The DEstroyer Life EXtension (DELEX) refit was born out of the need to extend the life of the steam-powered destroyer escorts of the Canadian Navy in the 1980s until the next generation of surface ship was built.
Encompassing all the classes based on the initial St. Laurent (the remaining St. Laurent, Restigouche,  Mackenzie, and Annapolis-class vessels), the DELEX upgrades were meant to improve their ability to combat modern Soviet submarines, and to allow them to continue to operate as part of NATO task forces.

Nipigon underwent a DELEX refit in 1982 and Annapolis followed in 1984.
The Annapolis class received the same sensor and communications upgrades that others in the St Laurent family of ships received, including the installation of a new tactical data system (ADLIPS), updated radars and sonars, fire control and satellite navigation.
They also received the new Canadian Tactical Towed Array Sensor or CANTASS which was a long-range towed sonar array that was affixed to the stern, which replaced the older VDS.
The class also received a new lattice mast.
The AN/SPS-503 radar was installed, the AN/SPS-10D replaced the older, AN/SPS-10 model.
The AN/SQS-502, AN/SQS-503 and SQS-10/11 sonars were removed and replaced by AN/SQS-505(V) in a fixed dome below the waterline.
The installation of the two ADLIPS units allowed the vessels to better integrate into NATO units.

They were given 12.75-inch (324 mm) torpedo tubes to allow them to fire Mark 46 torpedoes.
However, the Limbo mortar was removed in order to install the CANTASS.
This visibly altered the overall appearance of the ships.
The AN/SQR-504 was also replaced by the CANTASS.
The Super RBOC chaff system was installed during the refit.
The DEstroyer Life EXtension (DELEX) refit was born out of the need to extend the life of the steam-powered destroyer escorts of the Canadian Navy in the 1980s until the next generation of surface ship was built. Encompassing all the classes based on the initial St. Laurent (the remaining St. Laurent, Restigouche,  Mackenzie, and Annapolis-class vessels), the DELEX upgrades were meant to improve their ability to combat modern Soviet submarines, and to allow them to continue to operate as part of NATO task forces.
Nipigon underwent a DELEX refit in 1982 and Annapolis followed in 1984. The Annapolis class received the same sensor and communications upgrades that others in the St Laurent family of ships received, including the installation of a new tactical data system (ADLIPS), updated radars and sonars, fire control and satellite navigation. They also received the new Canadian Tactical Towed Array Sensor or CANTASS which was a long-range towed sonar array that was affixed to the stern, which replaced the older VDS. The class also received a new lattice mast. The AN/SPS-503 radar was installed, the AN/SPS-10D replaced the older, AN/SPS-10 model. The AN/SQS-502, AN/SQS-503 and SQS-10/11 sonars were removed and replaced by AN/SQS-505(V) in a fixed dome below the waterline. The installation of the two ADLIPS units allowed the vessels to better integrate into NATO units.
They were given 12.75-inch (324 mm) torpedo tubes to allow them to fire Mark 46 torpedoes. However, the Limbo mortar was removed in order to install the CANTASS. This visibly altered the overall appearance of the ships. The AN/SQR-504 was also replaced by the CANTASS. The Super RBOC chaff system was installed during the refit.
Annapolis-class destroyer