The capillary tube is a smaller tube with a small inside diameter, mostly it has a diameter of about 0.5 to 2.2mm and it is used in the domestic refrigerant, deep freezers, water coolers, and air conditioners.
The capillary tubing is also an appropriate method for separating a pressure instrument such as a gauge or transmitter from the process tapping/connection. Capillary tubing is used to separate the direct connection between the measuring instrument and the process tapping point.
High precision: seamless stainless steel capillary tubing is used in a wide range of instrumentation measurement applications. Based on the heavy wall, small diameter construction (typically 1/8" or less), this tubing is used in critical applications from nuclear reactors to resistors in aerospace.
Because a high-quality seamless capillary tube is made from a single homogeneous piece of steel with a continuous, uninterrupted grain structure, it is more suitable for applications that require consistent material throughout the tubing. Welds and mechanical fittings permit discontinuities that can encourage crevice corrosion and mechanical failure.
High-quality stainless steel allows for the formation of a passive protective layer at the surface in the presence of oxygen. Poor heat treatment and welding can affect this layer by changing the critical chemical composition in the Heat Affected Area (HAZ) due to the different alloying elements having different melting points.