The skip-car control mechanism utilised to date included two mechanical, geared cam limit switches that are time consuming to program. Upgrading to meet modern demands required suitable components for measuring actual values that are not only characterized by their high accuracy and functional reliability, but are also easy to program. Hübner Giessen replaced one of the geared cam limit switches with a series FG 4 K incremental encoder and an AMS 4 K type absolute encoder with integrated SSI interface.
Home Case Studies FGH 40 supplies 1 million pulses per rotation for stone recognition at the bucket wheel excavator
FGH 40 supplies 1 million pulses per rotation for stone recognition at the bucket wheel excavator
Pilger mill in tube rolling mills - hot and cold pipe detection
- High-resolution encoder improves safety for excavator personnel
- Rapid detection of the smallest changes to rotation speed when excavating stone
- Avoids mechanical damage to the power train
- Robust design features high resistance to shock and vibration
The operator cabin of the bucket wheel excavator is located at the end of the boom.
Challenges
- A seam of lignite can be as deep as 100 m below the surface of the earth. In the majority of cases bucket wheel excavators are used to recover the lignite. The so-called stone excavation masks a high risk. The bucket wheel can become blocked if a tooth of a bucket comes up against a pocket of firmly entrenched stone. The increased load moment can result in the rotation speed of the bucket wheel dropping within a very short period of time. The blockage simultaneously causes the bucket wheel boom to lower. The entire construction of the bucket wheel excavator performs a dipping motion in the opposite direction to the rotary movement of the bucket wheel. This results in a further drop in the rotary speed of the bucket wheel. Personnel could be exposed to a hazardous situation if the tooth of the bucket wheel slips from the stone and causes the bucket wheel boom to swing upwards.
The high-resolution encoder FGH 40 detects even the smallest changes of rotation speed very rapidly.
Solution
- The high-resolution incremental encoder FGH 40 is equipped with a pulse disk and optical scanning technology to provide up to 1 million pulses per rotation. Utilising this encoder ensures it is possible to stop the bucket wheel within a rotational movement of less than 2° should the speed of the bucket wheel drop by just 0.5 rpm – before damage can occur to the power train. As is the case with all Hübner devices the FGH 40 is designed for use in heavy duty applications. Suitable for temperatures ranging from -25 °C to +85 °C it is also highly resistant to shock and vibration. Standard degrees of protection to IP66 and IP67 ensure they can be used in both wet and dust-laden environments. Above all, the safety of excavator personnel is significantly improved by the new FGH 40 encoder and the considerably faster reaction time for stone recognition.
Products and Accessories
Case Study Number
- TP3
Challenge
- The increasing flexibility of production lines requires a high adaptability of sensors. Continually changing object geometries, different temperatures and very high radiation or surrounding temperatures are no rarity.
- In a pilger mill those rough conditions can be found, among others in the production of seemless steel pipes. The raw steel blocks, each weighing a few tons are heated up first in a round oven at a temperature of 1300 °C.
- After descaling of the surface, the steel block is prepunched in a hole press with a strength from a converted 2000 t. In the next sloping rolling mill the growing pipe rotates between two rollers that are positioned at an angle to each other. The punching is widened to the size of the mandrel diameter.
Previous solution / Competitor product
- N/A
Solution
- The sensor that was installed at this application is the HMD OKA 2038.38 G with tube OL 19.
- The signal of the infrared sensors controls the movement of centering device and abutment. The point of view is restricted by the tube and prevents disturbances by steam in the cooling phase.
- An optimum adaptation to the operating conditions is given due to the adjustable response temperature. The HMD with self-learning response temperature (Auto-Teach function) is suited to continually changing conditions.
- The compact sensor with a stainless steel housing can withstand surrounding temperatures of up to 75° C. The use of a cooling jacket raises this up to 200° C.
- Alternatively sensors with fibre optic cables are available which permit an application at ambient temperatures up to 600° C without cooling.
Customer Benefits
- Maintenance-free
- High temperature stability
- Recognition of hot objects at big distances
- Self adjustment with Auto-Teach or step switch for the response temperature
Product Part number
- OKA 2038.38 G
Brand
- Proxitron
Accessories
- Piros swivel stand HM2
- Tube OL 19
- Pilot light unit (for alignment) DAK 308 + OL 26
- Different cable lengths (e.g. 15 m)
Customer Testimonial
compared to previous solution or competition
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