Cuando he visitado clientes y en particular a los que ofrecen soluciones de empernado, siempre me interesó las características técnicas cuando se trata de apretar tantos pernos grandes al mismo tiempo.

Un claro ejemplo para entender lo que el personal de mantenimiento o el instalador tiene que lograr es la conexión de secciones de tuberías.

La conexión de grandes tuberías puede hacerse mediante la soldadura o montaje de brida. Cuando las tuberías contienen gases o fluidos peligrosos, esta conexión debe ser bien asegurada. Aplicaciones como postes para molinos de viento, pilares para carros de cables también tiene que ser controlado y monitoreado ya que ésta conexión tiene que ser fuerte, duradera y segura.

Uno de los principales puntos clave en la conexión de dos tuberías con una brida es la tensión aplicada a los pernos. Los ingenieros están determinando estos valores según cada caso. La tensión definirá el sellado o la fuerza de la conexión. Demasiada tensión en el perno creará un riesgo de rotura, y poca tensión hará una conexión débil.

Por lo tanto, en cada proyecto, la tensión de los pernos está claramente definida por el diseñador y el instalador tiene que llevar un control estricto.

Con el fin de obtener también una distribución suave del esfuerzo alrededor de la conexión, estos pernos tienen que ser apretados en secuencias con los opuestos alrededor de la circunferencia.

La colocación de una brida para conectar dos tuberías puede hacerse de dos maneras diferentes: apretando o tensando.

Aquí hay una descripción de cada uno de estos procesos:

 

Tensado

Una máquina tira de la parte de la barra roscada del perno y cuando se alcanza un cierto esfuerzo, entonces la tuerca del perno puede ser ensamblada a mano. Después de esto, la máquina libera el esfuerzo y el perno se coloca de forma segura con la tensión adecuada.

hydraulic bolt tensioners

 

Torqueing

In this case a torque controlled machine tightens the nut of the bolt directly until the desired value is reached.

Torqueing Machine at Work

The tightening job can also be done by hand and in this case the installer knows how many turns need to be achieved in order to reach the desired torque. Usually a mark is done with a pen or chalk on the bolt, and the striking or lever wrench is used to turn.
In some cases, this hand operation is the only way to do the job, especially when working at height or in difficult or narrow places.

The SAFEWRENCH helps mechanical engineers thanks to its efficient and safe positioning on the nut. They can use it as a counter-wrench, to avoid the other side of the bolt to turn when using hydraulic tightening.
The SAFEWRENCH can also be considered as a tightening device itself. As it stays on the nut, it can be used even with a work overhead, it is a great way to manually tight bolts in a safe manner.

 

Now, the real question for professionals is: When should I use one or the other solution?

Is tensioning better than torqueing when it comes to bolting solutions? It happens that the manufacturer or designer is telling you what to use, in this case you have no choice and you need to follow instructions.

But when you have a choice and you are looking for the best solution you need to make decision.

The SAFEWRENCH can also be considered as a tightening device itself. As it stays on the nut, it can be used even with a work overhead, it is a great way to manually tight bolts in a safe manner.

Every solutions have pros and cons, but let’s have a look at the big principles

 

    Tensioning

This bolting solution appears to be more precise. Many bolts will be tight at the same time with a perfect effort and nothing really look to suffer under friction. It is probably the most ‘natural’ way to put bolts in tension. In this case no counter wrench is needed and even if the access is limited on one side of the flange, you can always achieve the job.
It is a good and reliable system especially when big bolts or studs are involved. The strength is highly accurate and the control is quite easy.
Tensioning is also quite expensive and maybe longer to put in place than other systems.

 

     Torqueing

Stretching the bolt here is done by simply turning the nut. Not only the tension increases the strength the device has to reach to go further but the friction on the surface of the component to be tighten. Many factors are mixing to reach the right torque.
This system is simpler to use and less expensive. It can be used also to dismantle, so it is more versatile. But surely less accurate than tensioners but more adapted to small bolts.
Instead of measuring the torque, you can also count and monitor the angle between the stud and the nut in order to reach the desired value.
In the torqueing process, you need a counter-wrench that can be released under pressure.

 

     Striking

SAFEWRENCH as a counter wrench or as a torqueing device is ideal. After the process, the Safewrench can be stroke to release the pressure and be removed from the other side of the bolt.
For assembling, as it secures itself on the nut, it is easy to strike with two hands on the hammer even if used overhead. SAFEWRENCH is a patented tool equipped with 2 retaining rings allowing to maintain firmly and safely itself on bolts.
It is as easy to use as a regular striking wrench and does not require additional devices to secure the mechanical engineer jobs such as handles, magnets or springs.

The SAFEWRENCH comes in both steel and non-sparking materials.

Striking Wrench

Bertrand Causse