Is your Pressure Gauge Safe for Chemical Applications?

In chemical and petrochemical processes, a pressure gauge is only safe when it is properly matched to the process media, temperature conditions, environmental exposure, and operating pressures. Selecting the wrong gauge can lead to inaccurate measurements, instrument failure, process downtime, environmental incidents, and potential safety risks for personnel.

Ashcroft has been designing pressure and temperature measurement solutions for more than 170 years and has extensive experience helping users protect instrumentation in demanding process environments.

In this article, you'll learn the key factors that determine whether a pressure gauge is safe for chemical applications, including material compatibility, temperature limitations, ingress protection, overpressure protection, and vibration resistance.

How can a pressure gauge safely handle hazardous chemical processes?

A pressure gauge can safely handle hazardous chemical processes when it is designed to resist toxic or corrosive material, environmental exposure, temperature extremes, and pressure-related stresses. These factors can significantly affect gauge performance and longevity if they are not addressed during instrument selection.

The U.S. Environmental Protection Agency (EPA) defines a toxic chemical as any substance that may be harmful to the environment or hazardous to human health if inhaled, ingested, or absorbed through the skin. In chemical and petrochemical facilities, these substances may include corrosive, reactive, oxidizing, toxic, or carcinogenic agents used to convert raw materials into finished products.

Because these materials can damage instrumentation and create safety risks if not properly contained, pressure gauges must be evaluated for five critical factors:

1. Corrosion and wetted material compatibility
2. Temperature limits
3. Ingress Protection (IP) rating
4. Overpressure and pressure spikes
5. Pulsation and vibration

How do you prevent corrosion damage in chemical pressure gauge applications?

Preventing corrosion starts with selecting wetted materials that are compatible with the process media.

Corrosion is a leading cause of pressure gauge failure in chemical and petrochemical applications. Incompatible process media can result in media leakage, instrument failure, and serious safety hazards for operators and the environment.

To prevent corrosion-related damage, you must ensure the wetted components of the pressure gauge are compatible with the process media. On a process gauge, the sensing element, such as the Bourdon tube system, the socket, and the tip all come into contact with the process and must be compatible with the chemical being measured.

Material selection should consider:

• Process media composition
• Chemical concentration
• Process temperature
• Operating conditions

Figure 1 shows the wetted components of the Ashcroft® 1279 Duragauge® Pressure Gauge, which is designed for safety and reliability in demanding applications. However, regardless of the gauge selected, material compatibility should always be verified against the specific process requirements.

Figure 1. Ashcroft® 1279 Duragauge® wetted materials

What if a compatible wetted material is not available?

If a suitable wetted material is not available, a diaphragm seal or isolator can help protect the pressure gauge from corrosion damage.

A diaphragm seal isolates the instrument from the process while still transmitting pressure accurately, helping extend instrument life in corrosive applications.

When using a diaphragm seal, the wetted components become the diaphragm and lower housing (if applicable). These materials must also be compatible with the process media.

For additional guidance on material compatibility, refer to the Ashcroft® Material Selection & Corrosion Guide. You can also download the Complete Guide to Pressure Instrument Assembly to learn more about each of the mounting options for pressure gauge assemblies.

How do temperature limits affect pressure gauge safety?

Pressure gauges must operate within their specified temperature limits to maintain accuracy, reliability, and safety. Every pressure gauge has defined process, ambient, and storage temperature limits. Operating outside these limits can damage internal components, reduce accuracy, and shorten instrument life.

For example:

• Dry gauges are typically suitable for ambient temperatures below 200 °F (93 °C).
• Process temperatures for dry gauges are generally between -20 °F (-29 °C) and 250 °F (121 °C).
• Liquid-filled gauges are generally suitable for ambient temperatures up to 150 °F (66 °C).

The chart below illustrates the ambient, process, and storage temperature limits for pressure gauges based on gauge construction.

Figure 2. Ashcroft® 1279 Duragauge® Temperature Limits

What can you do when process temperatures exceed gauge limits?

Several options can help protect pressure gauges from excessive temperatures and maintain instrument integrity.

Use a temperature dissipator

Temperature dissipators reduce the amount of heat transferred from the process to the instrument. Examples include:

• MicroTube™ siphons for process temperatures up to 800 °F (427 °C)
• Finned siphons for process temperatures up to 700 °F (371 °C)
• Steam siphons for live steam applications

Mount the gauge remotely

Using a capillary line allows the instrument to be installed away from the process, reducing exposure to high or low temperatures.

Use a diaphragm seal assembly

A diaphragm seal used in conjunction with a temperature dissipator can provide additional protection in high-temperature applications.

For additional information, read: How Does Temperature Affect Pressure Gauge Performance?

Why is the IP rating important for pressure gauges used outdoors?

The IP rating determines how well a pressure gauge housing resists the ingress of dust and moisture.

When selecting instrumentation for outdoor service, it is important to consider the environmental conditions the gauge will encounter. Rain, washdowns, humidity, and airborne contaminants can all affect instrument performance if the case is not adequately sealed.

A pressure gauge's two-digit Ingress Protection (IP) rating indicates its ability to resist the entry of solids and liquids.

For outdoor applications, gauges with ratings such as IP65 or IP66 generally provide better protection against moisture ingress than lower-rated alternatives. Gauges with lower ratings, such as IP54, may be more susceptible to water intrusion from rain or washdowns. Selecting the proper case design helps prevent damage and supports long-term reliability in harsh environments.

Figure 3. IP Ratings Chart

How can pressure spikes and overpressure damage a pressure gauge?

Pressure spikes and overpressure conditions can reduce accuracy, damage internal components, or cause gauge failure. Overpressure occurs when process pressure exceeds the full-scale range of the gauge. Excessive pressure can deform or rupture the Bourdon tube, resulting in permanent damage and loss of measurement accuracy.

Proof pressure is typically between 130% and 150% of the gauge range and should not be exceeded if gauge integrity is to be maintained. Always review the manufacturer's specifications to determine the allowable operating limits of the instrument.

How can you protect a pressure gauge from overpressure?

Several options can help reduce the risk of overpressure damage.

• A pressure-limiting valve is designed to limit pressure to a predetermined value and only reopen when pressure returns to an acceptable range. This helps prevent damage to the gauge while maintaining system safety.

• An internal overload stop can increase proof pressure capability and provide additional protection during temporary pressure excursions.
  

• A solid-front gauge with a pressure-relief back helps direct pressure away from the front of the instrument in the event of a failure, enhancing operator safety.

How do pulsation and vibration affect pressure gauge performance?

Excessive pulsation and vibration can shorten gauge life, reduce readability, and damage internal components. Pressure fluctuations within pumps, compressors, and other processing equipment can cause pointer flutter and excessive wear within the gauge movement. Vibration generally falls into two categories:

• High-frequency vibration, which commonly cause pointer flutter, localized gear tooth damage, reduced readability

• Low-frequency, high-amplitude vibration, which common causes widespread gear tooth wear, increased stress on the Bourdon tube and reduced instrument life

As a general guideline, corrective action should be considered whenever pointer movement exceeds approximately 5% of the full-scale range.

How can you reduce the effects of pulsation and vibration?

Several solutions can improve gauge performance and longevity in dynamic applications.

• Use a liquid-filled gauge. These gauges use silicone, glycerin, or halocarbon fill fluids to dampen pointer movement and improve readability.

  • If a dry gauge is preferred, the Ashcroft® Duragauge® with PLUS!™ Performance is designed to dampen pulsation and vibration without liquid fill.
    
    

• Restrict process flow. You can reduce pressure fluctuations before they reach the instrument using accessories such as:

  • Pulsation dampeners

  • Steel needle valves

  • Diaphragm seals

• Install the instrument away from the vibration source. A capillary line, available in lengths up to 100 feet, can be used to remotely mount the gauge and reduce exposure to process vibration and mechanical shock.

Key takeaways

• Material compatibility, temperature capability, environmental protection, overpressure resistance, and vibration performance are the primary factors that determine whether a pressure gauge is suitable for chemical service.
  
  

• By evaluating these factors during instrument selection, you can improve measurement reliability, extend instrument life, and help support safer operation in demanding chemical and petrochemical processes.

Ready to learn more?

Now that you have a better understanding of the safety factors to consider when selecting a pressure gauge for chemical and petrochemical applications, you can use this information to make a more informed instrumentation decision. If you have questions, contact us to speak with an Ashcroft expert or take a look at the additional resources below. 

In the meantime, download our solutions guide to learn more about the common applications, and factors to consider when selecting pressure and temperature instruments for chemical and petrochemical processes.