Pre-treatment and Cementing – After sandblasting the metal surface a suitable primer shall be applied. After primer is dry, apply a coat of cold-set adhesive (i.e. rubber cement or as recommended by the rubber lining supplier) to the surface to be lined and to the rubber sheet. This is called cementing.
Cementing involves the use of an adhesive system that is compatible with the lining material specified. The lining supplier will provide the proper data for cement selection and application procedures. All cementing must be done following proper time frames for recoating and drying times. Cements must be mixed thoroughly to suspend all solids before application, and proper storage is required to maintain cement shelf life.
Application of Rubber Lining
Lining process
Allow the adhesive (cement) to dry before applying the rubber sheet to the vessel wall. The lining process is as follows:
Application of the uncured sheet stock should begin immediately after the application of the adhesive (cement) system.
The rubber sheet stock is to be applied to the vessel by hand. The lining stock is rolled out and cut to fit the area it is designed to protect. Cutting the rubber panels the correct width and length will prevent stretching that can cause tension during application and curing.
Each sheet is to be carefully laid and rolled into place to ensure all air is expelled between the sheet and metal surface. Thus, the rubber shall be rolled onto the substrate to remove all air between the lining and the substrate. Any air trapped during application must be removed before curing takes place.
Edges of sheet are to skived and carefully rolled. Adjoining sheets are to be overlapped 50 mm (2″) minimum. Seams are to rolled and stitched to ensure intimate contact.
Lining is to be carried through all nozzles. The nozzle lining is to overlap the lining on the vessel wall 25 mm (1″) minimum.
Upon completion of the lining operation, a pre-cure inspection shall be performed to check for entrapped air, loose seams, and visual defects. Any areas found are repaired with original lining stock before final cure.
A spark test shall also be conducted using a high voltage tester (10,000-15,000 volts) to detect any pinholes in the lining. These defects are repaired and tested before beginning the final cure as described above.
Any leaks detected shall be repaired by patching with unvulcanized material of the same compound as the original lining.
All trapped air shall be removed by the use of a hypodermic needle. Once the area is stitched to the substrate the needle hole is covered by a 2” x 2” patch using the original lining material.
Stitching is performed by hand using a 1/8 inch wheel. The stitcher has the appearance of a pizza cutter. Rolling the stitcher along the seam ensures that all edges are adhered tightly to the adjoining piece. Seams are stitched down to ensure a good closed joint.