Foundation types explained for industrial plants foundations, tank foundations, substation, control room etc. training and consultancy provider
Tank farm & Tank foundations
What is a tank farm?
it is a collection of tanks with/without a dyke wall.
- Classification of tanks:- hazardous & non-hazardous.
- Tanks storing same liquid are housed together within a common dyke wall.
- The dyke wall system may be designed for failure of the largest diameter tank.
- Access to the dyked area: these are called crossovers. either brick steps or steel staircase can be provided.
- Pump area: this is normally outside the dyked area. this is a paved area with pump foundations.
- Location of tank farms: This is decided by layout group considering statutory requirements for safe distances between structures.
Tank foundation types
- Earthen pads
- Ring walls
- RC deck slab with columns - isolated / raft
- RC deck slab with piles
- RC walls supported on RC strip footing/raft
This is decided by the size of the tank, soil parameters, the requirement of inspection access below tank bottom etc. Slope at top of foundation to be provided for tank draining as required by mechanical
- Earthen pad foundations - This is possible when the sub-grade has the adequate bearing capacity.
- Ringwall type foundation - Crushed stone ring wall / RC ring walls.
Dyke wall:- The dyke wall system may be designed for failure of the largest diameter tank. The height of dyke wall & the spacing of tanks is decided by layout group. Moc of dyke walls can be brick masonry, RCC, R R . masonry. The foundation of dyke walls can be strip footing for brick / RR masonry. Columns with isolated foundations with wall spanning between columns can also be provided. One can provide RCC retaining wall when founding strata is near ground level. Paving inside dyke wall can be RCC grade slab/gravel/asphalt surface/graded earth. Acid resistant .lining with RC. paving could also be provided depending on the nature of spillages from the tanks.
Proper attention shall be given for drainage from dyked area and suitable sump pit shall be provided.
SUBSTATION / CONTROL ROOM
The function of the Substation is to receive the power from main grid through transformers and distribute the same to various units of plant as per load requirements, through switch gear and MCC Generally, sub-station consists of Transformer Room / Bay, Oil Drain Pit, DG Set Room, Switchgear Room / MCC Room / UPS & variable speed drive PNL room, Cable Cellar Room, Battery Room for UPS / Lead Acid Batteries, AHU Room / A.C. Room, MCC pressurization room, Engineer’s Room, Office Room, Toilets & Store Room.
Substation can be the G+1 or G+2 structure with or without the control room. When the substation is along with control room, then control room is generally provided on the 1st floor or above the substation.
• Two type of transformers – Oil type and Dry type as per power requirement and space availability
For Oil type transformer
Open RCC framed structure with minimum 350 mm thick brick wall or 200 mm thick RC wall is provided (For 2-hour fire rating). This wall should be for transformer floor only. The front face is provided with chain link fencing and MS Gate for access. Transformers
are kept on raised foundations generally 500 mm above FGL. RCC trenches as required are located around the transformer foundation. After laying the cables, trenches are generally filled with sand up to the top & pre-cast RC cover is provided. This procedure prevents spreading of fire which may occur during accidents. About 100 to 150 mm thick layer of gravel is provided all round the transformer bay to take care of oil spillage which may result due to transformer failure. The gravel layer will prevent the collection of oil on the surface of the floor of transformer room/bay, thus reducing the risk of fire. A burnt oil drain pit may be provided by considering discharge with gravity.
CONTROL ROOM BUILDING
The building is meant to house systems to monitor and control the complete operations of the process plant form a centralized location. The measurement and control of process variables in the various plant sections including fire alarm/plant safety and
emergency shut down of the plant are affected by the control room. Control room building, being the heart of the plant, is generally designed with Proper architectural treatment, providing the right ambiance, both within and outside, for good operation of the
plant. In control room, minimum headroom from false floor to false ceiling should be 2.5m. The minimum distance between any two hazardous plant buildings (including control room building) is generally 15m out to out. Non-compliance with any of the safety distances will call for the provision of blast-proof type design of external walls including blast resistant doors (including fire resistant property).
Design data & Co-ordination with Up-stream departments
• Minimum values of live load
• Switchgear room, MCC, battery room 10 KN/m2 (including wt. of panel/batteries)
• False floor in switch and MCC room 3 KN/m2 (as eqpt./panels are not supported by false floor)
• Offices and auxiliary rooms 3 KN/m2
• Instrumentation and control room 5 KN/m2 (including wt. of cables/instrument)
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