Membrane Area Reducer Kit for HP4750(X), 25mm

Yes, you can use the AO membrane disc filters in the stirred cells. These disk filters are very brittle and must be handled with an abundance of care to avoid breakage. Use membrane tweezers  to carefully place the disk filter on the surface of the support disk and then install the support disk in the stirred cell body.

Yes, you can use almost all microfiltration membrane disk filters  in the stirred cells. The only exception are the ceramic membrane disk filters; these are too thick to fit in the stirred cells.

You can find a diagram for a typical stirred cell system at https://www.sterlitech.com/media/wysiwyg/Manual/HP4750_Flow_Diagram.png. In addition to the stirred cell itself, the user will require a pressure source consisting of a regulated supply of compressed inert gas or air, a bleed valve for releasing the air pressure, an appropriately sized magnetic stirring plate, and a permeate collection vessel (e.g. flask or beaker) to collect the filtrate. 

Yes, for flat sheet membranes that will be used with water or aqueous solutions, we recommend that you pre-condition the membranes prior to conducting your separation experiments. Pre-conditioning helps ensure that the membranes perform as expected. Also, pre-conditioning removes preservatives and other residuals from the membranes.

To pre-condition the membrane disk, install it in the stirred cell and then fill the stirred cell with purified deionized water. Initiate operation of the stirred cell at the pressure and temperature expected for the separation experiments. Allow the cell to operate until the permeate flux has stabilized at an expected value. Then release the pressure, discard any water remaining in the stirred cell, and discard the water from the permeate collection vessel. You may now proceed with your experiments by refilling the cell with the desired feed sample. At no time should the wetted membrane disk be allowed to dry.  

Yes, we offer operating manuals for the HP4750, HP4750X, UHP polymeric stirred cells. You can find links to the operating manuals for the stirred cells by clicking on the “Documention/Media” tab on the stirred cell product pages.

It is important to note that membrane manufacturer’s specifications for rejection and permeate flux are usually based on testing of large area spiral wound membrane elements operating in crossflow mode using standardized feed streams and pressures. It is normal, and to be expected, that rejection and permeate flux will be different for feed streams and pressures that are not similar to the standardized test conditions. It is also normal, and to be expected, that rejection and permeate flux will have greater variability from published specifications for devices with membrane active areas that are very much smaller than spiral wound elements, such as stirred cells. Some amount of concentration buildup in the feed for stirred cells is inevitable and this may affect rejection and permeate flux.

There are some tactics that can be used to optimize rejection and permeate flow while using stirred cells. First, the membrane should be pre-conditioned using purified deionized water. Please refer to the operating manual for the pre-conditioning procedure. Second, make sure that the stir bar is turning properly and at an appropriate rate. Third, the operating pressure should correspond to the membrane manufacturer’s recommended pressure. Finally, you may want to stop your experiments while there is still some feed liquid remaining in the stirred cell to mitigate effects associated with increasing concentrations.

Yes, you may connect the permeate line directly to an instrument. However, it is important to understand that if the membrane fails or is allowed to dry, then the full feed pressure may be applied to the permeate line. If the instrument cannot withstand the feed pressure, then directly connecting the permeate line is not recommended. Alternatively, if the membrane becomes prematurely fouled (due to a high TDS or particulate loading), permeate levels may drop below detection in the HPLC inlet port.

The stirred cells are designed to accept flat sheet membranes with thickness of 350 microns or less.

The porous support disk has a nominal pore size of 20µm.  

The HP4750 stirred cell is composed of 316 stainless steel, but is also available in Hastelloy C-276 for highly corrosive environments. The magnetic stir bar is PTFE coated to prevent corrosion and to ensure broad chemical compatibility. The standard seals are composed of Buna-N; other seal elastomers are optionally available.

Sterlitech offers an adapter that allows 25mm membrane discs to be used in the HP4750 stirred cell. Membrane discs with other diameters typically cannot be used. However, some users have been able to accommodate other diameters in low pressure applications by blanking the unoccupied area with an appropriately sized annular flat gasket. Please contact us if you desire to use smaller disks in the HP4750 as we may be able to provide some assistance.

Q: What is the active membrane area on the HP4750 Membrane Area Reducer?

A: The adaptor is used with a 25 mm membrane disc however, the membrane active area is approximately 323 mm2.

Q: Can I use 25 mm ceramic discs with HP4750 Membrane Area Reducer?

A: No, the ceramic membrane disk filters are too thick to fit in the HP4750 Membrane Area Reducer. Although not recommended by Sterlitech, some users have reported being able to close and operate the HP4750 stirred cell by replacing the support disk with a 25 mm ceramic membrane disk filter. However, success was almost always limited to low pressure use and physical damage to the disk filters was very common.

The HP4750X stirred cell has been designed to operate at higher pressures (up to 2500psi) and higher temperatures (up to 400F) than the HP4750 stirred cell. The top and bottom caps for the HP4750X cell are secured via high-strenght bolts, the standard HP4750 uses a clamp assembly to secure the caps. In addition, the standard seal elastomer for the HP4750X is Viton.