A difficult query for me
You need to first isolate the rows with 'ABIERTO' and 'CERRADO' and then do a FULL JOIN between them. Since MySQL has not implemented FULL join, there are various ways to achieve such a join. We will need the distinct values of (key, point_name) pairs, so the easiest way seems to be to get first these values and then do two LEFT joins, one to 'ABIERTO' and another to 'CERRADO' values:

SELECT
    d.point_name AS equipo,
    a.time       AS abierto,
    b.time       AS cerrado
FROM
    ( SELECT DISTINCT `key`, point_name
      FROM alarms_9_2015
    ) AS d
  LEFT JOIN
    alarms_9_2015 AS a
      ON  a.value = 'ABIERTO'
      AND a.key = d.key
      AND a.point_name = d.point_name
  LEFT JOIN
    alarms_9_2015 AS b
      ON  b.value = 'CERRADO'
      AND b.key = d.key
      AND b.point_name = d.point_name
ORDER BY
    COALESCE(a.time, b.time) ;


A composite index on (key, point_name, value) would improve efficiency.