Reciting a second beracha when replacing tefillin that had been removed
According to the Mechaber, someone who removed his tefillin or moved them from their place on his head/arm must recite a new beracha upon returning them to their place, even if his intention was to reposition them immediately. According to the Rama, a new beracha is not required when they are put back in place. If the original beracha was recited with the intention of removing and replacing the tefillin, all agree that a new beracha is not necessary. If the tefillin were removed to use the restroom or to eat a seudas keva, all agree that a new beracha is required.
(סעיף יב, ס"ק מג ו־מז, וביה"ל ד"ה אם וד"ה ויש; ביאורים ומוספים דרשו, 56)