mooring line tensiometer

MTNW Updates US Army Corp Dredge Potter Mooring Monitoring System

November 7, 2011. Seattle, WA. Measurement Technology NW (MTNW) announces successful implementation of its running line tensiometer technology with the US Army Corp of Engineers Dredge Potter. MTNW collaborated with C&J Offshore and Ockerman Consulting to ensure the mooring line monitoring project was successful from the initial design to the final installation and commissioning.

The US Army Corp of Engineers Dredge Potter is based near St. Louis and is charged with keeping the Mississippi passable. The Potter is a 240’ diesel electric vessel with a draft of 7’6″. It was recently retrofit during a deckhouse rebuild with a new haul winch and head hoist control system in 2011. The USACE contracted with Jensen Maritime Consultants (a Crowley company) and Ockerman Consulting to design the control system. C&J Offshore systems from Anacortes, WA were contracted to manufacture consoles and install these new controls. Ockerman Consulting chose MTNW’s Line Control Instrument RL-20175K 3-sheave running line tensiometers (RLTs) to monitor 2 mooring/hauling winches with 1.125″ wire rope with a peak tension requirement of 84,000lbs.

USACE Dredge Potter II

“The MTNW line riders installed quickly and easily. The RLTs are obviously built for a rugged environment and will have many years of service,” said John Ockerman, Owner, Ockerman Consulting. “The displays are intuitive and easy to work with. If you look at the whole bridge control console, from analog sweep meters to the standard PC HMI, the MTNW LCI-90i bright display jumps out at you from across the bridge.” The RLTs are integrated with the Dredge Automation Systems and Shipboard Integrated Control & Monitoring Systems. This system’s architecture provides real time and historic data to the ship’s engineers and dredge production performance data remotely to USACE headquarters.

Dredge Potter Controls

“MTNW RLTs are being used more frequently for mooring monitoring because our design provides a smaller footprint and rapidly deployable solution for retrofitting existing winches,” said Tom Rezanka, Managing Director of MTNW. “We can deploy on virtually any winch, with an installation time measured in hours, not weeks or months. In every environment, our customers are interested in monitoring and data-logging possible points of failure; and the mooring lines are a critical part of any dredge operations .”

Rezanka explains, “This is MTNW’s first installation on a dust pan dredge on the Mississippi. Our RLTs are frequently used to monitor pipe lay barges for offshore oil & gas installations around the world. We are pleased to be supporting the USACE here in the USA.

Measurement Technology NW, a Seattle, Wash. based company, provides a wide range of precision winch monitoring and control products, including the LCI-90i and LCI-80 (winch displays), WinchDAC (winch monitoring software), running line tensiometers or line riders, and much more. Look for MTNW at the Workboat Show, New Orleans, November 28 – Dec 1, 2011 (Booth 2566).

Running Line Tensiometer on Dredge Potter

Tags: dredge, dust pan dredge, LCI, LCI-80, LCI-90i, Line Rider, line riders, mississippi river dredging, mooring line tensiometer, mooring monitoring, MTNW, Running Line Tensiometer, St. Louis district, Workboat show

This entry was posted on Wednesday, November 9th, 2011 at 4:13 pm and is filed under Line Control Systems. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

Tension Calibration for a Winch Monitoring System

In a previous posting we discussed the technique of calibrating the payout line parameter for winch applications.

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.

Tags: barge mooring, cable tension, cable tension monitoring, Line Tension, mooring line tensiometer, Puget Sound, tugboat

This entry was posted on Wednesday, April 7th, 2010 at 6:38 pm and is filed under Line Control Systems. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

Post Update – Natural Gas Pipe Pigging & Slip Lining Application – Cable Tension Monitoring

We just spoke with Michael Kasten, President of Coordinated Wire Rope, and during the conversation he mentioned that last Friday the CD Lyon team was working with the LCI-90 and HRT-3MM tensiometer/dynamometer system (described in our last blog post) when they hit “a snag”…literally. The CD Lyon team was pigging the pipe, which means that they were dragging a device through the existing pipe looking for obstacles, when tension readings on their LCI-90 display suddenly jumped from 3,000 lbs to 13,000 lbs.

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.

Tags: cable tension, cable tension monitoring, Line Tension, mooring line tensiometer, winch payout, winch tension

This entry was posted on Friday, December 4th, 2009 at 7:00 pm and is filed under Line Control Systems. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

Natural Gas Pipe Pigging & Slip Lining Application – Cable Tension Monitoring

Based in Ventura, CA, Coordinated Wire Rope (http://www.coordinatedcompanies.com) approached us for a project that required highly accurate measurement of line tension and payout on an underground cable pulling application for their customer, CD Lyon. CD Lyon had been tasked with pigging (looking for obstacles) and slip-lining (inserting a new pipe into an old pipe) an old 8 mile natural gas pipe, and they were looking for solutions that would make the project run smoothly and efficiently.

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.

Tags: cable tension, cable tension monitoring, HRT-3MM, Line Tension, mooring line tensiometer, NTT Fabrication

This entry was posted on Friday, November 27th, 2009 at 7:24 pm and is filed under Line Control Systems. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.

Drill Ship Mooring / Oil Rig Mooring – 8 Line Mooring Project for Frontier Duchess

Our lead systems engineer, Matthew Lee, has just come back this month from installing, calibrating, and commissioning a mooring system for the Frontier Duchess, a drill-ship which is currently off the coast of Nigeria.

Running line tensiometer measuring tension on mooring lines for the Frontier Duchess.

On short notice, Matthew flew for over 20 hours from Seattle, through France, down to Port Harcourt Nigeria. Once in country, he was met by a friendly security team that helped him travel safely to the local heliport. From there it was a short but scenic 30 minute helicopter trip across the Bay of Biafra to the Duchess.

MTNW was called in to help install, calibrate, and commission the ship’s 8 mooring line tensiometers and LCI-90 winch displays. Mooring monitoring is crucial to FPSO and drill-ship work because ship managers need to reliably place and tension their anchors in order to limit ship movement. During drilling, the operators aim to keep the ship within a 12 inch circle. For a 75 foot wide and 475 foot long vessel like the Duchess, 12 inches is 1.3% of the ship’s width and .2% of its length… imagine attempting this feat while bouncing around on high sea states.

LCI’s WinchDAC software showing line tension for 8 mooring lines on the bridge of the Frontier Duchess.

In a traditional mooring setup, the vessel operator will notice a sudden change in position and will attempt to rectify the situation before the ship drifts too far and breaks the drill column. Essentially, the operators can only respond to problems after they have occurred, they have no foolproof means of predicting them. With MTNW’s mooring line monitoring system, the user can ensure that the tension on the mooring lines is low enough that the anchors are not at risk of shifting while also being high enough to keep the vessel in place; thus minimizing the chances of an anchor slip. In addition to this functionality, MTNW’s system can also monitor the payout of the line which enables the operators to accurately place buoys (with accuracy better than 30cm) to lift the mooring lines over subsea cables and pipelines.

The bottom line is that when you combine the action of dynamic sea states with the grid of subsea cables and pipelines crisscrossing the bottom of the ocean, mooring line monitoring becomes critical for personnel and property safety.

On the Duchess, Matthew worked closely with the ship’s electronic technicians and quickly brought the system online. All eight units were commissioned and calibrated (through a great deal of teamwork involving anchors, cranes, winches, and a tropical storm) and are now providing accurate and useful feedback for the ship’s operators. All on board were eagerly awaiting the opportunity to see the system in action during their next drill operation.

One of the key considerations any rig manager needs to think about when completing a mooring monitoring installation or retrofitting a legacy mooring/winch system is to think about where the tension, speed, and payout data needs to be seen. MTNW’s LCI system is designed to provide local visibility at the winch controls, but it also integrates to a PC based software interface that aggregates all mooring line parameters into one view at the bridge or control room (see image). This functionality was very popular with the crew of the Duchess, particularly the Captain, as it allows them to operate the entire system from the comfort of the bridge.

Another LCI system benefit is in the ease of hardware installation and maintenance. The LCI tensiometers are built with a removable center sheave which makes installation…even with deployed anchor lines…a breeze. Because we pre-calibrate our tensiometers before they are deployed, installation and commissioning often takes less than a week on site.

With installations all over the world, MTNW’s LCI team is rapidly becoming one of the leading experts in providing retrofit solutions for legacy mooring systems.

Tags: drill ship mooring, line mooring, mooring line tensiometer, off-shore, oil rig mooring

This entry was posted on Thursday, October 8th, 2009 at 10:00 am and is filed under Line Control Systems. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.