SIL 2

[Lc85]

We have an airheater driven by an inverter driven motor. This inverter driven motor has a dc motor as a back up and also an air motor as a further back up. The client has requested that the system be SIL 2. This is a slowly rotating heater (1rpm) with a high inertia.

The inverter is an altivar 71 and is rated sil 2. The client has asked for an emergency stop to be fitted for the drive unit so,when pressed this will have to prevent the air motor and DC motor from starting also. The heater will not stop straight away due to its inertia.

My question is can we get an emergency stop button that is rated SIL 2 and can incorparate the three drives?

Thanks

 

[ScottyUK]

No. You can't buy a button that is rated SIL2, although you can buy a button suitable for use within a SIL2 system.

The SIL rating applies to the overall system, not to individual components. It is entirely possible to build a system with no SIL rating whatsoever using exclusively SIL rated components if you get the design wrong.

 

[electricuwe]

The complete setup looks strange to me. On one side there are three different Motors to provide redundant power to drive- therefore keeping this device rotating seems to be extremely essential, on the other side there is a requirement to stop manually -making wrong action on the pushbutton a likely case of failure.

Please describe the total System. A much more approbriate approach to me would be to cut off engergy to the heating element istself (electric power or gas or what else) in case there is no Rotation anymore.

If this is no solution an electrical activated mechanical brake is the only way.