Thermal Hazard Testing Services

Process Pulse works with a specialist partner laboratory for the calorimetric testing itself. Our role is the engineering around it: reviewing the chemistry and plant conditions, deciding which materials, reaction steps and conditions need testing, specifying the test programme, and turning the measured data into a thermal risk assessment with clear operating limits and safeguard recommendations.

This keeps the test programme focused on the scenarios that matter for your plant — cooling failure, overdosing, loss of agitation, extended holds — rather than a generic test menu, and means the person interpreting the data is the same engineer who will carry the findings into your HAZOP, LOPA or relief design.

Screening uses milligram samples in a Differential Scanning Calorimeter (DSC), usually in sealed high-pressure crucibles, to find whether a material or reaction mixture decomposes exothermically, at roughly what temperature, and how much energy it releases. Screening is run on raw materials, reaction mixtures at key stages, isolated intermediates, products, and distillation or drying residues — residues are a frequent source of surprises because unstable by-products concentrate there.

Decomposition energy is a first indicator of severity. The UN Manual of Tests and Criteria, for example, uses an exothermic decomposition energy of 500 J/g as a screening threshold below which a substance need not be assessed further for explosive properties. Materials above that level need closer attention before they are heated, dried or stored in bulk.

A DSC onset temperature is not a safe operating temperature. The detected onset depends on scan rate and instrument sensitivity, and in a large, poorly cooled vessel decomposition can self-accelerate from well below it. Older rules of thumb such as keeping 100 K below the DSC onset are not reliable on their own for long hold times or large inventories — which is why screening results are followed by TMRad and TD24 assessment where the margin is small.

Adiabatic calorimeters — such as accelerating rate calorimeters and low-thermal-inertia vent sizing instruments — let a sample self-heat with almost no heat loss, recording temperature and pressure as a runaway develops. They give the adiabatic temperature rise, TMRad as a function of temperature, the self-heating and pressure rise rates, and the amount of permanent gas generated.

That data decides how an emergency relief system must be sized. The DIERS methodology distinguishes vapour systems, where boiling tempers the runaway; gassy systems, where non-condensable gas drives pressure; and hybrid systems with both. Each needs a different sizing method, and getting the classification wrong can under-size a relief device by a large factor. Tests intended for relief sizing are run at low thermal inertia (a phi factor close to 1) so that results represent the plant vessel directly.

Test results are only useful once they are turned into operating decisions. Comparing the process temperature, MTSR, the maximum technical temperature and TD24 places each reaction step in a criticality class, and the class points to the appropriate protection: operating limits and alarms, a controlled dosing strategy with interlocks on temperature, agitation and feed, emergency cooling, quench or dump systems, and correctly sized relief.

Those measures then feed the wider hazard studies. Measured thermal data makes HAZOP discussions of cooling failure, overdosing and loss of agitation concrete, and gives LOPA and SIL determination a defensible basis for the consequence severity and the time available for operator response.