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TECHNOLOGICAL APPLICATION

In order to comply with these standards the modu- meter of press-bent steel plates (thk = 8 mm for
les structure is made of carbon steel S355 NL for face 1-2-3; 6 mm for face 4), as primary longitudi-
low temperature (-52°C) insulated with EI60 wool nal beams and secondary cross-beams, made of
panels. Flanges, pipes, valve body and control trim carbon steel S355 NL. The roof frame structure is
are in Super Duplex and foam concentrate atmo- composed by a perimeter of press-bent steel pla-
spheric tanks, having maximum capacity 20,500 tes (thk = 8 mm for face 1-2-3; 6 mm for face 4) as
litres, are made in Stainless Steel 316L. well and transverse beams (thk = 6 mm), made of
carbon steel S355 NL.
In the last months Sanco
designed and manufactured The complete structure frame is composed by
press bent steel plates (thk = 6 mm), as corner
“several special water/foam columns and intermediate columns made of S355
deluge system in 14 modules NL. The corrugated steel plates are made of car-
bon steel S355 NL (thk = 6 mm for face 1- 2 ; 4
(S-BRM) suitable to resist mm for face 3-4), and there are a stiffness reinfor-
to an external blast. The fire cement steel S355 NL (thk = 6 mm) and panels
suppression system contained behind S355 NL (thk = 6 mm for face 2; 4 for face
1-3-4). Base frame, cross-beams, roof, structure
in the module S-BRM shall work and corrugated plates, welded together, create a
properly before, during and monolithic structure.
after the blast

In this article is shown the case of the Blast Pro-
of Resistant Module (S-BRM) having dimensions
9.4x3x3 m
(L x W x H), tested by the strongest blast (fig. 1).
S-BRM has been designed to ensure the structure
integrity after a blast load.
When blast occurs, the S-BRM shall have enough
The scope is to verify stress, plastic strain and de- structural strength to withstand the pressure, ho-
formation during in-service condition and subjected wever, permanent deformations are allowed.
to a blast load at the same time. The blast can have
different intensity on the module sides, therefore a On the other hand, elements subjected to plastic
penetration check has been performed on each strain could help the rest of the structure to pre-
of them increasing of 10% the explosion value as serve its integrity, absorbing part of the blast load.
required by customer specifications. After the ex- For this reason, in case small parts of the structu-
plosion the module may deform (deformations not re exceed the yield strengths of the material, the
exceeding 35 mm), but the fire protection system condition is acceptable; it does not mean that the
will continue to operate. structure will collapse.
The dynamic response of the S-BRM structure Due to this, in the blast analysis, the resulted stress
is simulated performing a transitory time-history is compared with 100% of ultimate strength of the
analysis (implicit dynamic analysis). Transport and used material.
lifting phases were also analysed, but not descri- Considering the elongation at break of the material
bed in this article. and a contingency factor, the used failure criteria is
0,1: if the plastic strain exceed the failure criteria, it
The calculation software is “Ansys Mechanical” by means that structure will collapse.
Ansys Company; this software is based on the fini- The following scheme, created by the “Ansys Me-
te elements theory. chanical” software, can be considered the starting
All structures are analysed using FEM (Finite Ele- point to perform calculation and checks. The doors
ment Methods) based on the package 3D model. are not modelled because they are blast certified
The corrugated steel is shaped as “shell” element by the vendor providing the test report.
considering the real dimension and thickness.
Using this method, the properties of the corrugated The dead load, or rather the self-weight of elements
steel are preserved. (e.g. steel frames and corrugated steel plates), is
The complex sections (structure beams, spars and automatically calculated by the software, conside-
columns) are shaped as solid parts to provide a ring a contingency factor (γ ) of 10% that is equal
M
more accurate analysis. to ~17,500 kg.
The mesh sizes are different for various points Pipes, valves, turbine in-line, foam proportioners,
of the structure, in order to perform an accurate foam concentrate tank and accessories are sup-
analysis of the main elements. ported internally by carbon steel racks welded di-
rectly on the floor of the module.
The base frame structure is composed by a peri- Point masses of the furniture are applied on the re-

90 90 Impiantistica Italiana - Luglio-Agosto 2022