- Selecting the type of material for manifold
- Manifold’s Blackening
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Choosing between ductile steel and aluminum can mean the difference between a failed product or machine and a reliable, productive machine. Consider the following factors:
When system pressure will be consistently above 3500 psi, ductile steel is required. Also, when normal operating pressures are at or near or at 3500 psi, and when pressure “spikes” might exceed 3500 psi, ductile steel should be considered.
Corrosive environments can also affect the material requirements of the manifold or body. Typically aluminum is anodized and ductile steel is plated; the plating provides a level of protection against corrosion. Consideration must be given to which is best for the environment.
Duty cycle of the system or function can also affect the manifold or body material requirement. High pulse applications, machine vibration and continuous severe duty cycles are all factors for consideration for using ductile or steel over aluminum.
Generally, aluminum is less costly due to lower material cost and ease of machining.
All of these considerations should be evaluated in your decision to use aluminum or ductile steel. The final choice will directly impact system reliability and machine uptime.
Usually, manifolds constructed of ductile iron material are blackened prior to shipment. After the manifold block is cleaned with a high-pressure detergent solution, the manifold is immersed into two room-temperature tanks that contain a blackening agent. The first tank conditions the part to accept the blackening and removes any surface rust. The second tank blackens the part by adding a thin surface layer approximately 5 millionths of an inch.
Once blackened, the manifold is then immersed into a water-displacing rust preventative solution, which leaves a thin dry film on the manifold. The rust preventative coating is designed to last up to 25 days when exposed to the ASTM-D-1748 humidity test and 50 hours of the ASTM-B-117 salt spray test. Some of the chemicals used to blacken the manifold will temporarily inhibit the oxidation process, however a permanent coating such as paint is recommended for long-term rust protection.