To establish a recommended quality assurance program for applicators of blastomeric sheet linings.
This bulletin describes the systems, methods and techniques for assuring the quality required by contractual obligations.
3) Applicable Documents
4) Receiving Inspection – Materials
4.1) Equipment to be lined
1) Part identification – serial #’s
2) Document receiving/inspection All items to be lined are inspected according to the
applicable plant inspection procedures and visually inspected for:
_ Shipping damage
_ Compliance with RMA Protective Linings Bulletins:
#1 Specifications for Welded Steel Tanks, Stacks, Ducts or other Welded
Parts for Protective Lining and/or Coating.
#2 Specification for Pipe and Fittings for Protective Lining and/or Covering.
4.2) Blasting Raw Materials
All blastomeric raw materials are inspected according to the applicable plant
inspection procedures and left in the original unopened containers, unless
physical damage to the container or package is found. Then the package is to
be opened to determine the degree of damage. These materials are visually
inspected and documented:
Proper size – i.e. thickness, width, length
Complete or partial quantity received
Material is within shelf life
Any discrepancies found are to be noted on the receiving report at the time of receiving inspection and reported to the applicable quality control supervisor for disposition. The material will be tagged “on hold” until approved for use or return to manufacturer. When applicable or required, the receiving date will be marked on original containers to permit age and inventory control.
All blastomeric raw materials shall be stored under cover, away from heat and light sources, in a cool, dry storage area in conjunction with the materials manufacturers recommended practices. During extremely hot weather, refrigerated storage may be required and is recommended. During periods of storage the conditions are recorded.
5) Inspection Prior to Blasting
5.1 Surface Contamination
The grit in the blast unit shall be inspected for contamination on a periodic basis and a record of these inspections is maintained. The inspection is accomplished by depositing a representative sample of grit in a beaker of clean water.
If an oil slick is formed on the surface of the water, or other contamination is found, the grit should be replaced or properly cleaned.
5.3) Compress Air Quality
Compressed air that is used for blasting and grit removal shall be kept free of oil and water contamination. Cleanliness of the air shall be determined by discharging air against a clean white blotter. Contamination will be seen as a darkened circle. Test shall be conducted at the start of every shift and results must be recorded.
5.4) Temperature and Humidity
Extreme care must be taken to prevent sweating of the metal surface. The relative humidity should at no time be high enough to produce a dew point during blasting, cementing, and lining and cause moisture to deposit on the cemented surface. To prevent condensation it is important that the substrate be a minimum of 5°F above the dew point or wet bulb temperature. Record temperature and humidity every four hours or as conditions change.
6) Inspection after Blasting and painting
All metal surfaces to be lined should be a clean grey-white metal blasted surface finish in accordance with RMA Protective Linings Technical Bulletin #3. Note: In contrast with grit or sand, the slag blasting agents produce a somewhat darker blasted surface appearance.
6.2 Removal of Blasting Material
All blasting materials should be cleaned from the surface of the metal by brushing, vacuuming, or blowing >with filtered compressor air before applying the metal primer.
7) Priming and Cementing
Primer cement shall then be applied
before any “flash rusting” can occur. If flash rusting does occur, the surface shall be reblasted as previously specified. Articles removed from blast area shall be protected in a manner as not to contaminate the blasted surface. In the event of the article being completely lined, the supporting surface shall be protected from contamination. Record the elapsed time between blasting and the application of primer.
7.1) Technique of cement applications shall be in accordance with manufacturer’s instructions, as to ensure a complete and uniform wetting of the surface. A separate set of brushes and rollers shall be maintained for each type of cement.
7.2) Drying time of cement should be in accordance with manufacturer’s instructions. Cemented parts should be kept free from all contamination during the drying and layover period. Cemented surfaces should not be exposed to sunlight and/or weather.
Temperatures should be between 60 to 90 degrees F for best results.
8) Application of Blasting Sheet Lining
8.1 After cementing, the metal shall be inspected to determine the best method of lining. Because equipment to be lined vary as to size, shape and the location of projections, irregularities and flanges, there is no set method ٥ of ٣Page of lining.
8.2 Prior to application, the uncured Blasting, Coating lining should be examined to verify that it is clean and free of any functional defects as outlined in RMA Bulletin #6 – Standard for Surface Appearance of Blasting, Coating Sheet Lining Materials.
8.3 The joint selected is usually determined by the Blasting, Coating material used. There are primarily two types, although there are variations of each, the 2” lap joint and the butt joint with cap strip.
8.4 Cut sheet to desired size and shape.
The type of material used may dictate the skive used. Warm on hot table.
Homogeneous or single may utilize an open skive or closed, while multiple layers of dissimilar
stocks require a closed skive. When cutting material, allowances should be made for a
minimum 2” lap unless restricted by dimensional tolerance, specifications or lining manufacturers’ recommended joint construction.
8.5 The lining must be rolled tightly against the material to remove any trapped air to assure complete contact between the elastomeric and metal.
Joints should be examined to determine that the seams are straight and all edges are stitched down tightly. Rubber fillets should be used in corners to prevent stretching.
8.6 Before pre-cure spark testing, the lining should be visually examined to
assure that the lining is clean, free of trapped air, and all seams are straight
and tightly stitched.
8.7 Air blisters that are found shall be punctured, vented and stitched down.
Overlay the area with the same material of the same gauge.
9) Procure Inspection
9.1 Check customer drawings, if available, to assure lining has been applied to the proper areas and with
correct thickness, and type.
9.2 Check any dimensional tolerances
and drawings, if available, against finished lining dimensions.
9.3 Determine that all components
associated with the job are together and complete.
9.4 Closely observe the general acceptance of lining surfaces for imperfections.
A. Check splices for looseness and uniformity.
B. Check for trapped air or blisters, pinholes, and other imperfections requiring rework.
C. Mark unacceptable areas with chalk.
9.5 Spark Testing – Before Cure
A. Calibrate spark tester
B. Spark test to voltage indicated by the lining manufacturer.
C. Mark any pinhole leaks found in spark testing with chalk for rework before cure.
10.1 Steam Curing
Make certain that an appropriate vacuum break device is installed to prevent a vacuum collapse of the vessel when any steam method of cure is used.
A. If pressure or atmospherically steam cured, check chart recorder or thermometers against the recommended time and temperature and compare to the manufacturer’s specification. Monitor outside temperature every 10-12 ft. and every 30° around every hour.
B. Check vessel to determine if any condensate can collect without draining, make provision to drain same.
C. When curing the external skin temperature is monitored, record the temperatures maintained at the top, middle and bottom of the vessel on an hourly basis and compare to the recommended time and temperature (minimum 150°F). Also field vessels must be insulated from the elements to ensure a thorough cure.
D. When pressure cured and cooled under air pressure and water spray, record the temperature, time and …
E. When test plate samples are to be cured with the vessel, make sure they are placed at several levels in the vessel. Record their position.
10.2 Chemical Curing
A. Record type and number of coats of curing agent used.
B. Check durometer daily until proper hardness is attained before vessel is released for use.
10.3 Hot Water Curing
A. This special cure should be done only under the direction of Blair Rubber Company’s Technical Department.
11) Post Cure Inspection
11.1 Closely observe the general appearance of all rubber surfaces for imperfections.
A. Check splices for looseness and uniformity.
B. Check for trapped air or blisters, pinholes and other imperfections requiring rework.
C. Mark areas needing corrections with chalk.
D. Record post cure repairs made on drawings, if available.
11.2 Check durometer of cured lining at various places from top to bottom of the tank after cool down and 24 hours. One reading per 100 square feet should be taken and recorded. Compare to the recommended durometer in manufacturer’s specifications. See RMA Bulletin #18 (in preparation).
11.3 Spark Testing – After Cure
A. Calibrate spark tester per RMA Bulletin #13.
B. Spark test to voltage indicated by the rubber manufacturer.
C. Mark any pinhole leaks found in spark testing with chalk for rework after cure.
11.4 Do not perform destructive adhesion tests on vessel lining. If test sample plates have to be made, the adhesion test will be based on ASTM D413. Results are to be recorded.
11.5 Post cure repairs are to be located on vessel drawings, if available.
These repairs are to be inspected and spark tested the same as the original lining.
12) Repairs to Blasting and coating
12.1 Regardless of the precautions taken prior to cure, repairs may be necessary.
12.2 Remove all loose or defective elastomeric lining.
12.3 There are many variables in selecting the material to repair, such as time available to return equipment to use; the availability of a heat source. The manufacturer should be consulted when selecting the method and type of material to repair.
12.4 There are four methods of cure for repairs:
A. Autoclave Cure – After repair, the entire piece of equipment shall be recured in an autoclave.
B. Internal Pressure Cure – The vessel itself shall be pressurized.
C. Exhaust Steam Cure – The area itself is isolated, or the entire vessel is exposed to atmospheric steam.
D. Chemical Cure – The existing lining shall be repaired with a stock which does not require an additional heat source. The repair material requires an application of an external curing agent to activate it.
Reference: RMA Bulletin #16 – Chemical Cure-Elastomeric Sheet Linings.
13.1 All gasket surfaces to be ground reasonably flat.
13.2 Bolt holes reamed to size of holes in metal.
13.3 All edges should be ground flush with contour metal.
14) Post Finishing – Pre-Shipment
Prior to release for shipment, Blasting and Painting lined equipment shall be inspected for, but not limited to (the purchase order or customer specifications shall govern this section):
1. All documentation completed.
2. All openings properly protected.
3. All labeling required properly applied.
4. Customer inspection, if required, has been completed.
5. Tank exterior to be stenciled in a conspicuous location in letters at least 2” high “Rubber Lined – Do Not Weld, Cut or Burn.”
6. Complete “Quality Assurance Certificate” (Paragraph 15.0 Exhibit A).