Which Type of Metal is Best For a Valve Plate?
Compressors have so much movement, which causes friction. This friction causes heat to generate and build up, so choosing the right material to make your valve plate is of the utmost importance if you want it to last. Every unique application requires different properties, so for your application you may need one that others may not. This article discussed the different types of metals that valve plates can be made of and the benefits that each material provides.
Stainless steel is by far the most universal choice when thinking about making a compressor valve plate. Stainless steel is rigid, meaning it doesn’t want to flex because of its nature. This keeps warping to a minimum, as well as its heat dissipation properties. Stainless steel takes a long time to heat up, and once heated it can still hold its strength, unlike some other materials. Also, again due to the nature of this alloy, it can hold its structural integrity for longer periods of time. Stainless steel will bend moderately, so it has some give to it if it needed to flex. Stainless steel is corrosion resistant, so unlike carbon steel, you do not have to maintain it by applying oil to prevent rusting. This alloy cosmetically being more appealing is also worth noting.
Carbon steel is a cheaper alternative to stainless steel. Even though the price is better, this does not necessarily mean it is a better deal. Carbon steel is more prone to corrosion than stainless steel and needs to be oiled regularly to prevent rust. However, carbon steel is still a viable choice as far as structural strength, even though it does not match that of stainless steel, it is still rigid enough for commercial purposes. Carbon steel is more malleable than its counter-part, so it will flex easier than stainless steel.
Cast iron is well-known for its structural strength and weight. Unlike wrought iron, or normal iron, it is moderately corrosion resistant. This metal is ideal to use where no bending will be necessary. The characteristics of iron make it perfect for friction because it takes a long time for iron to wear. However, this is a very brittle material. If it were forced to bend in any way, it would crack or break.
Spheroidal Graphite Iron
Spheroidal graphite cast iron, also known as SG iron, shares some of the properties of regular cast iron. It will not flex at all, due to its nature it will cause cracks or breaks. However, this type of cast iron is extremely more durable than that of regular cast iron. The tensile strength was increased, so wearing down your valve plate take much longer than the same plate made of cast iron, as long as it is used under normal operating conditions.
Stainless Spring Steel
There are multiple types of stainless spring steel, however they share similar characteristics. A valve plate cover made from this material has properties which allow it to dissipate heat like normal stainless steel, as well as wear slowly. The properties of this metal make it much easier to flex than standard stainless steel, however it will not retain the shape after it has bent. The metal is heat treated to go back to its beginning shape after it flexes. With all this in mind, it is typically not used as most stainless alloys can handle the job just fine with a much lower cost.
The Importance of Which Metal You Choose a Valve Plate
Each of these different materials serves a purpose. Each of them are better at a specific application than the others. The most important thing that you can do before you order your valve plate is to make sure that you are getting the right one for your application. For instance, if you know that there is flexing where the plate is located, then you would need to choose a metal that will return back to its original shape, such as stainless spring steel. Check the ductility of the metal you are thinking about choosing for your valve plate, and make sure it will withstand the function of what it is you need it to do. Each metal behaves differently, always keep that in mind.
Aspects to Think About Prior to Choosing
- Run-time: The amount of time that the compressor will be running makes a huge impact on which metal would be the right choice. The longer the compressor runs, the more heat that will generate. The Wear and Tear Theory shows that all things break down, fast through normal use and at an exponential rate when used more than it was designed for.
- Environment: Corrosion is the natural enemy of metal. It occurs through oxidation, most from the presence of both oxygen and water. If the surroundings condone corrosion, such as moist environments or outdoors, then you will need a metal that is corrosion resistant.
- Vibrations: If there is more vibration than what would be considered normal running conditions, then you should take this in to account as well. Different metals handle this differently, many times requiring flexibility of the plate to make sure that nothing gets damaged. Typically, a damper plate will handle the excess vibrations within the compressor.
- Heat: If your compressor just generates more heat than what would be considered normal running conditions, you need to choose a metal that will handle the extra temperature. If you choose a metal that will not handle the heat properly, it can cause the metal to lose its structural integrity and become either weak or malleable.
- Pressure: If the compressor you are putting the valve plate is large, then you will need to make sure the metal will withstand any pressure that the compressor might generate.
Different metals can have similar characteristics, however it is the characteristics that make them unique that makes choosing which metal to use for your valve plate so important. If you do not choose the right material for the job, you may end up prematurely damaging your plate, or worse. However, if you take the time to choose the correct metal for your application, then you will maximize the life span of the valve plate that you purchase.
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