32
LNG
INDUSTRY
SEPTEMBER
2014
shutdown valves, were invariably constructed frommetal,
despite the fact that it is heavy (e.g. steel is approximately
8 g/cm
3
) and difficult to insulate adequately due to its high
thermal conductivity (steel is between 15 and 50 W/mK,
depending on its grade). Furthermore, even when galvanised,
steel is susceptible to corrosion and pitting and requires regular
repainting.
Specialist composite materials
To overcome these issues, Intertec-Hess GmbH (Intertec)
manufactures products from a proprietary high performance
composite material, comprising inner and outer walls of
long-fibre glass reinforced polyester (GRP) sheets, enclosing a
thermally insulating core (see Figure 1). Single or multiple layers
are used as the basic structural material for the company’s
standard and custom enclosures; many of these are ideally
suited to offshore applications and are available in fire resistant
and explosion proof versions, with explosion proof heating,
cooling or air conditioning systems where appropriate.
The type of GRP composite used by Intertec has multiple
advantages, especially for fixed or floating offshore
installations. It has a weight of only 1.2 g/cm
3
(less than a
quarter than that of steel), yet it has a similar strength and a
rigidity that is well suited to the construction of robust walled
housings with an automated production of single-piece sheets
as large as 3 x 6 m without containing any metal components
that could introduce thermal ‘short-cuts’ between the inner and
outer layers and providing considerable design freedom. The
material is chemically inert and inherently immune to corrosion
from salt spray, as well as being an excellent thermal and
electrical insulator with a high degree of resistance to
UV-induced degradation.
Another advantage of the composite is that the thickness
and constituents of its core insulation can be varied and
multiple layer ‘sandwiches’ can be constructed to secure
application-specific attributes, such as increased load-bearing
capabilities or greater resistance to fire, wind velocity, blast
force or extreme temperatures. For example, Intertec has
supplied air-conditioned analyser containment shelters for
North Sea platforms that are capable of withstanding
300 mbar blast loads, as well as countless shelters for
protecting field equipment in arctic, desert and coastal
conditions.
Case studies
Earlier this year the company provided three protection
shelters for the supervisory control and data acquisition
(SCADA) systems of a new natural gas project on the coast
of the Persian Gulf, where the environmental conditions are
particularly severe. The atmosphere contains corrosive salt,
chlorine and sulfur, combined with extremely high levels of
UV radiation and daytime temperatures as high as 55˚C during
the summer months. Two of the shelters incorporate custom
air conditioning systems with special corrosion-resistant
heat exchangers. The third shelter, which is sited in a remote
location without access to an electricity grid, employs passive
cooling technology to dissipate more than 1 kW from the
solar-powered equipment it houses, ensuring that the internal
temperature is always kept below 35˚C even under worst-case
conditions (see Figure 2).
Another example of the versatility of the composite GRP
construction material can be seen in ‘walk-in’ access
fire-resistant shelters produced for offshore gas production
platforms in the Arabian Gulf. These shelters offer more than
basic fire resistance: their novel layered composite
construction and insulation will keep emergency shutdown
(ESD) control electronics below 60˚C for 120 minutes, even in
the event of a ‘rapid-rise’ hydrocarbon fire (which can reach
over 1100˚C within the first five minutes). The inner and outer
walls of the composite material used for these shelters (see
Figure 3) is formed from GRP, while the internal core uses a
patented combination of special construction techniques and
Figure 3.
These ‘walk-in’ shelters are designed to provide
two-hour fire protection for vital ESD control electronics on
offshore gas production platforms in the Arabian Gulf.
Figure 1.
Double-walled GRP sheets with a PU foam core
combine excellent thermal performance with rigidity.
Figure 2.
This passively cooled shelter was built to protect
a remote-sited SCADA system for a Middle East natural gas
collection project.
