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56 Measurement Piston and Flow Tube
Section 4: Maintenance Operating and maintenance instructions
January 2015 3-9008-701 Rev J
10. Slide the measurement piston into the flow tube up to the upstream seal. Lubricate the
upstream seal with light oil. If the upstream seal is installed correctly, the seal should
slip into the flow tube when gently pressing on the piston.
11. Press the measurement piston into the flow tube until the second rulon rider groove is
about to go into the flow tube. Install the second rider onto the piston with the gap at
the bottom of the piston. Lubricate the rider with light oil.
12. Press the piston into the flow tube past the second rulon rider and up to the
downstream seal. Lubricate the downstream seal with light oil. Gently press on the
poppet until the downstream seal slips into the flow tube.
13. Using a flashlight, look through the hole in the inlet flange where the optical detector
shaft goes through. Check the alignment of the threaded mounting boss on the piston.
The boss must be aligned with this hole in the inlet flange for correct installation of the
detector shaft. Rotate the piston if necessary to align the boss.
14. Remove the guide conduit from the actuator shaft. Pull the actuator shaft out from the
tee of the inlet flange until the piston is approximately half way inside the flow tube.
Recheck the alignment of the mounting boss on the piston with the hole in the inlet
flange for the detector shaft.
If realignment is necessary, the poppet must be used to ‘tap’ the piston into position. Pull on the
actuator shaft enough to open the poppet. Spin the actuator shaft, in the direction necessary
for alignment, when slightly pushing the poppet against the piston. This will make the poppet
‘tap’ on the piston and move the piston into alignment. It may be necessary to repeat this
procedure to align the threaded mounting boss correctly.
15. Install the detector shaft into the threaded mounting boss and tighten by hand. At this
point, it is recommended to install the optical seal support over the detector shaft. This
holds the piston in alignment for the remainder of the assembly procedures. See
Section 4.4.2 for optical seal support assembly and installation.
16. Install the o-ring in the groove of the outlet flange using lubricant to hold it in place.
17. Lift the outlet flange with a hoist and align it on the end of the flow tube. Insert four (4)
tie rods through the flow tube flanges that are diagonal from each other.
18. Install the tie rod nuts to the four tie rods and tighten them to pull the flow tube and
the outlet flange snug against the inlet flange. Pay attention to the o-rings in the end
flanges and be certain they remain in place. Care should be taken to avoid scraping
paint into the space between the flanges and the flow tube.
19. Install the remaining tie rods and nuts. Tighten nuts enough to bring the flanges and
flow tube together.
20. Check the alignment of the outlet flange with the inlet pipe flange. A standard level and
the installation studs (for the outlet flange) may be useful. Rotation of the outlet flange
will bring the bolt pattern into alignment.
21. Torque the tie rod nuts to the values specified in Table 4-2 for the proper prover size.
Torque all the tie rod nuts in a ‘criss-cross’ pattern.