The ultimate guide to filtration in the process industry

Welding spatter, gasket residues and fragments from worn valves. These may sound like minor issues, but for a sensitive flow meter or an expensive heat exchanger, it's the first step towards operational problems. 

Impurities that accumulate in a plate heat exchanger or pasteuriser often cause operational disruptions. With filtration, you eliminate the risk of breakdowns and make it possible to stick to a planned maintenance schedule. Whether space is tight or you need a robust barrier, there is a mechanical solution to suit your specific pipework. 

But for those responsible for plant design, it can be difficult to assess where and how best to implement filtration solutions. Which filter solution is best suited to your installation? And what about filter elements and mesh sizes? 

We’ll help you find out! 

Filtration is, of course, not the only factor ensuring trouble-free production, but with the right solution, you are well on your way to preventing the unforeseen disruptions that can occur in a process plant. Rather than viewing filtration as an isolated component, it should be seen as an investment in the stability of the entire process line. 

1. Protection of critical and expensive components: Pumps, flow meters and heat exchangers are not only expensive to purchase, but are also some of the most time-consuming components to repair in the event of a breakdown. By installing a correctly positioned filter, foreign particles are captured before they cause damage. This extends the service life of the components and reduces the need for emergency maintenance. 
2. Guaranteed product quality and safety: In food and pharmaceutical production, there is no margin for error, as foreign matter in the system means discarded batches. Filtration acts as an indispensable control mechanism, ensuring that only the desired, clean medium reaches the filling stage.  
3. Economic optimisation through reduced maintenance: By capturing particles in a filter, maintenance often becomes less extensive and more manageable. This can reduce the need for manual cleaning of larger and more complex components and make it easier to schedule maintenance as part of normal production rather than as an emergency intervention.

Theory is one thing, but the true value of filtration is demonstrated in the challenges that breweries, dairies and pharmaceutical companies face in their day-to-day operations. In the brewery, hop residues and malt particles can quickly become lodged in narrow channels and disrupt both flow and precise temperature control during wort cooling if they are not captured in time. 

In dairy operations, it's equally crucial to keep milk stones, wear particles and other impurities out of the pasteurisation unit so that hygiene is maintained and the heating surfaces are not subjected to unnecessary strain. 

In the pharmaceutical industry, the requirements are even stricter. Here, even microscopic particles are unacceptable, as they can compromise sterility and product safety. Filtration is therefore absolutely essential both in utility media such as clean steam and in process steps where CIP and SIP cycles must be carried out without risk of contamination. 

To achieve the right balance between protection and flow, the filter type must match your plant’s geometry and the specific system requirements. The market offers a myriad of filtration solutions, ranging from advanced membrane systems to simple mechanical filters. In this context, we focus on the latter and guide you through three practical mechanical filter types for piping: the Y-strainer, the L-strainer and screen gaskets. 

The Y-strainer is the technical standard when robustness and simplicity are paramount. It is designed with a streamlined shape that ensures reliable and cost-effective process protection in demanding environments. 

Choose the Y-strainer when: 

• You have long, straight pipe runs. 
• You work with media such as process water, CIP fluids, steam or other liquids and gases. 
• You want low pressure drop over the long term and a solution that can run stably in continuous operation. 
• You require flexible installation in existing pipework – both horizontally and vertically – with connections such as weld ends, clamps or DS/SMS fittings. 

The Y-strainer is manufactured from AISI 316L stainless steel, making it resistant to corrosion and water hammer. The internal flow direction ensures effective collection of impurities, and the available filter sizes of 1 mm, 0.5 mm and 0.25 mm make it possible to tailor the filter precisely to the equipment requiring protection. 

The L-strainer, also known as the angle filter, is the perfect solution for sanitary systems where hygiene, flow capacity and space optimisation are key requirements. As the strainer is designed at an angle, it also functions as a 90-degree pipe bend. You therefore get filtration and a change of direction in a single component, saving valuable space in your plant. 

Choose the L-strainer when: 

• You are working with low-viscosity media such as water, steam or liquid food and beverages, where high flow and low resistance are important. 
• Space is limited, e.g. in sanitary process lines, and the filter must be easy to inspect and clean. 
• You want a compact filter that fits directly into a male stud elbow in the pipework and can be supplied with, for example, weld ends, nuts or nipples in DS, SMS, DIN, ISO Clamp or DIN Clamp. 

The L-strainer is also manufactured in AISI 316L stainless steel with a smooth internal surface (Ra < 0.8 μm), which meets high hygiene requirements. If you choose a slotted filter insert, you can effectively reduce flow resistance by up to 75%. This gives you a significantly higher flow rate through the filter without increasing the filter size. It results in lower pressure drop, better utilisation of the pump’s capacity and the ability to handle larger volumes in the same space. 

Screen gaskets are the compact solution when there is absolutely no room for a traditional filter housing, but protection is still required right next to the sensitive process point. They combine sealing and filtration in a single, discreet component directly within the union. 

Choose union gaskets with a screens when: 

• You need a final line of defence immediately before sensitive components such as nozzles, valves or precision measuring equipment. 
• Space around the process equipment is very limited, and a separate filter housing is not a realistic option. 
• You want extra protection without altering the pipework. The filter gasket is retrofitted directly into existing unions for e.g. SMS, DIN, ISO or Mini-Clamp. 

The filter function is integrated directly into the gasket and therefore requires no extra installation space. The stainless steel filter mesh in AISI 316, combined with gasket materials such as EPDM, NBR or FKM, provides a hygienic solution suitable even for demanding media. The construction ensures effective capture of small internal particles immediately before the medium’s final point, where even small impurities can have a significant impact.

It may be tempting to choose the finest insert available, but in practice it's often better to start with a coarser one and work your way down. As a rule of thumb, a mesh size of around 0.5–1 mm provides good protection for pumps, valves and heat exchangers in many process plants, whilst finer grades in the 50–150 μm range are typically used when the focus is on product quality and particle control closer to the process. If you go much finer than that, the risk of frequent blockages and significant pressure drops increases, which can both strain the pumps and create unnecessary bottlenecks. 

The choice of material is just as important as the fineness. The gaskets must be able to withstand both the process medium, CIP routines and the temperatures to which the filter is exposed. Otherwise, the problem will simply move to the next stage of the plant. At the same time, a filter is only as good as the maintenance it receives. By monitoring the differential pressure across the filter, you can see when it starts to clog; a sustained pressure drop is a transparent signal that it's time for cleaning or replacement, before it affects the rest of the process. 

Would you like to know more about mesh sizes? Then take a look at this video, where we examine the issue in more detail based on our union gaskets with filters: 

Filtration in the process industry is not a self-sustaining process, but an active investment in your operational reliability. By choosing the right filter and accessories, you can minimise the risk of breakdowns and ensure consistent product quality across your entire production. 

Are you still unsure which mesh size or filter type is right for your production? 

You are always welcome to contact our specialists for a no-obligation chat about optimising your plant. Simply send us an email at inquiry@alfotech.eu or give us a call on +45 7020 0422. 

The Y-filter is the versatile standard solution for pipe connections where robust filtration and simple installation are required. It can be used in both horizontal and vertical installations and it's therefore the obvious choice when the filter needs to provide flexible, reliable protection for the system’s components. The L-filter, on the other hand, is designed for 90-degree elbows. This makes it particularly suitable for compact systems where space needs to be saved whilst avoiding extra fittings in the pipework. 

A screen gasket is the right choice when space around the process equipment is very limited and a separate filter housing is not a realistic option. It is a compact solution that can be retrofitted directly into existing unions, thereby providing extra protection without altering the piping system. 

Choosing the mesh size is about striking a balance between protection and flow. As a rule of thumb, the mesh size should be fine enough to capture the particles you want to keep out, but not so fine that it causes unnecessary pressure loss or the risk of clogging. 

Yes, filters made from AISI 316L stainless steel are suitable for most chemicals and for demanding process environments. This makes them suitable for use in plants where hygiene, operational reliability and ease of cleaning are key requirements. However, it's important that the gasket material is matched to the specific cleaning agents and temperatures in your process.