- FABRICATION
1.1 Placing of the order for steel items as per the standard and size mentioned in the order.
1.2 On receipt of the materials, inspect the size, standard, and visual inspection for surface finish.
1.3 Cut to the size as per the cutting diagram.
1.4 Preparation of the edges suitable for welding standards.
1.5 Bending of the plate as per the drawing, tag welding, checking the dimension and ovality.
1.6 Root run welding , back chipping and DP test .
1.7 Complete assembly, tag welding and checking of all the dimension as per the drawing.
1.8 Complete root run welding, back chipping and DP test
1.9 Completion of full welding, again checking of dimensions for distortions.
1.10 Complete rubberlining areas welding should be ground smooth suitable for rubberlining as per IS Code 4682 –Part-I
1.11 Visual inspection of complete rubberlining area for proper welding and smooth grinding.
1.12 Conduct DP test on complete welding areas which is in contact with rubberlining .
1.13 All the flange surface checked for flatness/distortions.
1.14 Carry out Hydraulic Pressure test/Vacuum test as per the working condition of the equipment.
- SURFACE PREPARATION
2.1 The rubberlining areas to be cleaned for scale and rust
removal,and also the surface roughening will be affected by
shot blasting (granulated hard grit will be used as blasting
agent)which will increase the bonding strength.
2.2 After the blasting, the fine dust and dirt will be cleaned with compressed air.
2.3 Checking of blasted areas for proper cleaning and whether it is as per the drawing for rubberlining.
2.4 Complete rubberlining areas will be checked up for any projection/undercuts/blow holes and will be rectified suitable for rubberlining. Further the repaired areas will be again cleaned by blasting.
The equipment will be moved to the rubberlining department.
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APPLICATION OF SOLUTION
3.1 The rubberlining department is totally enclosed for dust proof and having controlled temperature and humidity, suitable for application of solution and rubberlining.
The Excess air humidity will lead condensation of water particles on the lining surface which lead to bonding failures of rubber with metal. The excess temperature will lead to loose bonding of rubber.
3.2 The blasted areas will be cleaned with brush, and followed by thinner, to remove the fine dust and oil particles to ensure perfect cleaning and the complete cleaned areas will be checked thoroughly before application of solution.
3.3 Checking up the viscosity of solution suitable for first, second and third coat before application.
3.4 Application of the first coat of the solution and followed by second and third coat with proper intervals minimum of 12 hours or maximum of 24 hours according to the whether condition.
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COMPOUNDING AND MANUFACTURING OF RUBBER SHEET
4.1 We have different coaded rubber compound formulas which will have individual corrosion resistance properties.
The Suitable rubber compound will be selected according to the working condition of the rubberlining equipment.
4.2 The Rubber and chemicals will be weighed with the highly precision weighing equipments, (electronic Weighing scale)as per the compounding formula .
4.3 The Preliminary mixing of rubber and chemicals (excluding the accelerators) will be done in the internal mixture (Kneader Machine)which is totally closed and the rubber compound will be stored for minimum of 12 hours for self settlement.
4.4 The primer mixture will be mixed with accelerator in the opening mixing mill and again stored for minimum of 12 hours for settlement.
4.5 The fully mixed rubber compound will be warmed up in the open mixing mill and immediately feeded through the three roll calendar machine for sheeting.
4.6 The required thickness of rubber sheet will be taken out from the calendar machine and through the doubling machine(size of 1 mtr width x 10 mtr length). The rubber sheets will be rolled with liner and stored in the air conditioned room, where the temperature is controlled between 18 to 20 degree centigrade.
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RUBBERLINING
5.1 Spreading of un-vulcanised calendared and doubled to the
required thickness of rubbersheet on the table.
5.2 Checking of surface finishing airlock and thickness of
rubber sheet.
5.3 Cutting of rubber sheet (tapered edges ) to the required
shape and size
5.4 Cleaning of rubber sheets cutting edge, inside surface and
the metal portion to be rubberlined with thinner
5.5 The above rubber sheet folded with liner cloth and spreaded
over the rubber lining area.
5.6 The rubbersheets to be fixed properly and liner cloth will be
removed.
5.7 The rubbersheet will be rolled and ressed from the center
with metal and ensured proper removal of air and create
perfect bonding with the metal.
5.8 Followed by the same procedures the complete required areas
of the equipment will be rubberlined with proper overlapping
at the joints.
5.9 Checking up of airlocks and spark testing for pinholes for the complete rubberlined areas and if any defects noted the same will be rectified properly as per code.
5.10 Allow the equipment for 24 hours for settlement and again inspect for air/ gas locks and pin holes before sending it for vulcanizing.
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VULCANSING
6.1 Vulcanising of the rubberlined vessels will be carried out in the vulcaniser under pressure with saturated steam to the temperature between 135 to 140 degree centigrade generally will be used.
6.2 The vulcanizing process will be carried out by proper cycle consisting of temperature verses time and pressure. There will be different kinds of vulcanizing cycles for different types of rubber compound.
6.3 After completion of the vulcanizing cycles, the vulcaniser will be brought down to the atmospheric temperature under pressure, after cooling down the vulcaniser will be opened.
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FINISHING, TESTING, PACKING AND DESPATCH
7.1 The vulcanized vessel will be tested for hardness, airlock, loose bonding and high frequency spark testing for the entire rubberlining area.
7.2 The standard high frequency spark test voltage will be 5KVA/MM of rubber thickness. For carbon/ graphite loaded rubber compound the spark test voltage will be 1.5 to 2 KVA/MM of rubber thickness.
7.3 If any defect noted, that will be rectified and vulcanized again as per code and the same will be tested again to ensure perfect quality.
7.4 All the flange surface will be machined for flatness and the edges for rubberlining will be sandered to avoid any projection which will damage the rubberlining.
7.5 After completion of the inspection and finishing the vessel will be hydraulic/vacuum tested as per the P.O.
7.6 Un lined surface of the vessels will be cleaned by the sand blasting and followed by painting.
7.7 Finally the vessel will be visually inspected and spark tested before packing.
7.8 All the outside exposed surface of the rubberlined areas will be covered with soft, rubber/polythene gaskets fitted with steel/ wooden dummies. Further the entire vessel will be packed suitably for transport.
7.9 The properly packed vessels will be loaded with due care into the container and all the sides will be packed with wooden blanks to avoid any shake during transportation.
Outside of the vessel will be marked for (“Handle with Care”) avoid shock or impact stroke and stored in enclosed place to avoid exposed to sunlight or stored with filling of water till taken for commissioning.
