Delmar RLT

Measurement Technology NW (MTNW) implemented its running line tensiometer (RLT) technology with a Samson synthetic rope in an offshore mooring monitoring project engineered by Delmar Systems.  This implementation is MTNW’s first use of tension measurement technology with 2”+ synthetic ropes.

Recently, Delmar Systems was contracted to moor an offshore supply vessel (OSV) to a major offshore platform in the Gulf of Mexico. The OSV is being used as a support vessel while dive operations are conducted. The OSV is using a three-point mooring system consisting of two stern hawser lines attached to the platform and a bow mooring line attached to a preset suction pile foundation in 2,900 feet of water. The mooring system had to be as robust as possible while still maintaining ease of handling and rigging by the vessel crew.

To achieve a higher Maximum Breaking Load on the OSV bow mooring line while maintaining deck maneuverability, Delmar chose Samson’s AmSteel-Blue HMPE rope made of high modulus polypropylene (HMPE) as the bow winch line. An MTNW RL-20175K running line tensiometer provided tension measurement for the bow line.  During the design phase of the project, MTNW thoroughly tested and calibrated the RLT using the specified 2¼” AmSteel-Blue rope. 

 “This is MTNWs first use of an RLT to measure tension in a major synthetic mooring line of this large diameter,” said Tom Rezanka, managing director of MTNW.  “Our RLTs are more commonly used to measure the tension of wire rope, but synthetic lines have different mechanical characteristics under load.  We were able to collaborate closely with the R&D engineers at Samson.  The monitoring system was fully tested, calibrated and witnessed on an ABS-certified test bed with the resulting accuracy identical to wire rope applications. The trend in mooring is lighter and stronger, which will require increased use of synthetic ropes and new, modern technologies to monitor them. Our sensors and systems are proven to work with any lines.”

“Both the AmSteel-Blue winch line and MTNW’s RLT have been working flawlessly together and have played a vital role in the success of the project,” said Dillon Shuler, engineer at Delmar Systems. Rezanka explains, “MTNW RLTs are being used more frequently for mooring monitoring because our modern design provides a rapidly deployable solution for retrofitting existing winches.  We can deploy on virtually any winch, with an installation time measured in hours, not weeks or months.”

“Since the Macondo oil spill, we have seen a significant increase in interest from risk managers and lifting/rigging engineers for determining line and cable tensions in all environments,” said Rezanka.  “If it can be monitored, alerted on, and data-logged to a computer it needs to be.  Our solutions support the increasing safety requirements for offshore operations and allow project managers to sleep better at night.”

Original article can be found at: http://www.marinelink.com/news/approaches-offshore340216.aspx

Recently, DynaWinch has incorporated our displays (both the LCI-90i and the LCI-80) into their new product line of slickline skid units. They now manufacture electrically, hydraulically, and diesel driven skid based units for all types of environments and needs.

Their product line includes aluminum wireline van bodies for slickline, case hole, and open hole logging, mast units, swabbing rigs, and wireline skids for on-shore and off-shore applications. And, their wireline accessories include hydraulic drawworks packages, customized control panels, measuring systems, spoolers, and down hole tools.

The picture below shows Tom Rezanka, Managing Director of MTNW’s LCI product line, sitting at the controls of a DynaWinch wireline van built for one of their customers. Notice the beautiful display immediately in front of Tom. If Tom were an operator, that display would provide him with line tension, speed, and payout information through its electroluminescent (day-light readable screen) at line data sampling rates of over 200Hz! The display will also provide the operator with the ability to store up to 14 different tension and payout calibrations with automatic recall.

Michael Fernquist, Technical Project Manager for DynaWinch, explains to Tom how the operators use the controls and display information in their job.

Here is a picture of the MTNW 90i display incorporated into a an electrically driven wireline skid unit. You can see that our displays are built for rugged, all-weather conditions. If you thought our electroluminescent displays look good in the sun, you should see them in the rain!

It is also important to understand the technical challenges of calibrating the tension line parameter of your winch monitoring system.

The calibration of a tension measurement system can be achieved through several methods.

MTNW employees calibrate two Foss tugs in Puget Sound by having them pull against each other

It’s always best to conduct a live calibration of the winch monitoring system once the sensors, displays and line have been installed and the wrap angles determined and identified to be fixed (more on the wrap angle in another blog).

Since tension sensors behave in a very linear fashion, meaning that their electrical output has a linear relationship with the load applied to the sensor itself, a single, two-point calibration (a low tension and high tension reading) is often sufficient to calibrate a tension monitoring system.

We typically can calibrate a system to better than ±0.5% without too much trouble.

Calibrating a winch monitoring system requires the use of an additional (previously) calibrated tension sensor, typically a tension link. Make sure that the tension link has a valid certificate, that it is not expired. You can often rent these for days or weeks at a time.

Calibrations are typically good for a year for these types of devices.

Winch tension calibration often requires additional support from your marine operations group because they will need to provide the winch operator, a previously calibrated tension sensor, deck hands to rig the tension link to the winch line and winch time to complete the calibration procedure.

There have been many times we have been scurrying around the deck to get this done before the vessel leaves the port or the fuel truck shows up (all deck work ceases when the vessel is fueling).

One side of the tension link should be secured to the winch line and the other should be secured to either a rigid solid structure like the deck or weights of known values.
The winch operator can now carefully haul in the line slowly till the desired tension is reached or the weights have been lifted off the ground.

We prefer to use weights as they provide a more stable measurement platform. Because the winch line is basically a big spring, if you are securing your winch line to the deck the system can relax causing the tension link reading to change before the data is applied to the display.

Our method is to collect the tension sensor analog output (mA, volts, mV, etc) at two known line tensions, one high and one low. The low value can be either zero or near zero, depending on the application. The high point can be either the breaking strength of the line or the maximum tension the deployment can expect. It should be noted that the breaking strength of the line is a much higher value than the working tension range of the winch operations. Setting the high calibration point to the breaking strength will reduce the accuracy of the system at lower tension ranges.

We hardly ever calibrate to the maximum breaking strength of the wire rope as the forces required make the rigging difficult and increases the likely hood of something breaking and creating a safety hazard.

Always remember to stand way from the direction of the winch.

I was fortunate once to be able to walk away from an installation in Chile were I was not positioned properly and a snatch block gave way shooting across the deck and denting the bulkhead between myself and the Chief Engineer.

In terms of calibration, note the sensor output at the low and the high points and enter the data into your display. The LCI-90i display will automatically calculate the slope and offset of sensor output verses applied load and apply this over the complete working range of the sensor.

The LCI-90i makes calibration easier than most other systems because the input fields and buttons are right on the main face of the display. Inputs can be changed and updated on the fly without the use of an additional computer. Analog sensor values are displayed during the calibration making the calibration quick and easy.

If higher levels of accuracy are required, you can input more calibration points to develop a “look up table”. This can also be used if the sensor is exhibiting non linear characteristics. Synthetic ropes often will deform under tension and will perform non-linearly. The LCI-90i display allows the end user to develop and reference a “look-up” table without additional programming or a PLC interface.

Other calibration techniques can be used such as shunt calibration, voltage substitution, etc. These techniques, however, are hardly ever used and not worth learning about.

Good luck in your calibration. If you have questions, please don’t hesitate to give us a call.

We have just updated our division brochure with our new products and services. The images on the brochure come from our customers, vendors and partners!

We’re excited about 2010 and the many oceanographic, offshore, and construction projects we’re working on. Give us a call. We enjoy talking through questions about running line tensiometers, winch and cable spooling instrumentation or any kind of line tension/control project.

You can download the new division brochure by clicking here.

An HH-65C flight crew hoists an injured hiker to safety from a mountain peak in WA at an altitude of 6,300 feet.

The hoist was improved by adding a clutch designed to release if the cable forces exceed a known value.  The Coast Guard tested the release force pulling on the cable at various speeds from 1 in/s to 30 in/s.  After the hoist passed this testing, the Coast Guard then conducted a number of drop tests that consisted of a 600 pound mass attached to the end of the cable and various amounts of slack in the cable from 1 to 5ft.

During all testing, the tensiometer (or dynamometer) was attached to the cable and the load output was recorded.  The HRT-3mm system worked perfectly.

The HRT-3mm is designed to measure running line cable tension loads from 0-13,000 lbs.  It only weighs 30lbs and is compact but reliable.

The load cell on the Dillon unit was still functional but the rotational sensor had failed. MTNW designed a special gear tooth sensor and mounted it to the spur gear on one of the outer sheaves. In this manner we were able to obtain a digital quadrature pulse train that MTNW’s LCI-90 processed into a real-time display of speed, payout and cable direction. In the course of this retrofit MTNW worked with engineers from Dillon, the spur gear manufacturers, and our rotational sensor manufacturer. In the end we were able to measure 72 pulses per sheave rotation with a highly accurate payout resolution. The existing load cell was found to be functional and when connected to our LCI-90 display found to be very accurate in calibration. We also installed new bulkhead connectors on both the tensiometer and display units.

This Dillon Tensiometer is over 10 years old and came from the original Dillon series. It weighs about 350 lbs. As you can see in the picture below, we now make comparable tensiometers (dynamometers) which weigh less than 1/3 of the original Dillon model but which can support a similar tension range. Our RL-60 frame size (shown below) can accommodate a tension range from 0-60KIPS. For greater accuracy, we have used custom load pins in this frame size for lower (0-20 & 0-40 KIPS) maximum loads.

We also paired this older Dillon unit with our WinchDAC software for PC logging and remote viewing of operational data. Now NDT can build and send data directly out of WinchDAC into Excel for further report building. See our WinchDAC Software for Single Winch images below.

Given that Dillon was one of the first tensiometer manufacturers in North America it has been gratifying to see how well suited our modern technology was to the functional upgrade of this older system.

Because the LCI-90 payout measurement is so accurate, the construction team was able to go directly to the location of the stuck pig, dig down to the pipe, remove the obstacle, repair the pipe and keep pigging…all within a couple of days. This is exactly what Measurement Technology cable tension monitoring systems are designed to do! Provide fast, accurate information that prevents problems and saves you time and money.

In the picture below you can see the “pig” device that the CD Lyon team is pulling through the pipe to look for obstacles.

CD Lyon planned to use a 5/8” wire rope to pull the pipe pig and new pipe slipline. They needed to measure up to 14,000lbs of tension, which is load at which the pipe lining may be damaged.

This wire rope size and tension range was a perfect fit for our compact HRT-3MM tensiometer (dynamometer). We paired this tensiometer with our LCI-90 display, which was housed in a portable and rugged Pelican case.

In the photo below you can see that Coordinated Wire Rope and NTT Fabrication built a custom winch skid, on which they mounted the Pelican case and LCI-90 display. You can see the LCI-90 and case immediately to the left of the controls for the winch.

The photo below shows how the HRT-3MM tensiometer rides the cable it is monitoring. NTT Fabrication built an articulated arm which allows for lateral movement of the tensiometer (tracking line as the winch spools) and also supports the device in the case of a slack line situation.

MTNW’s solution provided an inexpensive and portable line monitoring system without the need for winch modifications. We pre-calibrated the system before it was sent it out, and Coordinated Wire Rope found that their new LCI-90 + HRT-3MM cable monitoring system was not only easy and intuitive to work with, it worked from the moment they pulled it out of the box.

For the last 15 years we have received monthly calls from winch operators and shipboard electronic technicians who have legacy MD Totco LM-2000 winch monitoring displays in need of repair or replacement. During these calls we are often asked how the LCI-90 and MD Totco LM-2000 compare.

Rather than go through a long list of features and benefits, the key differences are:

1. Daylight readability. The LCI-90 uses an electroluminescent display built originally for jet-fighters to ensure readability in direct sunlight. See picture above.
2. Cost. The LCI-90 is less than half the cost of the LM-2000.
3. Calibrations and Programmability. The five push buttons on the LCI-90 front panel are all you need to set 2 point calibrations, alarms, and input other data.
4. Construction. LCI-90 is built with a 316 stainless steel faceplate and sealed stainless steel pushbuttons for extreme durability and reliable performance under harsh conditions.
5. Wide Temperature Range. The LCI-90 is rated to operate effectively between -40C to 75C (vs. -20C to 55C for the LM-2000).
6. Support. The LCI-90 is the product that we have built our livelihoods around. We live and breathe its operations and support…and our support is personal. You can always call 206-634-1308 and ask for Matt, Tom or Derek with questions.

Under the hood the LCI-90 includes many more features not available in the LM-2000, but the outside dimensions are a match – which means the LCI-90 will fit into existing panel mount cut-outs as a direct drop-in replacement for the LM-2000.

Within a couple of weeks we will publish a blog post on the new LCI-90i which includes Ethernet connectivity and a whole host of upgrades to its processing power and sampling rates.