Technical Manual
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- Back flush outlet valve
Design of the Filtration Stage
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Form-No: TM-WW002 // Revision: A // Date: Oct. 10, 17
cavitation. In case the pump should be used for CIP or sea water application as well, depending on the chemicals and chloride content, the pump material has to be suitable to prevent premature fail- ure of the pump. When there are multiple filtration lines there is a possibility of sharing a common feed pump for several lines, however there should be a redundancy built in so that there is no possibility of a single point failure which causes the stoppage of the entire plant.
The back flush pump capacity is based on 80 to 100 LMH for the membrane area installed in one UF rack. The backflush pump shall be equipped with a frequency inverter for smooth ramp up and down and to maintain the backflush flow constant during the hydraulic cleaning and EBF cleaning procedures. Further the same design considerations as for the feed pump apply to the back flush pump as well.
Air blowers or pressurized air can be used with MICRODYN AQUADYN ® UA860 modules with the air scouring pressure max. 0.6 bar. The purpose of the air blower is in essence to provide sufficient agitation of the membrane fi- bers during the regeneration process. It should be designed with a blower discharge flow rate of 8 Nm 3 /h per module. Dosing pump The chemical dosing pump is required to supply the required chemicals to the membrane mod- ules during the EBF. Each different chemical requires a different dosing pump to ensure there is no mixing of different chemicals into the same dosing system. Depending on the application and dosage of chemicals into the system, a solenoid or motor driven dosing pump may be used. The dosing pump capacity is normally determined by the following parameters: - target concentration - source concentration - ack flush flow (directly related to backflush flux and installed membrane area in the UF rack) 5.1.3 Valves Valves to be used can be of pneumatic driven design. However, care must be taken in both cases that the opening and closing of the valves are well controlled to prevent fast opening and closing which may result in water hammers, directly pressuring onto the membrane modules, hence it is recommended to install air supply and release restriction on the valve actuators It is recommended that the valves come with position indicators which are connected to the control panel in order to ensure all valves are in the correct open/close position before transi- tioning to the next operation step. Design of the Filtration Stage
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Form-No: TM-WW002 // Revision: A // Date: Oct. 10, 17
The back flush outlet valve is an open/close device that is closed during filtration and opened only during regeneration, EBF and CIP. Therefore the sizing of the valve must be designed for the largest possible flow depending on the back flush flux.
The permeate outlet valve is an open/close device that is opened during filtration and closed during regeneration, EBF and CIP. Therefore the size of the valve must be designed for the largest flow possible depending on the filtration flux. In addition, this permeate outlet valve pre- vents a flow of water during back flush to the permeate line.
The feed inlet valve is recommended to be installed in cases where there is a possibility of feed water flowing to the membrane modules and a high hydraulic pressure can be subsequently applied. This could affect the back flush efficiency of the regeneration process as there is an additional backpressure when the back flush water is sent from the back flush pump to the membrane modules and subsequently to the reject line.
An air blower inlet valve is recommended to be installed inside the air pipe to fully isolate the air blower section from the rest of the water filled piping to prevent that there is a backflow of water into the air blower. The valve should be installed as close as possible to the junction where the pipe is joining di- rectly to the feed inlet of the UF membranes modules to minimize the flooding of the line. Check valves Check valves are to be installed in pipes sections where there is a possibility of backflow or where there are multiple pipe routes. An example is at the air pipe where there is a possibility of water backflow into the air blower when the air blower line/valve is open and the air blower has not yet built up sufficient pressure to push the air in the direction of the membrane modules.
Sampling valves and drain valves are recommended to be added wherever required, typically where it is required to do a drain of water for the maintenance of the system. Sampling valves can be added in front of and behind the membrane modules in order to collect samples for wa- ter analysis as a secondary check for the system operation.
A set of monitoring equipment is necessary to ensure that the entire system works correctly, safely and within permissible limits. Digital process monitoring equipment (i.e. pressure gauges, flow meter) is preferred over ana- log ones and recommended for optimum monitoring and control of the process.
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