TASK 20-11-05-358-404
12. Repair Hydraulic Tubing With Flexible Hoses___________________________________________
A. General
(1)
The Boeing Company recommends that the operator do these procedures:
(a)
Make a record of the flexible hoses that you install as temporary repairs for rigid lines.
(b)
Make a schedule for the regular inspection of flexible hose installations. Make sure the installation stays an airworthy repair until the system is put back to its initial configuration.
(c)
Make a procedure to make sure the flexible hoses that are installed as temporary repairs are replaced as soon as possible. You must replace the hoses no later than the scheduled time check approved by the assigned principal maintenance inspector.
(2)
You can use many different repair techniques. The Boeing Company cannot know about or control these repair techniques. It is your responsibility to decide if this procedure is applicable to your repair techniques.
(3)
This procedure is not acceptable for engine hydraulic tube repair or for the replacement of rigid or flexible coiled tubing. Engine hydraulic tubes are those tubes below or forward of the firewall, and within the engine cowls. Consult Boeing when considering a repair to any Engine Hydraulic or coiled tube.
B. References
(1) AMM 29-11-00/201, Main Hydraulic Systems
C. Consumable Materials
(1) Hydraulic Tubing Repair Kit - P/N 65-92528-1 or
equivalent
D. Install the Flexible Hose
S 228-405
(1) Use a flexible hose that has the specifications that follow:
(a) Make sure the flexible hose is specified for at least the same operating pressure and fluid type as the system in which you will install the flexible hose.
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MAINTENANCE MANUAL
(b)
Make sure the new flexible hose has a minimum of the same inner diameter as the damaged tube.
(c)
Make sure the new flexible hose is sufficiently long to replace the damaged tube or the damaged section of the tube.
(d) Make sure the new flexible hose has sufficient slack, flex, twisting, bending, clearance, and support specifications as shown below and on Fig. 831. 1) Slack - Do not install the hose assemblies in a way that will cause a mechanical load on the hose. Hoses will change length from +2 to -4 percent when pressurized. Supply sufficient slack or bend to make the allowance for a change in length and length tolerances. 2) Flex - When hose assemblies will have much vibration or flexing, make sure there is sufficient slack between the rigid fittings. Install the hose so flexing does not occur at the end fittings. The hose must stay straight for at least two hose diameters from the end fittings. Do not use clamp locations that will restrict or prevent the hose from flexing. 3) Twisting - Make sure you install the hoses without twists to prevent loose nuts and possible rupture of the hose. You can use swivel connections at one or two ends to release the twist stresses.
4) Bending - To prevent sharp bends in the hose assembly, use elbow fittings, hose with elbow type end fittings, or the applicable bend radii, as shown in Table 1.
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| TABLE 1 |
.................................................................
| | | MINIMUM HOSE BEND |
| AS 115 | HOSE INNER | RADIUS MEASURED AT |
| HOSE | DIAMETER (INCH) | INNER BEND (INCH) |
................................................................. | .04 | 1/4 | 1.50 | | .06 | 3/8 | 2.50 | | .08 | 1/2 | 2.88 | | .10 | 5/8 | 3.25 | | .12 | 3/4 | 4.00 | 2............…......................…...........................1
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