Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by and is under the jurisdiction of the National Technical Committee on Machinery Safety of Standardization Administration of China (SAC/TC 208).
Introduction
The architecture of safety standards in mechanical field is as follows:
——Class A standards (basic safety standards), specifying the basic concepts, design principles and general characteristics applicable to all machines;
——Class B standards (general safety standards), involving a kind of safety feature of machinery or a kind of widely used safety device:
Class B1, standards for specific safety features (such as safety distance, surface temperature and noise);
Class B2, standards of safety device (such as two-hand control device, interlocking device, pressure sensitive device, protective device).
——Class C standards (safety standards for mechanical products), specifying detailed safety requirements for a specific machine or a group of machines.
According to GB/T 15706, this standard belongs to Class B.
This standard is particularly relevant to the following parties concerned with mechanical safety:
——machine manufacturer;
——health and safety agency.
Other parties concerned affected by the mechanical safety level are:
——machine user;
——machine owner;
——service provider;
——consumer (for machinery intended to be used by consumers).
All the above parties concerned may participate in the drafting of this standard.
In addition, this standard is intended to be used by standardization organizations drafting Class C standards.
The requirements specified in this standard may be supplemented or modified by Class C standards.
For machines that are within the scope of Class C standards and have been designed and manufactured according to such standards, the requirements in Class C standards shall be preferred.
Local exhaust ventilation (LEV) is an important engineering control technology to maintain acceptable air quality in industrial operating environment, and the main means thereof is to control or inhibit airborne contaminants at or as close as possible to the contaminant generation point. The local exhaust ventilation is usually used together with other control methods, such as isolation, dilution ventilation or personal protective equipment. If designed, installed and operated correctly, the local exhaust ventilation (LEV) can efficiently control airborne contaminants.
This standard aims to improve the working conditions of industrial enterprises, protect personnel health and safety in the environment where harmful substances are discharged, and avoid or reduce safety accidents.
Safety of machinery - Local exhaust ventilation system - Safety requirements
1 Scope
This standard specifies the basic safety requirements for local exhaust ventilation (LEV) system.
This standard is applicable to the fixed industrial local exhaust ventilation (LEV) system for preventing or avoiding personnel from contacting airborne harmful substances in the industrial environment.
This standard is not applicable to the local exhaust ventilation (LEV) systems for the following purposes:
——comfortable ventilation;
——conveying air as a part of industrial process;
——painted cabinets not mainly for protecting personnel;
——saving energy;
——special use, special cleaning and special protection requirements.
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.
GB/T 15706-2012 Safety of machinery - General principles for design - Risk assessment and risk reduction
GB/T 33579 Safety of machinery - Control methods of hazardous energy - Lockout/tagout
GB 50016-2014 Code for fire protection design of buildings
GB 50019-2015 Design code for heating ventilation and air conditioning
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 15706-2012 and the following apply.
3.1
local exhaust ventilation (LEV) system
exhaust system
mechanical system consisting of one or more of the following components or systems to remove airborne contaminants from a space:
——exhaust hood;
——pipeline system;
——air cleaning equipment;
——exhauster or fan;
——chimney.
Note: The local exhaust ventilation system operates as a whole, and the performance of all components thereof will be affected by the design and performance of other parts.
3.2
air cleaning equipment
device or combination of devices for separating contaminants from the treated air in a local exhaust ventilation system
3.3
balanced
state when all branches in a local exhaust ventilation system simultaneously reach the expected air flowrate
3.4
baffle
flange
local enclosure arranged at or around the emission source to improve or enhance the airflow direction in the emission source and exhaust hood area
3.5
branch
connecting pipe between exhaust hood and main or secondary main
3.6
coefficient of entry
dimensionless factor used to reflect the relationship between the static pressure loss of the exhaust hood and the velocity pressure in the exhaust hood pipeline
3.7
contaminant
airborne harmful substance that can cause personal injury, danger or odor
Example: Smoke, fume, dust, steam, mist, water vapor or gas, etc.
3.8
capture velocity
control velocity
airflow velocity at a certain point in the space which is sufficient to suck contaminants and contaminated air into the hood
3.9
entry
position where a section of branch or secondary main enters another section of secondary main or main in pipeline system
Example: entry of exhaust hood into the pipeline; entry of plenum system into the pipeline.
3.10
exhaust hood
specially shaped opening designed to capture or control chemical emissions and other air contaminants
3.11
exhaust rate
air flowrate
volume flowrate of air passing through the exhaust hood
3.12
face velocity
average velocity of airflow in the exhaust hood opening plane with its direction vector perpendicular to the plane
3.13
fan
exhauster
mechanical device for providing pressure and enabling airflow to pass through local exhaust ventilation system
3.14
loss factor
dimensionless factor reflecting the relationship between static pressure loss and velocity pressure in system accessories and equipment
3.15
main
pipeline that connects two or more branches or secondary mains to the fan, exhauster or air cleaning equipment
3.16
makeup air
replacement air
external air or air with acceptable cleanliness used to fill the space of gas exhausted through cleaning by local exhaust ventilation (LEV) system
3.17
re-entrainment
return of discharged contaminants to the local exhaust ventilation system through airflow
3.18
slot velocity
average air velocity oriented perpendicular to the inner plane of the slot
3.19
system operating point
SOP
intersection of pressure curve and flow curve on pressure-flow diagram of local exhaust ventilation system
Note: SOP is usually used for fan selection.
3.20
system effect loss
fan performance loss caused by imperfect entry and outlet conditions
3.21
user
person who is directly and ultimately responsible for the design, operation and/or maintenance of the local exhaust ventilation system or a component thereof
4 Basic requirements
4.1 Users engaged in design, operation, maintenance or testing of LEV system shall be trained or experienced in relevant work to prove that they are qualified for this work.
4.2 The design and operation of LEV system shall be based on the following basic data:
——characteristics of emission sources;
——characteristics of air in workplace space;
——interaction between relevant personnel and emission sources.
4.3 Before the start of manufacturing and installation, the technical documents of LEV system shall be reviewed by professional technicians.
4.4 The LEV system performance and its exhaust rate shall be able to reduce the contaminants in the air of the workplace to the specified acceptable concentration.
4.5 The static pressure loss of the whole LEV system shall be estimated before fan selection, construction or installation.
4.6 The structural design of the whole LEV system shall be reasonable, and its manufacturing materials shall be chemically compatible. The physical compatibility shall be considered.
Note: Measures such as using refractory glass fiber for acid gas flow and galvanized steel for solvent steam stream shall be taken to meet this requirement, and the material used should be thick enough to ensure the expected service life of the system.
The LEV system shall be constructed to ensure that the chemical substances carried in the airflow are compatible with each other and compatible with the materials of exhaust hood, pipeline and fan even if such substances reach the maximum concentration.
4.7 The LEV system shall be capable of monitoring the performance. The monitoring and control functions of LEV system shall meet the requirements of 11.1, 11.2, 11.4 and 11.5 in GB 50019-2015.
Where feasible, the performance monitoring system or equipment may include analog or digital flow meters, smoke detectors, gas detectors or other equipment or programs as required.
For the LEV system, a static pressure hole should be arranged in the pipeline connecting the exhaust hood (in front of the damper and close to the exhaust hood), because it is optimal to measure the LEV system performance by using the airflow at the exhaust hood in terms of cost and efficiency, and there is a functional relationship between the static pressure of the exhaust hood and the airflow at this position.
4.8 When necessary, redundancy design shall be adopted for the safety protection devices and protection measures in LEV system to ensure continuous personnel protection.
4.9 The LEV system shall be kept clean in its whole life cycle, and free of potential risks such as open flame, smoke and explosion, and shall be kept in good operating condition.
5 Structure and layout
5.1 General requirements
5.1.1 Structure of LEV system
If conditions permit, single LEV system shall be arranged in the way as compact as possible so that it:
a) has the minimum pipe length and the least number of elbows;
b) is convenient to correctly mix the airflow from different exhaust hoods.
Generally, separate exhaust systems shall be set for decentralized processes or infrequently operated equipment.
5.1.2 Layout of LEV system
The machinery equipped with local exhaust system and elements (such as exhaust hood) of exhaust system should be arranged in such a way that they can facilitate the arrangement of exhaust pipeline system, so as to:
a) facilitate or not hinder the operation of other equipment, such as cranes, elevators, trucks, etc. as possible;
b) allow unimpeded access to the pipeline system for inspection, cleaning and maintenance;
c) prevent external damage and protect the pipeline system to the greatest extent.
Foreword i
Introduction ii
1 Scope
2 Normative references
3 Terms and definitions
4 Basic requirements
5 Structure and layout
5.1 General requirements
5.2 Cleaning and drainage
5.3 Special requirements
5.4 Plant reconstruction
6 Makeup air system
7 Exhaust hood
8 Pipeline system and exhaust funnel/chimney
9 Air cleaning equipment
10 Fan and air conveying equipment
Annex A (Informative) Design information of exhaust hood
Bibliography
Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by and is under the jurisdiction of the National Technical Committee on Machinery Safety of Standardization Administration of China (SAC/TC 208).
Introduction
The architecture of safety standards in mechanical field is as follows:
——Class A standards (basic safety standards), specifying the basic concepts, design principles and general characteristics applicable to all machines;
——Class B standards (general safety standards), involving a kind of safety feature of machinery or a kind of widely used safety device:
Class B1, standards for specific safety features (such as safety distance, surface temperature and noise);
Class B2, standards of safety device (such as two-hand control device, interlocking device, pressure sensitive device, protective device).
——Class C standards (safety standards for mechanical products), specifying detailed safety requirements for a specific machine or a group of machines.
According to GB/T 15706, this standard belongs to Class B.
This standard is particularly relevant to the following parties concerned with mechanical safety:
——machine manufacturer;
——health and safety agency.
Other parties concerned affected by the mechanical safety level are:
——machine user;
——machine owner;
——service provider;
——consumer (for machinery intended to be used by consumers).
All the above parties concerned may participate in the drafting of this standard.
In addition, this standard is intended to be used by standardization organizations drafting Class C standards.
The requirements specified in this standard may be supplemented or modified by Class C standards.
For machines that are within the scope of Class C standards and have been designed and manufactured according to such standards, the requirements in Class C standards shall be preferred.
Local exhaust ventilation (LEV) is an important engineering control technology to maintain acceptable air quality in industrial operating environment, and the main means thereof is to control or inhibit airborne contaminants at or as close as possible to the contaminant generation point. The local exhaust ventilation is usually used together with other control methods, such as isolation, dilution ventilation or personal protective equipment. If designed, installed and operated correctly, the local exhaust ventilation (LEV) can efficiently control airborne contaminants.
This standard aims to improve the working conditions of industrial enterprises, protect personnel health and safety in the environment where harmful substances are discharged, and avoid or reduce safety accidents.
Safety of machinery - Local exhaust ventilation system - Safety requirements
1 Scope
This standard specifies the basic safety requirements for local exhaust ventilation (LEV) system.
This standard is applicable to the fixed industrial local exhaust ventilation (LEV) system for preventing or avoiding personnel from contacting airborne harmful substances in the industrial environment.
This standard is not applicable to the local exhaust ventilation (LEV) systems for the following purposes:
——comfortable ventilation;
——conveying air as a part of industrial process;
——painted cabinets not mainly for protecting personnel;
——saving energy;
——special use, special cleaning and special protection requirements.
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.
GB/T 15706-2012 Safety of machinery - General principles for design - Risk assessment and risk reduction
GB/T 33579 Safety of machinery - Control methods of hazardous energy - Lockout/tagout
GB 50016-2014 Code for fire protection design of buildings
GB 50019-2015 Design code for heating ventilation and air conditioning
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 15706-2012 and the following apply.
3.1
local exhaust ventilation (LEV) system
exhaust system
mechanical system consisting of one or more of the following components or systems to remove airborne contaminants from a space:
——exhaust hood;
——pipeline system;
——air cleaning equipment;
——exhauster or fan;
——chimney.
Note: The local exhaust ventilation system operates as a whole, and the performance of all components thereof will be affected by the design and performance of other parts.
3.2
air cleaning equipment
device or combination of devices for separating contaminants from the treated air in a local exhaust ventilation system
3.3
balanced
state when all branches in a local exhaust ventilation system simultaneously reach the expected air flowrate
3.4
baffle
flange
local enclosure arranged at or around the emission source to improve or enhance the airflow direction in the emission source and exhaust hood area
3.5
branch
connecting pipe between exhaust hood and main or secondary main
3.6
coefficient of entry
dimensionless factor used to reflect the relationship between the static pressure loss of the exhaust hood and the velocity pressure in the exhaust hood pipeline
3.7
contaminant
airborne harmful substance that can cause personal injury, danger or odor
Example: Smoke, fume, dust, steam, mist, water vapor or gas, etc.
3.8
capture velocity
control velocity
airflow velocity at a certain point in the space which is sufficient to suck contaminants and contaminated air into the hood
3.9
entry
position where a section of branch or secondary main enters another section of secondary main or main in pipeline system
Example: entry of exhaust hood into the pipeline; entry of plenum system into the pipeline.
3.10
exhaust hood
specially shaped opening designed to capture or control chemical emissions and other air contaminants
3.11
exhaust rate
air flowrate
volume flowrate of air passing through the exhaust hood
3.12
face velocity
average velocity of airflow in the exhaust hood opening plane with its direction vector perpendicular to the plane
3.13
fan
exhauster
mechanical device for providing pressure and enabling airflow to pass through local exhaust ventilation system
3.14
loss factor
dimensionless factor reflecting the relationship between static pressure loss and velocity pressure in system accessories and equipment
3.15
main
pipeline that connects two or more branches or secondary mains to the fan, exhauster or air cleaning equipment
3.16
makeup air
replacement air
external air or air with acceptable cleanliness used to fill the space of gas exhausted through cleaning by local exhaust ventilation (LEV) system
3.17
re-entrainment
return of discharged contaminants to the local exhaust ventilation system through airflow
3.18
slot velocity
average air velocity oriented perpendicular to the inner plane of the slot
3.19
system operating point
SOP
intersection of pressure curve and flow curve on pressure-flow diagram of local exhaust ventilation system
Note: SOP is usually used for fan selection.
3.20
system effect loss
fan performance loss caused by imperfect entry and outlet conditions
3.21
user
person who is directly and ultimately responsible for the design, operation and/or maintenance of the local exhaust ventilation system or a component thereof
4 Basic requirements
4.1 Users engaged in design, operation, maintenance or testing of LEV system shall be trained or experienced in relevant work to prove that they are qualified for this work.
4.2 The design and operation of LEV system shall be based on the following basic data:
——characteristics of emission sources;
——characteristics of air in workplace space;
——interaction between relevant personnel and emission sources.
4.3 Before the start of manufacturing and installation, the technical documents of LEV system shall be reviewed by professional technicians.
4.4 The LEV system performance and its exhaust rate shall be able to reduce the contaminants in the air of the workplace to the specified acceptable concentration.
4.5 The static pressure loss of the whole LEV system shall be estimated before fan selection, construction or installation.
4.6 The structural design of the whole LEV system shall be reasonable, and its manufacturing materials shall be chemically compatible. The physical compatibility shall be considered.
Note: Measures such as using refractory glass fiber for acid gas flow and galvanized steel for solvent steam stream shall be taken to meet this requirement, and the material used should be thick enough to ensure the expected service life of the system.
The LEV system shall be constructed to ensure that the chemical substances carried in the airflow are compatible with each other and compatible with the materials of exhaust hood, pipeline and fan even if such substances reach the maximum concentration.
4.7 The LEV system shall be capable of monitoring the performance. The monitoring and control functions of LEV system shall meet the requirements of 11.1, 11.2, 11.4 and 11.5 in GB 50019-2015.
Where feasible, the performance monitoring system or equipment may include analog or digital flow meters, smoke detectors, gas detectors or other equipment or programs as required.
For the LEV system, a static pressure hole should be arranged in the pipeline connecting the exhaust hood (in front of the damper and close to the exhaust hood), because it is optimal to measure the LEV system performance by using the airflow at the exhaust hood in terms of cost and efficiency, and there is a functional relationship between the static pressure of the exhaust hood and the airflow at this position.
4.8 When necessary, redundancy design shall be adopted for the safety protection devices and protection measures in LEV system to ensure continuous personnel protection.
4.9 The LEV system shall be kept clean in its whole life cycle, and free of potential risks such as open flame, smoke and explosion, and shall be kept in good operating condition.
5 Structure and layout
5.1 General requirements
5.1.1 Structure of LEV system
If conditions permit, single LEV system shall be arranged in the way as compact as possible so that it:
a) has the minimum pipe length and the least number of elbows;
b) is convenient to correctly mix the airflow from different exhaust hoods.
Generally, separate exhaust systems shall be set for decentralized processes or infrequently operated equipment.
5.1.2 Layout of LEV system
The machinery equipped with local exhaust system and elements (such as exhaust hood) of exhaust system should be arranged in such a way that they can facilitate the arrangement of exhaust pipeline system, so as to:
a) facilitate or not hinder the operation of other equipment, such as cranes, elevators, trucks, etc. as possible;
b) allow unimpeded access to the pipeline system for inspection, cleaning and maintenance;
c) prevent external damage and protect the pipeline system to the greatest extent.
Contents of GB/T 35077-2018
Foreword i
Introduction ii
1 Scope
2 Normative references
3 Terms and definitions
4 Basic requirements
5 Structure and layout
5.1 General requirements
5.2 Cleaning and drainage
5.3 Special requirements
5.4 Plant reconstruction
6 Makeup air system
7 Exhaust hood
8 Pipeline system and exhaust funnel/chimney
9 Air cleaning equipment
10 Fan and air conveying equipment
Annex A (Informative) Design information of exhaust hood
Bibliography
