DIN 11851 in the food industry: fittings, gaskets and areas of application

Anyone who works in a dairy, winery, or beverage plant is familiar with the DIN 11851 fitting : the round nut that is tightened by hand, or with a wrench, to connect pipes, pumps, tanks, and valves. Originally developed in Germany for the dairy industry, so much so that it is still called a "dairy coupling" today, it has become one of the most widely used standards in European food processing plants.

In this guide we analyse how a DIN 11851 fitting is made, how to choose the right gasket, what its strengths and limitations are from a hygienic point of view, how it compares with other standards and in which sectors it is used.

What is DIN 11851?

DIN 11851 is the German standard that defines the dimensions and characteristics of detachable stainless steel threaded fittings for the food, chemical, and pharmaceutical industries. Its main advantage is interchangeability : fittings from different manufacturers, if built according to the standard, can be connected without adapters.

The standard covers nominal diameters from DN 10 to DN 150 and uses a round thread , indicated by the abbreviation Rd, which is much more resistant to impacts and easier to clean than a triangular profile thread.

The end versions

The fitting parts connect to the system in different ways:

•     To weld: for rigid stainless steel pipes, in dedicated AISI 304 or AISI 316L versions.
•     To churn: the fitting is expanded inside the pipe, without welding.
•     Hose holder: for connecting flexible pipes, joined or fixed with clamps
•     Gas threaded, flanged or reduced: to connect components with different connections or lines of different diameters.

The range is completed with bends, tees, reducers, caps, and adapters. Universalflex offers a wide selection of DIN 11851 fittings in AISI 304 and AISI 316L stainless steel, with a polished internal finish for food-grade applications.

Diameters and pressures

The standard provides for maximum operating pressures that decrease as the diameter increases:

• DN 10 – DN 40: up to 40 bar
• DN 50 – DN 100: up to 25 bar
• DN 125 – DN 150: up to 16 bar

Note: The actual limit of the system always depends on the gasket compound, the working temperature and the type of tightening.

 

The gasket: the heart of the seal

In a DIN 11851 fitting, stainless steel guarantees mechanical resistance, but it is the gasket that determines tightness, compatibility with the product and durability over time.

Material	Key features	Typical uses	To be avoided
EPDM	Excellent resistance to hot water, steam and alkaline detergents	Beverages, water, juices, lines with frequent CIP cleaning	Oils and fats
NBR	Good resistance to fats and oils	Milk, cream, edible oils, fatty products	Steam and prolonged high temperatures
FKM (FPM)	High chemical and thermal resistance, even to aromas	Aggressive products, essential oils, high temperatures	Prolonged saturated steam, some alkaline solutions
Silicone (MVQ)	Wide temperature range, inert and odorless	Delicate products, hot and cold applications	High mechanical stress, oils
PTFE	Almost total chemical inertia, high temperature	Aggressive products, solvents, multi-product lines	Assembly with uncontrolled tightening: PTFE is rigid and not very elastic at low temperatures

For the food industry, blue and metal-detectable gaskets are also available , which, in the event of breakage, allow any fragments to be detected either visually or with line inspection systems. Universalflex supplies DIN 11851 gaskets in PTFE, silicone, NBR, EPDM, and FKM.

 

DIN 11851 and hygiene: strengths and limitations

The DIN 11851 fitting is widely appreciated for its robustness and ease of assembly and disassembly without complex equipment. For this reason, it is used in system areas requiring frequent inspection or manual cleaning.

From a hygienic design perspective, however, it has a known limitation: in the standard version, the gasket compression is not controlled . If the ring is tightened too much, the gasket can protrude into the duct; if it is tightened too little, a small gap remains between the gasket and the steel. In both cases, this creates a point where the product can stagnate and which CIP cleaning is difficult to reach.

For this reason, in the most critical applications, such as aseptic processes or particularly sensitive products, standards designed for controlled compression of the gasket, such as DIN 11864, or Clamp fittings, are preferred. 

In existing DIN 11851 systems, it is still possible to improve hygienic performance with some measures:

1.  Tighten the swivel correctly and evenly, without forcing;
2. Use new gaskets made of the right material, replacing them at regular intervals and whenever they become deformed, hardened or cracked;
3. Check the correct seating and orientation of the gasket at each reassembly;
4. Lubricate the thread, if necessary, only with lubricants suitable for food contact.

 

DIN 11851 compared to other standards

Standard	Connection type	Hygienic features	Typical uses
DIN 11851	Threaded with swivel	Good (uncontrolled gasket compression)	Dairy, wine, beverage, canning
Clamp (CLAMP BS 4825, DIN 32676, ISO 2852)	Clamp with gasket between two fittings	Very good (very quick disassembly)	Pharmaceutical, cosmetic, breweries, beverage
SMS	Threaded with swivel	Similar to DIN 11851	Canning and dairy products
DIN 11864	Threaded, flanged or clamp, with controlled compression seal	Elevate; designed for aseptic processes	Aseptic, pharmaceutical, sensitive products

Different standards are not compatible: connecting components with different connections requires dedicated adapters. Universalflex supplies fittings according to all major standards, including DIN 11851, DIN 11853, DIN 11864, Clamp, SMS, and Garolla. For more information on materials and selection criteria, please consult our technical guide to stainless steel fittings.

 

Applications fields

• DairyUsed on milk collection tankers, receiving platforms, pasteurizers, and boilers. With fatty products (cream, butter), it is combined with NBR or EPDM gaskets for CIP cleaning.
• Oenology: The reference standard in the cellar for connecting transfer pipes, pumps, filters and fermentation tanks, thanks to the ease of operation with neutral EPDM or Silicone gaskets.
• Beverages and beer: Widely used on heat exchangers, tanks and transfer lines in water, juice and beer.
• Canning and confectioneryIdeal for tomato, syrup and cream processing lines, where the speed of disassembly facilitates end-of-season cleaning.
• Cosmetic and chemical: Used in non-sterile phases for the management of emulsions, soaps and solvents (with PTFE or FKM seals).

 

Regulations: a compliant connection is not enough

DIN 11851 defines dimensions and fits, but not the food safety of materials. Fittings and gaskets must also comply with regulations on materials intended for contact with food, such as Regulation (EC) 1935/2004 (MOCA) and, for export, FDA regulations. For steel, it is useful to request the EN 10204 3.1 certificate, which guarantees the traceability of the material.

 

Universalflex Group solutions for DIN 11851 fittings

Universalflex supplies the entire DIN 11851 system: stainless steel fittings, gaskets in all major materials, and ready-to-install DIN-compliant food-grade hose assemblies , complete with declarations of conformity. Our technical department supports customers in selecting the most suitable gasket and standard, and in creating adapters between different standards.

Need to replace DIN 11851 fittings or gaskets on your system? Contact our technicians or discover our full range of stainless steel fittings.

 

 

FAQ on DIN 11851 fittings

What is a DIN 11851 fitting?

It is a detachable stainless steel threaded fitting, defined by the German standard DIN 11851, used to connect pipes, pumps, tanks, and valves in food processing plants. It consists of a threaded part, a conical part, a round nut, and a gasket.

Which gasket should I choose for a DIN 11851 fitting?

The choice depends on the fluid and sanitization cycles: EPDM for water, beverages, and alkaline CIP washes; NBR for fatty products such as milk and oils; FKM for high temperatures or oils; PTFE for maximum chemical resistance.

What is the maximum pressure of a DIN 11851 fitting?

The standard specifies up to 40 bar for diameters from DN 10 to DN 40, 25 bar from DN 50 to DN 100 and 16 bar for DN 125 and DN 150. The actual limit must always be verified based on the operating temperature and the type of gasket.

Are DIN 11851 fittings compatible with Clamp or SMS fittings?

No, each standard has different geometries and threads. To connect lines with different standards, you need to use specific adapters (e.g., DIN 11851 / Clamp).

Is DIN 11851 suitable for aseptic processes?

In the standard version, the gasket compression is not controlled and can create small stagnation zones. For aseptic processes, standards such as DIN 11864 or hygienic clamp fittings are preferred.