Unique Load Pins for Dry-dock Instrumentation

We are frequently approached to provide custom load cells, load pins, instrumented shackles, tension links, and compression load cells for a wide variety of applications. 

Half the fun of our job is learning about our customers’ businesses, the way they make a living, their unique applications and how load sensing can improve safety.

In the last year, we have been approached to provide load sensing on:

• A six winch dry-dock in Russia
• The lowering of a 750,000lb Oil & Gas tree to the bottom of the GOM
• Seismic vessels in Norway
• Tug boat owners in the UAE, in the UK, and in Eastern Canada
• Pipe-lay barges in Nigeria, GOM, and Peru

In terms of measuring line or cable tension, we will often supply a running line tensiometer (or cable line-rider) with a load pin pre-installed.  Here is link to our line riders.

In other applications, our customers may have an existing sheave that we can help instrument.

Recently, a dry-dock operator came to us and wanted, for the first time, to install tension measurement on the dry dock maneuvering system.  Because they were using large diameter poly rope and they had existing turning sheaves with fixed wrap angles, we provided replacement load pins to retrofit the sheave axles.

Here is an image of the 130,000lbs pins. They were approximately 12” long  x 7” in diameter and weighed almost 65lbs each.  Despite their size they are sensitive enough that a couple of lbs of pressure will register in their mA output.

If you have a unique application, give us a call.

Load Pins

Tags: 000lbs load pins, 130, custom, dry dock, dry dock manuvering, instrumentation, instrumented shackles, line riders, measurement, system, tension links, tension measurement, unique load pins

This entry was posted on Friday, February 3rd, 2012 at 7:04 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.

MTNW & Delmar – New Approaches to Offshore Mooring

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

Tags: cable tension, delmar, Line Tension, MTNW, RLT, Running Line Tensiometer, Samson synthetic rope, tensiometers, tension measurement

This entry was posted on Tuesday, October 11th, 2011 at 11:48 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.

Cable Lay Operations – Gulf of Mexico

Tension Monitoring for Subsea Cable Laying

In subsea cable laying operations, it is imperative to understand the tension on the cable that you are laying on the ocean floor.  Too little tension and the cable will potentially kink under the vessel, too tight and the cable could break internally.  Once a cable has been bent or broken the entire span is unusable.

Subsea Cable Laying Ship

Often subsea cables will cost millions of dollars and the laying of the cable is a high-profile event with many observers…the cable manufacturer, the insurance company, the cable laying service providers and the vessel operators.  Everyone eager to ensure (and prove) that their piece of the operation doesn’t stress the cable.

Subsea Cable Laying

In March, one of our engineers flew down to Mexico to support a leading Oil & Gas services company in Mexico.  The service provider was working with PEMEX to lay a 2 mile subsea electrical and communications cable between 2 offshore platforms.  This service provider purchased a running line tensiometer (RLT) from MTNW to measure the tension, speed, and payout of the tugger winch cable which was used to pull the subsea cable into place.

You can see in the picture below that a RL-05K running line tensiometer was used to measure the tension, speed, and payout (scope) of the cable.

The MTNW RL-05 Running Line Tensiometer

This is our smallest RLT with a wire rope diameter limit of 20mm and a tension range of up to 13,000lbs.  They also purchased the LCI-90i winch display which provides tension, speed, and payout data.  This display is installed in a Pelican case for portability.   For data-logging they connected the LCI-90i display to a local PC and installed our WinchDAC (winch monitoring) software which provides all of the graphing and long-term data storage that they could need.  WinchDAC provides Demar the opportunity print out the force-over-time graphs , which can illustrate the peak tension of the cable lay operation.

The LCI-90i display in a Pelican Case connected to WinchDAC for data-logging.

WinchDAC Line Graph – Tension, Speed, & Payout

This cable lay operation was a success and the service provider, insurance company, and customer all had the real-time monitoring and data-logging to prove it.

Tags: cable lay operation, cable ship, cable tension, line control instrument, line control systems, line measurement, MTNW, subsea cable laying, tension measurement, tension monitoring

This entry was posted on Tuesday, June 14th, 2011 at 2:31 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.

Cable Tension Meters (or is it Tensiometers or Dynamometers?) for Barges, Rigs, Construction, and Pipeline Inspection.

We often get asked questions about the difference between tension meters, tensiometers, and dynamometers. There is good reason for the confusion because many different industries use the same words for different applications. For example, the word tensiometer, which we use to describe our primary cable tension/payout monitoring equipment, is also used to describe a soil moisture monitor, and dynamometer is a word that was widely used within North America for a device for measuring automotive horsepower.

At Measurement Technology NW we focus on measuring cable tension in many different applications (from 1,000 lbs-1,000,000 lbs) and we use the words tensiometer (dynamometer) and tension meter interchangeably. Even though the words mean much the same thing, our tensiometers can be provided with an extra sensor to measure payout and speed – two line control parameters that are not always considered when referencing a standard “tension meter”.

Tensiometers can be of two main styles; running line tensiometers (RLT’s) are designed to ride the line and provide measurements of tension, speed and/or payout as the line moves through the unit. Static tensiometers are devices that clamp onto to non-moving lines and only need to provide a measurement of line tension.

Our customers use MTNW tension monitoring devices in applications such as: offshore mooring, barge mooring, oceanographic payload monitoring, ROV launch and recovery system monitoring, tethered pipeline inspection (or pigging) monitoring, etc. Usually it is a safety requirement that drives the procurement of these tensiometers.

Here is a picture of a barge mooring monitoring project for which Ombak Marine Group in Kuala Lumpur has installed a group of MTNW’s tensiometers. These units are defined as tensiometers (or dynamometers) because we are helping them measure all three line parameters.

Our running line tensiometers are 3 sheave devices that detect tension by the deflection of the strain gauge transducer installed in the load pin that is in the center of the top sheave.

Here is another picture from an NPCC barge mooring monitoring project. NPCC, based in Dubai, ordered 8 running line tensiometers (or dynamometers) from us. You can see how we have installed this device in a compact area under a platform. It is tethered from above to avoid damage in a slack line event and tethered fore and aft to prevent rocking.

Whether you call it a tensiometer, a tension meter, or a dynamometer (and hopefully we’ve cleared away some of the confusion), we build the most rugged, accurate, and easily installed cable tension monitoring device in the industry.

Tags: cable tension, cable tension monitoring, tensiometers, tension measurement, tension meter

This entry was posted on Tuesday, January 12th, 2010 at 9:37 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.

Winch Payout Calibration

After spending the last 15 years installing and commissioning winch monitoring systems, we’ve found that some of the most commonly asked questions are about calibration.

1. How do we calibrate the LCI-90 display for tension and payout/speed?
2. How often should we calibrate?

These are important questions because the calibration inherently affects the accuracy of the winch monitoring system.

The following are methods we have used to calibrate the payout/speed system using our LCI-90 displays:

First, once the payout has been calibrated the speed data is developed automatically as it is just a time stamp of the incoming pulses produced by the rotational sensors. As in most physical measurements with external sensors, there is a theoretical method and an empirical method to achieve the payout calibration. Let’s consider a single overboarding sheave with installed rotational sensors. The scalar calibration value used in the LCI-90 display is pulses per unit length.

The theoretical calculation is to compute the circumference of a diameter defined as one line diameter plus the root diameter of the sheave. Then divide the pulse per one sheave revolution by this circumference to get a pulse per unit length. Drop this value into the display.

Equation = {(line diameter + sheave root diameter) * π} / pulses per sheave revolution

However this is never “exactly accurate”. The better way to calibrate your payout/speed system is to run a known length of cable through the sheave and note the accumulated pulses.

With the LCI-90 we can set the display to a diagnostic screen and monitor the pulses entering the display. Through the front panel buttons reset the payout by pressing the RSET button twice quickly. Then run the known length of line through the sheave, it is best to maintain a little tension on the line as to keep it line from slipping on the sheave. When the line has passed through, note the number of pulses on the DIAG screen of the LCI-90. Then the calculation is very straight forward:

Equation = number of pulses / length of line passed through the sheaves.

The same line standard can be used to verify both of the procedures above. The above scenario was recently used aboard the RV Thompson to dial in the payout system on the trawl winch. They had an opportunity to compare their winch monitoring readings to a very accurate beacon and transponder unit provided by an ROV group. They discovered differences between the two systems. Once they implemented the empirical calibration technique mentioned above they were able to get both systems to match.

Calibration should be done annually or as often as you detect discrepancies.

We have provided a small spread sheet at the bottom of this post to help calculate the required calibration value.

We will tackle the tension calibration in a later blog post.

Please give us a call if you have questions.
Phone: 206.634.1308
Email: lci@mtnw-usa.com

Download Spreadsheet

Tags: calibration, tension measurement, winch payout, winch tension

This entry was posted on Thursday, October 1st, 2009 at 6:16 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.