Dry braking systems are a straightforward and cost-effective solution. They employ a steel drive plate that compresses against a sacrificial friction disc to stop the motor shaft rotation. However, each engagement generates heat. Without a way to dissipate it, the heat can cause the surface of the friction plate to glaze over. Allowing air to flow through the dry brake can alleviate some of the heat, but doing so also introduces dust, dirt, scale, and moisture into the brake, which can cause corrosion, rust, and failed components – especially clips, coils, levers, springs, and bearings.
The maintenance and adjustment of dry brakes can be significant, often monthly or more, depending on the number of cycles that the system undergoes. Moreover, the cycles affect the brake’s service life, as there are only a limited number of engagements a mechanical item can endure. Higher cycle counts accelerate the failure date, regardless of maintenance and adjustment. If the brakes are spring set, the wear on friction discs can cause a change in torque and may cause unintended release issues.
If accurate positioning is required, the wearing away and glazing over of the dry brakes friction disc can elongate the stopping period and cause a positioning error. Depending on how critical the positioning is, this may be a mitigating factor in opting for an alternative means of stopping the load.
Wet brakes utilize the same basic principles of sacrificial surfaces and steel drive plates as dry brakes, but they introduce transmission fluid in a totally enclosed housing to achieve deceleration. When the liquid is compressed, its molecules shear, causing torque transmission to the other side and decelerating the rotating discs against the stationary plates. The design results in virtually no wear on the friction disc, eliminating the need for adjustment and maintenance. These brakes also use a patented fluid recirculation system that dissipates the heat generated by brake engagement, a major issue in dry braking systems. The transmission fluid also lubricates all components of the oil shear brake, extending their service life.
Because there is no wear on the friction disc, the positioning is precise over the lifespan of the oil shear brake, with no adjustment required. Oil Shear Brakes often perform at higher cycle counts than traditional dry brakes, enhancing machine performance.
The decision between dry or wet brakes also will have a significant impact on your budget when it comes to the overall cost of your braking system, but it is important to consider not only up-front purchase costs, but ongoing maintenance costs as well.
Initial Cost Vs. Operating Cost
While dry brake systems have a relatively low initial cost, they require regular adjustment and maintenance. In addition to labor this also involves stocking materials like friction plates. Since dry brakes generate a lot of heat and cannot dissipate it, working on them can be dangerous, requiring cool-down periods before any adjustments, repairs, or replacements can be made. The location of the brake can also come into play. Crane brakes, for example, require that maintenance and adjustment be made at height, which introduces safety concerns. Whether for cooling down of the brake, assembling parts, or the actual labor to perform maintenance and adjustment, all this downtime adds up, becoming very costly, very quickly.
Wet, oil-shear brakes require no adjustment, and are maintenance-free except for an annual transmission fluid change. That can be good news for plants where maintenance personnel are in short supply. No maintenance and no adjustment mean there are no parts to stock, so inventory carrying costs are reduced. The positioning is precise over the opil shear brake’s lifetime as well, so there are no process changes or adjustments required of your production line. However, whether wet or dry brakes are employed, each has a finite number of engagements before they must be replaced. Brakes in high-cycle count operations, like a crane that is jogged into place, or will inherently wear out sooner, and are prime considerations for an Oil-Shear Brake.
Because initial setup costs and ongoing maintenance costs can differ so greatly, it’s important to do the math. Estimate the brake’s service life in comparing total costs over the estimated life of the longer-lasting brake system. This will provide you with a more realistic full-cost comparison to help determine the most economical braking option.
