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Elbow (long)

key word:Heat exchange element


Product description

Elbow (long)

 

1. Introduction

1.1. Purpose

Elbow pipe is mainly used for turning of pipes in thermal power station, nuclear power station, petrochemical, metallurgy, shipbuilding, machinery, construction and other industries. Elbow pipe is divided into two series of inner diameter and outer diameter.

1.2. Model meaning

For the outer diameter pipe, the expression of elbow is as follows:

OD-**×##-R@@-&&-$$

**--------Outer diameter (mm)

##---------------Wall thickness (mm) or wall thickness serial number

@@--------------------Bending radius (mm)

&&-----------------------Bending angle (°)

$$-----------Steel grade

For the inner diameter pipe, the bending method is as follows:

ID -**×##-R@@-&&-$$

**--------Outer diameter (mm)

##---------------Wall thickness (mm) or wall thickness serial number

@@--------------------Bending radius (mm)

&&-----------------------Bending angle (°)

$$-----------Steel grade

1.3. Structural features

1.3.1. Structural form. Elbow pipe is divided into two series of inner diameter and outer diameter.

1.3.2. Structure description. The working principle of the medium frequency induction heating elbow is to use the medium frequency power supply to heat the narrow band in the circumferential direction of the pipe to the required temperature of the elbow. At the same time, the steel pipe is pushed forward at a uniform speed, and the bending moment acts on the heating area of the pipe to make the pipe bend along the preset track, so as to form the elbow with a certain curvature radius and angle. The working principle of cold bending is to drag the tube along the mould to form a bend with fixed curvature radius and angle without heating the tube. Cold bending is generally used for pipes with outer diameter less than 273mm. One of the four pipe bends in the power plant adopts medium frequency induction heating.

1.3.3. Important characteristics:

1.3.3.1. Bending pipe can obviously reduce the vibration of pipeline.

1.3.3.2. The erosion of the inner wall of the outer arc of the elbow by the medium flowing in the elbow is smaller than that of the elbow.

1.3.3.3. Bending pipe can reduce the total number of welded joints.

1.3.3.4. The welded joint of elbow is far away from the bending part, which is safer.

1.3.3.5. The local resistance of the elbow is small, which can reduce the total resistance of the pipeline.

1.3.3.6. The stress increase factor of elbow is small.

 

2. Main technical parameters and product appearance

2.1. Main technical parameters (see table 77-1)

Table 77-1 main technical parameters of elbow

No. Item Data
1 Design temperature T () Determination of parameters
2 Design pressure p [MPa(g)] Determination of parameters
3 Interface specification (mm): IDXT or ODXT Determination of parameters
4 Steel grade Determination of parameters
5 Bending radius R(mm) Determination of parameters
6 Bending angel θ(°) Determination of parameters
7 Straight length L1 (mm) Determination of parameters
8 Straight length L2 (mm) Determination of parameters
9 Min. wall thickness (mm) Determination of parameters

2.2. Product appearance (see figure 77-1)

 

3. Selection method

3.1. Performance parameters (see table 77-2)

Table 77-2 elbow performance parameters

Bending radius R(mm) Flow area Bending angel Straight section dimensions
2.5OD; generally more than 3OD, easy to bend and adjust Inner diameter pipe: 100% 100°any angle If the length of a single pipe is allowed, it is better to have one pipe diameter and the minimum is 150 mm
Cold section outer diameter pipe: 97% ~ 100%
Outside diameter of water supply pipe: 93%

 

3.1.1. According to the layout, the bending radius should be selected reasonably. Large bending radius is not conducive to layout; small bending radius is not conducive to processing and economic operation, but also increases the investment cost.

3.1.2. The wall thickness of the elbow should be selected according to the bending radius, and the influence of the manufacturer's bending process, the ratio of outer diameter to wall thickness and the steel grade on the wall thickness reduction should be considered.

3.1.3. Determine bending angle and straight section length according to material warehouse and design drawing.

3.2 supply requirements

3.2.1. Provide material quality certificate of pipes.

3.2.2. Provide main technical parameters.

 

4. Range of supply

4.1. The finished elbow meets the requirements of DL/T 515-2004 power station elbow, and is attached with quality inspection certificate.

4.2. For alloy copper elbow, the metallographic structure and hardness report after heat treatment shall be provided.