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].
Thermowell design calculation software 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. The software also provides you with instant theoretical maximums for insertion length and flow rate. This software is perfect for faster response time and increased reliability in your temperature measurement system.
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 thermowell design Software Do For Me?
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 software tells you why and what you can do to design a well that will work.
Why do we run wake frequency calculations ?
- 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.
What this Thermowell Design Software do ?
- 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.