Ever heard the term “partial stroke testing,” only to realize it’s not a medical term? Well, if that’s you, you’re in the right place.
Many industries use partial stroke testing to make sure their factories are running. But how does partial stroke testing work? Let’s take a closer look and see inside the workings of partial stroke testing.
What Is Partial Stroke Testing?
A partial stroke test is an automated method for valve testing in control systems. Examples include those used to regulate flow or pressure in industrial processes.
A partial stroke test is actionable on a valve with a mechanical linkage. This linkage sits between the actuator and the pilot-operated poppet. The purpose of this test is to verify valve operation under normal conditions.
You can check this post for more information on valve stroke testing.
How Does Partial Stroke Testing Work?
The basic principle behind partial stroke testing is simple. If there are no leaks, then when you pressurize one side of the system, it will equalize with the other side. Yet, suppose there is leakage from either direction.
Then, some fluid will leak out of the test side before equilibration occurs. This difference in volume represents the amount of leakage through the valve.
Partial stroke tests are often found on industrial emergency shutdown valves. These valves have two positions; open and closed.
To perform a partial stroke test, the operator must first move the NO position into NC mode. They do so by turning the power supply to the solenoid coil.
Once the valve is in NC mode, the operator turns back on the power supply to the coil and presses down on the stem. When the stem moves downward, the valve should close completely.
When valve testing steel valves, partial stroke testing may also refer as “pilot-operated”. That’s because the valve’s internal mechanism controls the movement of the outer stem.
Steel valves use a spring-loaded ball check valve inside the body. This mechanism opens after the stem reaches full travel.
Benefits of Partial Stroke Testing
Partial Stroke testing provides several benefits over traditional methods of measuring leakage. The test does not need to open the valve all the way, so it allows operators to measure small amounts of leakage. They can do so without shutting down their equipment.
Second, the test requires less time than conventional methods. That’s because it takes place while the valve remains in service. Test results provide more accurate information about the actual condition of the valve.
Especially compared to visual inspections alone. Finally, the test eliminates human error associated with manual measurements.
What Are Full Stroke Tests?
Full stroke tests are like partial stroke tests. Only they involve moving the entire stem instead of the end. They conduct using hydraulic jacks or pneumatic cylinders.
These devices apply to the valve stem, meaning they allow the operator to set resistance. For example, suppose the valve closes too slow. It could show problems with the sealing surfaces or packing glands.
Partial Stroke Tests Are Worth Considering
Most manufacturers recommend regular maintenance checks on your valves. Yet, many companies still rely upon visual inspection to identify potential issues. Visual inspections are inexpensive compared to other maintenance, but they aren’t as reliable.
With partial stroke testing, make sure you’re identifying any issues. That way, you’ll be keeping your systems up and running for minimal downtime!
Keep reading and see what you can find today!
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