The gas filled tube furnace tube has cracked

Cracking of gas filled tube furnace tubes is a serious equipment failure that may cause gas leakage, experimental failure, and even safety accidents. The following is a detailed treatment plan for furnace tube cracking, covering cause analysis, emergency response, repair methods, and preventive measures:

1. Analysis of the causes of furnace tube cracking
Material issues
Not resistant to high temperatures: The material of the furnace tube (such as quartz, ceramics, stainless steel, etc.) cannot withstand the actual working temperature, resulting in thermal stress cracking.
Poor corrosion resistance: When corrosive gases (such as chlorine and hydrogen sulfide) are introduced, the furnace tube material is not made of corrosion-resistant materials, which accelerates corrosion.
Quality defects: Manufacturing defects such as cracks, pores, or uneven thickness in the furnace tube itself.
Thermal stress effect
Excessive temperature gradient: uneven heating of the furnace tube locally (such as uneven distribution of heating elements), leading to differences in thermal expansion and causing cracks.
Rapid cooling and heating: frequent start stop or sudden temperature changes (such as cooling directly from high temperature to room temperature), causing the furnace tube to withstand thermal shock.
mechanical damage
Improper installation: The furnace tube is not aligned or excessively tightened when connected to flanges and seals, resulting in local stress concentration.
Collision or vibration: During transportation, handling, or use, the furnace tube may experience fatigue cracking due to external force impact or equipment vibration.
Abnormal gas pressure
Internal pressure too high: The pressure of the introduced gas exceeds the designed tolerance range of the furnace tube, causing explosive cracking.
Excessive negative vacuum pressure: When vacuuming, the vacuum degree is too high, and the pressure difference between the inside and outside of the furnace tube is too large, leading to deformation or rupture.

2. Emergency response measures
Immediately stop the machine
Close all gas valves, cut off the heating power, and stop the operation of the vacuum pump.
If there is flammable or toxic gas inside the furnace tube, the exhaust system should be quickly turned on to discharge the gas outdoors.
Personnel evacuation and safety isolation
Evacuate personnel from the scene, set up a warning zone, and prohibit unrelated personnel from approaching.
Wear protective equipment (such as gas masks, gloves) and check for leaks to avoid direct contact with high temperatures or corrosive substances.
Gas leakage treatment
If the leaked gas is flammable (such as hydrogen), it is strictly prohibited to start electrical equipment or open flames to prevent explosions.
Dilute the leaked gas with inert gas (such as nitrogen) to reduce the concentration to a safe range.
Record and Report
Take photos to record the location, shape, and surrounding environment of the furnace tube cracking.
Report the malfunction to the equipment management department or safety manager, and fill out the accident report form.

3. Furnace tube repair method
a. Temporary repair (applicable to emergency situations or small cracks)
High temperature adhesive bonding:
Select high-temperature and corrosion-resistant adhesives (such as silicates and epoxy resins), mix them according to the instructions, and apply them to the crack area.
Applicable scenarios: Small cracks (<1mm), non critical areas, and working temperatures below the temperature limit of the adhesive.
Disadvantage: The bonding strength is limited, and it may peel off after long-term use.
Metal fixture fixation:
For quartz or ceramic furnace tubes, metal hoops or fixtures can be used to wrap around the cracks, and stress concentration can be reduced by tightening with bolts.
Attention: High temperature resistant insulation material should be placed between the fixture and the furnace tube to avoid uneven heat conduction caused by direct metal contact.
b. Permanent repair (requires professional operation)
Welding repair:
Quartz furnace tube: using hydrogen oxygen flame or laser welding, strict control of welding temperature and time is required to avoid secondary cracking caused by thermal stress.
Metal furnace tube: using argon arc welding or plasma welding, selecting welding materials that match the furnace tube material, and annealing treatment to eliminate internal stress after welding.
Disadvantages: High welding process requirements, requiring professional equipment and technical personnel.
Furnace tube replacement:
If the cracks are severe or the repair cost is too high, it is recommended to directly replace the furnace tube with a new one.
Steps:
Dismantle the damaged furnace tube, clean the flange interface and sealing surface.
Install new furnace tubes, ensure alignment and evenly tighten flange bolts.
Perform air tightness testing and confirm no leaks before putting it back into use.

4. Preventive measures
Material selection and verification
Select corrosion-resistant and high-temperature resistant furnace tube materials (such as high-purity quartz, alumina ceramics, 316L stainless steel) based on the type of gas introduced and the operating temperature.
Require suppliers to provide material certification and temperature and pressure resistance test reports.
Temperature control optimization
Adopting a segmented heating program to avoid sudden temperature changes.
Install thermocouples in key areas of the furnace tube, such as the heating zone and flange connections, to monitor temperature distribution in real-time.
Mechanical protection design
Install protective brackets around the furnace tube to prevent collisions during transportation or use.
Optimize flange design and adopt flexible sealing structure to reduce stress caused by thermal expansion.
Regular maintenance and testing
Develop a furnace tube inspection plan and regularly use an endoscope or ultrasonic detector to inspect cracks on the inner wall of the furnace tube.
Replace aging seals, clean up carbon deposits or impurities inside the furnace, and reduce the risk of local overheating.
Operation specification training
Train operators on furnace tube installation, disassembly, and temperature control to avoid human error.
Emphasize the sequence of “vacuuming first and then venting” to prevent gas pressure from impacting the furnace tube.