diff --git a/TestBenchFramework/BenchControl/Elde/Valve/SetValvesOp.cs b/TestBenchFramework/BenchControl/Elde/Valve/SetValvesOp.cs
index 4650e32cb..7f2fa187d 100644
--- a/TestBenchFramework/BenchControl/Elde/Valve/SetValvesOp.cs
+++ b/TestBenchFramework/BenchControl/Elde/Valve/SetValvesOp.cs
@@ -33,8 +33,8 @@ namespace TBF.BenchControl.Elde.Valve
                 get
                 {
                     int max = 0;
-                    foreach (var vlv in VOpen)  if (vlv.Delay > max) max = vlv.Delay;
-                    foreach (var vlv in VClose) if (vlv.Delay > max) max = vlv.Delay;
+                    foreach (var vlv in VOpen)  if ((vlv != null) && (vlv.Delay > max)) max = vlv.Delay;
+                    foreach (var vlv in VClose) if ((vlv != null) && (vlv.Delay > max)) max = vlv.Delay;
                     return max;
                 }
             }
diff --git a/TestBenchFramework/BenchControl/Sequences/MainSeq.cs b/TestBenchFramework/BenchControl/Sequences/MainSeq.cs
index 63b1a69c1..683886ea3 100644
--- a/TestBenchFramework/BenchControl/Sequences/MainSeq.cs
+++ b/TestBenchFramework/BenchControl/Sequences/MainSeq.cs
@@ -497,9 +497,9 @@ namespace TBF.BenchControl.Sequences
                                     ButtonsEtc.SensitivityTestBtnEn |
                                     ((Cameras.Count > 0) ? ButtonsEtc.CalibrationBtnEn : 0) |
                                     ButtonsEtc.TryOpticalHeadsBtnEn)) |
-                                (((StateMachine.Balance1 != null) && !emptying1) ? ButtonsEtc.EmptyTankBtn1En : 0) |
-                                (((StateMachine.Balance2 != null) && !emptying2) ? ButtonsEtc.EmptyTankBtn2En : 0) |
-                                (((StateMachine.Balance3 != null) && !emptying3) ? ButtonsEtc.EmptyTankBtn3En : 0));
+                                (((StateMachine.Balance1 != null) && (StateMachine.EmptyTankValve1 != null) && !emptying1) ? ButtonsEtc.EmptyTankBtn1En : 0) |
+                                (((StateMachine.Balance2 != null) && (StateMachine.EmptyTankValve2 != null) && !emptying2) ? ButtonsEtc.EmptyTankBtn2En : 0) |
+                                (((StateMachine.Balance3 != null) && (StateMachine.EmptyTankValve3 != null) && !emptying3) ? ButtonsEtc.EmptyTankBtn3En : 0));
 
                 selection = Selection.None;
                 State.Create("MainSeq : Select an activity")
diff --git a/TestBenchFramework/BenchControl/StateMachine.cs b/TestBenchFramework/BenchControl/StateMachine.cs
index b119c40c0..99d2a7b2e 100644
--- a/TestBenchFramework/BenchControl/StateMachine.cs
+++ b/TestBenchFramework/BenchControl/StateMachine.cs
@@ -282,20 +282,17 @@ namespace TBF.BenchControl
 			// Automatic detection of empty tank valves
 			foreach (var opath in outputPaths)
 			{
-                if ((Balance1 != null) && (opath.Balance == Balance1.Cfg.Name))
+                if ((EmptyTankValve1 == null) && (Balance1 != null) && (opath.Balance == Balance1.Cfg.Name))
 				{
 					EmptyTankValve1 = TbfComponents.FindComponent(opath.EmptyTankValve) as IValve;
-					break;
 				}
-                if ((Balance2 != null) && (opath.Balance == Balance2.Cfg.Name))
+                if ((EmptyTankValve2 == null) && (Balance2 != null) && (opath.Balance == Balance2.Cfg.Name))
                 {
                     EmptyTankValve2 = TbfComponents.FindComponent(opath.EmptyTankValve) as IValve;
-                    break;
                 }
-                if ((Balance3 != null) && (opath.Balance == Balance3.Cfg.Name))
+                if ((EmptyTankValve3 == null) && (Balance3 != null) && (opath.Balance == Balance3.Cfg.Name))
                 {
                     EmptyTankValve3 = TbfComponents.FindComponent(opath.EmptyTankValve) as IValve;
-                    break;
                 }
             }