Coupling system including a safety fastener device

1. A coupling system comprising:

a coupling which is fastened to one end of a pipe via a fastening connection;

a sleeve surrounding the fastening connection and having a first end welded to the pipe and a second end with a hook; and

a retention plate with a hole centered on an axis of the pipe and a notch which receives the hook at the second end of the sleeve, the retention plate being secured to the coupling,

wherein the retention plate abuts the coupling so that the hook is received between the coupling and the notch such that the hook provides fastening between the coupling and the pipe in the event of the fastening connection breaks.

2. A coupling system according to claim 1 , wherein when the fastening connection is not broken, clearance exists between the hook and the coupling.

3. A coupling system according to claim 2 , wherein said clearance is axial clearance in an axial direction of a cylindrical portion of the coupling that is to be engaged with the end of the pipe.

4. A coupling system according to claim 2 , wherein the clearance lies in the range 0.1 mm to 0.5 mm.

5. A coupling system according to claim 1 , wherein the fastening connection is an annular weld.

6. A coupling system according to claim 1 , wherein a periphery of the sleeve is provided with openings enabling an external operator to see the fastening connection when the sleeve is fastened to the pipe.

7. A coupling system according to claim 1 , wherein the sleeve includes at least one fastener tab extending axially from the first end to the second end hook.

8. A coupling system according to claim 1 , wherein the hook includes a projection which extends radially.