GB/T 3836.29-2021 Explosive atmospheres—Part 29：Non-electrical equipment for explosive atmospheres—Constructional safety “c”, control of ignition source “b”, liquid immersion “k”
Explosive atmospheres -
Part 29: Non-electrical equipment for explosive atmospheres - Constructional safety "c", control of ignition source "b", liquid immersion "k"
1 Scope
This document specifies the requirements for the design and construction of non-electrical equipment, intended for use in explosive atmospheres, protected by the types of protection constructional safety "c", control of ignition source "b" and liquid immersion "k".
This document is applicable to Ex equipment, Ex elements, protective systems, devices, and assemblies of these products employing the types of protection constructional safety "c", control of ignition source "b" and liquid immersion "k"..
This document supplements and modifies the requirements in GB/T 3836.28-2021. Where a requirement of this document conflicts with the requirement of GB/T 3836.28-2021, the requirement of this document takes precedence.
Types of Protection "c", "k" and "b" are not applicable for Group I, EPL Ma without additional protective precautions.
The types of ignition protection described in the document can be used either on their own or in combination with each other to meet the requirements for equipment of Group I, Group II, and Group III depending on the ignition hazard assessment in GB/T 3836.28-2021.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions 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.
GB/T 3766 Hydraulic fluid power - General rules and safety requirements for systems and their components (GB/T 3766-2015, ISO 4413: 2010, MOD)
GB/T 3836.1 Explosive atmospheres - Part 1: Equipment - General requirements (GB/T 3836.1-2021, IEC 60079-0: 2017, MOD)
GB/T 3836.26 Explosive atmospheres - Part 26: Electrostatic hazards - Guidance (GB/T 3836.26-2019, IEC TS 60079-32-1: 2013, MOD)
GB/T 3836.28-2021 Explosive atmospheres - Part 28: Non-electrical equipment for explosive atmospheres - Basic method and requirements (ISO 80079-36:2016, MOD)
GB/T 4208 Degrees of protection provided by enclosure (IP code) (GB/T 4208-2017, IEC 60529: 2013, IDT)
GB/T 6391 Rolling bearings - Dynamic load ratings and rating life (GB/T 6391-2010, ISO 281:2007, IDT)
GB/T 7932 Pneumatic fluid power - General rules and safety requirements for systems and their components (GB/T 7932-2017, ISO 4414: 2010, IDT)
GB/T 10715 Belt drives - V-ribbed belts, joined V-belts and V-belts including wide section belts and hexagonal belts - Electrical conductivity of antistatic belts: Characteristics and methods of test (GB/T 10715-2021, ISO 1813:2014, MOD)
GB/T 32072 Belt drives - Electrical conductivity of antistatic synchronous belts - Characteristics and test method (GB/T 32072-2015, ISO 9563:1990, MOD)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 3836.28-2021 and GB/T 3836.1 and the following apply.
3.1
constructional safety "c"
type of ignition protection where constructional measures are applied so as to protect against the possibility of ignition from hot surfaces, sparks and adiabatic compression generated by moving parts
Note: See Annex A for application examples.
3.2
mechanical generated sparks
sparks produced by mechanical impact or friction burning particles, as well as showers of particles, produced by impact or friction between two identical or different solid materials
3.3
control of ignition source "b"
type of ignition protection where mechanical or electrical devices are used in conjunction with non-electrical equipment to manually or automatically reduce the likelihood of a potential ignition source from becoming an effective ignition source
Note: This might for example be a level sensor used to indicate loss of oil, a temperature sensor to indicate a hot bearing or a speed sensor to indicate over-speed.
3.3.1
automatic control measure
action taken without manual intervention, to reduce the likelihood of a potential ignition source from becoming an effective ignition source
3.3.2
manual control measure
action taken by a person as a result of a warning, indication, or alarm, to reduce the likelihood of a potential ignition source from becoming an effective ignition source
3.3.3
ignition prevention devices/systems
arrangement that converts signals from one or more sensors into an action, or indication, to reduce the likelihood of a potential ignition source from becoming an effective ignition source
3.3.4
safety devices
device intended for use inside or outside explosive atmospheres but required for, or contributing to, the safe functioning of equipment and protective systems with respect to the risks of explosion
3.4
liquid immersion "k"
type of protection where potential ignition sources are made ineffective or separated from the explosive atmosphere by either totally/partially immersing them in a protective liquid, or by partially immersing and continuously coating their active surfaces with a protective liquid in such a way that an explosive atmosphere which may be above the liquid, or outside the equipment enclosure, cannot be ignited
3.4.1
protective liquid
liquid which prevents the explosive atmosphere from making direct contact with potential ignition sources and thereby ensures the explosive atmosphere cannot be ignited
3.4.2
equipment with a sealed enclosure
totally enclosed equipment that limits the ingress of an external atmosphere during the expansion and contraction of the internally contained protective liquid during use in service
Note: Such equipment includes any pipework associated with it and often contains an overpressure relief device.
3.4.3
equipment with a vented enclosure
enclosed equipment that allows the ingress and egress of an external atmosphere through a breathing device or constricted opening during the expansion and contraction of the internally contained protective liquid during normal operation
Note: Such equipment includes any pipework associated with it.
3.4.4
open equipment
equipment that is immersed, or has its elements immersed, in a protective liquid that is open to the external atmosphere
Note: For example, an open top vessel with immersed moving components. Such equipment includes any pipework associated with it.
4 Determination of suitability
Before a decision is made to protect equipment or equipment assemblies, including interconnecting parts, by the measures described in this document, it shall have been subjected to the ignition hazard assessment in accordance with GB/T 3836.28-2021.
5 Requirements for equipment with protection by constructional safety "c"
5.1 General requirements
Equipment shall be designed and constructed according to the applicable safety requirements of the relevant industrial standards, and shall be capable of functioning in conformity with the operational parameters established by the manufacturer, including any mechanical and thermal stresses that they are intended to be subjected to.
This also applies to interconnecting parts of equipment including joints (e.g. cemented, soldered, or welded joints).
Note: This requirement is achieved by using applicable national standards, industry standards, etc.
5.2 Ingress protection
5.2.1 General
The degree of ingress protection (IP) as specified in GB/T 4208 provided by the outer enclosures of equipment depends upon its intended duty and the type of environment it is designed to be used in. An appropriate rated IP degree shall be determined as part of the ignition hazard assessment (see Clause 4) and, if relevant to ignition protection, the IP degree of the enclosure shall be able to meet this requirement.
Note: IP degrees according to GB/T 4208 are not intended to provide protection against the ingress of an explosive gas atmosphere.
5.2.2 Ingress protection in special cases
The following points specify the minimum IP degree for enclosures used in the explosive atmospheres.
a) In the case of equipment intended for use in explosive gas atmospheres, where entry of foreign objects can cause ignition, but entry of dust is harmless, the required degree of protection against the entry of foreign objects shall be determined in the ignition hazard assessment and shall be at least IP20.
b) In the case of equipment intended for use in explosive gas atmospheres, where the entry of dusts or liquids could cause a malfunction leading to an ignition source, the degree of protection shall be at least IP5X for dust and IPX4 for liquids.
c) In the case of equipment intended for use in explosive dust atmospheres, where ingress of dust can result in an ignition source or fire, the degree of protection shall be IP6X.
d) In the case of equipment intended for use in explosive dust atmospheres, where ingress of dust, foreign objects and liquids are not likely to cause an ignition, no specific degree of protection is necessary for the purpose of ignition protection.
Note: An enclosure is often employed for safety protection, e.g. IP2X to prevent parts of the body coming into contact with rotating parts.
5.3 Seals for moving parts
5.3.1 Un-lubricated gaskets, seals, sleeves, bellows and diaphragms
Un-lubricated gaskets, seals, sleeves, bellows and diaphragms shall not become an effective ignition source, e.g. if there is a risk of mechanically generated sparks and hot surfaces which can become an effective ignition source. Light metals shall not be used for these parts in this case (see GB/T 3836.28-2021).
Non-metallic materials shall be resistant to distortion and degradation which would reduce the effectiveness of explosion protection within the specified lifetime of operation.
5.3.2 Stuffing box seals
Stuffing box seals shall only be used when instructions are provided by the manufacturer to limit the maximum surface temperature during operation of the gland; alternatively an automatic means shall be provided.
5.3.3 Lubricated seals
Seals which normally require the presence of a lubricant which can be replenished to reduce the likelihood of hot surfaces occurring at their interface with equipment parts shall be designed to ensure the sufficient presence of lubricant or shall be protected by one of the following means:
——provision of an effective means to monitor the continued presence of the lubricant; or
——provision of a temperature detection device to warn of increasing temperatures; or
——design of the equipment to be capable of completing the 'dry run' type test, as described in Annex B, without exceeding the maximum surface temperature of the equipment and/or without suffering damage which would reduce the effectiveness of its ignition protection.
Monitoring shall be either continuous or by required appropriate inspection and examination. Where the level of lubricant cannot be easily monitored (e.g. seal containing grease), the relevant information shall be given in the instructions.
The instructions shall include details relating to the correct lubrication, monitoring and maintenance of such seals.
5.4 Equipment lubricants/coolants/fluids
Lubricants and coolants, which are required for the protection against incendive hot surfaces or mechanically generated sparks (see Clause 7) shall have an auto-ignition temperature (see GB/T 3836.11) at least 50 K above the maximum surface temperature of the equipment where the liquid is being used.
Any fluid which can be released shall not result in an effective ignition source, e.g. due to high temperature or electrostatic charging.
5.5 Vibration
Effective ignition sources, such as hot surfaces, mechanically generated sparks or loss of protection, caused by vibration (arise from the equipment itself or from the place where it is mounted) shall be avoided.
The manufacturer shall prepare any necessary installation, operation and maintenance instructions. In particular, the instructions shall specify the correct operating speed range of the equipment in order to avoid excessive vibration.
Foreword i
Introduction v
1 Scope
2 Normative references
3 Terms and definitions
4 Determination of suitability
5 Requirements for equipment with protection by constructional safety "c"
5.1 General requirements
5.2 Ingress protection
5.3 Seals for moving parts
5.4 Equipment lubricants/coolants/fluids
5.5 Vibration
5.6 Requirements for moving parts
5.7 Requirements for bearings
5.8 Requirements for power transmission systems
5.9 Requirements for clutches and variable speed couplings
5.10 Flexible couplings
5.11 Requirements for brakes and braking systems
5.12 Requirements for springs and absorbing elements
5.13 Requirements for conveyor belts
6 Requirements for equipment with protection by control of ignition source "b"
6.1 General
6.2 Determination of the control parameters
6.3 Ignition prevention system design and settings
6.4 Ignition protection of sensors and actuators
6.5 Ignition protection types
7 Requirements for equipment with protection by liquid immersion "k"
7.1 Determination of the maximum/minimum limits
7.2 Protective liquid
7.3 Equipment construction
8 Type test
8.1 Type tests for equipment with protection by constructional safety "c"
8.2 Type tests for equipment with protection by control of ignition source "b"
8.3 Type tests for equipment with protection by liquid immersion "k"
9 Documentation
9.1 Documentation for equipment with protection by constructional safety "c"
9.2 Documentation for equipment with protection by control of ignition source "b"
9.3 Documentation for equipment with protection by liquid immersion "k"
10 Marking
10.1 General
10.2 Safety device
Annex A (Informative) Approach and application: equipment with type of protection "c"
Annex B (Normative) Test requirements
Annex C (Informative) Methodology: equipment with type of protection "b"
Annex D (Informative) Approach to assign the required ignition protection type used for equipment to achieve different EPLs
Annex E (Informative) Information on functional safety concept
Bibliography
