⚠️ Disclaimer: These tasks are guidelines only. They do not include lockout/tagout (LOTO), energy isolation, or other safety requirements. Review and verify suitability for your specific equipment and application. Add all required safety procedures per your company's policies and regulatory requirements before use. You are responsible for the safe and appropriate execution of all maintenance activities.
Float-type level switches are about as simple as process instrumentation gets. A float rises and falls with liquid level. A mechanical arm or cable translates that movement into a switch contact change. No electronics. No signal conditioning. No transmitter to calibrate.
And yet they fail constantly — because nobody looks at them until they stop working.
This checklist covers both a field-ready task set for technicians executing the PM and a full reference library for managers building or auditing float switch PM programs.
For a broader look at how sensor and instrumentation PM programs fail before they ever catch a problem, start with the foundational principles behind every instrument PM
How to Use This Checklist
Record findings with specificity — not as a checkbox answer. "Float moves freely" tells you nothing six months from now. "Float moves freely, slight resistance near bottom of travel range, arm pivot shows surface rust but no binding" tells you exactly what to watch on the next PM. Every finding that deviates from normal gets a work order number in the Comments/WO# column.
Trend over time. A float that actuates at the right set point today but needed a half-turn of adjustment three PMs ago and another quarter-turn last PM is drifting. That pattern is information. A checkbox is not.
What a real finding looks like: "Housing cover gasket shows compression set, no longer sealing fully — moisture visible inside conduit box." What a checkbox answer looks like: "OK."
Field Checklist — Critical Tasks
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect float for physical damage, corrosion, or scale buildup. Verify float moves freely on its arm or cable without binding. | Every PM | MEC |
| Inspect the switch housing and conduit connections for moisture ingress, corrosion, or damage. Verify cover seals and gaskets are intact. | Every PM | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Verify switch actuates correctly at the designated set point by manually lifting or lowering the float through its travel range. Confirm output changes state as expected. | Every PM | ELE |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect the mounting hardware, pivot arm, and any linkage or cable for wear, corrosion, or mechanical damage. Verify secure attachment to tank or vessel. | Quarterly | MEC |
| Clean float, arm, and switch exterior of scale, debris, or process residue. Use a method compatible with the process fluid and float material. | Semi-Annually | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Check all electrical connections at the switch terminals for looseness, corrosion, or heat discoloration. Tighten and clean as needed. | Quarterly | ELE |
| Verify switch wiring and conduit routing are undamaged, properly supported, and free of abrasion or chafing against adjacent surfaces. | Semi-Annually | ELE |
| Confirm switch set point and deadband match current process requirements. Adjust per manufacturer procedure if actuation level has drifted. | Annually | ELE |
Reference Checklist — Full Task Library
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect float body for cracks, dents, corrosion, or scale accumulation. Verify float is not waterlogged (shaking a hollow float should produce no liquid sound). Replace a waterlogged or damaged float immediately. | Every PM | MEC |
| Inspect switch housing, conduit entry, and cable seals for moisture ingress, corrosion, or mechanical damage. Check cover gasket condition. Replace gasket if cracked, compressed flat, or missing. | Monthly | MEC |
| Inspect process wetted materials (float, arm, and fitting) for compatibility with any changes in fluid chemistry, temperature, or concentration since last PM. Flag any concerns for engineering review. | Annually | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Manually actuate the float through its full travel range. Confirm the switch changes state at the correct level set point and returns to normal upon release. Note any hesitation, sticking, or erratic actuation. | Every PM | ELE |
| Verify actual tank or vessel level matches the switch actuation point using a sight glass, tape measure, or level transmitter reference. Adjust if actuation level has drifted from the required set point. | Every PM | ELE |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect pivot arm, hinge pin, fulcrum, or cable and counterweight assembly (as applicable) for wear, corrosion, binding, or mechanical damage. Lubricate pivot points with a lubricant compatible with the process environment. | Quarterly | MEC |
| Clean float, arm, linkage, and all external switch surfaces of scale, process residue, biological growth, or debris. Use cleaning agent compatible with float material and process fluid. Rinse and dry before returning to service. | Semi-Annually | MEC |
| Verify mounting bracket, tank nozzle flange, or vessel fitting for corrosion, leaks, or loose fasteners. Retorque flange bolts or bracket hardware to spec. Inspect gasket or thread sealant condition at process connection. | Semi-Annually | MEC |
Electrical Inspection
| Task | Freq | Type |
|---|---|---|
| Check and record switch contact resistance using a multimeter across the NO and NC contacts with switch actuated. Compare to prior readings. High or rising contact resistance indicates contact wear or contamination. | Quarterly | ELE |
| Test switch output continuity in both the actuated and de-actuated states. Verify NO opens and NC closes (or vice versa per design) with correct, repeatable switching action. | Quarterly | ELE |
| Inspect wiring, conduit, and cable routing from switch to control panel for chafing, abrasion, UV damage, or loose supports. Re-route or protect any cable segment showing wear. | Semi-Annually | ELE |
| Perform insulation resistance test on switch wiring to ground using a 500V megger. Record results in MΩ. Values below 1 MΩ indicate compromised insulation and require follow-up. Trend against prior readings. | Annually | ELE |
| Verify switch set point and deadband against current process design requirements. Adjust per manufacturer procedure using a calibrated level reference or test stand. Document as-found and as-left set points. | Annually | ELE |
| Review defect history, actuation event logs (if available), and prior PM findings. Identify any recurring issues, set-point drift trends, or environmental factors contributing to accelerated wear. Adjust PM scope or frequency accordingly. | Annually | ELE |
Failure Modes This Checklist Targets
Float waterlogging. Hollow floats develop pinhole cracks — from corrosion, mechanical damage, or material fatigue — and slowly fill with process fluid. A waterlogged float stops riding the surface and starts riding the bottom. The switch actuates at the wrong level or not at all, and nothing in the control system flags it unless there is a cross-check.
Set-point drift. The mechanical relationship between float position and switch actuation shifts over time as pivot points wear, linkage loosens, or the arm geometry changes from corrosion or repair. The switch still fires — just not where the process requires it. This checklist catches drift before it becomes a process excursion.
Contact contamination and wear. Switch contacts accumulate resistance through oxidation, contamination from moisture ingress, and normal switching wear. Contact resistance that reads low today and high six months from now is telling you something. Most programs never measure it.
Moisture ingress. Float-type switches live near tanks and vessels in environments with humidity, wash-down, and condensation. Housing seals and conduit entries deteriorate. When moisture reaches the terminal block, it causes corrosion, tracking, and erratic switching — usually at the worst possible moment.
Mechanical binding. Scale accumulation, corrosion on pivot pins, and process residue buildup on the float arm create friction in the travel mechanism. The float moves sluggishly or sticks at the top or bottom of its range. Actuation becomes inconsistent long before the switch stops working entirely.
Insulation degradation. Cable insulation in wet, chemical, or UV-exposed environments degrades gradually. Reduced insulation resistance precedes intermittent faults and hard failures. A megger reading at installation and trended through each annual PM tells you where the wiring stands.
Related Checklists
Level sensing technology that covers a wider range of tank and vessel applications: Level Sensor / Switch PM Checklist
Non-contact level measurement that works where float switches can't: Ultrasonic Level Sensor PM Checklist
Continuous level measurement for high-accuracy or difficult-process applications: Radar / Micropulse Level Transmitter PM Checklist