September 23, 2012
Shaft Alignment Thermal Growth Targets–When You Don’t Know
By Stan Riddle
In shaft alignment, machines that run hot often have thermal growth targets. Thermal targeting simply means that the shafts may be misaligned while at room temperature, but as they heat up to operating temperature, they will “grow” into alignment.
But where does the thermal growth target come from?
Many times, the machine manufacturer will specify the hot alignment target. It may be listed on the installation drawings, on a machine nameplate or in an installation and maintenance manual. And while these may be fairly accurate, they often are calculated without knowing certain things such as the real ambient temperature, the amount of air circulating around the machine, additional heat sources near the machine, etc.
VibrAlign has created a new app, available for Apple or Android phones and devices, called Therm Align. Therm Align is an interactive app to calculate thermal growth targets of the movable and stationary machines based on averaging temperature measurements from the base of the machine to the shaft centerline. These measurements are taken with a contact thermometer or infrared temperature gun and entered into the Therm Align app. Once the distance dimensions and temperature measurements are input, the app will calculate the thermal growth targets to be entered into your laser alignment system.
Thermal growth in alignment can be a real problem but with the Therm Align app, the calculations just became much easier.
Download Therm Align and other helpful shaft alignment apps from VibrAlign at the Apple App Store and Google Play.
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There are several sources on our web site to learn more about thermal growth. I counted six blog posts. But I would recommend if you have specific questions regarding a specific machine, that you consult with the fan manufacturer.
How can we calculate the target dial gauge readings, when we have the combination of vertical and horizontal thermal growth.
Eg: pump vertical growth 0.08mm
Pump horizontal growth : 0.21 mm(towards right side)
NB: rotation view from pump
Nju, it depends on the type of measurements. Are you using dial indicators or lasers? If you are using dials, are you measuring using rim and face, or reverse dials? Please feel free to email me directly at firstname.lastname@example.org. I will try to help.
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