ISO/TS 21256-1:2020

TECHNICAL ISO/TS
SPECIFICATION 21256-1
First edition
2020-03
Fine bubble technology — Cleaning
applications —
Part 1:
Test method for cleaning salt (NaCl)-
stained surfaces
Technologie des fines bulles — Applications de nettoyage —
Partie 1: Méthode d’essai pour le nettoyage de surfaces dégradées par
le sel (NaCl)
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle of cleaning performance test. 1
5 Test apparatus for cleaning test . 2
5.1 High-pressure water jet . 2
5.1.1 Test conditions. 2
5.1.2 Characteristics of the high-pressure water jet . 2
5.2 Measuring instrument . 3
6 Salt-stained steel test plate for cleaning performance test . 3
7 Procedure. 3
7.1 General . 3
7.2 Measurement before cleaning the surface of the steel test plate . 3
7.3 Cleaning method of the surface of the steel test plate . 4
7.4 Measurement of salt stains after cleaning the surface of the steel test plate . 5
8 Calculation method of salt stain removal . 6
8.1 Calculation method of salt removal ratio . 6
8.2 Calculation method of salt removal quantity . 6
9 Test report . 6
Annex A (informative) Surface salinity meter . 8
Annex B (informative) Example of evaluation results for cleaning of steel bridge girder edges .9
Annex C (informative) Example of test result table.11
Bibliography .12
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
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 documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 281, Fine bubble technology.
A list of all parts in the ISO 21256 series can be found on the ISO website.
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iv © ISO 2020 – All rights reserved

Introduction
Salt and materials derived from other pollution sources are known to coat surfaces of exterior of
steel structures over time. Highway bridges and other steel structures are particularly vulnerable to
anti icing salts or ocean spray. It is necessary that this contamination be removed in order to prevent
growth of corrosion and to preserve the life time of the structure. Maintenance is conducted at times of
inspection, possibly via the erection of suitable scaffolding and platforms and therefore a rapid efficient
cleaning mechanism is essential.
High-pressure water sprays are commonly used for the cleaning method due to their hydrodynamic
power. The method requires the operator long term engagement to dangerous operation in inhospitable
environment.
It has been shown recently that cleaning process is much more effective and quicker once the water
used for the high-pressure spray is augmented with the addition of ultrafine bubbles (UFB) and that
markets of ultrafine bubble water or its generating systems are growing rapidly.
This document is intended to provide users of such products and systems with objective information
on the cleaning performance of ultrafine bubble water and to facilitate the improvement of ultrafine
bubble waters and their generating systems.
The test procedure correlates the ultrafine bubble enhanced performance with the presence of
ultrafine bubbles under standardized conditions based on the most commonly used criteria such as
hydrodynamic characteristics of high-pressure water spray, quality of raw water before mixing with
ultrafine bubbles, quality of salt stain, quality and dimension of coating and substrate of test steel
material and testing environmental conditions.
In this document, the presence of ultrafine bubbles is evaluated by measuring their sizes and number
concentrations. The performance of the method is assessed by measuring the change in removal of salt
from the test sample surface due to application of the ultrafine bubble water relative to that of plain
water as control. Example application of the test procedure demonstrates the test results on various
steel bridges long exposed to environments of express ways.
This document is intended to be used as a guidance for conducting tests and gathering more data to
develop an International Standard.
TECHNICAL SPECIFICATION ISO/TS 21256-1:2020(E)
Fine bubble technology — Cleaning applications —
Part 1:
Test method for cleaning salt (NaCl)-stained surfaces
1 Scope
This document describes the test method to evaluate the cleaning performance of ultrafine bubble
water when used in high-pressure water jet to wash out salt-stained steel surfaces.
The evaluation is carried out by measuring comparative removal of salt stain from the surface of a test
plate with the ultrafine bubble water to that with control water.
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 20480-1, Fine bubble technology — General principles for usage and measurement of fine bubbles —
Part 1: Terminology
ISO 20480-2, Fine bubble technology — General principles for usage and measurement of fine bubbles —
Part 2: Categorization of the attributes of fine bubbles
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20480-1, ISO 20480-2 and the
following 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
high-pressure water jet
equipment that forces water out of a small orifice at high speed
3.2
control water
blank water
water used as reference in comparative test on the ultrafine bubble water
4 Principle of cleaning performance test
Cleaning of salt stains is performed using water containing ultrafine bubbles that are uniformly
distributed in the water medium.
The characteristics to define the ultrafine bubble water are the diameter and the density distribution
of ultrafine bubbles.
The performance of the cleaning test is dependent in principle on the characteristics of the ultrafine
bubble water and the hydrodynamic performance of the high-pressure water jet as well as the
characteristic of the salt stains and the test environment.
In the test method, the characteristics of the high-pressure water jet, the salt stains and the test
environment are fixed, while the ultrafine bubble characteristics are modified to assess how ultrafine
bubbles can enhance performance.
The change in performance is assessed by measuring the density of salt stains after removal by high-
pressure water jet using ultrafine bubble water and control water.
5 Test apparatus for cleaning test
5.1 High-pressure water jet
5.1.1 Test conditions
A high-pressure water jet is used to carry out the cleaning test, as shown in Figure 1.
The test conditions are as follows:
a) high-pressure water jet nozzle: inner diameter 6 mm at outlet;
b) water temperature: 15 °C to 25 °C.
Key
1 nozzle of high-pressure water jet
2 water flow
3 steel test plate
Figure 1 — Salt removal method using a high-pressure water jet
5.1.2 Characteristics of the high-pressure water jet
The characteristics of the high-pressure water jet should be as follows.
a) The high-pressure cleaning machine should have an outlet pressure from 5 MPa to 9 MPa and the
amount of outlet cleaning liquid should range from 300 l/h to 400 l/h. The cleaning width on the
target should be stable, between 250 mm and 300 mm at a distance of 2 m from the outlet gate.
b) Ultrafine bubble water should be continuously supplied to the high-pressure water jet during the
cleaning test.
2 © ISO 2020 – All rights reserved

5.2 Measuring instrument
After removal, the adherent salt stains on the test plate shall be measured using a surface salinity meter
to perform density measurements.
The following conditions apply:
a) the surface salinity density is measured based on the
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