Intrumentation tube fittings - Technical Data

2.1 Dual cutting edge ring screw fitting

In most cases where a screw fitting is required benefits are achieved by using the dual cutting edge ring. As the union nut is tightened, initially the front cutting edge grips into the pipe and as it is tightened further the second cutting edge does so. Once the functional incisions of the cutting edges have finished, any further penetration is restricted by the cutting ring's design. At the same time, the ring has become wedged between pipe and union. This achieves a positive lock in both radial and axial direction. Thanks to the shape and high degree of positive locking any forces that arise get efficiently spread across the whole cone length. This achieves optimum resistance to vibration and a high level of reliability against flexural fatigue stress or fluctuations in pressure or temperature. By virtue of the high surface quality it is possible to achieve relatively advantageous levels of tightening torque. The noticeable increase in torque (after the cutting edges take grip as intended) makes it easy to spot any risk of 'over tightening'. Slight 'over tightening' does not impair the overall function.

Before tightening the union nut After tightening the union nut

2.2 Flared fitting

The flared fitting achieves a secure connection between unions with bore shape W DIN 3861 and 37º-flared pipe ends. Fitting is easy and can be repeated any number of times. You guide the tapered ring (with O-rings inserted) as far as it will go into the union. By virtue of its shape it sits tightly inside the union, gently clamped in place. As the union nut is tightened, the pressure ring pushes onto the pre-formed flaring of the pipe, which conversely presses itself onto the 37º cone of the tapered ring. The metallic/elastomer seal ensures that the most secure connection conceivable. The complete threaded fitting withstands high loading and protects against flexural fatigue forces and vibration. Even relatively great temperature fluctuations do not impair the connection's function. Nevertheless, the maximum permitted temperatures for the sealing materials used do need to be observed. This applies to all threaded fittings with elastomer seals!

2.3 Welded taper joints

Threaded pipe joints using welded tapers represent the logical extension of cutting ring threaded joints. The same unions based on bore shape W DIN 3861 and corresponding union nuts can be used, resulting in an identical fitted height. A secure and watertight connection between welded taper and union is provided by the metallic seal and additionally inserted O-ring. It withstands even extreme stress, especially from hydraulic shocks, vibration or temperature fluctuations.

Caution! Due to the build up of heat, the taper must be welded to the pipe before the O-ring is fitted.

2.4 Conical hose fitting

Thanks to the connecting cone used (24º) it is possible to perform a norm-compliant threaded connection with a union (bore shape W as per DIN 3861). The O-ring additionally fitted inside the cone creates a metallic/elastomer seal, which ensures that the join is highly leak-proof. Even under high levels of loading, it is insusceptible to hydraulic shocks or vibrations. Fitted dimensions are as for DIN 2353 and ISO 8434 specifications for threaded fittings. Pipe connection lines can optionally be fitted with cutting ring, tapered or welded taper joints.

7. Pipe joint measurements for unions

Screwed end as per DIN 3853/ISO 8434-1

Hole shape W as per DIN 3861

10.1 Preparing the pipe

1. Cut off pipes at right angles. Angle deviation of up to ½° to the pipe axis is permissible. Do not use a pipe cutter.
2. At the cut edges lightly deburr pipe on inside and outside. Bevel up to 0.2 x 45° is permissible. Clear away filings and debris.
3. In the case of elbows attention must be paid to the minimum height of the straight pipe end up to bend radius. It must be at least twice the height of the union nut.

10.2.1 Assembly using hardened pre-assembly mandrels

1. Lightly grease thread of the union nut, thread and cone of the pre-assembly mandrel and cutting ring with 'Fettpaste 325'.
2. Push union nut and cutting ring onto the pipe. Ensure cutting ring is in correct position.
3. Manually screw the union nut as far as possible onto the pre-assembly mandrel. As soon as it has engaged the pipe, a clear increase in torque becomes noticeable. Using spanner, tighten union nut by c. 1 turn. Note: The pipe must not turn with the nut!
4. Check whether a visible collar has accumulated on the pipe in front of the (first) cutting edge.

10.2.2 Finished assembly in the threaded fitting mandrel

Insert pre-assembled pipe into the threaded fitting mandrel. Further tighten nut by c. ½ of a turn across the noticeable point of increased force, using a spanner to prevent any rotation of the mandrel. For threaded fittings with no pre-assembly the procedure is similar to that with pre-assembly mandrels. The union nut just needs tightening by c. 1.1/4 to 1.1/2 turns after the pressure point.

Note: This type of screw connection is not recommended for the assembly of stainless steel components.

10.5 Assembling conical hose fittings

1. Lightly oil thread and O-ring or grease with lubricant.
2. Where necessary for angled, T and L fittings align pipe joint in the desired direction.
3. Screw on sealing cone nut firmly by hand and further tighten by c.. 1/3 turn with a spanner.

10.6 Fitting instructions for removable pipe joints for metallic gas pipelines

1. Solderless threaded pipe joints with male connectors may not be used in installations that need to comply with DVGW-TRGI’86 / TRF’88!
2. DCGW approval mark:
   NG – 4502AQ1441
   NG – 4502AQ1441
   DG – 4502AQ1280
   DG – 4502AQ1281
3. Suitable for gases as per DVGW worksheets G 260/I and G 260/II.
4. Permissible nominal pressures
5. Permitted operating temperature range of -20°C to +70°C.
6. Pipes compliant with ISO 1127, part 1.
7. Axial rigidity: resistant to pulling/pushing.
8. Repeat usability: 10 times.

Assembly instructions

When assembling stainless steel pipes pre-assembly must be done exclusively in the hardened pre-assembly mandrel. Any direct assembly in the stainless steel union must be avoided! The cones of the pre-assembly mandrel are subject to wear and a cone gauge must therefore be used at regular intervals to check that they remain true to gauge size. In order to avoid incorrect assembly from the outset, worn pre-assembly mandrels should be replaced with new ones.

We recommend only seamless, softly annealed stainless steel pipes made of material 1.4571 to DIN 2391, part 1 or DIN 2462, tolerance class D4 / T3.

Note: No welded pipes!

Saw the pipes off at right angles in a jig, saw off permitted angle deviation, ** query **, zuverlässige zur Rohrachse max 0,5°.

Do not use a pipe cutters!

Lightly deburr pipes inside and outside. Bevel of max. 0.2 x 45° is permissible. For thin-walled pipes we recommend using reinforcing sleeves (VSH). Clamp the relevant pre-assembly mandrel for the respective pipe into the bench vice.

Loosely screw the 24° inner cone and the outer thread of the pre-assembly mandrel, plus the whole inside of the union nut onto the pre-assembly mandrel so that the grease can spread itself about better within the thread.

Order details for
ES grease 325

Tube 50 g: Grease 325 – 50 g

Can 250g: Grease 325 – 250 g

Can 1000g: Grease 325 – 1000g

Push union nut and cutting ring over the pipe end.

Note: Cutting ring always in direction of the connecting cone.

Push combined unit of pipe, cutting ring and union nut into the pre-assembly mandrel.

A mark on the union nut makes it easier to monitor the required rotation.

Screw union nut by hand onto the pre-assembly mandrel until you feel it make contact. At the same time push the pipe against the end stop in the bottom of the pre-assembly mandrel.

Using a spanner, tighten by c. 1 – 1 ½ turns (varies depending on size). The pipe twists radially in the process by up to c. ½ turn, but thereafter it should not turn with the nut.

Note: When pre-assembling double edge cutting rings, tighten as far as possible to the upper tightening limits (c. 1 ¼ - 1 ½ turns).

Loosen union nut.

Check cutting edge's incisions on the pipe. The bulging covers a part of the face of the cutting ring equally across its full scope. The cutting ring is allowed to rotate radially, but it should not be possible to push it forwards.

Due to the tough pipe material 1.4571 no bulging is created at the cutting edge of the kind seen with steel pipes.

After approval, fit the pre-assembled pipe into the threaded fitting mandrel.

Tighten the union nut by c. ¼ - ½ turns, across the noticeable increase in force.

The union needs to be held by a spanner to stop it turning as well.

When working with pipes of larger dimensions, extensions for the flat spanner are required/pipe extension).

For reasons of cost thin-walled pipes are often used, which are unable to withstand the pressure of the cutting ring during assembly.

So that in spite of this you are able to ensure that the threaded joint functions well, we recommend using our reinforcement sleeves.

The reinforcement sleeves can be easily inserted into the pipe up to the knurl.

Using a soft hammer, you knock the knurled part into the pipe. This creates a tight fit without widening the pipe.

The reinforcement sleeve sits firmly in place and supports the pipe against any contraction during the assembly process.