Month: April 2020

April 29, 2020

The SL6000 Subsea Draw Wire Breaks the 100 Ft Barrier

Engineering Marvel – The CPI SL6000 30 Meter Hardened Linear Position Sensor

Since the introduction of our SL series hardened draw-wire Linear Position Sensors almost 20 years ago, we’ve learned a lot about long stroke hydraulics from our hydraulic cylinder manufactures. Our first sensor product was largely a magnetostrictive sensor replacement, able to form-fit-function replace these sensors in cylinders where longer stroke lengths (1m-3m) exposed the weaknesses of that technology.

But we’ve moved so far beyond that now.

In 2008 we introduced our first Subsea rated linear position sensors, capable of operation in open seawater at depths up to 1 mile below the surface.  And over the years, we’ve had requests for longer and longer stroke lengths, all while maintaining our robust survivability characteristics.

It was only a matter of time before our technology broke the 100 foot barrier. But the advancement here may be more significant than just this stroke length milestone: that’s because it maintains high accuracy and robust operating characteristics while doing it. The SL6000 is the same ATEX/IECEX safety rated, subsea capable, non-contacting, high endurance draw-wire sensor that it always has been.

How to make the Worlds most Robust 30 meter Linear Position Sensor

It certainly helps if you are already making the world’s most robust 16m sensor, the SL5000. Despite the marked difference in the appearance of the SL6000, this sensor design was much more an evolution of our field-proven sub-sea sensor than it might seem.

To be able to get a draw-wire sensor to reach 100 meters reliably, you’ll need to solve the usual issues related to cable sag and retraction force. We use the same basic approach as is used in our SL2000-SL5000 series with a couple of enhancements.

The 100 foot (30 meter) sensing range is achieved using the same patented linear-rotary-linear motion converter as is used in all our sensors. This mechanism is constructed from non-binding metal alloy’s and used as a reduction drive, coupled to multiple power springs.  The SL6000 uses 4 separate springs to maintain spool tension. While only 3 are needed, the fourth provides a significant design margin without increasing the sensor footprint. The addition of the chain drive presents an efficient and reliable coupling method which is also designed to perfectly handle the reduction ratio. The added size of the sensor presents no problems for inside-the-cylinder mounting of the kinds of large bore and telescoping sensors that the SL6000 is designed for.

Actual linear stroke measurement is achieved by coupling a short-stroke magnetostrictive sensor to the output of our linear-to-rotary-to-linear reduction drive. Using a magnetostrictive sensor in this way, we leverage the significant advantages of each technology, with none of the drawbacks.  Since only a short magnetostrictive probe (rod) is required, we eliminate concerns related to rod sagging due to shock and vibration, rod deflection, and end of stroke dead zones while dramatically extending linear sensing capability. We leverage the safety approvals of the sensor technology and the entire technology solution is non-contacting.

The result is a robust and highly accurate draw wire based sensor which provides sufficient return force and smooth operation through the full cable extension without approaching the stress thresholds of any components.

Sub-Sea Draw Wire Operation, in Open Seawater, Really?

Like all our SL series sensors, the SL6000 doesn’t have to be protected inside a hydraulic cylinder or accumulator. Because the basic sensor mechanism has no pressure vessels and uses special corrosion resistant alloys, it can be deployed in open seawater without adverse pressure effects or binding.

Versions of our sensors have been deployed in huge hydraulic accumulators almost a mile below the gulf and riser-tensioning systems on oil rigs. In other harsh-duty  deployments in wet areas, our sensor can be used in applications that have nothing to do with hydraulics at all, like those found in large surface cranes, dam and gate controls, and elevator systems.

The CPI SL-6000 is a Unique Problem Solver in the World

We’re understandably proud of this latest technological accomplishment by our engineering team. When there are no other solutions to your long stroke position measurement challenges or any other harsh duty linear position sensing application, the SL6000 can be customized for your application.

Call CPI today for more information on the world’s most unique line of draw-wire Linear Position Sensors.

April 16, 2020

Hydraulic Crane Manufacturers Need CPI Linear Position Sensors

Simple cranes used in truck beds or simple lifting applications can use electric or diesel powered motors to deliver the required lifting force. Indeed many of these cranes use our waterproof limit switches for everything from anti-two-block prevention, to proximity sensors, to operator control panels.

But it gets really interesting when you begin to talk about hydraulic cranes, especially those used in large construction or oil & gas applications where the forces involved are tremendous, and the cost of failure potentially tragic in terms of both machine and man.

Many of the largest, most powerful cranes in the world use huge bore, telescoping hydraulics of some kind in both fixed and mobile configurations. A great example of this is the Liebherr LTM, currently considered the largest, most powerful mobile hydraulic crane in the world. With a lifting capacity of 1200 Metric Tons and a telescopic boom which extends to 100 meters, this crane on wheels can lift the equivalent of 700 cars.

Stationary cranes or crawler cranes like those used at shipping ports, mounted on barges, or installed on long term construction projects can lift even more weight though not all of these are hydraulic based. Consider “Big Carl” one of the worlds largest land based cranes, currently hard at work in the UK building a nuclear power plant. The crane was shipped from Ghent, Belgium to the Hinkley Point C project location in Somerset, UK on over 250 trucks over a period of months. The crane can manage up to 3000 metric tons and has over 5200 Tons of counterweights.

Linear Position Measurement in Crane Design

Large crane designs take many forms but a couple of applications for Linear Position Sensors are common

  1. Load-Torque Transducers – In this application, draw wire sensors are commonly used to measure overall load torque to prevent cranes from turning over. Calculations made from the sensor inputs and other inputs insure compliance with operational limits. This safety system is so important that often redundant draw wire sensors are employed for fail safe operation.
  2. Piston Position Measurement – For long stroke and telescoping hydraulics used on many cranes, and understanding of the piston position is critical for safe operation of the crane. Draw wire sensors are one of the only technologies that have the potential to handle both the stroke length and the robustness requirements here.

For cranes using telescoping hydraulics, there are very few robust solutions to hydraulic cylinder piston position measurement in the marketplace. Consider some of the high level requirements of such a solution:

  • Sensor must be capable of extremely long stroke length measurement (10m – 30m)
  • Sensor must withstand extreme shock and vibration
  • Sensor must be impervious to adverse weather elements.
  • In certain applications, sensor will need to be safety rated to prevent explosion risk when working in flammable component areas.
  • Sensor must work in telescoping applications where the cylinder may be multi-stage.

CPI Linear Position Sensor 30 meters SL6000

In such applications a hardened draw wire sensor such as the CPI SL-2000 (10M) or the new SL-6000 (30m) should be considered for all high power, long stroke crane hydraulics.

CPI makes an entire line of high endurance draw wire sensors designed from the ground up for maximum life and durability in the harshest environments inside hydraulic cylinders and accumulators, and below the ocean.

CPI Draw Wire Sensors for Crane Applications.

While other draw wire sensors claim to be hardened for harsh duty construction applications, CPI sensors were designed and built from scratch with that in mind. From the material science used in our parts, to our patented transduction approach, our sensors have the most robust operating characteristics of any draw wire sensor in the world today. Furthermore, many other draw wire manufacturers still use rotary encoders or even potentiometers in their design. CPI’s SL Series sensors are non-contacting technologies using either LVDT based transducers, or an ultra-short magnetostrictive sensor. We achieve contactless operation by virtue of a patented linear to rotary to linear conversion mechanism that effectively scales down linear piston movement to small increments readable by a short magnetostrictive sensor or an LVDT.

Many characteristics of the CPI SL series sensor make it perfect for both external or internal deployment inside the hydraulic cylinders used on hydraulic cranes:

  1. These sensors are impervious to temperature and pressure effects and can be deployed completely immersed in hydraulic fluid without compromising mechanical operation.
  2. The Sensor’s cable retraction mechanism is over designed to allow for significant speed and improved lifetime even for double-acting telescoping cylinders.
  3. Stroke Lengths for the Product line go up to 30m (SL-6000)
  4. The sensor is sealed and completely waterproof. Our sensors have been deployed in open seawater close to 1 mile down.
  5. Electro-mechanical endurance of over 1 million cycles.
  6. Sensor is by design, highly impervious to vibration, and thermal conditions.
  7. Sensor can be fully safety rated for deployment in hazardous areas such as drilling platforms. Sensor is fully ATEX and IEC-EX Certified.
  8. CANBUS or virtually any other analog output available.

For Crane designers looking for draw wire solutions outside the cylinder, CPI offers external mounting for all our hardened sensors in stroke lengths from 10M to 30M.

For more information on how CPI sensors can lift crane design to new heights, call our engineering sales team today.

This blog is originally posted here -https://www.cpi-nj.com/blog/hydraulic-crane-manufacturers-need-cpi-linear-position-sensors/