BOILER 3CL LUNARIO 3CL MACARUBBO 3CL SAGAYO 3CL LUMIGUEN 3CL MIRADOR What is a boiler? Boilers use fuel to heat water or steam and circulate the hot water through pipes. The hot water produced is then used to heat a building and/or produce hot water for personal or industrial use. For example a boiler used as a heating system in a home would have radiators in a house or part of a building. The boiler heats the water for use and also circulates that hot water through the pipes and the radiator, heating the rooms. A boiler uses circulated hot water whereas a furnace, found in many homes today, uses forced air and circulates it through vents. Types of boilers include steam turbine, package boilers, steam generators, clean steam packages, hot water heaters, hot oil heaters, boilers and vaporizers. A package boiler is a boiler that is ordered with all necessary parts included, assembled and ready to use. Very little installation is required. Steam boilers are used to produce steam for industrial usage such as cleaning. Boilers vary in size and shape. A boiler used for a residence is going to be small enough to fit in the corner of a room, where are industrial boilers can be large enough to fill up an entire room. Depending on the amount of heat it needs to generate and what exactly it will be used for. Refurbishing a boiler If you now have a boiler and are considering replacing it you have a few options. Boilers have a general life of 30-40 years. If there are parts on your boiler that are not working you may consider getting it refurbished, buying a used boiler that has been refurbished already, or getting new parts. When a boiler is replaced it's often sent out to be remanufactured. The boiler is disassembled, cleaned, refurbished and then sent back out to operation or put on the market. The parts of the boiler are inspected and cleaned. If a part is no longer working and it is irreparable, it will be discarded, only parts that are safe and in working order are refurbished. It is common for brand new parts to be used with refurbished parts or systems. A boiler that has been refurbished can come out of the shop looking like new and work just as well as a new one, and for a much lower cost. Other benefits If the decision has been made to purchase a brand new boiler, consider sending your used boiler to get refurbished so that someone else can use it. Boilers can almost always be refurbished and recycled, if not for the whole boiler can usually be disassembled for parts. There may be a non-profit organization or church in your area that is in need of a boiler but cannot afford to purchase a new one. Having a used boiler available to purchase or given as a donation, would be a huge help to any organization. The benefits of used boilers extend beyond that. Buying used boilers benefits the environment by helping to keep used appliances and materials out of landfills and it creates jobs at recycling and remanufacturing plants. INTRODUCTION The D-type boiler has been installed in U.S. Navy ships since 1950. Whether 600 psi or 1200 psi, D-type boiler construction is basically the same with a few exceptions, such as number of fuel oil burners and overall size and volume. REFERENCES (a) Boilers NSTM Chapter 221 (b) Fireman NAVEDTRA 10520 Series (c) Boiler Technician 3&2 NAVEDTRA 10535B (d) Principles of Naval Engineering 10788 H (e) Boiler Operation and Maintenance Manual NAVSEA 0951-LP-022-6010 INFORMATION A. Main propulsion boilers provide steam to the main propulsion turbines and auxiliary services in order to supply all shipboard steam systems in accordance with demand. (refer to Figure 1). It is designated as a D-type boiler because of the relative positions of the drums and side header which form the letter D. All D-type boilers are designated as uncontrolled superheat boilers because all the steam generated by the boiler must pass through the superheater. Superheater outlet temperature is a result of the combustion gas flow in proportion to the total amount of steam flow through all ranges (0 - 120%). The design characteristics ensure that the temperature will stabilize at set point. The degree of superheat is calculated by subtracting steam drum temperature from the actual reading on the superheater outlet temperature gage. In this lesson we will examine the components of the boiler and then we will bring everything together by describing how water and steam is generated and circulated through the boiler. The flow path of combustion gases through the boiler will also be discussed. D TYPE BOILER B. The economizer is a multi-pass heat exchanger located above the main generating bank at the base of the exhaust stack, so that combustion gas will give up a lot of its remaining heat to the incoming feedwater before passing out the stack (Refer to Figure 2) The incoming feedwater absorbs about 100°-200°F sensible heat from the exhaust gases. Fins are installed on the economizer tubes to increase the heating surface area further, helping to increase efficiency. ECONOMIZER C. The steam drum is located at the top of the boiler to provide an upper reservoir for the water covering the generating tube bank. Water is distributed from the steam drum to the lower drums and headers by pipes called downcomers. Generated steam is also collected and is separated from the water in the steam drum. Boilers are also equipped with safety valves to relieve excessive pressure. The valves are located on the steam drum and superheater outlet. They are designed to relieve sufficient pressure to safely steam the boiler at 120% with boiler steam stop valves closed (refer to Figure 3). These valves are discussed in detail in lesson 62B-206. D. Air vents or air cocks are installed on top of the steam drum to expel air from inside the steam drum during cold boiler light-off or when filling the boiler. The air vents or air cocks are shut when the boiler starts generating steam. SAFETY VALVE CONFIGURATION E. The internal fittings in the steam drum help distribute the water evenly throughout the drum, separate the generated steam from the water and remove moisture from the steam before it leaves the boiler (refer to Figure 4). 1. Lower baffle plates or apron plates Separate the incoming feedwater and generated steam and direct the steam to the separators. 2. Primary separators (cyclone separators) Separate most of the water from the steam by giving it a cyclone or rotary motion so that the water particles are expelled from the steam by the centrifugal forces. These separators are vertically mounted in the steam drum so that the steam rises out the top and the water falls back into the steam drum. 3. Secondary separators (chevron dryers) Remove additional moisture from the steam by changing the direction of steam flow several times. The steam passes on but the moisture cannot make the direction change with the steam. These separators are mounted above the primary separators and direct steam to the dry box which collects the steam at the top of the steam drum, directing it to the steam outlet piping to the superheater. 4. Feedwater leaves the economizer and enters the boiler through the internal feed pipe and becomes "boiler water." Perforations along the side of the feed pipe allow water to be distributed evenly throughout the steam drum (refer to Figure 4) STEAM DRUM INTERNALS 5. Since suspended solids may accumulate on the surface of the water in the steam drum, there must be means of removing them. The surface blow pipe is used to remove these light suspended solids from the surface of the water and to reduce the total dissolved solid content of the boiler water. Suspended solids usually consist of oil, salt contaminants, or excessive treatment chemicals which can cause foaming on the water surface. Dissolved solids usually consist of salt contaminants and treatment chemicals that are in solution. F. The D-type boiler uses the principle of accelerated natural circulation to circulate water through the boiler. To enable this principle to work, relatively cool water will naturally circulate through large diameter pipes to distribution points low in the boiler. The downcomers are these large diameter pipes connecting the steam drum with the water drum and lower headers to ensure proper circulation by delivering water from the steam drum to the water drum and lower headers. The downcomers are located between the inner and outer air casing to protect them from the direct radiant heat of the furnace. G. The water drum is located at the bottom of the boiler below the main generating bank and acts as a lower reservoir of water for distribution to the main generating bank. Also, this large drum serves as a collection point for solids (sludge) that precipitate to the bottom that are removed by bottom blowdown. H. The sidewall header is located along the furnace sidewall connecting sidewall tubes from the furnace floor to the steam drum. It distributes water to the sidewall tubes and provides another blowdown point for sludge removal. The sidewall tubes are two inch tubes which protect the boiler sidewall refractory from the direct heat of combustion and generate a small amount of steam. I. The lower rearwall header is located along the furnace rearwall from the furnace floor to the steam drum or upper header to provide a lower junction for rearwall tubes.