Brief introduction: The steam trap plays the role of blocking steam and draining water in the steam heating system. Choosing the right trap can make the steam heating equipment achieve the highest working efficiency. In order to achieve the best results, it is necessary to fully understand the working performance and characteristics of various types of traps.
Keywords: structural form of steam trap
The steam trap plays a role in blocking steam and draining water in the steam heating system. Choosing the right trap can make the steam heating equipment achieve the highest working efficiency. In order to achieve the best results, it is necessary to fully understand the working performance and characteristics of various types of traps.
There are many kinds of traps, each of which has a different performance. When choosing a trap, you should first choose its characteristics to meet the best operation of steam heating equipment, and then consider other objective conditions, so that choosing the trap you need is correct and effective.
The steam trap should be able to "identify" steam and condensed water, thus playing the role of blocking steam and draining water. "Identifying" steam and condensed water is based on three principles: density difference, temperature difference and phase change. According to these three principles, we have made three types of steam traps, namely mechanical, thermal static and thermal dynamic.
First, the mechanical trap
Mechanical type, also known as float type, uses the density difference between condensed water and steam to make the float rise and fall to drive the valve disc to open or close through the change of condensed water level, thus achieving the purpose of blocking steam and draining water. The mechanical trap has a small supercooling degree, is not affected by the change of working pressure and temperature, and immediately drains water, and there is no water in the heating equipment, which can make the heating equipment achieve the best heat exchange efficiency. The maximum back pressure rate is 80%, and the working quality is high. It is the most ideal trap for heating equipment in the production process.
Mechanical traps are free float, free semi-float, lever float and inverted bucket.
1, free floating trap:
The structure of the free-floating trap is very simple. There is only a stainless steel hollow float with a finely ground moving part, which is both a float and an opening and closing part. No wearing parts, long service life. "Yinqiu" brand steam trap is equipped with Y series automatic exhaust device, which is very sensitive, can automatically exhaust and has high working quality.
When the equipment starts to work, the air in the pipeline is exhausted through Y series automatic exhaust device, and the low-temperature condensed water enters the trap. The condensed water level rises, the float rises, the valve opens, the condensed water is discharged rapidly, the steam enters the equipment rapidly, the equipment heats up rapidly, the temperature-sensitive liquid of Y series automatic exhaust device expands, and the automatic exhaust device closes. The steam trap starts to work normally, and the floating ball rises and falls with the condensate level to block steam and drain water. The valve seat of the free float trap is always below the liquid level, forming a water seal, no steam leakage and good energy saving effect. The minimum working pressure is 0.0 1Mpa, and it is not affected by the fluctuation of temperature and working pressure within the range of 0.0 1Mpa to the maximum working pressure, and the drainage is continuous. Condensed water with saturation temperature can be discharged, the minimum supercooling degree is 0℃, and there is no water in the heating equipment, which can make the heating equipment achieve the best heat exchange efficiency. The back pressure rate is more than 85%, which is one of the most ideal traps for heating equipment in the production process.
2. Free semi-floating trap;
The free semi-floating ball catcher has only one semi-floating ball cylinder as a moving part, with the opening facing downwards. The ball cylinder is both an opening and closing part and a sealing part. The whole spherical surface can be sealed, with long service life, water hammer resistance, no wearing parts, no fault, durability and no steam leakage. When the back pressure rate is greater than 80%, the condensed water with saturation temperature can be discharged, and the minimum supercooling degree is 0℃. There is no water in the heating equipment, which can make the heating equipment achieve the best heat exchange efficiency.
When the device was just started, the air and low-temperature condensate in the pipeline entered the trap through the launch tube, and the bimetallic emptying element in the valve bounced off the ball cylinder, and the valve was opened, so that the air and low-temperature condensate were quickly discharged. When steam enters the ball barrel, the ball barrel generates upward buoyancy, at the same time, the temperature in the valve rises, the bimetallic emptying element contracts, the ball barrel floats to the valve port, and the valve closes. When the steam in the ball barrel becomes condensed water, the ball barrel loses its buoyancy and sinks, the valve opens and the condensed water is quickly discharged. When the steam enters the ball barrel again, the valve closes again and works continuously intermittently.
3. Lever float trap:
The basic characteristics of lever-type floating ball catcher are the same as those of free floating ball catcher. The internal structure is that the floating ball connecting lever drives the valve core to open and close the valve with the rise and fall of condensate level. Lever floating ball steam trap adopts double valve seats to increase condensate discharge, which can realize small volume and large displacement, and the maximum displacement can reach 100 ton/hour. It is the most ideal trap for large heating equipment.
4. Inverted bucket trap:
Inside the inverted bucket trap, the inverted bucket is a liquid level sensitive component, with the barrel opening downward, and the inverted bucket is connected with the lever to drive the valve core to open and close the valve. The invention can exhaust air, is not afraid of water hammer and has good anti-pollution performance. The undercooling is small, the steam leakage rate is less than 3%, the maximum back pressure rate is 75%, and there are many joints, so the sensitivity is not as good as that of the free floating ball trap. Because the inverted bucket trap closes the valve by the upward buoyancy of steam, it is not suitable 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, and the inverted bucket falls by its own weight. The connecting rod of the bucket drives the valve core to open the valve, and the air and low-temperature condensed water are quickly discharged. When the steam enters the bucket, the steam of the bucket generates upward buoyancy, and the bucket rises to connect the lever to drive the valve core to close the valve. There is a small hole in the inverted bucket. When a part of steam is discharged from the small hole, another part of steam produces condensed water, and the inverted bucket loses buoyancy and sinks down by its own weight. The connecting lever of the inverted bucket drives the valve core to open the valve and work intermittently.
5, combined superheated steam trap:
The combined superheated steam trap has two isolated valve cavities, and the upper and lower valve cavities are connected by two stainless steel pipes. It is a combination of floating ball trap and inverted bucket trap. The valve is advanced and reasonable in structure, which can timely discharge the condensed water formed when superheated steam disappears under the working conditions of overheating, high pressure and small load, effectively prevent the leakage of superheated steam, and has high working quality. The maximum allowable temperature is 600℃, the valve body is all stainless steel, the valve seat is hard alloy steel, and the service life is long. It is a special steam trap for superheated steam, which has won two national patents and filled the domestic blank.
When condensed water enters the lower valve cavity, the floating ball of the auxiliary valve rises with the liquid level, and the floating ball closes the steam inlet pipe hole. The condensed water rises to the main valve cavity through the water inlet conduit, and the inverted bucket falls by its own weight to drive the valve core to open the main valve and discharge the condensed water. When the condensate level in the auxiliary valve cavity drops, the floating ball 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, and the inverted bucket generates upward buoyancy to drive the valve core to close the main valve. When the condensate level in the auxiliary valve cavity rises again, the next cycle starts again and the drainage is interrupted.
Second, the thermal electrostatic trap
This kind 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 supercooling degree of the thermal static trap is relatively large, generally between 15 and 40 degrees. Some sensible heat in condensed water can be used, and there is always high-temperature condensed water in front of the valve, so there is no steam leakage and the energy-saving effect is remarkable. It is the most ideal trap for steam pipes, heat tracing pipes, small heating equipment, heating equipment and small heating equipment with low temperature requirements.
Thermostatic traps are diaphragm type, bellows type and bimetal type.
1, diaphragm trap:
The main function element of diaphragm trap is metal diaphragm, which contains liquid with vaporization temperature lower than water saturation temperature. There are two options: the valve opening temperature is lower than the saturation temperature 15℃ and 30℃. Diaphragm trap is particularly sensitive, not afraid of freezing, small in size, and resistant to overheating, and can be installed in any position. The back pressure rate is greater than 80%, and non-condensable gas can be discharged. The diaphragm box is firm, long in service life, convenient to maintain and wide in application range.
When the device was just started, low-temperature condensed water appeared in the pipeline, the liquid in the capsule was in a condensed state, and the valve was in the open position. When the temperature of condensed water rises gradually, the liquid in the diaphragm box begins to evaporate, and the pressure in the diaphragm box rises, and the diaphragm drives the valve core to move in the closing direction. Before the condensate reaches the saturation temperature, the trap begins to close. The diaphragm box controls the valve switch with the change of steam temperature, which plays the role of blocking steam and draining water.
2, bellows trap:
The stainless steel bellows in the bellows trap valve core is filled with liquid with vaporization temperature lower than water saturation temperature. The valve switch is controlled by the change of steam temperature. The valve is equipped with adjusting bolts, which can adjust the service temperature as required. The adjustment range of supercooling is generally lower than saturation temperature 15℃-40℃. The back pressure rate is over 70%, which is not afraid of freezing, small in size, can be installed in any position, will not discharge condensed gas, and has a long service life.
When the device is started, cooling condensate appears in the pipeline, the liquid in the bellows is in a condensed state, and the valve core is in an open position under the elastic force of the spring. When the temperature of condensed water rises gradually, the liquid filled in the bellows begins to evaporate and expand, the internal pressure increases, and the valve core deforms and stretches, driving the valve core to move in the closing direction. Before the condensate reaches the saturation temperature, the steam trap begins to close, and the valve switch is controlled with the change of steam temperature to block steam and drainage.
3, bimetallic trap:
The main component of bimetallic steam trap is bimetallic temperature sensing element, which is heated and deformed with the rise and fall of steam temperature to push the valve core to open and close the valve. Bimetal trap is equipped with adjusting bolts, which can adjust the use temperature as needed. The adjustment range of supercooling is generally lower than saturation temperature 15℃-30℃, and the back pressure rate is greater than 70%. It can discharge non-condensable gas, is not afraid of freezing, is small in size, can resist water hammer and high pressure, and can be installed in any position. Bimetal fatigue requires frequent adjustment.
When the device was just started, low-temperature condensed water appeared in the pipeline, the bimetal was flat, and the valve core was in the open position under the action of spring force. When the temperature of condensed water rises gradually, the bimetallic temperature sensing element begins to bend and deform, pushing the valve core to the closed position. Before the condensate reaches the saturation temperature, the trap begins to close. Bimetal controls the valve switch with the change of steam temperature to block steam and drain water.
Third, the trap of thermal power generation
This kind of trap is based on the principle of phase change, relying on the different thermodynamic principles of speed and volume changes when steam and condensate pass through, so that the valve plate produces different pressure differences from top to bottom, which drives the valve plate to open and close the valve. Because the working power of the thermal trap comes from steam, the steam waste is relatively large. Simple structure, water impact resistance, maximum retraction of 50%, loud noise, frequent valve operation and short service life.
Thermal power traps include thermal power (disc type), pulse type and perforated plate type.
1, thermal power trap:
There is a movable valve plate in the thermal trap, which is both a sensitive part and an action executive part. According to the different thermodynamic principles of speed and volume changes when steam and condensate pass through, different pressure differences are generated on the valve plate to drive the valve plate to open and close the valve. The steam leakage rate is 3%, and the supercooling degree is 8℃- 15℃.
When the device is started, cooling condensate appears in the pipeline, which is pushed away by the working pressure and quickly discharged. When the condensed water is discharged, the steam is also discharged. Because the volume and flow of steam are greater than that of condensed water, the valve plate will have a pressure difference between the upper and lower, and the valve plate will close quickly under the suction of steam flow. When the valve plate is closed, the valve plate is subjected to pressure from both sides, and the stress area under the valve plate is smaller than that above. Because the pressure in the steam chamber of the trap comes from the steam pressure, the upper valve plate is more stressed than the lower one, and the valve plate is tightly closed. When the steam in the steam trap room is cooled into condensed water, the pressure in the steam trap room disappears. The condensed water is pushed away by the working pressure, and the condensed water continues to be discharged, circulated and intermittently discharged.
2. Disc steam insulation trap:
The working principle of disc steam insulation trap is the same as that of thermal trap, which is to add a shell outside the steam chamber of thermal trap. The inner cavity of the shell is communicated with the steam pipeline, and the main steam chamber of the trap is insulated by the steam of the pipeline itself. Make it difficult to cool the temperature of the main steam chamber, keep the steam pressure, and close the steam trap tightly. When the pipeline produces condensed water, the shell of the trap cools and the trap begins to drain water; If there is no condensed water 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 cemented carbide. The maximum allowable temperature of this valve is 550℃, which is durable and has a long service life. It is a special trap for superheated steam with high pressure and high temperature.
3, pulse trap:
The pulse trap has two orifice plates, and the valve switch is adjusted according to the change of steam pressure drop. Even if the valve is completely closed, the inlet and outlet are connected through the first and second small holes, and they are always in an incomplete closed state, and steam keeps overflowing, resulting in a large amount of steam leakage. This kind of trap has high working frequency, serious wear and short service life. Small size, water resistance, can discharge air and water at saturated temperature, close to continuous drainage, and the maximum back pressure is 25%, so there are few users.
4, orifice trap:
Orifice trap is to select orifice plates with different diameters according to different displacement, so as to control the displacement. Simple structure, improper selection will lead to poor drainage or a large number of steam running, which is not suitable for steam equipment with intermittent production or steam equipment with large fluctuation of condensate water.
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