Doing the Math
There are few things engineers love as much as math, and Peter Nachtwey’s recent article on modeling pressure changes in hydraulic systems is filled with the calculations behind flow control. But Nachtwey’s article includes another important consideration for engineers: “The equations for calculating pressure changes are complicated and depend on many factors that are constantly changing. Hydraulic simulators use the current state to calculate the next state in small time increments. Usually increments of 100 microseconds are sufficient. The reason for using small time increments is that pressure changes quickly when an obstruction is hit, as in a press. Plus, the smaller the time increments, the better and smoother the simulation will likely be. The tradeoff is the additional calculation time needed and the large amount of data generated.”
More Precise Calculations
As a recent Hydraulic & Pneumatics article from Steve Mraz notes, precise calculations have some practical impact on production—and sales—for the calendering industry. “The arrival of hydraulic calendering over the last several years has opened the door to new ways to improve on mechanical calendering. With hydraulic calendering, rollers are moved by hydraulic cylinders, giving the cylinders a virtually infinite range of positionings to meet more demanding production needs,” he writes. “For example, customers for calendered rubber sheets now expect available thicknesses to include those from 0.05 to 0.1 mm with tolerances of ±0.01 to 0.005 mm. In some extreme cases, they need tolerances of ±0.0025. These tolerances are difficult to execute, but holding such tight tolerances saves on raw materials and reduces manufacturing costs while improving sales due to higher-quality product—at least for the few manufacturers able to manage it.”
And Don’t Forget Your Seals!
One more barrier in hydraulic systems is contamination, which makes a recent Hydraulic & Pneumatics article on the topic of seals important to review. As the authors note, “Contamination is estimated by hydraulic experts to cause 65% to 90% of all hydraulic system failures, making it a major cause for concern for fluid power engineers. And although filters have improved, oil can still become contaminated and cut short the life of hydraulic equipment.”
