ISO 13577-3:2016

DRAFT INTERNATIONAL STANDARD
ISO/DIS 13577-3
ISO/TC 244 Secretariat: JISC
Voting begins on: Voting terminates on:
2014-07-07 2014-10-07
Industrial furnace and associated processing
equipement — Safety —
Part 3:
Generation and use of protective and reactive atmosphere
gases
Fours industriels et équipements associés — Sécurité —
Partie 3: Génération et utilisation des gaz d’atmosphère protectrice et réactive
ICS: 13.100;25.180.01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 13577-3:2014(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2014

ISO/DIS 13577-3:2014(E)
Copyright notice
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ii © ISO 2014 – All rights reserved

ISO/DIS 13577-3
Contents Page
1 Scope.1
2 Normative References.2
3 Terms and definitions .3
4 Safety Requirements, Measures and Verification Means.6
4.1 Pipework.6
4.1.1 General .6
4.1.2 Connections.7
4.1.3 Unconnected pipework.8
4.1.4 Galvanic cells.8
4.1.5 Flexible tubing and couplings.8
4.1.6 Marking of pipework.8
4.1.7 Soundness/Tightness .8
4.1.8 Condensate drains .9
4.1.9 Purge points.9
4.1.10 Blow-off and breather pipes or conduits .9
4.1.11 Pressure relief devices and flame arrestors on pipework .9
4.1.12 Pressure oscillations .9
4.1.13 Combustible fluid by-pass .9
4.1.14 Isolation of required safety devices .10
4.1.15 Drainage points .10
4.1.16 Vents.10
4.2 Required safety devices .10
4.2.1 Gas control equipment .10
4.2.2 Marking of devices .14
4.2.3 Other safety devices .14
4.3 Requirements for the use of protective or reactive atmosphere .15
4.3.1 Prevention of potential explosive atmospheres .15
4.3.2 Monitoring of TPE doors movements and process openings.16
4.3.3 Supervision of the means of ignition at the point of combustible gas discharge.17
4.3.4 Emergency safety purge.17
4.4 Change of atmosphere.17
4.4.1 Purge with purge gas.18
4.4.2 Purge with self-ignition.18
4.4.3 Change of atmosphere by burning.19
4.4.4 Purge by evacuation .19
4.5 Interfaces to exhaust systems for combustible or toxic atmosphere gases.19
4.5.1 Exhaust of burned gases.19
4.5.2 Gathering of gases without burning and a closed system .20
5 Additional requirements for the generation of protective and reactive atmosphere gases.21
5.1 Fluid supplies .21
5.1.1 Source gas supplies.21
5.1.2 Air supplies .21
5.1.3 Reaction mixture supplies.21
5.1.4 Generated gas distribution.21
5.2 Flame detection .22
5.3 Gas atmospheric generating burners .22
5.4 Special requirements for different types of generator .22
5.4.1 Requirements for endothermic generators .22
5.4.2 Requirements for exothermic generators.23
5.5 Post-treatment of generated Gases.23
ISO/DIS 13577-3
6 Verification of the safety requirements and/or measures . 23
7 27
7 Information for Use. 27
7.1 General. 27
7.2 Marking . 27
7.3 Instruction handbook . 27
7.3.1 General. 27
7.3.2 Description of equipment . 28
7.3.3 Inspection procedures . 28
7.3.4 Commissioning, start-up and operating procedures. 28
7.3.5 Shutdown procedures. 29
7.3.6 Maintenance procedures . 29
7.3.7 Documentation. 30
Annex A (informative) List of significant hazards. 31
Annex B (informative) Typical protective and reactive atmosphere gases. 32
Annex C (normative) Allowed maximum pressure. 33
Annex D (informative) Principle procedures for the change of atmosphere. 38
Annex E (informative) Examples for the determination of safety integrity level SIL using the risk
graph method. 39
Annex F (informative) Basic configuration of Piping system of TPE using protective or reactive
atmosphere gases . 53
Annex G (normative) Requirements specific to Japan. 55
G.1 General. 55
G.2 Background. 55
G.3 References. 55
G.4 Requirements. 56
Annex H (normative) Requirements specific to USA. 57
H.1 General. 57
H.2 Background. 57
H.3 Normative references . 57
H.4 Requirements. 57
Annex I (normative) Requirements specific to European countries . 58
I.1 General. 58
I.2 Background. 58
I.3 Normative references . 58
I.4 Requirements. 58

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ISO/DIS 13577-3
Figures Page
Figure C.1 — Piping referred to in clause a) group 1 of Annex C.34
Figure C.2 — Piping referred to in clause a) group 2 of Annex C.35
Figure C.3 — Piping referred to in clause b) group 1 of Annex C.36
Figure C.4 — Piping referred to in clause b) group 2 of Annex C.37
Figure D.1 — Principle procedures for the change of atmosphere.38
ISO/DIS 13577-3
Tables Page
Table 1 — Verification of the safety requirements and/or measures . 23
Table A 1 — List of significant hazards . 31
Table B 1 — Typical protective and reactive atmosphere gases . 32
Table E 1 - Example of SIL determination according to IEC 62061 for a multi chamber furnace at an inside
temperature > 750°C . 40
Table E 2 - Example of PL determination according to ISO 13849-1 for a multi-chamber furnace at an inside
temperature > 750°C . 46
Figure F 1 - Basic configuration of piping system of TPE using protective or reactive atmosphere gases . 53

vi © ISO 2014 – All rights reserved

ISO/DIS 13577-3
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 13577-3 was prepared by Technical Committee ISO/TC 244, Industrial funaces and associated
processing equipment, Subcommittee SC , .
This second/third/. edition cancels and replaces the first/second/. edition (), [clause(s) / subclause(s) /
table(s) / figure(s) / annex(es)] of which [has / have] been technically revised.
ISO 13577 consists of the following parts, under the general title Industrial furnaces and associated
processing equipment — Safety:
 Part 1: General requirements;
 Part 2: Combustion and fuel handling systems
 Part 3: Generation and use of protective and reactive atmosphere gases
 Part 4: Protective Systems
ISO/DIS 13577-3
Introduction
This document is a Type C-Standard as defined in ISO 12100.
The machinery concerned and the extent, to which hazards, hazardous situations and events are covered, is
indicated in the scope of this document.
When provisions of this type C standard are different from those which are stated in type A or B standards, the
provisions of this type C standard take precedence over the provisions of the other standards, for machines
that have been designed and built according to the provisions of this type C standard.
This DIS 13577-3 assumes that the equipment is not creating any potentially explosive atmosphere and is
located in a normally ventilated area.
Compliance with product standards e. g. ISO 22967 or ISO 22968 is not sufficient to ensure the minimum
safety requirement for TPE. This DIS shall always have priority for TPE.
Industrial Furnaces and Associated Processing Equipment (TPE) generally consists of the following
components:
 Processing chamber (e.g. steel construction with lining and/or refractory)
 Heating systems
 Protective system
 Control and instrumentation system / operator-control level
TPE cover e.g. gas generators, vaporizer, dissociators, pre- and post treatment equipment.
ISO 13577-1 provides the general safety requirements common to TPE. This part of ISO 13577 details in
addition specific safety requirements for generation and use of protective and reactive fluids that are part of
TPE as listed in the scope. These requirements establish the minimum acceptable requirements for safety
functions required for various processes. Where a process is not part of the TPE, the requirements do not
apply.
Example: the minimum requirements for the opening and closing of doors on a TPE, does not apply to TPE
that do not have doors in their design.
NOTE As stated in its scope, ISO 13577-1 does not cover blast furnaces, converters (in steel plants), boilers
and equipment not covered under ISO 12100.
The requirements of protective system are specified in ISO 13577-4.
If a general provision of ISO 13577-1 counters provisions in this part of ISO 13577, the provisions of this part
of ISO 13577 takes precedence.
It is assumed that TPE will only be operated and maintained by trained personnel.

viii © ISO 2014 – All rights reserved

DRAFT INTERNATIONAL STANDARD ISO/DIS 13577-3

1 Industrial furnaces and associated processing equipment —
2 Safety — Part 3: Generation and use of protective and reactive
3 atmosphere gases
4 1 Scope
5 This part of ISO 13577 specifies safety requirements for generation and use of atmosphere gas that are part
6 of industrial thermo-processing equipment (TPE)
7 NOTE: The general safety requirements common to TPE are provided in ISO 13577-1 (See introduction).
8 This part of ISO 13577 deals with significant hazards, hazardous situations and events relevant to the
9 generation and use of protective or reactive fluids created by thermochemical reactions. and their use in TPE
10 that are part of TPE as listed in Clause 4 and 5, when used as intended and under the conditions foreseen by
11 the manufacturer.
12 This part of ISO 13577 covers:
13  Pipework downstream of and including the manual isolating valve
14  Equipment for the generation of atmosphere gases
15  Additional equipment for the use of atmosphere gases in TPE
16  Safety devices
17  Functional requirements for safety related control system
18 for the generation and use of protective or reactive fluids.
19 It applies to the supply of fluids to TPE and their removal from TPE, confined to equipment integrated in the
20 TPE.
21 This part of ISO 13577 also details the anticipated significant hazards associated with atmosphere gas
22 systems and their use in TPE and specifies the appropriate preventative measures for the reduction or
23 elimination of these hazards.
24 The pressure hazard of the piping and components covered by this standard is within the maximum
25 pressure/size relationship of group I as described in normative Annex C.
26 This part of ISO 13577 specifies the requirements to be met to ensure the safety of persons and property
27 during installation, commissioning, start up, operation, shutdown and maintenance.
28 This part of ISO 13577 does not cover the relevant risks involved in the flue gas ducting system when it is not
29 considered a part of TPE.
30 This part of ISO 13577 is not applicable to utility supply upstream of the TPE main disconnects.
31 This part of ISO 13577 does not apply to TPE for semi-conductor devices.
ISO/DIS 13577-3
32 This standard does not apply to TPE with atmosphere:
33  As air
34  As a flue gas from an over stoichiometric combustion
35 This part of ISO 13577 not covers the decommissioning of the TPE.
36 This part of ISO 13577 not covers vacuum furnaces.
37 This International Standard also gives the necessary requirements for the information for use.
38 This Part of ISO 13577 assumes that the equipment is not creating any potentially explosive atmosphere and
39 is not designed to be located in an area with a potentially explosive atmosphere. .
40 This Part of ISO 13577 assumes that the equipment is not designed to be located in an area with hazardous
41 atmosphere.
42 This standard is not applicable to generation and use of atmosphere gas in TPE and associated plant which is
43 manufactured before the date of its publication as International Standard.
44 A table of typical protective and reactive fluids is given in Annex B.
45 This part of ISO 13577 does not deal with the hazard of noise. It's covered in ISO 13577-1.
46 2 Normative References
47 The following referenced documents are indispensable for the application of this International Standard. For
48 dated references, only the edition cited applies. For undated references, the latest edition of the referenced
49 document (including any amendments) applies.
50 ISO 7-1:1994, Pipe threads where pressure-tight joints are made on the threads — Part 1: Dimensions,
51 tolerances and designation
52 ISO 49:1994, Malleable cast iron fittings threaded to ISO 7-1
53 ISO 228-1:2000, Pipe threads where pressure-tight joints are not made on the threads — Part 1: Dimensions,
54 tolerances and designation
55 ISO 5817:2003, Welding - Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding
56 excluded) - Quality levels for imperfections
57 ISO 7005-1:1992, Metallic flanges —Part 1: Steel flanges
58 ISO 7005-2:1988, Metallic flanges — Part 2: Cast iron flanges
59 ISO 7005-3:1988, Metallic flanges — Part 3: Copper alloy and composite flanges
60 ISO 8434-1:1997, Metallic tube connections for fluid power and general use — Part 1: 24° compression
61 fittings
62 ISO 8434-2:1994, Metallic tube fittings for fluid power and general use — Part 2: 37° flared fittings
63 ISO 8434-3:2005, Metallic tube connections for fluid power and general use — Part 3: O-ring face seal
64 connectors
65 ISO 12100:2010, Safety of machinery - General principles for design - Risk assessment and risk reduction
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ISO/DIS 13577-3
66 ISO 13574, Industrial furnaces and associated thermal processing equipment - Vocabulary
67 ISO 13577-1, Industrial furnaces and associated processing equipment - Safety – Part 1: General
68 requirements
69 ISO 13577-2, Industrial furnaces and associated processing equipmen – Safety – Part 2: Combustion and fuel
70 handling systems
71 ISO 13777-4, Industrial furnaces and associated processing equipment – Safety – Part 4: Protective Systems
72 ISO 13849-1:2006, Safety of machinery - Safety-related parts of control systems - Part 1: General principles
73 for design
74 ISO 19879:2005, Metallic tube connections for fluid power and general use — Test methods for hydraulic fluid
75 power connections
76 ISO 22967:2010, Forced draught gas burners
77 ISO 22968:2010, Forced draught oil burners
78 ISO 23551-1:2012, Safety and control devices for gas burners and gas-burning appliances - Particular
79 requirements - Part 1: Automatic valves
80 ISO 23551-2: 2006, Safety and control devices for gas burners and gas-burning appliances – Particular
81 requirements - Part 2: Pressure regulators
82 ISO 23551-3:2005, Safety and control devices for gas burners and gas-burning appliances – Particular
83 requirements - Part 3: Gas/air ratio controls, pneumatic type
84 SO 23551-4:2005, Safety and control devices for gas burners and gas-burning appliances – Particular
85 requirements - Part 4: Valve-proving systems for automatic shut-off valves
86 ISO 23553-1:2007, Safety and control devices for oil burners and oil-buring appliances – Particular
87 requirements – Part 1: shut off devices for oil burners
88 IEC 61511-1:2003, Functional safety - Safety instrumented systems for the process industry sector - Part 1:
89 Framework, definitions, system, hardware and software requirements
90 IEC 62061:2005, Safety of machinery - Functional safety of safety-related electrical, electronic and
91 programmable electronic control systems
92 3 Terms and definitions
93 For the purposes of this document, the terms and definitions given in ISO 13574:— and the following apply.
94 3.1
95 protective or reactive atmosphere
96 atmosphere that is used to prevent the oxidization or decarburization of a products surface, or to change
97 property of steel such as carburizing or nitriding
98 [SOURCE: ISO 13574:—, 2.137]
99 3.2
100 flame detector device
101 shutdowndevice by which the presence of a flame is detected and signalled; it can consist of a flame sensor,
102 an amplifier and a relay for signal transmission
103 [SOURCE: ISO 13574:—, 2.65]
ISO/DIS 13577-3
104 3.3
105 flame trap
106 flame arrestor
107 device fitted to the opening of an enclosure, or to the connecting pipe work of a system of enclosures, and
108 whose intended function is to allow flow but prevent the transmission of flame
109 [SOURCE: ISO 13574:—, 2.68]
110 3.4
111 automatic shut-off valve
112 valve that opens when energised and closes automatically when de-energized
113 [SOURCE: ISO 13574:—, 2.194]
114 3.5
115 safety shutdown
116 A function that takes the TPE out of operation and brings it in a defined safe state
117 NOTE The definition is different from safety shutdown according ISO 13574:--, 2.166 which is applicable to
118 ISO 13577-2.
119 3.6
120 flame failure
121 loss of flame from the normally detected position by any cause other than the action of de-energising the
122 automatic shut-off valves system
123 NOTE The term is used in ISO 13577-2.
124 3.7
125 atmosphere gas generating system (e.g. gas generator)
126 equipment that converts or modifies a fluid or a mixture of fluids (gaseous or liquid) into a gas which can be
127 utilised as the controlled atmosphere within the thermo-processing equipment
128 3.8
129 automatic re-start
130 automatic repetition of the starting up sequence without manual intervention.
131 3.9
132 endothermic generator
133 gas generator that produces atmosphere gas by an endothermic reaction
134 3.10
135 exothermic generator
136 gas generator that produces atmosphere gas by an exothermic reaction
137 3.11
138 gas, combustible atmosphere
139 any gas mixture that is capable of forming ignitable mixtures with air or oxygen under the conditions of
140 temperature and pressure used in the process, according to the lower explosion level (LEL) of the actual gas
141 mixture.
142 NOTE 1 Typically any gas mixture containing more than 5% (V/V) combustibles (H +CO+CH ) of which CH is not
2 4 4
143 more than 1% (V/V), where the remainder of the mixture is non-combustible, is considered to be combustible. Any gas
144 mixture which contains more than 1% (V/V) C H or 2,5% (V/V) NH where the remainder of the mixture is non-
n m 3
145 combustible is also considered to be combustible (see Annexes B
146 NOTE 2 A combustible gas which contains 1 % (V/V) or less oxygen cannot in itself form an explosive or combustible
147 mixture.
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ISO/DIS 13577-3
148 3.12
149 gas, inert
150 a non-combustible gas which will not support combustion and does not react at all
151 NOTE Nitrogen, helium and argon are typical inert gases. 3.15
152 3.13
153 purge gas
154 a gas which can be used to purge a TPE
155 NOTE 1 A purge gas can safely be used for pre- and post-purging of cold and hot enclosures of TPE.
156 NOTE 2 Typically purge gases are nitrogen, argon, helium and lean exothermic gas.
157 3.14
158 purge
159 forced introduction of a fluid into a pre-determined area, in order to cleanse, by displacement, the existing fluid
160 [SOURCE: ISO 13574:—, 2.141]
161 3.15
162 safety purge
163 forced introduction of a defined gas (usually Nitrogen) into the work chamber in order to provide a safe
164 atmosphere for the process
165 [SOURCE: ISO 13574:—, 2.143]
166 3.16
167 emergency safety purge
168 safety purge (3.15) conducted automatically during an upset or abnormal condition
169 [SOURCE: ISO 13574:—, 2.145]
170 3.17
171 safety purge volume
172 the volume of purge gas needed to displace either air or a combustible gas from a furnace
173 chamber/enclosure to achieve 1% (V/V) or less oxygen and/or a non-combustible atmosphere gas (as defined
174 in 3.5) and/or 25% of the lower flammability limit.
175 NOTE Typically this will be a volume equal to five times the volume of the thermo-processing equipment chamber to
176 be purged, if the purging gas is an inert gas
177 3.18
178 valve, multiturn
179 a valve which, in order to operate from the fully closed to the fully open position, requires a number of
180 revolutions of the operating key or handwheel to be completed
181 3.19
182 temperature, safe ignition (MAC)
183 the minimum temperature at which spontaneous, safe auto-ignition of combustible gases occurs
184 NOTE The safe ignition temperature has been established at 750 °C.
185 3.20
186 toxic atmosphere gas
187 a gas which, in addition to having asphyxiating properties, also acts as a poison
188 3.21
189 gas generator, internal
190 Gas generator integrated into or directly connected to a TPE
ISO/DIS 13577-3
191 3.22
192 gas control equipment
193 A centralized mounting of components such as: pipework, safety components, pressure and flow accessories,
194 assembled in a functional unit.
195 4 Safety Requirements, Measures and Verification Means
196 Protective and reactive fluids in TPE are used to react with the goods or to avoid a reaction with the goods.
197 Protective and reactive fluids are fed into the TPE at determined points and are discharged out of the TPE at
198 determined points too.
199 Protective and reactive atmosphere gases shall only be used in TPE that has been constructed to avoid
200 leakage of either combustible or toxic gases into the working environment at any point other than at vents or
201 other exits designed for the purpose.
202 Electrical circuits shall be designed in accordance with IEC 60204-1.
203 A risk assessment according to ISO 12100 shall be carried out. Safety function shall be designed in
204 accordance with ISO 13577-4., where the use of standards for functional safety IEC 62061, ISO 13849, IEC
205 61511 and IEC 61508 is included. Informative Annex E provides information for the determination of the SIL or
206 PL of safety-related functions covered in this part of ISO 13577.
207 Specific regional requirements are given in Annex G, H, and I. The safety requirements of this Annex shall
208 ensure at least the equivalent level of safety to the requirements given in this Standard.
209 CAUTION: Toxic hazards for persons occur at lower concentrations than hazards by generation of ignitable
210 atmospheres.
211 NOTE Requirement for maximum allowable concentrations values are identified by national regulations.
212 Materials used shall comply with the requirements for process fluids (e.g. non-ferrous metals are not suitable
213 for NH and natural rubber is not suitable for natural gas).
214 For basic configuration of piping system of TPE using protective or reactive atmosphere gases, see Annex F.
215 4.1 Pipework
216 4.1.1 General
217 The pipework design shall take into account the composition and properties (e. g. pressure, temperature,
218 corrosiveness, specific gravity, velocity of fluids) of the fluids and the need for venting, purging and cleaning.
219 The pipework material shall comply with the relevant standards.
220 Due to durability steel is the preferred material for pipes and components but where appropriate and the same
221 safety levels can be achieved then other materials may be utilized. Such materials and conditions of service
222 shall be specified in the instruction handbook.
223 Vibration which may cause damage to pipework, components or safety systems shall be prevented (by firm
224 anchoring and/or use of flexible couplings).
225 Pipework shall be arranged so that safe isolation of atmosphere fluids to the all gasified parts of the TPE can
226 be guaranteed
227 NOTE: Example see Figure F 1 in Annex F: Basic configuration of Piping system of TPE using protective or reactive
228 atmosphere gases.
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ISO/DIS 13577-3
229 The isolation method shall be clearly identified (e.g. by removable spool piece painted in red, blanking plate),
230 and provision for blanking opened pipes shall be provided secured against loss (e.g. by an attached chain).
231 Any time a TPE is not operating all atmosphere fluid pipework shall be safely closed and locked. Under
232 service condition it shall be disconnected.
233 Use of brass or other copper alloy components in contact with ammonia or dissociated ammonia is not
234 allowed.
235 4.1.2 Connections
236 Pipework connections shall be metallic and shall be of threaded, compression, press fittings, flanged welded
237 or brazed types. Threaded connections shall be used only for the following pressure/diameter combinations:
238  pressures up to 15 kPa, and diameters up to DN 100;
239  pressures up to 200 kPa, and diameters up to DN 50;
240  pressures up to 600 kPa, and diameters up to DN 25;
241  pressures up to 1 MPa, and diameters up to DN 15
242 For other combinations of pressures and diameters connections shall be made by means of welded flanges or
243 welded joints. The number of connections shall be kept to a minimum.
244 For fittings according to ISO 49, the following limitations shall be observed:
245  fittings must be class “A” and
246  maximum allowed pressure is 50 kPa and
247  for dimensions DN25 or less, the maximum pressure is 600 kPa
248 Where the equipment has a threaded connection, this thread shall comply with ISO 228-1 or ISO 7-1 as
249 appropriate. The use of threads complying with ISO 228-1 is limited to diameter up to DN 50. In the case of
250 threads according to ISO 228-1, the tightness shall be ensured by a ring gasket. . In case of threads according
251 ISO 7-1 suitable sealants shall be used to ensure tightness. Hemp shall not be used in threaded connections
252 unless reinforced with a suitable sealant.
253 Where press fitting according to EN 10352 are used, they shall comply with the application restrictions (e.g.
254 temperature, vibration, fluids) .
255 Other threaded connections shall only be used providing they ensure tight connections and are suitably
256 identified.
257 The design of pipework shall be such as to avoid tensile loading of the joints.
258 Compression fittings shall comply with ISO 8434-1, -2 and -3 or ISO 19879. They shall only be used for
259 pressures up to 500 kPa and diameters up to 42 mm.
260 Any pipe passing through an unventilated space shall not have a connection except welded joints.
261 Flanges shall comply with ISO 7005-1 and -2 as appropriate.
262 Arc welding shall comply with ISO 5817, quality Level C.
ISO/DIS 13577-3
263 4.1.3 Unconnected pipework
264 Any unconnected pipework shall be plugged, capped or blank flanged by means of metallic parts.
265 4.1.4 Galvanic cells
266 The formation of galvanics cell shall be avoided by suitable choice of materials.
267 4.1.5 Flexible tubing and couplings
268 Flexible tubing shall comply with the general requirements of 4.1.1, together with the following:
269  shall be as short as possible,
270  shall be suitable for the maximum and minimum working temperatures;
271  shall be suitable for a pressure 1,5 times the working operating pressure (with a minimum of 15 kPa), at
272 the maximum and minimum working temperatures,
273  shall have a directly accessible, upstream manual shut-off valve,
274  shall be mounted in such a way as to avoid distortion, whiplash and damage,
275  shall have end fittings as integral parts of the tubing
276  and shall be constructed from suitable material both metallic and/or non-metallic selected for the
277 application duty and not be easily damaged.
278 Couplings for removable equipment shall ensure a gastight connection with the equipment connected and
279 disconnected
280 4.1.6 Marking of pipework
281 The pipework shall be identified as gas/fluid pipework.
282 Marking of different fluids lines is required which enable medium and flow direction to be identified in
283 accordance with the ISO XXXX.
284 NOTE Identification of pipework is dealt with by national regulations.
285 4.1.7 Soundness/Tightness
286 The pipework shall be tight and shall be designed to withstand the internal pressure. After assembly, the gas
287 pipework shall be submitted to its test pressure and tested for tightness. The test pressure shall be not less
288 than 1.1 times the maximum working pressure at any point with a minimum of 5 kPa.
289 The external leakage rate shall not give rise to a dangerous condition, combustible and/or toxic, in the
290 foreseen circumstances of the equipment installation. The frequency of testing to determine the external
291 leakage shall be specified in the instruction handbook.
292 NOTE It is generally agreed that an external leak rate of ~1dm3(n)/h gas or 1cm3(n)/h for methanol will not create a
293 dangerous condition in typical ventilated industrial installation. The external leak rate test method shall take into account
294 the volume, number of connections, test gas, number of valves and component parts contained and temperature. Methods
295 of testing shall include spray bubble leak identification and/or pressure decay test.
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ISO/DIS 13577-3
296 4.1.8 Condensate drains
297 In cases where condensates can create a hazard, means shall be provided at the lowest points of the
298 equipment for draining any condensate. When moist gases are being used, condensate drains of a suitable
299 type shall be installed. Any condensate drains, siphons, etc. shall be in a position such that they can be easily
300 checked. Combustible condensates shall be collected by an appropriate means (e. g. piped into a container).
301 Valves in condensate drains shall be suitably plugged, capped or blank flanged by metallic parts.
302 4.1.9 Purge points
303 Means shall be provided to facilitate purging of the gas system during commissioning and maintenance to
304 prevent the build-up of combustible substances.
305 All distribution pipework and storage vessels for atmosphere gas shall be designed, so that purging
306 procedures in accordance with 4.5 or in such a manner which excludes the simultaneous presence of
307 combustible gas/air mixtures and an ignition source can be done. Each purging point shall be provided with a
308 valve which shall either:
309  be fitted with a device to prevent unauthorised operation; or
310  be blanked off during normal operation of the plant.
311 4.1.10 Blow-off and breather pipes or conduits
312 Where blow-off or breather pipes or conduits are fitted on regulators or relief valves or vent valves, adequate
313 means shall be provided to facilitate the venting of gas from the system to a safe discharge area
314 In case breathers or blow-off pipes are gathered, the cross section of the collector shall be suitable to
315 evacuate simultaneously total flow rates of the exhaust sources.
316 Vents shall not be manifold.
317 4.1.11 Pressure relief devices and flame arrestors on pipework
318 For equipment designed for situations in which flash-backs can occur, flame arrestors and/or pressure relief
319 devices shall be fitted.
320 Pressure relief devices shall be designed to yield at a pressure below the design pressure of the pipework and
321 shall be positioned such that the discharge flow and the pressure relief device does not constitute a risk to the
322 equipment, personnel or third parties.
323 A flash-back shall trigger an alarm. The required measures after a flash-back shall be described in the
324 instruction handbook.
325 4.1.12 Pressure oscillations
326 The pipework shall be designed so as to avoid the possibility of gas velocities and pressure fluctuations
327 causing oscillations which could cause damage to pipework, components or safety systems (e. g. by
328 designing the correct sizing of pipe, using pressure regulator,).
329 4.1.13 Combustible fluid by-pass
330 By-passes shall not be fitted in parallel with any item of combustible fluids safety equipment
331 This requirement shall not apply t
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