procedure for application of wrapping and coating
What is the procedure for application of wrapping and coating?
Procedure for application of coating and wrapping: -
A. Prior to application of wrapping & coating, the surface of pipe should be made free from all loose mill scale, dirt, rust, grease, moisture and other foreign material. This is achieved by blast cleaning to grade
Sa 2 ½ .
B. The pipe exterior surface or blast surface shall be coated with primer within four hours of shot blasting. The primer shall not be applied when the pipe surface temperature is below 7C and above 70C. When moisture is present on the surface, the same is heated for sufficient time to dry the surface.
C. The pipe after priming shall be coated with two-flood coat of hot enamel incorporating the simultaneous application of inner & outer wrapping.
content of primer applied on the pipe surface before coating
What is the content of primer applied on the pipe surface before coating?
The primer consists of processed coal – tar pitch and refined coal – tar oil.
enamel applied on the pipe surface for coating
What is the enamel applied on the pipe surface for coating?
The enamel is plasticized coal tar pitch suitable for hot application and filled with inert mineral filler which have minimum tendency to settle down in fluid state.
material is used as inner and outer wrapping
Which material is used as inner and outer wrapping?
Fiber glass tissue consisting of a uniformly porous mat of chemically resistant boro – silicate glass containing not less then 5% B2O3 .
minimum thickness of enamel on any point on pipe
What should be the minimum thickness of enamel on any point on pipe?
The enamel shall have minimum thickness of 2.4 mm when measured on top of the weld with an overall thickness of 4 mm.
overlap between inner & outer wrap, minimum staggering of inner & outer wrap and cold type of wrapping
How much should be the depth of pulling of inner fiber – glass tissue into the hot enamel?
The inner wrap of fiber – glass tissue pulled in such a manner that the same is imbedded half way into the enamel without touching the steel surface.
What should be the overlap between inner & outer wrap?
The inner and outer wraps shall be overlapped by 25 mm.
What should be the minimum staggering of inner & outer wraps?
The overlaps of the inner and outer wraps shall be staggered from each other by minimum distance of 100 mm.
What is cold type of wrapping?
PVC backed bituminous compound tape used for field wrapping is called cold wrapping.
What is the minimum overlap of field wrapping (cold Tape) on shop wrapping?
Wrapping shall start and finish to give a minimum 75 mm overlap onto the adjoining shop coating.
material applied on the flanges or valves to obtain smooth surface, different types of Anodes used in cathodic protection
What is the material applied on the flanges or valves to obtain smooth surface for
application of cold tape?
Moulding compound shall be hand applied to obtain the smooth surface for application of cold tape on flanges / valves.
What is the device used to locate the defects on surface of coating & wrapping?
Holiday detector.
How much crest voltage of holiday detector shall be set?
The crest voltage of holiday detector shall be set as high as practical.
What is the test to ensure the proper thickness, adhesion and the position of inner wrap?
A square of 25mm X 25mm shall be cut from wrapping for determination of thickness, adhesion and position of the inner wrap. This shall be carried out at the rate of one pipe per 50 coated.
What are different types of Anodes used in cathodic protection?
Different types of anodes are magnesium, zinc, high silicon iron, aluminum etc.
insulating gasket kits, application of insulation for personnel protection, securement of insulation on pipe
What are insulating gasket kits?
Insulation gasket kits are designed to restrict the effects of corrosion often found in flanged pipe systems. The most common example is fire water line running inside the ground and turned upward on above ground with flanged connection.
It consists of following kits: -
A. Gasket : - Neoprene faced Phenolic / Glass Reinforced Epoxy (G10).
B. Insulation sleeve : - Reinforced Phenolic / Nylon / Polyethylene / (G10).
C. Insulation washer : - Reinforced Phenolic / Nylon / Polyethylene / (G10).
D. Plated washer : - Electro plated steel washer.
What is the temperature limit for application of insulation for personnel protection?
Insulation for personnel protection shall be required when the line operating temperature exceeds 60C.
What short of paint is applied on the inside surface of aluminium metal jackets for pipe
insulation?
All pipe insulation shall be provided with an aluminum metal jacket with site applied moisture barrier of bituminous paints.
Which material is used for securement of insulation on pipe?
For securement of insulation following material are applied:
A. Stainless steel wire (SS –304) of 1 mm thickness with 225 mm intervals.
B. Aluminium bands of 0.6 X 20 mm with 225 mm intervals.
What shall be layers of insulation for different thickness?
The insulation shall be single layer up to 75mm thickness and double layer at 90mm thickness and greater.
What care shall be taken before applying insulation?
The surface to be insulated shall be free from oil, grease and all other foreign matter and shall be free from moisture prior to the application of any insulation.