ISO 21173:2019

INTERNATIONAL ISO
STANDARD 21173
First edition
2019-08
Submersibles — Hydrostatic pressure
test — Pressure hull and buoyancy
materials
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General . 2
4.1 Test program . 2
4.2 Manufacturing requirements . 2
4.3 Test equipment and instruments . 2
4.4 Requirements for the test environment: . 3
4.5 Test sequence . 3
4.6 Test record . 3
4.7 Specification . 3
5 Detailed requirements . 3
5.1 Preparation before the tests . 3
5.2 Hydrostatic pressure test . 3
5.2.1 General. 3
5.2.2 Test pressurization and depressurization rates and holding time . 4
5.2.3 Hydrostatic pressure test of the pressure hull and its accessories
including viewports, hatches and connectors . 4
5.2.4 Hydrostatic pressure test of buoyancy materials . 6
5.2.5 Qualification testing of buoyancy material . 9
5.3 Optional tests . 9
5.3.1 General. 9
5.3.2 Strain test . 9
5.3.3 Continuous pressurization and depressurization test .10
5.4 Test results processing .11
5.5 Test report .11
Bibliography .12
Foreword
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iv © ISO 2019 – All rights reserved

Introduction
The document provides a unified specification for the hydrostatic pressure test method applicable to
the pressure hull and buoyancy materials of submersibles to confirm that their pressure resistance
performance is normal prior to assembly.
INTERNATIONAL STANDARD ISO 21173:2019(E)
Submersibles — Hydrostatic pressure test — Pressure hull
and buoyancy materials
1 Scope
This document specifies a test method for the hydrostatic pressure test for pressure hull and buoyancy
materials of submersibles. The test sequence comprises a tightness test and the hydrostatic pressure
test itself. It can also include continuous pressurization and depressurization tests, long-term static
load and cycling external pressure tests.
This document is applicable to the pressure structure of manned submersibles and unmanned
submersibles, including the pressure hull, its accessories (such as viewports, hatches and connectors)
and buoyancy materials. The long-term static load and cycling external pressure tests are only
applicable to buoyancy material.
This document is not applicable to submarines and other submersibles parking or operating underwater
for more than one week.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
submersible
vehicle operating underwater
3.2
manned submersible
submersible (3.1) occupied by persons
3.3
unmanned submersible
submersible (3.1) not occupied by persons
3.4
maximum working depth
maximum operating depth at which a submersible (3.1) can operate safely
Note 1 to entry: It is expressed in meters (m).
3.5
maximum working pressure
p
maximum pressure in which a system (pressure vessel, supporting controls and instrumentation) can
be operated
3.6
test pressure
p
t
water pressure endured by the pressure structure during the pressurization test or tightness test
Note 1 to entry: It is expressed in megapascals (MPa).
3.7
pressure hull
shell capable of withstanding the internal and/or an external pressure, in which occupants and the
required equipment are housed
3.8
viewport
penetration in the pressure vessel including a window, flange, retaining rings and seals
3.9
buoyancy material
material for a submersible (3.1), whose density is lower than that of the ambient medium
3.10
structural change
position which has a change in cross sectional area, structural configuration or other physical
characteristic
3.11
stress raiser
area where, due to the characteristics of the hull such as structural change (3.10), internal mounting,
reduced thickness due to constructional tolerances, additional loads, etc., a change in stress is likely
to occur
3.12
continuous pressurization and depressurization test
test in which the pressurization rate and depressurization rate keep the same values without any pause
for strain measurement
4 General
4.1 Test program
Prior to the test, the test program shall be prepared, including the test organization, test objective, test
equipment, inspection content, loading and unloading procedures, support conditions and test result
processing.
4.2 Manufacturing requirements
Tests shall be carried out on completion of assembly, welding of components and accessories, and
completion of heat treatment/post weld heat treatment, if applicable. The components and accessories
shall be assembled in place, provided with quality certificates for materials, manufacturing and
assembly.
4.3 Test equipment and instruments
a) The test equipment shall pass the certification, obtaining the qualifications of carrying out
hydrostatic pressure test within the validity period.
b) The test equipment and instruments shall pass the verification, which evaluates the metrological
performance of measuring instruments and determines whether they are certified or not. The
2 © ISO 2019 – All rights reserved

equipment and instruments shall be within the specified period of validity and be checked and
calibrated, and then remain in good condition before the test.
c) The test equipment and instruments shall be installed in the appropriate positions according to the
requirements of the test and to the relevant operating instructions, to prevent the test results from
being affected by the external environment during the test.
d) Two thirds of the range of the test pressure gauge shall not be less than the maximum test pressure.
4.4 Requirements for the test environment:
a) During the hydrostatic pressure test, the pressure medium temperature may be set as the room
temperature (10 °C to 30 °C). For viewports, the temperature of the pressurizing medium during
the test shall be the design temperature for which the viewport is rated, with a tolerance of +0/
−2,5 °C (+0/−5 °F). Brief deviations from these temperature tolerances are allowed, provided that
the deviation does not exceed 5,5 °C (10 °F) and lasts less than 10 min.
b) Atmospheric pressure: 0,084 MPa to 0,106 MPa.
c) Relative humidity: 30 % to 95 %.
d) Pressure medium: fresh water or seawater.
4.5 Test sequence
The hydrostatic pressure test of the submersible pressure structure consists of at least the following:
a) a prior tightness test;
b) the hydrostatic pressure test itself.
Optional testing includes strain measurement tests, and continuous pressurization and
depressurization tests.
4.6 Test record
All test checks shall be recorded, and relevant reports shall be filled in.
4.7 Spec
...