LOWER TRAY INSTALLATION SEQUENCE
a. Prerequisites
✓ Adsorbent tower, center pipe and annular chambers inspections relative to dimensional and cleanliness aspects are successfully achieved.
✓ Adsorber first inspection scaffolding has been dismantled and only bottom head platform (refer to fig 15 on page 59) is remaining in place.
b. Lower tray beams installation
✓ Prepare at ground the beams of the tray.
✓ Install the beams beginning by the 2 main ones.
✓ Then continue installation following the typical beams installation sequence.
Figure 25: Lower tray beams installation sequence.
✓ Adjust the levelling of the beams using the various thickness shims. Adjust the relative position between beams.
✓ Bolt the beams to the different supports.
✓ Check the fastening, the horizontality and the flatness of the beams.
✓ Tack weld all potential moving parts: bolts, shim plates …
✓ Punch mark the beams once the complete set is in position.
c. Lower tray panels installation
✓ Support rings and top faces of beams must be clean.
✓ Panels can be installed inside the vessel following the typical panel installation sequence.
Figure 26: Lower tray panels installation sequence. Install the first panel.
✓ Adjust the position of the first panel to equalize the distance between panel frame and beams axis on each side
Figure 27: First panel positioning
✓ Adjust panel to panel clearance using 15 mm thickness spacers. Shift panel with crowbars and block them with screw clamps. Remaining space will be packed on the periphery.
Figure 28: panel positioning using spacers and screw clamps.
d. Bolting and tightness procedure for lower tray
✓ Fasten the fork joints and the split pins to the plates located on the lower side of the panels. Install the panel to panel plates under the beam.
✓ Install the clamps fastening the round edge side of the panel to the support ring.
✓ Screw the nuts symmetrically in order to balance the strains (first panel to panel staples, then panel to support ring clamps).
✓ Check the horizontality and the flatness of the tray.
✓ Install the metallic wire rope and alternate rows of glass fiber rope. Packing to be performed according to the dedicated AXENS procedure.
✓ Install and GTA W weld the seal plates on the panels.
✓ GTA W weld the seal angle plates on the welding rings of the shell and center pipe and the tack welded plates of the round edge of the panel.
✓ To prevent warping of the panels by localized hot points, an alternating welding scheme must be followed. This scheme will be provided by the contractor in charge of internal assembly and submitted to AXENS’s approval.
Figure 29: Lower tray panels installation.
e. Lower piping manifold installation
This operation is very time consuming and must be prepared as far as possible outside the shell. It must be finalized in place after full completion of the lower tray assembly.
✓ Check the internal and external surfaces of the piping. In case of rust, piping must be brushed before introduction into the vessel.
✓ Install the piping using GTA W procedure.
✓ Connect the flushing line to the bottom of the center-pipe. After completion, a careful visual inspection of the weldings and a dye check are to be performed.
f. Lower tray and piping manifold leak test
Figure 30: Lower tray and piping manifold leak test.
✓ Mechanical resistance
• During this step no entry inside the vessel is permitted
• Check the equilibrium device nozzle is blind.
• Install a temporary blind flange on the pumparound outlet.
• Close the manhole and all the other nozzles located on the bottom head.
• Pressurize bottom head under dry air at 0.3 bar g. Maintain 2 hours.
• Depressurize the bottom head.
• Verify visually the mechanical integrity of the different pieces of the tray.
✓ Leak test
• Pressurize bottom head under dry air at 0.1 bar g.
• Check the integrity of the tray by controlling the pressure local indicator. In case of loss of pressure, use a surface active agent or leak detector.
• If any leakage, locate it. Depressurize the head and repair the defective weld. Pressurize back the bottom head to check the repair.
• Perform these steps until the leak test is fully satisfactory. According to this procedure, the piping manifold is air-tested from the outside at the same time but the tightness of the piping may be questionable if the loss of pressure is coming from the panels themselves.
g. Bottom head connection
✓ Remove the blind flange and install the equilibrium device.
✓ Connect internal piping to the equilibrium device (flushing and analysis points).
✓ Dismantle the scaffolding.
h. Bottom head final inspection
✓ Clean carefully the head and internal manifold before closure.
✓ Inspect the bottom head.
Inspection will be performed following the AXENS issued check-list.
✓ Close the manhole flange.
i. Intermediate trays beams installation
✓ Prepare at ground the beams of the tray.
✓ Install the beams beginning by the 2 main ones.
✓ Then continue installation following the typical beams installation sequence.
Figure 31: Odd Intermediate trays beams installation sequence.
✓ Adjust the levelling of the beams using the various thickness shims. Adjust the relative distance between beams.
✓ Check the horizontality and the flatness of the beams.
✓ Punch mark the beam once the complete set is in position.
j. Lower tray final inspection
✓ Clear out the tray.
✓ Clean the neoprene sheets with a vacuum cleaner.
✓ Remove the neoprene sheets.
✓ Clean perfectly the panel screen.
✓ Inspect carefully the screen and the tray following the AXENS issued check-list.
✓ Once all the materials are get off, make an inventory to make sure nothing has been forgotten inside the vessel.
✓ Remove bottom part of the center pipe ladder.
Refer to appendix A for main AXENS inspection points regarding lower tray.