CRITICAL INSTALLATION POINTS ABOUT TRAY ASSEMBLY IN TOWER

CRITICAL INSTALLATION POINTS ABOUT TRAY ASSEMBLY IN TOWER

Respect of fabrication tolerances, cleanliness, quality of work done inside the adsorbers etc … are critical points to succeed in the trays assembly. The following points have to be checked and followed carefully from the beginning to the end of the installation process.

Regarding Adsorbent Towers shell and associated annular chambers tolerances, AXENS highly recommend these items to be completely manufactured and assembled at shop. Assembly on site is most of the time not adequate in particular in terms of tolerances, roundness etc.. For these reasons the following recommendations are assuming that the Adsorbent Towers and Annular Chambers manufacturing and assembly have been done at shop.

a. Critical points related to status of equipments before shipment

i. Vessels at manufacturer shop before shipment

Vessel manufacturer is responsible for adsorbent tower shells, center pipes, all beam supports and support rings on each adsorber. Annular chambers and immediately connected flanges are also included in vessel manufacturer scope of supply.

(1) Adsorbent towers shell

✓ Overall sizes of the vessels to be checked at shop and be within the tolerances.
✓ Roundness of the shell should be checked
✓ Each nozzle and connection on the vessel to be blind, with proper flanges and proper gaskets.
✓ All surfaces must be perfectly clean inside and outside of the adsorbers: no scales, particles, rust, barbs, sand, dust is allowed.

✓ Surface treatment for vessels :
• Vessels are protected by surface treatment in order to protect them during storage under normal conditions and during sieve loading.
• Procedure to be defined by vessel manufacturer and reviewed by AXENS for comments

(2) Center Pipe

✓ Roundness and straightness of the center pipe to be checked.
✓ Each nozzle and connection on the Center Pipe to be blind, with proper flanges and proper gaskets.

✓ Temporary, light and adjustable beams shall be installed to prevent warping of the center-pipe during transportation. They must compulsorily have cylindrical-shaped cross-section. The temporary beams will be installed at least at two levels. One in the middle and one on the top. Typically three temporary adjustable beams are installed at 120°. This temporary support beams will be used and potentially adjusted while checking the centering of the Center Pipe. As these temporary beams will be kept in place during internals installation, no beam is allowed in the axis of the top head manhole.

Avoid in all the case welding of the temporary beams, which maintain the center pipe during the steps of transportation and internals installation, either on the vessel or the center pipe; they have to be completely removable without any trace anywhere.

✓ Center-pipe installed horizontally with its skirt. Even in horizontal, the centering of the Center Pipe, compare to the  center of the inlet P/ A nozzle, will be checked and potentially  the temporary beams will be adjusted.
✓ All surfaces must be perfectly clean inside and outside of the adsorbers: no scales, particles, rust, barbs, sand, dust is allowed.
✓ Surface treatment for vessels :
• Vessels are protected by surface treatment in order to protect them during storage under normal conditions and during sieve loading.
• Procedure to be defined by vessel manufacturer and reviewed by AXENS for comments

(3) Beam supports and support rings

1. Support rings welded on shell and center-pipe.
2. Proper welding of the beam supports on shell and Center Pipe
3. It will be checked that no welding would be susceptible of interfering with the panels, beams, installation. The width of the weld cordon will be such that the panels and beams could be placed as they are needed to be.
4. Levelness, horizontality and flatness of rings on both shell and center pipe. Level of beam supports on shell and Center Pipe. As parts of the adsorbent towers, rust prevention treatment used for vessels is applicable to these items.

(4)Annular Chambers

1. Tightness of annular chambers
2. Number, diameter and orientation of nozzles shall be checked at shop.
3. Each nozzle and connection to be punch-marked according to punch marking philosophy.
4. Connections have to be plugged.
5. Make sure there is no foreign material inside the annular chambers. If any, it shall be removed and perfectly cleaned. Special device to be provided by vendor to be able to go inside the annular chamber from each nozzle.
6. All surfaces must be perfectly clean inside and outside of the annular chambers: no scales, particles, rust, barbs, sand, dust is allowed.
7. As parts of the adsorbent towers, rust prevention treatment used for vessels is applicable to annular chambers.

ii. Panels at manufacturer shop before shipment

Tray manufacturer is responsible for tray panels supply and associated piping (for intermediate, lower and upper trays) as well as support beams.
✓ Overall sizes of the panels to be checked at shop and be within the tolerances.
✓ Horizontality and flatness of each tray panel should be checked on several points with special measurement device.
✓ Rocking of all panels is checked to be nil or minimized.
✓ No warping of the panels is allowed. The frame, which will be in contact with the support rings or the support beams, shall be perfectly plane.
✓ Each panel will be punch-marked according to punch marking philosophy.
✓ All surfaces must be perfectly clean inside and outside of the internals: no scales, particles, rust, barbs, sand, dust is allowed.
✓ Surface treatment for all trays:

• Trays are protected by surface treatment in order to protect them during storage under normal conditions and during sieve loading.
• Procedure to be defined by tray manufacturer and reviewed by AXENS for comments

✓ Special attention shall be given to the welding of the panels of Lower Tray and Upper Tray, especially in the corners side. The weld cordon shall be complete and no leakage is allowed due to improper welding.

✓ The holes pattern in the Upper Tray panels shall be checked to make sure they will perfectly match with the corresponding threaded holes on the corresponding support beams.
✓ After final inspection following an AXENS’s issued check-list, trays are immediately prepared for shipment.

• Panel connections have to be plugged
• Each panel is packed up in a seal tight plastic bag with desiccant to avoid any entry of humidity which will lead to rust. If rust is present, it becomes very difficult to get rid of it, especially inside the panels nozzles and panels internal parts.
• Panels for one or half a tray to be gathered into one wooden crate.
• Tools and accessories required for tray assembly on site will be packed into a special crate. Tools and accessories will be provided by the panels supplier.

iii. Internal piping at manufacturer shop before shipment

✓ Each piping element will be punch-marked according to punch marking philosophy.
✓ Make sure there is no foreign material inside the pipes.
✓ All surfaces to be perfectly clean inside and outside, no scales, particles, rust, barbs is allowed.
✓ Surface treatment for all piping:

• Piping is protected by surface treatment in order to protect it during storage under normal conditions and during sieve loading.
• Procedure to be defined by piping manufacturer and reviewed by AXENS for comments.

✓ During fabrication, special attention will be taken for all necessary welding, which shall be GT AW as per AXENS recommendations. Welds cordon shall be totally completed. All welds to be checked by ND test (Supplier to issue the procedure to AXENS for approval).

• After fabrication and final inspection, piping is immediately prepared for shipment.
• Piping for one tray is packed in a seal tight plastic bag with desiccant to avoid any entry of humidity which will lead to rust. If rust is present, it becomes very difficult to get rid of it, especially inside the piping.
• Protective plastic covers around the flexible hoses of the intermediate tray piping must be provided.

iv. Support beams at manufacturer shop before shipment

Horizontality and flatness within tolerances.
✓ Beam length, main and secondary to be checked for all beds.
✓ Upper face and carrying faces must be machining cut.

• V The threaded holes in the Upper Tray support beams shall be checked to make sure they will perfectly match with the corresponding holes pattern on the corresponding support tray panels.
• Threaded holes in support beams for the upper trays to be plugged with a proper threaded (plastic) stud easily removable.

✓ All surfaces to be perfectly clean, no scales, particles, rust, barbs is allowed.

Surface treatment:

• Beams are protected by surface treatment in order to protect them during storage under normal conditions and during sieve loading.
• Procedure to be defined by beams manufacturer and reviewed by AXENS for comments.
V After fabrication and inspection, beams are immediately prepared for shipment.

• Support beams for one tray is packed in a seal tight plastic bag with desiccant to avoid any entry of humidity which will lead to rust.

b. Critical points related to work done before tray installation

All the following points have to be checked on site prior to start tray installation. Should any deviation be found, the vendor shall give a corrective procedure, either for the nozzle or for the fitting of the piping.

i. General

✓ Once on site, the crates (with piping, beams and panels) will be stored inside a warehouse, and if not possible, they would be heightened from the ground to be protected from any water/rain accumulation and properly protected with tarpaulins or any other means to protect any rain/water to enter inside the crates.
✓ Overall sizes of the vessel and of the internals to be checked on site after erection and during the centering trial of the Center Pipe.
✓ Roundness of the vessel to be checked on site after erection and during the centering trial of the Center Pipe.
✓ Roundness, straightness and centering of the center pipe to be checked on site after erection, during the inspection of the adsorbers, prior to start Lower Tray installation.
✓ Number, diameter and orientation of the nozzles might be rechecked on site after erection to vertical position.
✓ Proper welding of the beams support,
✓ Proper welding of the support ring on the shell and on the center pipe. (The weldings shall not prevent to properly install the panels)

✓ Line-up, horizontality and flatness of the tray support rings on the shell and on the center-pipe.
✓ Line-up of the beam supports on shell and center-pipe for the main beams
✓ Rocking of all panels is checked. At shop it shall be nil or minimized.

ii. Cleanliness

✓ All surfaces (visible or not) of all equipments must be perfectly clean before any assembly: no scales, no particles, no rust, no barbs …
✓ Make sure there is no foreign material inside the annular chambers. If any, it shall be removed and perfectly cleaned using vacuum cleaner and special devices provided by vendor.
✓ Make sure there is no foreign material inside the pipes.
✓ At reception threaded holes in support beams for the upper trays should be plugged with a proper threaded (plastic) stud easily removable.
Threading cleanliness and proper machining have to be checked.
✓ No rust shall be present inside the adsorbers. Presence of rust leads to an important loss of time when getting rid of it. Potentially on site sand blasting would be required depending of the thickness of the rust layer.

iii. Protection against corrosion

• Surface treatment at shop using rust preventive is mandatory for vessel and on all the internals (Panels and piping) to prevent any rust formation, up to the end of the sieve loading.
• Potentially, if rust is detected during the inspection of the adsorbers prior to start the internals installation, cleaning will have to be performed and rust preventive will have to be added, prior to start any installation work inside the adsorbers.
• It is mandatory to keep the adsorbers under N2 all the time from shop to site and during the erection, until they are open for first on site inspection. If for any reasons, external nozzles shall be open, then the N2 blanketing will be lost. It shall be repressurized as soon as possible, otherwise rust will appear on the inside of the adsorbers.
• From the first on site inspection up to final closure, dry air shall always be supplied to the inside of the adsorbers to avoid any humidity inside leading to rust formation.

iv. Welding procedures

For any kind of weld inside the vessels, full GTA W is required. In case of any weld to be done or redone on the adsorbers shell or center pipe, the relevant vendor shall be contacted to get its advises on the proper welding procedure in application of mechanical codes and on the non destructive tests to be performed, like MPD (magnetic particles distribution), or any others ND tests.
Welding procedures to be defined by contractor and reviewed by AXENS for comments before tray manufacturing.

c. Critical points related to work during tray installation

i. General

The following points have to be checked before panel introduction in the adsorbent towers and once the panel is in position.
✓ Line-up of the beam supports on shell and on main beams, for the secondary beams installation.
✓ Horizontality and flatness of beams and panels.
✓ Horizontality and flatness of each tray checked on several points by a special level measurement.
✓ Rocking of all panels.
✓ Gaps between the panels themselves and between the panels and the shell and the Center Pipe shall be checked. These gaps  shall be such that the provided rope diameter will fit in for tightness.
✓ Integrity of screens on both sides concerning the panels of intermediate trays and one side for the Lower Tray and Upper Tray.
✓ To avoid damaging the screens, protective neoprene sheets will remain on the upper side of each panel after installation, until final cleaning and final inspection is done prior the sieve loading. These neoprene protections will be put in place on site during the panels ground inspection.

ii. Tightness

Several kind of tightness have to be ensured for the performances of the adsorbent towers.
Tightness of trays to the sieve thanks to rope packing and profiled wire screens.
Tightness of annular chambers and internal piping.
Tightness to the sieve and to the liquid of lower and upper trays.

iii. Cleanliness

All surfaces (visible or not) must be perfectly cleaned before
any assembly: no scales, no particles, no rust, no barbs …

iv. Protection against corrosion

✓ During the first on site inspection and up to final closure, dry air shall always be supplied to the inside of the adsorbers to avoid any humidity inside leading to rust formation.
V Panels and internal piping must be unpacked gradually just before lifting into the vessel. This is done on site. Potentially, if rust is detected during the unpacking, cleaning will have to be performed and rust preventive will have to be added, prior to start installation work of such rusty panels or piping, inside the adsorbers
Outside and inside work must be stopped in case of rain or  heavy fogs or sand storm, etc … No rain, no water, no sand, no dust is allowed to go inside the adsorbers. In case of slight mist the work could be pursued inside the adsorbers provided a proper shelter is installed on top of the adsorbers to prevent any
mist to enter in the adsorbers.

v. Welding procedures

For any kind of weld inside the vessels (seal plates and angle bars of lower and upper tray, shim plates, etc … ) full OTA W is required. In case of any weld to be done on the adsorbers shell or center pipe, the relevant vendor shall be contacted to get its advise on the proper  welding procedure and on the non destructive tests to be performed, like MPD (magnetic particles distribution), or any others ND tests. Welding procedures to be defined by contractor and reviewed by AXENS for comments.

The root pass and the last pass of field welds will be visual and dye checked. This check is done by skilled representatives either from vendor or from owner, in presence of AXENS as witness.

d. Tolerances

Tolerances concerning the vessels, the panels and the trays once installed are reported in the Process Data Book and shall be confirmed by vendors and all deviation must be submitted to AXENS for approval.