The structural form and working principle of the trap_Li Shenghui_Architectural Design_Architecture Chinese Network Introduction Traps play a role in steam blocking and drainage in steam heating systems. Choosing the appropriate trap can make the steam heating equipment Achieve maximum work efficiency. In order to achieve the best results, it is necessary to have a comprehensive understanding of the working performance and characteristics of various types of traps.
Introduction: Traps play a role in steam blocking and drainage in steam heating systems. Choosing a suitable trap can enable steam heating equipment to achieve the highest working efficiency. In order to achieve the best results, it is necessary to have a comprehensive understanding of the working performance and characteristics of various types of traps.
Keywords: Structural form of steam trap
Traps play a role in blocking steam and draining water in steam heating systems. Choosing the appropriate steam trap can make the steam heating equipment achieve the highest working efficiency. . In order to achieve the best results, it is necessary to have a comprehensive understanding of the working performance and characteristics of various types of traps.
There are many varieties of traps, each with different performance. When selecting a trap, you should first select its characteristics to meet the optimal operation of the steam heating equipment, and then consider other objective conditions. In this way, choosing the trap you need is correct and effective.
A steam trap must be able to "identify" steam and condensate in order to function as a steam barrier and drainer. "Identification" of steam and condensate is based on three principles: density difference, temperature difference and phase change. Therefore, three types of traps were manufactured based on three principles, classified into mechanical type, thermostatic type, and thermodynamic type.
1. Mechanical type trap
The mechanical type, also called the float type, uses the density difference between condensation water and steam to cause the float to rise and fall to drive the valve disc through changes in the condensation water level. Open or close to achieve the purpose of steam blocking and drainage. Mechanical traps have a small degree of subcooling and are not affected by changes in operating pressure and temperature. Water is discharged immediately and no water is stored in the heating equipment, allowing the heating equipment to achieve optimal heat exchange efficiency. The maximum back pressure rate is 80 and the working quality is high. It is the most ideal trap for production process heating equipment.
Mechanical traps include free float type, free semi-float type, lever float type, inverted bucket type, etc.
1. Free float type trap:
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The free float type trap has a simple structure. There is only one movable part inside, a finely ground stainless steel hollow float, which is both a float and an opening and closing part. It has no wearing parts and has a long service life. The "silver ball" Brand traps are equipped with a Y series automatic air exhaust device inside, which is very sensitive, can automatically exhaust air, and has high working quality.
When the equipment first starts working, the air in the pipeline is discharged through the Y series automatic air exhaust device, and low-temperature condensate water enters the trap. The liquid level of the condensate water rises, the float rises, the valve opens, and the condensate water It is discharged quickly, the steam enters the equipment quickly, the equipment heats up rapidly, the temperature-sensing liquid of the Y series automatic air exhaust device expands, and the automatic air exhaust device closes. The trap begins to work normally, and the float rises and falls with the condensate level, blocking steam and draining water. The valve seat of the free float type trap is always below the liquid level, forming a water seal, no steam leakage, and good energy saving effect. The minimum working pressure is 0.01Mpa, and it is not affected by fluctuations in temperature and working pressure within the range from 0.01Mpa to the maximum working pressure, and is continuously drained. It can drain condensation water at saturated temperature, and the minimum subcooling degree is 0℃. There is no water in the heating equipment, so the heating equipment can achieve the best heat exchange efficiency. With a back pressure rate greater than 85, it is one of the most ideal traps for production process heating equipment.
2. Free semi-floating ball trap:
The free semi-floating ball trap has only one semi-floating ball barrel as a movable part, with the opening facing downwards and the ball barrel It is both an opening and closing part and a sealing part. The entire spherical surface can be sealed, has a long service life, can resist water hammer, has no wearing parts, is trouble-free, durable and has no steam leakage. The back pressure rate is greater than 80, which can discharge condensation water at saturated temperature. The minimum subcooling degree is 0°C. There is no water in the heating equipment, so the heating equipment can achieve the best heat exchange efficiency.
When the device is just started, the air and low-temperature condensate in the pipe enter the trap through the launch tube. The bimetallic emptying element in the valve pops open the ball barrel. The valve opens, and the air and low-temperature condensed water enter the trap. Condensed water drains away quickly. When steam enters the ball barrel, the ball barrel generates upward buoyancy. At the same time, the temperature inside the valve increases, the bimetallic emptying element contracts, the ball barrel floats toward the valve port, and the valve closes. When the steam in the ball barrel turns into condensation water, the ball barrel loses buoyancy and sinks, the valve opens, and the condensation water is quickly discharged. When the steam enters the ball barrel again, the valve closes again, working intermittently and continuously.
3. Lever float type trap:
The basic characteristics of the lever float type trap are the same as the free float type. The internal structure is that the float is connected to the lever to drive the valve core. The condensate level rises and falls to switch the valve. The lever float type trap uses double valve seats to increase the condensate displacement, which can achieve a small volume and a large displacement, with a maximum drainage capacity of 100 tons/hour. It is the most ideal trap for large heating equipment.
4. Inverted bucket trap:
The inside of the inverted bucket trap is an inverted bucket that is a liquid level sensitive part. The opening of the bucket is downward, and the connecting lever of the inverted bucket drives the valve core. Open and close the valve. The inverted bucket trap can discharge air, is not afraid of water hammer, and has good anti-fouling performance. The degree of subcooling is small, the steam leakage rate is less than 3, the maximum back pressure rate is 75, there are many connecting parts, and the sensitivity is not as good as the free float trap. Since the inverted bucket trap relies on the upward buoyancy of steam to close the valve, it is not suitable for use when the working pressure difference is less than 0.1MPA.
When the device is just started, the air and low-temperature condensate in the pipeline enter the trap. The inverted bucket falls by its own weight. The connecting lever of the inverted bucket drives the valve core to open the valve, and the air and low-temperature condensate are quickly discharged. . When steam enters the inverted bucket, the steam in the inverted bucket generates upward buoyancy, and the connecting lever of the inverted bucket rises to drive the valve core to close the valve. There is a small hole in the inverted bucket. When part of the steam is discharged from the small hole, and the other part of the steam generates condensed water, the inverted bucket loses its buoyancy and sinks under its own weight. The lever connected to the inverted bucket drives the valve core to open the valve, and the cycle begins. Work, intermittent drainage.
5. Combined superheated steam trap:
The combined superheated steam trap has two isolated valve chambers. The upper and lower valve chambers are connected by two stainless steel pipes. It is composed of The combination of float type and inverted bucket type trap has an advanced and reasonable structure. Under the working conditions of overheating, high pressure and small load, it can promptly discharge the condensed water formed when the superheated steam disappears, effectively preventing the leakage of superheated steam. High quality work. The maximum allowable temperature is 600°C, the valve body is made of all stainless steel, and the valve seat is made of hard alloy steel. It has a long service life. It is a special trap for superheated steam. It has obtained two national patents and filled a domestic gap.
When condensate enters the lower valve cavity, the float ball of the auxiliary valve rises with the liquid level, and the float seals the steam inlet pipe hole. The condensate water rises to the main valve cavity through the water inlet pipe, and the inverted bucket falls by its own weight, driving the valve core to open the main valve and discharge the condensate water. When the condensate level in the auxiliary valve chamber drops, the float drops with the liquid level and the auxiliary valve opens. Steam enters the inverted bucket in the upper main valve cavity from the steam inlet pipe. The inverted bucket generates upward buoyancy, and the inverted bucket drives the valve core to close the main valve. When the condensate level in the auxiliary valve cavity rises again, the next cycle starts again with intermittent drainage.
2. Thermostatic traps
This type of trap uses the temperature difference between steam and condensate to cause the deformation or expansion of the temperature-sensing element to drive the valve core to open and close the valve. The thermostatic trap has a relatively large degree of subcooling, generally ranging from 15 degrees to 40 degrees. It can utilize part of the sensible heat in the condensation water. There is always high-temperature condensation water in front of the valve. There is no steam leakage, and the energy saving effect is significant. . It is the most ideal trap for steam pipes, heat tracing pipelines, small heating equipment, heating equipment, and small heating equipment with low temperature requirements.
Thermostatic traps include diaphragm box type, Bellows type, bimetallic sheet type
1. Diaphragm type trap:
The main action element of the diaphragm type trap is a metal diaphragm, which is filled with a For liquids with a vaporization temperature lower than the saturation temperature of water, there are two options to choose from, the valve opening temperature being 15°C or 30°C lower than the saturation temperature.
The membrane box type trap is particularly responsive, not afraid of freezing, small in size, resistant to overheating, and can be installed in any position. The back pressure rate is greater than 80, which can discharge non-condensable gas. The membrane box is strong, has a long service life, is easy to maintain, and has a wide range of uses.
When the device is first started, low-temperature condensation water appears in the pipeline, the liquid in the membrane box is in a condensation state, and the valve is in the open position. When the temperature of the condensed water gradually increases, the liquid in the membrane box begins to evaporate, the pressure in the membrane box rises, and the diaphragm drives the valve core to move in the closing direction. Before the condensed water reaches the saturation temperature, the trap begins to close. The membrane box controls the opening and closing of the valve as the steam temperature changes, thereby blocking steam and draining water.
2. Bellows-type trap:
The valve core of the bellows-type trap is a stainless steel bellows filled with a liquid whose vaporization temperature is lower than the water saturation temperature. The valve switch is controlled as the steam temperature changes. The valve is equipped with an adjustment bolt to adjust the operating temperature as needed. Generally, the subcooling adjustment range is 15°C-40°C lower than the saturation temperature. The back pressure rate is greater than 70, it is not afraid of freezing, is small in size, can be installed at any position, can discharge non-condensable gas, and has a long service life.
When the device is started, cooling condensate appears in the pipe, the liquid in the bellows is in a condensed state, and the valve core is in the open position under the elastic force of the spring. When the temperature of the condensate gradually rises, the liquid in the bellows begins to evaporate and expand. The internal pressure increases, deforms and elongates, driving the valve core to move in the closing direction. Before the condensate reaches the saturation temperature, the trap begins to close, and is controlled as the steam temperature changes. Valve switch, steam blocking and drainage.
3. Bimetal trap:
The main component of the bimetal trap is the bimetal temperature sensing element, which is heated and deformed as the steam temperature rises and falls, pushing the valve core to open and close. valve. The bimetal trap is equipped with adjustment bolts, which can adjust the operating temperature according to needs. Generally, the adjustment range of subcooling is 15℃-30℃ lower than the saturation temperature, and the back pressure rate is greater than 70. It can discharge non-condensable gas and is not afraid of freezing. The volume Small, resistant to water hammer and high pressure, it can be installed in any position. Bimetallic plates have fatigue properties and require frequent adjustments.
When the device is just started, low-temperature condensation water appears in the pipe, the bimetallic sheet is flat, the valve core is in the open position under the elastic force of the spring. When the temperature of the condensate gradually increases, the bimetallic temperature sensing element begins to bend and deform, and pushes the valve core to the closed position. The trap begins to close before the condensate reaches saturation temperature. The bimetallic piece controls the opening and closing of the valve as the steam temperature changes, blocking steam and draining water.
3. Thermodynamic traps
This type of trap is based on the phase change principle and relies on the different thermodynamic principles of flow rate and volume changes when steam and condensate pass through. Different pressure differences are generated up and down, driving the valve plate to open and close the valve. Because the working power of the thermodynamic trap comes from steam, the waste of steam is relatively large. It has a simple structure, is resistant to water hammer, has a maximum backlash of 50, is noisy, has frequent valve work, and has a short service life.
Thermodynamic traps include thermodynamic (disc type), pulse type, orifice plate type
1. Thermodynamic traps:
Thermal There is a movable valve piece in the power trap, which is both a sensitive part and an action actuator. According to the different thermodynamic principles of flow rate and volume changes when steam and condensate pass through, different pressure differences are generated up and down the valve plate, driving the valve plate to open and close the valve. The steam leakage rate is 3, and the subcooling degree is 8℃-15℃.
When the device is started, cooling condensation water appears in the pipeline, and the condensation water pushes open the valve plate by the working pressure and is quickly discharged. When the condensate water is discharged, the steam is subsequently discharged. Since the volume and flow rate of the steam are larger than the condensate water, a pressure difference is generated between the upper and lower parts of the valve plate, and the valve plate is quickly closed under the suction force of the steam flow rate. When the valve plate is closed, the valve plate is subject to pressure from both sides. The force-bearing area below the valve plate is smaller than the force-bearing area above. Since the pressure in the steam chamber of the trap comes from the steam pressure, the force on the upper surface of the valve plate is greater than the force below. Close tightly. When the steam in the steam chamber of the trap cools down and turns into condensate, the pressure in the steam chamber disappears. The condensate water pushes open the valve plate by the working pressure, and the condensate water continues to be discharged, working in a cycle, and draining water intermittently.
2. Disc steam insulated trap:
The working principle of the disc steam insulated trap is the same as that of the thermodynamic trap. A shell is added outside the steam chamber of the valve. The inner chamber of the shell is connected to the steam pipe, and the main steam chamber of the trap is insulated by the pipe's own steam. Make it difficult for the temperature of the main steam chamber to drop, maintain the steam pressure, and close the drain valve tightly. When condensation water is generated in the pipeline, the trap shell cools down and the trap begins to drain water; if no condensation water is generated on the superheated steam pipeline, the trap will not open and the working quality is high. The valve body is made of alloy steel and the valve core is made of carbide. The maximum allowable temperature of the valve is 550°C. It is durable and has a long service life. It is a special trap for high-pressure and high-temperature superheated steam.
3. Pulse trap:
The pulse trap has two orifice plates that adjust the valve switch according to changes in steam pressure drop. Even if the valve completely closes the inlet and outlet, it will still pass through the first , the second small hole is connected and is always in an incompletely closed state. Steam continues to overflow and the amount of steam leakage is large. This trap has a high operating frequency, severe wear, and short lifespan. It is small in size, resistant to water hammer, can discharge air and saturated temperature water, is close to continuous drainage, and has a maximum back pressure of 25, so it has few users.
4. Orifice plate type drain valve:
Orifice plate type drain valve selects orifice plates with different apertures according to different drainage volumes to achieve the purpose of controlling drainage volume. The structure is simple, but improper selection may result in insufficient drainage or a large amount of steam leakage. It is not suitable for steam-using equipment with intermittent production or steam-using equipment with large fluctuations in condensate water volume.
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