Applications require:
Positive Shut-off
Verifiable -0- leakage
One valve versus:

 Bleed Valve

                                                1 plug & 2 seats/slip 
                                                         Seats/slips:
                                                                     - block up & downstream flow
                                                                     - provide positive shutoff
                                                                       - mechanical load not spring load
                                                                                         - no relieving seats like ball valves
                                                                                         - prevent product contamination

                                                                     - retract before turning
                                                                                         (fully retracted valve opened/closed)

                                                                     - no rubbing action like gate, ball valve
                                                                     - longer seal life/metal back up

                                                                                                                 DTR – manual bleed & thermal relief
                                                                     - standard
                                                                     - prevents cavity pressure buildup
                                                                     - automatic
                                                                     - relieve excess cavity pressure “upstream” 
                                                                     - not “downstream” like ball valve self relieving seats - dp > 25 psi
                                                                     - prevent actuator problems, i.e lockup

                                                        Bleed
                                                                    - verify seat/slip integrity