Many facilities have tested piping systems by installing various types in the same process conditions. While they have comparable performance in a lot of respects, there is often a greater deviation over an extended period of time. Here are the areas where glass-lined pipe surpasses other options when put to the test of time.
Build-Up
Unlike PTFE and other fluoropolymer lining materials that are soft and subject to abrasion and product build-up, glass is one of the hardest natural occurring materials. Glass lining maintains its smooth, impervious surface even in the harshest environments to greatly reduce or in some cases eliminate product build-up.
Structural Integrity
When it comes to the bond between the lining and the base, glass wins hands down. Since glass lining is fabricated using extremely high temperatures, a mechanical and chemical/molecular bond is created. This bond is permanent so the glass lining cannot separate from the base metal, making the design impervious to liner collapse from full vacuum conditions at high temperatures. With most other types of lining only a mechanical bond is created with the base metal. The lining materials can become brittle over time or even shrink which can cause separation from the base metal and make the liner subject to collapsing under vacuum.
Permeation
A big concern that arises in any application that involves corrosive media is permeation, which needs to be carefully managed so as not to allow contamination of the lining or a chemical attack on the steel substrate. Glass lining is non-permeable and has no problem handling chemicals that can permeate fluoropolymer piping. Chances are if you are considering using glass-lined pipe then your process already involves a glass-lined reactor. If the material of construction is satisfactory enough for the large, most significant units in your process, you can be 100% sure that piping of the same fabrication will support your process requirements.
Cost
It’s no surprise that lined pipe is more expensive than unlined pipe, as there is a significant amount of extra work that goes into the manufacturing. Therefore, if your process can adequately function using a more basic piping system, then unlined pipe is the way to go; Glass-lined pipe is intended for processes that have more stringent requirements for corrosion resistance and cleanliness. When compared to the less expensive option of unlined pipe, though, the additional expense of glass lining is often compensated by the reduction in man hours required to clean lines (build-up can become a huge issue in metal pipes) so if you do have a product that accumulates in piping, glass lining is certainly a viable option.
Other Considerations
Since lined pipe is constructed with some type of metal as the base, the arrangement of the piping system must be carefully measured since the material is rigid and offers no malleability. However, there is some level of versatility when it comes to PTFE-lined pipes in that the pipe lengths can be cut down to a desired size and reflanged to fit into the pipeline run. Glass-lined pipe sections do not offer this type of flexibility; since glass-lined equipment must be processed through a furnace their length cannot be altered. Therefore it is important to obtain accurate run dimensions prior to ordering your pipe. Spacers can be used to make up for differences in some instances but if a non-standard length is required then it must be manufactured to order.