High pressure hose failure (polyester tube)

Gerardcreep · Aug 22, 2003

I need some guidance into a fialure that was experienced in an H2S environment. A high pressure hose, consisting of a internal polyester tube with a double braided high strength steel braided reinforcement covered with neoprene, ruptured. Inside the entire length of the hose showed brittle cracks in an axial direction, and offcoarse the wires underneath this was embrittled by the H2S. Does H2S embrittle polyester? and what can be done to prevent this from happening in the future? Thank you

1399 · Sep 1, 2003

What you have probably is related to polyester hidrolysis. This may cause hardening and material embritlement
Polyesters are not hidrolytically stable and suffer degradation via hidrolisis which is promoted by acids(H2S) This is common in polymers such as: Polyesters, Nylons, Acetals, Polyurethanes, Polycarbonates, Silicones

Depending of your operational conditions: fluids?, temperature, etc you may try PVC (unplasticized), some kind of polyethlene(UHMW)or Polypropylene. Also may try some Rubber such as EPDM.

Again, check first your fluids, temperatures and pressures.

patprimmer · Sep 1, 2003

Polyesters are quite sensitive to hydrolysis, but much more so under alkaline conditions rather than acid. They are in fact quite resistant to even quite srong acids.

I wonder if the Polyester tube is actualy an ester based polyurthane, as this would be much more flexable than a PET or PBT type of polyester. PET and PBT (typicaly known as polyesters) are really to rigid to make a hose liner, unless they were very thin, like 10 or 20 microns I would think

Regards
pat

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