LLENTAB sandwich panels - Inspection and maintenance
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LLENTAB sandwich panels –
Inspection and maintenance
This document addresses those in Interventions in sandwich panels
charge of maintenance of buildings with Any interventions, such as making holes and
sandwich panels made of painted suspending panels, must be carried out in a
galvanized steel. It offers advice on what way so that a negative effect on the bearing
to pay attention to during inspections capacity and stability is prevented. When
and provides recommendations on when planning such measures, please contact a
and how to carry out maintenance of the professional structural engineer.
panels.
Hot-dip galvanizing
LLENTAB sandwich panels The colour-coated plate with a thickness of
LLENTAB AB manufactures and assembles steel 0.5 or 0.63 mm features a hot-dip galvanized
buildings and structural frames used in hall steel core. For thin sheet metal, Z275 g/m2 is
buildings. The company develops, designs and applied on both sides.
delivers primarily total solutions that include pillars,
roof trusses, high trapezoidal plates, roof and wall Because zinc coating corrodes at a much
plates, sandwich panels, studs and fittings slower pace than steel, hot-dip galvanized
complemented with object-specific accessories steel protects the painted sheet steel against
and materials. These operation, maintenance and rust over a very long time.
inspection instruction cover LLENTAB Sandwich
Panels. Hot-dip galvanizing protects the steel in two
ways.
Sandwich panels constitute insulating wall – By creating a barrier that prevents humidity
elements made up of painted, hot-dip galvanized and oxygen from reaching the steel surface.
steel plates and insulating mineral wool core. The – By offering cathode protection against
company buys pre-painted sheet steel and scratches, impacts, cut edges, etc.
mineral wool from different suppliers. The sheet
metal and mineral wool insulation are glued with Paint coating
polyurethane glue in our production facilities in Thanks to treatment of the sheet steel with
Kungshamn, Sweden. The wall elements can be different paint systems, the surface takes on
adapted to different needs by varying the properties that can withstand different types
appearance with regard to thickness, surface of environmental stress and meet varying
coating and pattern. quality requirements. These operation and
maintenance instructions include the
Sandwich panels offer a long service life. polyester coatings offered as standard in the
Properly maintained, they retain their distinctive LLENTAB range. For more detailed
properties for a very long time. More details on information on the various coatings and
the panel coating and its properties can be found specific considerations to pay attention to
in the documentation from the sheet steel when e.g. repainting the panels, please refer
supplier, which is available from LLENTAB. to the documentation from the relevant sheet
steel supplier.
2013.02-04 – Operation and maintenance – Sandwich panels
LLENTAB AB Box 104, SE-456 23 KUNGSHAMN, Sweden Tel +46 (0)523–79000 Fax +46 (0)523 31120 Corp. ID 556302-5484
VAT No. SE556302548401 Pg 52 89 34-3 Bg 653-9373 E-mail info@llentab.seMaintenance and inspection Surface finishes with thin coats of paint are
A decision to select sandwich type gable/wall more sensitive to scratches and corrosion
elements in itself constitutes an important step for than high-build coatings. This is an especially
keeping future costs for maintenance of the important consideration in marine
property at bay. Basically, the products require environments and in areas and settings with
very little maintenance. Inspection and pollution.
maintenance can be performed by your own staff,
or this work can be entrusted to specialized Two measures of service life
companies. Regular inspections and maintenance For pre-painted sheet steel, it is common to
are prerequisites for low maintenance costs. Done differentiate between two different kinds of
properly, the sandwich panels and the coating will service life: aesthetic and functional. In a
offer an extended service life. normal environment and depending on the
type of paint applied, an undamaged
Factors that affect the service life surface coating will offer an aesthetic
The environment in which the building is set is service life of 10-20 years.
decisive for the aging of the panel paint work;
however, durability differs between different paint More specific data is also presented in the
systems and between identical colour shades. data sheets provided by the sheet steel
Sun rays, the elements and proximity to the sea supplier. This life time can be extended by
are other factors that cause the paint coat to age, applying regular inspections and
while it is also affected by airborne pollution. maintenance.
The sun affects aging of the paint finish in two Aesthetic service life: represents a
ways: The paint coat ages on one hand as a result measure of time until the paint coating has
of the UV rays, and on the other as a result of heat changed to such a degree that the
absorbed from the sun. As a result, the choice of appearance no longer meets the require-
colour affects the service life; light colours last ments placed upon the finish. The degree of
longer, while darker ones have slightly shorter colour change that is considered acceptable
durability. The service life also depends on for a sheet steel coating depends on who
whether the product is used as a wall or roof. Even judges the change and on which building
the point of the compass and the roof slope affect the sandwich panel has been mounted on.
the service life. Roofs with a gentle slope facing
south are, for example, more affected by exposure Functional service life: represents the
to the sun than those facing to the north. time until which the sheet steel can no
longer meet its bearing capacity or protect
The service life of the paint coat also depends on the insulating layer it was designed to
the environment in which the sandwich panel is protect in the first place. This time varies
used in. Sheet steel close to the seaside is often depending on the type of coating used and
more exposed to air saturated with salt. This even more importantly in what kind of
reduces the service life compared to sheet steel environment the panels/sheet steel is used.
plates used inland. Additionally, industrial
effluents and traffic exhausts affect the service life
of the surface coating.
Damage to the paint coating reduces the
protection against environmental impacts. This
can cause corrosion. By quickly attending to even
minor damage, it is possible to extend the service
life of the surface coating.
2013.02-04 – Operation and maintenance – Sandwich panels
LLENTAB AB Box 104, SE-456 23 KUNGSHAMN, Sweden Tel +46 (0)523–79000 Fax +46 (0)523 31120 Corp. ID 556302-5484
VAT No. SE556302548401 Pg 52 89 34-3 Bg 653-9373 E-mail info@llentab.seAging of paint coating Cleaning
The paint coating will change over time. For Usually the rain is sufficient to keep the
polyester and PVDF paint systems, the evolution external surface of the panels clean. Any
of aging can generally be described in four deposits of dirt that do not disappear when it
phases: rains can be washed off using a soft brush
and water. Take special care of areas not
exposed to rain where dirt and deposits are
not washed away.
In areas with air pollution, it may become
necessary to use a mild detergent and water
(standard washing-up detergent or an
industrial detergent) to clean the panels.
1 2 3 4
Cleaning advice
Phase 1 • Stronger solutions than those recommended
New sheet steel. can damage the paint. Dose according to the
manufacturer’s recommendations.
Phase 2 • Rinse thoroughly until all detergent residue
Adhesive residue is visible on the surface and has disappeared.
appears as chalking, causing the surface to • Avoid organic solvents/abrasive cleaning
appear lighter. The paint coat is still intact; agents.
however, it is thinner.
• Apply the cleaning solution from bottom to
Remedy: If chalking is disturbing, it can be washed top. Rinse from top to bottom.
off. • Carry out cleaning carefully. Excessive
washing will have the opposite effect.
Phase 3 • High-pressure cleaning is not
The primer starts to be visible. The top paint coat recommended as this may cause water to
has partly eroded. penetrate the structure.
Remedy: Following cleaning, the existing coating
can be repainted. Touch-up painting
If the paint finish has suffered minor
Phase 4 scratches, these can be remedied by touch-
The primer and top paint coats have partly up painting. This involves using small paint
disappeared and the metal surface is exposed. brush to only apply paint on scratched
areas. Use an air-drying paint type. Since it
Remedy: Following cleaning and removal of loose can be expected that the applied paint will
paint flakes, prime with wash primer and apply a change in colour over time and take on a
finishing coat. shade slightly different from the colour
applied at the factory, it is important to only
Reconditioning of the surface coating apply paint where necessary.
Reconditioning of the paint coat may become
necessary in order to:
• Clean the surface
• Touch up minor damage
• Deal with corrosion attacks
• Repaint the entire surface
2013.02-04 – Operation and maintenance – Sandwich panels
LLENTAB AB Box 104, SE-456 23 KUNGSHAMN, Sweden Tel +46 (0)523–79000 Fax +46 (0)523 31120 Corp. ID 556302-5484
VAT No. SE556302548401 Pg 52 89 34-3 Bg 653-9373 E-mail info@llentab.seCorrosion Painting
Do as follows to deal with corrosion damage: Use these rules as a guideline:
1. First sandy or scrape off all loose paint and 1 a) If the zinc layer has vanished, first
corrosion residue. Dull the original paint coat in prime the surface with a zinc-rich primer.
the immediate area. 1 b) If the paint has disappeared, but the
2. If the edges appear to have red rust, sand or zinc layer remains undamaged, prime the
sand-blast the area until all red rust has been surface with a wash primer.
removed and the metal surface is clean. 2. Then apply a finishing coat of top paint.
3. Perform cleaning using an alkaline degreasing A finishing coat of paint can also be directly
agent, e.g. 5% caustic soda with a washing-up applied on old paint after cleaning and
detergent added. having established good adhesion.
4. Apply a zinc-rich anti-corrosive primer on the
cleaned surface. All metal surfaces to be touched up or
5. Apply a coat of top paint and also on the painted should be dry and free from grease
dulled surface. and dirt. To reduce the risk of different
colour shades, thoroughly mix the paint.
Dealing with corroded edges Avoid painting in direct sunlight and do not
In normal environments, panel edges will paint at temperatures below +5°C when
usually not corrode. However, in especially using solvent based paint or under +10°C
aggressive environments the edges could for water-based paint. Relative humidity
corrode, and this should be addressed in order should not exceed 80%.
to keep the panels intact.
Proceed according to steps 1-5 above. For Check beforehand that the old paint coat
corroded edges, it is especially important that has proper adhesion! Remove loose paint
the paint fully covers the cut edge (in a cross- and other residue with a scraper and steel
sectional view, the applied coat of paint should brush. Carefully clean corroded surfaces
have a form similar to that of the sulphur tip at with a steel brush or using sand-blasting.
the end of a match). Perform cleaning using an alkaline
degreasing agent, e.g. 5% caustic soda with
a washing-up detergent added. Rinse with
Repainting
water and allow to dry.
Colour changes, peeling, corrosion or simply a
Use a paint brush, roller or spray gun. When
decision to change colour are common reasons
touching up small areas, choose a small,
for repainting a metal surface. Select a paint
soft paint brush.
type system depending on the surface and any
damage. Repainting of exterior sheet steel
should always be carried out in a professional
manner and with proven colour systems. The
selection of a colour system for repainting
depends on the composition of the original paint.
Suppliers of repainting systems have
instructions for how repainting should be carried
out with different colour systems.
Repainting polyester coated sheet metal
Generally, thorough cleaning of the metal is
sufficient. Please refer to the previous section.
Loose paint that does not come off during
washing should be removed by hand.
2013.02-04 – Operation and maintenance – Sandwich panels
LLENTAB AB Box 104, SE-456 23 KUNGSHAMN, Sweden Tel +46 (0)523–79000 Fax +46 (0)523 31120 Corp. ID 556302-5484
VAT No. SE556302548401 Pg 52 89 34-3 Bg 653-9373 E-mail info@llentab.seRepainting unexposed polyester Annual inspection
The procedures for repainting differ depending on To maintain an effective maintenance regime,
whether the object is sheet steel that needs to be annual inspection of the building’s panel/steel
repainted as a result of long-term outdoor exposure surfaces is necessary.
or new sheet steel that has not been subject to
exposure outdoors for a longer time. Polyester paint At the annual inspection, check and correct
has a slight wax content and as such presents a as follows:
surface finish that makes it easier to process. On the – Corroded edges, cut edges at panel
other hand, the wax content can make it difficult to joints. Corrosion can spread if not treated
achieve good adhesion when repainting sheet metal in time.
that has not been exposed outdoors. This wax finish – The condition of the surface/paint
in aged polyester/Nova coatings has eroded naturally coating, indications of chalking, change in
through exposure to the elements. With this in mind, colour or surface cracking, especially
it is important to first find out where the object has where rain can’t reach to rinse clean the
been used before it is repainted. The following sandwich panels. Make a judgement of
constitutes general recommendations for repainting whether washing, cleaning, attending to
new or unexposed sheet metal. corroded edges, touch-up painting or
1. Wash clean with an alkaline cleaning agent using repainting is required.
a sponge, e.g. Scotch Brite or similar – Rubbish in the gutters. Blocked gutters
2. Rinse with water increases the risk of corrosion and as such
the risk of water leaking into the building.
3. Apply a coat of primer Clean out rubbish in the gutters as it will
4. Apply one or two coats of top paint bind moisture and corrosive substances.
The supplier of the repaint product can provide – Damage to the paint coating increases
detailed recommendations for correct pre- the risk of corrosion. Consider touch-up
processing of the material. painting, repainting or replacing the panel
depending on the scope and type of
damage.
2013.02-04 – Operation and maintenance – Sandwich panels
LLENTAB AB Box 104, SE-456 23 KUNGSHAMN, Sweden Tel +46 (0)523–79000 Fax +46 (0)523 31120 Corp. ID 556302-5484
VAT No. SE556302548401 Pg 52 89 34-3 Bg 653-9373 E-mail info@llentab.seYou can also read
