Fusion Bond ed Epoxy Powder
Each container of epoxy powder is inspected prior to loading into the powder delivery system.
Note: With FBE powder it is advisable to check production material for moisture content and gel time on at least a daily basis. (A high moisture content can cause coating irregularities.
The inspection should also confirm that the epoxy powder is listed on the "Approved IRF".Only powder with current, valid approval shall be used. Batch numbers shall be recorded on all the relevant inspection and laboratory test reports.
Polymers
Each container Polymer shall be inspected prior to loading into the Extruder hopper systems.
Note: With Polymers it is advisable to check for moisture of the pellets every two hours when in production. A simple way to check for moisture is to push your bare hand into the box of pellets. If when you withdraw your hand you find pellets adhering to your skin it is an indication that excessive moisture is present.
The inspection shall also confirm that the Polymers are listed on the "Approved IRF. Only Polymers with current, valid approval shall be used. Batch numbers shall be recorded on all the relevant inspection and laboratory test reports.
Reclaim:
Subject to client approval the amount of reclaim powder applied in any given interval shall notexceed 20 % of the total powder application.
4.6 Coating Appli cation
Powder applic ation
The Fusion Bond Epoxy Powder is applied to the heated pipe using a series of electrostatic spray guns. By balancing the conveyor line speed and the settings of the electrostatics, guns, FBE flow rate and pressure of the material feed the material application is controlled to achieve the correct applied coating thickness. The coating should be continuous over the entire length of each pipe joint. The minimum thickness shall be as indicated in the agreed Project Inspection Test Plan ( ITP.)
Polymer Application
Immediately after the FBE primer, the co polymer adhesive (intermediate coat) is applied. The application shall take place within the gel time window of the FBE to ensure adequate adhesion to the primer. The minimum thickness is as indicated in the agreed project Inspection Test Plan (ITP)
Following the adhesive side extrusion application, the Polyethylene or Polypropylene topcoat is applied by side extrusion process in a single sheet layer over the adhesive. Both polymer layers are applied with an overlap. During the application of the polymers, a pressure roller is applied against the pipe behind the polymer sheet that presses against the the applied
sheet that eliminates air bubbles and ensures intimate contact between the layers. The minimum thickness of the PE/PP is as indicated in the agreed project Inspection Test Plan (ITP).
PE Application
PP Application
Responsibilities:
The coating line Supervisor shall be responsible for the strict control of all the heating to maintain the correct pipe preheat temperatures in accordance with line speed, pipe diameter and material preheat requirements. Information required to perform this function is received from
the coating line controller. He shall also be responsible in ensuring that the task is conducted in the safest possible manner.
The QC, inspector/auditor shall be responsible for monitoring of the coating parameters.
The Powder booth foreman shall be responsible for maintaining the application, gun settings, flow rates of materials, feed line pressures for the particular line speed and pipe diameter and the electrostatics.
The coating line controller shall be responsible for all line activities for material coating line. This includes maintaining the correct line speed and pipe preheat by monitoring inspection reports and control room instrumentation and that all powder coating and Polymer extrusion parameters are maintained.
On completion of coating the coated pipe is progressed through a water quenching tunnel where copious amounts of water is sprayed onto the finished coating and to cool the pipe for safe handling.
4.3 COOLING BOARDS & INSPECTION
Immediately after cooling the coated pipes are transferred to an outgoing padded pipe rack where the pipes are positioned on end cleaning rotators The end cleaner brushes remove the coatings from the cut back areas of the pipe. The entire coating surface is visually inspected for coating quality and detrimental coating defects. The cutback distance at both ends of the pipe are also checked..
After end cleaning and visual inspection the entire coated surface of each length of pipe is inspected for holidays using a high voltage (pulse type) holiday detector previously set and calibrated to the correct voltage. The circumferential search electrode shall maintain intimate contact around the entire circumference of the coated pipe at all times. The voltage shall be checked and recorded hourly. The travel speed for holiday detection shall be at a rate of 300 mm per second maximum. Any holidays or surface defects shall be clearly marked and recorded on the agreed Coating Application Report.
Holiday Detector
The coating thickness is usually determined by taking the 4 equidistant measurements (3 on the body and 1 on the weld) at the lead end middle and tail end of each pipe (a total of 12 measurements). The measurement shall be conducted using an electromagnetic thickness gauge. Records of the thicknesses shall be recorded on the agreed Coating Application
Report
Thickness Check
Responsibilities
Cooling board supervisor shall be responsible for ensuring that the holiday detection of each pipe is carried out in a correct manner and at the correct voltage. Also he shall ensure that the pipe cutbacks are correctly established and that the pipe ends and pipe internals are sufficiently cleaned. He shall also be responsible in ensuring that the task is conducted in the safest possible manner.
The QC, inspector/auditor shall be responsible for visual inspection of the coating and physical testing. He shall also monitor the holiday detection and cut back length. He shall also be responsible for calibration of the holiday detection equipment prior to the start of each shift.
Load out Tally man, shall be responsible for checking the pipe identity and maintaining pipe trace ability on the computerized pipe tracking system. He shall also ensure that coating thickness checks are being carried out and being recorded correctly for each pipe.
4.4 REPAIRS:
Repairs to the coatings shall be carried out in accordance with an approved Repair Procedure. Coated pipes that cannot be repaired shall be rejected, stripped and re coated. Unacceptable pipe shall be marked up with Red/White hazard tape and recorded on the NCR system.
Typical Repair Procedure
This procedure describes methods that enable repairs to be made to the 3 Layer Coating System after the completion of the in line process. This method statement describes three repair methods and is presented in three parts:
Part 1: - Repairs using a Hand Held Extruder Gun. Part 2: - Repairs using Melt sticks.
Part 3: - Repairs using Sleeves. Part 1: Hand Extruder
There are two types of repair
Type A: - Repairs to the total three layer system. Type B: - Repairs to the Polyethylene layer only.
TYPE A - The defective area shall be removed and the surrounding sound coating shall be abraded to allow a "key" for the system repair material. An area of at least 50 mm diameter will be removed to facilitate the effective cleaning of the steel and FBE. The repair area substrate shall then be gently preheated to remove surface moisture.
The FBE shall then be feathered using abrasive paper at the FBE/substrate interface.The exposed substrate shall then be mechanically roughened, masking tape (if used) and surface dust shall be removed and two pack epoxy material applied. Mixing/application of the two pack epoxy shall be in accordance with manufacturer's data sheet and shall be applied to the prepared area using a clean brush (or pallet knife if compound is used). After the Epoxy coating has cured, Polymer (as used in the parent coating)
is then extruded from a hand held extruder onto the repair area taking care that no air entrapment at the FBE/Polymer interface occurs. The Polymer is extruded in layers to bring the repair thickness up to and in excess of the parent coating thickness. Once cool, the repair shall be blended with the parent coating, any excess Polyethylene removed by scraper and/or rasp. The completed repair areas shall then be holiday detected.
TYPE B - The damaged Polymer is removed using a chisel and the surrounding area roughened using a mechanical burr. Extruded Polymer (as used in the parent coating) is then introduced into the prepared area. Once cool, the repair area shall be blended with the parent coating and any excess removed by scraper and rasp. The completed repair areas shall then be holiday detected. For repairs of Pinholes and minor defects to the Polymer coating repairs shall be by using melt sticks.
Any loose or defective coating shall be removed from the damaged area and any sharp edges eliminated. The area and adjacent coating is then cleaned thus removing all foreign materials.
The prepared area is then preheated, at the same time the end of the melt stick is heated such that it becomes “glossy”. The molten adhesive is then spread onto the damaged area.
On hardening, the repair shall be smoothed with a rasp such that the repair area becomes flush with the existing parent coating.
Part 3: WPC Sleeves
Heat shrinkable sleeves shall be used as an alternative for larger repairs. The defective coating area shall be removed from the defect area. The full circumference around the pipe at the defect locality shall be thoroughly cleaned of surface dust, grease, oil etc using Xylene or bio -degradable emulsifier. The full circumference of the pipe surface where the sleeve is to be applied plus 100 mm either side shall be abraded.
The steel substrate at the defect area shall be mechanically roughened and the repair area warmed slightly to drive off surface moisture. On completion of preparation a two pack epoxy shall be applied to the steel surface. Mixing and application of the two pack epoxy shall be in accordance with the manufacturer's data sheet. The epoxy shall be applied to the prepared area using a clean brush (or pallet knife if compound used).
When the Epoxy compound has cured, a filler shall be applied to the repair area to increase the coating thickness at the repair area location. A shrink sleeve shall be prepared to the correct dimensions and made ready for application. When prepared the protective release plastic shall be removed from the mastic coating and the sleeve centred over the repair area. The sleeve shall be loosely wrapped around the pipe with ends overlapping by approximately 75-100 mm. The overlap shall be in approximately the 11 o’clock position of the pipe with the edge of the overlap pointing downwards. The ends shall be aligned evenly.
until the reinforcing fabric is visible or the thermo-chromic paint has changed colour. With a gloved hand, the closure shall be patted down firmly to the pipe and any wrinkles or bubbles shall be smoothed out. This procedure shall be repeated moving across the closure until the opposite end is completed. Whilst the closure is still hot and soft, a hand roller shall be used to smooth out any trapped air and the edges and corners shall be firmly bonded down.
The heating procedure shall continue around the pipe by heating in the centre of the sleeve and continue towards the edges. Occasionally the adhesive flow shall be checked by using finger pressure. After the sleeve has shrunk and is still hot and soft, use a hand roller over the sleeve to remove any entrapped air. Re heating of the sleeve is permissible to complete the repair.
Responsibilities:
The repair foreman shall be responsible for coating repairs and shall ensure the correct equipment and repair method is used for coating repair. He shall also be responsible in ensuring that the task is conducted in the safest possible manner.
QC, Inspector/auditor shall be responsible for checking the preparation and the completed repairs.