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Galaxy Tanks ­ Ring Beam Site Preparation Requirements

1. Introduction · The Galaxy range of tanks requires certain basic conditions to be met in the preparation of the site, which are the responsibilities of the buyer. These conditions are given below, but should there be any confusion, please contact Galaxy Africa directly. · A concrete ring beam is required for tanks above a certain size, for commercial tank installations and in cases where the site conditions are not suitable for the direct installation or sand bed method. 2. Initial Preparation · A level area 2 metre larger than the tank diameter is required for the correct siting of the tank. Ensure that no vegetation is allowed within this area. · If the site is a "cut and fill" on sloping terrain, the cut must be sufficient to ensure that the tank is sited on the "cut" section only and does not overlap onto the "fill" section. (See Figures 1 & 2 below).

Figure 1: Incorrect tank siting WRONG


Figure 2: Correct tank siting RIGHT


Retaining Wall



FILL 1m 1m

TANK Drain


Sufficient clearance of at least 1 metre must be left between the "cut" bank and the tank. Provision must be made for an adequate retaining wall as indicated in Figure 2 as well as drainage to prevent collapse of the "cut" bank into the tank wall. Failure to do so will invalidate the guarantee.

3. Ring Beam Layout · Once the area has been cleared and levelled, determine the point where the centre of the tank will be. · Drive a rod into the ground at this point to serve as the datum point during the ring beam construction. (Note: the installers will also use this datum point when they arrive on site, so please do not remove). · The following method of ring beam construction is not the only acceptable method, but is proposed as a basic method. Experienced contractors may well have their own method for achieving the desired levels and accuracy. · Using this centre point as reference, mark out the inner and outer perimeters of the ring beam on the ground in accordance with the specified dimensions as shown in Figure 3 below. Document No: GA/RB003 Issue: 01 Date: January 2007


Figure 3: Marking of perimeters

Tank position Outer d Centre datum R1 R2 Inner edge

· ·

Excavate the ring beam to the specified ring beam depth less 100mm (the height of the ring beam above ground) between the marked lines. Also excavate the scour pipe trench at this stage. Place the first shuttering support (see Figure 4) in position on the outer edge of the trench and secure in place as shown in Figure 7. (Check that the distance from the centre datum point to the vertical of the shuttering support is correct, i.e. correct radius plus shuttering thickness). Figure 4: Laying out the supports

1 +/- 600mm Trench

Figure 5: Joining the shuttering

Rebar pin


Plan view

Figure 6: Side view of supports & trench


25MPa concrete Reinforcing not shown

Shuttering 150mm deep minimum Trench depth = Ring beam depth less 100mm


Place further shuttering supports around the outer perimeter approximately 600mm apart until all the outer perimeter supports are securely in place. Issue: 01 Date: January 2007

Document No: GA/RB003

3 · · · Using a dumpy (or laser) level placed at the centre datum point, find the shuttering support that is at the lowest point on the perimeter. Call this support No 1. Mark out a line on the vertical arm of the support 100mm above the level of the ground at the support. Use the dumpy (or laser) level to transfer this reference mark to the vertical arms of all the outer perimeter supports with the aid of an assistant. These marked lines give the position of the top edge of the shuttering board (either 6mm tempered hardboard, or 2mm mild steel plate). The shuttering board should now be fastened in position to the vertical arms of the shuttering supports with either screws or nails. The ends of each length of shuttering should be butted together at a shuttering support as per Figure 6. When all the outer perimeter shuttering is complete, check with the dumpy level that the top edges of the shuttering all round the perimeter is within 3mm of the reference mark at support No 1. Place the inner shuttering supports in place opposite the outer supports and pin down as before. Use a spirit level to transfer the reference marks from the outer supports to the inner supports. Fasten the inner shuttering to the supports as before, and again check the tolerances are within 3mm on completion.

· · ·

4. Ring Beam Construction · The ring beam reinforcing may now be conveniently laid out on top of the shuttering by placing short planks across the shuttering supports at various points around the circumference. (See Figure 7), and assembling the 4 lengths of Y-12 with the R-8 stirrups on these temporary planks until the reinforcing structure is complete. · With the help of assistants, remove the supporting planks and lower and fix the reinforcing structure in place in the ring beam trench as per Figure 8. · Figure 7: Assembling reinforcing

Y-12's R-8 stirrup Temporary support plank

Figure 8: Reinforcing in position

Oil inner faces well (used oil is OK)

· · · · · · · ·

Fit a sleeve of the specified size for the scour pipe through (or under) the reinforcing structure at the correct height. Once this is complete, perform a final check on the ring beam shuttering heights with the dumpy and spirit levels in case one or more of the supports has been accidentally knocked out of position. Mix the concrete (25Mpa minimum strength) and pour to the top level of the shuttering. Tamp or vibrate the concrete to make sure it fills the trench and does not leave any holes. Ensure that the finished top surface is level with the shuttering boards. Use the dumpy level and check that the top level of the beam is still within 3mm. The top surface of the ring beam must be level to better than 3mm across the entire top surface and ring beam circumference, and must be steel float finished (smooth finish, not foundation type finish). Chamfer and smooth the inner and outer top edges of the ring beam with a bull nosed trowel to eliminate any sharp edges, which could affect the integrity of the tank liner. The ring beam, when completed should be proud of the surrounding ground surface by 100 mm, both inside and outside the ring beam. (See the Figure 10). Issue: 01 Date: January 2007

Document No: GA/RB003

4 5. Internal Sand Bed · A bed of clean, debris and stone free building or screened river sand (2mm or smaller) must be placed inside the ring beam to form the bed on which the tank liner sits. · Lightly water and compact either by hand stamping or by using a plate compactor. Please note that compaction is important to maintain integrity of the tank after installation. · Note that failure to use the correct sand may result in long and costly delays if SBS have to rectify the situation!

6. Anti-erosion Control · Once the tank has been installed, a layer of coarse (approx. 30mm) aggregate must be placed around the perimeter of the tank as shown in Figure 10. This prevents erosion of the surrounds due to differing climatic conditions, animal intrusion and to assist water to drain away from the tank. The aggregate also helps prevent vermin from burrowing under the tank. · Typical suitable coarse aggregates are: - Crushed stone (25 - 40 mm) - Coarse crushed limestone - Rocks (50 ­ 100 mm) Concrete and slabs are not preferred.

7. General · Site preparation must be completed prior to the arrival of the installers. · For sloping tank sites, please make sure that adequate retaining and drainage is provided (see also the requirements for "cut and fill" sites) prior to and upon completion of the tank construction. In particular, care must be taken to ensure that run-off or rainwater cannot pool around the ring beam. · Galaxy Africa guidelines have to be met to prevent additional charges for the cost of any remedial works that may be required, or in the event of our installers having to stand down because of any delays or incomplete sites. · Should the ring beam and sand bed not be properly prepared by the time our installation team arrives on site, a waiting time charge will be levied whilst the situation is rectified. · If the installation team has to return on another date or lengthen their stay on your site overnight due to non-availability of the site, a charge for time, subsistence and transport will be made over and above any other quoted charges. The above guidelines have been given to ensure that minimum standards are met. Any variations from the above may delay installation or invalidate the guarantee Galaxy Africa will be pleased to offer a quote for either the construction of the ring beam, or to layout and supervise the construction for you. Please contact Galaxy Africa if you have any concerns or queries regarding installation of the tank.

Document No: GA/RB003

Issue: 01

Date: January 2007


Fig 9: Marking out of ring beam inner and outer positions using a rope, centre peg and marker

Fig 10: Excavating to required depth and width as per tank report table

Fig 11: Inserting shuttering prior to fixing ­ note that shuttering will be curved when fixing

Fig 12: Reinforcing sections assembled externally prior to installing in the shuttering

Fig13: Reinforcing installed in shuttering. Support the reinforcing 50mm above trench bottom. Note shutters now bolted and pegged in place.

Fig 14: Finished ring beam, correctly shuttered, levelled and constructed

Document No: GA/RB003

Issue: 01

Date: January 2007

6 Figure 15: Typical Ring beam details

100mm thick, uniformly graded sand pad

Tank wall

Chamfer internal edge Aggregate

Ground level

See tank report

R8 Stirrups at 600mm (SABS 82, Shape code 60)


4 x Y-12 See tank report Concrete Ring Beam, 25Mpa min

Edge of Tank

1m x 1m Centre Footing (if required)

Scour drain, pipe and sleeve (Sleeve must be at least 25mm larger internal diameter than scour drain)


A Concrete ring beam footing

Ring Beam Inner Diameter

Ring Beam Outer Diameter Document No: GA/RB003 Issue: 01

Plan View

Date: January 2007


Microsoft Word - Galaxy Ring Beam Prep Doc # 01

6 pages

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