ISO 7661:2024

International
Standard
ISO 7661
Second edition
Aerospace fluid systems —
2024-10
Clamp blocks for tube lines
having axial alignment — Design
requirements and qualification
testing (metric series)
Systèmes de fluides pour l'aéronautique et l'espace — Peignes
supports de tuyauteries à alignement axial — Exigences de
conception et essais de qualification (série métrique)
Reference number
© ISO 2024
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification of clamp blocks . 3
5 Dimensions of clamp blocks . 4
5.1 Maximum height .4
5.2 Nominal radius .4
5.3 Width of removable parts .4
5.4 Clamp block bolt spacing .5
5.4.1 Modular clamp block.5
5.4.2 Monobloc clamp block .5
6 Temperature conditions . 5
7 Qualification tests . 5
7.1 Electrical tests (for clamp blocks with electrical grounding) .5
7.1.1 Measurement of the electrical contact resistance .5
7.2 Mechanical tests .6
7.2.1 Sliding test under temperature .6
7.2.2 Sliding test combined with contamination .7
7.2.3 Vibration test .8
7.3 Climatic tests . .9
7.3.1 General .9
7.3.2 Low temperature test .9
7.3.3 High temperature test .9
7.3.4 Salt spray test .9
7.4 Flame resistance test .9
7.4.1 General .9
7.4.2 Test apparatus .9
7.4.3 Test procedure.10
7.4.4 Acceptance criteria .10
Bibliography .12

iii
Foreword
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The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
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Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 10, Aerospace fluid systems and components.
This second edition cancels and replaces the first edition (ISO 7661:1984), which has been technically
revised.
The main changes are as follows:
— the reference to ISO/TR 2685 has been updated in 7.4 and in the bibliography because ISO/TR 2685 has
been replaced by ISO 2685;
— Clause 2, normative references, has been updated;
— Clause 3, terms and definitions, has been updated;
— the upper limit of the tube outside diameters range has been increased from 32 mm to 36 mm.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
International Standard ISO 7661:2024(en)
Aerospace fluid systems — Clamp blocks for tube lines having
axial alignment — Design requirements and qualification
testing (metric series)
1 Scope
This document describes clamp blocks for tube lines having axial alignment, with or without electrical
grounding, designed for a range of tube outside diameters from 4 mm to 36 mm selected from ISO 2964.
This document specifies the dimensions of clamp blocks and the test methods for qualification testing.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 6771, Aerospace — Fluid systems and components — Pressure and temperature classifications
ISO 7137, Aircraft — Environmental conditions and test procedures for airborne equipment
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
axial alignment
axes of supported tubings located in the same plane
3.2
clamp block for tubing
device used on aerospace vehicles for fixing tubings, the dimensions of which may be different and which
are constituted from different materials.
Note 1 to entry: These clamp blocks permit the fastening of tubes, used for different purposes in fluid systems.
3.2.1
monobloc clamp block
clamp block for tubing (3.2) consisting of two monobloc parts
EXAMPLE See Figure 1.
Dimensions in millimetres
Key
1 upper part
2 lower part
R radius of tube support
H height of clamp block
a
See ISO 5855-2.
b
Bolt spacing ±0,125.
c
Width of tube support.
Figure 1 — Monobloc clamp block
3.2.2
modular clamp block
clamp block for tubing (3.2) consisting of removable parts (3.3), with or without insert(s) (3.4)
EXAMPLE See Figure 2.
Key
1 upper part
2 lower part
R radius of tube support
H height of clamp block
L length of part X
x
L length of part Y
y
L length of part Z
z
a
See ISO 5855-2.
b
Bolt spacing ±0,125.
c
Width of tube support.
Figure 2 — Modular clamp block (without insert)
3.3
removable part
part of a modular clamp block (3.2.2) which ensures a standardized clearance between two adjacent tubings
3.4
insert
part that can be assembled between two removable parts (3.3) in order to obtain the required centre-to-
centre distance, standardized or not, between tubes
4 Classification of clamp blocks
The clamp blocks are divided into three classes, A, B and C, each corresponding to a range of tube outside
diameters and to a maximum clamp block height (see Table 1), as follows:
Class A: tube outside diameters from 4 mm to 12 mm
Class B: tube outside diameters from 4 mm to 20 mm
Class C: tube outside diameters from 4 mm to 36 mm

5 Dimensions of clamp blocks
5.1 Maximum height
Table 1 gives, for each clamp block class and for each tube outside diameter, the maximum height, H, of the
clamp block (see Figures 1 and 2).
Table 1 — Maximum height of the clamp block
Dimensions in millimetres
Tube outside diameter
Identification
class of the 04 05 06 08 10 12 14 16 20 25 32 36
clamp block
Maximum height of the clamp block, H
A 27 27 27 27 27 27
B 35 35 35 35 35 35 35 35 35
C 48,5 48,5 48,5 48,5 48,5 48,5 48,5 48,5 48,5 48,5 48,5 48,5
5.2 Nominal radius
Table 2 gives, for each tube outside diameter, the nominal radius R, of the clamp block (see Figures 1 and 2).
Table 2 — Nominal radius of the clamp block
Dimensions in millimetres
Tube outside
04 05 06 08 10 12 14 16 20 25 32 36
diameter
Nominal radius,
2 2,5
...