Diagnosing Premature Gauge Failure in a Water Treatment Pump System

Ashcroft works closely with distributors and end users to diagnose instrumentation issues in real-world operating environments and implement solutions that improve reliability and extend service life. In many cases, the root cause is not immediately visible and requires a structured evaluation of system conditions and instrument performance.

This Use Case demonstrates how an on-site assessment helped identify hidden overpressure conditions in a water treatment pump system. It also shows how applying the right diagnostic tools and protective devices eliminated premature gauge failure and improved long-term performance.

Customer / Application

A water treatment plant operating a pump system with isolation ring assemblies installed in close proximity on both the suction and discharge sides. Each assembly included a mechanical pressure gauge and pressure switch mounted on a 4-inch isolation ring.

Challenge

The plant reported that several pressure gauges were reading off zero even when no pressure was present in the line. The instruments had only been in service for approximately three years, significantly shorter than expected.

Because the assemblies were installed near pump systems, multiple potential causes had to be considered, including pulsation, vibration, temperature effects, clogging and pressure-related events. 

Engineering Assessment

Ashcroft and the distributor conducted an on-site audit to observe the instruments in both operating and idle conditions. The team systematically evaluated potential causes and found:

• No visible pointer flutter, indicating pulsation and vibration were not significant factors

• Gauges were equipped with PLUS!™ Performance movement technology, which adds dampening to help maintain a steady pointer under fluctuating conditions 

• Pressure snubbers were installed to restrict flow and provide additional dampening, protecting both the pressure gauge and pressure switch when positioned properly

• No excessive vibration detected in the system

• Ambient temperature conditions reported by operators ruled out thermal effects

• Isolation ring design reduced the likelihood of clogging

With these factors eliminated, attention turned to pressure spikes, which are more difficult to detect because they do not produce visible symptoms like pointer flutter. These surges of pressure can occur during pump start-up or shutdown and are often associated with water hammer.

To validate this theory, a max pointer, also known as a drag pointer or tell-tale, was installed. This device captures the highest pressure reached by the gauge by allowing the indicating pointer to move a secondary pointer to the peak value.

Mechanical pressure gauges are typically designed to withstand a maximum of 130 to 150 (with an internal overload stop) percent of full scale. For example, a 0–60 psi gauge should not experience pressures above approximately 78 psi. The max pointer indicated pressure excursions well beyond the gauge’s full-scale range.

While the exact peak pressure could not be determined, the readings clearly confirmed that the instruments were exposed to overpressure conditions.

Solution

To address the issue, we recommended the plant implement two key changes:

1. Pressure spike validation and instrument review

The original assemblies were removed using the Safety Quick Release™ (SQR™) feature of our isolation ring. This allowed safe removal without draining the system or disassembling piping, minimizing downtime and eliminating the need for extensive cleaning prior to evaluation. A replacement instrument was installed to maintain operation while the original assemblies were sent back to Ashcroft for further analysis.

2. Overpressure protection with a pressure limiting valve (PLV)

A pressure limiting valve was installed upstream of the replacement instrumentation. The PLV remains open during normal operation and automatically closes when pressure exceeds a defined threshold, then reopens once conditions return to safe pressure levels. This provides direct protection against transient pressure spikes commonly seen in pump systems.

Laboratory inspection of the returned gauges confirmed overpressure exposure, based on deformation of the bourdon tube and wear patterns on internal gear components.

Result

With the pressure limiting valve in place, the plant successfully eliminated premature gauge failures caused by pressure spikes. The solution provided:

• Improved instrument reliability

• Protection against transient overpressure events

• Reduced maintenance and replacement frequency

• Continued safe and efficient operation of the pump system

All future replacements were specified with pressure limiting valves as a standard component of the assembly.

Key Takeaways

In pump systems, pressure spikes can cause significant instrument damage without obvious warning signs. While pulsation and vibration are easier to detect, transient overpressure events require targeted diagnostic tools such as max pointers.

Max pointers typically will not operate in liquid filled cases which is why PLUS!™ Performance  is our recommended dampening selection.

Installing isolation rings with safety quick release mechanisms allows the flexibility to maintain installations without expensive disassembly and cleaning processes.

Combining proper diagnostics with protective devices like pressure limiting valves ensures long-term reliability and helps prevent repeated instrument failure.

Learn more

Contact us if you have questions about your application. In the meantime, check out the related resources below or download our guide to recognize the early warning signs of pressure instrument failure.