A scary part on-site is when you try to install the Thermowell inside the Nozzle and you realize the Thermowell Outer Diameter (OD) larger than Nozzle Inside Diameter (ID)?.

Image Courtesy: Parker

This simple thing will lead to great delays since you can’t just insert some other thermowell as they go through W.F.C calculations, material selection, etc.

Nobody would want this to happen, so Let’s explore the precautions and recommended practices.

What factors are to be evaluated for ensuring the Thermowell gets properly inserted in Nozzle I.D

1. Nozzle Schedule

Even 1&1/2 inch pipe won’t have the same I.D all the time.

The schedule of the pipe needs to be checked.

As it is logical the Higher the schedule (like Std, XS, XXS etc) the smaller the I.D available.

Software’s like pipe pro can be used to get dimensions.

2. Cladding on Thermowell

Thermowell consumes a lot of material as compared to the diaphragm of transmitters etc.

So always it is not a cost-effective option to upgrade thermowell material to Alloy C-276 or other exotic material until it’s a dire necessity.

Another option sometimes used (depends on application) is to provide cladding on thermowell.

This also consumes little space and must be accounted for.

3. Clearance Space

This one important consideration that gets overlooked.

Handling changes at the initial stages of the project is very easy, but the very same changes at a later stage have a significant impact.

A classic example is Wake frequency calculation that caused the Thermowell base O.D to increase. (Maybe in the later stage process data got revised or WFC was incorrectly done etc)

Now if we have exact cut to cut the distance between nozzle I.D and Thermowell O.D then it is very difficult to accommodate such last-minute changes.

Few more examples are listed below:-

Thermal expansion at higher temperatures is an issue.

As indicated above maybe at a later stage cladding of thermowell is recommended and this will consume some space.

Also sometimes the Pipe spec has a certain schedule but for ease of welling, a different schedule is selected for vessel nozzle.

Hence it is preferred not to take the exact cut to cut the distance and keep some clearance.

Beware of illegal Ways

Polishing of thermowell to fit into the Nozzle:-

Sometimes on-site people polish the thermowell to reduce its O.D so that it fits in the nozzle.

This is an unsafe practice. As this risks the integrity of thermowell design and can lead to catastrophic failure.

Thanks for reading !!

I hope it has been of value to you.

PS: This is as per the best of my current understanding.

Comments

PLC Program for Mixing Tank

Create a ladder diagram for controlling a batch mixing process. Implement a PLC program for mixing tank or Mixing Process using PLC Ladder Logic. PLC Program for Mixing Tank Fig : Mixing tank A tank is used to mix two liquids. The required control circuit operates as follows: A. When the START button is pressed, solenoids A and B energize. This permits the two liquids to begin ﬁlling the tank. B. When the tank is ﬁlled, the ﬂoat switch trips. This de-energizes solenoids A and B and starts the motor used to mix the liquids together. C. The motor is permitted to run for 1 minute. After 1 minute has elapsed, the motor turns off and solenoid C energizes to drain the tank. D. When the tank is empty, the ﬂoat switch de- energizes solenoid C. E. A STOP button can be used to stop the process at any point. F. If the motor becomes overloaded, the action of the entire circuit will stop. G. Once the circuit has been energized, it will continue to operate until it is manually stopped. Solution...

What is Relay? How it Works? Types, Applications, Testing

We use relays for a wide range of applications such as home automation, cars and bikes (automobiles), industrial applications, DIY Projects, test and measurement equipment, and many more. But what is Relay? How a Relay Works? What are the Applications of Relays? Let us explore more about relays in this guide. What is a Relay? A Relay is a simple electromechanical switch. While we use normal switches to close or open a circuit manually, a Relay is also a switch that connects or disconnects two circuits. But instead of a manual operation, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit. Relays can be of different types like electromechanical, solid state. Electromechanical relays are frequently used. Let us see the internal parts of this relay before knowing about it working. Although many different types of relay were present, their working is same. Every electromechanical relay consists of an consists of an Elect...

Chlorine dioxide Analyzer Principle

Chlorine dioxide measurement Chlorine dioxide (ClO2) is an instable, non-storable, toxic gas with a characteristic scent. The molecule consists of one chlorine atom and two oxygen atoms – represented in the chemical formula ClO2. It is very reactive. To avoid the risk of spontaneous explosions of gaseous chlorine dioxide or concentrated solutions, it is generally handled in dilution with low concentrations. ClO2 is soluble in water, but tends to evaporate quickly. Typically it is prepared on site, for example from hydrochloric acid and sodium chlorite. The procedure provides solutions with approx. 2 g/l ClO2 that can be safely handled and stored for several days. Image Credits : krohne Sensor Parts : Reference electrode Applied chlorine dioxide specific potential Current needed to maintain the constant potential Counter electrode Measuring electrode The disinfection effect of ClO2 is due to the transfer of oxygen instead of chlorine, so that no chlorinated byproducts are formed. C...

TILI Automation

Search This Blog