Why would you put three sets of pinger detectors on one ship? Given there is a clock running before the batteries in the pinger run out, would you not put three detectors on three boats and cover as much ground/sea as possible?
You need at least 3 to triangulate the location, and pinpoint the location as quickly as possible. With a unit, you simply get direction. Relative strength is difficult to tell distance with thermoclines, etc.
With only one vessel, or one unit, it is very difficult to pinpoint the location. You have to drive, get a direction, then drive perpendicular to get direction, then parallel wide and combine the three to get a general location, if you have gone wide enough. Then start again to narrow down further...
You can deploy them from RHB from the mother ship, and these can usually get far enough away to triangulate, and narrow down an area.
This is in a perfect world. In reality, the currents, thermoclines, and salinity cause a signal to wander...