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Jining Qiangke Pipe Anticorrosion Materials CO.,Ltd

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Home > News > Anti-corrosion Construction Technology For inner wrap tape,outer wrap tape

Anti-corrosion Construction Technology For inner wrap tape,outer wrap tape

2019-06-26

1. General

The wrapping work shall not be done when it is rainy ,dusty, freezing, or in such weather as will adversely affect the wrapping work,(except where protective facilities and sufficient protections are provided)

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. Liquid Adhesive Application

a)The coating system shall ALWAYS be applied with GF 1027 liquid adhesive.

b) The adhesive is applied to the pipe steel surface by spraying, brushing or using a paint roller to a wet thickness of no less than 2 mils (51 microns) and no greater than 3 mils (76 microns). The adhesive shall be thoroughly mixed prior to application on pipe. The

adhesive container shall remain covered when not in use.

c)the brushing time should be control within 4 hours between the pipe surface treatment. During brush primer ,pipe surface should be free from damp and pollution. If the pipe surface rust return,should be re-pre-cleaned.

d) The primer should be applied uniformly, without any sags,floods,runs,drips,bare spot and over spray, such as leakage brush, clot , streaming. The primer coat DFT shall not be less than 25-50micron(1-2mils, depending on ambient conditions)


4. COATING APPLICATION

4.1 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.

4.2 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 removed just prior to the application of the coating to the primed pipe surface. This will prevent contamination of the high tack adhesive.

4.3 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.

4.4 When the outside pipe diameter is greater than 12" (30 cm), the ditch conditions dictate or

required by end-user specifications; if necessary ,a GF 955 outer wrap shall be spirally applied over the GTC coating for mechanical protection. A minimum overlap of 1" shall be used

and the GF 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

on the pipe.

4.5 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 ,brush primer 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 .


6. COATING INSPECTION REPAIR


6.1 Peel strength

Use a knife cut width 10mm,length greater than 100mm tape layer until pipe body .

Then use spring balance with a 90degree direction to pull ,speed not more than 300mm/min,peel strength should get no less than 25N/cm.

The test should be done 24 hours after tape wrapping .


6.2 The coated field joint shall be electrically inspected for holidays with an adjustable

Electronic Detector.


The travel rate of the holiday detector shall not exceed 1 foot (30 cm) per second, nor shall an activated holiday detector remain stationary over the coated

field joint.

6.3 Coated field joints that are damaged prior to lowering in and backfilling shall be repaired

immediately. The damage area shall be cleaned and the abraded portions trimmed level.

6.3.1 Small or Pinhole type Holidays in the GF GTC shall be repaired by applying the

GF 1027 liquid adhesive over the holiday area an when dry to touch, using the GF GTC, start at the 9:00 o`clock position on the coated pipe surface and cover the repair area a

minimum of 1 inch on all sides of the repair. A complete wrap of 1-1/2 revolutions shall be

made around the pipe with coating always cut on the downward side of the pipe. If outer wrap is

being used apply a layer of the outer wrap over the repaired area.

6.3.2 For larger Holidays or where the GF GTC damage exposes the steel pipe, remove

the damaged coating and smooth edges before the repair is made. If the damaged area is

less than 4" fill the area with a patch of GF GTC and cover the repair with an overlay

of GF GTC material. If the repair area is larger than 4" the area shall be primed with

GF 1027 liquid adhesive then spiral wrapped with GF GTC using a 1" minimum

overlap covering the repair area a minimum of 1" on all sides of the repair. If outer wrap is

being used apply a layer of the outer wrap over the repaired area.

8.0 BACKFILL

8.1 Backfill material shall contain NO large or sharp stones that could damage the wrap

coating system during backfilling.

8.2 Walking on the coated pipeline shall not be allowed.


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Morgan Chen

Mr. Morgan Chen

Email:

chinapipetape@163.com

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Tel:86-0537-6400111

Fax:86-0537-6400222

Mobile Phone:+8618863769877

Email:chinapipetape@163.com

Address:No.3 Jiamei Road ,Jiaxiang Industry Park, Jining, Shandong

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