Supplier: KCES
08 March, 2012

Please find answers to frequently asked questions (FAQ) here.

According to which material specifications are STRAUB couplings manufactured?
STRAUB-GRIP-L in W2 and W5,
STRAUB-FLEX and -OPEN-FLEX in W1, W2, and W5

Does STRAUB provide stepped couplings?

Basically, STRAUB-FLEX couplings can be used to compensate for the differences in diameter of up to 10mm, depending on the diameter. Upon request, also larger differences in the diameter can be compensated for using STRAUB-STEP-FLEX couplings.

Does STRAUB sell only through dealers?

Do STRAUB couplings require additional mounting points?
STRAUB-GRIP couplings do not require additional mounting points.
When using STRAUB-FLEX or STRAUB-OPEN-FLEX couplings, one fixing point per coupling has to be installed.

Does the STRAUB concept also work on hard pipe surfaces?
Yes, it does. The patented anchoring rings enable faultless anchoring to be achieved even with hard pipe material surfaces.

Up to what extent the STRAUB couplings attenuate pressure surges and sound compared to a welded pipe connection?
Depending on the type of coupling used, the attenuation values are 3 to 7-times better than those achieved with welded or flanged connections.
What are the usable clamping ranges for the different coupling sizes?
The clamping ranges of the couplings are indicated on the data sheets. Refer to Products. Within these ranges, trouble-free installation of the coupling is ensured. Under certain conditions, also pipes of diameters outside these clamping ranges may be connected to each other. If in doubt, please contact STRAUB Application Technology Department.
What is the lifespan for STRAUB sleeves?
Assuming favourable conditions, lifespan of more than 25 years can be expected.

Are temporary higher operating temperatures acceptable?

Yes, they are. But if the maximum operating temperature is exceeded repeatedly or for a longer period of time, lifespan of the sealing sleeve will be reduced.
Do STRAUB couplings also work under vacuum conditions?

Yes, they do. Values of up to 50mbar abs. can be achieved. When the coupling is used under vacuum conditions, the strip insert must be used.
Are installation tolerances allowed to be added up?
No, they are not. The installation tolerances given are limits that apply to the individual application. If several cases occur simultaneously, the allowable values must be reduced. If in doubt, please contact STRAUB Application Technology Department.

Are STRAUB couplings able to accept radial load?
No, they are not. (The couplings can accept such load to a certain extent which, however, will result in coupling misalignment.)

What is the difference between the STRAUB-METAL-GRIP and STRAUB-GRIP-L type couplings?
Both are axially restraint couplings for metal pipes. The STRAUB-METAL-GRIP type is of significantly stronger design. The STRAUB-GRIP-L is strong enough for approx. 75 per cent of all applications.

Is the STRAUB-OPEN-FLEX leak-proof with the sleeve cut? How so?
Yes, it is. The sealing sleeve is manufactured in the same way a FLEX sealing sleeve is and is then cut. Thus, cutting surfaces are achieved that absolutely match and provide 100 per cent leak-proof sealing performance.

What are intervals after which the bolts have to be re-tightened?

The bolts do not require to be re-tightened. STRAUB couplings are completely maintenance free.
Are the pipe ends required to be prepared?
No, they are not. Only remove dirt, rust or paint remainders. Debur, if necessary.

What is the lifespan for STRAUB couplings?

25 years and more can be achieved. There are couplings that have been in use since 1974.

What is a strip insert used for?
It is used to protect the sealing sleeve under vacuum conditions, to fill large gaps between pipe ends, to prevent rubber swelling, axial displacement, axis misalignment, or if external overpressure is present.

How does the axial movement concept of the STRAUB-FLEX/-OPEN-FLEX work?
The Sealing lip is flexing, thereby taking up any axial movement of the pipe. Because of the specific shape of the sealing lip the coupling can compensate for a certain amount of axial change in pipe length without friction occurring between the surface of the pipe and the rubber. As a result, such movements can be absorbed as often as required.

Why there are differences in nominal pressure between STRAUB-FLEX and STRAUB-OPEN-FLEX couplings?
Because of the slotted casings (internal weakening).

Are STRAUB couplings electrically conductive?
STRAUB-GRIP-L and STRAUB-METAL-GRIP are electrically conductive. STRAUB-FLEX and STRAUB-OPEN-FLEX couplings can be made electrically conductive by using the "Current Conductor".