thermal expansion, additional stresses, and aging/relaxation of sealing materials. Without verification, this can lead to higher operating forces, jamming, and leaks.

Depending on the standard and application. For steam applications, test temperatures up to approximately 400 °C are often used; with heating mats, testing can be done up to 1000 °C.

Yes. Usually a pre-test at ambient, then high temperature and a short final test at room temperature.

Often customer-specific requirements. For Fugitive Emission, high temperature tests are often requested by: ISO 12101, ISO 15848‑1, Shell MESC SPE 77/300, API 622, API 624, and API 641. Customized procedures are possible if they are agreed upon in advance.

Often the end user determines the standard. Deviating or additional requirements can be recorded in a project-specific test procedure, including setpoint, ramp rate, number of cycles, and leak limits.

Generally yes. ITIS is an ISO 17025 accredited testing laboratory and thus a conformity assessment body (CAB).

As an independent organization, we verify whether products, processes, persons, or services comply with legislation, standards, or specifications. Accreditation increases trust and international acceptance; the final acceptance lies with the customer/authority.

Usually suffice: standard/procedure, type of test object, weight/dimensions and desired test temperature.

Yes. The test object must be clean and dry. At high temperatures, paint/oil/dirt can outgas; above ~150 °C it is preferable to test without coating.

For repeatability and to limit gasket effects, we often use welded adapters/test flanges; this is coordinated per project.

Depending on the product, standard, and test objective. Often: thermocouples at fixed measuring points with data logging, pressure sensors, helium mass spectrometer (external leakage), flow meters (seat leakage), and torque/force transducers for operation.

Standards may specify the number of measuring points, stabilization criteria, and accuracies; all equipment is calibrated and traceable.

Yes, provided the method falls within our scope. The current scope is with the RvA; upon request, we will send the link or the certificate. Outside the scope, we test according to the same procedures; the reporting is then not accredited.

Yes. We choose the method per test that suits dimensions, mass, material, desired temperature, and test pressure.

For tests at ITIS, we often use the following techniques:

• Hot-air oven – uniform heating of the entire object; uniform temperature distribution; up to approx. 500 °C.
• Ceramic heating mats – very fast, locally (or fully) applicable heating; efficient for larger objects or complex shapes; up to approx. 1000 °C.
• Induction heating – contactless via a coil and electromagnetic field; fast, well-controllable heating; very suitable for carbon steel.

Control and monitoring:

• PLC-controlled temperature profiles with ramps, dwells, and cooling phases.
• Multiple thermocouples at critical positions, including alarm monitoring to prevent overshoot.
• Recording of temperature and test parameters (upon request as a graph in the test report).

Selection and customization:

The final choice is customized; we advise the best configuration for your object and test purpose. For each test, we align equipment and setup to size, weight, fastening, desired temperature, and environmental requirements.

Heating up according to setpoint from standard/customer requirement; controlled ramps; continuous monitoring; start of measurements as soon as all measurement points have stabilized within tolerance.

Until all prescribed measuring points reach the target temperature and fall within the stabilization criteria; the duration depends on setpoint, standard, and especially the mass/volume of the test object.

Above room temperature up to and including 1000 °C, depending on customer requirements and chosen heating technology.

External: helium (pure or mixture) with mass spectrometer. Internal: usually dry nitrogen. Other media upon consultation.

At a fixed pressure difference and flow direction, using a calibrated flow meter; we test against standard limits or pre-agreed limits.

Yes, often prescribed. We measure torque or force under specified conditions and test against standard or customer limits.

Depending on the standard and configuration; usually multiple cycles.

Threshold values for internal/external leakage and requirements for operability/operating moment; exact values are stated in the standard or project specification.

This is reported as ‘non-compliant’ according to the applicable customer requirements/standard. A retest can usually only take place after corrective measures (e.g. adjusting tolerances or material choice), followed by a full reassessment according to the same test procedure.

Often yes, to determine lasting effects (e.g., relaxation of seals).

Metal housings (carbon steel, low alloy steel, stainless steel, Cr-Mo or nickel alloys) are often suitable depending on temperature, pressure, corrosion, and toughness. The limiting factor is usually in non-metallic parts (elastomers, PTFE/soft seats, some gaskets).

For high temperatures, metal seats and graphite gaskets are often chosen. Maximum temperatures and P-T ratings can be found in standards and datasheets; the lowest limit of housing, bolts, gasket, seat, and actuator is always decisive.

A chart or table that shows the maximum allowable pressure per temperature. Use manufacturer data or standards (including ASME B16.34, EN 12516).

Briefly explained

• Purpose: determine the pressure rating at operating temperature (derating at higher T).
• Source: manufacturer tables or standards per material, pressure class, and connection.
• Components: separate limits for body/bonnet, bolts/flanges, seals and seats; the lowest determines the overall rating.
• Medium influence: some tables apply media/corrosion allowances.

How do you use it?

1. Choose material, pressure class and connection type.
2. Read the max. pressure at the operating temperature.
3. Check additional limits for seat/packing (soft seats often have lower T-limits).
4. Include safety margins and standard/customer requirements; the lowest limit is decisive.
5. If in doubt, follow the manufacturer table for the specific type/serial number.

Important notes

• Values are material- and standard-specific; do not use generic numbers.
• High temperature ⇒ pressure rating decreases (derating).
• Low temperature ⇒ pay attention to toughness/impact requirements (brittle fracture).
• Test pressure ≠ operating pressure: hydro/pneumatic testing follows separate rules and can temporarily exceed the operating rating.

Yes, high temperature tests carry risks.

Main risks and control measures:

• Fire and explosion hazards, especially when testing with methane (ISO 15848‑1, API 622, API 624, API 641); testing takes place in shielded test bunkers.
• Limiting exposure during sniff tests by using robots where possible.
• PPE: flame-retardant/heat-resistant clothing and the correct PPE are mandatory.
• PLC-controlled ramps/dwells and overshoot protection reduce the risk of damage from heating too quickly/too much.

Yes, via the ITIS Cloud Portal (secure livestream). On-site witnessing by arrangement.

That depends on mass/volume, target temperature and profile, standard/procedure, number of thermal cycles and test pressure(s). Heating up and controlled cooling usually take the most time.

Depending on the same factors. For a targeted quote, we would like to receive: product type, weight/dimensions, setpoint(s), standard/procedure, number of cycles, test pressure(s) and internal volume.

The sequence is basically flexible, but ensure that after hydrotesting the test object is fully drained and dried. Residual water degasses at high temperature and can cause seat leakage. The object must be free of dirt, grease, and oil both inside and out; preferably without coating or preservation.

Often yes. Due to thermal expansion, increased friction, and changing material behavior, design and assembly errors become quickly apparent. Rejection rates are relatively high, especially for gaskets, soft seats, and stem seals.

Typical causes: too tight tolerances (seizing/heavy operation), relaxation/aging of seals, exceeding P/T range of soft seats/gaskets, residual grease/oil/moisture.

Approach: correct material and seat selection relative to P-T diagram; tolerances adjusted for expansion; heat-resistant gaskets/graphite or metal seats; sufficient torque margin; clean and dry assembly; controlled ramps and dwells.

Type test: design qualification at high temperature of one representative sample from a design family; the approval applies to sizes/pressure classes within that family. Production test: sample (or 100%) from a batch to verify whether the delivered production meets the requirements.

Choose a type test for a new/modified design, new size or class, new materials or changed sealing materials. Choose a production test for series or project deliveries to verify batch conformity (sample or 100%, according to standard/customer requirement) and for pre-shipment inspections.