GASKET SOLUTIONS FOR ELECTROLYZERS – AN OVERVIEW

Electrolysis seals play an important role in the chemical industry and are used to seal liquids and gases in electrolysis cells. A good seal is critical to the performance and reliability of the electrolysis process, ensuring that no unwanted substances enter the system and that the correct amount of liquid and gas flows through the cell. This article explains the most important aspects of seal geometries, materials for electrolytic seals and required equipment.


INTRODUCTION
Electrolysis seals play an important role in the chemical industry. They are used to reliably seal liquids and gases in electrolysis cells Pitschak et al. (2017). A good seal is of great importance for the performance of the electrolysis process. It ensures that no unwanted substances enter the system and that the right amount of liquid and gas flows through the cell. Loadman (2012) This article focuses on the key aspects of injection moulding tools, sealing geometries and materials used in electrolysis seals. The correct selection of these components is crucial to achieve an effective seal and ensure optimal functionality of the electrolysis system. A through consideration of these aspects enables manufacturers and engineers to develop and apply the best solutions for electrolysis seals.

SUCCESS FACTORS FOR AN ELECTROLYSIS SEAL
The main task of an electrolytic seal is to seal the contact surfaces of the assembly. For this, it is important that there is no relative movement between the components.
To achieve this goal, it is important to look at the process as a whole.  Figure 1 shows that the success factors of an optimally functioning electrolytic seal are an interplay of the factor's geometry, material, injection mould, and the production process.

MATERIAL
When sealing gases and liquids in electrolysis, we face a number of challenges. An effective electrolysis seal must be able to provide gas tightness and pressure resistance. It is important to avoid leaks and prevent gas leakage to ensure efficient and safe electrolysis.
One way to overcome these challenges is to choose the right sealing material. EPDM (ethylene propylene diene (monomer) rubber) is a proven material used in many electrolysis applications. EPDM offers excellent chemical resistance to a wide range of substances and is relatively stable at elevated temperatures Loadman (2012) This material is well suited for general sealing requirements in electrolysis.
For more demanding applications, for example in environments with acids, a fluororubber (FKM) compound can be used as a sealing material. FKM is a high-tech material known for its outstanding chemical resistance. It can withstand even aggressive chemicals and offers very high temperature and pressure resistance. The use of FKM seals can be an effective solution when dealing with extreme conditions and demanding environments in electrolysis. Loadman (2012) In order to minimise gas bubble formation and leaks, not only the right material but also the right shape of the seal is crucial. The gasket geometry should be designed to allow optimal matching and pressure distribution between the components to be joined. Careful design and shaping can achieve an effective seal. Loadman (2012) Furthermore, regular inspection and maintenance of the electrolysis seals is of great importance. Wear or damage can occur over time and lead to leaks. Timely detection and maintenance of leaks or damaged seals is therefore crucial to ensure smooth operation of the electrolysis system.
Overall, the selection of the right sealing material and careful design of the sealing geometry is crucial to overcome the challenges of gas sealing and pressure resistance in electrolysis. By using materials such as EPDM or FKM and paying attention to the correct shaping, we can achieve a reliable and efficient seal that meets the requirements of electrolysis.

CHOICE OF THE APPROPRIATE GEOMETRY
O-ring and flat gaskets are often used as static seals that provide a reliable seal. Gronitzky (2017) However, additional sealing lips can provide a better seal at low forces and thus higher gas tightness and pressure resistance.
O-ring geometries are suitable when only a few plates are stacked on top of each other, because the force required for compression is very high Li (2023) Li (2023) In an electrolyzer, sometimes 100 or more plates are stacked on top of each other, all of which must be sealed together. In this task, O-ring seals are conceivable as a geometry for a sealing task, but are rather unsuitable, as a lot of pressure is required. NOK Foundation Coorperation (2015) A sensible alternative is to profile the seal, accordingly, as can be seen in Figure  3.   Figure 3 shows that the contact surface area increases significantly with compression. In this respect, the required forces increase accordingly when not only two plates, but perhaps 100 plates are pressed together. Nielson (2022) A corresponding approach to solving this problem is profiling to increase the contact surface pressing force, as shown here in Figure 3.

INJECTION MOULD AND SUITABLE PROCESS
Choosing the right injection moulding tools for electrolysis seals is crucial to producing a reliable seal. A key factor in tool selection is the tool steel as well as the surface finish of the tool, as these factors influence the shaping of the electrolysis seal and thus its performance.
When manufacturing electrolysis gaskets, it is important to select suitable gating points as they have a critical influence on the moulding. Du et al. (2023) The placement of the gating points allows for optimal distribution of the material during the injection moulding process.
Careful selection of gating points can improve the quality of the electrolysis seals by minimizing unwanted defects such as air pockets or material distortion.
In addition, factors such as the cooling of the mould should also be considered when selecting the injection moulding tool.  Combination of material and mould is a guarantee for function. Effective tempering is important to reduce cycle times and ensure uniform vulcanization of the electrolysis seal. In contrast, insufficient tempering can lead to uneven shrinkage and deformation of the seal, which can sometimes severely impair its performance.

SUMMARY AND OUTLOOK
In summary, the careful selection of the material, geometry, process sizing and injection moulding tool is of great importance for the production of reliable electrolysis seals. For the gasket, the appropriate material is necessary accordingly. A suitable geometry is also important. For the tooling, the right tool steel, the surface finish of the tool and the placement of the gating points are the critical factors to ensure optimal shaping and performance of the seals.
Only if the above-mentioned success factors are equally taken into account, then it can be guaranteed that the electrolysis seal will permanently fulfil its task.