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  1. ashtree

    1000volt deep well motors

    Thanks everyone. A lot of different opinions on what is good, what is workable and what is not. That seemed to be the advice i had generally been getting anyway. Seems like the general consensus is though to put the transformer after the VFD
  2. ashtree

    1000volt deep well motors

    We are working through the issues on installing 1000 volt motors on well pumps at about 350 metres (1100 feet ) below ground. We have to go to 1000v because of the cable size required to limit the voltage drop at 400volts is so large that we cant fit the pump and the cable down the well. These...
  3. ashtree

    Help me in RO plant design calculations

    DuPont RO Technical Manual is a good start. However it is technical and requires close reading to develop a full understanding of the subject. https://www.dupont.com/content/dam/dupont/amer/us/en/water-solutions/public/documents/en/RO-NF-FilmTec-Manual-45-D01504-en.pdf Regards Ashtree "Any...
  4. ashtree

    Help me in RO plant design calculations

    On a single membrane recovery is normally limited to about 15% to avoid concentration polarization. However if you recirculate a portion of the concentrate from that one membrane back to the feed of the membrane it is possible to achieve concentrations up to the solubility limit of the most...
  5. ashtree

    TTHMs in wastewater

    Blurt Its a matter of what is getting carried through to the effluent to be chlorinated. THMs are typically caused by the chlorination of organic matter. Most likely you have more BOD in the effluent than what you had when you were feeding glycerin. A TOC/DOC test of the effluent when using the...
  6. ashtree

    Corrosion Control: Calcite for RO Permeate

    Why is finished water pH important beyond the obvious. If you are worried about corrosion, high pH is not required if you have the appropriate hardness, alkalinity, TDS etc. Higher pH is one way to get the LSI to an appropriate value but its also a balance with calcium and alkalinity. What this...
  7. ashtree

    Corrosion Control: Calcite for RO Permeate

    Wright 44, Do you have any details of the Limestone that you propose to use. Porosity, diameter, roundness? With regards to the water do you know the permeate TDS and the dissolved inorganic carbon As a general requirement you typically need to have an empty bed contact time of at least 20...
  8. ashtree

    Materials Handler - Pipe Fabrication and Valves

    PamL This is an excellent handbook which will help with some of the information you seek. https://www.emerson.com/documents/automation/control-valve-handbook-en-3661206.pdf Regards Ashtree "Any water can be made potable if you filter it through enough money"
  9. ashtree

    RO Water Treatment Plant

    It would also help to know how much daily, weekly or monthly variation in those water demand numbers. If there is considerable variation either side of the 100kl/day you may able to get away with 2 ROs smaller than 100kl/day with one running continuously using the capacity in the large storage...
  10. ashtree

    Dosing Pump

    Many pumps particularly if they have a fixed speed motor also offer stroke length adjustment which alters the volume of each stroke or pulse. This can be done manually or by a analogue controlled adjuster to give "automatic" or "remote" control. Stroke length adjustment works well but is not...
  11. ashtree

    Starting Methods for Motors in Oil and Gas Industry

    Little Inch is spot on. Unless there is a requirement for flexibility in operation in terms of flow then the overall savings are marginal. But because no one can select pumps properly anymore a VFD is typically installed because you can normally get the output you want at some speed. Maybe that...
  12. ashtree

    PDT test on UF membranes

    Thanks EdStainless UF membranes can tolerate reverse pressure during backwash so i would expect these to be okay. Regards Ashtree "Any water can be made potable if you filter it through enough money"
  13. ashtree

    PDT test on UF membranes

    I am setting up a pressure decay test (PDT) on a UF plant. In simple terms a PDT involves pressurizing with compressed the feed side of the membrane to about 5psi ,locking off the valves and looking at how quickly the pressure decays. This assumes that if a lumen is broken the pressure will leak...
  14. ashtree

    Water process piping for RO unit to prevent back pressure

    RO membranes do not like being unpressurised on the feed side and having pressure on the permeate side of the membrane . Typically this is recommended to not exceed about 30kpa (4.5 psi approximately). Its not about water hammer or surge , but about protecting the membranes from back pressure...
  15. ashtree

    valve actuator and positioner

    I agree with TiCl4s comments and you should also check what happens if you lose air pressure. Regards Ashtree "Any water can be made potable if you filter it through enough money"
  16. ashtree

    AC ( Asbestos Cement) Water Piping

    Early in my career i worked for a Utility that had a whole lot of AC pipe breaks in one part of a city. The breaks were often complete burst where the top of the pipe would blow out. It was not my operational area so i never got directly involved but i can remember the guys involved saying it...
  17. ashtree

    VSD or throttle control strategy for RO High pressure pumps

    All the above answers are good advice but I am going to propose a slightly different approach because there are some gaps in your information. First of all as someone has suggested above you need to start with the concentrate flow control valve and when the plant is running adjust it until the...
  18. ashtree

    Extreme Flow Variations & Process

    The pH change may be sufficient to impact on the other biological processes especially if the change is significant and rapid. Whether or not nitrification and subsequent denitrification is occurring will also impact on DO and aeration requirements. Membranes may allow the production of clear...
  19. ashtree

    Extreme Flow Variations & Process

    There is another issue here which requires some focus. Although you do not have a N or P limit and you say that you only have to meet a 30/30 requirement the 2ntu maximum turbidity potentially puts a fairly tough limit on your suspended solids. I am guessing that's why you are thinking about...
  20. ashtree

    Extreme Flow Variations & Process

    This is the type of situation that suits an SBR. If these swings happen weekly than you would not change from one basin to two basin operation in that time. If the variations are regular, lets say the low flow is always the weekend you would design a control system to deal with that. On those...

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