Trap principle and structure

Steam trap plays the role of steam resistance and drainage in the steam heating system. The steam heating equipment can reach the highest working efficiency by selecting the right steam trap.In order to achieve the most ideal effect, it is necessary to have a comprehensive understanding of the working performance and characteristics of various types of steam traps.

There are many varieties of steam traps, each with different performance.When selecting a steam trap, you should first select its characteristics to meet the best operation of steam heating equipment, and then consider other objective conditions, so as to select the steam trap you need is correct and effective.

Steam trap to be able to "identify" steam and condensate, in order to play the role of steam drainage.Steam and condensate are "identified" on three principles: density difference, temperature difference and phase change.Therefore, three types of steam traps are manufactured according to three principles: mechanical, thermostatic and thermodynamic.

Mechanical type steam trap

Mechanical type is also known as float type, is the use of condensate water and steam density difference, through the change of condensate level, float lifting drive valve disc open or close, to achieve the purpose of steam resistance drainage.The mechanical steam trap has a small degree of supercooling, which is not affected by the working pressure and temperature change. Water is discharged when there is water, and there is no water stored in the heating equipment, which can make the heating equipment achieve the best heat exchange efficiency.Maximum back pressure rate of 80%, high quality, is the production of the most ideal steam trap heating equipment.

Mechanical type trap has free float ball type, free half float ball type, lever float ball type, inverted bucket type and so on:

1, free floating ball trap

The structure of free-floating ball type trap is simple, there is only one stainless steel hollow float ball with fine grinding of moving parts inside, it is both float and open and close parts, no vulnerable parts, long service life, "HG" trap with Y series automatic air exhaust device inside, very sensitive, can automatically exhaust air, high quality of work.

Equipment has just started work, air in the pipe after Y series automatic air discharge device, low temperature water into the steam trap, water level rise, the float rises, the valve opens and the condensate discharge rapidly, steam quickly into equipment, equipment rapidly, Y series automatic air discharge device of liquid thermal expansion, automatic air discharge equipment shut down.The steam trap starts to work normally, the float ball rises and falls with the condensate level, and the steam is blocked and drained.The valve seat of free-floating ball type trap is always below the liquid level, forming water seal, no steam leakage, good energy saving effect.The minimum working pressure is 0.01Mpa, and the range from 0.01Mpa to the maximum working pressure is not affected by the fluctuation of temperature and working pressure, and continuous drainage is required.Can condensate saturation temperature, minimum degree of supercooling of 0 ℃, no water in the heating equipment, can make the heating equipment to achieve optimum thermal efficiency.The back pressure ratio is more than 85%, which is one of the most ideal traps for heating equipment in production process.

2, free semi-floating ball trap

Free half float ball trap only one half float ball ball bucket for moving parts, opening down, the ball bucket is open and close parts, is a seal.The whole sphere can be sealed, long service life, water resistant hammer, no wearing parts, no failure, durable, no steam leakage.Back pressure is greater than 80%, can the condensate saturation temperature, minimum degree of supercooling of 0 ℃, no water in the heating equipment, can make the heating equipment to achieve optimum thermal efficiency.

When the device is just started, the air and low-temperature condensate in the pipeline pass through the launching pipe and enter the trap. The bimetallic strip emptying element in the valve sprays the ball bucket open, and the valve opens and the air and low-temperature condensate are discharged rapidly.When the steam enters the ball barrel, the ball barrel produces upward buoyancy, at the same time the temperature inside the valve rises, the bimetallic strip empties the element to contract, the ball barrel floats to the valve mouth, the valve closes.When the steam in the ball barrel turns into condensate, the ball barrel loses buoyancy and sinks. The valve opens and the condensate is quickly discharged.When the steam reenters the ball barrel, the valve closes again, discontinuously and continuously.

3, rod float ball trap

The basic characteristics of the lever-float type steam trap are the same as that of the free-float type. The internal structure is that the float is connected with the lever to drive the valve core, and the valve is switched on and off with the rise and fall of the liquid level of the condensate.The lever floating ball type steam trap increases the condensate displacement by the double valve seat, may achieve the volume small displacement big, the biggest steam trap reaches 100 tons/hour, is the large-scale heating equipment most ideal steam trap.

4, inverted bucket trap

Inside the inverted bucket trap is an inverted bucket for level sensitive parts, the bucket opening down, inverted bucket connected with a lever to drive the valve heart open and close the valve.Inverted bucket trap can discharge air, not afraid of water hammer, anti - fouling performance is good.The subcooling degree is small, the vapor leakage rate is less than 3%, the maximum back pressure rate is 75%, the connection is more, the sensitivity is not as free floating ball trap.Because inverted bucket trap is steam upward force to close the valve, the working pressure difference is less than 0.1mpa, not suitable for selection.

When the device is just started, the air and low-temperature condensate in the pipeline will enter the trap, the inverted bucket will fall by its own weight, the inverted bucket will connect with the lever to drive the valve core to open the valve, and the air and low-temperature condensate will be discharged quickly.When the steam enters the inverted bucket, the steam of the inverted bucket will generate upward buoyancy, and the rising lever of the inverted bucket will drive the valve core to close the valve.There is a small hole in the inverted bucket, when some steam is discharged from the small hole, another part of the steam produces condensate water, the inverted bucket loses buoyancy and sinks by its own weight, the inverted bucket is connected with a lever to drive the valve core to open the valve, circulation work, intermittent drainage.

5, combined superheat steam trap

Combined superheated steam trap has two isolation valve cavity, two stainless steel tubes connected by upper and lower valve chamber, it is by the ball float and a combination of inverted bucket type steam trap, the valve structure of advanced and reasonable, in the heat, high pressure and small load working conditions, to be able to timely discharge superheat disappear when the formation of the condensate, effectively prevent leakage of superheated steam, high quality of work.Maximum allowable temperature is 600 ℃, the body as a whole stainless steel, the seat for hard alloy steel, long service life, is a special superheated steam trap, obtained two national patents, fill the domestic blank.

When the condensate enters the lower valve chamber, the float ball of the auxiliary valve rises with the liquid level, and the float ball closes the steam inlet pipe hole.The condensate rises to the main valve chamber through the inlet pipe, the inverted bucket falls by self-weight, drives the valve core to open the main valve, and discharges the condensate.When the condensate level of the auxiliary valve chamber drops, the float drops with the level and the auxiliary valve opens.The steam enters into the inverted bucket in the upper main valve chamber from the intake pipe. The inverted bucket generates upward buoyancy, and the inverted bucket drives the valve core to close the main valve.When the condensate level of the auxiliary valve chamber rises again, the next cycle starts again, discontinuously draining water.

Two, thermal static trap

This kind of steam trap is the use of steam and condensate water temperature difference caused by the variation of temperature sensing elements or expansion driven valve heart valve door.Thermal-static steam trap has a high degree of supercooling, generally ranging from 15 degrees to 40 degrees. It can make use of a part of the condensate water to show heat. There is always high temperature condensate water in front of the valve, without steam leakage and with remarkable energy saving effect.Is in the steam pipeline, heat tracing pipeline, small heating equipment, heating equipment, temperature requirements of small heating equipment, the ideal trap.

Thermal-static steam trap has bellows type, bellows type, bimetallic sheet type.

1, bellows type trap

Bellows trap is the main action of element metal film box, filled with a kind of gasification temperature is lower than the water saturation temperature of liquid, have open valve temperature below the saturation temperature 15 ℃ and 30 ℃ two to choose from.The response of the bellows type trap is particularly sensitive, it is not afraid of freezing, small size and can be installed at any position.The back pressure ratio is more than 80%, can exhaust the non-condensing gas, the membrane box is strong, the service life is long, the maintenance is convenient, the use scope is very wide.

When the device is just started, cold condensed water appears in the pipeline, the liquid in the capsule is in the state of condensation, and the valve is in the open position.When the condensate temperature gradually increases, the liquid inside the membrane begins to evaporate and the pressure inside the membrane rises. The diaphragm drives the valve to move toward the closing direction. Before the condensate reaches the saturation temperature, the trap starts to close.Diaphragm box with the change of steam temperature control valve switch, play a role in steam resistance and drainage.

2, bellows type trap

Bellows type trap spool stainless steel bellows filled with a vaporization temperature below the water saturation temperature of the liquid.Change with steam temperature control switch valve, the valve is equipped with adjusting bolt, can be used according to need to adjust the temperature, the average degree of supercooling adjusting range below the saturation temperature 15 ℃ to 40 ℃.The back pressure ratio is more than 70%, it is not afraid of freezing, small volume, can be installed at any position, can exhaust non-condensing gas, long service life.

When the device is started, the cooling condensate appears in the pipeline, the liquid in the bellows is in the state of condensation, and the valve core is in the open position under the elastic force of the spring.When the condensate temperature gradually increases, the liquid filled in the bellows begins to evaporate and expand, the internal pressure increases, the deformation and elongation drive the valve heart to move toward the closed direction. Before the condensate reaches the saturation temperature, the steam trap starts to close, and the valve switch is controlled with the change of steam temperature to prevent steam drainage.

3, bimetal plate trap

The main parts of the bimetallic steam trap are bimetallic temperature sensing elements, with the steam temperature rise and fall by thermal deformation, to push the valve heart switch valve.Bimetal plate equipped with adjusting bolt, trap can be used according to need to adjust the temperature, the average degree of supercooling adjusting range below the saturation temperature 15 ℃ ~ 30 ℃, back pressure is greater than 70%, can not condensate gas, not afraid of cold, small size, resistant to water hammer, resistance to high pressure, can be installed at any position.Bimetallic strip has fatigue and needs constant adjustment.

When the device is just started, cold condensed water appears in the pipe, the bimetallic sheet is flat, the valve heart is under the spring force, and the valve is in the open position.As the temperature of the condensate rises, the bimetallic element begins to bend and deform, pushing the valve core toward the closed position.The trap begins to close before the condensate reaches its saturation temperature.Bimetallic sheet with steam temperature change control valve switch, steam resistance drainage.

Thermodynamic steam trap

This kind of steam trap according to the phase change principle, depending on the steam and condensate water through the flow rate and volume change of the different thermodynamic principle, so that the valve disc up and down to produce different pressure difference, driving the valve disc valve switch.Because the thermal power type steam trap work power from the steam, so the steam wave is relatively large.Simple structure, resistant to water hammer, 50% maximum back, noise, valve plate work frequently, short service life.

Thermodynamic type trap thermodynamic (disc), pulse type, hole plate type.

1. Thermodynamic steam trap

Thermally powered steam trap has a movable disc, which is both a sensitive part and an actuator.According to the different thermodynamic principles of the flow rate and volume change when steam and condensed water pass through, different pressure difference is generated between the upper and lower parts of the valve disc, and the valve disc is driven to open and close the valve.Steam leakage rate is 3%, super-cooling degree is 8 ℃ ~ 15 ℃.

When the device is started, cooling condensate appears in the pipeline, and the condensate pushes the valve plate away by working pressure and rapidly discharges.When the condensate discharge is completed, the steam is then discharged. Because the steam is larger than the condensate volume and flow rate, the pressure difference between the upper and lower parts of the valve disc is generated, and the valve disc is quickly closed under the suction of steam flow rate.When the valve plate is closed, the pressure on both sides of the valve plate, the bearing area under the valve plate is less than the bearing area above, because the pressure inside the steam trap steam chamber comes from the steam pressure, so the pressure above the valve plate is greater than the below, the valve plate tightly closed.When the steam in the trap chamber cools to condensate, the pressure in the chamber disappears.Condensate by working pressure to open the valve, condensate and continue to discharge, circulation work, intermittent drainage.

2. Disk-type steam insulated steam trap

The working principle of the disc steam insulated steam trap is the same as that of the thermodynamic steam trap.The inner chamber of the shell is communicated with the steam pipe, and the steam of the pipe is used to keep the main steam chamber of the steam trap warm.Make the temperature of main steam chamber not easy to cool down, keep steam pressure, steam trap close tightly.When condensate is produced in the pipeline, the trap shell cools down and the trap begins to drain water;If there is no condensate in the superheated steam pipeline, the trap will not open and the work quality is high.For alloy steel body, valve core for carbide, the valve is the highest temperature is 550 ℃, durable, long service life, is a high pressure, high temperature of superheated steam trap.

3, pulse trap

Pulse type steam 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 communicated through the first and second holes, and the valve is always in the state of incomplete closing. The steam is constantly escaping and the steam leakage is large.The steam trap has high operating frequency, severe wear and short service life.Small size, resistant to water hammer, able to discharge air and saturated water temperature, close to continuous drainage, maximum back pressure 25%, so few users.

4, hole plate trap

The purpose of orifice trap is to select orifice with different orifice sizes to control the displacement according to different displacement.The structure is simple, the choice is not suitable will appear the drainage is not equal to or the massive run off steam, will not be suitable for the intermittent production to use the steam equipment or the condensate water volume fluctuation big to use the steam equipment.