Build a demand profile that reflects the process
Separate continuous uses, batch demands, cleaning and simultaneous operations. A monthly average does not reveal a rapid tank fill at the start of a shift. Identify which demands can be rescheduled and which cannot tolerate interruption. This distinguishes required production from instantaneous distribution capacity.
Include known expansions and their timing rather than adding undefined margin to every component. Each design flow needs a traceable reason. Request consumption records by shift or hour where available; otherwise document assumptions that can be verified during engineering and reviewed with the operating team.
Calculate output within the available operating hours
In an ideal example, a factory needs 120 m³/day with 20 effective RO production hours. Minimum usable production is 120/20 = 6 m³/h during those hours. If an additional 6 m³/day is required for auxiliaries, the balance becomes 126/20 = 6.3 m³/h.
Do not add consumption already deducted from a guaranteed net-output figure. Define the boundary: membrane outlet, complete treatment outlet or point of use. Check hours lost to maintenance and conditions reducing output, particularly minimum temperature and the expected change in membrane performance during service.
| Assumed duty | Calculation basis | Ideal result |
|---|---|---|
| 120 m³/day in 20 h | 120/20 | 6 m³/h usable |
| Additional 6 m³/day auxiliaries | 126/20 | 6.3 m³/h |
| 10 versus 6 m³/h peak for 2 h | (10−6) × 2 | 8 m³ support volume |
Use storage to compare production with consumption
Tank duty follows the cumulative daily balance. If consumption is 10 m³/h for two hours while RO produces 6 m³/h, that interval needs 8 m³ of usable volume available beforehand, excluding additional reserve and level constraints. This is a demand-balancing calculation rather than a tank specification.
Check when the level can recover and how other demands affect the cycle. Include distribution pump flow and delivery pressure. The distribution pump may serve an instantaneous demand different from RO production, so both duties need their own sizing and operating checks.
Decide which failure the system must withstand
Stored reserve and a second membrane train address different situations. Define acceptable downtime, required output with one train unavailable and access to alternative water. A redundancy label should be supported by a balance showing delivery capacity throughout the specific incident being considered.
Compare quotations at the same temperature, feed quality, product target and net-production boundary. Ask how off-specification water is kept separate from usable product and how capacity will be demonstrated at acceptance. Appropriate sizing meets the actual use profile under explicit conditions and remains practical to operate and maintain.
Common questions
Should RO production equal my peak demand?
Not necessarily. Suitable storage and distribution pumping can decouple production from consumption. Check the complete balance and water turnover before selecting equipment.
Is catalogue flow available during winter?
It must be verified at the actual design temperature and conditions. Membrane production depends on feedwater and operation rather than the model name alone.