Video: 3 reasons to choose vacuum fittings

In a standard pressure system, a leak blows outwards. In a vacuum system, it's the other way round: here, the leak sucks inwards, drawing air, moisture and impurities into the process you’re working to keep clean and free from oxygen. That’s why the choice of fittings is not a mere afterthought but a crucial decision for the integrity of the entire system – for it's at the joints that a vacuum system either remains airtight or draws air in.

In our guide to vacuum technology in the process industry, we explored the physics behind negative pressure and the challenges that vacuum technology solves in the dairy, brewing and pharmaceutical sectors. Here, we go a step further and look at one of the most common types of joint.  Our Director of Sales & Marketing, Alexander Hold, explains what vacuum fittings are, where they’re used in the process industry, and why you should consider them for your production. Last but not least, he shows what a standard connection with vacuum flanges, vacuum clamping ring, and a vacuum centering ring looks like.

Vacuum fittings are the components that connect pumps, pipes and tanks in a closed vacuum system. They ensure the joints are airtight, so that the system can maintain the vacuum without drawing in air.

The underlying concept is the KF standard (Klein Flange). In practice, it functions as a quick-connect system for vacuum: two flanges, a centering ring with a gasket and a clamping ring that locks the whole assembly together by hand. No screws, no special tools – and at the same time full compatibility with the international standards DIN 28403 and ISO 2861.

In the process industry, you’ll encounter vacuum in three main areas:

• Evaporation: Gentle concentration of the medium at low pressure. Because the boiling point falls as the pressure drops, you can evaporate milk to produce, for example, condensed milk, or juice to produce concentrate at much lower temperatures than atmospheric pressure. In this way, you can preserve flavour, aroma and nutritional content.
• Degassing: Removal of dissolved oxygen from liquid media. In dairies, oxygen is removed from the milk prior to homogenization to slow down oxidation and foaming, and in breweries, oxygen is kept out of the beer during the sensitive flow prior to bottling, where even small amounts of oxygen would otherwise shorten the shelf life.
• Vacuum transport of various media: Efficient and sealed transport of various media, for example, dry materials such as flour and sugar in the food industry, and active pharmaceutical ingredients and additives in the pharmaceutical sector.

No screws. No spanners. No special tools. The KF coupling is locked with a wing nut on the clamping ring, so you can assemble and disassemble it by hand. It might look like this:

• In the dairy, you can dismantle the evaporation line quickly before CIP and have it reassembled shortly afterwards.
• In the brewery, this provides flexibility for conversions and replacements without lengthy stoppages.
• In the pharmaceutical industry, you can reconfigure the plant between batches without the line being blocked for long periods.

Therefore, vacuum fittings are not just individual components, but a system designed to be assembled and disassembled time and time again. It sounds easy, and it is. In practice, it's time you save every single day. 

A vacuum assembly usually consists of three parts: a vacuum flange (one at each end), a vacuum centering ring with a gasket, and a vacuum clamping ring. Together, they form a mechanically locked connection, where the gasket is pressed between the flanges and seals tightly, ensuring that the vacuum is maintained.

The choice of material determines how well the joint withstands the medium. The flanges, which comply with the DIN 28403 and ISO 2861 standards, are manufactured from AISI 316L stainless steel for high corrosion resistance.

You select the gasket based on the medium and temperature; NBR is a robust all-round choice, whilst Viton (FKM) offers excellent resistance to chemicals and high temperatures. With the correct gasket, the joint maintains a leak rate as low as approx. 10⁻⁷ mbar, making it suitable for use from rough to high vacuum. It simply doesn’t get any tighter than that.

Dead zones are the small pockets and crevices in a joint that cleaning can never quite reach. It's there that product residues and bacteria build up, and it's there that a sanitary line reveals its weak point.

The KF design has been specifically developed to avoid them. The gasket fits snugly, and the joint leaves no hidden gaps. This is why vacuum fittings are particularly well-suited for sanitary applications, for example:

• In dairies, for transporting dairy products between process stages.
• In breweries, to maintain sterile, oxygen-free conditions in the sensitive part of the production process.
• In the pharmaceutical industry, as a prerequisite for handling active ingredients in cleanrooms.

This is directly in line with one of the core challenges in vacuum production, which we addressed in our previous guide: keeping contamination out of the finished product.

Vacuum fittings are not limited to the standard assembly shown in the video. Our range is modular and designed so that you can shape the line to your plant – and this logic applies throughout. You lay the foundation with the flange, which ensures tight connections between pipes, valves and pumps. The centering ring with gasket acts as the heart of the seal itself, and the clamping ring mechanically locks the connection by hand using the wing nut. From there, you can adapt the line as required: a 90° elbow handles changes in direction in confined spaces without restricting flow, and a flange with concentric reduction changes diameter in a single smooth, conical transition rather than requiring an extra joint.

If the line needs extending, you can use a tee for branch lines and the integration of pressure gauges, sensors or an extra vacuum pump – or a tee with reduction, when the branch line also needs to change size. And should a port remain unused, you can seal it airtight with a blind flange.

The advantage is that the quick-connect principle applies not just to individual joints, but to the entire system. You can assemble, modify and extend the line without tools – and without changing standards along the way.

Before you make your choice, there are some key questions you should ask yourselves:

• What is being transported through the joint, and what does this require of the sealing material?
• How often do you dismantle the joints for CIP or modification?
• Does the plant need to comply with EHEDG, FDA or GMP?
• Do the new fittings need to be compatible with an existing plant that meets different standards?

If you're unsure about the answers, it's exactly where technical advice makes all the difference. We'll help you match fittings, gaskets and standards to your process – and, last but not least, integrate them with the other components of your vacuum system.

If you need help choosing the right vacuum fittings for your plant, please get in touch. Call us on +45 7020 0422 or send us an e-mail at inquiry@alfotech.eu, and we’ll find the solution together.

With the right materials, the KF joint is leak-tight down to around 10⁻⁷ mbar, which covers the vast majority of applications from low vacuum to high vacuum. However, the leak-tightness depends on the choice of gasket and on the flange surfaces being clean and undamaged. Thus, you should pay particular attention to the gasket every time you open the joint. If you’re unsure about the vacuum level in your process, we’d be happy to assess it with you.

Yes, in many cases. KF fittings comply with DIN 28403 and ISO 2861 and are designed to be compatible with the most widely used standards, so you rarely need to replace the entire line. This should always be assessed on a case-by-case basis, considering dimensions, pressure levels and the standards your current system complies with. Please feel free to send us an overview of the installation, and we’ll work out what’s compatible.

It depends on the medium, the temperature and the cleaning process. NBR is a robust all-round choice for most applications, whilst Viton (FKM) performs well against aggressive chemicals and high temperatures. The right choice depends on what flows through the joint and how you clean it. We’d be happy to advise you on the right combination for your process.

Yes, provided the materials are suitable for the task. Flanges made of AISI 316L and gaskets made of, for example, Viton can withstand both cleaning and sterilization, provided the materials are compatible with the chemicals and temperatures involved. The tool-free connection also makes it quick to dismantle the line for cleaning and reassemble it afterwards. Therefore, you should select the gasket material and design based on your CIP and SIP procedures from the outset.