The Advantages of Using Monel Hose vs. Teflon for Chlorine Transfer
The Chlorine Institute’s Pamphlet 6 “Piping Systems for dry chlorine” provides useful information and gives practical suggestions for the selection of material suited for chlorine piping systems. Materials of construction for chlorine transfer hoses are discussed in Appendix A of the Pamphlet. It is permitted for chlorine transfer hoses to have both metallic and non-metallic inner cores. In case of metallic hose the inner core shall be Monel 400 (UNS N04400) or Hastelloy C-276 (UNS N10276). For non-metallic hoses the inner core shall be virgin, unfilled PTFE with or without fiberglass reinforcement. So, what are the advantages and disadvantages of one material over the other?
The issue of permeability is probably the most commonly cited disadvantage for non-metallic hoses. Though certain technological advances have been made to reduce permeability in PTFE, the issue is still addressed directly in Section 7.5 of Appendix A, which states:
“Permeability: The inner core of non-metallic hoses is subject to some degree of permeability of chlorine. The braid and chafe guard shall be designed to allow chlorine which permeates the inner core to escape to atmosphere. Uses of non-metallic hose shall be limited to applications where adequate ventilation has been provided.”
Non-metallic hoses would appear to have other “limiting” characteristics as well. Although chlorine transfer hoses are only required to be designed for temperatures between -40F and 122F (which PTFE hoses can certainly handle), monel hoses can operate from -300F to 800F. Finally, Positive Material Identification (PMI) can be used to confirm that metallic hoses are constructed from specific alloys. There is no known PMI for non-metallic materials.
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