Yo! I’m a supplier of Azbil Valve Positioners, and I often get asks from customers about how to adjust the zero and span of these things. So, I thought I’d write this blog to share some tips based on my experience dealing with these devices day in and day out. Azbil Valve Positioner
First off, let’s talk about why we even need to adjust the zero and span of an Azbil Valve Positioner. The zero point is when the input signal is at its lowest (usually 4 mA for a standard 4-20 mA signal), and the valve should be at its fully closed position. The span, on the other hand, corresponds to the input signal at its highest (20 mA), and the valve should be fully open. Getting these settings right is crucial for the valve to operate accurately and efficiently.
Before we start adjusting, make sure you’ve got the right tools. You’ll typically need a multimeter to measure the input and output signals, a small screwdriver for making adjustments, and a pen and paper to jot down any readings. Safety first, though! Always turn off the power and make sure the system is depressurized before you start working on the valve positioner.
Step 1: Initial Checks
First, take a quick look at the valve positioner itself. Check for any visible damage or loose connections. Make sure all the wires are properly attached, and there are no signs of corrosion. If you notice anything funky, it’s a good idea to fix it before you start adjusting.
Next, check the input signal. Use your multimeter to measure the current coming into the valve positioner. It should be within the range of 4-20 mA. If it’s not, there might be a problem with the control system sending the signal, and you’ll need to sort that out first.
Step 2: Adjusting the Zero
Now, let’s get to the zero adjustment. Locate the zero adjustment screw on the valve positioner. This is usually labeled "Zero" or "Z". With the input signal set to 4 mA (you can use a signal generator to set it accurately if you have one), you’ll want to adjust the zero screw until the valve is fully closed.
You can use a visual inspection to check if the valve is closed. In some cases, you might need to use a feeler gauge to measure the gap between the valve disc and the seat. As you turn the screw, you’ll notice the valve start to move. Turn it slowly and make small adjustments. It’s a bit like tuning a guitar – you need to be patient and make incremental changes until you get it just right.
Keep checking the input signal with your multimeter to make sure it stays at 4 mA. Once the valve is fully closed and the signal is stable, you’ve set the zero point.
Step 3: Adjusting the Span
After setting the zero, it’s time to work on the span. Find the span adjustment screw, usually labeled "Span" or "S". Set the input signal to 20 mA. You want the valve to open fully at this signal level.
Just like with the zero adjustment, use your screwdriver to turn the span screw slowly. As you do this, the valve will start to open. Keep an eye on the valve’s position and the input signal. You can use a position indicator on the valve or measure the valve’s travel mechanically.
The goal is to make sure the valve is fully open when the input signal reaches 20 mA. You might need to go back and forth between adjusting the span and checking the valve’s position a few times. It can take a bit of trial and error, but with patience, you’ll get it.
Step 4: Fine – Tuning and Verification
Once you think you’ve set the zero and span correctly, it’s time for some fine – tuning. Go back and forth between the zero and span adjustments, making small changes as needed. Check the valve’s position at different input signals between 4 mA and 20 mA. You can use a step – by – step approach, increasing the signal in small increments (like 2 mA at a time) and checking the valve’s position each time.
Use your multimeter to double – check the input and output signals. You want to make sure that the valve’s position corresponds accurately to the input signal across the entire 4 – 20 mA range. If you notice any discrepancies, go back and make further adjustments.
Step 5: Final Checks
After you’re satisfied with the adjustments, do a final check. Make sure all the screws are tightened properly so they don’t come loose over time. Check the connections again to make sure everything is secure.
Turn the power back on and let the system run for a little while. Monitor the valve’s operation and the input and output signals. If everything looks good, then you’ve successfully adjusted the zero and span of your Azbil Valve Positioner.
Now, I know that adjusting the zero and span can be a bit tricky, especially if you’re new to it. That’s where we come in. As a trusted supplier of Azbil Valve Positioners, we’ve got a team of experts who can help you out. Whether you need more in – depth advice on the adjustment process or you’re having trouble with a specific model, we’re here to assist.
Rosemount Temperature Transmitter If you’re in the market for a high – quality Azbil Valve Positioner or you need any support with your existing ones, don’t hesitate to reach out. We can offer you the best products at competitive prices and provide top – notch after – sales service. Contact us today to start the conversation about your valve positioner needs.
References
- Azbil Valve Positioner User Manual
- Industry best practices for valve positioner adjustment
Iges Instrument Co., Ltd.
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