Key Takeaway
Pressure switch failure can happen for several reasons. One common cause is dirt or debris clogging the pressure port, which stops the switch from sensing pressure correctly. Over time, electrical contacts inside the switch can burn, rust, or wear out, leading to poor connection. Water or moisture getting inside the switch can also cause corrosion. Mechanical parts like springs or diaphragms may weaken due to age or repeated use, causing incorrect cut-in or cut-out points. Vibration, high temperatures, or excessive pressure spikes can also damage the switch. Sometimes, improper installation or wrong pressure settings lead to early failure. If the system turns ON and OFF too often (called short-cycling), it puts more stress on the switch. Regular inspection, keeping the switch clean, and setting the correct pressure range can help extend its life. If your system behaves abnormally, always check the pressure switch as part of your troubleshooting.
Overpressure Conditions and Shock Loading
Overpressure occurs when the system exceeds the pressure switch’s rated limit. This can lead to diaphragm rupture, contact damage, or complete switch failure. Shock loading, caused by sudden pressure spikes, is especially harmful in high-speed systems like pumps or compressors. Repeated exposure to overpressure shortens switch life and compromises reliability. To prevent this, use pressure relief valves, surge dampeners, or choose switches with higher proof/burst pressure ratings. Always check the system’s maximum expected pressure before selecting a switch. Overpressure not only damages the switch but also risks injury and equipment failure. Proper system design and protection devices help absorb shocks and extend the switch’s operational lifespan.
Mechanical Fatigue of Springs and Diaphragms
A pressure switch is like a muscle. It flexes every time the system reaches the setpoint.
That constant flexing? It causes wear.
Springs and diaphragms inside the switch are mechanical parts. Over time, they suffer from fatigue. Think of a spring being compressed and released a million times. It won’t snap, but it loses its strength. The result? Inaccurate switching, delayed action, or no switching at all.
In diaphragm-based switches, fatigue leads to tiny cracks. Sometimes they’re invisible to the eye. But they ruin the pressure integrity. Air or fluid seeps through. Switch behaves erratically.
Now, how fast this happens depends on two things: cycle frequency and pressure range.
A pressure switch operating 100 times a day will age faster than one used weekly. And if the switch is frequently pushed near its upper limit, the diaphragm gets stressed harder.
Also, temperature matters. In high-temperature environments, materials expand and contract faster. That accelerates fatigue.
Electrical Arcing and Contact Burnout
Let’s switch gears. Mechanical problems aside, electrical failures are just as deadly.
Inside a pressure switch, there’s a simple but critical job: close or open a contact when pressure hits a point. But with every open-close action, there’s an arc. A spark jumps across the contacts.
Now, multiply that by thousands of cycles. That tiny arc? It starts eroding the contact surface.
Eventually, you get pitting. Burn marks. Carbon deposits. And what was once a smooth connection turns into an unreliable spark gap.
Worse, in high-voltage or inductive loads (like motors or solenoids), the arc is stronger. One common mistake? Using a low-duty switch on a heavy-duty load. The contacts burn out fast.
There are ways to delay this:
Use snubber circuits to absorb the arc.
Match the electrical load rating.
Choose gold-plated contacts for low-voltage, or silver alloy for inductive loads.
Signs of contact burnout? Random switching, erratic behavior, or the system not responding even though pressure is correct.
So if a pressure switch stops switching, don’t just check the diaphragm. Open it. Look at the contacts. You’ll often find the real story there.
Corrosion Due to Fluid Ingress or Moisture
Moisture is sneaky. You don’t always see it. But once it enters the switch enclosure, it slowly starts eating away the internals.
Pressure switches are designed for specific environments. But in the real world, installations don’t always follow the book.
A tiny gap in the cable gland? Rainwater or humidity gets in. In food factories or washdown areas, water jets enter if the IP rating is ignored.
Once moisture touches the metal parts—especially contacts or springs—corrosion begins. You might not notice it at first. But inside, oxidation is degrading performance.
For diaphragm switches exposed to process media (like acids, coolants, or brine), the sealing must be spot-on. If the diaphragm fails, fluid enters. And corrosion is just a matter of time.
To avoid this:
Always check the IP rating.
Use proper enclosures in wet or dusty areas.
Never reuse damaged sealing gaskets.
If the switch faces aggressive chemicals, choose Teflon-coated or stainless steel diaphragms.
A corroded pressure switch may still respond. But slowly. Or inconsistently. By the time you realize, your process may have already been affected.
Improper Installation or Adjustment
Here’s where most new engineers make mistakes.
Installing a pressure switch isn’t just screwing it in. You need proper orientation, torque, and calibration.
First mistake? Overtightening. Many pressure switches have brass threads. Use a wrench too hard, and you’ll deform the fitting. Worse, it leaks later. That leakage can mislead pressure readings or flood internals.
Second mistake? Wrong mounting location. If you install it near bends, valves, or pulsing zones, the reading gets unstable.
And don’t ignore vibration. In pumps or compressors, constant shaking can loosen connectors. Or wear down the threads.
Now, let’s talk about calibration.
Pressure switches come with factory-set cut-in and cut-out points. But field engineers often adjust them. If done wrongly, you’ll get false triggering.
Always use a pressure gauge when adjusting the setpoint. And never rotate the switch body without checking the diaphragm housing—you may tear the seal.
Conclusion
Most pressure switch failures aren’t due to poor manufacturing—they’re due to improper installation or neglect. Over-tightening, incorrect wiring, and mounting in high-vibration or overly moist environments can shorten the life of a switch. Always follow the manufacturer’s installation guide, including the correct orientation and torque. Use proper sealing methods to prevent leaks and corrosion. Once installed, routine maintenance is key. Inspect for corrosion, test activation points regularly, and verify wiring connections. Pay attention to system pressure cycles—frequent switching might mean you need to adjust the setpoints or change the pump setup. Also, never exceed the rated pressure range. Doing so damages internal components, often without visible signs until it’s too late. By installing correctly and maintaining regularly, you reduce the risk of emergency repairs. Smart practices help your pressure switch deliver consistent, reliable performance, prolong system lifespan, and avoid costly shutdowns or safety issues.