UNIT VI. THE SUPERHEATER

The efficiency of the steam power plant is influenced by the steam conditions, i.e. pressure and temperature. That is why the superheater is an essential part of the modern marine boiler.

Steam is superheated by being heated above the temperature of saturation. Superheaters may be divided into several types:

- the convection type installed in one of the gas passages of the boiler;

- the radiant type installed in the boiler furnace;

- the multi-loop type placed remote from the furnace in the lower part of the uptake.

The convection type superheater usually consists of two headers into which seamless steel tubes are rolled. The tubes are connected to the steam inlet header and to the superheater outlet header. Steam from the boiler circulates through these tubes. Superheater tubes range from 1 to 2 in. in diameter; the temperature rarely exceeds 550°C, as the tensile strength of most metals decreases rapidly after passing 350°C.

With increased evaporation rates and higher superheat temperatures, many modern boilers use multi-loop type superheaters. These superheaters consist of a number of multi-loop tube elements. The steam enters all the tubes together, but makes several passes across the gas stream through each element.

The boiler drums are designed for a certain maximum operating pressure. When the steam pressure gets above the safe minimum, the safety valve should open and steam discharged. So all superheaters must have one or more safety valves.

Vocabulary

superheater, n пароперегреватель

efficiency, n производительность; КПД

steam conditions параметры пара

saturation, n насыщение

convection type superheater конвективный тип пароперегревателя

radiant type superheater радиационный тип пароперегревателя

multi-loop type superheater змеевиковый тип пароперегревателя

remote отдельно

uptake, n дымоход

seamless, adj бесшовный

roll, v вальцевать; прокатывать

inlet header входной коллектор

outlet header выходной (выпускной) коллектор

range, v колебаться в пределах

inch (in.), n дюйм

exceed, v превышать

tensile strength предел прочности

decrease, v уменьшать

evaporation rate скорость или интенсивность испарения;

паропроизводительность

gas stream поток газа

E X E R C I S E S

1. Give English equivalents:

Паросиловая установка, влиять, давление, выше температуры, устанавливать, размещать, соединять с, редко, быстро, использовать, поступать в, рабочее давление, слегка перегретый пар, вспомогательные механизмы, установка/агрегат, при необходимости, потребность в паре, существовать, в случае продувки котла.

2. Complete the statements. Choose the proper word from the list: