Multipart frac head with replaceable components

A multipart frac head, comprising:

• a frac head body having a plurality of inlet ports and a bottom leg socket that comprises a box thread and a seal bore located inwardly of the box thread;
• a bottom leg removeably received in the bottom leg socket, the bottom leg comprising an inner end received in the seal bore and an elongated pin thread that cooperates with the box thread to secure the bottom leg in the bottom leg socket;
• and
• a lock nut threadedly secured to an outer end of the elongated pin thread, the lock nut being tightened against a bottom end of the frac head body to lock the bottom leg in the bottom leg socket.

A multipart frac head, comprising:

• a frac head body having a plurality of side entries that respectively retain inlet ports and a bottom leg socket that comprises a box thread and a seal bore located inwardly of the box thread;
• a bottom leg removeably received in the bottom leg socket, the bottom leg comprising an inner end received in the seal bore, the inner end cooperating with high-pressure seals in the seal bore to provide a high-pressure fluid seal around the bottom leg, and an elongated pin thread that cooperates with the box thread to secure the bottom leg in the bottom leg socket;
• a lock nut threadedly secured to an outer end of the elongated pin thread, the lock nut being tightened against a bottom end of the frac head body to lock the bottom leg in the bottom leg socket;
• and
• an adapter on a bottom end of the bottom leg for connecting the multipart frac head to wellhead or wellhead isolation equipment.