Repair of Malfunction of The Emergency Stop Button on A Fume Hood?

Preparations before maintenance

Tool preparation: Get all the tools needed for maintenance ready, such as screwdrivers, multimeters, soldering irons, solder wires, insulating tapes, etc. A screwdriver is used to remove the casing of the emergency stop button and related components. A multimeter is used to detect parameters such as the continuity and voltage of a circuit. Soldering irons and solder wires are used for soldering circuit connection points. Insulating tape is used for insulation treatment.

Safety precautions: Before carrying out maintenance, make sure the power supply of the fume hood has been cut off to prevent electric shock accidents. At the same time, wear necessary protective equipment, such as insulating gloves, etc.

Fault diagnosis

Visual inspection

Check whether the appearance of the emergency stop button is damaged, such as the button housing being cracked or deformed. If the casing is damaged, it may affect the normal pressing and reset of the button, causing a malfunction.

Check if the button labels are clear. If the labels are blurry, it may affect the operator's judgment, but generally will not directly cause button failure. However, after repair, it can be considered to re-label.

Press test

Manually press the emergency stop button and observe whether it can be pressed and reset normally. If the button cannot be reset after being pressed, it may be that the reset spring inside the button is damaged or stuck. At this point, you can gently shake the button to see if it can reset. If not, further disassembly and inspection are required.

Check whether the touch sensation when the button is pressed is normal, and whether there is any loose or stuck feeling. An abnormal touch may indicate that there is a problem with the mechanical structure inside the button.

Circuit detection

Use a multimeter to check the circuit continuity of the emergency stop button. Set the multimeter to the resistance range and measure the resistance values of the buttons respectively when they are pressed and reset. Under normal circumstances, when the button is pressed, the resistance value should be close to zero ohms, indicating that the circuit is conducting. When resetting, the resistance value should be infinite, indicating that the circuit is disconnected. If the measurement result does not match the normal situation, it indicates that there is a problem with the circuit of the button.

Check whether the wiring of the button is loose or fallen off. Loose or fallen wiring can lead to poor circuit contact, thereby affecting the normal function of the button. You can gently pull the wiring to check if it is firm.

Maintenance method

Replace the reset spring

If it is determined that the button cannot be reset due to the damage of the reset spring, the button housing needs to be disassembled. Use a screwdriver to unscrew the screws on the casing, carefully remove the casing, and be careful not to damage the internal circuits and components.

Find the reset spring, remove it and replace it with a new one. When installing a new spring, make sure that its installation position is correct and it can function normally.

After installing the new spring, reinstall the button housing and tighten the screws. Perform the press test again to check if the button can reset normally.

Repair the mechanical structure

If the mechanical structure inside the button gets stuck, it is necessary to carefully check the cause of the jam. It might be that foreign objects have entered the interior of the button, or that mechanical parts have worn out, causing the movement to be sluggish.

If a foreign object enters, a small pair of tweezers or other tools can be used to remove it. If it is mechanical parts that are worn out, you can try to grind and repair the worn areas or replace the worn parts. After repairing or replacing the components, conduct a press test to ensure that the mechanical structure of the button can work properly.

Reconnect the wire

For problems with loose or fallen wires, use a screwdriver to loosen the terminal blocks, reinsert the loose wires tightly, or reconnect the fallen wires to the terminals.

After the wiring is properly connected, use insulating tape to insulate the wiring points to prevent leakage. Use a multimeter again to check the continuity of the circuit and ensure that the circuit connection is normal.

Replace button

If the emergency stop button still fails to function properly after the above-mentioned inspection and maintenance, it may be that the button itself is severely damaged and cannot be repaired. At this point, a new emergency stop button needs to be replaced.

Select buttons of the same model and specification as the original ones and install them in the reverse order of disassembly. After installation, conduct a comprehensive test, including a press test and circuit inspection, to ensure that the new button works properly.

Test after repair

Functional test: Reconnect the power supply of the fume hood, manually press the emergency stop button, and observe whether the related equipment of the fume hood can immediately stop running. Press the button again to reset it and check if the equipment can resume normal operation.

Long-term operation test: Let the fume hood run for a period of time under normal working conditions and observe whether the emergency stop button shows any abnormal conditions, such as misoperation or poor contact. If no problems are found during the long-term operation test, it indicates that the repair was successful.