Technical data

Proper Pipe Preparation for Electrofusion Fittings
For a pipe surface to be properly prepared for electrofusion the outer layer or “skin” of
the pipe should be removed to expose a clean, virgin pipe material. This can be
achieved by using one of several types of approved scraping tools. “Approved”
scraping tools can vary widely between electrofusion manufacturers and they may not
necessarily be a tool that is manufactured by the fitting manufacturer. A few examples
of scraping tools that Central Plastics classifies as “approved” are; a rasp type tool
(Stanley Surform Model 21-296 or equivalent), a metal blade paint scraper, or tools
manufactured specifically for electrofusion scraping. “Approved” simply indicates that
the tool has been qualified by the manufacturer and has been found to perform in a
satisfactory manner under the joining conditions established by the manufacturer.
Wood rasps or metal files are not considered acceptable.
It is very important to note that abrasive materials, such as sandpaper or emory cloth,
should never be used in place of a scraping tool. Abrasive materials have been proven
to be ineffective in the removal of sufficient amounts of surface material needed to
achieve an electrofusion bond and in fact, they have actually been shown to impede
the electrofusion process. This is due to the grit or grit like residue they imbed into the
pipe area being scraped, which in turn acts as a barrier between the pipe and fitting.
The electrofusion process significantly differs from conventional heat fusion. In the
electrofusion process there is very little material movement or melt displacement (i.e.
melt beads). For this reason, any contaminant that is present on the surface of the
pipe will remain sandwiched between the pipe and fitting interface and will ultimately
prevent the two materials from joining. It is also recommended that the “Metal File”
type of rasp not be used as a pipe scraper; as the pipe material is removed with this
type of tool, tends to ball up and roll around on the pipe surface instead of being
cleanly removed and directed away.
Central Plastics Company recommends that a minimum of .007” to .010” of the pipe’s
surface material be removed during the scraping process in order to expose a clean
virgin material. This is approximately the thickness of two sheets of paper. It is impor-
tant that the pipe surface be clean and free from any type of contaminants that may be
spread before scraping begins. Should the pipe surface be contaminated with dirt,
mud or drilling fluids before scraping, plain water may be used to remove the surface
level of these contaminates. It should be noted however, that water cannot be used to
clean the pipe surfaces once the virgin material has been exposed. In those in-
stances a minimum 70% isopropyl alcohol concentration, with no additional addi-
tives, has been found to be highly effective in removing these type of contaminates
and is recommended by Central Plastics as a cleaning agent that can be used before
and after scraping. For applications where a fitting will be moved around on the pipe,
such as a repair application where a coupling will be pushed completely over one end
of the pipe, it is recommended that pipe be scraped for the entire length of the cou-
pling to prevent a clean fitting from being contaminated by unscraped pipe.
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