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Series 10&15 Straight Shank with .260" Bore Series 20&25 Tapered Shank with .260" Bore Series 30&35 Straight Shank with .385" Bore Series 40&45 Tapered Shank with .385" Bore |
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Tempco offers standard and custom manufactured Thermowells and Protection Tubes which afford you an excellent variety of ways to protect your temperature sensor from high velocity, high pressure and corrosive and harsh environments. |
Well failures, in most cases, are not due to the effect of pressure and temperature. The calculations necessary to provide adequate strength, under given conditions, are familiar enough to permit proper choice of wall thickness and material.
Less familiar, and more dangerous, are the vibrational effects to which wells are subjected. Fluid, flowing by the well, forms a turbulent wake (called the Von Karman Trail) which has a definite frequency based on the diameter of the well and the velocity of the fluid. It is important that the well has sufficient stiffness so that the wake frequency will never equal the natural frequency of the well itself. If the natural frequency of the well were to coincide with the wake frequency, the well would vibrate to destruction and break off in the piping.
On the following pages, a recommended velocity rating can be found for every standard well length and material cataloged. To reduce the complexity of presenting this information, the ratings are based on operating temperatures of 1000ºF for wells made of Carbon Steel (C-1018), ANSI 304 ANSI 316. Values for brass wells are based on 350ºF operation. Limits for Monel are based on 900ºF service. Slightly higher velocity is possible at lower temperatures.
Where single values appear in the velocity tables, these may be considered safe for water, steam, air or gas. In the shorter insertion lengths, consideration is given to the velocity pressure effect of water flowing at higher velocities. The values in parenthesis, therefore, represent safe values for water flow while the unbracketed value may be used for steam, air, gas and similar density fluids.
It should be pointed out that the values given are extremely conservative, and intended primarily as a guide. Wells are also safe if the resonant frequency is well below the wake frequency or if the fluid velocity is constantly fluctuating through the critical velocity point. Nevertheless, if the installation is not hampered by the use of a sufficiently stiff well, we recommend the values should not be exceeded.
If you have operating conditions requiring special well designs, our Engineering staff is available to assist you. Consult Tempco with your requirements.
