MANUFACTURING AND INSPECTION PROCEDURE FOR 3 LPE COATING

PURPOSE:

The purpose of this procedure is to provide instructions for carrying out and monitoring the three-layer polyethylene coating process on bare pipe surface.

GLOSSARY:

3LPE --- THREE LAYER POLYETHYLENE

ABRASIVE BLASTINGBARE PIPE

PREHEATING BLOW OUT STATION

CHROMATE APPLICATION

HEATING STATION

EPOXY APPLICATION

BOOTH

QUENCHING ZONE

THICKNESS, VISUAL CHECK AND TEST STATION

BRUSHING MACHINE

HOLIDAY, REAPIR & FINAL

INSPECTIONSTENCILLING AND

READY FOR DESPATCH

WELSPUN GUJARAT STAHL ROHREN LTD

ADHESIVE & POLYETHYLENE / POLYPROPYLENE APPLICATION

BOOTH

PHOSPHORIC ACID WASH & HIGH PRESSURE WATER RINSE

BLASTED SURFACE INSPECTION

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QTP --- QUALITY CONTROL AND TEST PLAN NTC --- NOT TO BE COATED R.H. --- RELATIVE HUMIDITY

REFRENCES:

DIN 30670 SSPC SP-10 SIS 055900 CAN/CSA/Z 245.20-02 ASTM D-1238

RESPONSIBILITY:

The Production Manager or his authorized person is responsible for carrying out the coating process.

COATING SYSTEM REQUIREMENTS:

PROCEDURE QUALIFICATION TEST

As mentioned in the QTP or randomly five pipes are selected for PQT. All the required tests are performed on these pipes before regular production.

SEQUENCE OF OPERATIONS FOR 3LPE COATING

BARE PIPE RECEIVING

Bare pipes shall be received from client either by purchase order or as a free issue material. Pipe shall be unloaded by vacuum crane/MOBILE / EOT WITH rubber padded hooks. Job No. / order No. Wall thickness, diameter and other relevant marking details shall be checked and matched with the received packing list from the pipe manufacturer.Pipe shall be stored in the yard in stacks physically separated by order No./ job No/ diameter/ wall thickness.

BARE PIPE INSPECTION AT INLET

Pipes are unloaded by EOT crane of 15-ton capacity with rubber-padded hooks on to the rack. The rack is installed with a slope to ensure pipes natural movement towards the blast-cleaning conveyor and is equipped with kick out device.Bare pipe shall be visually checked for steel defects, such as bevel damage, dent, Flatness, scratch, lamination etc and for any kind of contamination.

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Each pipe shall be identified by its mill No. Before starting the cleaning operation. QC inspector at inlet station shall make sure that all data of pipes found is in order.

PREHEATING

Heating system is equipped with 6 gas fired oven of 430000 kcal / hr each. It can heat up to 306 ton steel per hour and up to 100°c.Preheating of pipe is to be done, if the pipe surface temperature is less than 3°C above dew point or if relative humidity is more than 90% or as per customer requirement. Pipe Temp, Relative Humidity dew point shall be measured by suitable instruments and by suitable means. ABRASIVE BLASTING

Two shot blasting machines are placed one after another. Each machine consists of four turbines with 75-kw/100 hp motors. Each machine is capable to clean up to SA 2½, SSPC SP-10 standard and roughness between 50-70µm. Each machine is equipped with dust vacuum suction and grit reclaim system, grit sieving & spent particle removal.

After blasting pipes are moved to blowout station where all dusts, shots & grits are blown out from inside pipe surface.

Pipes received at blasting inspection rack are checked for below mentioned parameters as per approved QTP

Cleanliness Dustiness Roughness Salt level Visible steel defects Magnetic Intensity

All the measuring instruments are calibrated as per approved QTP.

Any pipe not complying the QTP requirement will be marked as “NTC” by and sent for rectification.

After inspection of bare pipe coupling shall be attached on one end of pipe for smooth coating. The coupling will be slightly heated to makeup for the heat loss at the time of induction heating due to additional thickness of the coupling.

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PHOSPHORIC ACID TREATMENT APPLICATION (if required)

If the incoming pipe is tested positive for salt contamination, then phosphoric acid treatment is done and thereafter rinsed with high pressure demineralized water. The acid application cabinet is equipped with 4 nozzles of 1.5 M3/Hr. capacity.

CHROMATE TREATMENT APPLICATION (if required)

To enhance the bond strength between the substrate and fusion bonded epoxy layer chromate layer is applied using rubber wiper.

APPLICATION STATION

FUSION BONDED EPOXY APPLICATION

Pipes are heated by 2 consecutive induction coils of 300 Hz capacity. Pipe surface temp is recorded using temperature gauge with roller type probe. The temperature shall lie between 180 - 240 °C or as per epoxy manufacturer recommendation.Application of epoxy primer is carried out using 20 electrostatic guns of capacity 1000kg/hr for 1500 µm thickness. The system is also equipped with fluidized bed with venture pumps, surplus powder suction & recycling plant.

ADHESIVE APPLICATION

The system is 222 mm diameter equipped with lifting platform. It is provided with vacuum feeding unit of capacity 400Kg/Hr. and a hopper neck with heating control unit

POLYETHYLENE PPLICATION

The system is provided with 150mm diameter, 510KW extruder vacuum granule suction with hopper “Y” shaped feeding neck of capacity 1600Kg/Hr. with temperature control system

PE and Adhesive film temperature is measured using digital infrared thermometer.

COOLING ZONE

In the cooling zone coated pipe shall be subsequently quenched & cooled in water for a period which shall sufficiently lower the temp of pipe coating to permit handling & inspection

This zone is 38 M Long, provided with water distribution system, hydraulic power units & motors.

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Chiller capacity 18 m3/hr., 125 trCooling water circulation rate 400m3/hr

ON LINE INSPECTION STATION

Here the thickness of the applied coating is measured by means of magnetic thickness gauge, bond strength of coating is measured using suitable apparatus. If any defect appears on coating such as coating damage due to peel test the pipe is then sent to the repair bed.

END CLEANING

Brushing machines equipped with 2 electric motors of capacity 45 hp. with adjustable brush to create bevel to PE. Brushes to remove coating up to steel and form taper end.Cutback length shall be as per customer requirement in approved QTP.

HOLIDAY TEST AT 25 KV

Each pipe is passed through the holiday ring to check for any discontinuity in coating.

The holiday detector shall be low pulse D.C. full circle electronic detector with audible & precise voltage control

If any damage observed it is marked manually by chalk and repaired as per approved repair procedure.

After holiday colour codification is given as per approved QTP

FINAL INSPECTION

Coated Pipes Are Visually Checked. Coating film shall be uniform in thickness, glossy and free from any irregularities. Bevel ends shall be free of coating materialRepair should be done as per approved repair procedure.Apply white wash (emulsion paint) on 3 LPE coated pipes to protect UV attack if required by the customer.Accepted pipes are assigned with unique TPI no after final inspection.Stencil marking at the end of external surface of the coated pipes is carried out using spray gun.

YARD HANDLING AND STORAGE

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After final Inspection, coated pipes are fitted with bevel protectors and lifted from final skid by EOT/cranes padded with rubber hooks and loaded on trailers for transportation to stockyard.

SAW(SAWL,SAWH): Spiral WeldedSSAW: Spiral Submerged-arc Welded

LSAW (Longitudinal Submerge-arc Welded) UO(UOE)、RB(RBE)、JCO(JCOE)DSAW (Double Submerged arc welded)

ERW (Electric Resistance Welded)HFI (High Frequency Induction)EFW(ELECTRIC FUSION WELDED TUBE)HFW(High-Frequency Welding)

- Have knowledge of Rotating (Pumps, Compressors, Material   Handling, Packaged equipments).- Have knowledge of Pressure vessels (vessels, Scrubber,    ASME Sect. II & VIII, PV Elite, TEMA, WRC 107/297, NACE).- To be familiar with various statutory requirements.- Be familiar with the preparation of specifications.- Prepare data sheets and should be able to prepare various  reports.- To be familiar with the testing and inspection requirements.- To guide drafting team.- To check various vendor design calculations/ vendor drawing  & documents.- To participate in various reviews, if reqd.- Maintain master copy of all discipline deliverables.- Prepare Material Handling study report.

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