As the final safety barrier for pressure vessels, the safety valve of sterilizers plays a crucial role in fields such as medical sterilization and laboratory equipment. This article systematically introduces the working principle, technical characteristics, and management specifications of the safety valve to help users ensure the safe operation of equipment.
- Core Functions and Importance of the Safety Valve
The safety valve of a sterilizer is an automatic pressure relief device, mainly undertaking three key functions: First, when the internal pressure of the sterilizer exceeds the set threshold (usually 0.14-0.16MPa), it can automatically open to release pressure; second, in emergency situations such as the failure of the temperature control system, it can prevent the pressure vessel from exploding due to overpressure; third, as a mandatory safety component of special equipment, its compliance is directly related to the legal use of the entire sterilization system.
According to the requirements of TSG 21-2016 Safety Technical Supervision Regulations for Stationary Pressure Vessels, all sterilizers with a working pressure ≥ 0.1MPa must be equipped with safety valves that meet standards. In medical institutions, safety valves are even regarded as key safety equipment, and their performance status directly affects medical safety.
- Detailed Explanation of the Working Principle of the Safety Valve
Taking the most common spring-loaded safety valve as an example, its working process can be divided into four stages:
- Seal Maintenance Stage: When the pressure inside the sterilizer is normal, the pre-tightening force of the spring keeps the valve disc and valve seat in close contact, forming a reliable seal. At this time, the safety valve is in a closed state to ensure the normal progress of the sterilization process.
- Critical Opening Stage: As the pressure rises to approximately 90% of the set pressure, the valve disc begins to lift slightly, and a slight airflow sound will appear, indicating that the system pressure is close to the critical value.
- Discharge Stage: When the pressure reaches 110% of the set pressure, the valve opens, and high-temperature steam is quickly discharged through the pressure relief port. The discharge capacity at this stage must be ≥ the maximum evaporation capacity of the sterilizer to effectively reduce the pressure.
- Reset and Closure Stage: When the pressure drops to the reseating pressure (generally 85% of the set pressure), the spring force regains the advantage, pushing the valve disc to reset, and the system returns to a sealed state.
The entire working process realizes automatic control relying on the mechanical balance between pressure and the spring, without the need for external energy. This is precisely where the reliability of the safety valve as the “last line of defense” lies.
III. Key Performance Parameters of the Safety Valve
A qualified safety valve must meet a number of strict technical indicators:
- Opening Pressure Accuracy: The error range should be controlled within ±0.005MPa. It is recommended that safety valves used in medical institutions be calibrated every six months.
- Sealing Performance: Under 90% of the set pressure, no visible leakage should be detected by the bubble method.
- Discharge Capacity: The steam discharge capacity in the fully open state must be more than 1.1 times the maximum gas production of the sterilizer.
- Reseating Pressure Difference: The pressure difference between opening and closing should be ≤ 10% of the set pressure to avoid frequent jitter.
For important places such as medical sterilizers, it is recommended to select all-stainless steel valve bodies with a wrench test function and ensure that the products have passed the ISO 4126 international certification. At the same time, it should be noted that it is strictly forbidden to adjust the spring pre-tightening force without authorization or replace the dedicated safety valve with an ordinary valve.
- Maintenance and Management of the Safety Valve
To ensure that the safety valve is always in good condition, a systematic maintenance system needs to be established:
- Daily Inspection: Manually pull the test rod every week to check the flexibility of moving parts; check whether the pressure relief pipeline is unobstructed every month; observe whether the valve body has signs of rust or leakage before each sterilization.
- Regular Calibration: Calibration should be carried out at least once a year in ordinary places, and it is recommended to do so every six months in medical institutions. For calibration, a class 0.4 precision pressure gauge and a dedicated calibration bench should be used, and complete calibration records should be kept.
- Fault Handling: If air leakage is found, the sealing surface should be ground or the valve disc should be replaced; if the valve fails to open, check whether the spring is rusted and stuck; if frequent jitter occurs, check the resistance of the exhaust pipeline.
Special Reminder: The normal service life of a safety valve is generally 5 years, and it must be compulsorily replaced when it expires. For key medical sterilization equipment, adopting a dual-safety-valve redundancy design is an effective solution to improve safety.
Although the safety valve of a sterilizer is a small component, it is related to major safety issues. Users must fully recognize its importance, establish a sound management system, and ensure that this “safety guard” is always in a state of readiness. Only by organically combining standardized operation, regular maintenance, and strict supervision can the safe operation of the sterilization system be truly ensured, providing protection for medical quality and laboratory safety.