Air and Gas compressors are typically used in every sector such as Oil & Gas, Steel, Chemical, Engineering industries etc. Based on its intended use, these compressors handle different corrosive gases such as chlorine, hydrogen chloride, hydrogen sulphide etc. The piston rods are subjected to wear and corrosion due to continuous operation under these harsh conditions which result in premature failure of packaging seal areas and untimely breakdowns. In specific industries, these compressors are the heart of overall production and an unexpected downtime may cause huge financial loss. HVOF sprayed carbide and cermet coated piston rods, ground and super-finished to achieve low co-efficient of friction, have proven to exhibit excellent wear and corrosion resistant properties thereby increasing operational life.
A crosshead is a block or bar between the piston and the connecting rod of an engine that prevents the piston from moving from side to side and damaging the piston and cylinder. The crosshead guides the piston rod, protecting it from the sideways forces of the connecting rod. During abnormal operation the cross head comes in contact with sides of the cylinder and an absence of coating will damage the cross head as well as the cylinder.
Babbitt is a soft metal deposited on cross head and cross head shoes through Twin Wire Arc spray and Wire Flame spray coating process. These coatings act as a sacrificial layer meant to provide protection to piston rod and its sub-assemblies during abnormal operation or vibration. The base metal is prepared by machining threads on the coating surface to facilitate better bonding. After coating the surface is machined to achieve desired size and surface finish. Required NDT’s are performed to ensure that the coating does not have any defects.
|Coating Properties||PIC WC02|
|Micro Hardness||20 – 30 HV0.3|
|Porosity||6 - 10%|
|Bond Strength||Up to 3000 Psi|
|Finish Coating Thickness||2 to 2.5mm|
Compressors handling corrosive gases such as chlorine, hydrogen chloride, hydrogen sulphide etc. are subjected to extreme operating conditions. The mating surfaces in such reciprocating compressors, especially piston rods suffer wear in packaging seal areas. Dry-running materials with abrasive fillers such as ceramics, glass or carbon fiber can cause severe wear related damage on counter body surfaces made of cast iron. If abrasive gas contaminations such as aluminum oxide are involved additionally, even nitrided parts cannot provide adequate wear resistance. Even hard chrome plating’s offer no protection in such cases.
We have been actively involved in providing specialized coating solutions for compressor piston rods to combat wear, abrasion and corrosion. The coatings are applied with HP-HVOF process that produces a dense and homogeneous coating with very strong mechanical adhesion to the rod surface. The coatings are ground and super-finished, further enhancing the sliding properties and reducing wear of mating seal parts. Our PIC DC range of coating solutions prove to be the best replacement for hard chrome plated piston rods and improves the operational life by 5 - 8x.
We refurbish piston rods which are previously nitrided, hard chrome plated or tungsten carbide coated. We have in-house setup for complete manufacturing of coated piston rods ranging from 12 to 120 inches in length.
|Coating Properties||PIC DC08||PIC DC09||PIC DC12|
|Micro Hardness (HV0.3)||1100 - 1400||1100 - 1400||800 - 1100|
|Corrosion Resistance||Good||Very Good||Excellent|
|Max Temperature||< 450°C||< 450°C||< 850°C|
|Bond Strength||>10000 Psi|
|Finish Coating Thickness||150 to 200 µm|
|Surface Finish||< 0.4 Ra µm|