Table of Contents
- Ensure safety precautions:
- Prepare for the loop checking:
- Verify power and electrical connections:
- Examine the command and control system:
- Examine the MOV operation:
- Verify control loop feedback
- Test the feedback switch
- Check the torque switch
- Keep a record of the measurements:
- Completion of MOV loop checking
- MOV Loop checking template
Ensure safety precautions:
- Lockout/tagout the motorized valve and accompanying equipment to prevent accidental re-energization during loop checking.
- To prevent unintentional operation, follow your company’s LOTO protocols, which may involve locking and labeling power sources, isolating energy sources, and notifying employees.
- Wear the right safety gear, like safety glasses, gloves, and protective clothing, based on the job environment and the risks that come with it.
- Ensure that PPE is in good condition, properly fitted, and used consistently throughout the loop checking process.
- Before starting inspection, testing, or maintenance, disconnect the motorized valve’s power supply.
- Avoid working with live circuits or components unless absolutely required and only if fully trained and authorized.
- Use insulated tools when working on electrical connections and equipment.
- Be cautious of potential electrical hazards and follow electrical safety protocols.
- Prevent harm by securing loose clothing, hair and keeping a safe distance from moving parts during operation.
- Identify and manage any hazardous materials or substances related with the motorized valve system in compliance with safety rules and requirements.
- Take precautions against leaks, spills, and exposure to the valve’s fluids or gases.
- Follow the motorized valve and equipment manufacturer’s instructions and safety requirements.
- For loop checking safety warnings and limitations, refer to the valve’s operation and maintenance handbook.
- Motorized valve loop checking staff must be properly trained and capable to perform their duties safely.
Prepare for the loop checking:
- Ensure that the necessary safety precautions are in place.
- Obtain the required tools, equipment, and documents, including a multimeter, current clamp, loop calibrator, and control system-related documents.
- Configure your multimeter to measure digital output and input signals. Ensure that the probes on the multimeter are connected properly.
- Connect the current clamp meter to the motorized valve’s three-phase supply wire. Depending on the expected current demand of the motorized valve, choose a suitable current range.
Verify power and electrical connections:
- Turn on the motorized valve’s power.
- Check the MOV’s power source to confirm it is within the specified voltage range.
- Look for any loose or damaged wires in the electrical connections.
- To confirm the power source, measure the voltage across the MOV power terminals.
Examine the command and control system:
- Check that the power in the control system is turned on and working properly.
- Check that control signals from the control system to the MOV are reaching their intended destination.(command DO/AO signals)
- Measure the control signal voltage and current to the MOV with a multimeter
Examine the MOV operation:
- Initiate open and shut orders from the control system and monitor the MOV’s reaction.
- Check that the MOV opens and closes smoothly and without excessive noise or vibration.
- If the motorized valve has a control system that activates it, ensure that the control system is in an operational state, such as when it is actively opening or closing the valve. Check the reading on the clamp meter to see how much current is flowing through the motor when it is starting up and running.
Verify control loop feedback
- Check the feedback devices, such as potentiometers or position transmitters, to ensure that the MOV’s position is accurately measured.
- Compare the actual position feedback to the position desired by the control system.
- To ensure proper operation, test the MOV under various operating circumstances.
- Determine how long it takes for the MOV to react when it receives commands from the control system.
- Verify that the positioning of the MOV can be repeated with the same degree of precision.
Test the feedback switch
- Observe the movement of the feedback switch and check if it accurately reflects the position of the valve.
- Verify that the feedback switch sends the correct signal to the control system when the valve reaches the desired position (e.g., fully open or fully closed).
- Use a multimeter to check the continuity of the feedback switch.
- Set the multimeter to measure resistance (ohms) and ensure it is within an appropriate range.
- Disconnect the feedback switch from the wiring and place the multimeter probes across the switch terminals.
- Activate the valve manually or through the control system and verify that the multimeter displays continuity (low resistance) when the switch is in the appropriate position.
- Check that the limit switches or position feedback devices provide an accurate indication of the MOV’s location at the control system or control room HMI and local control station of MOV.
- Verify that the control system receives feedback regarding the MOV’s real position.
Check the torque switch
- Determine the location of the torque switch on the motorized valve assembly. The torque switch is a safety mechanism that detects excessive torque or force applied to the valve while it is in use.
- Inspect the torque switch for visible damage, such as broken or loose connections, overheating symptoms, or worn-out components.
- Check that the torque switch is correctly placed and securely fastened to the motorized valve assembly.
- Inspect the torque switch wiring connections to ensure they are secure and clear of any loose or damaged wires.
- If necessary, use the proper tools to tighten any loose connections.
- Refer to the manufacturer’s instructions for the correct process for adjusting and testing the switch with the designed torque valve if the torque switch has an adjustable torque setting.
Keep a record of the measurements:
- Keep track of all measurements, observations, and issues that arise during the loop checking procedure.
- Make a note of any changes or repairs done to the MOV or control system.
- Prepare a detailed report describing the loop checking process and the performance of the MOV. Make a note of the starting current and running current readings for future reference or keeping records.
- Check that the measured currents are within the manufacturer’s or any applicable standards’ prescribed limitations.
- Keep a record of your observations and any concerns that arise throughout the torque switch inspection and testing.
- Make a note of any changes made to the position feedback switch, torque switch, or valve assembly.
- Prepare a detailed report detailing the inspection and testing procedure, as well as the performance of the torque switch.
Completion of MOV loop checking
- Equipment and tools should be cleaned and kept safely stored.
- Verify that the workspace for checking the MOV loop has been returned to operation in a clean manner.
- Conduct a loop MOV checking, then de-isolate the apparatus and resume the system.
- Before using the MOV, make sure it is in proper functioning condition.
MOV Loop checking template
The following illustration provides a sample of the loop checking checklist for the motor operator valve.