Estimating Movement Amounts

01.Center misalignment (movement from center)

Center misalignment occurs when one end of a double-sided joint (such as a flange joint, screw joint, union joint or coupling) is secured and the joint at the other end moves vertically up or down with a fixed horizontal length (planar movement).

02.Horizontal/vertical movement (line with U-shaped pipe/horizontal U-shaped pipe)

Radial motion is horizontal or vertical motion of the support point of an arc formed when a line is attached with a curve as shown in Figures A and B. Radial motion is generally known as a moving loop. The amount of movement is expressed by the distance that the support point moves horizontally or vertically. If total movement T is a known value and the curvature radius can be arbitrarily selected, the tube true length L and loop length K can be calculated by the formula shown.
Note: Total length = L + Metal fixture length

03.Permanent bends (fixed bends)

To make it easier to connect two line system components, lines are bent once and used in that state instead of using a normal bend. Lines must be attached with a bend radius of at least the permitted minimum bend radius. Use for handling line system thermal expansion or vibration damping is a misapplication (low pressure lines only).

04.Lines exhibiting disordered bend motion

For applications such as water-spraying hoses (garden hoses), bend stress becomes concentrated at the bases of metal fixtures, so spring coiling is recommended.

05.Prohibited movements

Applying axial direction displacement is prohibited on wires attached to tubes due to the braided covering. Braid-free lines can’t be used since tube buckling occurs. Using bellows-type expansion joints is recommended for axial-direction displacement.


Tubes must not be twisted.