What Is a Steam Trap?

The function of steam traps (referred to as steam traps) is to automatically exclude non-condensable gases such as steam condensed water and air from heating equipment or steam pipes, and not to leak steam. Because the steam trap has the function of blocking steam and draining water, it can make the steam heating equipment evenly supply heat and make full use of the latent heat of steam to prevent water hammer in the steam pipeline.

The basic function of the steam trap is to discharge the air and cold non-condensable gas and steam from the steam system as soon as possible after use; at the same time automatically prevent steam leakage. There are many types of traps, each with different performance. Select

1. The rolling valve mechanism (new SCCV switching method) is adopted, which has excellent sealing and durability.

2. Balanced double valve seat design, which is smaller in volume and larger in displacement than ordinary traps, and has a large displacement field and can play a superior role.

3. Built-in bimetallic air automatic discharge valve can prevent air blockage and steam lock.

4. The unique U-shaped bi-metal ventilation port can greatly shorten the startup time of the equipment.

5. All parts are installed on the valve cover, the valve can be maintained and maintained without removing the pipe, which is simple and convenient. The imitation of many domestic trap manufacturers has further improved the production technology.

There are many domestic manufacturers producing traps, and most of the connection sizes are not uniform. It is mainly divided into the following major categories: General categories based on JB / T2203-1999 "Structure Length of Traps". Most domestic trap manufacturers are designed and manufactured according to this standard. For example, the maximum nominal diameter of the trap is DN500, and the maximum nominal diameter of the float trap is DN600. According to the trap specifications and the information available, the maximum nominal diameter of the trap is DN500.

1. Minimal loss.

2. Long life and reliable performance.

3. Can discharge air.

4. Can discharge carbon dioxide gas.

5. Corrosion resistance.

6, can work under back pressure, high pressure return water.

7, can prevent dirt blocking.

8.Water traps

Basic classification	Principle of action	Classification	Small classification
Mechanical	Vapor and condensation density difference	Float	Lever Float
		Free Float
		Free Float Pilot Piston
		Open up float	Floating bucket
		Differential pressure double-valve floating bucket
		Open-bottom float	Inverted bucket
		Differential pressure double valve bucket type
Thermostatic	Temperature difference between steam and condensate	Steam pressure difference	Bellows
		Bimetal sheet	Circular plate bimetal
Thermodynamic	Thermodynamic properties of steam and condensate	Disc	Atmospheric cooling disc
		Air insulation disc
		Steam heating condensate cooling disc
		Orifice	Pulsed

To exclude the same amount of condensate under a certain pressure difference, different types of traps can be used. All kinds of traps have certain technical performance and the most suitable working range. To choose according to the conditions of use, we cannot simply choose from the perspective of maximum drainage, and we should not choose the water valve based on the diameter of the condensate pipe. Generally, when selecting, first select the most suitable form of vegetable and water valve according to the use conditions and the technical performance of various traps according to the installation position. Select the specifications and quantity of the trap.

When the condensate load fluctuates to less than 15% of the rated maximum displacement, a hole-wrench trap should not be used, because under low load, some fresh steam leakage loss will be caused.

In the case that the condensed water must be removed immediately after the formation, it is not suitable to use a perforated trap, and a thermostatic bellows trap cannot be used, because both require a certain degree of subcooling (about 1.7 ~ 5.6 ° C) ).

As the condensate cannot be drained out immediately by the orifice trap and thermostatic trap, they cannot be used in steam turbines, steam pumps, or steam mains with manifolds. Even if the turbine casing is hydrophobic, it is not an option. In the above cases, a float-type steam trap is used. If necessary, a thermodynamic steam trap can also be used.

The thermodynamic trap has a performance close to continuous drainage, and its application range is large, and generally it can be used. However, the maximum allowable back pressure shall not exceed 50% of the inlet pressure, and the minimum working pressure shall not be less than 0.05 MPa. Floating ball traps should be used in quiet places.

For indoor steam heating equipment or pipes operating intermittently, an inverted bucket trap can be selected because of its good exhaust performance.

Mechanical traps should not be used for traps installed outdoors. If necessary, anti-freezing measures (such as shutdown and venting, thermal insulation, etc.) should be provided.

Although the installation positions of the traps are different, they can be divided into three types according to the flow direction of the condensate and the direction of the traps, as shown in the following figure: Any type of traps can be used as shown in Figure (a); Figure (b) ) The floating bucket type cannot be selected, but a bimetallic trap can be selected; the formation of condensate shown in Figure (c) is basically the same as the elevation of the trap position, and a floating bucket, thermodynamic or bimetallic trap can be selected. Valve ^[1]

1. Determine the pressure difference between the inlet and outlet of the steam trap according to the actual operating conditions. The inlet pressure of the steam trap refers to the lowest working pressure at the inlet of the steam trap due to the fluctuation of the steam pressure or the throttling of the temperature regulating valve; the outlet pressure of the steam trap refers to the highest working back pressure that can be formed after the steam trap When discharged into the atmosphere, the actual pressure difference is determined by the steam trap inlet pressure. This type of valve should generally be installed horizontally in the pipeline.

2. According to the amount of condensate generated by the steam heating equipment during normal operation, multiply by the selection correction factor k, and then select according to the drainage capacity of the steam trap.

3. The amount of condensate can be calculated by the following methods:

(1) The amount of condensate produced during pipeline operation Q = q0L (1-Z /%) (kg / h), in this formula:

Q: amount of condensed water (kg / h)

q0: amount of condensed water produced by light pipe (kg / h)

L: distance between hydrophobic points (m)

Z: thermal insulation efficiency (%)

(2) The amount of condensed water generated when the steam heating equipment is operating Q = VrC T / Ht, in this formula:

Q: amount of condensed water (kg / h)

V: volume of heated object (m3)

r: density of heated object (kg / m3)

C: Specific heat of liquid (kcal / kg.OC)

T: liquid temperature rise (OC)

H: Latent heat of steam (kcal / kg)

t: heating time

4. The structure and principle of various types of steam traps are different, and the performance fluids are different. When selecting, you can choose different steam traps according to different applications.

1.Principle

The principle of the mechanical steam trap is driven by the change of the condensate level.

The principle of a thermostatic steam trap is driven by changes in condensation temperature.

The principle of a thermodynamic steam trap is driven by the dynamic characteristics of condensate.

2.Main control parameters

The main technical parameters of steam traps include nominal size, nominal pressure, working pressure difference, working temperature, back pressure, and condensate water discharge.

Function

Quickly remove condensate generated; prevent steam leakage; remove air and other non-condensable gases. It can prevent water hammer, reduce the use efficiency of steam equipment, prevent corrosion of the inside of steam using equipment, and prevent damage to steam using equipment.

4, the main classification

According to the driving method of the opening and closing parts, it is divided into mechanical type, thermostatic type and thermodynamic type.

Mechanical type can be divided into floating ball type, floating bucket type, inverted bucket type and so on.

Thermostatic type can be divided into bimetal sheet type, bellows type, liquid expansion type, capsule type, diaphragm type and so on.

Thermodynamic type can be divided into disc type, pulse type, orifice plate type and so on.

5, select

1) The structure and principle of various types of steam traps are not the same. The types of steam traps should be distinguished. The pressure difference between the inlet and outlet of the steam trap should be determined according to the actual operating conditions, and the steam heating equipment may be generated during normal work. The amount of condensed water is multiplied by the selection correction factor K, and then selected according to the drainage capacity of the steam trap.

2) In the condensate recovery system, if the working back pressure is used to recover the condensate, a steam trap with a higher back pressure rate (such as a mechanical steam trap) should be selected; when the steam equipment is used, it is not allowed to accumulate condensate. In the condensate recovery system, steam equipment should not only saturate condensate, but also require non-condensable gas to be discharged in time. , Should use a steam trap capable of draining saturated water in parallel with the exhaust device or a steam trap with both functions of drainage and exhaust (such as a thermostatic steam trap); when working with steam equipment When the pressure fluctuates frequently, a steam trap that does not need to adjust the working pressure should be selected.

3) The nominal pressure and working temperature of the steam trap should be greater than or equal to the maximum working pressure and working temperature of the steam pipeline and steam equipment.

4). When the drainage capacity of one steam trap cannot meet the requirements, several steam traps can be installed in parallel.

5) Bypass pipe and valve can be set for easy maintenance.

6, construction, installation points

1) Clean the pipeline equipment before installation to remove impurities to avoid blockage.

2) The steam trap must be installed below the lowest point of the steam-using equipment and in a place that is easy to drain and easy to maintain. It should be arranged as concentratedly as possible for easy management and the connection should be firm and tight.

3) When installing, pay attention to the direction of the arrow on the valve body and the flow direction of the medium in the pipeline.

4) For a steam trap without a filter, a filter should be installed in front of the valve, and its flow area should not be less than 1.5 times the area of the channel, and the filter should be set in a position that is easy to disassemble.

5) Where freezing may occur, anti-freezing measures should be taken.

6) After the steam trap is installed, a hydrostatic test is required. The test pressure is the same as the test pressure of the pipeline system.

7) For installation practice requirements, please refer to the National Architectural Design Standards Atlas 05R407 "Selection and Installation of Steam Condensate Recovery and Drainage Devices" and manufacturer samples.

7, implementation standards

1) Product standards

"Terms, signs and structure length of steam traps" GB / T 12250-2005

Steam Trap Test Method GB / T 12251-2005

"Condensate recovery for steam heating systems and technical management requirements for steam traps" GB / T 12712-1991

"Steam Trap Valve Quality Classification" JB / T 53169-1994

Technical Conditions of Steam Traps JB / T 9093-1999

"General requirements for steel valves" GB / T 12224-2005

2) Engineering standards

"Code for Construction Quality Acceptance of Building Water Supply and Drainage and Heating Engineering" GB 50242-2002

"Code for Acceptance of Construction Quality of Ventilation and Air Conditioning Engineering" (GB50243-20023), related standard drawing 05R407

"Selection and Installation of Steam Condensate Recovery and Drainage Device" ^[1]