Steam traps
- Manufacturer: Yoshitake
- Material: stainless steel
- Condensate drain type: thermodynamic
- Maximum operating pressure: 4.6MPa
- Maximum working temperature: 425(°C)
- Maximum consumption: 830kg/h
- Manufacturer: Yoshitake
- Material: carbon steel, stainless steel
- Condensate drain type: float
- Maximum operating pressure: 1.4MPa
- Maximum working temperature: 220(°C)
- Maximum consumption: 24000kg/h
- Manufacturer: Yoshitake
- Material: stainless steel
- Condensate drain type: thermostatic
- Maximum operating pressure: 1.0MPa
- Maximum working temperature: 185(°C)
- Manufacturer: Yoshitake
- Material: stainless steel
- Condensate drain type: thermostatic
- Maximum operating pressure: 2.1MPa
- Maximum working temperature: 220(°C)
- Manufacturer: Yoshitake
- Material: stainless steel
- Condensate drain type: thermostatic
- Maximum operating pressure: 2.1MPa
- Maximum working temperature: 220(°C)
- Manufacturer: Yoshitake
- Material: stainless steel
- Condensate drain type: thermodynamic
- Maximum operating pressure: 4.2MPa
- Maximum working temperature: 425(°C)
- Maximum consumption: 710kg/h
- Manufacturer: Yoshitake
- Material: forged steel, stainless steel
- Condensate drain type: float
- Maximum operating pressure: 2.1MPa
- Maximum working temperature: 220(°C)
- Maximum consumption: 700kg/h
- Manufacturer: Yoshitake
- Material: malleable iron
- Condensate drain type: float
- Maximum operating pressure: 2.1MPa
- Maximum working temperature: 220(°C)
- Maximum consumption: 1950kg/h
- Compound: 1/2"
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CONDENSATION DRAINER AND WHAT IT IS NECESSARY FOR
Before determining why a steam trap is needed, it is necessary to understand what a steam condensate system is, what functions are performed by steam and, accordingly, condensate. Steam is water that turns into a gaseous state and can be used to transfer energy over a distance. The greatest value is the heat of phase transition or specific heat of vaporization and condensation r, kJ / kg. The value of the heat of vaporization depends on the parameters of the steam. When the steam is cooled, condensation occurs with the release of useful latent heat of condensation. The heat of condensation is transferred to the product or the heated medium, the vapor condenses and becomes a liquid (condensate). Since condensate does not have as much energy as steam, it must immediately be completely removed from the heat transfer zone. If this is not done, then the condensate prevents the supply of fresh steam to the heat exchange surfaces, the heat consumption decreases, which leads to disruption of the technological process.
Photo: Samples of various steam traps at the OPEKS ENERGOSYSTEM warehouse
There is another reason why it is necessary to separate condensate from steam, since steam moves at a high speed in pipelines and the presence of condensate has a destructive effect on pipelines, valves and equipment, causing water hammer.
To separate steam, as a valuable energy carrier, from condensate, the following types of steam traps are used: mechanical (float and "inverted cup" type), thermodynamic, thermostatic, bimetallic.
For clarity, consider an example of condensate drainage from the steam jacket of a storage heater.
If the condensate is not discharged in a timely manner, then the stagnation of condensate in the heat exchanger (steam jacket) leads to a decrease in the product temperature and its uneven distribution. Also, in the absence of a condensate drain, significant energy losses are inevitable in the form of a passage of uncondensed steam, followed by its useless condensation and heat release in the condensate line. When organizing condensate drainage, it is important to take into account the possible presence of non-condensable gases, which must also be removed in order to avoid air pockets, and as a result of insufficient heating by steam of the medium inside the vessel with a steam jacket.
From this we can conclude that the condensate drain is a kind of automatic valve that passes condensate through itself, removes gases and retains steam. A steam trap is an essential and essential element for any steam condensate system.
For the automatic discharge of condensate and non-condensing gases (air, carbon dioxide), condensate drains have been developed with different operating principles. The mechanism of their operation is based on the difference in the physical properties of vapor and liquid - this is specific gravity, temperature or pressure. There are three main types of steam traps: mechanical (float steam traps, inverted cup steam traps), thermodynamic and thermostatic.
The most widely used are mechanical - float steam traps and inverted cup steam traps, since the principle of their operation ensures constant condensate discharge and sufficient system reliability (no condensate blocking) during water hammer.
CONSTRUCTION FEATURES OF MECHANICAL CONDENSER DRAINS
Inverted glass
The regulating body is a poppet valve actuated by means of swivel joints, a float in the form of an inverted bowl. A built-in filter removes particulate matter.
Feature: high resistance to water hammer, even with destruction, condensate drainage continues.
Lever float
The regulating body is a globe valve actuated by means of swivel joints by a spherical float. An integrated air vent removes non-condensable gases.
Feature: built-in filter and air vent, the float has a strong, reliable connection and high resistance to water hammer.
Free floating float
A free-floating float, with its surface regulates the opening of the outlet calibrated opening in proportion to the level of the incoming condensate.
Feature : the need to ensure a high class of cleanliness of the surface of the float, in order to exclude loose closure of the outlet valve
WORKING CYCLE OF MAIN TYPES OF CONDENSER VALVES
(COMPARATIVE CHARACTERISTICS OF CONDENSER DRAINS)
Inverted glass
Condensate drain
At start-up, the condensate drain is filled with condensate from the previous cycle, the bowl is recessed, the outlet clan is open, air is removed and carried out into the condensate line through the outlet in the upper part of the bowl.
Air venting and vapor recovery
Air and steam are collected under the glass, displacing condensate. At the same time, the glass floats up and closes the outlet valve. Air is removed through a hole in the glass. A small amount of steam also passes through the same hole. When steam condenses in the upper part of the glass, the glass is filled with condensate, lowered and opens the valve for condensate drainage.
Condensate and air discharge
The steam trap operates in a cyclical manner, raising and lowering the bowl and, accordingly, opening and closing the drain valve.
Lever float
Air release
At start-up, air is vented through a thermostatic air vent, which opens below the saturation temperature of the steam.
Condensate drain and steam recovery
The incoming condensate fills the float chamber and the hollow float floats to open the outlet valve. The opening of the valve is proportional to the amount of incoming condensate.
Discharge of condensate and air
The entry of steam and the absence of condensation helps to lower the float and close the outlet valve.
Free floating float
1. Air release
When cold, the X-element (air vent) fully opens the bypass discharge port. In this case, there is a continuous de-aeration of the steam system.
2. Condensate drain
At the end of the removal of cold condensate and air, the X-element is closed. The floating float regulates the opening of the orifice in proportion to the flow rate of the incoming condensate, responding to sudden changes in the flow rate of the condensate.
3. Capturing steam
If there is no condensate inflow, the float lowers and locks the orifice. The maintained level of condensate creates a water seal on the orifis, preventing the escape of steam. In operating mode, when hot air enters the trap, the X-element is immediately triggered by a drop in temperature and automatically opens the vent valve.
Thermostatic condensate drain
Condensate discharge
In a thermostatic steam trap, when it is filled with condensate colder than steam, the medium inside the bellows is compressed, deforming it and opening the outlet valve to drain condensate and air bubbles.
Steam trapping
When steam enters the thermostatic steam trap, the medium in the bellows expands, deforms the siphon and closes the condensate drain valve. While the siphon is surrounded by steam, the valve is closed.
Bimetallic steam trap
Condensate discharge
In bimetallic steam traps, when filled with condensate, the bimetallic plate deforms, opening the outlet valve to drain condensate and air bubbles.
Steam trapping
When steam enters, the bimetallic plate changes its spatial position and closes the condensate drain valve. While the plate is surrounded by steam, the valve is closed.
Thermodynamic steam trap
Condensate discharge
The condensate fills the cavity of the thermodynamic steam trap, lifts the disc and drains the condensate. The condensate washes all the internal hydraulically connected cavities of the trap.
Steam trapping
When steam enters the cavity under the disc at high velocity, the pressure under the disc decreases and the disc descends, closing the outlet valve. The pressure above the disc decreases, as a result of cooling and condensation of steam, the disc rises and releases condensate with a small portion of steam and so on cyclically. In order to reduce the cooling of steam due to environmental influences and to reduce the cycle of opening and closing the valve, an insulating cavity (cover) filled with air is provided, as well as a steam jacket.
MECHANICAL CONDENSER DRAINS COMPARISON
ADVANTAGES OF CONDENSER VALVES
Inverted glass:
- resistant to pollution;
- condensate drainage with saturation temperature;
- in the event of a breakdown or water hammer, it always remains in the open position, ensuring reliable drainage of condensate, despite steam leakage;
- maintainability;
- durability.
Lever float:
- installation both horizontally and vertically of one condensate drain;
- durability;
- maintainability;
- resistance to water hammer;
- fast air removal;
- replacement of parts without dismantling the pipeline
- fast response to changes in loads and condensate flow;
- condensate drain with saturation temperature.
Free-floating float:
- resistance to water hammer;
- durability;
- maintainability;
- replacement of any part without dismantling from the pipeline;
- only one moving part;
- fast air removal;
DISADVANTAGES OF CONDENSATION DRAINS
Inverted glass:
- slow venting of air;
- cyclical operation;
- inevitable steam losses;
- concentric valve wear and loss of tightness;
- sensitive to fluctuations in inlet pressure;
- a constant presence of a water seal is required.
Lever float:
- concentric valve wear;
- possible separation of the lever from the float during a water hammer.
Free-floating float:
- during installation, deviation from the axis is allowed no more than 5˚;
- susceptibility to water hammer (deformation of the float).
- if the X-element is defective, steam loss is inevitable.
CONDENSER DRAIN APPLICATION
First of all, it is necessary to determine the type of steam trap (mechanical, thermodynamic or thermostatic) based on the purpose and place of installation. To do this, you can use the table:
TYPE OF | Basic equipment | Light load | Drainage | Steam satellite |
Mechanical (float) | + | + | + | + |
Mechanical (inverted glass) | + | + | + | + |
Thermodynamic | - | + | + | + |
Bimetallic | - | + | + | + |
Thermostatic | - | - | - | + |
CONDENSER DRAIN HOUSING MATERIAL
The material is selected based on the maximum operating temperature and pressure, as well as the presence of aggressive impurities in the condensate. Typically, the trap body is made of gray or ductile iron, carbon steel or stainless steel. Cast iron is the most common material for steam traps, as it provides low cost, corrosion resistance and sufficiently high operating pressures up to 25 bar.
The maximum allowable pressure and temperature is not only limited by the body material, but also by the resistance of other components such as seals. In addition, different standards such as ASME or DIN may influence the indication of maximum parameters.
Bandwidth
This is the main technical indicator of a steam trap and depends on many factors. This is, firstly, the standard size, and secondly, the throughput jet (orifis), the caliber of which is selected based on the maximum pressure drop across the condensate drain. The higher the capacity, the greater the condensate flow rate that the trap can drain from the system.
I would like to note that the connection diameter does not affect the above parameters, since one and the same steam trap can be made from DN20 to DN50.
Then how to choose the right size and orifice (jet)?
To do this, you need to know two parameters - the maximum condensate flow rate and the pressure drop (the pressure difference in the steam line and the condensate line). As an example, let's assume a condensate flow rate of 1150 kg / h with a pressure drop of 6 bar (0.6 MPa).
Since the number of the orifice (jet) reflects the maximum operating pressure drop, we select the orifice closest and larger than the specified differential value - this is # 10. The required parameters are provided by the model of the Yoshitake TSF-10 condensate drain ; on the diagram, the operating point is under the orifice line with number 10.
Position in the space of the condensate drain
The steam trap must be installed horizontally or vertically on the pipeline. There are steam traps that can be installed only on horizontal or only vertical pipes due to their limited design features. There are also models (for example TSF-10, TSF-11 from Yoshitake) that can be installed simultaneously in horizontal and vertical pipes due to the ability to rotate the internal mechanism along the axis of the steam trap.
Connection diameter
The diameter of the condensate drain connection is taken in accordance with the diameter of the condensate line, which is calculated taking into account the condensate flow rate and the formation of flash steam. The greater the amount of secondary steam and the length of the condensate line, the correspondingly larger its diameter should be.
For a first approximation, the minimum diameter of the condensate line to the condensate drain is taken in accordance with the table:
Maximum condensate load | Equipment outlet pipe size |
Less than 200 kg / h | 15 mm [1/2 in.] |
200 - 500 kg / h | 20 mm [3/4 inch] |
0.5 - 1 t / h | 25 mm [1 inch] |
1 - 2 t / h | 32 mm [1 1/4 inches |
2 - 3 t / h | 40 mm [1 1/2 inches] |
3 - 5 t / h | 50 mm [2 inches] |
More than 5 t / h | parallel installation of several steam traps |
Basic Recommendations for the installation of steam traps
1. For a group of heat exchangers or a multi-section heat exchanger, it is not allowed to install one common condensate drain as this leads to pressure imbalance, condensate flooding and water hammer.
As an example, consider a three-section heater with a common steam and condensate header and one condensate drain. Sequential installation of sections allows you to increase the heat exchange surface and heat output of the heater. The amount of condensate formed in each section is different, since the first section is in contact with the coldest air, and the last - with the already heated one. In this case, the pressure after the first section will be lower than after the last one. The pressure imbalance creates a kind of "short circuit" that prevents condensate from draining from the heat exchangers and leads to their flooding.
Installing an individual condensate drain after each heat exchanger completely eliminates the above problems.
But there are times when the system is already existing, and it is not possible to install individual air conditioners. In such cases, an oversized collector can be installed.
However, it will not be possible to completely eliminate the pressure imbalance, so the installation of steam traps at each source remains the preferred option.
2. It is necessary to exclude the installation of steam traps in the upper part of the rise of the condensate line in order to avoid the formation of steam locks. When designing and installing condensate drain lines, it is necessary to ensure that the condensate lines are laid without U- shaped sections. The diameter of the condensate drain pipes must correspond to the condensate flow rate.
It is not uncommon for steam-using enterprises to face the problem of an unstable heat transfer process, which is expressed in fluctuations in the temperature of the heated medium or product. For example, at a certain moment, the product temperature begins to decrease, although the control system is working properly, and then it rises sharply again to the set values. Moreover, this process occurs cyclically.
The reason for this phenomenon may be the so-called "steam closure". This happens when a vapor "plug" forms between the equipment and the steam trap, blocking the drainage of condensate. You should not look for the reason in the malfunction of the steam trap, since its task is to retain steam. This is most likely caused by the configuration of either the heat exchange equipment and / or the condensate outlet lines.
The reason for the "short circuit of steam"
A steam short circuit occurs when the system does not allow condensate to drain from the bottom of the condensation zone to the trap by gravity. This can be caused not only by the design of the equipment (tilting vats, drying cylinders), but also by the incorrect configuration of the pipelines, which can be corrected. Here are some typical cases of incorrect installation:
Do not install steam traps at the top of the rise of the condensate line. The resulting vapor lock will block it until the steam in this section is completely condensed.
Sagging of the pipeline, especially in long sections, also leads to blockage.
Even if the piping is installed horizontally, long sections in front of the condensate drain with a narrowed diameter cause steam to close.
How to deal with steam plugs?
The simplest option is to install an external bypass line with a shut-off valve on the steam trap in areas with a risk of vapor lock. By opening the valve, the steam bypass can be adjusted by removing the steam plug in front of the condensate drain.
3. Drainage of condensate from steam pipelines must be organized, providing for the so-called "pockets" of the required volume for the collection and subsequent removal of condensate.
An example of correct drainage of steam lines:
4. It should be remembered that for heat exchangers and other equipment with intensive condensation, only float-type steam traps should be installed to ensure continuous drainage of condensate.
When selecting steam traps, it is important to consider the safety factor. If the exact flow rate of condensate is not known, then it is necessary to overestimate the calculated values for the flow rate of condensate, so that the steam trap is selected with a capacity margin. If the trap is too small, there is a risk of condensation build-up in the equipment, reduced performance, water hammer and cavitation. All these factors can lead to failure and destruction of steam-using equipment.
The OPEKS ENERGOSYSTEMY company continuously maintains a wide range of steam traps of various types in the warehouse. Our engineers will select the correct model of the steam trap and offer a complete solution for the modernization or design of a new steam system.