Hydrogen Diagnostics

Hydrogen diagnostics is a modern, highly sensitive, and safe method for detecting leaks in plate heat exchangers. It uses a mixture of hydrogen (H₂) and nitrogen (N₂), known as forming gas, which is non-flammable, non-explosive, and complies with ISO 10156 safety standards.

Method Principle:

• The plate heat exchanger is filled with test gas (typically 10% H₂ and 90% N₂) on either the primary or secondary circuit side.
• On the opposite side of the exchanger, where non-pressurized air circulates, a hydrogen detector monitors the presence of hydrogen molecules.
• Thanks to the extremely small size of the H₂ molecule, even microscopic leaks can be detected that often escape other methods.

Method Advantages:

• High sensitivity – leak detection down to 10⁻⁶ mbar∙l/s.
• Safety – non-flammable mixture, suitable for work in enclosed or operational areas.
• Speed and precision – immediate results with accurate leak localization.
• Non-destructive – gentle method, suitable even for sensitive technologies.

Typical Applications:

• Leak diagnostics in food, pharmaceutical, energy, or chemical industries.
• Leak testing after overhauls or exchanger servicing.
• Prevention of cross-contamination between media (e.g., water/steam, water/refrigerant, CIP media/food).

Functional Description of the Leak Test

Before performing the test, the heat exchanger must be cleaned, disconnected from piping connections, and drained. Cleaning prior to the test is carried out by the customer, for example using a CIP station. Draining the exchanger is done by blowing compressed air into both the primary and secondary sides so that most of the contained medium is expelled.

The next step is to seal all inlets and outlets of the heat exchanger using special sealing covers. The primary side is then pressurized with the test gas (a mixture of hydrogen and nitrogen), according to the permissible operating pressures of individual plate or shell-and-tube heat exchangers. The secondary side remains unpressurized, with air circulating through it. This air circuit includes a membrane compressor, which keeps the air moving, and a measuring point where samples are taken.

If the unit has any damage (cracks, corrosion, etc.), hydrogen molecules may pass through from the normally separated primary side to the secondary side, carried along by the airflow to the measuring point. There, they are detected by the sensor and displayed on the measuring device as an H₂ concentration = inter-sectional (internal) leakage.

Leak Test Breakdown

The process of testing a heat exchanger consists of two separate parts:

1. Detection of internal (inter-sectional) leakage, i.e., potential damage to heat transfer plates or tubes. Depending on the size of the unit, this takes about 2 hours per section. To achieve a clear result, at least 3 measurements are performed, with the interval between measurements depending on the volume of the respective section (exchanger).
2. Detection of external leakage, i.e., potential damage to gaskets, heat transfer plates, or tubes, or leaks caused by insufficient tightening of the exchanger. This takes approx. 30 minutes. It is performed by moving the sensor along the surface of the unit. Possible leaks or faults are detected by the sensor with pinpoint accuracy, and defective spots are immediately located and marked (e.g., with colored tape).

Properties of Hydrogen

• Smallest molecule in the world
• Lightest molecule in the world
• Very low viscosity
• Low concentration in the environment (0.5 ppm)
• Environmentally friendly
• Cheapest tracer gas (approx. 1/4 the cost of helium)
• Non-toxic
• Non-corrosive
• Approved for food use (E 949)

General Requirements for the Food Industry

The requirements of international retail chains increasingly force manufacturers to implement high accreditation standards such as IFS (International Food Standard). Manufacturers must be able to supply products that are safe from a physical, chemical, and biological perspective throughout the entire production chain. The foundation of the control system should be a systematic and comprehensive HACCP plan (Hazard Analysis and Critical Control Point), which is based on Hygiene Regulation (EC) No. 852/2004 – general rules on food hygiene.