Y-strainers are almost always supplied in one of four materials, iron, bronze, carbon steel, or stainless steel. Iron is most widely used because it costs the least. Its disadvantages are poor resistance to thermal shock and poor resistance to mechanical shock. For these reasons, iron is used on non-critical applications involving low pressures and temperatures.
Bronze is the second material of which Y-strainers are made. It has better thermal and mechanical shock qualities than iron, and therefore, is sometimes preferred for low pressure steam service. However, it is limited in temperature to a maximum of about 350 degrees F.
Carbon steel is the third material and is best when strength, temperature or mechanical shock resistance are important. Many engineers specify carbon steel even when iron might be suitable. The extra cost is very small when spread over the years of actual service and a good safety factor is built in. Particularly with steam, the chance of an accident to many people is not worth the risk of using lower priced iron in place of more dependable steel.
The last common material for strainers is stainless steel. This, of course, is used where corrosion is a problem. Many gases such as those from petroleum operations or natural gas are “sour” or acid and when moisture is present, will corrode iron or steel. In these cases, stainless steel is called for.