Dual chamber orifice fitting plate support
Methods and apparatus for positioning an orifice plate within a body having a straight flowbore. One embodiment includes a carrier supporting the orifice plate and a drive member operable to engage the carrier and move the carrier along a first axis perpendicular to the flowbore. The drive member is also operable to limit the movement of the carrier along a second axis perpendicular to the flowbore and perpendicular to the first axis. A pin is operable to engage the carrier so as to limit movement along the first axis.
1. An apparatus for positioning an orifice plate, the apparatus comprising:
a body having a straight flowbore;
an orifice plate carrier moveably disposed in the flowbore, wherein the orifice plate carrier includes a pair of machined outer side surfaces; and
a drive assembly, the drive assembly comprising:
a rotatable shaft inserted though the body, wherein the shaft is rotatably coupled to the orifice plate carrier; and
a pair of stuffing boxes disposed between the shaft and the body, and coupling the shaft to the body;
wherein opposed inner ends of the stuffing boxes engage the pair of machined outer side surfaces of the carrier;
wherein:
the body includes two outer surfaces, each outer surface equidistant from a center of the flowbore as measured parallel to a first axis that is normal to a longitudinal axis of the flowbore;
the drive assembly includes a pair of gears disposed on the shaft, each gear rotatably constrained relative to the shaft;
the pair of stuffing boxes is concentrically disposed on the shaft, each stuffing box inner end engaging one of the gears, wherein each end is equidistant from one of the outer surfaces as measured parallel to the first axis;
a center of an orifice through the orifice plate is equidistant between the ends of the stuffing boxes as measured parallel to the first axis; and
rotation of the shaft displaces the plate carrier in a direction parallel to a second axis that is normal to the first axis and the longitudinal axis.
2. The apparatus of claim 1 wherein said gears engage teeth disposed on said orifice plate carrier.
3. The apparatus of claim 1 wherein said stuffing boxes are connected to the body and sealingly engage said shaft.
4. The apparatus of claim 1 , wherein each stuffing box comprises a machined length between the inner end and an outer end flush with one of the outer surfaces of the body that is machined to closely control engagement between the stuffing boxes and the carrier surfaces.
5. The apparatus of claim 4 , wherein the outer surfaces of the body, the side surfaces of the plate carrier, and the length of each stuffing box are machined, whereby the center of the orifice and the center of the flowbore are equidistant from the second axis and from the longitudinal axis.
6. The apparatus of claim 1 , wherein the stuffing boxes are removably threaded into the body and include inner bores for receiving the shaft.
7. The apparatus of claim 1 , further comprising a stop pin engaging the plate carrier, the stop pin movable to displace the plate carrier in the direction parallel to the second axis, whereby the center of the orifice and the center of the flowbore are equidistant from the first axis and from the longitudinal axis.
8. The apparatus of claim 7 , further comprising a spanner nut attached to the body so as to limit the movement of said stop pin.
9. The apparatus of claim 8 , further comprising a jack screw adapted to engage said spanner nut and move said stop pin.
10. The apparatus of claim 7 wherein said stop pin is sealingly engaged with said body.
11. The apparatus of claim 7 , wherein the body further comprises:
a lower chamber, wherein the drive assembly is disposed within the lower chamber; and
an upper chamber having an upper drive member disposed within the upper chamber and operable to engage said orifice plate carrier and move said orifice plate carrier between the upper and lower chambers.