The P6KE22ARL: No official successor is listed on the record, so any BOM line using this part will need a form-fit-function substitute or a last-time-buy inventory bridge.
That energy rating tells you the device can absorb a single surge of that magnitude without failing – useful for clamping transients on 12V or 24V DC rails where the reverse standoff voltage is 18.8V. The clamping voltage at peak pulse current is 30.6V, which is the maximum voltage the downstream circuitry will see during the event. For a 20A (8/20µs) pulse, the clamp stays under that ceiling.
Breakdown and clamping window – selecting the right rail
The minimum breakdown voltage is 20.9V, meaning the diode starts conducting between 20.9V and the clamping ceiling. The reverse standoff of 18.8V is the maximum DC voltage the part can sit across without conducting – so it fits on a nominal 18V rail or lower. If your rail is 24V, the standoff is too low and the diode would leak or conduct continuously; you would need a higher-voltage variant in the P6KE family.
T-18 axial package – through-hole retrofit considerations
The package is Axial, a through-hole form factor with leads on both ends. Mounting type is Through Hole.