Chris Heberlein, Author at AUTOMATION INSIGHTS

Hydraulic Valves – Customize your Feedback

Hydraulic actuators can be used to open and close a valve’s position. In automation architectures, a linear position sensor is used within the hydraulic actuator to provide continuous position feedback.

The linear position sensor is installed into the back end of the cylinder. The sensing element resides in a cavity that has been gun-drilled through the piston and cylinder rod, extending the full length of the mechanical stroke. A magnet ring is used as a position marker and mounted on the face of the piston. As the piston (and the position marker) move, the linear position sensor provides a continuous absolute position by way of an analog or digital signal.

In some applications, a cylinder’s position may only be moving across a small portion of the overall stroke or a specific portion of the stroke. The end user could benefit from altering the transducer’s signal based on the application’s specific stroke requirements instead of the entire cylinder’s stroke, thereby maximizing available position resolution. When this situation arises, most transducer manufacturers offer the ability to customize or “teach” a modified output of the stroke via push buttons or from wiring inputs. When this is done, the process does require the cylinder (and position marker) to move to these defined locations for a “teach”.

A more user-friendly and repeatable approach for customized stroke lengths with linear position sensors is to use a graphical software package. The software can be connected
from a PC via USB to a compatible linear position sensor. Starting and ending stroke values can be precisely entered into the software and a graphical representation of the output curve is created. For a more straightforward approach, you can also drag and drop these stroke points by a click of a cursor. The file can be saved on a PC and downloaded to the transducer. In either case, the cylinder’s piston doesn’t need to be actuated.

In projects where multiple, identical actuators and linear position sensors need to be customized, the setup would only need to be done once, the file saved, and simply uploaded to all the sensors for the project. A great time-saver over manually teaching each and every sensor.

Another benefit to using software with linear position sensors is to be able to upload programs for replacement units in a safe user environment (e.g. lab station or office) and shipping them to various job sites. These different locations (or locales) can be in harsh environmental conditions (extreme cold or heat) or areas that contain ignitable or explosive gases or dusts which may be difficult to work in.

Other software features include inverting the output curves, offering position or velocity outputs, and more.

For more information on Balluff’s Magnetostrictive Linear Position Sensors, visit www.balluff.com.

A new angle on rotary feedback

Transporting hot materials (ex. steel slabs) from one location to another via a walking-beam is common place in steel manufacturing. In the past, rotary encoders have typically been used to provide the precise feedback of rotary movement for these types of applications. However, optical encoders are prone to failure in harsh environments. Steel mills utilizing walking-beams for material handling have plenty of dirt and particulates in the air as well as produce high shock and vibration. All of these would contribute to an overall harsh environment which would shorten the life of an optical encoder.

Precise position checking and the continuous adjustment of rotational movements are extremely important on the walking-beam. Inclination Sensors are ideally suited for these exact tasks. With contact-free angle measurement, they guarantee maximum precision when the slabs are being transported. Inclination Sensors do not need mechanical coupling in contrast to rotary encoders, are compact and robust, and measure the deviation from the horizontal on an axis of up to 360°.
Downtime at a Steel Mill can cost up to tens of thousands of dollars per hour. The next time you need you have an angular measurement application in such harsh environments, you may want to consider an Inclination Sensor. It will surely be up to the task!

For more information on Balluff solutions for the metallurgy industry, start here.

For more information, visit www.balluff.com.

Stop the Scrap

In the current era of steel production, steel manufacturers employ a continuous process during the casting phase of production. The molten steel is solidified during this process by a continuous casting machine. The processes include feeding the liquid steel through a series of rollers to cool the material and slowly form into the next shape of production (e.g. slabs, round, etc…). In this process, the rollers are positioned using hydraulic cylinders that include linear position sensors as closed loop feedback devices. The outputs of these sensors are closely monitored and are critical to the steel quality. Because of the harsh environment of the continuous casting process, the life span of these sensors can be cut short. If the sensor’s output becomes unstable and begins to fail, the continuous casting process cannot simply stop quickly. The steel quality during this sensor failure mode will most likely become scrap, costing the steel mill tens of thousands of dollars.

For maximum reliability, a linear position sensor with 2 or 3 times redundancy can be utilized to provide position feedback of hydraulic systems. Such sensors employ 2 or 3 independently-operating sensing elements and processing circuitry . The extra feedback signals can be monitored through an automation system. When the outputs are compared, a failure could be identified early and the automation system could switch over to the reliable output maintaining the quality of steel. No scrap! During the next possible scheduled stoppage in the manufacturing process, the sensor could be replaced.

For more information on Balluff solutions for the metallurgy industry, start here.

For more information, visit www.balluff.com.

Quick field replacement for linear sensor electronics

Micropulse Transducers BTL 7 Rod-style with Rapid Replacement Module — Micropulse Transducers BTL 7
Rod-style with Rapid Replacement Module

When maintenance technicians replace linear position sensors (also known as probes or wands) from hydraulic cylinders, it can leave a terrible mess, waste hydraulic oils, and expose the individual to harmful hot fluids. Also, the change out process can expose the hydraulic system to unwanted contaminants. After the sensor replacement has been completed, there can also be more work yet to do during the outage such as replacing fluids and air-bleeding cylinders.

Hydraulic linear position sensors with field-replaceable electronics/sensing elements eliminate these concerns. Such sensors, so-called Rapid Replacement Module (RRM) sensors, allow the “guts” of the sensor to be replaced, while the stainless steel pressure tube remains in the cylinder. The hydraulic seal is never compromised. That means that during the replacement process there is no danger of oil spillage and no need for environmental containment procedures. There is also no need to bleed air from the hydraulic system and no danger of dirt or wood debris entering the open hydraulic port. Finally, there is no danger of repair personnel getting burned by hot oil.

The RRM is an option for Balluff’s BTL7 Z/B Rod Series used in applications for the lumber industry, plastic injection and blow molding, tire and rubber manufacturing, stamping presses, die casting, and all types of automated machinery where a continuous, absolute position signal is required. Applications in industries such as Oil & Gas and Process Control are especially critical when it comes to downtime. For these applications, this Rapid Replacement Module capability is especially advantageous.

You can learn more about linear position sensors with hazardous area approvals, by visting http://www.balluff.com/local/us/products/sensors/magnetostrictive-linear-position-sensors/

The video below shows a demonstration of the Rapid Replacement Module in action.