Preventing inadmissibly high overpressures in process plants in the operational malfunctions is an important safety aspect and an integral part of the design. Purely mechanical pressure relief devices, and especially safety valves and/or rupture disks, are often used as the ultimate safety measure.
For the design of these overpressure safeguards, precise knowledge is required of the processes to be secured, the assumed malfunctions and blow-off cases and the regulations and calculation rules to be complied with.
The range of services offered by the weyer group in the context of the overpressure protection design incorporates the entire path from determination of the blow-off cases and mass flows to selecting the suitable overpressure protection. It goes without saying that we also take two-phase blow-off cases into consideration in accordance with the currently applicable calculation rules.
The cases that cause maximum permissible excess pressure in parts of process engineering production systems to be exceeded can be very diverse, but are always generated by the excessive input of energy into the system under consideration.
These can be due to excessive exothermic reactions, but also to parts of the plant being unintentionally shut-off or classic cases of fire, to name just a few. All operational malfunctions in question, and not to forget malfunctions during commissioning, or plant start-ups and shut downs need to be recorded. A structured procedure is available for this purpose.
Following the analysis of the possible malfunctions or non-unusual operating conditions, the cases that cause the highest input of energy into the system are then examined in more detail. This determines which flow rates have to be discharged over the safety valve when the maximum permissible overpressure is achieved.
After the highest volume flow is identified and calculated, the actual design and selection of the safety valve takes place.
Different designs then become available as a result. Not only do the individual safety valve has to be considered, but also the supply and discharge pipes. The pressure loss that occurs from blows offs over a safety valve then plays an important role here.
In summary, it can be said that the calculation of a safety valve on its own only takes up a small part of the design and deliberations concerning the accident. The real task actually involves recording all operational incidents and malfunctions at a plant that cause overpressure in a part of the plant and to evaluate them qualitatively and quantitatively.
Depending on the application, corresponding calculation rules, which are set out in standards, are used. Furthermore, thermodynamic system states can only be represented quantitatively with sufficient accuracy with the help of process simulation.
- Determination of the relevant blow-off cases
- Determination of all relevant substance data
- Selection, design and recalculation of the overpressure safeguards
- Design/recalculation of the downstream systems
- Manufacturer-independent documentation
weyer special: Safety Valves
A central safety aspect in the planning of process engineering plants is the effective prevention of impermissibly high overpressures in the process plants in case of operational disturbances. In many cases this can only be guaranteed by the installation of safety valves – or more generally – mechanical overpressure protection…Download weyer special here