Module 7.9-7.13 Pipes and hoses, springs, bearings, transmissions and control cables (practices)

These sub-modules cover the maintenance practices for the hardware described in Module 6.6-6.10. B2/B2L are not examined on them.

Knowledge levels

Sub-module	A	B1 / B3	B2 / B2L
7.9 Pipes and hoses	1	2	—
7.10 Springs	1	2	—
7.11 Bearings	1	2	—
7.12 Transmissions	1	2	—
7.13 Control cables	1	2	—

7.9 Pipes and hoses

Bending

• Bend rigid tubes with a hand or production tube bender of the correct size; the bend must be smooth with no kinks, wrinkles or excessive flattening (flattening limit typically 75 % of original diameter remaining minimum).
• Observe the minimum bend radius for the tube size and material.

Flaring and beading

• Single flare (37° AN) for most aluminium and steel tubes; double flare for soft aluminium tubes up to about 3/8 in OD (stronger, better seal, resists shearing).
• Cut the tube square with a tube cutter, deburr inside and outside, slide on the nut and sleeve before flaring.
• Flare must be concentric, without cracks or splits, and of correct diameter (not overflared).
• Beading (a raised ridge near the tube end) retains hoses/clamps on low-pressure lines.
• Flareless fittings: the sleeve is pre-set (presetting tool or fitting body) so it bites into the tube, then installed to the specified torque or number of turns.

Inspection and testing

• Look for dents, nicks, scratches, chafing, corrosion, leaks, cracked flares, loose fittings. Dent and scratch limits (e.g. depth limits as a % of wall thickness, dents under 20 % of diameter outside bends - per manual) decide repair or replacement.
• Hoses: check for blisters, cracking, kinks, abrasion of the braid, leaks, age limits, twisting (lay line).
• After installation, pressure test to the specified test pressure and check for leaks; never tighten a fitting under pressure.

Installation and clamping

• Support lines with cushioned clamps at specified intervals; keep clearance from controls, structure and wiring; do not use a fitting to pull a tube into alignment (pre-load cracks the flare).
• Hoses: allow 5-8 % slack (hoses shorten under pressure), no twist, minimum bend radius observed, fire sleeves in fire zones.