Abstract: A method and bipolar membrane stack for the generation of acid and alkali metal base solutions from an impure salt by electrodialysis. The unit cells of the stack comprise a novel arrangement of cation-selective membranes and an anion selective membrane with relation to a bipolar membrane forming four liquid flow channels. One of the cation-selective membranes is monocation-selective, passing monovalent cations while blocking the passage of multivalent cations. The method is operable continuously using untreated raw material brines contaminated with multivalent cation salts to generate substantially pure alkali metal base solutions.

Abstract: A method and bipolar membrane stack for the generation of acid and base solutions from a salt by electrodialysis. The unit cells of the stack comprise a novel arrangement of membranes which provide four liquid flow channels. One of the channels has circulating therein a multivalent acid solution which acts as a buffer and presents leakage of the salt anion through the bipolar membrane, thereby producing base solution of substantially reduced salt-anion contamination. The method can be operated on a continuous basis.

Abstract: A method and apparatus for generating acid and base regenerant solutions by utilization of a bipolar membrane electrodialysis stack. A mineral-containing salt solution is continuously circulated through the stack to produce a partially demineralized salt solution, an acid solution and a base solution. The acid solution and base solution are continuously circulated through the stack to increase the concentration thereof. The circulating salt solution is controlled to maintain the salt concentration in the range of 2% to 25% and the pH in the range of 8-11. The concentrations of the circulating acid solution and base solution are controlled to maintain the concentrations thereof in the range of 0.2N to 3.0N. The concentrated acid solution and base solution are utilized to regenerate exhausted ion-exchange resins.

Abstract: An RF shielded and electrically insulated circuit board structure comprises a first layer of shrink wrap tubing wrapped on a circuit board substrate, and a layer of an electrically conductive RF shielding material on the tubing. A second layer of shrink wrap tubing retains the electrically conductive material to the circuit board. Edge portions of the electrically conductive layer and heat shrink tubing are folded inward to prevent RF energy from the circuit board from leaking from the edges of the structure. The structure is made by wrapping a first heat shrink tubing on the circuit board to insulate and seal any wiring patterns and components thereon and shrinking the tubing by applying heat. The electrically conductive layer is located on the heat shrink tubing, and the second heat shrink tubing is wrapped on the electrically conductive layer and first tubing.

Abstract: A portable tester determines an operating condition of coin relays by sensing a duration of a time period between flux conditions generated thereby. The device does not require electrical circuit connection to the relay and is thus a non-invasive testing apparatus. An annunciator provides audible and visual indications to service personnel to indicate whether the detected duration is too short, requiring one form of adjustment, too long, requiring a second form of adjustment, or within a specified range therefor, requiring no adjustment.

Abstract: An air/water distributor underdrain assembly for providing a uniform distribution and metering of backwash air and/or water through a filter bed. The distributor assembly includes a distributor member which defines a distributor chamber for receipt of backwash air and/or water thereinto. A plurality of first and second spaced apart openings extend through the distributor member. A shroud extends downwardly into the distributor chamber from each of the first openings in fluid communication with an intermediate portion of the distributor chamber for directing backwash water therethrough. Backwash air collected in a gas compartment formed in an upper portion of the distributor chamber is directed through the second openings.

Abstract: A filter element having a perforated tubular core and a plurality of layers of strand material wound about the tubular core. The outermost layer has the ability to retain particles smaller than those retained by the innermost layer. The size range of particles retained by the outermost layer is from one to twenty-five microns and the size range of particles retained by the innermost layer is from twenty-five to one hundred microns.According to the method of invention, the filter element is used to purify liquids through the steps of precoating, delivering liquid through the filter, periodically backwashing the filter, and precoating the filter again.

Abstract: A liquid precoat filter has a multitude of elongated replaceable filter elements that have one of their ends supported on tubes that project upwardly from a tube sheet. A multi-component, spring-biased, sliding seal prevents leakage between the filter elements and their support tubes. Externally engageable connectors are used to releasably fasten the filter elements to their tubes.

Abstract: A liquid precoat filter has a multitude of elongated replaceable filter elements that have one of their ends supported on tubes that project upwardly from a tube sheet. The individual filter elements are releasably connected to the tubes by couplings that permit a spring clip to lock under shoulders when the filter element is pushed down; the spring clip is released when the filter element is rotated about one-quarter of a turn. A sliding seal prevents leakage between the filter elements and their support tubes.

Abstract: The invention relates to a method for converting strong-base anion exchange resins from the monovalent anion form to the hydroxide form. A .?.solution.!. .Iadd.source .Iaddend.of polyvalent anions is first passed through the resin to displace the monovalent anions. A solution of alkali metal hydroxide is then passed through the resin to convert it to the hydroxide form, and to produce an effluent solution of hydroxide ions and polyvalent anions. This effluent solution is then neutralized with an acid containing .Iadd.a source of .Iaddend.polyvalent anions, and the neutralized solution is passed through a second batch of resin in the monovalent anion form. In the preferred embodiment, a portion of the effluent is retained without neutralization and is delivered to the second batch of resin after the neutralized effluent to perform a portion of the hydroxide regeneration.