Tubular plates

The tubular-plate design for the positive electrodes, shown in Fig. 7, is common mainly in European countries for batteries with larger capacities. In this plate design, the conducting elements are separated 

The advantage of tubular plates is the comparatively high utilization of the active material which results in a rather low weight in relation to capacity. These features have two causes, namely  

A disadvantage for tubular plates is the fact that a minimum tube diameter between 6 and 8 mm is required for economic production, but the tube diameter corresponds 

This means high porosity and a high utilization factor. 

The production of tubular positive plates is in principle similar to that of pasted plates. A number of manufacturers use the same gray oxide as the basic Ailing substance. Sometimes the portion of red lead or minium (PbsOr) is increased above 25 or even to 100 wt%. The latter is more economic when the manufacturer rans his own minium plant then the expense of the chemical oxidation of lead oxide (PbO) to minium (Pb304) may be compensated by reduced formation cost. Furthermore, curing is not required, because of the high oxidation state, and the battery starts with full capacity when formed. 

Different methods are in use for plate filling. The material can be filled as a powder with the aid of vibrators. Other techniques use a slurry of lead oxide or even a paste, as described above [26]. 

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Fig. 2. Cutaway view of a tubular positive lead—acid battery, (1) Positive tubular plate (2) iiegatwe plate (3) separator (4) connecting strap (5) ceU cover (6)...

The tubular positive plate uses rigid, porous fiber glass tubes covered with a perforated plastic foil as the active material retainer (Fig. 2). Dry lead oxide, PbO, and red lead, Pb O, are typically shaken into the tubes which are threaded over the grid spines. The open end is then sealed by a polyethylene bar. Patents describe a procedure for making a type of tube for the tubular positive plate (90) and a method for filling tubular plates of lead—acid batteries (91). Tubular positive plates are pickled by soaking in a sulfate solution and are then cured. Some proceed directiy to formation and do not requite the curing procedure. 

Figure 7. Section of a tubular plate a, lead-alloy spine (grid) b, active material (PbOz) c, tube, (in this example, fabric of polyester fibers) d, bottom seal of plastic caps.

Figure 9. Conversion of grid material into lead dioxide (Pb02) by corrosion spine of a positive tubular plate. New plate 3mm diameter means 7.1 mm2 cross-section (nr2 with r = 1.5mm). Aged plate reduction of r by 0.03 x 15 = 0.45mm means nr2 = 3.5 mm2.

Spiral Hollow fiber Tubular Plate and frame... 

Fig. 5.6 (a) Tubular plates for lead-acid cells, (b) Cross-section showing central lead current collector, active material and porous separators... 

It is probable that a range of soluble species such as Fe(OH)2 and Fe02 are involved, and it is known that Fe(OH)3 or Fe304 may be formed on deep discharge. The practical energy density of conventional tubular plate cells is 20-30 Wh/kg with the more recent cells which use press-sintered iron electrodes, values of 40-60 Wh/kg have been reported. 

The effect of concentration polarization on specific membrane processes is discussed in the individual application chapters. However, a brief comparison of the magnitude of concentration polarization is given in Table 4.1 for processes involving liquid feed solutions. The key simplifying assumption is that the boundary layer thickness is 20 p.m for all processes. This boundary layer thickness is typical of values calculated for separation of solutions with spiral-wound modules in reverse osmosis, pervaporation, and ultrafiltration. Tubular, plate-and-ffame, and bore-side feed hollow fiber modules, because of their better flow velocities, generally have lower calculated boundary layer thicknesses. Hollow fiber modules with shell-side feed generally have larger calculated boundary layer thicknesses because of their poor fluid flow patterns. 

Over the course of development of the membrane technology, RO module designs, as shown in Figure 8.4, evolved. They are tubular, plate-and-frame, spiral wound, and hollow hne-hber modules. In the tubular design, the membrane is lined inside the tube which is made of ordinary tubular material. Water is allowed to pass through the inside of the tube under excess pressure causing the water to permeate through the membrane and to collect at the outside of the tube as the product or permeate. The portion of the influent that did not permeate becomes concentrated. This is called the concentrate or the reject. 

Properties Tubular Plate and frame Envelope Spiral wound Capillary Hollow fiber... 

Membrane separators are built with a variety of membrane types assembled in modules that can take any of several forms such as spiral-wound, tubular, plate-and-frame, and so on (Hsieh et al., 1988). 

Tubular plates have been made with chemically prepared lead dioxide and 2.2 or 3.8wt.% sodium sulfate in the positive active-material [44]. Test results on cells cycled at constant-current are shown in Table 4.7. It was concluded that sodium sulfate increases the utilization of material by dissolving to create a more porous structure in the positive plate. It was also noted that graphite has an even greater effect in the same concentration range (see Section 4.4.7). 

Fig. 9.12. Voltage vs. SoC curves for CC charging of thin tubular-plate VRLA cells with three different saturation levels. Charging S-shaped curves (left to right) are for 100, 92, and 84% saturation [15].

Purpose-built batteries. Gel batteries with either tubular plates or thick, flat plates (> 5 mm) are recommended when a long cycle-life is required. Both designs have a high level of resistance to positive-plate degradation, and can tolerate high levels of positive-grid corrosion. 

Many manufacturers around the world offer tubular-plate gel batteries for heavy-duty RAPS operations. As the name suggests, the batteries have tubes that contain the plate material. This design is employed only for the positive plates, as these are... 

Technological scheme for the manufacture of tubular-plate batteries. 

The tubular-plate technology is used in the manufacture of traction and stationary batteries. Figure 2.53 shows die main stages involved in the classical production process of mbular plates. Only the preparation of positive plates will be described briefly, since the other technological stages are identical to those discussed for flat-plate batteries. 

Tube filling. The tubular plates are filled, under pressure, with a slurry of 3BS or 4BS positive pastes diluted with water, or with a suspension obtained from leady oxide and red lead... 

Curing. Tubular plates are cured for several days under definite conditions. 

Antimony alloys 4—11 wt% Sb, As, Sn, Cu (Ag) Flat plates, tubular plates for traction batteries, older types of stationary batteries... 

Low-antimony alloys 0.5—3.0 wt% Sb, Se, Cu, S, Flat plates, tubular plates for low-maintenance... 

Figure 4.39 presents a micrograph of the CL formed on the spines of tubular plates cast from Pb—0.09 wt% Ca—0.3 wt% Sn alloy (r = 3.33) [18]. The battery suffered from PCL-1 effect and had low capacity. The picture features a thick CL wifli cracks parallel to the spine surface, which impair the contact CL PAM. The appearance of these cracks can be attributed to the low creep resistance (30 h at 20.7 MPa). This is a value lower by more than a magnitude than the highest creep resistance measured for Pb—Ca—Sn alloys. The micrograph in Fig. 4.39... 

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