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Butt Wrap Instruction
Abstract
The Butt & Wrap joint consists of plain‐ended pipes and fittings, prepared, aligned and laminated with
glass fiber reinforced resin. The pipe ends are adjacent end to end, aligned on the same centerline, and the
joint over wrapped with layers of resin impregnated glass fiber. Before work on laminated joint is started,
all necessary equipment for completing the procedure must be available. Ensure that the pipes are
maintained with joint faces held tightly together without offset. Material should be prepared before lay‐
up.
Material
‐ Glass fiber mat
Chopped strand mat
Multi axial mat(+45/‐45/90)
‐ Resin
‐ Cobalt
‐ Catalyst
‐ Aerosil
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Butt Wrap Instruction
Preparation
Pipe or Fitting: Preparation and lay‐up process should be done carefully to ensure that product meets specifications. It is important to prepare materials before lay‐up process. Grinding the surface of pipes or fittings to be laminated is necessary before starting lamination. Grinding length of pipes or fittings depends on the diameter (DN) and pressure class (PN) of the pipes (lamination width+20) which are to be joined. The grinded length at least should be 20 mm longer than lamination length found in butt wrap tables. It should be taken care on oil and fat free tools and handling. Ends of the pipe should be clean and smooth. Remove the dust from grounded area with a clean, non‐fluffy rag or brush to obtain a clean and roughened bonding surface.
Glass fiber mat: Cut sufficient amount of mats in accordance with attached lamination table for each joint. Remember fabrics must be kept clean and dry before lay‐up.
Chopped Strand Mat Multi axial Mat
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Butt Wrap Instruction
Resin: Resin is liquid which is responsible for bonding between layers and pipes or fittings. The color of this liquid is light yellow without any additives. The shelf life of pure resin is normally between 5‐6 months which would be achieved in cool and dark area. Mix resin with sufficient amount of cobalt of 1% solution. In the case of using vinyl ester resin, DMA of 10%
solution also should be added. The procedure guide of sufficient amount of resin and accelerator will be delivered with resin. Mix sufficient amount of catalyst with accelerated resin at 25 (± 1) °C to achieve suitable geltime .Geltime should be adjusted with considering time needed for lamination process. For example geltime might be adjusted between 20 to 25min for pipe diameter smaller than 30inch, and for pipe diameter larger than 30inch at least 30min would be preferred. Use correct mixing ratios of resin and catalyst. Using excess catalyst can effect on laminate properties and make a brittle discolored laminate, while insufficient catalyst results uncured laminates (the minimum amount of catalyst is 1%). Stir resin and catalyst for 1 minute to ensure they are mixed well. Curing system must be according to data sheet of resin. The ambient temperature is very important and effect on geltime range. Gel time will be shorter, in temperature higher than 25°C.
Putty: Aerosil powder should be added to resin mixed with cobalt solution. After having a good mixing, add enough catalyst to the mixture.
Lamination Procedure
To start lamination process, put pipes or fittings ends to be joined, adjacent to each other. Apply putty on the gap between ends of the pipes or fittings to fill it and provide a flat surface.
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Butt Wrap Instruction
Let putty cured and then remove all lumps from the surface by rasp to obtain smooth surface with no nubs and pits.
Cover surface of the pipes or fittings with a thin layer of resin, to make bonding between first layer of mat and pipe or fitting surface. The first layer should be chopped strand mat. The laminates used for butt wrap joint contain chopped strand mat for the first and final layer and the other layers used in between are multi axial fabric (45/45/90). Please note that third axis of fabric(90 degree roving) should be in axial direction.
DBT (+45/‐45/90) for joining pipes
Special care is necessary for the first layer of lay‐up and make sure there is no air under layer by perform a thorough roll out to provide good adhesion. Use clean tools for laminating with no cured resin on the roller surface to prevent air interruption. Apply layers after the previous layer completely wet out and then roll out from the center towards the edges. Apply the layers from large width to small like a pyramid.
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Butt Wrap Instruction
After putting each layer, rotate next layer 90 degree to prevent overlap the edges of the layers.
Lamination might be applied only on exterior side of pipes or on both sides (interior and exterior) refer to the butt wrap specification. When lamination finished cover the lay‐up area by a thin layer of resin.
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