LLENTAB sandwich panels - Inspection and maintenance

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LLENTAB sandwich panels - Inspection and maintenance
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.se
Maintenance 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.se
Aging 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.se
Corrosion                                                                            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.se
Repainting 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.se
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