When a Teflon hose has been in service for a time, what condition may have occurred and/or what precaution should be taken when it is temporarily removed from the aircraft?

When a Teflon hose has been in service for a time, what condition may have occurred and/or what precaution should be taken when it is temporarily removed from the aircraft?

• A. The hose may have developed a set, or have been manufactured with a pre-set shape, and must be supposed to maintain its shape.
• B. It may have expanded due to temperature.
• C. It may have contracted.
• D. It may have absorbed moisture and should be dried.

Answer: (A)

Teflon hoses can develop a set or arrive with a pre-set shape because PTFE tends to creep and remember a bend after long service or manufacturing forming. That means, once a hose has been bent into a route, it may not relax back to a straight configuration or to a different shape when you remove it. The safest way to handle it after temporary removal is to treat it as having a memory of its previous form: check that its bend and routing match the required path, and do not force it into a new, tighter bend or misalignment. If there is any noticeable deformation or if it cannot be installed in the correct orientation, replace it rather than trying to reshape it in service. Temperature changes and moisture absorption aren’t the primary concerns with PTFE hose in this context, since PTFE is relatively inert to moisture and the issue here is the potential permanent deformation from prior use.

Teflon hoses can develop a set or arrive with a pre-set shape because PTFE tends to creep and remember a bend after long service or manufacturing forming. That means, once a hose has been bent into a route, it may not relax back to a straight configuration or to a different shape when you remove it. The safest way to handle it after temporary removal is to treat it as having a memory of its previous form: check that its bend and routing match the required path, and do not force it into a new, tighter bend or misalignment. If there is any noticeable deformation or if it cannot be installed in the correct orientation, replace it rather than trying to reshape it in service. Temperature changes and moisture absorption aren’t the primary concerns with PTFE hose in this context, since PTFE is relatively inert to moisture and the issue here is the potential permanent deformation from prior use.