a) Wrapping application shall not be performed when environment condition humidity ratio max 85% and pipe temperature must kept 3 C degree above dew point.
2. Surface preparation
Before the wrapping work applied, the grease ,dirt ,moisture ,water and other adhesive materials shall be removed from its surface.
a) Eliminate sharp projections,if any
b) Completely clean and eliminate surface deposits(scalling, rust, dirt, contaminants and foreign matters ,etc.)from the surfaces ,using hand tools or power tools(disc, sander, wire brush, scraper, surface preparation hammer, etc)
c) Splatter residue,flux,mill scale,rust,and other contaminants shall be cleaned /removed by blast cleaning in accordance technical specificion documents requested.
d) After surface proparation,the dust and abrasive materials attached to the steel pipe suface shall be removed .and being affected with damp,rust formation or secondary pollution shall be prevented .The steel pipe after surface preparation shall be applied within 4 hours ;If it is over 4 hours or rust is formed again on pipe surface,the surface prpartion work shall be carried out again .
e) Stop wapping work in the open air under the weather conditions of rain,snow,fog,sand form,noticeable wind,etc.
Note:STOP SURFACE PREPARATION AND APPLICATION WORK IN ANY OF THE FOLLOWING CASES:
a) Ambient temperature is lower than 5℃,or higher than 40℃.
b) Steel surface temperature is lower than 3℃ over the dew point.
c) Relative humidity of air is greater than 85%.
3. COATING APPLICATION
3.1 The cold applied coating system shall be applied by hand or more preferably by using a
hand-wrapping machine capable of maintaining even, constant tension across the width of
the coating. The hand-wrapping machine shall be equipped with take up spindles to remove
and wind the separator sheet as the coating is applied to the pipe. The use of gloves is highly
recommended.
3.2 The coating system shall be applied to the primed pipe in a spiral configuration.
The wrapping process shall start at a minimum of 4 inches (10 cm) beyond the cutback edge
of any existing coating and start on the downside of the pipe. The release liner should be removedjust prior to the application of the coating to the primed pipe surface. This will prevent contamination of the high tack adhesive.
3.3 The coating system shall be applied under hand or machine tension that will result in a
smooth, wrinkle free coating. The minimum overlap width shall be 1" (25 mm). Particular attentions should be afforded while coating over the girth weld area, to prevent wrinkles in the coating.
3.4 When the outside pipe diameter is greater than 12" (30 cm), the ditch conditions dictate or
required by end-user specifications; if necessary ,a Polyken 955 outer wrap shall be spirally applied over the GTC coating for mechanical protection. A minimum overlap of 1" shall be used
and the Polyken 955 outer wrap shall be applied to achieve a uniform smooth application.
The end of the outer wrap spiral shall be cut on the downside at the 3 or 9 o`clock position
3.5 The coating shall not be exposed for a long period of time .
5.Repair
5.1Coating system defects founded,should be on mark ,indicate and timely repaired .
5.2Remove the burr ,dust before repair work.
5.3For large leakage winding or damaged pipeline coating layer which is exposed ,will remove damaged coating firstly ,and use appropriate width tape spiral winding to protect damaged area .
5.4 The repair material should be wrapped extend at least 50mm from each side of previous wrapping level .
