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Thank you for taking the time to learn more about diaphragm seals. These seals play an essential role in protecting various pressure instruments across a range of industries. The sensing elements of pressure gauges and switches need to be isolated from process fluids in many cases. Diaphragm seals are designed to seal enclosures within these delicate instruments, separating them from dangerous media.

These seals must also act to keep the process fluid from being affected by contact with the sensor. This is especially important in the food and beverage industry, where fluid accumulation can result in health concerns. The use of the right diaphragm seal prevents bacteria development over time. In other cases, the pressure sensor itself may cause metallic contamination of the process fluid; diaphragm seals stop this from occurring.

Common Diaphragm Seal Applications

A wide variety of seal types are available, to be used for a range of purposes. There are a number of common diaphragm seal applications to be aware of. They are frequently used with instruments in the oil and gas/chemical field. Complete process control and reliable monitoring is essential throughout the oil drilling, production, and refinement process, so taking great care of your pressure instruments is vital.

Likewise, energy companies require the use of a variety of instruments for generators, transformers, turbines, pumps, and more. The sensors used to monitor pressure in the energy field should be protected with diaphragm seals. Other industries include:

  • Water and Waste Water
  • Transportation and Logistics
  • Machinery
  • Laboratory and Medical
  • Food and Beverage

About Diaphragms

Generally, diaphragms are made from metal, rubber, Teflon, plated metal, or other coatings. Diaphragms range from 0.002” to 0.008” in thickness. Their diameter is typically 5/8” of an inch or larger. They may be welded between two metal housings, welded to an upper housing, or clamped between two solid housings, depending on the type of diaphragm used.

It is important to bear in mind that the diaphragm and seal you use will reflect your specific application. Every industry has different requirements and distinct pressure instruments necessitate the use of different types of seals. Always ensure that the seal you use matches the specification situation. Don’t hesitate to reach out for assistance when attempting to make a determination in this regard. The experienced team at ESP would be happy to guide you every step of the way.

Common Types of Diaphragm Seals

Diaphragm seals are commonly categorized according to their process connection. The type of connection used must be determined based on the intended application. Please take the time to learn more about a few common types of seals.


Threaded diaphragm seals feature threaded process connections. Several types of this seal are available. Depending on the application and seal type, they may be mounted to pressure gauges, transmitters, switches, or to a cooling element.

Some threaded seals may also be connected with a flexible capillary. In all cases, the filling fluid used in the measuring system must be chosen based on the application. Features available with threaded diaphragm seals may include:

  • Internally Welded Diaphragms
  • Exchangeable Lower Parts
  • Exotic Material Options for Wetted Parts
  • Cleaning Rings
  • All-Welded Designs
  • Full Stainless Steel Materials
  • Compact Designs
  • Flush Diaphragms


Flanged diaphragm seals allow direct mounting on pipes, tanks, and standardized flange connections. Typically, they are mounted to pressure gauges and switches directly, or with the use of a flexible capillary. As with all seals, the flanged option should be selected based on process compatibility. Various diaphragm materials may be used to keep the seal in line with selected process fluids and applications.


Sanitary diaphragm seals feature hygienic process connections. This ensures efficient cleaning. They also help to avoid pollution and the development of bacteria during hygienic production processes. These are essential in the food and beverage industry where contamination most be avoided at all costs.

Likewise, the laboratory and medical fields have strict standards in place to ensure safety. Diaphragm seals must conform to FDA requirements or possibly match Sterilization In Place (SIP) and Clean In Place (CIP) methodologies.


In-line diaphragm seals are internal to metallic bodies. They are used with a range of connection types and come in various sizes. These seals replace the process “T” in media flow, and allow for laminar flow to occur. Use of an in-line seal greatly reduces the risk of mishandling a diaphragm. This prevents unnecessary damage from occurring, protecting your investment. In-line seals also remove dead space where bacteria grows, and prevent media from building up in the diaphragm over time.

Finding the Right Type of Diaphragm Seal

With so many options available, it can be difficult to decide on the right diaphragm seal for your application. Trust the team at ESP to provide you with the expert advice you need to make the right decision.

Why Use a Diaphragm Seal?

The sensing elements of pressure gauges and switches are vulnerable to corrosive, sedimentous, and viscous fluids, as well as fluids with high temperatures. The purpose of diaphragm seals is to isolate the sensing element of pressure switches and gauges from these fluids. There are many reasons why using a seal for this purpose is essential across various industries.

Protect Your Instruments for Years to Come

Pressure instruments are delicate. Extreme temperatures can easily damage their sensors, rendering them useless. They are subject to clogging, as process media builds up within the instrument’s internals. Over time, this can lead to fluid solidification. Without the use of a diaphragm seal, excessive cycling damage may occur.

There’s also the matter of material compatibility. Some sensors may not be compatible with the process media being used. This can result in both damage and media contamination. It is critical to prevent either from occurring, to keep your instruments in optimal condition at all times. The best way to do so is with the use of a quality diaphragm seal, purchased from a company you can trust to provide you with quality products.

Customize a Solution That Matches Your Needs

Diaphragm seals may be used in a large number of applications, across many industries. Their process connections can be adapted to your industry standard, including flanged, sanitary, flow-through, and male and female threaded options. This allows for a great deal of adaptability and a spectrum of functionality options when selecting diaphragm seals.

The needs of an oil and gas company are different than those of one operating in the food and beverage field. The variety of process connections and seal types available allows for compatibility with your company’s requirements, no matter your industry. The best option is always the one that fulfills your needs precisely. ESP is here to help you find it, with detailed product information and in-depth technical expertise. You’ll receive the information you need the first time you ask for it, because your time matters to us.

Maintain Safety at All Times

Diaphragm seals enhance the safety profile of your facility in different ways based on the type you use. Sanitary or hygienic processes require the use of certain seals to prevent contamination and media buildup. Diaphragm seal remote mounting allows for safety away from extreme temperatures and makes viewing instrument readings easier. Using the right seals will save you time and ensure compliance with safety standards, such as those set by the FDA.

How to Select Fill Fluids

Making the right diaphragm seal fill fluid selection is important. You understand your process and parameters well, but having a partner to assist you is always helpful. ESP will supply detailed data to help inform your decision regarding the type of system fill fluid you use. Outside of direct advice from ESP, there are several principles to keep in mind.

The Foundation of Fill Fluid Choice

When choosing a system fill fluid, you must base your decision on several factors. These include the pressure, process media, and temperature. Additionally the type of application must be considered. ESP is happy to provide you with detailed information regarding all of these factors upon request. Don’t hesitate to reach out to us for additional details regarding the fluid selection process.

Common Fluid Types and Typical Applications

There are many diaphragm seal fill fluid types available. Each type of fluid fulfills a specific purpose and is typically ideal for use within a certain set of applications. For example, Vaseline and mineral oil are used in food and pharmaceutical applications, as well as all standard devices. They are approved for use by the FDA.

There are many silicone seal fill fluid types to consider. Silicone DC510-100 is ideal for low-temperature use, while silicone DC550-100 is used with high temperatures. Silicone DC200-10 is generally used with low-viscosity fluid, and causes a reduction of response time. Silicone DC704 is used for vacuum and absolute pressure measurements. For high-temperature use in process measurement transmitters with reduced response time, silicone Slytherm 800 is ideal, while low-temperature silicone may be used in very cold applications.

Fluorocarbon works with any device used on an oxygen or chlorinated circuit (P max. 160 bar). For glycerin plus water, use paint without silicone or vacuum. Finally, use paraffin oil for sanitary purposes; it is FDA-approved.

Feel Confident in Your Decision

Once you choose the right diaphragm seal fill fluid for your particular process, you’ll feel more confident that your investment in your pressure instruments is secure. As always, ESP is happy to provide data-driven guidance to assist with your selection, but the most important thing to bear in mind is that the type of fluid you select will be based on your specific requirements. Make your seal fill fluid choice with confidence, knowing that it will work correctly in conjunction with the use of a high-quality diaphragm seal from ESP.

Why Choose ESP for Your Diaphragm Seals?

ESP is the perfect choice when you need to purchase diaphragm seals. We understand that availability is a major consideration when purchasing seals, and are proud to say that we ship dry Bourdon diaphragm seals within 2 days, for your convenience. Our company also ships assembled Bourdon diaphragm seals in 5 days. Best of all, we charge no expediting fees. You’ll enjoy the prompt shipping you deserve without paying extra it for it.

We get you your parts when you need them, addressing your needs through superb customer service. You’ll enjoy same-day response times and order processing, so that you can continue to focus on what matters most. We pride ourselves on rapid part development while maintaining the high standards of quality that are the foundation of our business.

Competitive Costs, Impeccable Quality

In addition to our strong focus on availability, ESP keeps prices competitive while maintaining top quality. Our products are designed for process industries. The quality they offer is both reliable and repeatable. When you invest our diaphragm seals, you can rest assured that you are making a smart investment that will pay dividends for years to come.

Exceptional Service at Every Stage of the Sale

Please know that when you work with ESP, we’ll do more than sell you a diaphragm seal; our team will provide complete pre-sale support, offering detailed product advice based on hard data. You’ll gain a comprehensive understanding of the benefits and potential applications of our seal products, enabling you to make an informed decision. We will respond to your inquiries on the same day, understanding that every minute matters when it comes to your business.

During the sale, our team will always treat you with the utmost respect and courtesy, making sure that you are aware of all pricing and shipping information. You deserve to understand every aspect of your purchase and we will gladly provide you with the details you need.

Following the sale, our commitment to serving you continues. We provide attentive post-sale support, making sure that our diaphragm seals are everything you expect them to be. We value great customer service, and we maintain that focus long after we’ve sold and shipped your diaphragm seal. When you’re looking for diaphragm seals for sale, you cannot go wrong with ESP. Contact us today to learn more.

Common Oversights

In many cases, diaphragm seal troubleshooting can seem complicated. With so many factors to review, you may find it difficult to identify the oversight that led to a given result. Fortunately, there are some common problem-causing issues that are relatively easy to solve.

It is very important to ensure that the connections between seal and gauge are the same size and type. This is a very common oversight and it causes unnecessary compatibility issues that may result in lost time and profit. Similarly, you must make certain that your diaphragm seal is the right size for the specified instrument. No matter your industry, it is essential that your seal match your pressure instrument exactly. Otherwise, it simply will not work.

When using a capillary with a diaphragm seal, certain oversights can result in a range of issues. For example, in some cases, a capillary with a gauge may need access to an adjustable pointer. In other instances, a capillary with a gauge might require a certain method to mount the gauge. Ensure that you are prepared for these examples to avoid problematic situations related to capillary use.

Other Issues

Other potential diaphragm seal oversights include:

  • Small Pressure Span Gauge with Crimped Window
  • A glycerin and water mix
  • Water System Fill Fluid is Specified for Vacuum or Compound Ranges The aforementioned items are typical examples of additional common oversights and may not be representative of your specific issue. Working with ESP to complete your order will help you to avoid these issues. You know your specific needs and we know what products will fulfill them the right way. You can always expect us to provide you with the correct answer the first time you ask us, as we draw upon deep experience in our field. Working together, we can easily avoid oversights related to the use of diaphragm seals and capillaries.

When you do have a question for us, please remember that we are always happy to provide data related to diaphragm seal and fill fluid usage. As part of our complete approach to customer service, we assist you before, during, and after the sale, addressing these types of issues throughout the sale process. As our valued customer, it’s what you deserve. Please feel free to each out to ESP with any additional inquiries regarding common diaphragm seal oversights, along with any other questions or concerns.

What are Capillaries?

There are many reasons to think about using capillaries with diaphragm seals. Before considering them, it’s important to understand the role that a capillary plays. Capillaries are used for mounting pressure gauges, transmitters, and switches away from the tank or pipe. This may be done for several reasons. You might wish to mount your pressure instrument in an area with good visibility, like an instrument panel. In other cases, it may be necessary to reduce instrument pulsation.

Capillaries are also used to separate instruments from very hot or cold temperatures. The level of temperature reduction they provide is condition-dependent and varies. Make sure you have the right capillary for your requirements by working with the knowledgeable team at ESP. Various product options are available, including degreasing for oxygen applications.

What to Know Before Using a Capillary

Please note that capillaries will affect the response time of your assembly. Specifically, the length and diameter of the capillary causes such an effect, in conjunction with system fill fluid, temperature, pressure, and instrument-displaced volume.

In addition to mounting pressure instruments, capillaries may be used between measuring instruments and diaphragm seals. There are several types of capillaries available for use in various industries and applications. Capillaries come in a range of lengths and with different process connections, so you can find the perfect one for your setup. No matter what you plan to use your capillary for, it is essential to conduct thorough research before ordering.

Capillary Protection

Capillary armor plays an important protective role. It is strongly recommend to use capillary armor in all applications if possible. There are many types of armor available. SS interlocking is the most common, while polyethylene white tube armor is the second most commonly used. Other options include SS reinforced woven and PVC black coating. As with the capillary itself, the type of armor used must be based on application requirements.

Use of capillary protection will ensure your peace of mind, protecting your instruments from potential failure. For assistance choosing the right armor, speak with the professionals at ESP. Once you explain your desired application, we will provide you with data relevant to your selection of armor and other capillary options. Getting the initial order right will ensure the smooth operation of your pressure instruments.

Mounting a Diaphragm Seal

When mounting a diaphragm seal, it is essential to pick the right option for your application. Diaphragm seals play an important role in protecting pressure instrument sensors from dangerous process media. Making sure they are mounted correctly is essential to ensuring they fulfill that role. Before ordering, you should make certain that the mounting method you choose is the right one.

There are several methods for mounting a diaphragm seal. First, they can be mounted using a capillary. This usage is restricted by the system fill fluid limit. Secondly, they can be directly mounted. This method is recommended only for temperatures up to 150 degrees Celsius, or 302 degrees Fahrenheit. Finally, you can mount diaphragm seals with cooling adapters, up to the system fill fluid limit. This method allows for temperature reduction. In each of these cases, the process connection, seal type, and material may differ.

Direct Mounting

Direct-mounted diaphragm seals may be attached to mechanical pressure gauges, switches, and transmitters. In this case, a flanged, threaded, or sanitary process connection may be used. It is important to understand the type of process connection you need before ordering. A direct mount may be ideal in certain circumstances; in other instances, use of a capillary or cooling adapter may be ideal. Ensure your mounting method matches the process connection, diaphragm seal type, and application requirements.

Capillary Mounting

Several types of diaphragm seals feature process connections that are perfect for capillary mounting. Capillaries offer the advantage of remote mounting; the reasons you may need this type of setup are entirely specific to your facility’s layout and the demands of your application. When using the capillary method, it is very important that you choose a capillary armor to protect the line. There are many protection types available, and ESP will gladly provide you with additional assistance with option selection.

Cooling Adapter Mounting

Cooling adapters are used to keep pressure instruments from being negatively affected by high temperatures. Placed between the diaphragm seal and the measuring instrument, these adapters deliver significant temperature reduction. Various types are available, with a range of connection types and maximum temperatures.

Support for Your Mounting Process

Whether you need to use direct, capillary, or cooling adapter mounting, the team at ESP is here to help. We have detailed information available regarding diaphragm seal mounting and related product options. Our comprehensive selection of diaphragm seals, with their various process connections, ensures that mounting the right seal for your application will be straightforward.