LL Couplings

Screw is not the same screw! This phrase is especially true for Stainless Steel Pipe Fittings, which depend on the highest security and with little downtime.

The heart of a cutting ring fitting according to EN ISO 8434-1 (DIN 2353) is the cutting ring. In most cases, the specially designed and tested by Germanischer Lloyd Two edge cutting rings are used,  which have shown themselves to be very precise and highly reliable a million times. The cutting ring seals the fully assembled screw in three prominent places.

The major advantages are:

+ Extremely good cut in   
+ High tightness, no rust on the surface   
+ Safe installation   
+ No "set" of the cutting ring    

Through the use of surface-coated coupling nuts, the tightening torque reduces up to 35%. Furthermore, a cold welding of stainless steel material is prevented in the thread.

Functional description of the ferrule:
When tightening the nut the cutting ring is guided into the connector plug. The cone directs the cutting edge for increased tightening of the nut into the surface of the pipe. The tube is pushed into the nozzle base, where it can exert a sealing function with appropriate clean preparation. On the other side, the cutting ring is wedged by the pressure of the nut onto the tube. With dynamic load this fit provides additional support. If the tube is exactly perpendicular cut and deburred, three distinctive points can be sealed in the fully assembled fitting.

The cutting rings are divided into 3 series:

LL for compressed air, plastic pipes, laboratory apparatus; especially in the low pressure range up to max. PN 100   

L at larger size pressure loads up to max. PN 315, in the field of measurement and control technology, paper and plastics industry, pharmaceutical industry, aerospace, hydraulic systems and in the paint and coatings industry.   

S at high pressure, vibrations and high mechanical. Stresses in heavy machinery, shipbuilding, mining, chemical industry, industrial refrigeration, harbor and lock installations, offshore, petrochemical, usually in the pressure range from 250 up to PN 400 using kegligen screw threads to PN 630th    

Through the use of surface-coated coupling nuts, the tightening torque reduces up to 35%. Furthermore, a cold welding of stainless steel material is prevented in the thread.

Pipes: There are seamless, soft annealed stainless steel precision tubes from 1.4571 to DIN EN ISO 1127 tolerance class D4 / T3  its recommended not to use welded tubes: in the area of the weld material structure is modified, resulting in the snipping behavior of the cutting ring changing. However, thin-walled tubes are used for cost reasons, often the cutting ring cannot withstand the pressure during assembly. To ensure the function of the fitting nevertheless, we recommend the use of reinforcing sleeves.