diff --git a/src/aeros_equipment/service.py b/src/aeros_equipment/service.py
index 64d9a80..315746b 100644
--- a/src/aeros_equipment/service.py
+++ b/src/aeros_equipment/service.py
@@ -364,6 +364,8 @@ def get_distribution_from_db(parameters: dict, is_repairable: bool = True, best_
         elif distribution == "Normal":
             mu = parameters.get("mu", 0)
             sigma = parameters.get("sigma", 1)
+            if sigma > 1000 or sigma < 0:
+                sigma = 999
             return "Normal", mu, sigma
         elif distribution == "Weibull":
             # Assuming Weibull parameters are available
@@ -374,6 +376,8 @@ def get_distribution_from_db(parameters: dict, is_repairable: bool = True, best_
             # Default to Normal
             mu = parameters.get("mu", 0)
             sigma = parameters.get("sigma", 1)
+            if sigma > 1000 or sigma < 0:
+                sigma = 999
             return "Normal", mu, sigma
     
 async def update_oh_interval_offset(*, aeros_db_session, overhaul_offset, overhaul_interval, project_name):
diff --git a/tests/unit/test_update_equipment_simulation.py b/tests/unit/test_update_equipment_simulation.py
index c6fa078..b5b511b 100644
--- a/tests/unit/test_update_equipment_simulation.py
+++ b/tests/unit/test_update_equipment_simulation.py
@@ -225,3 +225,74 @@ async def test_update_equipment_for_simulation_missing_reliability():
         assert eq_node["cmDisUnitCode"] == "UHour"
         assert eq_node["relDisUnitCode"] == "UHour"
         assert eq_node["ohDisUnitCode"] == "UHour"
+
+@pytest.mark.asyncio
+async def test_update_equipment_for_simulation_sigma_constraint():
+    # Mock parameters
+    db_session = AsyncMock()
+    aeros_db_session = AsyncMock()
+    project_name = "TestProject"
+    simulation_duration = 8760
+    overhaul_duration = 72
+    overhaul_interval = 8000
+    offset = 0
+    schematic_name = "TestSchematic"
+    
+    # Mock get_aeros_schematic_by_name
+    mock_schematic = MagicMock()
+    mock_schematic.id = 1
+    
+    # Mock db_session.execute
+    mock_eq = MagicMock()
+    mock_eq.location_tag = "EQ_SIGMA"
+    mock_eq_result = MagicMock()
+    mock_eq_result.scalars.return_value.all.return_value = [mock_eq]
+    
+    mock_empty_result = MagicMock()
+    mock_empty_result.scalars.return_value.all.return_value = []
+
+    db_session.execute.side_effect = [
+        mock_eq_result,    # equipments
+        mock_empty_result, # rbd_group
+        mock_empty_result  # non_repairable
+    ]
+    
+    # Mock nodes data
+    mock_nodes_data = [
+        {"equipmentName": "EQ_SIGMA", "relDisType": "Fixed", "relDisP1": 0}
+    ]
+    
+    # Mock reliability data with high sigma (> 1000)
+    mock_reliability_data = {
+        "EQ_SIGMA": {
+            "relDisType": "Normal",
+            "relDisP1": 100,  # mu
+            "relDisP2": 1500, # sigma
+            "cmDisType": "Fixed",
+            "cmDisP1": 0,
+            "cmDisP2": 0
+        }
+    }
+    
+    with patch("src.aeros_equipment.service.get_aeros_schematic_by_name", return_value=mock_schematic), \
+         patch("src.aeros_equipment.service.get_aeros_equipment_by_location_tag", return_value=mock_nodes_data), \
+         patch("src.aeros_equipment.service.get_asset_batch", return_value=mock_reliability_data), \
+         patch("src.aeros_equipment.service.update_oh_interval_offset", return_value=None), \
+         patch("src.aeros_equipment.service.update_node", return_value=None) as mock_update_node:
+        
+        # Run
+        await update_equipment_for_simulation(
+            db_session=db_session,
+            aeros_db_session=aeros_db_session,
+            project_name=project_name,
+            simulation_duration=simulation_duration,
+            overhaul_duration=overhaul_duration,
+            overhaul_interval=overhaul_interval,
+            offset=offset,
+            schematic_name=schematic_name
+        )
+        
+        # Check if sigma was constrained correctly
+        called_args = mock_update_node.call_args[1]
+        eq_node = called_args["equipment_nodes"][0]
+        assert eq_node["relDisP2"] == 999