This article is about Installation and Sieve Loading Typical Activities Schedules, sieve analysis procedure, sieve analysis calculation formula and sieve analysis lab report.
Sieve Loading Typical Activities & Installation
a. Work Organization
Detailed schedule and work organisation for internals installation and sieve loading, has to be issued by Client and submitted to AXENS for approval. This must be done well ahead the start of internal installation and sieve loading.
This schedule should specify the name of each contractor, their limits of supply (Tasks to be perform by them and material they will supply to perform their tasks), their duties and their areas of responsibility.
In order to save time, sieve loading and internals assembly must be performed on both adsorbent towers in parallel. Sufficient personnel have to be foreseen in accordance with work organisation and schedule. As well lifting equipment’s and the required tools must be in sufficient quantity to assemble 2 trays simultaneously.
A meeting should be held on a daily basis in order to report the work progress, consumption and remaining quantities of the goods such as glass fiber rope (valid for all diameters), final gaskets, etc.. This daily scheduled meeting should allow to solve and anticipate any difficulties so as to find adjustments as necessary.
Read Also: Internals Installation & Sieve Loading | Tower Internals in Plants & Refinery
b. Typical Schedule for Installation and Sieve Loading
The estimated time necessary for all internals assembly and sieve loading is estimated to be about 10 weeks. This means that the installation work shall be performed in ~ 70 days from first Lower Tray up to the last Upper Tray, and last adsorber final closing included, provided the installation work is done on 24 hours basis and in parallel on both adsorbers.
These estimated durations do not take into account the possible time gap between two consecutive installation tasks, shift change duration, delay for rain, heavy fog or any contingencies for any possible troubles arising during the installation of internals and loading.
The time necessary to transport to the site the crates for panels, beams, piping and containers for sieve, Big bags weighting, panels ground inspection inside the panels shelter, ground cleaning for beams, piping and panels, etc.. is not taken into account. This is supposed to be done on hidden time.
In addition, three extra weeks on normal day time have to be planned for work preparation regarding all prerequisites (adsorbers inspection and center pipe centering, Catapac platform installation as well as positioning, installing the internal ladder, etc.. ).and tools before to
start lower trays installation.
i. Typical Activities for Lower Tray (Adsorber A or B) (Typical duration)
- Ground inspection for the panels and neoprene sheet installation.
- Angle plate welding on the adequate panels for Center Pipe blanket installation.
- Beams installation for lower tray with checking of levelness and flatness of the beams.
- Install panels with their protective neoprene. 20 hours
- Check panels horizontality and flatness. (30 hours)
- Panels bolting to the Lower Tray beams (Staples, clamps). (30 hours)
- Glass fiber rope installation. (24 hours)
- Lower Tray seal welding & DP tests. (48 hours)
- Beams installation for the tray above with checking of levelness and flatness of the beams. (18 hours)
- Install bottom manifold. (100 hours)
- Lower tray leak test (and reparations if any). (60 hours)
- Installation of Lower Tray equilibrium device and its piping. (06 hours)
- Clean the bottom head, final inspection of the bottom head & close bottom man hole. (18 hours)
- Remove top temporary bracing of center pipe & check dimensions for any deviation. (18 hours)
- Remove internal ladder from Lower Tray up to the bed above. (01 hours)
- Measuring all dimensions and radius after Lower Tray installation. (02 hours)
- Lower Tray final cleaning & final inspection & remove neoprene. (04 hours)
- Catapac in load position. (02 hours)
- Loading the bottom bed. (12 hours)
- Plywood bridges installation the and bed levelling flush with the above bed beams. (02 hours)
- Catapac in park position. (02 hours)
Total (409 Hours)
For both lower trays, as this are the first one to be installed, normally the workers need some time to find their normal adequation to this specific work. Considering this, some operations may appear to be longer than for others beds.
ii. Typical activities for Intermediate Tray (Adsorber A or B) Typical duration
- Ground inspection for the panels and neoprene sheet installation. hidden
- Angle plate welding on the adequate panels for Center Pipe blanket installation. hidden
- Install panels with their protective neoprene sheets. 12 hours
- Check panels horizontality and flatness. 6 hours
- Glass fiber rope installation. 10 hours
- Beams installation for the next tray with checking of levelness and flatness of the beams. 10 hours
- Piping leak test. Hidden
- Internal piping installation. 8 Hours
- Center pipe tightness blanket installation. 3 hours
- Thermocouples installation (for beds 1, 6 and 11 only). 1 hours
- Clips installation and welding. 2 hours
- Measuring all dimensions and radius after Lower Tray installation. 1 hours
- Intermediate Tray final cleaning & final inspection & remove neoprene. 6 hours
- Catapac in load position. 1 hours
- Loading the bed. 12 hours
- Plywood bridges installation the and bed levelling flush with the above bed beams. 2 hours
- Catapac in park position. 1 hours
- Typical time to install one intermediate bed. 73
- Total to install the intermediate beds (11 trays and 11 beds). 805 Hours
(*) Average duration based on installation of thermocouples on bed 1, 6 and 11 shared on the
global work duration for one complete set of intermediate trays installation for one adsorber.
iii. Typical activities for Upper Tray (Adsorber A or B). Typical duration
- Ground inspection for the panels. hidden
- Provision for fine adjustment of the upper tray beams and checking of threaded holes. 24 hours
- Install panels. 24 hours
- Check panels horizontality and flatness. 12 hours
- Panels bolting to the Upper Tray beams. 24 hours
- Glass fiber rope installation. 18 hours
- Upper Tray seal welding & DP tests. 48 hours
- Install top manifold. 80 hours
- Center-pipe and upper tray leak test (and reparations if any). 84 hours
- Installation of Upper Tray equilibrium device and its piping. 8 hours
- Upper Tray final cleaning & final inspection before closure. 10 hours
- Final closure. 6 hours
Total. 338 hours
Read Also: Lower Tray Leak Test Procedure | Tower Internals in Plants & Refinery
c. Potential causes for work delay versus schedule
i. Panel screen damaged by lack of attention or misoperation
Because screen is delicate and not easy to fix, maximum care has to be taken to avoid any screen damage.
Gap between V wires is process dictated and must not exceed 225 microns.
Risk:
✓ Increase of delta P in the adsorbers,
✓ Poor performances (yield decreased)
✓ Sieve in withdrawal streams
In case of screen damage the possible untoward consequences are:
✓ Sieve migration from top to bottom,
✓ Leak of sieve and shut down for unloading
Important repairs have to be done by the manufacturer only.
Repairs are possible outside the vessel before loading. Repairs once tray installation is started, even if possible would be very time consuming.
ii. Poor quality or not completed welding inside the vessel
The only welding phases during internal installation are related to lower and upper trays.
There are many welds of pipes inside the vessels for each of these trays and poor quality or not completed welding may have some consequences:
Risk:
✓ back mixing and poor performances (yield and purity decreased)
✓ Sieve in withdrawal streams
✓ Increase of Delta P for secondary streams
Possible untoward consequences:
✓ leak of sieve and shut down for unloading
✓ Cross pollution and shut down for unloading
This point is very difficult to detect before oil-in, except by a rigorous inspection during the internals assembly.
Do not hurry for any purpose: a proper assembly during installation will save time and money during operation
iii. Forgetting a temporary gaskets or forgetting to install one proper gasket
There are many flanges between pipes inside the vessels for each tray.
Temporary gasket replacement by proper one has to be carefully done.
In case it is not done correctly,
Risk:
✓ back mixing and poor performances (yield and purity decreased)
✓ Sieve in withdrawal streams
✓ Increase of Delta P for secondary streams.
Possible untoward consequences:
✓ Leak of sieve and shut down for unloading
✓ Cross pollution and shut down for unloading
This point is very difficult to detect before oil-in, except by a rigorous inspection and continuous count of temporary/final gaskets during the internals assembly.
Do not hurry for any purpose: a proper assembly during installation will save time and money during operation
iv. Damaged flexible hose
Risk:
✓ back mixing and poor performances (yield and purity decreased)
✓ Sieve in withdrawal streams
✓ Increase of Delta P for secondary streams
Possible untoward consequences:
✓ Leak of sieve and shut down for unloading
✓ Cross pollution and shut down for unloading
Very difficult to detect before oil-in, except by a rigorous inspection during the internals assembly
v. Foreign materials inside the panels, the internal piping or the annular chambers
Presence of foreign materials in the panels, the internal piping or the annular chambers represents a risk of plugging the distributors and/or damaging special ON/OFF valves.
In case of presence of foreign material:
Risk:
✓ delta P increases
✓ Bad distribution leading to poor performances
✓ foreign materials in withdrawal streams
Possible untoward consequences:
✓ Damaging to on/off valves
Impossible to detect except by a rigorous inspection during the internals assembly
vi. Rope packing dashing off
ln case of rope packing dashing off:
Risk:
✓ Increase of delta P in the adsorbers,
✓ Poor performances (yield decreased)
Possible untoward consequences:
✓ Sieve migration from one bed to another,
✓ Sieve damaging and shutdown for unloading
vii. Failing in the sieve loading
Dense loading with Catapac apparatus is required to load the proper quantity of sieve as the sieve quantity is an operating constant of the unit. Possible untoward consequences:
✓ Lack of sieve reduces the capacity.
Sieve loading has to be performed by a dense loading specialist
viii. lack of transparency between involved parties
Every body has to keep in mind that a mistake can be fixed more or less easily during the sieve loading and internals assembly.
Once oil-in has been performed, any intervention in the adsorbers would be heavy to handle.
In case of doubts of any kind, communication between involved parties will allow corrective actions to be undertaken for the benefit of everyone.
If Want More Information: Check out INSTALLATION OF ADSORBENT TOWER INTERNALS.