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Ensure your Thermowell
Designs Meet the Standard
with our new free tool |
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Design thermowells that last and extend the life of your temperature sensors with JMS SwiftyCalc. |
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| The only US Standard regarding the strength of
thermowells has just had its first significant revision in 35 years. There are new geometries, new requirements, new
capabilities and more than 60 new pages of math and physics calculations to boot in the ASME PTC 19.3-TW (2016) [updated from 2010]. |
Your objective? To ensure your thermowell designs meet the
standard.
Your tool? SwiftyCalc. Now free from JMS Southeast,
Inc. to registered users. |
The JMS SwiftyCalc quickly provides you with a
thermowell design based upon your material requirements and process variables that you can count on to meet the ASME PTC
19.3-TW standard. Save your results to your own account and return later to modify on the fly. JMS SwiftyCalc also
provides you with instant theoretical maximums for insertion length and flow rate. SwiftyCalc is perfect for faster
response time and increased reliability in your temperature measurement system.
Need to develop a quick budget for your temperature application project? Push a button and get pricing
from a friendly and knowledgeable JMS sales engineer.
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To sign up for SwiftyCalc, Register Online, or call 1.800.873.1835. |
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+ General |
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A Bit of Background on ASME PTC 19.3 History
For 35 years the PTC 19.3 has remained essentially unchanged. It is the only US standard evaluating the mechanical strength
of thermowells and is often referred to as a wake frequency calculation or a "Murdock Calculation". The benefits of the
former ASME PTC 19.3 calculation were that it was short, fairly simple to apply and generally successful in steam
applications for predicting mechanical failures.
The old PTC 19.3 standard, however, was extremely limiting in terms of what geometries could be used, provided no clear
guidance on how to deal with issues such as shielding and, significantly, did not address the phenomenon of in-line
resonance at all. This omission resulted in multiple well failures in non-steam applications, especially circulating
water, gas, heavy water and liquid sodium applications.
The New ASME PTC 19.3 Standard (In Brief)
In 2010 the first major revision to the PTC 19.3 since its inception was approved and published by the ASME. On the plus
side, the new standard addresses in-line resonance, fatigue factors for oscillatory stress, effects of foundation
compliance, sensor mass, stress intensification factors at the thermowell root, fluid mass and more. It allows a greater
variety of geometries such as step wells meaning that you can get a faster response time than ever in an application that
calls for a wake frequency calculation.
On the minus side, the standard has grown significantly in
length and complexity. What once was a mere four pages of text
is now more than forty.
Why Do I Care About the New ASME PTC 19.3 Standard?
For starters, it is the only US Standard evaluating the mechanical strength of thermowells.
Moreover, if a thermowell is going into a system you are designing then the standard says that you are responsible for
making sure that the well passes the ASME PTC 19.3 standard.
Thermowell designers are always balancing competing interests. Optimal temperature measurement pushes for thinner longer
wells in faster moving process fluids while thermowell strength characteristics militate for the opposite. When it
comes to mechanical strength the shorter, fatter and slower the better.
What Does the Swifty Calc Software Do For Me?
JMS has spent many hours creating Swifty Calc Software. What we have built is a quick and easy mechanism for customers like
you to check the validity of their well design against the PTC 19.3-TW with a minimum of effort and pain. The software
generates drawings and makes recommendations based upon the options you select. If your well falls outside of the standard
Swifty Calc tells you why and what you can do to design a well that will work.
Finally, with SwiftyCalc your work is saved on our servers so that you can come back to it and tweak it as you see fit.
SwiftyCalc is personal to you and other customers will see only their own account information when they log on. Obtaining
a quote on your well design for budgetary purposes is as simple as pushing a button.
Check it out for free today and find out why customers rate JMS #1 in quality and service. Let us know what we can do to
help you with your temperature application. We love this stuff!
Can JMS Help Me with the New PTC 19.3 Standard?
Yes. SwiftyCalc provides the solution for 90% of the thermowell applications our customers require. However, the
ASME PTC 19.3-TW standard provides the opportunity to consider corrosion factors, operation at or above in-line resonance,
custom fillets for increased support and much more.
Our JMS engineers are happy to discuss and provide premium custom reports based on these and other factors. JMS premium
SwiftyCalc reports consist of multiple pages establishing additional information utilized in the performance of the
SwiftyCalc.
Why do we run wake frequency calculations like the SwiftyCalc?
- To Avoid Vibration Damage to the Well. Thermowells exposed to a flow can begin to vibrate and harmonize with
the vortexes left in its wake by the passing fluid. This is called its natural frequency. As the thermowell approaches
its natural frequency the amplitude of vibration increases dramatically and can cause catastrophic failure of the
thermowell - typically at its base or root.
- To Avoid Vibration Damage to an RTD. Let's not forget why these thermowells are installed in the first place - so
that we can insert a probe into that thermowell to measure the temperature of a process. A thermowell that vibrates so
much that it shakes the sensing element in an RTD to pieces is not much help to the end user. Minimizing vibration
increases the reliability of your control and monitoring systems while reducing expenses that result from unnecessary
replacement of damaged probes
- To Avoid Stress Damage to the Well. Steady State Stress occurs when a fluid exerts stress at the base of the
thermowell (and thermowell step in the case of a step shank well) in the direction of the fluid's flow. Oscillating
Stress occurs when a fluid exerts stress at the base of the thermowell (and thermowell step in the case of a step shank
well) in multiple directions.
What the ASME PTC 19.3-TW Does:
- Provides the only US Standard giving explicit guidance on the strength of thermowells.
- Addresses risk posed to thermowells from transverse and in-line vibration.
- Addresses Oscillatory and Steady State Stress independently of each other.
- Includes the effects of foundation compliance, fluid, sensor mass, temperature de-rating for stress limits,
thermowell shielding and more.
- Allows increased geometries never previously permitted - like the step shank well - which provides optimal response
time at no increased cost to you.
- Provides the most sophisticated and innovative approach to thermowell design in 30 + years.
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+ What SwityCalc Does |
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- Provides you with a quick, free wake frequency calculation report based on the new ASME PTC 19.3-TW.
- Allows you to save configurations so that you can come back later to tinker with them.
- Allows you to compare multiple thermowell designs to a single process and vice versa quickly and easily.
- Provides theoretical max insertion and flow criteria on the fly.
- Permits you to print a one page report showing pass / fail results.
- Provides a simple interface to receive pricing for your well with the push of a button.
- And much, much more.
Perfect for faster response time and increased reliability in your temperature measurement system.
The JMS SwiftyCalc quickly provides you with a thermowell design based upon your material requirements and process
variables that you can count on to meet the ASME PTC 19.3-TW standard. Save your results to your own account and
return later to modify on the fly.
JMS SwiftyCalc provides you with instant theoretical maximums for insertion length and flow rate.
Need to develop a quick budget for your temperature application project? Push a button and get pricing from a
friendly and knowledgeable JMS sales engineer.
SWIFTYCALC™ HELPS YOU:
- Quantify the design possibilities for your thermowell application.
- Document temperature de-rated thermowell strength calculation results and drawings to match.
- Promptly establish list pricing for your budgetary needs.
To sign up for SwiftyCalc, call 1.800.873.1835 or visit us at
https://www.jms-se.com/swiftycalc/ |
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+ Swifty Tips on Thermowell Design |
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- For optimal strength, just think of Swifty's High School basketball team - short, fat and slow. The same
things that kept Swifty out of the basketball game and in the temperature game will provide strength to your thermowell
installation.
- "Short" immersion lengths reduce drag and stress at root.
- "Fat" thermowells, at least at the root, increases the strength of the well at the weakest point of its structure. Enlarging the tip decreases the wake frequency of the thermowell, often without significant reduction to the installed natural frequency. Since keeping your thermowell's wake frequency significantly below its installed natural frequency is key to avoiding vibration induced damage, enlarging the tip can often cause your thermowell to achieve longer immersion lengths without encountering dangerous resonance conditions induced by Von Karman vortices.
- "Slow" process fluids are unlikely to cause a thermowell to approach an unacceptable natural frequency or experience an
unacceptable stress at its base.
- For optimal temperature measurement, think of a more traditional basketball team - long, slender and fast.
- "Long" thermowells avoid or reduce the effects of stem loss error.
- "Thin" thermowells decrease the response time of your sensing element for the same reason that it takes longer to
fry a Thanksgiving turkey than it does a chicken wing.
- "Fast" process fluids provide optimal heat transfer again accelerating the response time of your sensing element.
- For the best blend of the strength and measurement, try SwiftyCalc. Applying the PTC 19.3 standard, it provides you
with maximum theoretical immersion lengths and flow rates so that you can design your thermowell with an eye towards both
strength and measurement requirements without giving short shrift to either. For special reports dealing with corrosion
allowances and more, please contact JMS at 1-800-873-1835.
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SWIFTYCALC™ HELPS YOU:
- Quantify the design possibilities for your thermowell application.
- Document temperature de-rated thermowell strength calculation results and drawings to match.
- Promptly establish list pricing for your budgetary needs.
Call 1-800-873-1835 for a thermowell quote today!!
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