WIKA USA has a long history of partnering with customers in the process industry to troubleshoot and resolve common issues with traditional diaphragm seals.

The process industry relies on diaphragm seals to protect sensitive pressure instruments, keep media uncontaminated, and make system monitoring more reliable. However, traditional seals have their share of issues.

WIKA USA has decades of experience identifying diaphragm seal problems and solving them. Here are some of the top questions that we’ve received over the years.

Diaphragm Seal Issue #1: Loose bolts

Problem: My thermal cycling applications causes vibration and pulsation, which means that clamping bolts sometimes work themselves loose.

Solution: Try switching to our All-Welded System (AWS) model M93X.D1. The upper and lower housings of the diaphragm seal body are clean-welded together; this eliminates the need for clamping bolts and is considered tamper-proof. As a bonus, without the need for traditional hardware, the assembly takes up less space.

The XSEL® industrial process gauge is also permanently welded to the upper portion of seal body and will not separate, even under heavy vibration and pulsation. Furthermore, the AWS is designed as a drop-in retrofit for most existing gauges, making replacements extremely easy.

Diaphragm Seal Issue #2: Incompatibility with process media

Problem: It turns out that the O-rings and gaskets in my diaphragm seal are not compatible with the process media.

Solution: Rather than trying to find elastomers that are compatible, get rid of them altogether in your pressure instruments. The diaphragm in WIKA’s AWS is recessed from the process media and welded to the seal body using a TIG (tungsten inert gas) weld technique. By eliminating the need for O-rings and gaskets, you eliminate process compatibility issues. There’s also the additional benefit of increasing the pressure instrument’s upper temperature limits while maintaining material compatibility between the lower body and the diaphragm.

Diaphragm Seal Issue #3: Poor thread contact

Problem: The thread contact between my pressure gauge and diaphragm seal changes in extreme temperatures, heavy vibration, and during installation and orientation.

Solution: In the AWS, the threads of the stainless steel process gauge are welded to the upper housing of the diaphragm seal body. This back weld is fully resistant to thermal cycling, vibration, and incorrect installation, and there is always contact between the pressure gauge and the diaphragm seal. This also eliminates a potential leak point and makes the entire assembly tamper proof.

Besides more reliable pressure readings, welded threads mean that gases or system fill fluid cannot escape through the threads – a common issue with NPT connections. In addition, because the gauge is permanently welded to the diaphragm seal, the AWS qualifies as a dual-containment system.

The AWS: Two innovative products welded into one

To create the AWS, we took two of our highest-performance instruments and expertly welded them together into one exceptionally reliable system.

Models M932.D1, M933.D1

All-Welded System (AWS)

The 23X.34 XSEL® process gauge is expressly designed for demanding conditions in the process industry:

  • Stainless steel movement and socket to withstand corrosive environments.
  • Fiberglass-reinforced thermoplastic (POCAN) case for excellent load-cycle stability and shock resistance.
  • Pressure measurement from vacuum to 10,000 psi (690 bar) in combination with an AWS.
  • Movement with a built-in 50% over-range protection with no loss of accuracy.
  • A choice of liquid case filling for applications with high dynamic pressure loads and vibrations, and to protect gauges from environmental ingress.
  • Standard equipped with a threaded restrictor to reduce the impact from pressure spikes and high dynamic pressure cycles.
  • Fully traceable assembly with order and material information engraved on the gauge.
  • Approval requirements and certificates (EU, Canada, CIS countries) upon request.

The other half of the assembly is the model 990.34 diaphragm seal with welded design. It is made to withstand corrosive, hot, or viscous media. The measuring range of the seal is between 15 psi and 10,000 psi. The diaphragm, lower housing, and upper housing come standard in stainless steel, with the option for Monel or Hastelloy.

WIKA’s All-Welded System is the solution for many diaphragm seal issues. Our pressure professionals are also well-versed in diagnosing and resolving a variety of pressure gauge failures. Contact us for more information.

Products mentioned in this blog:
23X.34 XSEL® process gauge
• 990.34 diaphragm seal with welded design


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