Planning a KESSEL EasyOil light liquid separator
The light liquid separators from KESSEL’s EasyOil range are used wherever it is necessary to prevent fuels and lubricants from entering the drainage system. The most suitable model and version must be determined by calculation based on the specific application. Find out here how best to proceed.
Please note that these planning tips are for information purposes only. To actually design an EasyOil light liquid separator, please use the KESSEL design sheet.
Step 3: Identify influencing factors
When designing a light liquid separator, in addition to the maximum rainwater and wastewater flow rate, you must also take into account the so-called influencing factors. These are determined by the density of the light liquids fed into the separator, the biodiesel content and the type of wastewater.
Step 4: Determine the nominal size and storage capacity
Once you have the figures for the maximum rainwater and wastewater discharge, as well as the influencing factors, you can calculate the required nominal size of the light liquid separator using the following formula:
NS = (Qr + fx × Qs) × fd × ff
Additionally, determine the required volume of the light liquid storage tank in litres, as specified by the relevant authority. When doing so, also take into account the quantities of light liquid that may be generated in the event of operational disruptions.
Sample calculation for a light liquid separator
Property: independent petrol station in Cologne
Operating information
S-I-P components
Rainwater and waste water not at the same time
Washbasin
- 3 x outlet valve DN 25
- 2 x outlet valve DN 15
- 2 x high-pressure unit
- Engine wash; oil with a density of 0.92 g/cm³
- B10 biodiesel
Precipitation area
- 100 m²
- r(5;2) = 245 l/s x ha
- B10 biodiesel
Rainwater runoff Qr
Local rainfall * | Rainwater runoff l/s | Rainwater runoff l/s | Rainwater runoff l/s | Rainwater runoff l/s |
150 | 1.5 | 4.5 | 7.5 | 12.0 |
200 | 2.0 | 6.0 | 10.0 | 16.0 |
300 | 3.0 | 9.0 | 15.0 | 24.0 |
* Check with the relevant authority if necessary; however, it must not fall below 150 l/(s x ha).
Local rainfall = ................................................. l/(s x ha)
Rainwater collection area 1 = ............................................................ m²
Rainwater collection area 2 = ............................................................ m²
Rainwater catchment area 3 = ............................................................
m²_______________________________________________________________________________________________
Total = ............................................................ m²
Calculation of rainwater runoff Qr:
100 m² x 245 l/s x ha : 10,000 = 2.45 l/s
Wastewater discharge Qs
→Qs 1: Drain valves/tap points
Outlet valves to which high-pressure equipment in accordance with Qs 3 is connected are not taken into
account here..................... No. DN 15 (R 1/2) at 0.5 l/s = ................................. l/s
.................... No. DN 20 (R 3/4) at 1.0 l/s = ................................. l/s
.................... No. of DN 25 (R 1) at 1.7 l/s = .................................
l/s_______________________________________________________________________________________
Total Qs1: .............................. l/s
→Qs2: Automatic vehicle washing systems / washes
...................... units at 2 l/s Total Qs 2: .............................. l/s
→Qs3: High-pressure cleaning equipment (HP equipment)
– Single unit: 2
l/s – Multiple units: 1st unit 2 l/s, each additional unit 1
l/s – Single unit in conjunction with an automatic car wash: 1 l/s
...................... units Total Qs 3: ............................ l/s
Unless the competent authority requires or accepts a different calculation, the nominal size of the waste water discharge Qs must be doubled: 2 Qs = .............................. l/s
Total QS = QS1 + QS2 + QS3 = QS …………………………… l/s
Minimum difficulty factors fx
Intended use | fx |
| a) for treating waste water (commercial effluent) from industrial processes, vehicle washing facilities, the cleaning of oil-contaminated parts or from other sources, e.g. petrol station filling points; | 2 |
| b) for treating oil-contaminated rainwater (rainwater runoff) from impervious surfaces, e.g. car parks, roads, maintenance depots; | irrelevant, as Qs = 0 (rainwater only) |
| c) to retain uncontrolled spills of light liquids in order to protect the surrounding areas. | 1 |
Calculation of the difficulty factor:
fx = 2
Rainwater | Value | Unit |
| Area | 120 | m² |
| Rainwater yield | 285 | l/s x ha |
| Runoff coefficient | 1 | - |
| Qr | 3.42 |
Wastewater | n | Qs | |
| Drain valve DN 25 | 1 | 1.7 | |
| Outlet valve DN 20 | 2 | 1.7 | (1.0 + 0.7) |
| HD unit | 3 | 4.0 | (2 + 1 + 1) |
| Qs | 7.4 |
Selected | fx | fd | ff | fs | ||
| 2.0 | 1.0 | 1 | 200 | |||
| ||||||
NS Calculation: dirt factor only | (fx × Qs) × fd | 14.8 | ||||
| ||||||
NS Calculation for rainwater only | Qr x fd x ff | 3.42 | ||||
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NS combined | 18.22 | |||||
NS elected | 20 | |||||
| ||||||
Calculate sludge trap | NS x fs / (fd x ff) | 4,000 | 20 x 200 / (1 x 1) | |||
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Selected sludge trap | 5,000 | |||||
