Three precision valve brief analysis of the working principle of the trap

The steam trap plays a role in blocking the steam and water in the steam heating system. Selecting a suitable trap can make the steam heating equipment achieve the highest working efficiency. In order to achieve the best results, we must fully understand the performance and characteristics of various types of traps.

There are many varieties of steam traps, each with different performance. When using steam traps, first select their characteristics to meet the optimal operation of steam heating equipment, and then consider other objective conditions, so that the trap you need is correct and effective.

Traps must be able to "recognize" steam and condensate before they act as a barrier to steam. The "identification" of steam and condensate is based on three principles: density difference, temperature difference and phase change. Then three types of traps were manufactured based on three principles: classified as mechanical, thermostatic, and thermodynamic.

A mechanical trap

The mechanical type is also called float type. It uses the density difference between condensate and steam. By changing the liquid level of condensate, the float lifts the valve flap to open or close to achieve the purpose of blocking the steam discharge. Mechanical type traps have a low degree of undercooling and are not affected by changes in working pressure and temperature. There is water and rows, and there is no water in the heating equipment, which can make the heating equipment achieve the best heat exchange efficiency. With a maximum back pressure of 80% and high work quality, it is the ideal trap for heating equipment in the production process.

Mechanical traps have free float, free half float, lever float, inverted bucket, etc.:

1. Free float trap:

The structure of the free float trap is simple. There is only one stainless steel hollow float ball finely grounded by moving parts. It is both a float and an open and close part. It has no wearing parts and has a long service life. The inside of the YQ brand trap has Y series automatic air exhaust device is very sensitive, it can automatically discharge air and has high working quality.

When the equipment is started, the air in the pipeline is discharged through the Y series automatic air discharge device. The low temperature condensate enters the trap. The level of the condensate rises, the float rises, the valve opens, the condensate drains quickly, and the steam quickly enters. Equipment, equipment quickly warms up, the Y-Series automatic air evacuation device's temperature-sensitive liquid expands, and the automatic air-discharge device closes. The trap starts working normally and the float floats up and down with the condensate level, blocking the steam. The seat of the free float trap is always below the liquid level, forming a water seal, no steam leakage, and good energy saving effect. Minimum operating pressure 0.01Mpa, from 0.01Mpa to the maximum use pressure within the scope of the temperature and working pressure fluctuations, continuous drainage. Saturated temperature condensate can be discharged, the minimum degree of undercooling is 0°C, 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 half-float traps:

Free half-float traps only have one half-ball type bucket as the moving part, with the opening facing downwards, the bucket is the opening and closing part and the seal. The entire sphere can be sealed, has a long service life, is resistant to water hammer, has no wearing parts, is trouble-free, durable, and has no steam leaks. The back pressure rate is greater than 80%, can condense condensation temperature, the minimum degree of undercooling is 0°C, there is no water in the heating equipment, which can make the heating equipment achieve the best heat exchange efficiency.

When the device is just starting up, the air and low-temperature condensate in the pipeline enter the trap through the launch tube. The bimetal evacuation element in the valve opens the bowl, the valve opens, and the air and low-temperature condensate drain quickly. When the steam enters the barrel, the barrel generates upward buoyancy and the temperature in the valve rises. The bimetal evacuation component contracts, the ball rake floats toward the valve port, and the valve closes. When the steam in the barrel becomes condensed water, the barrel loses buoyancy and sinks, the valve opens, and the condensate drains quickly. When the steam reenters the barrel, the valve closes again, intermittently and continuously.

3. Float ball trap:

The basic characteristics of the lever float ball trap are the same as that of the free float ball. The internal structure is a floating ball connecting the lever to drive the valve core, and the valve is opened and closed with the liquid level of the condensate. Lever float ball trap utilizes double valve seats to increase the condensate discharge capacity, can achieve large volume and small displacement, and the maximum water repellent capacity reaches 100 tons/hour. It is the ideal trap for large heating equipment.

4. Inverted bucket trap:

The inside of the inverted bucket steam trap is an inverted bucket as a liquid level sensitive part, the bucket opening is downwards, and the invert bucket connects the lever to drive the valve core to open and close the valve. Inverted bucket traps can discharge air, are not afraid of water hammer, and have good dirt resistance. The degree of undercooling is small, the steam leakage rate is less than 3%, the maximum back pressure rate is 75%, and there are many connectors. The sensitivity is not as good as the free float trap. Because the inverted bucket steam trap closes the valve by buoyancy and the working pressure is less than 0.1 MPA, it is not suitable for use.

When the device is just started, the air and low-temperature condensate in the pipeline enter the trap. The inverted bucket leans on its own weight. The inverted bucket connects the lever and drives the valve core to open the valve. The air and low-temperature condensate drain quickly. When the steam enters the inverted bucket, the steam of the inverted bucket generates upward buoyancy, and the inverted bucket rises to connect the lever to drive the valve core to close the valve. A small hole is opened in the bucket. When some steam is discharged from the hole, the other part of the steam produces condensate. The bucket loses its buoyancy and sinks by its own weight. The bucket is connected to the lever to drive the valve to open the valve. Work, intermittent drainage.

5. Combined superheated steam trap:

The combined superheated steam trap has two isolated valve cavities. Two stainless steel pipes connect the upper and lower valve cavities. It is a combination of floating ball and inverted bucket traps. The valve structure is advanced and reasonable, in overheating, high pressure, Under the small load working condition, the condensed water formed when the superheated steam disappears can be promptly discharged, effectively preventing the leakage of the superheated steam, and the work quality is high. The maximum allowable temperature is 600 °C, the valve body is all stainless steel, the valve seat is a hard alloy steel, long service life, is a special steam trap for superheated steam, obtained two national patents, to fill the gap in the country.

When the condensate enters the lower valve chamber, the float of the secondary valve rises with the liquid level, and the float ball closes into the steam tube hole. Condensate rises into the main valve chamber through the inlet pipe, and the bucket is lowered by its own weight, which drives the valve core to open the main valve and discharges the condensate. When the condensate level of the sub-valve chamber drops, the float drops with the liquid level and the secondary valve opens. The steam enters into the inverted bucket in the upper main valve cavity from the steam inlet pipe, and the inverted bucket generates an upward buoyancy force, and the inverted bucket drives the valve core to close the main valve. When the condensate level in the sub-valve chamber rises again, the next cycle starts again, intermittently draining.

Two. Thermostatic steam trap

This type of steam trap uses the temperature difference between steam and condensate to cause the deformation or expansion of the temperature sensing element to actuate the valve core opening and closing valve. Thermostatic steam traps have a relatively high degree of undercooling, typically 15 degrees to 40 degrees, and they can use some of the sensible heat in the condensate. High-temperature condensate is always present in front of the valve. No steam leaks, and the energy saving effect is significant. . It is the ideal trap for steam pipes, heat tracing lines, small heating equipment, heating equipment, and small heating equipment with low temperature requirements.

Thermostatic traps are bellows, bellows, bimetal
1. Membrane type traps:

The main action element of the membrane trap type trap is a metal bellows, which is filled with a liquid whose vaporization temperature is lower than the saturation temperature of water, and whose opening temperature is lower than the saturation temperature of 15°C and 30°C. Membrane traps are extremely responsive, not afraid of freezing, small in size, resistant to overheating, and can be installed in any position. The back pressure rate is more than 80%, it can discharge non-condensing gas, the membrane box is strong, the service life is long, the maintenance is convenient, and the use range is very wide.

When the device is started, low-temperature condensate water appears in the pipeline, the liquid in the membrane box is in a condensation state, and the valve is in the open position. As the temperature of the condensate rises, the membrane begins to evaporate, the pressure in the membrane rises, and the membrane drives the valve to move in the closed direction. The trap begins to close before the condensate reaches the saturation temperature. The membrane box controls the valve switch with the steam temperature change, and plays the role of blocking steam and water drainage.

2. Bellows type traps:

Bellows-type steam trap valve core Stainless steel bellows is filled with a liquid with a vaporization temperature below the water saturation temperature. With the steam temperature control valve switch, the valve is equipped with adjustment bolts, according to the need to adjust the temperature, the general subcooling adjustment range is lower than the saturation temperature of 15 °C -40 °C. The back pressure rate is greater than 70%, is not afraid of freezing, and has a small volume. It can be installed in any position, can discharge non-condensing gas, and has a long service life.

When the device is started, the cooling condensation occurs in the pipeline, the liquid in the bellows is in a condensed state, and the valve core is in the open position under the spring 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 expands, and the valve moves in the direction of closing. Before the condensate reaches saturation temperature, the steam trap starts to close, and the steam valve is controlled to change with the steam temperature. Valve switch, stop steam.

3. Bimetal trap type:

The main component of the bimetal trap is the bimetal temperature sensing element, which is heated and deformed as the temperature of the steam rises and falls, pushing the valve core to open and close the valve. Bi-metal steam traps are equipped with adjusting bolts, which can be used to adjust the operating temperature. Generally, the degree of subcooling adjustment is lower than the saturation temperature of 15°C-30°C, and the back pressure rate is greater than 70%. It can discharge noncondensing gases and is not afraid of freezing. Small size, able to resist water hammer, high pressure resistance, can be installed in any position. Bimetals are fatigued and need to be adjusted frequently.

When the device has just started, low-temperature condensate water emerges from the pipeline, the bimetal is flat, and the valve core is under the spring force and the valve is in the open position. As the temperature of the condensate rises gradually, the bimetal temperature-sensing element begins to bend and deform and pushes the valve core toward the closed position. The trap begins to close before the condensate reaches saturation temperature. The bimetallic strip controls the valve opening and closing as the temperature of the steam changes to block steam.

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