Steel Mill Applications

Rolling Mill Main Drive | Metal Strip Leveling | CDB Brakes - Hoist & Trolley Brakes | Bridge Brakes

Situation
Electronic controls synchronize the recoiler’s arbor to the leading edge of the steel strip. The arbor must accelerate at a rate that allows the strip to be caught in the arbor’s slot but fast enough so that the strip does not deadhead in the slot.

Problem
If the steel strip deadheads in the arbor’s slot, the arbor will be subject to a sudden acceleration and the uncoiler will be subject to a like deceleration. This can cause inertial shockloads on the respective drive systems. The electronic controls cannot protect the drive system from inertial shockload because by the time they detect the problem, the inertial shockload has already caused drive system damage.

FMD Series

• Multiple disc with torque up to 190,000 lb-ft
• High energy
• Accepts elastomeric, gear or universal joint couplings
• Bores up to 10 inches

Solution
Place a FMD 561 Friction Limiter between the motor and spindle. When the impact occurs, the FMD 561 slips just long enough to absorb the shockload yet continues to transfer torque equal to the torque setting. Once the shockload passes, the FMD 561 stops slipping and the recoiler continues to do its job.

Situation
Coiled metal strip must be leveled prior to slitting or shearing. A leveler gearbox has a single motor input and many outputs. All of the outputs are mechanically tied together inside the gearbox.

Problem
If operating conditions cause one roll to experience a greater resistance then its opposing roll, it will draw a disproportionate amount of torque. This can cause gearbox and spindle breakage.

CMD Series

• Designs from 820 to 9,000 lb-ft
• 2 3/4 to 11 inch diameters
• Mounts either on gearbox output shaft or in between spindle’s u-joints.

Solution
CMD torque limiters are placed on the output shafts of the gearbox. Their setting is below the ultimate strength of the spindles or the gearbox. When an uneven load is applied the CMD will slip allowing even power sharing among all the rolls.

Situation
Drum brakes have been the mainstay of the steel industry. They are susceptible to a number of problems including drum surface cracking due to thermal shock, fade due to heat, frequent adjustments due to drift and drag problems (expansion and contraction of the brake wheel), lengthy downtime due to brake pad replacement and expense involved in getting heavy brake shoes up onto the crane.

Problem
At the AIST Crane Symposium each year, crane brakes were consistently recognized as one of the biggest maintenance problems.

CDBA Series

• Spring Applied, Electrically Released
• Operates in Series with DC Mill Motors
• Meets AIST Standard #11
• Series and Shunt Coils Available

Solution
PT Tech’s CDB Caliper disc brakes meet the AIST brake standard published in 1997. They directly replace existing drum brakes. They have the same mounting hole pattern and the centerline of the disc matches the centerline of the drum so no modifications to the mounting holes are required. They can operate in series with DC motors or in DC shunt circuits. Discs are not susceptible to checking due to thermal shock. They also eliminate drift and drag problems. Their friction pucks are lightweight and replacement only takes five minutes. Most importantly, they were designed with maintenance people in mind. Adjusting for wear takes 15 seconds. CDB brakes are used on hoists and trolleys.

Situation
The drive is designed to slow the bridge by first using motor plugging and then using a hydraulic brake as the sole means of stopping the bridge. Also, operators have a tendency to use the brake pedal as a foot rest. This causes the brake to drag and dramatically heat the drum. In other cases, the duty cycle of the crane has changed over time. Its new rate of cycling is much higher than when originally designed. This means the brake must contend with a higher than expected amount of energy

Problem solved!

Hydraulically

Problem
Bridge brakes are often abused for many different reasons. This leads to frequent and costly repairs.

or Electrically

HCDB Series
The HCDB brake is a hydraulically applied bridge brake that directly replaces 10, 14, and 18” drum brakes. Installation requires no modification. Its compact design allows it to fit into the existing space. The HCDB is designed to operate with the existing pedal/master cylinder. It reduces maintenance because it compensates for friction material wear. The HCDB’s unique caliper accommodates misalignment and axial motor movement. Replacing the friction pucks is quick and easy. The caliper folds down exposing the pucks. The entire procedure takes 5 minutes.

Solution
Replace the drum brake with the largest ventilated HCDB disc brake that will fit into the existing installation. The ventilated disc increases the disc’s energy dissipation through convection by increasing its air flow volume. CDBs can also be used with pendant control.