Pressure Spikes: The Hidden Threat to Pressure Measurement Systems

Pressure spikes can place significant stress on pressure measurement systems, even when normal operating pressure remains well within the transmitter’s rated range. Understanding pressure transients is essential when selecting a reliable pressure transmitter for demanding industrial applications.

A pressure measurement system can appear perfectly stable during normal operation. A hydraulic system may run consistently at 200 bar, for example, with no obvious problems.

But what happens when the pressure suddenly jumps to 400 bar for a fraction of a second?

These short-duration events are known as pressure spikes or pressure transients. They can occur during pump start-up, valve operation, emergency shutdowns and sudden changes in fluid flow.

Because pressure spikes can happen in milliseconds, they may not appear on a conventional pressure gauge. However, the pressure transmitter still has to withstand the event.

For applications involving hydraulics, industrial machinery, oil and gas, pumps, compressors and pressure testing, understanding pressure spikes is an important part of pressure transmitter selection.

What Causes Pressure Spikes?

A pressure spike occurs when pressure changes rapidly over a very short period.

Unlike a gradual increase in operating pressure, a transient pressure event can produce a sudden peak that is considerably higher than the system’s normal working pressure.

Several common causes can create pressure spikes.

Water Hammer

Water hammer is one of the most common causes of pressure transients in fluid systems.

It occurs when moving fluid is forced to stop or change direction suddenly. Rapidly closing a valve, for example, can cause the moving fluid to generate a pressure wave that travels through the pipework.

The resulting pressure can be significantly higher than the normal system pressure.

Water hammer can occur in:

• Water and wastewater systems
• Hydraulic equipment
• Pumping systems
• Industrial process systems
• Long pipe runs
• Systems using fast-acting valves

The faster the change in fluid velocity, the more severe the resulting pressure transient can become.

Pump and Compressor Start-Up

Starting or stopping a pump or compressor can create rapid changes in pressure and flow.

Depending on the system design, start-up can produce an initial pressure surge before the system reaches its normal operating condition. Similar effects can occur during shutdown.

Variable-speed drives, soft-start systems and appropriate control strategies can reduce these effects, but they do not necessarily eliminate pressure transients completely.

Valve Operation

Valves can have a major influence on pressure stability.

Fast-acting valves, solenoid valves and control valves can all create rapid changes in flow. When a valve opens or closes quickly, the resulting change in fluid velocity can generate a pressure wave.

In some applications, the pressure spike happens so quickly that it is not visible on a standard pressure gauge.

Mechanical Shock

Not all pressure transients originate from fluid movement.

Mechanical shock and vibration can also affect pressure measurement systems.

Mobile hydraulics, heavy machinery, test equipment and industrial systems may subject a pressure transmitter to sudden mechanical forces through the installation or pressure connection.

This means the transmitter may need to withstand both pressure spikes and mechanical shock.

Why Normal Operating Pressure Isn’t the Whole Story

One of the most important considerations when specifying a pressure transmitter is the difference between normal operating pressure and maximum pressure exposure.

Normal operating pressure is the pressure the system experiences during typical operation.

Maximum pressure exposure includes the pressures the transmitter could realistically encounter, including short-duration transient events.

For example, a hydraulic system might normally operate between 100 and 200 bar but experience occasional pressure spikes of 350 bar.

Selecting a transmitter based only on the 200 bar operating pressure could leave insufficient protection against these transient events.

The problem is that pressure spikes are often difficult to predict.

A conventional pressure gauge may show a perfectly acceptable reading because its mechanical response is too slow to capture a very short pressure spike.

A pressure transmitter may respond much faster and therefore experience the full pressure event.

The pressure you can see is not necessarily the pressure your sensor experiences.

How Do Pressure Spikes Affect Pressure Sensors?

Repeated or excessive pressure spikes can affect a pressure transmitter in several ways.

The most immediate concern is mechanical stress. Excessive pressure can place additional force on the sensing element, diaphragm and pressure connection.

A transmitter may survive a single pressure event without immediate failure. However, repeated exposure to high transient pressures can contribute to mechanical fatigue and reduce long-term reliability.

Depending on the severity of the event, pressure spikes can potentially cause:

• Permanent measurement errors
• Zero shift
• Calibration changes
• Sensing element damage
• Diaphragm deformation
• Mechanical failure
• Reduced transmitter service life

The effect depends on several factors, including the magnitude, duration and frequency of the pressure spike.

This is why asking only, “What is the normal operating pressure?” is not enough.

Operating Pressure, Overpressure and Burst Pressure

When selecting a pressure transmitter, it is important to understand the difference between several pressure specifications.

Operating Pressure

The operating pressure range is the pressure range within which the transmitter is designed to provide its specified measurement performance.

Overpressure

Overpressure refers to pressure above the specified measurement range that can be applied without causing unacceptable damage or permanent degradation, according to the manufacturer’s specification.

This is particularly important when pressure spikes are expected.

Burst Pressure

Burst pressure represents a much higher pressure limit associated with structural failure of the pressure-containing components.

Burst pressure should not be treated as a normal operating limit.

A transmitter should never be routinely operated close to its burst pressure simply because it can technically withstand that pressure.

For applications with significant pressure transients, the transmitter’s specified overpressure capability should be considered alongside the expected peak pressure.

How Can Pressure Spikes Be Reduced?

The best solution is not always to select a pressure transmitter with an extremely high pressure range.

The complete pressure system should be considered.

Depending on the application, pressure transients may be reduced using:

• Accumulators
• Surge suppressors
• Pressure dampers
• Flow restrictors
• Appropriate valve sizing
• Controlled valve actuation
• Pump start-up controls
• Soft-start systems
• Improved pipework design

These measures can reduce the severity of pressure spikes before they reach the pressure transmitter.

However, the transmitter must still be specified for the pressure conditions it may encounter.

How to Specify a Pressure Transmitter for Pressure Spikes

When selecting a pressure transmitter for an application where pressure spikes are possible, several factors should be considered.

1. Establish the Normal Operating Range

Start by identifying the minimum, normal and maximum expected operating pressures.

This determines the basic pressure range required from the transmitter.

2. Identify Potential Transient Events

Consider what happens during:

• System start-up
• System shutdown
• Emergency stops
• Valve operation
• Pump switching
• Compressor cycling
• Pressure testing
• Changes in flow direction
• System faults

These events can expose the transmitter to pressures significantly above the normal operating range.

3. Determine the Likely Peak Pressure

Where possible, calculate or measure the maximum transient pressure.

For existing systems, high-speed pressure measurement can help identify short-duration pressure spikes that conventional gauges may miss.

4. Check the Transmitter’s Overpressure Specification

Do not select a transmitter based solely on its measurement range.

Check the manufacturer’s overpressure specification and ensure that it provides sufficient protection against the expected pressure transients.

5. Consider How Often Pressure Spikes Occur

A single pressure spike and thousands of repeated pressure spikes can have very different effects.

If transient events occur frequently, consider the cumulative mechanical stress placed on the sensing element.

6. Consider the Complete Operating Environment

Pressure is only one part of the specification.

Temperature, vibration, mechanical shock, corrosive media, installation conditions and hazardous-area requirements can all affect the appropriate transmitter design.

For demanding industrial applications, a pressure transmitter designed around the complete operating environment can provide greater reliability than one selected on pressure range alone.

Selecting the Right Pressure Transmitter

The correct pressure transmitter should be selected according to the real conditions of the application, rather than simply the pressure displayed during normal operation.

At ESI Technology, pressure transmitters are designed for demanding applications where accuracy, reliability and long-term performance are critical.

Our pressure measurement solutions cover applications across:

• Industrial and process systems
• Hydraulic equipment
• Oil and gas
• Test and calibration
• Aerospace
• Hydrogen
• Marine and subsea applications

Depending on the application, pressure transmitters can be specified with different pressure ranges, materials, electrical configurations and environmental or hazardous-area approvals.

For applications where pressure spikes or transient pressure events are a concern, it is important to understand what the transmitter may experience throughout its operating life, including pressure events that last only milliseconds.

Because when it comes to pressure measurement, the highest pressure isn’t always the one you see on the gauge.

If your application involves pressure spikes, rapid pressure changes or uncertain peak pressures, contact ESI Technology to discuss your pressure measurement requirements, or find your local distributor here