What the tool does
Bunding (the tank dike) that holds liquid spilled from outdoor above-ground tanks is governed by Article 119/2 of Turkey's Regulation on the Fire Protection of Buildings (BYKHY). For your tank arrangement the tool finds the bund volume the regulation requires, works out the net volume your bund dimensions provide, gives the minimum bund wall height and checks the tank-to-bund distance under 119/2-ğ. The result shows a section with the bund walls, tanks and the required liquid level.
Article 119/2: required bund volume
| Case | Bund volume | Clause |
|---|---|---|
| Tanks of the same size | Volume of one tank | 119/2-a |
| Tanks of different sizes | Volume of the largest tank | 119/2-a |
| Portable tanks | 75% of the total volume, or at least the volume of the largest portable tank | 119/2-b |
| Mixed storage | Sum of the volumes under (a) and (b) | 119/2-c |
| Crude oil, carbon disulphide | Total volume | 119/2-ç |
The portable-tank clause joins its two conditions with "or at least"; the tool takes the larger of the two (safe reading). Example: portable tanks totalling 8 m³ with the largest at 2 m³ give 0.75 × 8 = 6 m³. With three 50 m³ fixed tanks in the same bund, mixed storage needs 50 + 6 = 56 m³.
How the net volume is worked out
Guide Figure 119.2 shows the bund volume as side lengths times height. In a real bund the other tanks and the foundations take up space up to the wall height and liquid cannot fill it. The regulation does not state this deduction; the tool makes it as a calculation assumption:
Vnet(h) = L × W × h − Σ π/4 × Di² × min(h, hfound + Hi) − π/4 × Dlargest² × min(h, hfound) − Vother
- The largest tank, which fills the bund, is taken as empty; only its foundation is deducted.
- Every other tank is deducted with its foundation as a solid cylinder up to the bund height.
- Tanks are vertical cylinders on foundations of the same diameter; tank volume is π/4 × D² × H.
- Supports, plinths and portable containers go into the "other volumes" field.
The minimum bund height is the height at which the net volume equals the required volume. If the tank footprints fill the bund area no such height exists, and the tool says so.
Bund and tank layout
| Rule | Requirement | Clause |
|---|---|---|
| Tank to bund | At least 3 m from bund walls lower than 4/5 of the tank height, measured from the tank shell | 119/2-ğ |
| Dividing walls | Not lower than 4/5 of the outer wall; channels open on top | 119/2-ı |
| Construction | Excavated or walled; non-combustible except the sealing membrane; liquid-tight in a fire | 119/2-g |
| Penetrations and drainage | Sealed pipes; water can be drained; closable outlet with a liquid separator | 119/2-h |
| Inside the bund | Only valves and pipes besides the tanks | 119/2-i |
The 3 m rule in 119/2-ğ is written only for bund walls lower than 4/5 of the tank height; for a higher wall the clause sets no distance. The tool works out 4/5 of each tank group's height and compares the shortest distance you enter.
How many bund zones?
Class I, II and III liquids other than crude oil and carbon disulphide may share one bund zone while the total, expressed as Class IA, does not exceed 12,500 litres (119/2-d). Article 119 gives no conversion ratio; the tool uses the storage-building ratios of 118/2 (IB/2, IC/4, II/12, IIIA/40, IIIB/80) as an assumption and warns if the limit is exceeded. For crude oil or carbon disulphide one bund zone is allowed while the stored volume stays within 15,000 m³ and the bund surface within 700 m² (119/2-e); the tool takes the surface as the bund inside area. Clauses (a) and (b) also apply where Class I, II and III liquids are stored together (119/2-f).
The bund does not replace the protection zone around the tanks: for above-ground tanks the clearance comes from Annex 12/C, for portable containers from Annex 12/D, and at least two-thirds of it lies outside the bund (119/3).
Common mistakes
- Relying on the gross volume: the other tanks and foundations take up space inside the bund.
- Using only 75% for portable tanks: if the largest container is bigger, that governs.
- Placing a low wall against the tank: walls lower than 4/5 of the tank height need at least 3 m.
- Draining the bund to the storm-water line: the Annex 12/C note asks for a separate channel system and 119/2-h for a closable outlet with a liquid separator.
For tank distances to boundaries and between tanks, use the Annex 12/C part of the flammable liquid class and storage tool.
Frequently Asked Questions
How is the bund volume taken for tanks of different sizes?
Under BYKHY 119/2-a the volume of the largest tank; for tanks of the same size, the volume of one tank. For crude oil and carbon disulphide the total volume is needed (119/2-ç).
What is the 75% rule for portable tanks?
The bund volume is 75% of the total volume of the portable tanks, or at least the volume of the largest portable tank (119/2-b). The tool takes the larger.
Are the other tanks in the bund deducted?
The regulation does not say; Guide Figure 119.2 shows only side lengths × height. As a stated assumption the tool deducts the volume the other tanks and the foundations take up to the bund height.
How far must a tank be from the bund wall?
At least 3 m from walls lower than 4/5 of the tank height, measured from the tank shell (119/2-ğ). For a higher wall the clause sets no distance.
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