Rubber and Plastic Extruders and Extrusion Lines - Part 1: Safety Requirements for Extruders
1Key Takeaways
This standard specifies the safety requirements for extruders and extrusion production lines, focusing on the design, construction, and operation of extruders. It covers essential safety measures to ensure the protection of personnel and equipment during the extrusion process. The standard outlines general safety princ…
2Expert Interpretation
An in-depth interpretation of GB/T 25431.1-2025, the national standard for safety requirements for rubber and plastic extruders, covers key technical requirements such as mechanical hazard protection, electrical safety, and thermal hazard control, providing professional guidance on safety design and risk assessment.
Standard Revision Background and Technological Innovation
GB/T 25431.1-2025, a Category C standard for safety requirements for rubber and plastic extruders, is a comprehensive upgrade of the 2010 version. This revision fully considers the evolution of extruder technology and safety protection needs over the past 15 years. The scope of application has been expanded from plastic extruders to include rubber and plastic screw extruders, demonstrating the standard's adaptability to industry developments.
The core changes in the standard revision are reflected in the restructuring of the terminology system, the refinement of safety requirements, and the improvement of verification methods. Of particular note is the upgrade of control system safety requirements, shifting from the traditional "category" concept to the "required performance level PL," marking a move toward more refined and quantitative safety control technology.
Comparative Analysis of Major Technological Changes
| Technical Field | Requirements of the 2010 Edition | Requirements of the 2025 Edition | Significance of Technological Upgrade |
|---|---|---|---|
| Scope of Application | Plastic Extruders | Rubber and Plastic Screw Extruders | Expand the applicability of the standard to cover a wider range of industry needs |
| Control System Safety | Category-Based | Based on Performance Level PL | Aligned with international standards to provide more accurate safety assessment |
| Protective Device Requirements | Complies with GB/T15706 | Complies with GB/T8196 | Citing more professional protective device standards |
| Thermal hazard control | Hot machine parts and thermoplasticized materials | Unified as thermal hazards | Integrate heat-related risks and provide systematic protection |
| New requirements | None | Ergonomic requirements | Focus on operator health and improve work comfort |
Key technical requirements for mechanical hazard protection
Protection of drive and transmission devices
Standard 4.2.1 clearly stipulates that the drive shaft, connector and transmission belt between the motor and the reducer must be protected by a fixed protective device that complies with the provisions of GB/T8196. The safety distance must comply with the provisions of Table 2, Table 3 and/or Table 4 of GB/T23821-2022, which ensures that operators will not accidentally contact rotating parts during normal maintenance and operation.
Screw shaft end protection
According to the requirements of 4.2.2, if the end of the screw shaft does not have an enclosed housing, a fixed protective device is also required. This requirement is specifically designed for the transmission end of single-screw and twin-screw extruders to prevent clothing, tools or body parts from being caught in rotating parts.
Feeding system safety design
The standard puts forward differentiated safety requirements for different types of feeding systems:
| Feeding system type | Main protection requirements | Control system safety level | Emergency stop requirements |
|---|---|---|---|
| Hopper | Prevent entry to hazardous areas by design, doors or covers must be equipped with interlocking devices | PLr=c | System integration |
| Single roller feeding system | Entrance area protection, stops the screw and feed roller movement when opened | PLr=c | Independent emergency stop device |
| Twin roll feeding system | Entrance area protection, stops feed roll movement when opened | PLr=c | Independent emergency stop device |
| Stop feeding system | Hazardous area protected by design or protective devices | PLr=c | System integration |
Overpressure protection system design
4.2.5 of the standard specifies the overpressure protection requirements for extruders and pressure-containing components in detail. The manufacturer must prevent the declared maximum allowable internal pressure from being exceeded by one or more of the following measures:
- Safety break point: Automatically breaks at a preset pressure
- Bursting disc: One-time overpressure protection device
- Stretchable bolt: Mechanical overpressure protection
- Pressure detection system (PLr=c): Automatically shuts off the pressure source
- Position detection system (PLr=c): Monitors the screw displacement
It is particularly important to note that possible projections of components or materials used for overpressure protection must be safely guided or deflected, such as pointing them downward or using guide plates, which reflects the standard's full consideration of secondary injuries.
Electrical Safety and Electromagnetic Compatibility
Chapter 4.3 of the standard comprehensively upgrades electrical safety requirements, expanding "electrical hazards" to "electrical hazards and electromagnetic interference hazards." Key technical requirements include:
Protection Level Requirements
Connectors and junction boxes in heating areas must meet the IP3X protection level specified in GB/T4208-2017. This ensures the safe operation of electrical equipment in humid and dusty industrial environments.
Electromagnetic Compatibility
The machine's electrical circuits must have sufficient immunity to electromagnetic interference, and electromagnetic emission limits must comply with the requirements of GB17799.4. This requirement is crucial for ensuring stable operation in complex industrial environments.
Electrostatic Protection
Areas of the machine where undesirable static electricity is foreseeable must be equipped with anti-static equipment. Specific measures should be implemented in accordance with GB12158.
Thermal Hazard Control Systems
Section 4.4 of the standard integrates heat-related risks into unified thermal hazard control requirements:
Protection of Hot Machine Components
Hot machine components that cannot be covered due to operational or process reasons (such as the extruder head) must be protected from accidental contact by insulating materials or blocking devices. The temperature of accessible surfaces must not exceed the limits specified in GB/T 18153, and warning signs must be placed nearby.
Protection of Hot Extrudates
To warn of the dangers of hot extrudates, hot gases, and hot liquids, warning signs must be placed on or near uncovered openings, and the instructions for use must provide specific recommendations for wearing personal protective equipment.
Noise Control Technical Requirements
Section 4.5 of the standard and normative Appendix B specify detailed noise control requirements:
Identification of Major Noise Sources
The standard clearly identifies major noise sources requiring particular attention, including motor drives, powertrain systems, pneumatic systems, and pressure relief/exhaust systems.
Noise Reduction Measures
Noise can be reduced through various measures, including soundproofing enclosures, mufflers, low-noise pumps, dampers, and anti-vibration installations. Noise testing must comply with the requirements of Appendix B, using either the engineering method (Level 2 accuracy) or the simplified method (Level 3 accuracy).
Noise Information Statement
When the A-weighted emission sound pressure level measured at the work position exceeds 70dB(A), the value must be declared. When it exceeds 80dB(A), the A-weighted sound power level must also be declared.
Ergonomics and High-Level Work Platform Safety
The new section 4.9 of the standard sets out ergonomic requirements for the first time:
Work Area Design
The design of the work area must comply with the requirements of GB/T16251, taking into account the operator's comfort, fatigue, and physical and psychological stress.
High-Level Work Platform Protection
Guardrails must be installed when the fall height exceeds 1m. The design of designated entry and working positions on the machine must comply with the requirements of GB/T15706-2012 and GB/T17888.
Emergency Stop System Design Requirements
Section 4.10 of the standard specifies the design principles for the emergency stop function:
- Must comply with the provisions of Category 0 Stop or Category 1 Stop in GB/T 16754-2021
- At least one emergency stop device must be installed on the control panel, and additional locations as needed based on risk assessment
- All hazardous movements must cease after an emergency stop is executed
- Circulation of non-hazardous systems such as lubrication and cooling systems shall not be forced to stop
Conformity Verification and Usage Information
Verification Methods
Chapter 5 and Table 1 of the standard detail the verification methods for safety requirements, including visual inspection, functional testing, and measurement and calculation. Different verification combinations are used for different safety requirements to ensure comprehensiveness and effectiveness of the verification.
User Information Requirements
Chapter 6 specifies detailed user information requirements, including machine markings, safety signs, and the content of the instruction manual. Particular emphasis is placed on warnings and protective guidance for specific risks, such as thermal hazards, noise hazards, and fire hazards.
Implementation Recommendations and Risk Assessment
Design Phase Considerations
During the extruder design phase, manufacturers should fully consider all major hazards listed in Appendix A of the standard, including mechanical hazards, electrical hazards, thermal hazards, and noise hazards, and determine appropriate protective measures through risk assessment.
Protection Measures Selection Principles
The standard adopts a hierarchical principle for selecting protection measures, prioritizing the elimination of hazards through design, followed by the implementation of protective devices, and finally, the use of information to warn of residual risks.
Lifecycle Safety Management
The standard requires consideration of the safety of the extruder throughout its entire lifecycle, including transportation, installation, commissioning, operation, maintenance, and decommissioning, embodying the concept of full lifecycle safety management.
Practical Application Case Analysis
Taking the double-roller feeding system as an example, the standard requires that the entrance area must be protected by designed or fixed protective devices. When the system is opened, the movement of the feed roller must be stopped by an interlock device (PLr=c). For specific debugging operations, if the feed roller needs to be rotated when the feeding system is opened, a Type II two-hand operating device must be equipped. This hierarchical protection requirement ensures safety in different operating modes.
The release and implementation of GB/T 25431.1-2025 will provide more scientific and systematic technical guidance for the safe design, manufacture and use of rubber and plastic extruders, and effectively promote the improvement of the industry's production safety level.