10 Steps to Selecting Your Pressure Gauge

Ashcroft, a leader in pressure and temperature instrumentation, understands that you need accurate and reliable pressure gauges to keep your operation running efficiently. We also know the importance of following industry and regulatory standards for safety. However, finding the best solution to meet your unique specifications can be completely overwhelming.

We created this article to help simplify the pressure gauge selection process for you and give you confidence in your purchasing decision. When you are done reading, you will know about the primary factors to consider when selecting your pressure gauge and what steps to take in the pressure gauge ordering process.

Six factors to consider when selecting pressure gauges.

Before you start looking for the perfect pressure gauge for your application, yourself these six questions:

1. Does your pressure gauge meet your application’s safety requirements?

Protecting your people and process is a top priority, especially in potentially hazardous conditions. For instance, if you use specialized equipment to handle ultra-high pressure, a rupture in the process could hurt the operator, damage your equipment and disrupt your process. In this case, choosing a high-pressure, solid-front pressure gauge that meets ASME safety standards will help protect the operator from rupture blowback and keep your operation running.

2. Are the pressure gauge materials compatible with the process media?

The wetted material you choose must be compatible with your process media. If you are using the wrong materials, you may encounter instrument damage or failure. The Ashcroft Material Selection & Corrosion Guide can help ensure that you choose the proper instrumentation for your application's media.

3. What are your pressure gauge material traceability requirements?

Material traceability provides a documented record of the origin and composition of the pressure instrument’s materials. This traceability is crucial for ensuring that the wetted materials used in the instruments are suitable for the specific application's conditions, such as high pressures, extreme temperatures or corrosive environments. It also enables easier identification of any issues or recalls and simplifies bulk replacements.

4. Do you have the right instrumentation for your application?

Your application has specific requirements for pressure range, temperature and other factors. Ensuring your instruments meet those specific demands is critical. For instance:

Temperature: Pressure gauges are rated for use in a specific temperature range. Using gauges in temperatures outside of their range can lead to damage, depending on their design and construction. 

Range: Ashcroft recommends using ASME guidelines for selecting a pressure gauge with a full-scale range that allows the operating pressure to fall within the middle half (25% - 75%) of the scale. The full-scale range of the gauge should be about twice the desired operating pressure.

5. Do you know which product standards and/or approvals you need?

Whatever your required safety standards and regula­tions, Ashcroft has the necessary product approvals to validate that our instruments have undergone rigorous testing and comply with industry-specific requirements. This will give you confidence in the instruments' reliability and suitability for their intended applications.

Product Standards
• ASME B40.100
• EN 837-1
• CE
• RoHS
• Ingress Protection (IP65, 66 or 67, NEMA 4X)

Product Approvals
• 3-A
• Hazardous Location Approvals (ATEX)
• CRN
• R110

6. What's your budget? 

The cost of a pressure gauge depends on the application, features and accessories you need. For example, the cost of a pressure gauge that measures air in a tank will be vastly different than a pressure gauge used in a power plant or processing facility. Common cost factors will include:

Gauge Type – Depending on whether you need a commercial, industrial, critical process or test gauge, the cost could be anywhere from $10 - $1,000.

Features – Accuracy, dial size and pressure range requirements are also factors in gauge cost. Typically, more accurate pressure gauges, larger dials and certain pressure range needs, including vacuum and compound ranges can be more expensive.

Options and Accessories – Certain applications, especially those that involve hazardous conditions, may require options like a solid-front design, approvals, certificates and more that will add to the cost.

Selecting your pressure gauge in 10 simple steps.

Pressure gauges are not a one-size-fits-all solution. To ensure you get the best pressure gauge for your needs, be prepared to know the following:

1. Where and how will your pressure gauge will be used? 

The type of pressure gauge you choose will depend on the industry and application. For instance, a gauge used in a high-purity environment has different requirements than one used in hydrogen systems. 

Figure 1. Pressure Gauge Application Options.

2. Whether your pressure instruments require any approvals. 

Some applications require approvals from nationally or internationally recognized agencies. See Figure 2.

Figure 2. Pressure Gauge Approval Requirements.

3. The type of pressure you are measuring. 

There are two gauge styles:

• One for measuring differential pressure. Measures the difference in pressure between two points in a system.
• One for measuring gauge pressure. Measures positive pressure and vacuum pressure that is referenced to atmospheric pressure, and compound pressure that measures both positive and vacuum. 

4. The pressure gauge size. 

The dial or case size can vary based on the application and dimensions of where the gauge will be used:

• ≤2" (50 mm) - Smallest sizes for compact areas.
• 2.5" (63 mm ) to  3.5" (90 mm) - Small sizes typically for high volume, commercial uses.
• 4" (100 mm ) to 6" (160 mm) - Common sizes for most process applications.
• 8.5" (215 mm) and above  - Large sizes for easy viewing from a distance or test measurement and validation.

Read, Choosing a Pressure Gauge Dial Size to learn more.

5. The case style. 

The style you need will depend on your application and safety requirements.

• Open front. This style is designed with a pressure relief plug. There is no partition or barrier between the pressure element and the window. These cases are less expensive and most often used in commercial applications. 
• Solid front. This style has a blowout back design for added safety in hazardous environments. It has a partition with minimal openings between the pressure element and the window. These cases are typically more expensive and are often found in high-pressure applications in process plants, for example, that have the possibility of rupturing. 
  

Read, Solid Front vs. Open Front Pressure Gauges to learn more. 

6. The desired case material. 

The case material you select must align with specific industry specifications and/or requirements. For instance: 

• Aluminum is often used for rugged outdoor applications that require metal construction.
• Phenolic/thermoplastic can be found in process or specialty applications requiring corrosion resistance. 
• Stainless steel is used for sanitary applications and corrosion resistance.
• Steel/black metal is a lower-cost option that is appropriate for high-volume commercial use. 

7. The connection location.

This is where the pressure gauge will connect to the process. Your options will be: 

• Lower: connects to the process from the bottom of the gauge.
• Lower back: connects to the process from the lower back of the gauge.
• Center back: typically for panel mounting, the connection is from the back center of the gauge. 
• In-line: this connection goes through the two ports on either side of the gauge and is specially designed for differential and sanitary gauges. 

8. The required pressure range for your application.

For this step, the range must align with the operating pressures of your process and follow ASME B40.100 best practices, which state the following: 

• Operating pressure should be 25% to 75% of scale, and the gauge range should be twice the operating pressure.
• Ideally, the mid-scale on your dial should be around 12 o’clock or the mid-scale of the full-scale gauge span.
• If pulsation is present, the maximum operating gauge pressure should not exceed 50% of the full-scale range.
  

Options include: 

• ≤10 psi (0.7 bar): Including gauge, vacuum & compound for low-pressure ranges
• 10 to 5,000 psi (0.7 bar to 350 bar): Including gauge, vacuum & compound for low-pressure ranges
• 5,000 to 20,000 psi (350 bar to 1,400 bar): Including gauge, vacuum & compound for low-pressure ranges
• 20,000 to 100,000 psi (1,400 bar to 7,000 bar): Including gauge, vacuum & compound for low-pressure ranges
• ≤10 psid (0.7 bar): Low differential pressure
• 10 to 1,000 psid (0.7 bar to 70 bar): Mid-to-high differential pressure

9. The accuracy requirements for your application. 

The accuracy of your pressure gauge should align with your application requirements and ASME B40.100 or EN837-1 best practices.

• ≤±0.25% of span - for high-accuracy test and measurement applications. The best accuracy is as high as 0.05% of span.
• ±0.5% to ±1.0% of span - for high to mid-accuracy process applications.
• ±1.6% to ±2.5% of span - for mid-accuracy industrial applications.
• ≥±3.0% of span - lower accuracy for general-purpose applications.

Read our blog to learn more.

10. The gauge's wetted materials. 

If you want to avoid instrument problems stemming from corrosion, you should ensure the material for the instrument’s wetted parts is compatible with the process material’s composition, concentration and temperature. If it is not possible to choose a compatible wetted material, you can integrate a diaphragm seal/instrument isolator or isolation ring constructed from an appropriate material for the process. Check out our Material Selection & Corrosion Guide to find compatible options for your application. 

Want to learn more?

Now you know all the factors to consider before purchasing your pressure gauge and the 10 steps to narrowing your search to the one that is best suited for your application. Remember, many applications present a unique set of challenges that can damage your pressure gauge and adversely affect your operation. If your pressure gauge will be required to withstand harsh conditions, Ascroft offers several accessories that are specifically designed to protect your instrument and optimize its performance.

If you still have questions, feel free to talk to one of our industry experts. In the meantime, here are a few articles we’ve written to address our customers' FAQs:

• How To Identify Your Pressure Gauge and Get the Proper Replacement
• How Does Temperature Affect Pressure Gauge Performance?
• How Do I Select the Right Pressure Gauge Range?
• How Often Should I Check the Calibration of My Pressure Gauge?

 Are you ready to get started? Our online Pressure Gauge Selection Tool can help!