Industrial Steam Boiler Manifold Headers With Longitudinal Welded Pipe ASME Standard

Header Brief Description

In order to improve the boiler efficiency, boilers are gradually developed into tubular boilers to increase heat transfer area. The pot water flows from the pot barrel to the lower box through the downward tube, and is distributed to each tube bundle by the box body. The water in these tube bundles continuously absorbs heat energy and collects into the upper box body and then flows back into the pot barrel. We call the upper and lower box body headers. Header is an important part of the boiler, which is divided into upper header and lower header.

The main function is to collet working fluids or redistribute working fluids to other pipelines through headers. That is, to collect, mix and distribute working fluids, so as to ensure the working fluids are evenly distributed and heated. Lower header, also called coke-proof box, is located on both sides of the grate and directly contacts with the burning coal seam. Its function is to cool the coking slag without bonding with the side wall.

Types

According to its location, there are upper header and lower header or inlet header and outlet header. According to the types of bundles collected, they can be divided into water wall headers, super-heater headers, economizer headers and so on.

Functions

Header is a pipe fittings for mixing working substances of boilers and ensuring uniform heating of working substances. Usually the furnace wall of industrial boilers is composed of rows of tubes(water-cooled walls), but the size of boilers is huge, and the structure is complex. It can not guarantee that the working substances in all tubes absorb the same heat. There are many differences in heat absorption in different parts. Installing headers can let the working substance in each tube converge here, and distribute to the next level of each pipe so as to reduce the thermal deviation so that the heat absorption, flow of the working fluid and cooling and thermal efficiency of the boiler are optimized and improved; in addition, the size, number and layout of the pipes in the upper, middle and lower parts of the boiler are different. The header is responsible for connecting each section to ensure smooth flow of working substances.

Manufacturing process of headers

Structure and material

In all types or grades of boilers, the header structure is basically similar, mostly consisting of barrel, end cap, big and small pipe joints, tees, elbows, accessories( pre-welded parts or lifting ears) and other parts. The typical structure of header is shown in Figure 1.

The diameter range of header barrel in power station boilers is generally from 89mm to 914mm, the wall thickness range is from 7mm to 150mm, and the max. Length is 23000mm. The header is made of carbon steel(such as 20G, SA-106B, SA-106C), low alloy heat-resistant steel(such as 15CrMoG, 12Cr1MoVG, WB36, SA-335P12, SA335-P22), medium alloy heat-resistant steel(such as SA-335P91), and ultra-super critical boilers use SA-334P122, SA-335P92, etc. Commonly used equipment in header manufacturing includes groove machine, drilling machine, boring machine, automatic submerges arc welding machine for annular seam, CO2 gas shield welding machine, pipe bender, hydraulic press, heat treatment furnace and plunger hydraulic pump, etc..

Classification