Pressure relief issue in the granulation workshop

It’s probably because such materials pose a risk of dust explosion.

Polyethylene dust is classified as an explosive dust: Basis: Safety Regulations for Dust Explosions (GB15577-2007) 1 Scope This standard specifies the safety requirements for preventing explosions in areas where dust explosions are a risk. 　　This standard applies to the engineering design, production management, as well as the storage and transportation of powder products in areas at risk of dust explosions. 　　This standard does not apply to mines, areas with fireworks and firecrackers, and dust-filled environments. 　　2 Normative reference documents The provisions in the following documents become provisions of this standard through reference to it. Any referenced documents dated shall not be applicable to this standard, including all subsequent amendment sheets or revised versions that contain corrections; however, parties reaching an agreement under this standard are encouraged to consider whether the latest versions of such documents can be used. For reference documents without a date, the latest version applies to this standard. 　　GB/T11651 Rules for the Selection of Personal Protective Equipment GB12476.1 Electrical equipment for use in environments with flammable dusts – Part 1: Electrical equipment protected by enclosures and limited surface temperatures – Section 1: Technical requirements for electrical equipment IDT IEC 61241-11999 GB/T15605 Guidelines for pressure relief in dust explosions NEQ NFPA 68 GB/T17919 Guidelines for explosion-proof design of dust collectors used in areas at risk of dust explosions GB/T18154 Safety technical requirements for monitored explosion suppression systems GB50057 Code for design of lightning protection in buildings GB50058 Code for design of electrical installations in explosive and fire-hazardous environments GBJ16 Code for fire protection design of buildings 3 Terms and definitions The following terms and definitions apply to this standard. 　　3.1 Combustible dust is dust that can undergo a vigorous oxidation reaction with gaseous oxidizers, primarily air, under certain conditions. 　　3.2 Areas subject to dust explosion hazards: Places where combustible dusts and gaseous oxidizers, primarily air, are present. 　　3.3 Inerting: The technique of introducing sufficient inert material into areas at risk of dust explosions to render the dust mixture non-explosive. 　　3.4 Explosion suppression: A control technique for explosions that involves using physical and chemical methods to extinguish the flames, thereby preventing the unexploded dust from participating in further explosions. 　　3.5 Explosion arrestment: A fire control technology that involves installing devices in passages containing combustible dust to prevent flames from passing through, as well as to block and attenuate waves, thereby containing explosions within a certain range. 　　3.6 Venting of dust explosions: It is a technique for controlling explosions that occurs in an enclosure containing dust and primarily air; it involves allowing the high-temperature, high-pressure combustion products and unburned materials generated by the explosion to escape through weak points in the enclosure in a direction free from danger, thereby preventing the enclosure from being destroyed, before the explosion pressure reaches the enclosure’s maximum strength. 　　3.7 Secondary explosion: A series of explosions that occur when the shock wave from the initial explosion, during a dust explosion, lifts the accumulated dust again, forming a dust cloud which is then ignited by the flames that follow. 　　4 General Provisions 4.1 New construction, renovation, and expansion projects of enterprises in areas at risk of dust explosions shall comply with the provisions of this standard. Existing enterprises that do not meet the requirements of this standard shall formulate a plan for safety technical measures. 　　4.2 Enterprises should be aware of whether there are areas in their facilities prone to dust explosions, and take effective measures to prevent and control such explosions. 　　4.3 Enterprises shall, in accordance with this standard and taking into account the characteristics of their own dust explosion-hazardous areas, formulate their own implementation rules for dust explosion prevention as well as safety inspection checklists, and conduct thorough dust explosion prevention inspections using these checklists. Enterprises should inspect the workshops or production units at least once per quarter, and at least once per month. 　　4.4 Enterprises should earnestly carry out education on safe production and dust explosion prevention, disseminate knowledge regarding dust explosion prevention and safety regulations, so that employees are aware of the degree of danger in areas prone to dust explosions within the enterprise as well as the measures taken to prevent such explosions. Employees working in high-risk positions must receive specialized training in safety techniques and related skills, and only after passing the relevant examinations may they be allowed to take up their duties. 　　4.5 In areas at risk of dust explosions, all kinds of non-productive open flames must be eliminated. 　　4.6 Equipment and facilities for safety, ventilation and dust removal, prevention of dust explosions, and control of dust explosions shall not be replaced or taken out of use without the approval of the safety authorities. 　　5 Structure and Layout of Buildings and Structures 　5.1 Buildings and structures equipped with process equipment at risk of dust explosions or containing combustible dust should be separated from other buildings and structures, and the fire separation distance between them shall comply with the relevant provisions of GBJ16. 　　5.2 Buildings should preferably be single-story, with lightweight structures for the roofs. 　　5.3 The structural requirements for multi-story buildings are as follows: 5.3.1 Frame structures are preferred for multi-story buildings. 5.3.2 Buildings that cannot use frame structures should be equipped with blast vents in their walls that meet the required standards. 5.3.3 If windows or other openings are used as blast vents, they must be designed carefully to ensure effective blast release in the event of an explosion. 　　5.4 Process equipment with a risk of explosion should be located in outdoor areas outside the building. Process equipment in a factory building that poses a risk of dust explosion should be placed at a higher position within the building, near the exterior walls. 　　5.5 Beams, supports, walls, and equipment shall have a surface structure that facilitates cleaning. 　　5.6 Requirements for evacuation routes are as follows: 5.6.1 The working area shall have evacuation routes. The number and location of evacuation routes shall comply with the relevant provisions of GBJ16. 5.6.2 Evacuation routes shall be equipped with clear signs and emergency lighting. 　　5.7 Process equipment with explosion hazards should be installed in outdoor areas outside the building. 　　6 Preventing ignition of dust clouds and dust layers 　　6.1 Preventing spontaneous combustion of powders 　　6.1.1 Hot powders that are prone to spontaneous combustion should be cooled to normal storage temperatures before being stored. 　　6.1.2 When storing large quantities of such powders under normal storage conditions, it is necessary to continuously monitor their temperature; if an increase in temperature or the release of gases is detected, measures should be taken to cool the powder. 　　6.1.3 The unloading system should include mechanisms to prevent the accumulation of powder. 　　6.2 Preventing ignition by open flames and hot surfaces 　6.2.1 The following rules must be followed when performing operations with open flames in areas where dust explosions pose a risk: 　— Approval from a safety officer is required, along with a permit for carrying out such operations. 　— Before starting the work with open flames, all combustible dust in the area must be removed, and sufficient fire-fighting equipment must be available. 　— The area where open-flame operations are carried out should be separated from other areas. 　— No dust should enter the area where open-flame operations take place, either during the operation itself or during the cooling period afterward. 　　6.2.2 The surface temperature of equipment or devices that are in direct contact with dust, such as light sources and heating elements, should be lower than the minimum ignition temperature of the corresponding dust. 6.2.3 The transmission mechanisms of equipment and devices in areas where combustible dust is present must comply with the following requirements: – The bearings of process equipment should have dust-proof seals; if overheating is a possibility, detectors capable of continuously monitoring bearing temperature should be installed. – Belt drives should not be used; if belt drives are employed, speed difference sensors and automatic anti-skid protection devices must be installed, so that the device can ensure automatic shutdown in the event of sliding friction. 　　6.3 Prevention of arcs and electric sparks 　　6.3.1 In areas at risk of dust explosions, corresponding lightning protection measures shall be taken in accordance with the relevant provisions in GB50057. 　　6.3.2 The following regulations shall be observed when there is a risk of static electricity: 　　6.3.2.1 All metal equipment, device enclosures, metal pipes, supports, components, and parts should generally be grounded to prevent static electricity. Where direct grounding is not feasible or not permitted by the manufacturing process, indirect grounding can be achieved using conductive materials or products. 　　6.3.2.2 Containers used for holding electrostatically charged powders, as well as pipes used for transporting such powders, should be made of metal or conductive materials. 　　6.3.2.3 All connections between metal pipes, such as flanges, should be bonded together. 　　6.3.2.4 Operators should take measures to prevent static electricity. 　　6.3.2.5 Static electricity should not be eliminated by using metal conductors or screens that are directly grounded in contact with rapidly flowing powders. 　　6.3.3 Electrical equipment used in areas at risk of dust explosions shall comply with the relevant provisions in GB12476.1. 　　6.3.4 The electrical design for areas at risk of dust explosions shall be carried out in accordance with the relevant provisions in GB50058. 　　6.4 Preventing sparks from friction and collisions 　6.4.1 Measures should be taken to prevent collisions when dust clouds can be ignited by sparks generated by such collisions; explosion-proof tools should be used during maintenance work. 　6.4.2 Magnets, pneumatic separators, or screens that can remove impurities mixed in the feed material should be installed at the inlet of the process flow to prevent these impurities from colliding with the equipment. 　6.4.3 Effective measures should be taken to prevent sparks from being generated by friction between metal powders such as aluminum, magnesium, titanium, and zirconium, or powders containing these metals, and stainless steel. 　6.4.4 There are no protective measures equivalent to those used for operations involving open flames. Rotary grinding wheels and rotary cutting discs should not be used for grinding and cutting. 　　6.5 Inerting: When safety cannot be ensured even after taking the aforementioned measures in the process equipment used for producing or handling flammable powders, inerting technology should be employed. 　　6.6 Ventilation and Dust Removal 　　6.6.1 It is advisable to establish relatively independent dust removal systems for different sections of the process. 　　6.6.2 Dust collection hoods should be installed at all areas where dust is generated. 　　6.6.3 No dust should settle within the air ducts. 　　6.6.4 The installation, use, and maintenance of dust collectors shall comply with the relevant provisions of GB/T17919. 　　7 Reducing damage caused by initial explosions 　　7.1 Segmentation and isolation 　　7.1.1 The connections between process equipment should be such that the equipment can be easily separated and moved without the need for open-flame operations. 　　7.1.2 When designing process equipment, technically feasible methods of isolation should be taken into consideration. 　　7.2 Implementing protective shutdown during explosions: Several power supply control boxes that can interlock with each other should be installed depending on the size of the workshop, so that the power to all motors can be cut off promptly in emergency situations. 　　7.3 Explosion suppression 7.3.1 Explosion suppression devices should be used for protection. 7.3.2 If a monitored explosion suppression device is used, it shall comply with the requirements of GB/T18154. 　　7.4 Controlling explosion pressure: When producing and handling powders that can cause explosions, if there are no explosion suppression devices or pressure relief measures in place, all process equipment must be capable of withstanding the excess pressure generated by internal explosions. The connections between various process devices, such as pipes and flanges, must also have the same strength as the equipment itself. At the connections between high-strength and low-strength equipment, explosion suppression devices should be installed. 　　7.5 Explosion venting 7.5.1 When the strength of process equipment is not sufficient to withstand the overpressure generated by internal dust explosions under actual operating conditions, explosion vents should be provided. The size of the explosion vent should comply with GB/T15605 7.5.2. For process equipment equipped with internal pipelines, it is generally recommended that the design parameters allow it to withstand an internal overpressure of at least 0.1 MPa. 　　8 Prevention of secondary explosions 　　8.1 The joints, inspection doors, baffles, explosion vent covers, etc., of process equipment must all be tightly sealed. 　　8.2 Cleaning requirements for special locations 　　8.2.1 Effective dust removal measures shall be implemented in special locations where dust leakage cannot be completely prevented, such as at the points where powdery materials enter and leave process equipment. 　　8.2.2 Effective dust prevention measures shall be adopted in areas where powdery materials are handled manually. 　　8.2.3 Dust in areas where packaging takes place shall be cleaned regularly. 　　8.3 Cleaning 　　8.3.1 All production workshops and storage areas where dust may accumulate should be cleaned regularly. 　　8.3.2 Compressed air should not be used for cleaning. 　　8.4 Fire Extinguishing 　　8.4.1 The appropriate fire extinguishing agent should be selected based on the physicochemical properties of the dust. 　　8.4.2 During fire extinguishing, care must be taken to prevent the dust from being suspended in the air and forming a dust cloud. 　　8.4.3 Water should not be used to extinguish fires if contact with water by the burning material could result in the generation of explosive gases. 　　9 Personal Protection and Rescue 　　9.1 Personal Protection 　　9.1.1 Production workers shall use protective equipment in accordance with the relevant provisions of GB11651. 　　9.1.2 In areas where inert gases are used or where toxic gases may be released during the production process, respiratory protection devices that can ensure the safety of workers must be provided. 　　9.1.3 Workers should not wear clothing made of synthetic fibers closely against their skin in the workplace. 　　9.2 Rescue 　　9.2.1 Enterprises shall prepare emergency rescue plans for dust explosions and file them with the relevant authorities. 　　 9.2.2 All employees should be organized to conduct drills on fire fighting and emergency rescue procedures.

In the granulation workshop, the product is in granular form with a diameter of about 2 mm; is it still necessary to have explosion protection in this workshop?