The 1.8k is used in the upper position (furthest form the tank) of the regulator on Pure Energy
HPA tanks.
It is absolutely essential that you ONLY replace failed units with exact replacements. Any subsitutions will void all warranties.
To replace a Unified Burst Disk Assembly, simply unscrew the failed unit, and discard it. They are NOT serviceable.
Screw in the new replacement unit and torque with torque wrench to 55 inch-pounds. Do not over-torque.
Burst Disks are designed to release excess pressure and prevent further damage from component failure. A blown burst disk is most likely due to another part of the system. Burst Disks carry no warranty. Consult a qualified air smith for further information.