World loops 2: Electric Boogaloo.

code/modules/power/gravitygenerator.dm

@@ -128,7 +128,7 @@
 
 			for(var/area/A in gravity_generator:localareas)
 				var/obj/machinery/gravity_generator/G
-				for(G in world)
+				for(G in machines)
 					if((A.master in G.localareas) && (G.on))
 						break
 				if(!G)

code/modules/power/singularity/field_generator.dm

@@ -346,7 +346,7 @@ field_generator power level display
 	//I want to avoid using global variables.
 	spawn(1)
 		var/temp = 1 //stops spam
-		for(var/obj/machinery/singularity/O in world)
+		for(var/obj/machinery/singularity/O in machines)
 			if(O.last_warning && temp)
 				if((world.time - O.last_warning) > 50) //to stop message-spam
 					temp = 0

code/modules/power/singularity/singularity.dm

@@ -42,7 +42,7 @@ var/global/list/uneatable = list(
 		spawn(temp)
 			del(src)
 	..()
-	for(var/obj/machinery/singularity_beacon/singubeacon in world)
+	for(var/obj/machinery/singularity_beacon/singubeacon in machines)
 		if(singubeacon.active)
 			target = singubeacon
 			break

code/modules/power/turbine.dm

@@ -212,11 +212,11 @@
 /obj/machinery/computer/turbine_computer/New()
 	..()
 	spawn(5)
-		for(var/obj/machinery/compressor/C in world)
+		for(var/obj/machinery/compressor/C in machines)
 			if(id == C.comp_id)
 				compressor = C
 		doors = new /list()
-		for(var/obj/machinery/door/poddoor/P in world)
+		for(var/obj/machinery/door/poddoor/P in machines)
 			if(P.id == id)
 				doors += P