I've been
trying to establish criteria for parts replacement on a number of items.
The latest of these would be hose assemblies.
Manufacturer guidelines place the burden for determining
useful life on the end user. It would also appear much more reliance is
placed on external visual inspection than I
would have expected in determining "condition" (SAE ARP 1658, "Visual
Inspection Guide for Installed Hose Assemblies"). Nowhere have I found a
criteria for determining the condition of the hose interior. Does anyone
have any experience in this area? What do the airlines or
maintenance shops use for replacement criteria?
from Aeroquip:
"The actual service
life of a given hose assembly, in a given application, is dependent on many
variable factors. These variable factors may include, but are not limited to,
operating pressure, pressure surges, flexing, operating temperatures (both
fluid and ambient), installed bend radius, cleaning solutions, ozone and
assembly routing. Due to the variety of operating conditions and applications,
the user, through their own analysis, testing and/or review of maintenance
records and data, is ultimately responsible for making the final selection, of
or decisions about replacement hose assemblies and assuring that all
performance, safety and warning requirements of the application are
met.
......
1. Normal
Duty Hoses
Typically, these are hose
assemblies in less demanding applications, such as in-body, in-wing or other
applications not normally exposed to the environment, cleaning fluids,
continuous temperature extremes, heavy pressure pulsation, etc., and having
infrequent maintenance actions associated with their installation. Recommended
Maintenance Approach: On Condition
2. Moderate or Heavy Duty
Hoses
Typically,
these are hoses exposed to more frequent maintenance activity or major system
removal, or hoses occasionally exposed to environmental conditions (e.g.,
upper wheel well hoses, APU hoses)
Recommended Maintenance Approach: Either On-Condition or based on user data
and maintenance records.
3. Demanding or Severe Duty
Hoses
Typically,
these are hoses continuously or routinely exposed to environmental, cleaning,
or other harsh operating variables
such as landing gear brake hoses, EDP
hoses, etc., and associated with major systems requiring regular removal,
repair or overhaul. Recommended Maintenance Approach: Strongly consider
replacement at time of major system overhaul."
Chris Zavatson
N91CZ
360std