INTERNAL PAINTING OF SILENCERS

By

ANANDKUMAR

SILENCER

"Device which is used to absorb and damp out high pressure gases coming from a exhaust valve of an engine, to a smooth, quiet flow to the atmosphere”.

FUNCTIONS

To remove exhaust gases.

To reduces the noise.

To maintain the engine performance.

PARTS OF A SILENCER

A silencer is a combination of tuning chambers, baffle partitions and perforated solid tubes designed to create reflected waves that interfere with each other or cancel each other out and thus dissipate noise

CAUSES OF SILENCER FAILURE When the engine stops the silencer cools to normal ambient

temperature there is condensation of the residual fumes and this initiates the corrosion on the internal surface of the silencer.

The (H2O) and oxides of sulphur from the flue gasses react forming low concentrated (H2SO4) which is highly corrosive and attacks the welded areas first.

This weakens the welding strength and affect the steel material causing the pit marks, which leads to formation of holes .

NEED OF INTERNAL PAINTING FOR THE SILENCERS

When the vehicle is not running the acid droplets formed by the chemical reaction of the exhaust gases, starts accumulating on the inner side of the silencer. So the metal surface of the silencer starts rusting in the absence of any protective layer. This causes pits and holes and ultimately the baffle breaks away indicating complete silencer failure.

Noise muffling capacity of the silencer is reduced by corrosion because it causes prominent holes and pits in the welded areas which causes the leakage of sound wave without destructive interference. This causes unpleasant noise and failure of silencer.

The perforations of pipes inside get chocked and prevent smooth passage of gases which will increase back pressure on the engine reducing its efficiency.

REQUIREMENTS OF THE HEAT RESISTANT PAINT TO BE UTILIZED FOR PAINTING:

Good etching properties. (So that paint adheres to surface quickly and firmly.)

Resistant to acid attacks.

Good heat resistance.

Uniform film coating.

Better penetration of gaps .

PRETREATMENT OF INTERNAL SURFACE BEFORE APPLYING PAINT

Degreasing and Cleaning

Removal of oil and other contaminating foreign matter by dipping the component in a emlusion.

Acid Cleaning

Removal of rust and greases

Washing after acid cleaning

Removing of sludge and acid containing iron

salts

Phosphate Coating

It removes all the cleaning agents and

improves the corrosion resistance

DIFFERENT METHODS OF PAINT APPLICATION

SPRAY PAINTING

DIPPING

FLOW COATING

DESIGN MODIFICATION IN SILENCERS TO ACHIEVE INTERNAL PAINT COATING

1. In a silencer, after assembly, only tail pipe is available for paint filling and there is no air vent if CAT is masked . To achieve this, a modification is done in silencer in the form of a drilled hole on the cover plate near inlet pipe. It serves the purpose as an air vent . This hole can also be used for sending in compressed air for fast draining of paint.

2 While painting the paint accumulates over the baffles causing non uniformity in paint coating. This problem is solved by making two small diametrically opposite openings near the edge of the baffles as shown in figure.

3. To ensure proper attachment of paint filling nozzle to the tail pipe, a cone shaped structure may welded to it as shown.

PARTS OF SPM

1. Upper paint tank

2. Collection tank

3. Pump

4. Agitator

5. Over flow Pipe

6. Distribution Pipe

7. Painting Nozzle

8. Silencer holding fixture

9. Drain off channel

DRYING OF PAINT

Baking

Drying of paint about 80c for 10-15 mins is known as baking

Hot air ovens

The silencers after internal painting are put into the oven and heated by using hot air at 180- 250 C for about 10-15 minutes.

ADVANTAGES

Noise muffling capacity can be maintained.

Life of the silencers increases.

Efficiency of engine can be maintained.

CONCLUSION

By making internal painting to the silencers We can increase the life of the silencers by avoiding corrosion and also we can reduce the noise .

REFERENCES

Jain, K.K., Asthana, R.B., 'Automobile Engineering', Tata-McGrawhill, New Delhi (2001).

Shreir, L.L., 'Corrosion', Newnes, London (1963).

Silman, H., Iseerlis, G., Averill, A.F., 'Protective and Decorative Coatings for Metals', Finishing Publications Ltd.

Parker, Dean H., 'Principles of Surface Coating Technology', Interscience Publishers, New York (1965).

Fontana, Mars G., Greene, Norbert D., 'Corrosion Engineering', McGraw-Hill, New York (1967).

Huminik, John Jr., 'High Temperature Inorganic Coatings', Reinhold Publishing Corporation.

Thank you