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Frequently Asked Questions about Supa Maxi™

Why does the DN350-600 range have a pending approval EN 14525 to PN10 and not PN16 ?

It as a compromise between design and production cost in order to keep DN350-600 competitive. All Supa MaxiTM couplings DN50-600 are pressure rated at PN16 and thus designed for test with min. 1.5 x PN = 24 bar, but for DN350-600 we have chosen not to go for the PN16 approval since it would demand an approval test pressure of 29 bar – which is very high for such large couplings.

Will the Supa Maxi™ gate valve be available for gas applications?

As a start it is only made available for water and wastewater applications.

Why should I use a Supa Maxi™ gate valve when repairing an old pipe, and not just a normal coupling?

With a built-in gate valve it is easy to shut-off the water in case of further repair or replacement of the pipeline at a later stage.

Why should I use a Supa Maxi™ gate valve instead of other types of gate valves?

It is easier to install than e.g. a flanged gate valve or a spigot end gate valve with 2 flanges, and it is a more cost efficient solution considering the alternative cost of a valve + 2 flanges + bolt sets

Why did you choose to design the couplings with bolts to be tightened from the sleeve side?

Actually our first prototype was made with bolts tightened from the other side, but in a field trial we learned that when space in the trench is limited, it is much easier to tighten the bolts from the sleeve side.

Is it necessary to cross-tighten the bolts?

Yes, like for all other mechanical couplings it is recommended to cross-tighten the bolts. However, due to the unique design of the AVK coupling the bolts can be tightened individually to compensate for any ovality the pipe may have. To ease installation it is also recommended to pre-tighten the bolts before installing the coupling on the pipe. This ensures an even torque on the gasket and grip segments as well as making the installation faster in the uncomfortable surroundings of a pipe trench.

What am I supposed to do with the centre piece of the protection cap, after having torn it off?

It is made of recyclable PE, so scrap it in the same way as you do with other PE material.

Why have you chosen to deliver the couplings with permanent protection caps?

In our research prior to product development we learned from several customers that dirt from the trench normally finds it way into the gasket. Furthermore, the tightening of bolts and nuts at a specific torque is difficult with sand and debris in the threads. Consequently AVK designed a protection cap that covers the gasket and bolt threads to achieve an easier installation and maximum tightness.

Why is it not necessary to re-tighten the bolts after installation?

AVK uses an all-metal grip construction, and therefore compression will not be lost over time. This is the case when using plastic supports as an integrated part of the gasket system, since most plastics cold floats over time which causes a need for re-tightening the bolts.

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