The main idea behind reservoir capacity is balancing enough fluid for the pump to draw during high-demand cycles, plus room for thermal expansion, cooling, and settling of contaminants, without adding unnecessary weight or space. For the MOD-II, 30 gallons provides that balance: it is large enough to prevent the system from starving the pump or pulling air as the fluid warms and expands, and to allow for proper cooling and fluid turnover during operation. A smaller capacity, like 20 gallons, could underprove on headroom and risk cavitation or air intake during peak demand or temperature rises. A larger capacity, such as 40 or 50 gallons, would add extra weight and bulk and offer diminishing returns for typical use, making the system less practical to handle. Therefore, 30 gallons is the most appropriate and effective choice.

In oxyacetylene cutting, you want a strong oxygen stream to oxidize and push away molten metal, while the fuel gas is kept at a lower, controllable pressure to shape and stabilize the flame. The typical setup uses oxygen around 20–25 psi so the jet is powerful enough to sustain cutting. Acetylene is kept much lower, about 5–7 psi, and should not be allowed to exceed roughly 15 psi, to maintain a stable, hot flame and reduce the risk of backfire or flashback. This combination produces a clean, efficient cut; pressures that push too much acetylene or drop the oxygen pressure too low lead to poor cuts or dangerous conditions.

A 3/4 inch square drive is the size of the square stem that fits into sockets. This larger drive is used for higher-torque, heavy-duty work and accepts bigger sockets. The IW-12 is the tool configured to use 3/4 inch drive sockets, so it matches that size. The IW-20, by contrast, uses a different drive size, so it doesn’t fit 3/4 inch sockets. Therefore, the tool with the 3/4 inch drive is the IW-12.

When you’re sealing a hole with a plug and wedge underwater, you want packing materials that can conform to the surface and stay compressed under pressure. Wrapping the plug and wedge with fabric, rubber sheet, oakum, or sheet lead provides a flexible, compressible layer that fills tiny gaps and irregularities, creating a reliable seal. Fabric serves as a base, rubber sheet acts as a pliable gasket, oakum (tarred fiber) can swell slightly to block leaks, and sheet lead is soft enough to mold into crevices and distribute the load from the wedge. These materials remain workable underwater and adapt to the surface, whereas rigid substances like epoxy or GRP would not seal irregularities once set, and wax or tar alone isn’t as dependable or durable in wet conditions. Canvas with Herculite isn’t a standard combination for this purpose, as it doesn’t provide the same effective, moldable sealing properties.