Fires produce four major outputs: gases, flames, heat, and smoke. The materials involved in the fire will determine the combination of these four outputs. For example, crude oil will produce a very dark thick smoke cloud, and ethylene does not produce much smoke but has a very large flame.
The Nowatec methodology for PFP of oil and gas facilities involves a unified probabilistic approach to structural fire assessment and optimal design of passive fire protection on offshore topsides. The methodology was developed by integrating:
- QRA techniques
- Fire and explosion models
- Heat transfer models, and
- Non-linear structural analysis methods
The main effects of the hydrocarbon fires on topside steel structures are thermal expansion, reduced elastic modulus, and yield stress and creep. Thermal expansion begins at the ignition moment and due to the fact that different structural members will be heated differently (different exposure and surface/mass ratio), it will vary from one structural component to another. Thermal expansion results in member axial forces and bending moments.
Design of Passive Fire Protection and the implementation into the structural design is carried out by Nowatec for clients’ development projects. Typical scope of work and deliverables include:
- Global nonlinear structural fire consequence analysis of a topside including effects of Passive Fire Protection (PFP) using FATHS/USFOS modelling and in-house developed KFX/Ls-Dyna methodology. Strengthening of primary structures when required.
- Local nonlinear structural fire consequence analysis including the effects of PFP on e.g. critical equipment and pipe supports using KFX/Ls-Dyna interface.
- Modification of design and implementation of PFP into drawings and CAD models.