Steam is one of the most efficient heat carriers, which instantly transfers all thermal energy to the consumer upon contact with the heat transfer device. In addition, it is easy to give the required characteristics to the gaseous phase - the required temperature and pressure.
But when steam and equipment interact, a large amount of condensate is formed, which leads to water hammer, a decrease in thermal power and a deterioration in the quality of the gaseous phase. To combat droplets of water falling on the surface of the pipes, it is necessary to use a steam trap. At foreign enterprises, such fittings are called a "steam trap", which fully reflects the functional purpose of the device.
Steam Traps
Steam traps are one of the types of industrial pipeline fittings, which is designed forprevent condensation when using steam and more efficient use of its thermal energy.
As a result of a series of experiments, it has been proven that the introduction of a steam trap into a set of equipment saves up to 20% of the useful energy of live steam.
Types of steam traps
Depending on the design and the implemented principle of operation, pipeline fittings can be mechanical, thermodynamic or thermostatic. Any type of steam trap must meet two basic requirements:
- condensate removal without loss of acute gaseous phase;
- automatic venting of the system.
Condensate is formed due to heat loss by steam in heat exchangers, as well as during the heating of pipeline installations, when part of the gaseous phase turns into water. The loss of a large amount of moisture reduces the energy efficiency of the equipment, accelerates its wear. That is why it is so important to fight him.
Mechanical steam traps
Mechanical fittings are the most reliable, and therefore popular, "steam trap". Its principle of operation is based on the difference in the densities of water vapor and condensate, and the main actuating element is a float. Depending on the design of the float, the following types of reinforcement are distinguished:
- steam float spherical open or closed type steam trap;
- bell-type float element, or inverted closed steam trap.
Each type of reinforcement works in its own waya certain scheme, has advantages and disadvantages, the knowledge of which will allow you to implement the most efficient scheme of work in the enterprise.
Spherical Float Steam Traps
The basis of the design of this type of valve is a spherical float. It is located in the internal cavity of the exhaust valve and is connected to the lever valve. In addition, the steam trap includes a thermostatic valve.
The operation principle of a ball float steam trap can be divided into two steps:
- Condensate enters the device through the pipe, fills the internal cavity and raises the float, which pulls the valve lever and opens the hole for water removal.
- When hot steam enters the device, the thermal valve is activated, steam begins to accumulate in the cavity and causes the float to sink to the bottom, the outlet is blocked.
This is how the condensate is separated from the steam. Due to the presence of a thermostatic valve in the design, the released gas is automatically removed, and the appearance of an air film in the cavity, which jams the device, is also prevented.
Advantages and disadvantages
A typical representative of a spherical float valve is the FT-44 steam trap. We will analyze the main pros and cons of devices using its example. The main thing that experts note is the insensitivity of the device to variable loads.
The device is capable of continuously draining condensate both at saturated vapor temperature and under heavy loads. The stable and continuous separation of non-condensable gases is another advantage of the valve. All this, combined with a long service life, is due to the simple design of the device.
The main disadvantage of the device is its large size, which increases heat loss to non-insulated elements of the case. High sensitivity to water hammer and exactingness to “steam purity” (valve silting is possible) are two more disadvantages of this type of steam traps.
Bell type steam traps
As the name implies, the main element of this type of steam trap is the bell, or "inverted cup" float. The device itself has a cylindrical shape, rather bulky (larger than the previous representative), but has a large set of advantages.
In the initial position, the inverted float is at the bottom of the valve and its bottom rests against the vertical tube. A spool lever is attached to the glass, which is located in the valve cover. The separation of steam from condensate occurs in four steps:
- Through the inlet, water enters the device, fills the internal cavity and, under pressure, pours out through the open spool.
- Steam, entering the system, begins to put pressure on the bottom of the float, causing it to float in the volume of condensate and close the spool.
- Steam, being inside the glass, startsdecompose into liquid and gaseous phases. The latter passes through a special channel in the bottom, enters the spool and pushes it back.
- The condensate and the remaining gaseous phase leave the glass through the hole in the bottom, the float begins to release, opening the spool again.
Cyclic repetition of the described operations results in a complete and effective separation of live steam from condensate. This technology was patented in 1911, but remains relevant to this day.
Pros and cons
Zamkon's steam trap is a prominent representative of the inverted cup valve. We will analyze the pros and cons of devices in this category using his example.
Here, large dimensions are also considered a minus, which greatly affects the loss of thermal energy on non-insulated elements. Another disadvantage experts call the limited throughput, which does not allow the use of fittings on high-performance equipment.
The benefits of a steam trap are much greater. Firstly, the spool is not subject to contamination, which increases the reliability of the device. Secondly, the fittings are not afraid of water hammer. Thirdly, condensate removal is possible even at high temperatures.
In the event of failure, the exhaust valve remains open, which saves the equipment complex from breakdown. Finally, all additional components and assemblies, such as filters or check valves, are installed directly in the steamsteam trap. This reduces the loss of thermal energy and reduces the size of the entire set of devices.
"Thermal" fittings
Thermostatic and thermodynamic steam traps operate on the ability of various fluids to expand and contract as the temperature rises or falls. Together with an increase in temperature, for example, when steam enters, the locking element expands and closes the channel that drains the condensate.
The principle of operation of other devices is based on a change in pressure inside the system as a result of the interaction of a dense (cold) and rarefied (hot) medium. The main elements in such devices are bimetallic plates. The photo shows the steam trap with a bimetal element.
This type of equipment has a complex design and is rarely used in practice. Low popularity is also due to complex and often impossible repairs. The use of equipment of this type is justified only in especially critical industrial installations.
