2. 37-Degree Flare. The 37-degree flare connection has a male straight thread that mates with a
female straight thread. The sealing surface for this connection is the angled nose at the end of
the male fitting. The nose mates with a similar surface in the female 37-degree flare fitting.
These sealing surfaces must be free of nicks and scratches to seal properly.
3. O-Ring (Preformed Packing) Boss. The boss connection has a straight thread. The seal for this
connection has a preformed packing that fits on top of the thread. This packing is squeezed in
the extra space at the top of the female thread and seals the connection.
4. Flareless. This fitting has a straight thread. The female fitting contains a ferrule that mates with
a cavity in the male fitting. Use care not to overtighten to avoid damage to the ferrule.
5. Installation of Preformed Packings.
a. Before installing a new packing, inspect threads and packing seat for nicks, cracks, and
b. Make sure the packing is correct type and size. If not sure, check Repair Parts and
Special Tools List (TM5-2420-224-24P).
c. Before installing a new packing, apply coat of lubricating oil to packing (Appendix C, Item 22).