EN ISO 16784-2:2008

SLOVENSKI STANDARD
01-julij-2008
.RUR]LMDNRYLQLQ]OLWLQ.RUR]LMDLQREUDãþDQMHYLQGXVWULMVNLKYRGQLKKODGLOQLK
VLVWHPLKGHO9UHGQRWHQMHXþLQNRYLWRVWLSURJUDPRYREGHORYDQMDVKODGLOQR
WHNRþLQR]XSRUDERRSUHPH]DSUHVNXãHYDOLãþDSLORWQHVHULMH,62
Corrosion of metals and alloys - Corrosion and fouling in industrial cooling water systems
- Part 2: Evaluation of the performance of cooling water treatment programmes using a
pilot-scale test rig (ISO 16784-2:2006)
Corrosion des métaux et alliages - Corrosion et entartrage des circuits de
refroidissement a eau industriels - Partie 2: Évaluation des performances des
programmes de traitement d'eau de refroidissement sur banc d'essai pilote (ISO 16784-
2:2006)
Ta slovenski standard je istoveten z: EN ISO 16784-2:2008
ICS:
77.060 Korozija kovin Corrosion of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 16784-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2008
ICS 77.060
English Version
Corrosion of metals and alloys - Corrosion and fouling in
industrial cooling water systems - Part 2: Evaluation of the
performance of cooling water treatment programmes using a
pilot-scale test rig (ISO 16784-2:2006)
Corrosion des métaux et alliages - Corrosion et entartrage Korrosion von Metallen und Legierungen - Korrosion und
des circuits de refroidissement à eau industriels - Partie 2: Fouling in industriellen Kühlwassersystemen - Teil 2:
Évaluation des performances des programmes de Bewertung der Leistung von Kühlwasser-
traitement d'eau de refroidissement sur banc d'essai pilote Behandlungsprogrammen unter Anwendung eines Modell-
(ISO 16784-2:2006) Prüfstands (ISO 16784-2:2006)
This European Standard was approved by CEN on 21 March 2008.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16784-2:2008: E
worldwide for CEN national Members.

Contents Page
Foreword.3

Foreword
The text of ISO 16784-2:2006 has been prepared by Technical Committee ISO/TC 156 “Corrosion of metals
and alloys” of the International Organization for Standardization (ISO) and has been taken over as EN ISO
16784-2:2008 by Technical Committee CEN/TC 262 “Metallic and other inorganic coatings” the secretariat of
which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by October 2008, and conflicting national standards shall be withdrawn at
the latest by October 2008.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 16784-2:2006 has been approved by CEN as a EN ISO 16784-2:2008 without any
modification.
INTERNATIONAL ISO
STANDARD 16784-2
First edition
2006-01-15
Corrosion of metals and alloys —
Corrosion and fouling in industrial
cooling water systems —
Part 2:
Evaluation of the performance of cooling
water treatment programmes using a
pilot-scale test rig
Corrosion des métaux et alliages — Corrosion et entartrage des circuits
de refroidissement à eau industriels —
Partie 2: Évaluation des performances des programmes de traitement
d'eau de refroidissement sur banc d'essai pilote

Reference number
ISO 16784-2:2006(E)
©
ISO 2006
ISO 16784-2:2006(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO 2006
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2006 – All rights reserved

ISO 16784-2:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 3
5 Reagents and materials . 3
5.1 Water characteristics. 4
5.2 Preparation of synthetic test waters using mother solutions. 4
6 Apparatus . 5
6.1 Temperature measurement. 5
6.2 Circulation-rate monitor. 5
6.3 Make-up, evaporation and blow-down measurement. 5
6.4 Cooling tower. 5
7 Test method. 6
7.1 Procedure . 6
7.1.1 Cleaning of the test assembly. 6
7.1.2 Test tube preparation and pre-treatment . 6
7.1.3 System water content. 6
7.1.4 Procedure to fill the cooling water system . 6
7.1.5 Heating the test tubes . 7
7.1.6 Flow rate . 7
7.1.7 Blow-down and half-life. 8
7.1.8 Biocide treatment. 8
7.1.9 Make-up water for cooling-tower use . 8
7.2 Determination of analytical and control parameters. 8
7.3 Test data reporting . 9
7.4 Test termination. 9
8 Assessment of results. 9
8.1 Recording of cooling water quality. 9
8.2 Treatment of the test tubes. 9
8.3 Assessment of results on deposition and fouling . 9
8.4 Assessment of results on corrosion . 10
9 Test report . 11
Annex A (informative) Test data sheet on the performance of cooling water treatment
programmes . 12
Annex B (informative) Further information on some methods of measurement and test. 15
Bibliography . 19

ISO 16784-2:2006(E)
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 through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 16784-2 was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys.
ISO 16784 consists of the following parts, under the general title Corrosion of metals and alloys — Corrosion
and fouling in industrial cooling water systems:
— Part 1: Guidelines for conducting pilot-scale evaluation of corrosion and fouling control additives for open
recirculating cooling water systems
— Part 2: Evaluation of the performance of cooling water treatment programmes using a pilot-scale test rig
iv © ISO 2006 – All rights reserved

ISO 16784-2:2006(E)
Introduction
Due to more stringent environmental requirements and escalating costs of water, there is an industrial need to
improve the safety, reliability and cost-effectiveness of open recirculating cooling water systems.
Correspondingly, it is important to establish a standard framework for evaluating the performance of cooling
water treatment programmes. The aim is to provide users of cooling systems and vendors of treatment
materials for those systems with a procedure to make consistent evaluations of cooling water treatment
programmes on a pilot scale.
INTERNATIONAL STANDARD ISO 16784-2:2006(E)

Corrosion of metals and alloys — Corrosion and fouling in
industrial cooling water systems —
Part 2:
Evaluation of the performance of cooling water treatment
programmes using a pilot-scale test rig
1 Scope
This part of ISO 16784 applies to corrosion and fouling in industrial cooling water systems
This part of ISO 16784 describes a method for preliminary evaluation of the performance of treatment
programmes for open recirculating cooling water systems. It is based primarily on laboratory testing but the
heat exchanger testing facility can also be used for on-site evaluation. This part of ISO 16784 does not include
heat exchangers with cooling water on the shell-side (i.e. external to the tubes).
2 Normative references
The following referenced documents are indispensable for the application 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 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 8407:1991, Corrosion of metals and alloys — Removal of corrosion products from corrosion test
specimens
ISO 8501-1:1988, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel
substrates and of steel substrates after overall removal of previous coatings
ISO 11463:1995, Corrosion of metals and alloys — Evaluation of pitting corrosion
3 Terms, abbreviations and definitions
For the purposes of this document, the following terms, abbreviations and definitions apply.
3.1
ATP
adenosine tri-phosphate, an active chemical present in living bacteria
NOTE ATP concentrations can be indirectly measured and are used as an indicator for the presence of biology in
cooling water
ISO 16784-2:2006(E)
3.2
blow-down
discharge of water from the cooling water circuit expressed as a discharge rate
3.3
Cfu
colony forming units which are a unit of measure for the amount of bacteria in cooling water
3.4
cooling tower
tower used for evaporative cooling of circulating cooling water, normally constructed of wood, plastic,
galvanized metal or ceramic materials
3.5
cooling water treatment
adjustment of cooling water chemistry by which corrosion and fouling can be controlled
3.6
cycles of concentration
ratio of the concentration of specific ions in the circulating cooling water to the concentration of the same ions
in the make-up water
3.7
heat rejection capacity
amount of heat that can be rejected by a cooling-tower system
3.8
half-life
time needed to reduce the initial concentration of a non-degradable and/or non-precipitable compound to
50 % of its concentration in the cooling water
3.9
make-up water
total water mass per time unit, which is added to the system to compensate for the loss of water due to
evaporation, blow-down, leakage and drift loss
3.10
Reynolds number
LV ρ
dimensionless form, which is proportional to the ratio of inertial force to viscous force in a flow system
η
where:
L is the characteristic dimension of the flow system, expressed in metres (m)
V is the linear velocity, expressed in metres per second (m/s)
ρ is the fluid density, expressed in kilograms per cubic metre (kg/m )
η is the fluid viscosity, expressed in kilograms per metre per second (kg/m/s)
3.11
surface temperature
temperature of the interface between the cooling water film and the heat-transfer surface, whether the surface
be the tube wall or the outside of a fouling deposit
3.12
TOC
total organic carbon
2 © ISO 2006 – All rights reserved

ISO 16784-2:2006(E)
3.13
tower fill
portion of a cooling tower, which constitutes its primary heat-transfer surface, over which water flows as
evaporation occurs
3.14
wall shear stress
shear stress of the fluid film immediately adjacent to the tube wall
NOTE The wall shear stress is expressed in N/m .
3.15
wall temperature
temperature sensed by a thermocouple placed between the heater element and the inside of the heat-transfer
tube wall, preferably as close to the tube wall as possible
4 Principle
A test assembly of metallic test tubes is submitted under heat-transfer conditions to the circulation of cooling
water for a specified period. This may be connected directly to the cooling water system on-site, to be
representative of service conditions. For laboratory testing, the cooling water composition is designed to
reflect the chemistry for the service application but modified with the appropriate treatment programme under
investigation. The adoption of synthetic chemistry in laboratory tests can be effective for comparative
purposes, e.g. screening, but will not be representative of service conditions. The effect of the cooling water
circulation and the treatment programme on the corrosion and fouling of the test tubes is assessed using a
number of measurement parameters.
5 Reagents and materials
The cooling water composition of the test should reflect the likely service application. For laboratory testing
using synthetic water, only reagents of recognized analytical grade and only water complying with the
minimum requirements of grade 3 of ISO 3696 shall be used.
There are two main operating environments, which may be adopted. The first is to use the make-up water as
used in the specific cooling system on-site (a variation on this is to use synthetic make-up water), and
concentrate it to the required number of cycles in the test system. Annex A includes forms recommended for
recording test conditions, compositions of make-up and recirculating water, and test results.
The second approach involves using a synthetic water simulating the on-site circulating water for the required
number of cycles. The use of synthetic circulating water obviates the need to concentrate the synthetic water
to obtain the desired cycles of concentration. This approach simplifies the test by avoiding the use of the pilot
cooling tower.
Synthetic circulating water will usually contain a higher level of dissolved ionic solids than corresponding
natural water, thus making the synthetic water more corrosive.
ISO 16784-2:2006(E)
5.1 Water characteristics
The natural or synthetic water(s) used should be characterized as specified in Table 1.This Table should be
used to record compositions of both the circulating water and the make-up water, if used. Turbidity, total silica,
bacteria and ATP need only be measured for on-site waters.
Table 1 — Composition of make-up and circulating cooling water
No. Component Value Units
1 pH pH units
2 Conductivity µS/cm
a
3 Total hardness
a
4 Alkalinity – p
a
5 Alkalinity – m
2+
6 Ca mg/l
2+
7 Mg mg/l
+
8 Na mg/l
+
9 K mg/l
+
10 NH mg/l
2+
11 Fe mg/l
2+
12 Cu mg/l
3+
13 Al mg/l
2-
14 CO mg/l
-
15 HCO mg/l
-
16 Cl mg/l
2-
17 SO mg/l
-
18 NO mg/l
3-
19 PO mg/l
20 SiO mg/l
21 Cl mg/l
22 Turbidity FTU or NTU
23 Suspended solids mg/l
24 Bacteria UFC/ml or UFC/l
25 ATP RLU
a
The unit of measurement will depend on the test method.

5.2 Preparation of synthetic test waters using mother solutions
Synthetic test waters are normally prepared in the laboratory at the time of use by mixing mother or stock
solutions. One mother solution contains the alkalinity. The other mother solution contains the hardness and
other salts required in the test water The composition of these two solutions is calculated so that, when the
solutions are mixed in the proper proportion, they prepare either the circulating test water or an appropriate
make-up water. Typical mother solutions are shown in B.1. Alternatively, mother solutions may be prepared as
concentrates and subsequently diluted with demineralised water.
4 © ISO 2006 – All rights reserved

ISO 16784-2:2006(E)
6 Apparatus
The core of the test assembly is the heat exchanger section - described further in 6.1 to 6.4. The test
assembly comprises two or more metal heat-transfer tubes, made of the relevant alloy used in the on-site heat
exchanger, mounted in series (Figure B.1) or in parallel (Annex B.3, Figure B.2). Conduction and convection
of electrically generated heat occurs through the heat-transfer tube wall into the circulating cooling water. The
materials-of-construction of the test assembly shall be chosen so as not to influence the composition of the
test water. Glass or plastic [(e.g., poly(vinyl chloride) (PVC), chlorinated poly(vinyl chloride) (CPVC) or
poly(vinylidene fluoride) (PVDF)] are commonly used.
From the cooling water reservoir, the cooling water is pumped through the heat exchanger section at a
controlled flow rate. If the heat transfer tubes are mounted in series, only one flow rate controller is required. If
they are mounted in parallel, one flow rate controller is required for each heat exchange tube. Through partial
evaporation of water in a cooling tower (6.4), the heat absorbed is subsequently released to the environment.
Alternatively, if a cooling tower is not required to concentrate make-up water, a closed cooling loop to extract
heat is used. In order to determine corrosion rates on non-heat-transfer surfaces, corrosion coupons (flush
mounted probes) of the relevant metals in the system should be used.
If the heat exchange tubes are mounted in parallel, simultaneous tests may be run by setting a different
combination of surface temperature and flow rate for each heat exchange tube. However, it is highly
recommended that all of the heat-transfer tubes be of the same metallurgical composition.
6.1 Temperature measurement
The wall temperature of the metal tubes should be measured by a thermocouple placed between the heater
element and the inside of the heat-transfer tube wall, preferably as close to the tube wall as possible. Because
of temperature gradients, this measurement will not be fully accurate but will be indicative. More accurate
determination would require three thermocouples mounted at varying distances from the tube wall, with the
temperature gradient used to determine the temperature at the wall.
6.2 Circulation-rate monitor
The circulation rate can be measured by use of a flow meter in the flow line, either preceding or following the
heat exchange tubes.
6.3 Make-up, evaporation and blow-down measurement
A means for measuring the mass flow of make-up, the amounts of evaporation and blow-down water
(including minimum, average and maximum values) shall be established and shall be included in the test
report. In essence, blow-down and make-up rates can be monitored by water meters and the evaporation rate
deduced. Chemical feed may be based on blow-down or make-up. Blow-down is normally controlled using the
conductivity of the circulating water. Make-up is controlled by a level controller in the cooling-tower basin.
6.4 Cooling tower
The design and heat rejection capacity of the cooling tower and tower fill are optional but shall be reported.
Deposition of salts in the cooling tower may occur depending on the system design. An example of the
apparatus is described in B.2. A visual inspection of the inside of the cooling tower at the end of the test is
advised.
ISO 16784-2:2006(E)
7 Test method
7.1 Procedure
7.1.1 Cleaning of the test assembly
Before starting a test, the test assembly shall be cleaned in order to prevent contamination with products from
a possible previous test or undesirable microbiological fouling.
The following cleaning solutions are suggested: first, flushing with water, then flushing out with an appropriate
solution, such as hypochlorite solution in the case of slime formation, sulfamic acid or citric
...