UPPER TRAY INSTALLATION PROCEDURE | Tower Internals in Plants & Refinery
a. Prerequisite
✓ Bed below is loaded and beams have been installed with special
care regarding perpendicularity (refer to chapter 8-e).
✓ The adequate dump-nozzle is open and air circulation IS m service.
✓ Panels of the tray have been prepared at ground as per procedure.
✓ Atmosphere inside the adsorber is breathable (no apparent dust).
✓ Support rings and top faces of beams are clean ( of any sieve particles or any other material).
V The Catapac apparatus and the support platform have been removed.
✓ Plugs from beams threaded holes have been removed and threaded holes in the beams do not present any damage and are clean.
b. Upper tray panels installation
✓ Install the panels following the procedure described for the lower tray.
✓ Tighten the stud bolts with washers.
✓ Remove the 15 mm thickness spacers progressively.
c. Tightness and bolting procedure for upper tray
✓ Pack the glass fiber rope in each space. Pay attention around each stud. Use smaller diameter rope when necessary.
✓ Check the horizontality and the flatness of the tray.
✓ Tack weld the seal angle plates on the welding ring of the shell.
✓ Install and GT AW weld the panel to panel seal plates.
✓ GT AW 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.
As for lower tray, an alternating welding scheme must be followed to prevent warping of the panels by localized hot points.
Figure 40: Upper tray panels installation.
d. Upper piping manifold installation
This operation must be performed after completion of tightness and bolting
of the tray.
✓ Introduce top piping manifold into the top head of the vessel.
✓ Install the gasket and tighten the inlet distributor box.
✓ Install preassembled piping between the inlet distributor box
and the corresponding panel nozzle.
✓ Use the piping GTAW welding procedure. Dye test all weldings.
✓ Connect the flushing line to the center-pipe.
✓ Blind the equilibrium device nozzle.
e. Center Pipe, Upper tray and piping manifold leak tests
i. General
✓ Those tests have to be performed with dry air.
Figure 41: Center Pipe, Upper tray and piping manifold leak test
ii. Center-pipe pressurization
✓ Install a temporary flange with an accurate pressure gauge and a valve connected to dry air on the top nozzle of the center-pipe.
Blind the bottom nozzle.
✓ Pressurize the center-pipe under dry air at 0.5 bar g. Leak test is satisfactory when the pressure decrease is lower than 0.05 bar/h over a period of 4 consecutive hours. Keep pressure on the center-pipe during the next steps.
iii. Leak test
✓ Check the equilibrium device nozzle is blind.
✓ Manhole is maintained open.
✓ Install a temporary blind flange equipped with an accurate pressure gauge on the pumparound inlet (the temporary blind flange already used for the lower tray leak test is already in
place on the pumparound outlet).
✓ Top head piping manifold is air-tested in the same time.
✓ Close the vent on the temporary flange of the pumparound inlet.
✓ Pressurize the bottom head and the vessel under dry air at 0.05 bar g.
✓ Check the integrity of the tray and of the top piping manifold by controlling the pressure local indicator. In case of loss of pressure, use a surface-active agent (soap solution) to detect the leakage.
✓ If any leakage is detected, paint mark it. Depressurize the vessel and repair the defective welding. Pressurize back the bottom head to check the repair.
✓ Perform these steps until the leak test is fully satisfactory.
iv. Vessel pressurization and mechanical resistance of the upper tray
✓ During this step no entry inside the vessel is allowed.
✓ Pressurize bottom head under dry air at 0.3 bar g. The whole
vessel except the top head will be air tested. The upper tray
will be air tested to a differential pressure of 0.3 bar. Test is
satisfactory when the pressure decrease is lower than 0.05 bar/h
over a period of 4 consecutive hours.
✓ Depressurize the vessel.
✓ Verify visually the mechanical integrity of the different pieces of the tray.
f. Top head closure
✓ Depressurize the vessel.
✓ Remove the blind flange and install the equilibrium device.
✓ Plug all nozzles of the top head.
✓ Connect internal piping to the equilibrium device (flushing and
sampling lines).
✓ Clean carefully the upper tray and the top piping manifold.
✓ Close the manhole.
Refer to appendix C for main AXENS inspection check point regarding upper tray.
ii. General leak test of the vessel
✓ Pressurize the vessel as previously at 0.1 bar g.
✓ Check the integrity of the vessel by controlling the pressure
local indicators. In case of loss of pressure, use a surface-active
agent (soap solution) on the different nozzles to detect the
leakage.
✓ If any leakage is detected, paint mark it.
vessel and repair the defective connections.
bottom head to check the repair.
Depressurize the
Pressurize back the
iii. Waiting position
✓ Blind adsorbent tower and place it under nitrogen blanketing
(0.1 bar g).