SIPERM® R

Material basis and positioning

SIPERM® R is a porous sintered material made of stainless steel 1.4404 (AISI 316L) that has been developed for industrial applications in which defined flow, pressure or filter properties must be maintained under demanding conditions. The material is produced by sintering stainless steel powders, which are processed in controlled grain fractions and press densities. During the thermal process, the metal particles bond together permanently, creating a stable structure in which an open pore network is formed.

The structure differs fundamentally from wire mesh, perforated sheets or polymeric filter materials. While these materials form flow paths via individual openings or fibers, SIPERM® R creates a three-dimensionally cross-linked pore space that is uniform across the entire wall thickness. The porosity is not a side effect of production, but a specifically set material parameter. The resulting characteristic values – pore size, permeability, pressure loss – are reproducible and determined in accordance with standards.

SIPERM® R is used wherever materials are required that are simultaneously porous, mechanically stable and thermally resilient. Typical areas of application range from process, measurement and safety technology to flow-guiding functional surfaces. The central role of the material is to guide, dampen or distribute flows – under conditions where conventional filter media would fail.

Microstructure and characteristics of the pore network

The characteristic feature of SIPERM® R is the continuous pore structure. The pores are created when the individual particles fuse at their contact points during the sintering process, while the spaces in between remain as a defined cavity structure.

Distribution and size of the pores

Depending on the selected material quality, the pore sizes range from around 1 to 200 µm. The exact distribution is defined by the grain size used and the press density. The test methods follow DIN ISO 4022 for permeability and DIN ISO 4003 for bubble point measurements.

These parameters make it possible to calculate flow paths, pressure losses and retention levels in advance. The homogeneity across the material surface prevents local constrictions or “hotspots”, which can occur with woven structures.

Open porosity as a functional principle

The structure allows a uniform flow in any direction, provided the component geometry permits this. The open structure fulfills several functions simultaneously:

• Transportation and distribution of the medium
• Controlled pressure reduction
• Flow calming
• Defined particle retention
• Energy conversion through friction in the duct structure

This multifunctionality is a key unique selling point of porous sintered materials compared to one-dimensional or two-dimensional filter systems.

Flow behavior of SIPERM® R

The flow characteristics of SIPERM® R are made up of laminar-dominated and turbulent components. The specific coefficients are material-specific and are available separately for each porosity quality. This means that the flow behavior can not only be observed empirically, but can also be planned technically.

Laminar flow

At low flow velocities, the movement of the medium is predominantly laminar. The pressure loss increases proportionally to the volume flow, which enables precise prediction. This property is important for applications where a stable flow profile is required.

Turbulent flow

As the flow rate increases, the turbulent proportion in the pore system grows. As the flow in the branched channels is repeatedly accelerated, decelerated and deflected, the pressure loss in this area increases disproportionately. This effect is already taken into account in the material characteristic value and can be used for technical calculations.

Flow stabilization as a material function

Thanks to the network of microchannels, SIPERM® R acts as a natural flow damper. Local pressure peaks are reduced, the speed of the medium is homogenized and uneven flow fields are smoothed out. This is precisely one of the key advantages of the material: it enables reproducible process conditions, even if external factors fluctuate.

Mechanical properties and strength behavior

Despite its porosity, SIPERM® R is characterized by high mechanical stability. The metallic bonds that are formed during sintering create a load-bearing structure in which the strength is not only derived from the material matrix itself, but also from the large number of contact points between the stainless steel particles. The strength characteristics – including tensile strength, bending strength and shear strength – are documented for each specific material and form the basis for the structural design.

Mechanical stability is particularly relevant when components are used under differential pressure or mechanical loads. SIPERM® R is used in applications where pressure differences occur that would overtax conventional porous materials. The robustness of the material also allows it to be used in oscillation and vibration environments without the pore structure collapsing or changing significantly.

The strength depends on the degree of porosity: finer grades have a higher material density and therefore higher strength values, while coarser grades offer higher permeability but have lower mechanical properties. This correlation is essential for design decisions and must be taken into account for wall thicknesses, surface design and pressure loads.

Thermal behavior and temperature resistance

The base material stainless steel 1.4404 gives SIPERM® R high temperature stability. The material can be used reliably in oxidizing atmospheres up to 500 °C and in reducing atmospheres up to 650 °C without affecting the microstructure or function.

In this temperature range, the pore structure remains completely intact. Unlike polymer-based filters or fibrous structures, the sintered metal structure does not undergo thermal softening or structural shrinkage. This represents a significant technical advantage, as many applications – such as process gas routing, venting or flow control – operate under high thermal loads.

Even rapid temperature changes do not cause the structure to fail. Due to the homogeneous metal matrix and uniform pore distribution, no local stresses occur that could jeopardize the mechanical integrity. This makes SIPERM® R suitable for thermally cyclical processes.

Chemical resistance and media compatibility

The material inherits the chemical resistance of stainless steel 1.4404. This means that SIPERM® R remains stable in numerous industrial media, including:

• Many solvents
• Process gases
• organic substances
• Weak acids and bases

However, the large inner surface of the material leads to a stronger interaction with media than with solid stainless steel. This means that cleaning conditions and exposure times must be controlled particularly precisely.

In the case of chemically aggressive media or high concentrations, the design must be carried out with appropriate care. Under typical industrial process conditions, however, SIPERM® R offers stable and permanent chemical resistance.

Processing properties and structural integration

Despite its porosity, SIPERM® R is a machinable metallic material. Machinability depends on the porosity selected, as finer grades offer more material contact and more stable cutting conditions.

Mechanical processing

• Rolling, bending, pressing and embossing are possible.
• Machining may only be carried out on areas where there is no air flow, so as not to close pores.
• Water jet cutting and spark erosion are the preferred processes for contour-accurate cuts.

Connection technology

SIPERM® R can be joined to solid stainless steel parts using TIG welding. A low heat input is important in order to avoid local compaction of the pore space.

These joining techniques enable functional components in which porous and solid zones are combined – such as flow surfaces, sensor connections or components for pressure areas.

Cleaning and maintaining functionality

The porous structure of SIPERM® R has a large internal surface area, which is crucial for its functionality, but can also lead to deposits within the pores. Cleanability is therefore a key aspect for long-term operation. The material can be reliably cleaned using several methods, provided these are correctly matched to the medium and the degree of contamination.

Mechanical cleaning

Mechanical counterflow cleaning is the preferred method for surface or loosely bound particles. A suitable gas or liquid is passed through the component in the opposite direction to the operating flow in order to remove deposits. This can often be carried out without removing the component and is suitable for regular maintenance intervals.

Thermal or physical cleaning

Superheated steam treatment and – if the component can be removed – ultrasonic cleaning loosen particles that have settled deeper in the pore system. The physical processes do not affect the material structure, but require a controlled procedure in order to avoid thermal overloads or incomplete drying.

Dry cleaning

Chemical cleaning agents such as alcohols, acetone or diluted acids can be used if inorganic or organic residues adhere more strongly. Due to the high internal surface area, however, it is necessary to precisely limit the exposure time. After each chemical cleaning, complete rinsing and drying is essential to ensure that no residues remain in the pore system.

The combination of different cleaning processes generally enables complete restoration of permeability. This makes SIPERM® R a material that can be used in the long term and whose functional properties remain stable over many operating cycles.

Functional advantages in an industrial environment

SIPERM® R is used in technical applications where a combination of flow control, mechanical stability and thermal resistance is required. The porous structure offers several functional advantages that cannot be achieved in this form by alternative materials.

Reproducible flow parameters

The clearly defined pore sizes and flow coefficients enable the precise calculation of pressure losses and volume flows. The material behaves reproducibly, even with temperature or load changes.

Homogeneous media routing

The cross-linked pore structure distributes the medium evenly over the entire surface. Flow inhomogeneities are reduced, which stabilizes sensitive processes.

High mechanical and thermal robustness

In contrast to fibrous or polymeric filter materials, SIPERM® R remains dimensionally and functionally stable even at high temperatures. The metal matrix reliably withstands mechanical vibrations, pressure surges and cyclical loads.

Process reliability through defined porosity

The pore size determines the retention behavior, the flow coefficients determine the pressure loss behavior – both variables are defined and measurable. This allows the material to be specifically designed for safety-relevant processes.

Long-term usability

Thanks to its cleanability and structural stability, it retains its functionality for years. The material does not need to be replaced frequently, which offers both technical and economic advantages.

Summary

SIPERM® R is a porous stainless steel material manufactured with technical precision that is characterized by a combination of reproducible porosity, high mechanical stability, thermal resilience and chemical resistance. The continuous pore network enables defined flow and filter properties that behave reliably under all operating conditions.

The mechanical properties allow use in pressurized or dynamic systems, while the temperature resistance enables applications in high-temperature or thermally cyclical processes. The chemical resistance and good cleanability ensure a long service life of the material – a significant advantage over non-metallic filter systems.

The combination of these properties makes SIPERM® R a material that is used as a functional element in many industrial sectors when media with defined parameters need to be guided, calmed, distributed or retained. The technical characteristics enable precise design and the versatility of the material allows it to be integrated into a wide range of system concepts and process environments.