Complex sentence: It is also planned that No.18 will be broken up in 2013 following the arrival of the new diesel locomotive currently referred to as'No.21' while it is still relatively new it will be another locomotive being broken up.
Split into simpler sentences: It is also planned that No.18 will be broken up in 2013 following the arrival of the new diesel locomotive currently referred to as "No.21". While it is still relatively new it will be another locomotive being broken up.