I. Memorize the translation of the word combinations.
feed-water heater, flue gases, heating medium, heat absorbed by water, to reduce the losses, series of tubes, present practice, all-steel unit, return bend, flange joint, economizer heating surface, opposite direction, great heat transfer, the gases discharge, gas side, single-pass construction, row of tubes, various factors, in some cases, boiler heating surface, straight run of tubing, gases leaving the boiler.
II. Answer these questions on the text
1. What is an economizer? 2. What is used as a heating medium in the economizer? 3. Where is the economizer interposed? 4. Does the economizer increase boiler efficiency? 5.What does the economizer consist of? 6. Can you say by what medium are the tubes of the economizer surrounded on the outside? 7. How are economizers classified according to their gas and water flow? 8. Speak about the difference between the parallel and counterflow economizers. 9. What does the counterflow in the economizer result in?
III. Translate into English
1. Экономайзер - это теплообменник, где питательная вода подогревается при помощи уходящих из котла газов.
2. Экономайзер представляет собой устройство, которое обогревается продуктами сгорания топлива.
3. Подобное устройство предназначено для подогрева либо для частичного испарения воды, которая поступает в паровой котёл.
4. Высокотемпературный перегретый пар позволяет повысить экономичность паровых машин и турбин, так как потребление ими пара снижается примерно на 1% с увеличением перегрева на 5° C.
UNIT 6
BOILER MOUNTINGS
Certain fittings are necessary on a boiler to ensure its safe operation. They are usually referred to as boiler mountings. The mountings usually found on a boiler are:
Safety valves. Safety valves are fitted in pairs, usually on a single valve chest. Each valve must be able to release all the steam the boiler can produce without the pressure rising by more than 10% over a set period.
Spring-loaded valves are always fitted on board ship because of their positive action at any inclination. They are positioned on the boiler drum in the steam space. The valve is held closed by the helical spring, whose pressure is set by the compression nut at the top. The spring pressure, once set, is fixed and sealed by a Surveyor. When the steam exceeds this pressure the valve is opened and the spring compressed. The escaping steam is then led through a waste pipe up the funnel and out to atmosphere.
Figure 6.1 – Safety valveThe compression of the spring by the initial valve opening results in more pressure being necessary to compress the spring and open the valve further. To some extent this is countered by a lip arrangement on the valve lid which gives a greater area for the steam to act on once the valve is open. A manually operated easing gear enables the valve to be opened in an emergency. Various refinements to the ordinary spring-loaded safety valve have been designed to give a higher lift to the valve.
Main steam stop valve. This valve is fitted in the main steam supply line and is usually of the non-return type. It regulates the flow of steam supply outside. The steam from the boiler first enters into an anti-priming pipe where most of the water particles associated with steam is removed.
Auxiliary steam stop valve. This is a smaller valve fitted in the auxiliary steam supply line, and is usually of the non-return type.
Feed check or control valve. A pair of valves are fitted: one is the main valve, the other the auxiliary or standby. They are non-return valves and must give an indication of their open and closed position. The high pressure feed water is supplied to the boiler through this valve. This valve opens towards the boiler only and feeds the water to the boiler. If the feed water pressure is less than the boiler steam pressure then this valve remains closed and prevents the back flow of steam through the valve. Feed check or control valve prevent backflow from the boiler through the feedwater line into the condensate/feedwater tank during the off cycle of the pump.
Water level gauge. Water level gauges or 'gauge glasses' are fitted in pairs, at opposite ends of the boiler. The construction of the level gauge depends upon the boiler pressure. This indicates the water level in the boiler, the water level in the boiler should not fall below a particular level otherwise the boiler will be overheated and the tubes may burn out.
Fusible Plug. If the water level in the boiler falls below a predetermined level, the boiler shell and tubes will be overheated. And if it is continued, the tubes may burn, as the water cover will be removed. It can he prevented by stopping the burning of fuel on the grate. When the temperature of the shell increases above a particular level, the fusible plug, which is mounted over the grate, melts and forms an opening. The high-pressure steam pushes the remaining water through this hole on the grate and the fire is extinguished.
Figure 6.2 - Fusible Plug
Pressure gauge connection. Where necessary on the boiler drum, superheater, etc., pressure gauges are fitted to provide pressure readings. Pressure gauge connection indicates the pressure of the steam in the boiler.
Air release cock. These are fitted in the headers, boiler drum, etc., to release air when filling the boiler or initially raising steam. An air cock is located in the uppermost steam space of a boiler. This design allows for air to enter and escape during filling and draining of the boiler. Before firing a cold boiler with no steam pressure, open the air cock to allow air to escape during the heating of the water. When steam begins to come out of the air cock piping, close the valve.
Sampling connection. A water outlet cock and cooling arrangement is provided for the sampling and analysis of feed water. A provision may also be made for injecting water treatment chemicals.
Blow down valve. This valve enables water to be blown down or emptied from the boiler. It may be used when partially or completely emptying the boiler. The blowdown valves on a boiler are used to remove scale and other foreign matter that have settled in the lowest part of the water spaces. Boilers are also blown down to control concentration of dissolved and suspended solids in boiler water. The water column blowdown permits removal of scale and sediments from the water column.
Scum valve. A shallow dish positioned at the normal water level is connected to the scum valve. This enables the blowing down or removal of scum and impurities from the water surface.
Whistle stop valve. This is a small bore non-return valve which supplies the whistle with steam straight from the boiler drum.
VOCABULARY
valve chest клапанная коробка
safety valve предохранительный клапан
helical spring спиральная пружина
compression nut стяжная гайка
main stop valve главный стопорный паровой клапан
auxiliary steam stop valve вспомогательный стопорный клапан.
non - return valve невозвратный клапан
water level indicator датчик уровня воды
drain valve дренажный клапан
salinometer valve солемерный клапан
chemical dosing valve дозировочный клапан
blow down valve клапан продувки котла
discharge tube сливная труба
evaporating tube испарительная (парогенерирующая) труба
scum valve 1) продувочный клапан 2) клапан верхнего продувания
whistle stop valve cтопорный клапан свистка
sampling connection aрматура для взятия проб
steam space паровое пространство
to refer to относиться, ссылаться, зд. называться
mountings гарнитура(котла)
to mount устанавливать
to fit устанавливать
main steam supply line главный паропровод
auxiliary steam supply line вспомогательный паропровод
feed check or control valve регулировочный клапан
water - level gauge водомерное стекло
air release cock воздуховыпускной кран
pressure gauge connections манометровые штуцера
fusible plug плавкий предохранитель
the back flow of steam обратное перетекание котловой воды
the off cycle of the pump отключение насоса по завершению рециркуляции теплоносителя
a predetermined level заданное значение регулируемой величины
the grate колоснико́вая решётка
EXERCISES
Exercise 1.Read these word combinations and remember their translation.
Boiler mountings, a single valve chest, spring-loaded valves, the steam space, the helical spring, the compression nut, the escaping steam, the initial valve opening, a lip arrangement, the valve lid, manually operated easing gear, the main steam supply line, an anti-priming pipe, the auxiliary steam supply line, the back flow of steam, the off cycle of the pump, a predetermined level, pressure readings, initially, partially or completely, foreign matter, dissolved and suspended solids, scale and sediments.