Definition: A condensate pot collects and traps condensate (the liquid formed when steam cools and condenses) before it can interfere with the operation of equipment or instrumentation. These condensing pots separate the condensate from the steam and protect sensitive instruments and control devices from damage or malfunction.
What is a Condensate Pot?
A condensate pot is a device used in the flow measurement of steam using a differential pressure flow transmitter, in which the orifice is the primary sensing element. The main aim of this condensate pot is to protect the differential pressure flow transmitter from the excessive temperature of the steam and from inaccurate flow measurement.
The condensed steam is present between the tapping of the orifice plate and the bottom of the tube, which connects to the differential pressure flow transmitter, and the condensate pot between the orifice plate and the transmitter has a major volume of this condensate or condensed steam.
This condensed steam protects the differential pressure flow transmitter’s sensitive material against high temperatures. Suppose direct steam is hitting the transmitter; sometimes condensate will also form, which will result in inaccurate flow measurements. Hence, the condensate pot will protect the transmitter and also help in getting accurate measurements of flow.
Why is Condensate Pot Required?
Flow measurement is one of the most important parameters and is done using various types of techniques. Flow measurement requires very accurate transmitters because an inaccurate flow measurement can lead to various problems. There are various techniques of flow measurement available, like differential pressure flow measurement, magnetic type flow measurement, ultrasonic type flow measurement, Coriolis mass flow meter, and orifice flow meter. Amongst these, the differential pressure flow measurement technique is the most widely used.
Flow measurement using the differential pressure flow measurement technique is widely used for measuring various media. Liquid, air, and even steam flow can be measured using a differential pressure flow transmitter.
Let us be more specific regarding the differential pressure flow measurement technique. Here, we will be talking about the orifice plate as a primary element for flow measurement. In liquid, the orifice is at a height above the flow transmitter, and the flow transmitter will be installed below this orifice plate.
The reason for installing the flow transmitter below the orifice in liquid is that many times, vapors or gases form in liquid service. So, if the flow transmitter is above the orifice assembly, then this vapor or gas will reach the flow transmitter, resulting in inaccurate flow measurements. Similarly, in the case of gas flow measurement, the flow transmitter is always mounted above the orifice plate. The reason is that in gas service, the gas can condense, and if the flow transmitter is installed below the orifice plate, then the condensed gases will stay on the transmitter tapping and result in inaccurate measurements.
Now, confusion arises when we need to measure the flow of steam using an orifice-type differential pressure flow transmitter. In this case, a special type of arrangement is used. A special device called a condensate pot is used in the steam flow measurement technique using differential pressure flow measurement by an orifice plate. The condensate pot is placed between the orifice plate and the flow transmitter. Also, the flow transmitter in this technique is always installed below the condensate pot. So, on top will be the orifice plate, below it will be the condensate pot, and at the bottom will be the flow transmitter.
Working of Condensate Pot
A condensate pot is a device used in the flow measurement of steam in a thermal power plant using a differential pressure flow transmitter, in which the orifice is the primary sensing element. The main aim of this condensate pot is to protect the differential pressure flow transmitter from the excessive temperature of the steam and from inaccurate flow measurement.
The condensed steam is present between the tapping of the orifice plate and the bottom of the tube, which connects to the differential pressure flow transmitter, and the condensate pot between the orifice plate and the transmitter has a major volume of this condensate or condensed steam.
This condensed steam protects the differential pressure flow transmitter’s sensitive material against high temperatures. Suppose direct steam is hitting the transmitter; sometimes condensate will also form, which will result in inaccurate flow measurements. Hence, the condensate pot will protect the transmitter and also help in getting accurate measurements of flow.
How to Install a Condensate Pot?
While using a condensate pot, the following things should be kept in mind:
- The condensate pot should always be between the orifice plate and the transmitter.
- The tube from the orifice plate to the transmitter should always be filled with condensed steam.
- Both high-pressure tapping and low-pressure tapping should be filled with condensed steam.
- There should not be a difference in height between high-pressure tapping and low-pressure tapping. This will result in inaccurate flow measurements.
- While using a condensate pot, no leakage should be present. If there is any leakage, then the condensate will come out of it, and steam will reach the transmitter and eventually damage it.
- The condensate pot should be properly supported. If support is not proper, then due to vibrations, leakage will occur over a period of time.
- Always use proper isolation valves between the orifice tapping and the condensate pot to isolate the condensate pot in case any requirement arises in the running line.
One important thing to keep in mind is that whenever the impulse line is empty, and steam is introduced in this line, properly flush the steam through the drain point of the flow transmitter assembly. Make sure to keep the flow transmitter isolated from the manifold.
Another important thing that every instrument engineer should keep in mind is that whenever the line is totally empty and steam is introduced into the line, keep the flow transmitter isolated. The isolation should be done through the manifold.
The reason is that when the line is empty and steam is introduced, there is a high chance that this steam will directly hit the transmitter, and it can damage the transmitter. Thus, to avoid this situation, keep the transmitter isolated when such a condition arises. Let the line be used for transferring steam for a few hours. After a few hours, like 4 hours to 5 hours, the condensate will be properly collected in the condensate pot and the whole assembly of tubing. After that, we can take the flow transmitter in line.
Applications of Condensate Pot
The primary application of a condensate pot is to enhance the accuracy of differential pressure flow measurement in steam or vapor applications. They are used to prevent condensation from affecting differential pressure measurements and minimize gauge line errors. They are widely used in the following industries.
- Power Plants
- Petrochemical
- Chemical Plants
- steel plants
- Refineries
Advantages of Condensate Pot
- Provides accurate flow measurement
- Collects and traps moisture and foreign material and prevents corrosion in the pipeline.
- Protects the measuring instrument
- It forms a liquid barrier between the hot gas and the instrument to safeguard it from moisture.
- Reduces the maintenance cost
- Improves the performance of the plant.
Conclusion:
The condensate pot collects and retains condensate, preventing damage to the metering system or manifold. By using a condensate pot, you can ensure accurate pressure and flow measurements and protect sensitive instruments from damage caused by condensate or other liquids in the process fluid.