diff --git a/site_ansto/instrument/util/write_tree.tcl b/site_ansto/instrument/util/write_tree.tcl
index 989eb8d4..75382d53 100644
--- a/site_ansto/instrument/util/write_tree.tcl
+++ b/site_ansto/instrument/util/write_tree.tcl
@@ -1,35 +1,54 @@
   namespace eval ::utility {}
   proc ::utility::writeNode {tc_root { do_props 0 } { level 0 }} {
-    set space [string repeat "  " $level]
-    set val [hval $tc_root]
-    set nam [lindex [split $tc_root "/"] end]
-    if {"$val" == ""} {
-      set line "$nam ([hinfo $tc_root])"
-    } else {
-      set line "$nam ([hinfo $tc_root]) = $val"
-    }
-    clientput "$space* $line"
-    if {"[string tolower "$do_props"]" == "-prop"} {
-      set props [hlistprop $tc_root]
-      #clientput "<<$props>>"
-      foreach prop $props {
-        #clientput "prop: $prop"
-        set flds [split $prop "="]
-        #clientput "flds: $flds"
-        if {[llength $flds] > 1} {
-          set fld0 [lindex $flds 0]
-          #clientput "fld0: $fld0"
-          if {[hpropexists $tc_root $fld0]} {
-            set rst [hgetprop $tc_root $fld0]
-            set nam [lindex [split [lindex $rst 0] "."] 1]
-            set rst [join [lrange [split $rst " "] 1 end] " "]
-            clientput "$space    - $nam $rst"
+    if [ catch {
+      set space [string repeat "  " $level]
+      if [ catch {
+        set val [hval $tc_root]
+      } message ] {
+        clientput "Error in writeNode/hval for $tc_root : $message"
+        return
+      }
+      set nam [lindex [split $tc_root "/"] end]
+      if [ catch {
+        if {"$val" == ""} {
+          set line "$nam ([hinfo $tc_root])"
+        } else {
+          set line "$nam ([hinfo $tc_root]) = $val"
+        }
+      } message ] {
+        clientput "Error in writeNode/hinfo for $tc_root : $message"
+        return
+      }
+      clientput "$space* $line"
+      if {"[string tolower "$do_props"]" == "-prop"} {
+        if [ catch {
+          set props [hlistprop $tc_root]
+        } message ] {
+          clientput "Error in writeNode/hlistprop for $tc_root : $message"
+          return
+        }
+        #clientput "<<$props>>"
+        foreach prop $props {
+          #clientput "prop: $prop"
+          set flds [split $prop "="]
+          #clientput "flds: $flds"
+          if {[llength $flds] > 1} {
+            set fld0 [lindex $flds 0]
+            #clientput "fld0: $fld0"
+            if {[hpropexists $tc_root $fld0]} {
+              set rst [hgetprop $tc_root $fld0]
+              set nam [lindex [split [lindex $rst 0] "."] 1]
+              set rst [join [lrange [split $rst " "] 1 end] " "]
+              clientput "$space    - $nam $rst"
+            }
           }
         }
       }
-    }
-    foreach node [hlist $tc_root] {
-      ::utility::writeNode $tc_root/$node "$do_props" [expr {$level + 1}]
+      foreach node [hlist $tc_root] {
+        ::utility::writeNode $tc_root/$node "$do_props" [expr {$level + 1}]
+      }
+    } message ] {
+      clientput "Error in writeNode for $tc_root : $message"
     }
   }