diff --git a/erpnext/manufacturing/doctype/bom/bom.py b/erpnext/manufacturing/doctype/bom/bom.py
index 1d7d451..6e1c7dd 100644
--- a/erpnext/manufacturing/doctype/bom/bom.py
+++ b/erpnext/manufacturing/doctype/bom/bom.py
@@ -517,17 +517,21 @@
 	def update_rate_and_time(self, row, update_hour_rate = False):
 		if not row.hour_rate or update_hour_rate:
 			hour_rate = flt(frappe.get_cached_value("Workstation", row.workstation, "hour_rate"))
-			row.hour_rate = (hour_rate / flt(self.conversion_rate)
-				if self.conversion_rate and hour_rate else hour_rate)
+
+			if hour_rate:
+				row.hour_rate = (hour_rate / flt(self.conversion_rate)
+					if self.conversion_rate and hour_rate else hour_rate)
 
 			if self.routing:
-				row.time_in_mins = flt(frappe.db.get_value("BOM Operation", {
+				time_in_mins = flt(frappe.db.get_value("BOM Operation", {
 						"workstation": row.workstation,
 						"operation": row.operation,
-						"sequence_id": row.sequence_id,
 						"parent": self.routing
 				}, ["time_in_mins"]))
 
+				if time_in_mins:
+					row.time_in_mins = time_in_mins
+
 		if row.hour_rate and row.time_in_mins:
 			row.base_hour_rate = flt(row.hour_rate) * flt(self.conversion_rate)
 			row.operating_cost = flt(row.hour_rate) * flt(row.time_in_mins) / 60.0
diff --git a/erpnext/patches.txt b/erpnext/patches.txt
index 311e785..0f6a606 100644
--- a/erpnext/patches.txt
+++ b/erpnext/patches.txt
@@ -299,3 +299,4 @@
 erpnext.patches.v13_0.reset_clearance_date_for_intracompany_payment_entries
 erpnext.patches.v13_0.einvoicing_deprecation_warning
 erpnext.patches.v14_0.delete_einvoicing_doctypes
+erpnext.patches.v13_0.set_operation_time_based_on_operating_cost
\ No newline at end of file
diff --git a/erpnext/patches/v13_0/set_operation_time_based_on_operating_cost.py b/erpnext/patches/v13_0/set_operation_time_based_on_operating_cost.py
new file mode 100644
index 0000000..4acbdd6
--- /dev/null
+++ b/erpnext/patches/v13_0/set_operation_time_based_on_operating_cost.py
@@ -0,0 +1,15 @@
+import frappe
+
+def execute():
+	frappe.reload_doc('manufacturing', 'doctype', 'bom')
+	frappe.reload_doc('manufacturing', 'doctype', 'bom_operation')
+
+	frappe.db.sql('''
+		UPDATE
+			`tabBOM Operation`
+		SET
+			time_in_mins = (operating_cost * 60) / hour_rate
+		WHERE
+			time_in_mins = 0 AND operating_cost > 0
+			AND hour_rate > 0 AND docstatus = 1 AND parenttype = "BOM"
+	''')
\ No newline at end of file