Safety-related calculations


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Safety-related calculations

We undertake the calculations for the design of the safety-related system components and, where necessary, also on the basis of safety-related parameters ascertained in our laboratory

  • Design of pressure relief equipment (safety valves, bursting discs)
  • Flow-related calculations for piping networks
  • Computer simulation of disturbance scenarios / dispersion calculations
  • Dimensioning of retention systems
  • Design of covers and throttles to limit mass flow
  • Measures to minimise pressure surges in pipes

In addition, we also carry out dispersion calculations with which we then estimate the consequences of any substance discharge. These calculations are integral to the approval applications that plant operators must submit to the various authorities.

Safeguarding pressure equipment

Where proper safeguarding of pressure vessels is concerned, consilab’s experts assist in careful analysis of the possible causes of increases in pressure. In the event of a disturbance, the mass flow to be discharged from the section of the plant then depends primarily on the identified scenarios. When calculating the dischargeable mass flow, two-phase flows may have to be taken into account. In complex cases, such as when safeguarding reactors, it may be necessary to implement the design based on dynamic simulation calculations. The following specific tasks are processed at consilab:

  • Analysis of pressurization scenarios → more
  • Design of pressure limiting equipment (safety valves/bursting discs/ventilation systems)
    (also for two-phase flow)
  • Calculated verification of supply lines and blow-off lines (also for two-phase flow) → more
  • Design of retention systems → more
  • Recording/logging of pressure limiting and retention equipment in operation

Safeguarding chemical reactors

The target reaction in normal operation is generally very well known. The condition in a reactor can change quickly in the event of a disturbance of the normal operating procedure so that undesired and often unknown reactions occur, which can in turn lead to an unforeseen, rapid increase in pressure above the maximum permissible operating pressure of the reactor.

Any possible fault that cannot be eliminated through sufficient safety-related process control or organizational measures during normal operation should be analyzed in an adiabatic laboratory test with respect to the possible rate of temperature and pressure increase. In doing so, analysis should include not only a blocked exhaust air path, a possible failure of the cooling system or a fault in the heating control system but also, if applicable, incorrect dosing, accumulation, mixing up of input materials, etc. Tests for these purposes are generally carried out in an adiabatic reaction calorimeter, e.g., VSP2. You will work with our experienced experts to determine which tests should be carried out – and how – to attain an optimal data situation to safeguard the plant.

The pressure curve during the reaction as well as the cooling curve can be used to deduce whether the reaction being analyzed is a gas-producing reaction system (gassy system), a vapored system (or vapor-cooled system) or a mixture of both, i.e., a hybrid system.

The test results are also used to determine the maximum temperatures and pressures as well as the temperature gradients (rate of temperature increases) and pressure gradients (rate of pressure increases) required to design a safety valve or bursting disc.

Batch quantities in operation, vessel data, and data obtained from adiabatic analysis in the laboratory can be used as a basis for calculating the required discharge cross-sections as well as for arriving at the probability of a two-phase discharge.

The actual design is usually implemented using the DIERS method according to Leung or in accordance with ISO 4126 Part 10. The roll-up behavior (homogeneous, churn-turbulent, bubbly) of the reaction mixture in the vessel depends on the viscosity, filling level and foaming capacity of the reaction mixture. The mass flow density in the safety valve or the bursting disc is highly dependent on the flow pattern. Distinctions are drawn not only between pure gas flow, pure liquid flow and two-phase flow. Calculation with two-phase flow can be carried out according to the homogeneous equilibrium model (HEM) or homogeneous disequilibrium model in accordance with Diener and Schmidt (HNE-DS).

Assessing the effects of incidents

The effects of incidents must be described in safety reports for plants covered by the extended requirements of the Hazardous Incident Ordinance. Impact assessments must also be conducted as part of land-use planning. These assessments are used in your expert reports by our experts, who are notified as defined in Section 29a of the German Immission Control Act (BImSchG). consilab offers:

  • Source term calculation (release volume flows from leaks, pools, etc.)
  • Dispersion calculation for neutral and heavy gases (VDI 3783, AUSTAL2000)
  • Free jet calculation (explosive cloud, thermal radiation, explosion pressures)
  • Assessment of the effects of fires and explosions

Flow-related calculations

Our experts perform steady-state calculations and dynamic calculations for flow in pipelines. The focus here is on safety-related issues, in addition to optimization tasks. Pressure surges when closing shut-off valves or during quick discharge procedures require careful analysis with the aid of dynamic simulation programs. consilab offers the following specific services:

  • Design of orifice plates and throttles → more
  • Pressure loss calculations (also for two-phase flow)
  • Analysis of pressure surge hazards (e.g. during rapid closure of valves)
  • Optimization of pipeline networks
  • Safeguarding storage tanks
  • Calculation of flow-induced loads on pipelines (reaction forces)
  • Design of gas vents and pressure-relief devices