Interlock Scheme for Screw Conveyor

Dear Sirs,

Attached herewith is some interlock scheme for our screw converyor scheme,it has got two conditions
1) OFF
2) Interlock

Depending upon process conditions the system will be OFF or if the interlock (Process Parameters) fails again the system will be off,

I wanted to know wats purpose of using both OFF and Interlock in the diagram


Regards

JOSE

It looks like this conveyor is used for product moving from one bin to another bins. LSHH are used to prevent overfilling. Overfilling means an alarm condition. Conveyor must be stopped and can be restarted only when LSHH aren't active. I don't know physical sense of pressure sensor PSHH in your case. SSL means rotation quard, IMHO.
LSLL signalize source bin is empty. In this case screw conveyor working is possible but haven't sense.
Difference is in sense of situations. In first case this is an alarm; in second case - product absence. Of course, your customer may want to realize different system reaction to that situations.