Application of Rotary Compensator in Medium Pressure Steam Pipeline

1 Project Overview

In a company 100 × 104t / a ethylene and ancillary projects, there are two medium-pressure steam pipelines that are transported from the thermal power project to the refining project. The specifications of the steam pipeline are D610 × 26, and seamless steel pipes for high-pressure boilers are used, and the material is 20G carbon steel. The total length is 2396m, the conveying capacity is 152 ～200t / h, the design pressure is 4.2MPa, the design temperature is 450 ℃, and it is laid overhead.

2 Selection of compensator

2.1 Square compensator

The square compensator is a commonly used method for steam pipelines, which has the advantage of high safety and no maintenance is required during normal operation, but it takes up a lot of space when the pipe diameter is large. The steam design temperature is as high as 450 ° C. If a square compensator is used, the compensation distance is short, resulting in large consumption of elbows and pipes and excessive pressure drop. The total length of the pipeline of this project is 2396m, and one square compensator is provided every 60m. A total of 40 square compensators are required. The outrigger of the square compensator is 11m long. Each compensator is calculated based on 4 elbows, for a total of 160 elbows. The length of the pipe extended by the outrigger is 880m. The calculation shows that the pressure drop of the pipeline using the square compensator is 0.367 MPa, which cannot meet the user's requirements.                 

2.2 Spherical compensator

The advantages of the spherical compensator are its strong compensation ability, small footprint, small resistance, and bending in any direction. If a spherical compensator is used, 12 sets of spherical compensators need to be installed according to the terrain and other conditions. The length of the outrigger of the spherical compensator is 7.5m and the calculated pressure drop is 0.25MPa. Considering the pressure drop alone, the use of a spherical compensator is a feasible solution. However, the spherical compensator has lateral displacement, is easy to leak, and has high operating and maintenance costs. There is a safety problem in performing leak compensation under high pressure. The processing technology of the spherical compensator suitable for this project is very complicated.

2.3 Rotation compensator

Rotary compensator is a new type of compensator developed in recent years. It is mainly composed of a rotating tube, a sealing gland, a sealing seat and a cone connection tube.

3 Design points

The bracket should be set reasonably for long-distance compensation; Because of the square swing of the square combination compensation, the bracket is not allowed to be set within a certain distance on both sides; The friction angle directly affects the service life of the sealing material. The larger the pipe diameter, the smaller the friction angle ; The length of the force couple arm should be controlled at 2-6m; the compensator should be pre-biased by 1/2 of the compensation amount; due to the long compensation distance, in order to reduce the thrust of the fixed bracket, a rolling bearing with a lower friction coefficient or other reduction socket.