Feature sponsored by Test & measurement
Tackling the issue
of hydrogen permeation in
pressure transmitters
Pressure transmitter with H-Shield coating to tackle hydrogen permeation
within designated parameters. Pressure transmitters are extremely durable and successfully operate in some of the most challenging environments on the planet, helping production processes to run effectively. The actual mechanism of the pressure measurement is explained by Pascal’s Law, which states that when an external pressure is applied to any confined fluid at rest, the pressure is increased at every point in the fluid by the amount of that external pressure. According to Pascal’s Law, the fill fluid inside the primary element will reach the same pressure as that applied against the isolation diaphragm(s). The fill fluid hydraulically conveys this pressure to the sensor, which produces an appropriate output signal. Pressure transmitters are set for a period of
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growth in the short to medium term. According to Data Bridge Market Research the pressure transmitter market is expected to witness market growth at a rate of 3.86 per cent between 2021 to 2028 and is expected to reach $3.82 billion by 2028. The increase in industrial automation, demand for multivariable pressure transmitters, and the industrialisation of developing countries,
Pressure transmitters play a key role in ensuring efficient and safe operations across a number of industries. Jon Davison, product manager temperature and pressure, UK & Ireland at ABB provides guidance on a phenomenon called hydrogen permeation, a major cause of pressure transmitter failure. The article provides insight on processes more susceptible to the phenomenon, signs to look out for which may indicate the presence of hydrogen permeation, as well as advice on how to address the issue.
ressure transmitters are used to measure the pressure of fluids, gases, and liquids in process industries. They are used in a wide range of industrial equipment to ensure machinery is operating
are key factors to supporting this growth. And yet, while pressure transmitters play a key role in optimising operations, all too often their performance can be compromised.
WHY TRANSMITTERS FAIL? There are a number of reasons why the performance of a transmitter can be compromised. These include:
the wrong type of transmitter being used for the application/environment
poor maintenance
shocks and vibrations outside of the operating parameters of the transmitter
extreme pressure spikes being exposed to extreme temperatures incorrect turndown ratio water contamination However, one of the common causes of pressure
transmitter failures is hydrogen permeation, a phenomenon that is not that well understood. Hydrogen is the smallest element on the periodic table, and in nature it is normally found in a diatomic
Pressure transmitters affected by hydrogen permeation suffer reduced accuracy and can fail
state (H2), with a single molecule comprised of two hydrogen atoms. Hydrogen is the most common
element in the universe and is found in many compounds including water and acids. While hydrogen in its normal state does not cause corrosion, it can cause a measurement related problem in pressure transmitters under certain circumstances if the wetted diaphragms are not protected against the ingress of hydrogen (commonly known as hydrogen permeation).
WHAT IS HYDROGEN PERMEATION? In its normal diatomic state, a hydrogen molecule will not be able to pass through a pressure transmitter diaphragm. Problems occur where conditions cause the molecule to split into two hydrogen ions, which are small enough to penetrate the molecular structure of the
September 2022 Instrumentation Monthly
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