WORLD LEADER IN LARGE DIAMETER PIPE MANUFACTURING TECHNOLOGY
3-LAYER POLYETHYLENE COATING SYSTEMS
PRD CO., INC. .1321 W.WINTON AVE. HAYWARD CA . 94545 USA PH (510) 782 7242 . FAX (510) 887 5639
http://www.prdcompany.com
e-mail:
[email protected]
3-LAYER POLYETHYLENE COATING SYSTEMS CONTENTS A- COATING LAYERS B- TECHNICAL DATA OF THE PIPES C- COATING CAPACITY D- SYSTEM COMPONENTS E- COATING PROCESS F- PROCESS PARAMETERS G- PROCESS H- TYPES OF WRAPPING I- CAPACITIES OF THE MACHINES AND EQUIPMENTS J- INSPECTIONS AND TESTS K- REPAIR
PE COATING PROCESS
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PRD Pipe Manufacturing Systems
INTRODUCTION : Pacific Roller Die Co. Inc. supplies complete plants for polyethylene coating of pipes. PRD’s technology provides pipe manufactures the best solution for their specific needs. PRD gives service to their customers from layout design to operation. 3-LAYER PE COATING : 3-Layer PE Coating provides high quality protection of steel line-pipes to be used for transportation of natural gas, oil and water. 3-Layer PE Coating has great influence on the service life of pipeline.
A-COATING LAYERS 1- Fusion Bonded Epoxy ( Primer ) used for corrosion protection. 2- Copolymer Film ( intermediate layer – adhesive ) used for bonding between fusion bonded epoxy layer and polyethylene layer. 3- Polyethylene Film ( top layer ) used for mechanical resistance to damages may arise in the handling, transportation and laying of the pipe. There are two main advantages of the coating by combination of multi-layers : 1- Excellent adhesion and chemical resistance properties obtained by fusion bonded epoxy ( first layer - corrosion protection ). 2- Strong physical and mechanical performance obtained by extruded adhesive copolymer ( intermediate layer ) and polyethylene ( top layer ). B-TECHNICAL DATA OF THE PIPES Pipe Diameter Wall Thickness Pipe Length
: 200 mm – 2500 mm : 3 mm – 25 mm : 6 – 16 m.
C-COATING CAPACITY 250 m2 / hour ( optionally 400 m2 / hour )
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Optional Units 1- Gas-Fired Flame Heating Furnace for pipe heating to the temperature of 220 degree C 2- Chromate Application for surface treatment prior to coating process after blast cleaning 3- Phosphate Treatment Unit 4- Vacuum Cleaning and Magnetic Plate Unit 5- Primary Inspection Station 6- Solvent Cleaning Unit 7- Inspection Station after blast cleaning process 8- Final Inspection Station D-SYSTEM COMPONENTS 1- Pipe Entry Racks - Let-Down Arms 2- Pipe Conveyors for Cleaning ( Blast ) Line 3- Flame Heating Furnace ( Preheating ) – Natural Gas or LPG 4- Grit/Shot Blast Cleaning Machine ( Roto-jet double disc turbines ) 5- Pipe Kick-Out Arms, Pipe Racks and Let-Down Arms 6- Process Conveyors 7- Induction Heating System ( High Voltage Generator and Induction Coil ) 8- Electrostatic Epoxy Powder Spraying Unit – CO2 Fire Extinguishing System 9- Adhesive Extruder and Side Wrapping Head 10- Adhesive Film Pressure Silicon Roller 11- Polyethylene Extruder and Side Wrapping Head 12- Polyethylene Film Pressure Roller 13- Water Cooling Circuit and Cooling Tunnel 14- On-Line Holiday Detector 15- Pipe Kick-Out Arms and Racks 16- Pipe End Cleaning Machines 17- Pipe Exit Racks
TYPICAL LAYOUT AND SYSTEM COMPONENTS
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PRD Pipe Manufacturing Systems
E-COATING PROCESS
VISUAL INSPECTION
PIPE ENDS PROTECTION PREHEATING
ABRASIVE BLAST
VISUAL INPECTION
SURFACE TREATMENT
HEATING
PRIMER LAYER - FUSION BONDED EPOXY
ADHESIVE INTERMEDIATE LAYER – EXTRUDED COPOLYMER FILM – SIDE
TOP LAYER - EXTRUDED POLYETHYLENE FILM – SIDE
COOLING
HOLIDAY DETECTION
PIPE END CLEANING
FINAL INSPECTION
STORAGE
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REPAIR
F-PROCESS PARAMETERS 1- Precleaning of the pipes prior to blast cleaning for : - removal of surface contaminations ( salts, soil, grease, oils, organic matter and contaminants ) - loosening mill scale - removal of moisture Methods : - High Pressure Fresh Water for removal of salts and soil - Hydrocarbon solvent ( xylol or mineral spirits ) for removal of organic contaminations - Preheating of pipe surface by flame burners to 75 degree C for loosening mill scale, removing moisture, burning of organic matter and conditioning pipe surface for blast cleaning. 2- Shot/Grit Abrasive Blast Cleaning : The purpose of cleaning is to obtain clean steel surface with the cleanliness degree of Sa 2 ½ and an anchor pattern with the average profile depth of 25 – 80 microns. Blast cleaning may also remove pipe defects ( slivers, burrs, laminations, scabs, gouges ). If not, grinding can be also used for removal of such defects on pipe surface. EXTERNAL SHOT BLAST MACHINE
3- Heating of the Pipes The pipe surface shall reach the temperature of 200 – 220 degree C prior to powder epoxy application. The pipe surface temperature shall not exceed 270 degree C. Metallurgical or surface defects can occur at over 270 degree C. Bluing or darkening of the pipe surface is an indication for over heating of pipes.
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INDUCTION HEATING
Surface Treatment Chromate pretreatment ( 1% - 5% of concentrated solution )
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Coating Thickness : -
Epoxy powder 80 – 100 microns Adhesive film 350 microns PE film 1.5 – 3 mm 5
PRD Pipe Manufacturing Systems
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Cleaning / Process Line Conveyors The pipes move helically over the conveyors through : -
preheating unit blast cleaning cabinet chromate application heating coil or flame heating furnace epoxy spray booth water cooling tunnel
Adhesive and Polyethylene films are wrapped around the pipe in a helical motion GENERAL VIEW FROM PE. COATING PLANT to form overlap.
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Water Cooling The pipes are cooled by water at least to 70 degree C after extruded adhesive and polyethylene film application.
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Pipe End Preparation All pipes are cleaned for field joint welding. The coatings at pipe ends are removed by rotary brushes for the length ( max. 150 mm ) specified by related specification.
COOLING TUNNEL
9- On-line Quality Control -
The pipes are tested on-line after cooling for holiday at 25 kV. Temperature check of pipe surface prior to epoxy powder spraying is done by infrared temperature measurement device
HOLIDAY DETECTION
10- On-line Spot Check -
Non destructive coating thickness measurement Temperature check of the bare pipe surface after heating unit and coated pipe surface after adhesive and polyethylene film application is done by manual – roller type temperature measurement device. 6
G-PROCESS Initially, pipe ends are covered by protectors to prevent the damage of pipe bevels from blasting and then the pipe is taken to cleaning line conveyors. The pipe is transferred to gas-heated burners in a spiral movement on conveyors in order to remove the surface moisture. Then the pipe is fed to blasting unit. Steel grit and/or shot is used in blasting unit. The surface of pipe is cleaned. After blasting, the pipe surface is visually inspected. The pipe having acceptable surface condition is transferred to process line conveyors by rolling on pipe racks between cleaning line conveyors and process line conveyors. The pipes are transferred end to end in a spiral motion continuously on process conveyors. Initially the pipes are moved through induction heating coils or gas-heated furnace. The pipes are heated to the temperature of 200 degree C. Then, epoxy powder ( primer ) is sprayed to pipe surface by electrostatic guns located inside the booth. The pipe surface temperature is monitored continuously by optical temperature measuring device. The adhesive film is applied by extruder on pipe in an overlapping form. Just after adhesive film, polyethylene film is applied by other extruder to pipe surface in several overlapping forms. PREHATING BEFORE SHOT BLAST BLAST
Adhesive and polyethylene films are pressed by silicon pressure rollers onto pipe surface to obtain uniform coating. The pipe is transferred to water cooling section located just after extruders. The endless polyethylene coating is separated at the pipe ends to have single pipe at the beginning of cooling section. Pipes are cooled to temperature below 70 degree C. The pipes are inspected by on-line holiday detector continuously at the end of cooling section. The pipe is marked by spray gun if a pinhole is detected in the coating.
EPOXY POWDER CABINET AND EXTRUDER
The coated pipes are moved to pipe end cleaning machine by rolling on the racks located at the end of process conveyor just after cooling section and holiday detector. The polyethylene coating on the pipe ends are removed by rotating steel brush.
Polyethylene coated pipes are lifted with belts or rubber-coated forklift for moving to storage area or loading to trucks. PIPE END CLEANING MACHINE
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PRD Pipe Manufacturing Systems
H-TYPES OF WRAPPING 1- Adhesive and PE films to be applied on the bottom of the pipe. Adhesive and PE extruders are located on floor and on the same side of the pipe. 2- Adhesive and PE films to be applied on the top of the pipe Adhesive and PE extruders are located on the same side of the pipe on a platform. The level of platform is adjustable according to the diameter of the pipe to be coated. 3- Adhesive film to be applied on the top of pipe and PE film to be applied on the bottom of the pipe. PE extruder is located on the floor and adhesive extruder is located at a lifting platform on the other side of the pipe. The level of lifting platform is adjustable according to the diameter of pipe to be coated I-CAPACITIES OF THE MACHINES AND EQUIPMENTS* 1- Blast cleaning machine ( roto – jet double disc turbine type ) Grit / Shot rate ( toward the pipe surface ) Machine rate
: 200 -500 Kg / min at a velocity of 80 m / sec. : 35 -75 kW / turbine
2- Gas Fired – Flame Heating Furnace for process line Heat Input: 6 million BTU / hour
SHOT BLAST MACHINE AND FLAME HEATING
FLAME HEATING FURNACE
3- Induction Heating Unit Power Supply M.F. power rating Working frequency M.F. nominal rated voltage
: 500 kVA - 1800 kVA : 400 kW - 1400 kW : 1000 Hz – 4000 Hz INDUCTION HEATING COIL : 1000 V – 1250 V 8
4- Extruders Adhesive extruder output Polyethylene extruder output
: 150 - 250 Kg / h : 1000 - 1500 Kg / h
ADHESIVE EXTRUDER
POLYETHYLENE EXTRUDER
5- Electrostatic epoxy powder unit Powder spray gun Electrical field
: 15 units : 95 kV
EPOXY POWDER AND SYSTEM CONTROL PANEL
EPOXY POWDER CABINET
* Above parameters are defined according to required coating capacity.
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PRD Pipe Manufacturing Systems
J-INSPECTIONS AND TESTS The tests and inspections written below are carried out for assuring the quality of the coating. On-line continuous inspections and tests : 1234-
Surface Inspection Thickness Test Temperature Check Holiday Inspection
Off-line periodical inspections and tests : 123456-
Impact Resistance Test Adhesion ( Peeling ) Resistance Test Hardness ( Indentation ) Test Tensile ( Elongation ) Test Cathodic Disbonding Test Coating Resistivity Test TENSILE TESTER
K-REPAIR There are two main repair methods in case the coating is damaged during the transportation and storage of the coated pipe and also during the pipe line construction. 1- Stick embedding method for small size repair 2- Patch and tape method for large size repair
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SHOT BLAST LINE
COATING PLANT GENERAL VIEW
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PRD Pipe Manufacturing Systems
COATING LINE
COATING PLANT GENERAL VIEW 12
