No matter what industry you work in, diaphragm seals (also referred to as isolators) and welded assemblies are used to protect your pressure and temperature instrumentation from corrosive process media.

After decades of making quality pressure and temperature gauges and sensors to help keep processes performing reliably and efficiently, Ashcroft has seen just about every scenario where something can go wrong. One reason we like to share our expertise is to help people like you who may be experiencing a similar issue that we can help solve.

In this article, you will learn what a welded diaphragm seal assembly is and how it is used to help mitigate the damaging effects of high temperature, pulsation and vibration endured by your instruments. You will also see how these assemblies can ensure reliable and accurate pressure readings of your process.

When you are done, you will find links to additional resources that can help you learn more about related topics.

What is a Welded Instrument Assembly?

Simply put, a welded instrument assembly consists of a mechanical measurement instrument like a pressure gauge and an accessory welded together to provide the specific protection you need.  Different conditions and product specifications call for different accessory assemblies. For example:

For corrosion and clogging protection.

• A diaphragm seal/isolator.  Protects the gauge sensor from corrosive process media and prevents clogging of the instrument from a dirty process.

Figure 1. Ashcroft®  

For pulsation protection. 

• A pulsation dampener. Protects measuring instruments from sudden increases and fluctuations of pressure.

Figure 2. Ashcroft® Pulsation Dampener.

For elevated temperature protection.

• A finned siphon. The reduced orifice decreases the volume of the process medium in the siphon allowing efficient heat transfer between the medium and the siphon. 

Figure 3. Ashcroft® Finned Siphon.

• MicroTube™and Mini MicroTube Siphon. The reduced internal volume of these accessories allows for superior temperature dissipation. 

Figure 4. Ashcroft® MicroTube™ and Mini MicroTube™ Siphon.

• A capillary line. This accessory prevents direct contact between the gauge and the installation point to protect it from elevated temperatures or pressure spikes.

Figure 5. Ashcroft® 1115 Capillary Line.

Instruments attached directly to seals can be welded, and assemblies with some accessories can be welded at each connection. However, there are some exceptions. Accessories like snubbers that help protect gauges from pulsation issues, and valves that help with isolation valves cannot be welded since they contain elastomers that will be compromised with the elevated weld temperature.

Figure 6. A Welded Instrument Assembly Example.

Why material compatibility is important in welded assemblies. 

Materials that will be welded together must be compatible. For example, 316 Stainless steel cannot be welded to Monel. If the materials are not compatible, the instrument can be compromised and become ineffective. The good news is there are many material options available for the wetted portion of a diaphragm seal to ensure compatibility with the process media.

How instrument accuracy is affected
Generally, an accessory attached to a gauge does not change the accuracy of the gauge. However, attaching a diaphragm seal/isolator to a gauge can typically reduce the gauge accuracy by ± 0.5% of span.

When it is necessary to weld a gauge to a diaphragm, Ashcroft confirms appropriate assembly accuracy tolerance after the assembly is welded, filled and calibrated. For example, an Ashcroft® 1279 Pressure Gauge with an accuracy of
± 0.5% when it is attached to a diaphragm seal, will usually have an accuracy of ±1% of span.

If the same Pressure Gauge is welded to a MicroTube™ Siphon and a Threaded Diaphragm Seal and then filled and calibrated, the typical gauge accuracy of the assembly will also be ± 1% of span. So, additional accuracy occurs only when a diaphragm seal is added to the assembly.

Why Use a Welded Instrument Assembly?

More and more customers are seeing the value of a welded instrument assembly. A welded instrument assembly can be used in any application and is good for all industries.

Prevents accidental tampering or disassembly. A welded assembly is tamperproof and prevents a diaphragm seal from being detached from the gauge. This is important because removing the gauge from the seal breaches the assembly's system integrity and will render the gauge inoperable.

The tamperproof welded design also prevents an important accessory from being removed. For example, if the process temperature is 800 °F/427 °C, design engineers may specify that a siphon needs to be attached to the assembly to dissipate process temperature and protect the gauge. If the siphon is removed from an assembly that is not welded, the gauge will lose its integrity and not give an accurate process pressure reading.

Primary benefits to welded assemblies. 
A welded assembly provides peace of mind that the components of the assembly won’t be removed. Here are a few other reasons why a welded assembly can benefit you.
 

Note: If at some point welded components need to be replaced, replacement of the complete assembly would be required. Replacing individual instruments and accessories of a welded assembly is not an option. Breaking any welded connection of an assembly would result in damage to the instruments and accessories.

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

Selecting the correct electrical connection for a pressure transducer helps ensure your equipment continues to operate effectively, even when affected by vibration, moisture, dust, or temperature extremes that can compromise performance. From off-road equipment to process automation systems, choosing the wrong connector can lead to signal loss, premature failure, or even safety risks.

As a recognized authority in pressure and temperature instrumentation, Ashcroft has extensive experience helping engineers and operators protect their systems in the harshest conditions. Read this article to learn the factors to consider when selecting an electrical connector for a transducer:

• Why connector selection directly affects sensor reliability and longevity
• What environmental conditions should guide your connector choice?
• What installation and wiring factors should you consider?

Why is selecting the right electrical connection so important for pressure transducers?

Electrical connections do more than deliver power and transmit output signals—they provide essential protection against environmental hazards. A weak or poorly matched connector can cause intermittent readings, corrosion, or total sensor failure.

For example, in mobile hydraulic systems or compressors, connectors endure high vibration and thermal cycling. Over time, these stresses can loosen fittings or compromise seals, allowing moisture or debris to enter. The result is drift, erratic output, or short circuits. Reliable connections ensure:

• Signal integrity: Stable voltage or current output without dropouts
• Environmental protection: Proper sealing against contaminants like dust and oil
• Serviceability: Ease of installation, maintenance, and replacement
• Safety: Electrical isolation in hazardous locations where explosive gases or dust may be present

Ultimately, the right connector enhances the durability and reliability of the pressure transducer throughout its service life. When choosing an electrical connector that would function best in your application, be it indoors or outdoors and exposed to the elements, there are many factors to keep in mind.

What environmental conditions should guide your connector choice?

The environment in which a transducer operates determines the level of protection required. For instance, will your pressure transducer be installed outside, or will it be regularly exposed to moisture, dust or sunlight?

Both the National Electrical Manufacturers Association (NEMA) and the International Electrotechnical Commission have established standards, which specify how effectively a transducer's enclosure keeps the user safe from electrical hazards and prevents the entry of solids, liquids and other contaminants into the instrument.

NEMA rating examples

There are many different NEMA ratings that define how well an enclosure performs in different environmental conditions, including:

• NEMA 4 enclosures provide a degree of protection to personnel against incidental contact with the enclosed equipment. It protects against windblown dust and rain, splashing water and hose-directed water, making them ideal for outdoor use.
• NEMA 4X offers similar protection but with added resistance to corrosion, which is common in food, beverage or chemical processing environments.
• NEMA 7 enclosures are designed to contain an internal explosion without causing an external hazard.
• NEMA 9 enclosures are designed to prevent the ignition of combustible dust for use in hazardous areas.

Most Ashcroft pressure sensors predominately fall into the NEMA 4, NEMA 4X, NEMA 7/9 category ratings. For example, the Ashcroft® E2G Pressure Transducer has a NEMA 4X rating, so it offers the same protection as the NEMA 4, with the addition of corrosion resistance.
 

IP rating examples

In a previous article, we explained that ingress protection (IP) ratings typically consist of two numbers. The first indicates how well the instrument protects against solids (like dust). Solid ratings go from a low of 1 up to the highest rating of 6. The second number indicates how well the enclosure or sensor protects against liquids. See Figure 1 for full list. 

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

In industries where temperature extremes, vibration, or hazardous process environments are part of daily operations, accurate and reliable temperature measurement becomes a serious challenge. In these environments, operators need instruments that deliver accurate readings from a safe distance, reducing the need to approach hazardous areas.

Gas-actuated thermometers are an effective solution for these applications. Their robust design, wide measurement range, large dial size and remote mounting capabilities make them ideal when both safety and accuracy are priorities.

As a global authority in pressure and temperature instrumentation, Ashcroft has helped manufacturers and process operators improve reliability and reduce downtime for more than a century. In this article, you’ll learn:

• How gas-actuated thermometers work
• When and where they are most effective
• Why remote mounting and thermowell selection matter
• Which design options can extend instrument life in extreme conditions
   

When are gas-actuated thermometers used?

Gas-actuated thermometers are best used when applications involve:

• Extreme temperature ranges. Common in refineries and power generation plants, where process media can swing from cryogenic to several hundred degrees and standard thermometers cannot operate reliably.
• Vibration or shock. Found in offshore oil rigs or pulp and paper mills, where rotating machinery or pumps can cause continuous vibration. The “movementless” Bourdon tube design helps minimize wear and eliminates pointer flutter.
• Remote monitoring requirements. Typical in chemical and petrochemical facilities, where operators must read temperatures from safe control areas away from high-pressure or corrosive processes. Capillary lengths up to 80 feet or 100 meters allow operators to mount the dial in a safe, accessible location while the sensing bulb is near the process source.
• Hazardous or confined environments. Seen in food, beverage, and pharmaceutical manufacturing, where sanitary requirements or confined equipment layouts make remote mounting safer and more practical. Remote mounting lets personnel take readings from control panels or safe areas, away from heat, obstructions, or caustic media.
• Outdoor or wide-area systems. This can include water and wastewater treatment sites, where thermometers may need to be installed far from monitoring stations.
   

How do gas-actuated thermometers work?

Gas-actuated thermometers use a Bourdon tube system filled with an inert gas to sense and indicate temperature changes. As the temperature rises, the gas expands within the sealed system, creating pressure inside the Bourdon tube that moves the pointer across a calibrated scale.

In remote-mount designs, the gas pressure travels through a capillary line that connects the sensing bulb to the dial, allowing the indicator to be installed at a safe or more accessible distance.

Because the system is completely sealed and filled with gas, it delivers fast response, linear accuracy and stable readings across a wide range—from approximately –320 °F to 1,200 °F (–200 °C to 650 °C).

This design makes gas-actuated thermometers ideal for both direct-mount installations and remote applications where the sensing bulb and dial must be separated for visibility, accessibility, or operator safety.

Electric contact switches can be added to the thermometer for process alarm or control.

Why is remote mounting important for gas-actuated thermometers?

Remote-mounted thermometers separate the dial indicator from the temperature-sensing bulb, connected by a gas-filled capillary line. This configuration helps:

• Reduce vibration damage by isolating the sensitive indicator from pumps, compressors, or piping.
• Protect operators from hot or hazardous process zones.
• Simplify readings by allowing installation on panels or easily visible control stations.

Ashcroft’s Duratemp® 600A and 600H-45 Gas-Actuated Thermometers, for example, offer bendable extension bulbs with adjustable union connections that can be freely positioned for the best insertion depth. The armored capillary provides added mechanical protection.

How do bulb and thermowell configurations affect performance?

The bulb acts as the sensing element, while the thermowell shields the bulb from pressure, corrosion, and velocity effects. Two common bulb types are:

• Plain bulbs. Best for air or liquid measurement in open tanks or low-pressure environments.
• Union-connected bulbs. Threaded fittings that secure the bulb into a thermowell, making them ideal for pressurized or corrosive processes

Using a thermowell not only extends the thermometer’s service life but also enables instrument interchange or recalibration without process shutdown—a best practice across high-reliability industries.

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

Monitoring low-pressure processes comes with unique challenges. In industries ranging from food and beverage to wastewater treatment to liquefied natural gas (LNG) transfer, even modest changes in pressure can affect efficiency, product quality, or safety. Directly exposing instruments to these processes often leads to media buildup, corrosion, or inaccurate readings. That’s where using assemblies that combine pressure gauges, transducers, or switches with diaphragm seals or isolation rings can help.

Ashcroft, a leading authority in pressure and temperature instrumentation, has decades of experience helping industries overcome these challenges. As the product lead for diaphragm seals and accessories, I help customers find the best assembly for their specific needs. Read on to learn:

• How different industries and instruments define “low pressure”
• Which assemblies work best with gauges, mechanical switches and sensor-based instruments
• How assemblies support applications across sanitary, industrial, utility and cryogenic environments — with LNG as a primary example
   

When you are finished, you will know how to ensure accurate measurement and keep your operations running efficiently with the right seal or isolation ring assembly.

What does “low pressure” actually mean?

The definition of “low pressure” depends on who you ask and which instrument or industry you’re working with. At Ashcroft, we define low pressure as anything below 15 psi. This threshold matters because diaphragm flexibility, seal fill fluids and instrument sensitivity all affect accuracy below this point.

However, in industry terms, HVAC or wastewater can also define “low pressure” as anything under 30–50 psi since those systems normally run higher. Finally, there are also instrument variations:

• Pressure gauges: often anything under 15 psi.
• Switches: can go much lower, down to inches of water column (inH₂O) set points.
• Sensor-based instruments, such as transducers, generally require a minimum span of 15 psi when paired with a diaphragm seal.
   

These variations are why it’s important to choose the right assembly for your exact application. What qualifies as “low” in one industry may be considered normal in another, and the wrong pairing of seal and instrument can compromise performance.

How do assemblies support different industries?

Every industry faces different challenges when monitoring low pressure. Assemblies provide tailored solutions across a wide range of applications. When selecting assemblies, material compatibility is just as important as pressure range. Using diaphragm seals made from corrosion-resistant alloys such as 316 stainless steel, Monel® or Hastelloy® helps prevent instrument damage from aggressive or abrasive process media.

Here’s how assemblies ensure accuracy, protection and compliance across critical applications.

Figure 1: Industry assembly challenges

In cryogenic environments, selecting wetted materials resistant to embrittlement — such as 316 stainless steel or Monel® — helps maintain long-term performance.
 

What are the instrument considerations for low-pressure assemblies? 

Selecting the right assembly isn’t just about matching a diaphragm seal to an instrument. It’s also about knowing the capabilities and limitations of each type of device. Low-pressure gauges, switches and sensor-based instruments all behave differently when paired with seals and isolation rings, and each has specific requirements.

In this section, we outline some recommendations and restrictions for 4 instrument types. The Ashcroft product examples are used to illustrate how these rules apply in practice, helping you avoid misapplications and ensure your assemblies perform accurately and reliably. For a full reference, read the Ashcroft Diaphragm Seal Pressure & Temperature Min/Max Guide.

1. Pressure Gauges
Pressure gauges are widely used for local indication, giving operators a direct, real-time reading of system pressure right at the process line. They’re simple, reliable, and require no external power, making them ideal for monitoring lines, vessels, or systems where visual feedback is critical.
 

Recommendations for use in low-pressure applications

• Bellows gauges are a good choice for applications where accuracy at extremely low ranges is critical, such as tank level monitoring or low-pressure gas systems.
• For example, a gauge like the Ashcroft® 1188 Low-Pressure Bellows Gauges requires a minimum span of 60 inches of water (~2.2 psi), making it ideal when small changes in pressure must be detected.
• These gauges can be paired with the Ashcroft® 200/300 Series Viton™ or Kalrez® diaphragm seals or the Ashcroft® 740/741 Series metallic seal, which provides the flexibility needed for such low spans. 
   

Restrictions for use in low-pressure applications

• Don't use vacuum or compound ranges at these spans with metallic diaphragms because metallic materials lack the flexibility that elastomers provide.
• Avoid using any general-purpose or commercial gauges that are not designed for seal assemblies.
   

2. Pressure Switches
Pressure switches are designed for control and safety functions, automatically triggering an alarm, pump, or shutdown when pressure crosses a set limit. For instance, you will see them used in low-pressure processes that depend on stable pressure conditions, such as filtration systems, pump control, or pressure safety interlocks.
 

Recommendations for use in low-pressure applications

• Choose switches that can operate at very low set points, even down to inches of water column (inH₂O), to ensure precise control and early detection in applications where minimal pressure changes can impact safety, efficiency or product quality.
• For example, the Ashcroft® Pressure Switch Series A, B, G, L and P can function at these extremely low set points, ensuring your process will operate reliably in sensitive, low-pressure environments. (See Figure 2 below.)
• Pair the pressure switch with a high-displacement diaphragm seal like the Ashcroft® 740/741 to achieve the desired low set points. Or, you can pair switches with flexible diaphragms like those found in the Ashcroft® 200 Series, offered with Viton™ or Kalrez®. These materials are used when setpoints are between 6 - 20 Inches of Water

Note: Set points higher than 6 psi can use any seal or isolation ring material.

Figure 2: Minimum set points for mechanical pressure switches

Restrictions for use in low-pressure applications

• Do not set switches below their published limits. Some ranges are not recommended for remote mounting with a capillary because of signal dampening.
• Avoid using incompatible fill fluids, like glycerin, which cannot be used in spans under 15 psi or in vacuum service. 
   

3. Sensor-Based Instruments (Digital Gauges, Transducers, Electronic Switches)
Sensor-based instruments are typically used in automated systems that require continuous monitoring, remote control, or data integration. They provide electrical outputs for control systems, making them ideal for modern process facilities, sanitary applications and critical environments like LNG or pharmaceutical production.
 

Recommendations for use in low-pressure applications

• Sensor-based instruments are the best choice when you need precise data and integration with control systems, such as in automated LNG or sanitary processes.
• For example, the Ashcroft® E2 Sanitary Pressure Transducer, Industrial Digital Gauges and NPI Electronic Pressure Switch deliver high outputs for advanced system integration.
• These instruments should only be used in applications with a minimum span of 15 psi when paired with diaphragm seals.
   

Restrictions for use in low-pressure applications

• Do not specify sensor-based instruments for spans below 15 psi, as accuracy cannot be maintained.
• Avoid overlooking temperature effects — using the wrong fill fluid can lead to calibration drift, especially at the low end of the pressure range.

Figure 2: Low-pressure instrument assemblies comparison

How do you choose the right assembly for your application?

Selecting the proper assembly isn’t just about protecting the instrument — it’s about ensuring your readings remain accurate and reliable over time. The wrong pairing of seal, instrument and fill fluid can lead to drift, clogging or even premature failure.

In addition to proper sizing, material and fill fluid selection are critical factors in low-pressure assemblies. The Ashcroft® Corrosion Guide recommends matching seal materials and elastomers to the process fluid to prevent swelling, hardening or corrosion, which can lead to inaccurate readings or premature failure.

By considering a few key factors, you can narrow down the best assembly for your low-pressure environment.

• Match the pressure span of your application to the diaphragm seal’s displacement.
• Select the instrument type (gauge, switch or sensor) based on your specific needs.
• Consider media compatibility, temperature ranges and cleaning needs.
• Use Ashcroft’s expertise and selection tools to avoid trial-and-error and get it right the first time.

For pressure gauges, following ASME B40.100 guidelines, operating pressure should fall within the middle 25–75% of the gauge scale, and the instrument’s full-scale pressure should be approximately twice the expected operating pressure. This ensures both accuracy and safety in low-pressure measurement.

Talk to one of our experts today at (855) 737-4714, or fill out our online form to learn more. 

Heating, ventilation and air conditioning (HVAC) systems are the backbone of building comfort and safety. Because these systems operate continuously and consume significant energy, even small inefficiencies can drive up operating costs.

At Ashcroft, a leading producer of pressure instruments for multiple industries, including HVAC, we provide insights and recommendations to engineers and facility managers like you to help improve system performance and reliability.

For instance, we know that instrument accuracy is one of the most important factors in maintaining HVAC efficiency. Pressure sensing instruments, like transducers, monitor the system’s conditions and help automation controls that adjust fan speeds, pump flows and valve positions. Inaccurate sensor measurements can cause systems to overwork, leading to wasted energy and unnecessary expense.

Read this article to:

• Examine how HVAC systems function and the factors that can influence measurement reliability.
• Learn how pressure sensors optimize HVAC system performance
• Understand why accuracy is so important
• Compare the different methods used to determine accuracy
• By understanding these elements, you’ll be better equipped to evaluate pressure sensors that support both building performance and cost savings.

What is the role of a pressure sensor in your HVAC system?

An HVAC system balances multiple processes to maintain indoor comfort and efficiency. Key functions include:

• Air distribution. Fans and ductwork move conditioned air throughout the building.
• Heating and cooling. Hot water circulates through coils for heating, while chilled water runs through coils for cooling and dehumidification.
• Air quality control. Filtration and ventilation ensure proper oxygen levels, remove particulates and maintain humidity within safe limits.
   

All of these processes use energy and cost money, so it stands to reason that the more efficiently they run, the less the system costs to operate. To ensure high efficiency, you must verify that the pressure sensors you use to monitor and control the flow of air through ducts, hot water through heating coils, and cold water through chillers and dehumidification coils are highly accurate.

One way to ensure an efficient HVAC system is to verify the accuracy of the pressure instruments used in the system.

What can affect pressure sensor accuracy in HVAC applications?

Even though pressure instruments are designed for reliable measurement, five conditions in HVAC systems can affect their accuracy:

• Temperature changes. Shifts in ambient or process temperature may cause zero or span drift.
• Mechanical stress. Vibration from fans, pumps or compressors can introduce error or reduce service life.
• Installation factors. Improper mounting or orientation may require recalibration.
• System dynamics. Rapid load changes can cause hysteresis or repeatability issues.
• Environmental influences. Dust, moisture or corrosive air streams can degrade performance over time.

Understanding these influences is essential when selecting and maintaining pressure instruments for HVAC service

Why does pressure sensor accuracy matter in HVAC systems?

Accuracy refers to how far the measured value of a specific pressure is from the accepted allowable error of that measurement. The accuracy of a pressure instrument is determined by the maximum positive and negative difference between the measured value and its ideal value. This allowable error is calculated as a percentage of the measured output of the sensor versus the ideal output, and it is expressed as a percentage of the full span of the sensor.

Pressure instruments with greater accuracy provide a more accurate indication of the actual pressure conditions, which allows HVAC controllers to better manage the heating and cooling needs of the building. However, the accuracy alone does not fully define an instrument’s ability to measure pressure, which is why pressure instrument manufacturers incorporate accuracy as part of a larger accuracy statement.  

Are all accuracy statements the same?

No. Because the HVAC industry lacks a universal standard, accuracy statements can differ widely. Some use root sum squared (RSS) or best fit straight line (BFSL) methods, which may exclude important errors such as zero offsets, span shifts or temperature effects. The result: additional on-site calibration, higher installation costs and reduced out-of-the-box equivalency.

RSS and BFSL accuracy statements often overlook important factors, resulting in reported accuracy that may not reflect actual instrument performance. These methods typically exclude zero and span offsets, meaning additional installation errors may occur at both the low and high ends of the measurement range. As a result, installers may need to calibrate instruments on-site using a secondary standard, increasing startup costs, eliminating out-of-box interchangeability, and impacting overall system performance. Ultimately, these required adjustments add expenses for building owners who expect pre-calibrated sensors.

What are common sources of accuracy error?

In determining the accuracy of pressure instruments, consider all factors relevant to the specific application that could lead to measurement errors. Some of the most common sources of error include:

• Nonlinearity error – deviation from a straight output line
• Hysteresis error – output differences in response to increasing versus decreasing pressure        
• Non-repeatability error – inconsistent readings under identical conditions
• Zero and span errors – offsets at both ends of the measurement range
• Temperature coefficient errors – zero and span shift caused by ambient temperature changes
   

What is the best method to determine accuracy?

While not all methods consider each of these errors, the terminal point method, which includes zero and span offsets in its error determination, is the most reliable calculation for HVAC applications. This method determines the actual error for a pressure instrument, allowing manufacturers to better indicate the accuracy of their products and contractors to better manage the heating, cooling and subsequent low airflow in their HVAC systems.

Talk to one of our experts today at (855) 737-4714, or fill out our online form to learn more. 

There are three distinct phases involved in removing or displacing water from another liquid.  The first is particulate filtration.  Many refer to this stage as prefiltration.  During this phase, the goal is to remove as much particulate from a liquid as possible before it enters into the next portion of the process.  During the second phase, coalescing, the liquid enters a coalescer where we develop small droplets of water where it then combines into larger droplets of water, making it easier to remove.  During the third stage, separation, we’re aiming to completely separate the water from the rest of the liquid.  Essentially, the separator will act as a screen and repel any water droplets that are still around the stream.  However, the only way to ensure that this final stage does its job is to be confident that stages one and two are done properly. Part two (coalescing) is becoming more of an essential step in more and more industries, especially those that involve fuel and oil.

For coalescing to have the desired impact, it must be handled properly.  This means walking through the process of properly sizing and specifying the tools we’re using for this stage. And this all starts with accurate inputs. 

First, we must have a complete understanding of the operating parameters in a system.  More specifically, we want to know the flow rate, operating pressure, operating temperature and the liquids at play.

Particulate filtration is an essential but not exactly a complicated exercise. You can be both cost conscious and effective in this stage as oversizing a filter will achieve both.  When a filter is oversized, operators can be confident that the filter will do its job properly, and they will spend less time replacing them, saving on operating costs.

However, if you apply this principle to coalescing, it will no longer be effective.  We must combine the particles, so knowing the flow rate is essential.  If the rate is too low, the liquid may not separate.  If it’s oversized, the velocity isn’t high enough to coalesce properly.  When sizing the coalescer, we’re looking for optimal efficiency, staying within +/- 15% of the design operating parameters of the system: flowrate, temperature and pressure.  The general principle of sizing is based off Stokes law.  

Coalescing is a critical step in the filtration process. If you’re unsure about your setup, and want to ensure optimization, reach out to one of our experts to help walk you through what will work best for your process. Along with my colleague Joe Bodle, I wrote an article about this subject that was published in International Filtration News last year.  Give it a read if missed it.