Hastelloy Pressure Transducers

• When it comes to pressure transducers, there are tons are choices and configurations to choose from, which can be daunting.
• While stainless steel is often a great choice, but when working with corrosive liquids, something more rugged, such as Hastelloy may be a better choice.
• Core Sensors manufacturers a wide-range of Hastelloy pressure transducers for a variety of applications.

When configuring a pressure transducer for your application, there are a lot of factors to consider. One question you will likely hear is: “What is the media that will be making contact with the pressure transducer?” While it may seem like a simple question, it is a very important one. For instance, what’s the difference between Hastelloy pressure transducers compared to other materials like stainless steel?

For the majority of applications that we encounter, 316L stainless steel is a fine choice. Stainless steel is common for use in applications requiring mild corrosion resistance. This would include applications that come in contact with water, oils, lubricants, utility grade natural gas, mild acids, and hydrogen service. While 316L SS does offer good corrosion resistance, there are medias that will quickly corrode 316L SS. And this corrosion will compromise the structural integrity of the pressure transducer’s diaphragm. In these applications, Core Sensors provides pressure transducers with Hastelloy C-276 superalloy.

What are Hastelloy Pressure Transducers?

Hastelloy C-276 (UNS N10276) is a super nickel-molybdenum-chromium alloy that offers high corrosion resistance in oxidizing and reducing environments. It exhibits excellent resistance to Sulfide Stress Cracking (SSC) and Stress Corrosion Cracking (SCC). This is due to its high molybdenum and chromium content, in addition to its 3.0-4.5% Tungsten content. Hastelloy C-276 is a NACE MR0175 / ISO 15156 compliant material for use in the oil and gas production industry.

Applications where Hastelloy pressure transducers are most ideal include:

• oil and gas production – sour gas (high H2S content)
• seawater – exceptional crevice corrosion resistance
• pollution control – desulfurization systems
• wet chloride gas
• chemical processing plants
• hypochlorite

Low Pressure Measurement in Corrosive Applications

Monitoring low pressures in corrosive applications is a difficult task. And the large availability of corrosion resistant pressure transducers on the market can make for a tough choice. Two common recommendations for low pressure corrosive measurement are:

1. Diaphragm Seals
   • The Downside – In order to properly transmit pressure to the diaphragm seal, there needs to be enough displacement from the transfer fluid to the diaphragm of the pressure transducer. As a general rule of thumb, the smaller the pressure range, the larger the diaphragm seal needs to be. It is not uncommon to see a 1.5″ diaphragm seal for pressures below 15 PSI.
2. Ceramic Diaphragms
   • The Downside – Ceramic is highly corrosion resistant. However, an elastomer seal is necessary to attach it to the body of the pressure transducer. This elastomer is commonly overlooked when determining media compatibility. As a result, incorrect compatibility with the elastomer seal can cause swelling, cracking, and/or leaking of the process media.

Using Hastelloy Pressure Transducers in Corrosive Applications

In an effort to simplify low pressure measurements in corrosive environments, we offer Hastelloy C-276 material in a media isolated package. An oil-filled sensor element is precision welded to the process connection threads without the use of O-rings or other sealing materials. This ensures that the corrosive media is only making contact with the materials of the sensing element and threads. With this sensing method, we are able to offer pressure ranges down to 1 PSI and up to 30 PSI in a small package. Most commonly, these configurations feature 1/4″ Male NPT threads.

We offer two types of material construction in low pressure designs:

1. Hastelloy C-276 diaphragm + 316L SS process connection threads
   • With a thickness of 1 to 1.5 mils, the diaphragm is the thinnest component of the transducer. As a result, it is most susceptible to corroding in harsh environments. When working with medias that cause minor corrosion to standard austenitic stainless steels, selecting a Hastelloy C-276 diaphragm with 316L SS threads is an economical choice. In doing so, the Hastelloy C-276 material will prevent the thin diaphragm from corroding. Additionally, while the 316L SS threads will show signs of surface corrosion, the structural integrity will remain intact.
   • For applications where both corrosive media and clogging is a concern, we offer a Hastelloy C-276 flush diaphragm with 1/2″ Male NPT threads in 316L SS.
2. All Hastelloy C-276 wetted material (diaphragm + process connection threads)
   • When working with medias that are extremely corrosive to standard austenitic stainless steels, we offer an all Hastelloy C-276 solution.

Medium to High Pressure Measurement in Corrosive Applications

For medium to high pressure applications, we utilize a high strength solid piece of Hastelloy C-276. This Hastelloy is free of fluid-filled cavities, sealing materials such as o-rings, and weld joints. This solid piece of Hastelloy contains the corrosive media within the pressure port. In doing so, it reduces or completely eliminates the corrosion that is common when using standard austenitic stainless steels. For applications where standard tapered threads and Teflon tape are not ideal, we can offer straight threads (i.e. SAE 4) with a flare. As a result, this creates a metal-to-metal seal and eliminates the need for an elastomer seal. Pressure ranges from 50 PSI up to 10,000 PSI are available.