Civil | Infrastructure

The Civil/Infrastructure category contains blogs related to civil engineering and infrastructure projects.

How to Install Weldable Strain Gauges

 

Weldable strain gauges installed on a bulk material tank.

Weldable strain gauges installed on a bulk material tank.

When it comes to measuring structural stresses and load, every application is unique, and sometimes that means using a different solution.  In some cases where strain gauges are applied, it can be advantageous or even necessary to use weldable strain gauges instead of chemical bonding the strain gauges to the specimen.

Since many epoxies used to chemically bond strain gauges require specific heat and pressure for curing, it can be difficult or even impossible to use this method on large or irregular structures.  Weldable strain gauges offer an advantage in this situation as they eliminate the need to clamp and cure any epoxies for bonding. In addition, weldable gauges can be installed in a variety of environments and weather conditions which offers additional advantages over traditionally bonded strain gauges. Although weldable strain gauges are applied differently, they function in much the same way as their bondable counterparts.

To properly install a weldable strain gauge, you will need:

Always remember to have the proper safety equipment on hand, such as eye protection and gloves, as well as any PPE required by your environment.

When installing a weldable strain gauge, you must first prep the area. Unlike bondable gauges, the area does not need to be polished to a fine degree.  Simply degrease the gauge area, sand down any paint, coatings or excess debris and ensuring the area is purely metallic and free of chemicals is enough.  A clean metal surface is important to the welding process.

After the part has been cleaned, you can position the gauge.  Most weldable gauges come marked so you can align the grid properly.  When the gauge is properly aligned, spot weld the gauge on either side of the gauge along the centerlines, to hold it firmly in position and prevent shifting as the gauge is welded further.  Once secure, the gauge should be welded all around the carrier surface, as illustrated below.

Weldable strain gauge spot weld pattern.

Weldable strain gauge spot weld pattern.

 

Recap:

  1. Clean the area to be bonded (Remove all paints, coatings, residue and debris until the surface is smooth).
  2. Mark center-lines for the gauge location with scribe and straight edge.
  3. Place the gauge on the part, lining up the center-lines.
  4. Spot weld the gauge on each line, to secure it in place.
  5. Weld the entire perimeter of the gauge in the pattern shown above.

For more information about our strain gauging and testing services, contact Ryan Welker @ (844) 837-8797 x702.

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Contact ITM for your Strain Gauge Needs  

Installing strain gauges in the field for structural and fatigue measurements requires expertise and experience. Whether you use our iTestSystem software to stream and analyze strain signals for static measurements and real-world fatigue data acquisition or contract our software engineers to build a real time strain monitoring system, we will make sure you acquire quality strain data. Contact our strain lab and technicians to install strain gauges on test specimens or to design, build, calibrate, and test strain-based load cells. 

Strain Lab Contact Info: Ryan.Welker@iTestSystem.com, (844) 837-8797

Accelerometers for Rotating Machinery Vibration Measurements

Choosing an accelerometer for rotating machinery vibration measurements can be a daunting task since there are so many options available. This blog outlines the characteristics you should consider when choosing a piezoelectric single axis accelerometer for general purpose vibration measurements and presents some accelerometers to consider.

Characteristics of a General Purpose Accelerometer

When measuring vibration on rotating equipment such as motors, pumps, and generators, the most common measurement location(s) are on the shaft bearing housing(s) at the shaft centerline. At this location, typical vibration levels perpendicular to the shaft are < 100 g and the frequency range of interest is < 5000 Hz.  A general purpose single axis piezoelectric accelerometer with either a 10 mV/g or 100 mV/g sensitivity fits this criteria.

Other characteristics to consider are size, mounting options, cable connections, grounding, and cost. Several mounting options are available. They include magnetic bases, adhesive bases and stud mounts. The mounting option you choose affects the frequency range of your accelerometer measurements. The table below shows typical frequency limits for accelerometer mounting methods.

Mount TypeTypical Frequency Limit
Magnet2,000 Hz
Adhesive5,000 Hz
Stud6,000 Hz

5 General Purpose Accelerometers

The table below shows some examples of stud mounted general purpose piezoelectric accelerometers. These accelerometers all have a female 10-32 coaxial / microdot connector.  It is important to note that this is not a complete list of accelerometers and there are many options available from each manufacturer. I would encourage you to go to the websites linked in the table and see what’s available.

 
ManufacturerPCBDytranBRÜEL & KJÆREndevcoKistler
Model #353B033055D14533-B256HX -108702B500-M1
Sensitivity10 mV/g10 mV/g9.8 mV/g10 mV/g10 mV/g
Frequency Range(±5%) 1 to 7000 Hz(±5%) 1 to 5000 Hz(±10%) 0.2 – 12800 Hz(±10%) 1 to 10000 Hz(±5%) 1-10000 Hz
Temperature Range-65 to +250 °F-67 to +250 °F–67 to +257 °F-67˚F to +257˚F-67˚F to +257˚F
Height0.88 in0.64 in0.54 in0.55 in0.67 in
Weight0.38 oz0.35 oz0.3 oz0.14 oz0.32 oz
Housing MaterialTitaniumTitaniumTitaniumTitaniumTitanium
Electrical Connector10-32 Coaxial (side)10-32 Coaxial (side)10–32 Coaxial (side)10–32 Coaxial (top)10–32 Coaxial (side)
Mounting Thread10-32 Female10-32 Female10-32 Female10-32 Female10-32 Female

For more information about collecting vibration data, accelerometers, iTestSystem, or test equipment rental, contact Mark Yeager @ (844) 837-8797 x701.

Another Successful Condition Monitoring System Installation

Last week our team successfully and safely installed another Boiler Monitoring System (BMS).  This system, a Sootblower Fouling Detection (SFD) system, monitors structural and vibration sensors that quantify the boiler’s response to sootblower operations. The SFD system analyzes the boiler response data and outputs Key Performance Indicators (KPIs) such as fouling level, sootblower efficiency, and sootblower health to automated boiler cleaning systems.

This boiler uses over 50 sootblowers located at different elevations to clean soot build-up from boiler steam tubes.  Since the vibration measurement locations are relatively far apart, the SFD system requires a distributed monitoring system consisting of several junction  boxes that monitor and process data for groups of sensors.  One team of engineers mounted the vibration sensors to the sootblowers and confirmed communication back to a local junction box containing the National Instruments condition monitoring hardware.  The other team installed the junction box panels and terminated the sensor cables.

After all the sensor installations and terminations were completed, each sensor’s location and calibration were verified.  While the sensor verification was being completed, one engineer worked with the mill IT department and the controls engineer to establish remote connection to the system and confirm communication with the mill’s automated cleaning system.

After commissioning the system and returning to our home base, our engineers are now monitoring the system through a VPN connection and assisting boiler operators with optimizing their cleaning process.

For more information about our boiler condition monitoring systems, contact Ryan Welker via email at ryan.welker@iTestSystem.com or phone @ 1.844.837.8797 x702

Machine Failures Caused by Intermittent Damaging Events

Over the years we have been tasked with identifying the root cause of machine structural failures. In many cases, we can determine the failure mode through strain and vibration testing, order analysis, modal analysis, and operating deflection shape analysis.  What tests can you run when the damaging conditions are intermittent and not easily identified?

In these cases, we like to install a cellular networked temporary data acquisition (DAQ) system that can autonomously log vibration and strain data along with machine status data. We have deployed two types of DAQ systems to collect data remotely.  An interactive system that includes an industrial PC running our iTestSystem software and National Instruments (NI) Compact DAQ hardware and a headless system that utilizes NI Compact RIO hardware.  Our test engineers prefer using the interactive solution for troubleshooting because they can view real-time signal waveforms and collected data files, and then adjust the test parameters accordingly without having to reprogram the hardware.

Rugged Measurement System

Figure 1: Headless networked data acquisition system

When potentially damaging events are identified in the vibration and strain data collected by these systems, it is important to know the machine’s operating status. Collecting the machine status information is just as important as collecting the structural data.  Many machines transmit these operating variables and operating stages over their network/bus.  Recently we have recorded process data from Allen Bradley Control Logix PLCs via Ethernet/IP, mining machine data from a Siemens controller via proprietary TCP/IP protocol, boiler condition data from a DCS via Modbus TCP,  machine pressures from PI historian via the UFL connector (TCP), and vehicle speeds and pressure via CAN.  Fortunately, we were able to use and adapt LabVIEW communication protocol tools to build applications and addons that allow this network tag data to be collected along with structural data.

LabVIEW Modbus to Shared Variable Code

Figure 2: Modbus to Shared Variable Tool

After the data collection phase, our engineers perform statistical analysis on the sensor and status channels in all data files and aggregate the results into a database for searchability. To identify the root cause probabilities, you can process the channel statistics data using your favorite correlation algorithm or application.  The image below shows an example data set containing related sensor data that was processed using a LabVIEW correlation test tool.

LabVIEW Correlation VI

Figure 3: Correlation Test Example vi

Contact Information: For more information about our remote data acquisition service, our LabVIEW development service, or iTestSystem contact:

Mark Yeager – Integrated Test & Measurement (ITM), LLC.  Email: mark.yeager@itestsystem.com or Phone: 1.844.TestSys

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Strain Gauge Installations for Field Testing

Image1: Shaft torque strain gauge installation example for field testing

Our engineers and technicians have epoxied, soldered and spot welded strain gauges for applications ranging from high temperature exhaust systems to miniature load cell measurements. Every application requires a unique understanding of the strain measurement requirements including installation environment.

If the strain gauge installation is to survive in the field you must plan for the conditions it will undergo. Three important variables that you should account for are temperature range, liquid exposure, and potential impact forces. These variables determine the type of strain gauge, epoxy, solder, wiring, coating, and impact/wear protection to use in the application. The table below shows which variables affect your installation choices.

 GaugeEpoxySolderWiringCoatingCovering
Temperature 
Liquid Exposure   
Impact Forces   

Table1: Strain gauge installation variables

For more information about ITM’s strain gauging services contact Ryan Welker at email: ryan.welker@itestsystem.com or phone: 1.844.837.8797 x702

DOT Structural Health Monitoring

As engineering consultants, it’s the nature of our business for our work to take us out on the open road. It is for this reason that we are proud to support several state Departments of Transportation (DOT) with their structural testing and data acquisition needs.  We travel the very roads, bridges and other major infrastructure that they work so hard to design, build and maintain. 

Over the years, our field-testing experts have provided DOTs with the manpower needed to install and maintain the structural sensors for monitoring bridge and infrastructure usage/health, as well as the custom enclosures that house the precision data acquisition (DAQ) equipment used to process and trend data from the structural sensors.  We are looking for more opportunities to provide DOTs with the manpower and tools needed to keep tabs on our aging infrastructure.  

If you need help or advice on a structural monitoring project, contact Ryan Welker (ryan.welker@itestsystem.com or 1.844.837.8797 x702).  

Building a Modern User Interface in LabVIEW

When we develop LabVIEW™ applications for our customers, a common request is for a simple, resizable and intuitive user interface (UI) for data visualization.  In these cases, we use a tree control and a subpanel.  This type of UI functions like a tab control that automatically resizes.  The main benefit of using a subpanel is to make your code more modular.

Figure 1: Modern User Interface with a Tree and Sub Panel.

To illustrate the modularity that this type of UI creates, I made an example LabVIEW™ project.  The main VI shown above uses a tree control to switch between a VI containing a graph and a VI containing a table.  I used our multi-queue event architecture for VI information communication messaging.  The image below shows the main VI’s significant functions.

Figure 2: Main VI’s Block Diagram – Significant Functions

The main VI’s functions are listed below.

Functions

  1. Initialize queues and events and then generate initialize event.
  2. Initialize tree and add tree items.
  3. When a user selects an item in the tree, generate data and then send it to the subpanel VI.
  4. Receive SubPanel Ready event from a subpanel VI and then insert the VI into the subpanel.
  5. Destroy queues and unregister for events.

In this example the subpanel VIs are very simple.  They populate an indicator (table or graph) and then generate a SubPanel Ready Event.  The two (2) subpanel VIs and block diagrams are shown below.

Figure 3: SubPanel VIs: Graph.vi and Table.vi

Contact Information: For more information on this example or our LabVIEW development service contact:

Mark Yeager – Integrated Test & Measurement (ITM), LLC.  Email: mark.yeager@itestsystem.com or Phone: 1.844.TestSys

Marquette University’s Engineering Hall Data Acquisition System

A CASE STUDY of Marquette University’s Engineering Hall Monitoring System

ITM Strain Gauging Services

Custom Strain Gauge Load Cell with Calipers and Drawings

Custom Strain Gauge Load Cell with Calipers and Drawings

Our strain gauge instrumentation team makes tough measurements 

Quantifying stress, strain and force within a structure using real-world strain gauge measurements is commonly used to verify FEA models and estimate a component’s fatigue life. Our engineers and technicians have planned and implemented challenging installations for our customers around the globe. Information from these strain gauge installations has allowed our customers to validate their designs and improve their product’s reliability. 

Contact ITM’s Strain Lab

Installing strain gauges in the field for structural and fatigue measurements requires expertise and experience. Whether you use our iTestSystem software to stream and analyze strain signals for static measurements and real-world fatigue data acquisition or contract our software engineers to build a real time strain monitoring or load cell system, we will make sure you acquire quality strain data. 

Contact our strain lab and technicians to install strain gauges on test specimens or to design, build, calibrate, and test strain-based load cells. 

Strain Lab Contact Info: Ryan.Welker@iTestSystem.com, (844) 837-8797