Emerson manual Interlock Permissive Emergency Shutdown, Rosemount 848L, Reference Manual

Reference Manual

00809-0100-4696, Rev AA September 2004

Rosemount 848L

Interlock

Permissive

Emergency Shutdown

An interlock switch is easily added as follows, where input 4 is the normally closed interlock:

	1		2	4	Out1
+--	--	+--	--	+--/-----------------	( )--+ OUT1_EQ
			3
		+--	--	+

•The first expression is still OR(IN(2),IN(3))

•The top and final expression is now AND(IN(1),OR(IN(2),IN(3)),IN(4)); Enter the expression and test as above.

A permissive switch may be added, with or without the interlock, as shown, where 5 is the permissive:

	1		2	5	4	Out1
+--	--	+	------	--+--	/-----------	( )--+ OUT1_EQ
			3
		+	----------	+

•The first expression is now AND(IN(2),IN(5))

•The second expression is OR(AND(IN(2),IN(5)),IN(3))

•The final expression is AND(IN(1),OR(AND(IN(2),IN(5)),IN(3)),IN(4));

In ladder logic, this would be shown as a switch for power to a section of the ladder if there was more than one thing to be turned off. In the 848L, one contact must be shown for each rung but only one input is required. The shutdown contact is input 8 in the drawing below:

	1		2	5	4	8	Out1
+--	--	+	------	--+--	/	----/----	( )--+ OUT1_EQ
			3
		+	----------	+

•The first expression is still AND(IN(2),IN(5))

•The second expression is OR(AND(IN(2),IN(5)),IN(3))

•The final expression is AND(IN(1),OR(AND(IN(2),IN(5)),IN(3)),IN(4),IN(8));

E-5