Marine boilers information

Marine Boilers

By

Lars Josefsson. Important marine boilers information for technicians and engineers using marine boilers and HFO burners, water-tube steam boiler or fire-tube steam boiler, HFO or coal fired furnaces

Know-how is the keystone of all marine boilers operations; pioneer Scotch marine boilers as well as modern water-tube marine boilers, and exhaust gas economizers; they all require skilled engineers to operate them.

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Steamesteem means that I like steam boilers, old fashion Scotch marine boilers as well as top modern water tube marine boilers.
Marine boilers alarm and trip functions The most important alarm and trip functions on steam boilers.
Marine boiler control automatic An easy way to find out if your steam boiler control system lights up the first burner safely.
Marine boiler Control The very best way to get redundancy in a steam boiler plant would be to have two completely independent one boiler control systems.
Marine boiler Safety Steam boiler plants require adequate control systems to raise steam, maintain design conditions for steady steaming, secure the boiler units and detect promptly malfunctions and failures.
Fail-safe, Marine boiler control Fail-safe; any predictable failure must result in a safe situation.
Marine Boilers Steam and Water Steam flow diagram for an exhaust gas boiler and two oil-fired auxiliary marine boilers.
Marine Boilers Heavy Fuel Oil Fuel Oil flow diagram for two oil-fired auxiliary marine steam boilers
Marine boilers water level control Sophisticated methods are required for a steam boiler with high steam production and relatively small water volume.
Two marine boiler operations Keeping a slave steam boiler pressurized in a two boiler system.
Marine boilers HFO firing How to burn marine bunker oil.
Marine boilers Smoke Density Meter A plant that never shows traces of smoke at the funnel is not burning the fuel efficiently.
Waste oil firing in marine boilers Is the sludge a waste oil just to get rid of or is it a valuable fuel?
Heat transfer media: steam, oil and water A comparison between the heat transfer media

Marine Steam Boiler Accessories

Steam sootblowing A steam soot blower consists of a number of nozzles on a pipe that rotate and sometimes moves axially between the banks of tubes.
Water soot washing A water washing devise is normally a number of water nozzles placed over the tubes and the water washes the tubs and the sooty water is then collected in a pit below.
Infrasonic soot cleaning Infrasonic sound from a special loudspeaker make the soot vibrates off the tubes.
Steal balls soot cleaning Small steel balls falling from the top of the boiler, bouncing from one tube to the next one.
Rapping soot cleaning By rapping the fouled convection heating surfaces the tubes are caused to vibrate so that the deposited combustion residues fall off. It is designed to be used during boiler operation.
Combustion air preheater While the utilization of the waste heat in the chimney gases for preheating the combustion air supplied to the boiler furnace, by means of air heaters, has long had a wide use in steamships, as, for example, in the Howden air heter.
Boilers Superheaters Superheaters are essentially a bank of tubes, in the exhaust gas duct after the boiler, used to heat the steam above the saturation temperature.
Boiler accessories

Marine Boiler Constructions

A Scotch marine steam boiler consists of a steam drum and one to four fire-tubes in which furnaces heats the steam boiler. A water-tube Marine boiler is a steam generator consisting of a steam drum and water-drums and tubes which are exposed to the heat of a furnace and arranged so as to promote rapid water circulation in the steam boiler. At high pressure, providing a more positive means of maintaining the circulation becomes desirable and advantageous. The Controlled Circulation Boiler design is an ideal arrangement for steamships in the high pressure range. With its features of positive circulation, compactness, light weight, suitability for high pressure and temperature, and adaptability to limited space conditions, Boilers with Controlled Circulation can offer important advantages for advanced steamships design.

Marine boilers level sensors

Advanced methods to measure and control the water level in a marine boiler. Using one level method for controlling the marine boiler level and another for the level alarms and boiler trip-functions would be quite wise. Differential pressure transmitter is a common method for measuring the level in a marine boiler.
Marine boiler level differential pressure This boiler level measuring method uses a differential pressure measuring system with "wet leg", that is, the impulse pipes to the positive measuring point below the lowest water level and the impulse pipe to the negative measuring point above the highest water level, are both filled with water
Marine boiler level capacitance electrode An insulated electrode is placed in the boiler and the length should be sufficient to reach the water at all acceptable levels. The insulated electrode and the boiler work as a capacitor with the water and the steam as a variable dielectric medium
Marine boiler level conductivity electrode It's normally one boiler level electrode for emergency low water level alarm, or two electrodes if also high level alarm is required. This water level sensing method is also common on small boilers for start and stop of the feedwater pumps
Marine boiler level float Boiler level float switches have been used for decades as level switches in boilers, but nowadays electrodes have replaced them
Marine boiler level displacer A boiler level displacer (a float heavier than the water) is suspended to a spring balance by means of a stainless steel cable or a rod
Marine boilers level sensors

Marine boilers feedwater

The marine boiler feadwater system is very important for the steam production. The steam boiler feedwater quality is essential to protect the marine boiler from harm.
Oil in marine boilers feedwater Beware of oil in the boilers feedwater system
Boiler blowdown Optimizing Bottom-Blowdown from marine Boilers
Marine boilers feedwater heating The first and most important use for the exhaust steam is to heat the feedwater, since all of the heat of the exhaust steam so utilized is returned undiminished to the boilers
Marine boilers feedwater treatment The presence of impurities in boiler feedwater is a constant source of concern to the operating personnel, because it affects not only the efficiency of the boiler, but also its safety
Marine boiler scale The mineral and organic substances present in natural water supplies vary greatly in their relative proportions, but are principally comprised under the carbonates, sulphates and chlorides of lime, magnesia and sodium, iron and aluminum salts, silicates, mineral and organic acids, and the gases oxygen and carbon dioxide.
Corrosion within Marine boilers The boiler corrosion process is essentially an oxidationl reduction reaction. It may occur in various forms including the special form known as caustic cracking. The most usual forms, however, are pittings and general wastage
Marine boiler water treatment The importance of the correct method of applying treatment chemicals cannot be over-stressed. Additions of hydrazine to the feedwater must be continuous and sufficient quantity to remove the last traces of oxygen from the feedwater and to leave a small excess
Marine boiler water test Because of the inherent difficulties involved in any attempt at automatic control of feedwater treatment, it is necessary that the exact condition of the boiler water be known from day to day, in order that necessary treatment can be applied for the correction of any unsatisfactory conditions which may exist
Boiling out a marine boiler Boiling out before the boiler is placed in service to remove any foreign products
Care of idle marine boilers Several methods are available for storing idle boilers to prevent corrosion. The choice will depend on whether or not long term storage is required or if, for short time storage, the boiler need to be available at short notice
Marine boilers feedwater

Atomizers for marine boiler HFO burners

Marine boilers today are mainly HFO fired. Different methods are used to atomize the fuel before the combustion in the steam bolers furnaces.
Fuel Oil Atomizing Some methods are suitable for heavy fuel oil, and others are better to be used with diesel oil
Fuel pressure jet atomizer The pressure jet atomizer utilizes the supply pressure energy to atomize the fuel into a spray of finely dispersed droplets
Intenal mix steam atomizer The burner lance consists of two concentric tubes, a one-piece nozzle and a sealing nut. The media supplies are arranged so that the steam is supplied down the centre tube and the fuel oil through the outer tube
External mix steam atomizer The steam-assisted pressure jet burners atomizer is designed to make full use of pressure jet atomization at high outputs and full use of blast atomization at low outputs
Rotary cup atomizer The fuel oil flows at low pressure into the conical spinning cup where it distributes uniformly on the inner surface and throws off the cup rim as a very fine oil film
Low pressure air atomizer The principle is similar to that of the rotary-cup-atomizer, but the fuel is forced to rotate in a fixed cup by means of a forcefully rotating primary airflow
Blue flame burner atomizer In the blue flame burner some of the hot gases from the flame are recirculated back to the inlet where they mix with and heat the combustion air
Atomizers for marine boiler HFO burners

Propgrams for units-conversions and fuel-oil calculations

UNITS-Conversion Program Accuracy is an important concern with measuring units-conversion. The units in this program are, as far as practical, derived directly from the Basic Conversion Factors and calculated with a precision of twenty significant figures.
FUEL OIL Calculation Program The basic idea with The FUEL OIL Calculation Program is that anyone should be able to easily get the most important informations about their fuel oil.
Units-conversions and fuel-oil calculations

Tables

Steam tables

Steamships

Steamships

Links to marine boiler suppliers

On these pages I have put together some links that I think might be useful for marine engineers in their work
Marine boiler Accessories Products that enhance your ability to obtain maximum marine steam boiler performance.
Boilermakers marine boilermaker and industry boilermakers.
Marine boiler Control system Field repairing services for various marine boiler control systems.
Boiler feedwater treatment Proper feedwater treatment is of the utmost importance in marine boiler operations.
Burner Manufacturers Manufacturer of oil and gas burners for homes, industry and ships.
Literature and Education Diploma In Ship Management and Marine Surveying.
Machinery and Services Propulsion diesel engines based upon the highly advanced technology.
Steamships owners Steamboats used for pressure

Marine Boilers Development

In tracing the history of the marine boilers development and application of marine boilers, it's interesting that some of the basic requirements have always applied, although from time to time the emphasis has shifted from one requirement to another. In the beginning, space and weight limitations were not considered to be as important as other factors, and yet at later stages the emphasis on those items brought about the development of new types of marine boilers. Generally, it has been the economic or military need for increased propulsion power that has instigated significant advances in marine boiler design. The earliest types of steam boilers were relatively large pressure vessels, with furnaces located underneath them, but it soon became apparent that such exterior furnaces were far from satisfactory, and they were then located inside the marine boilers shell. The marine boiler exterior had now developed into an approximate cube, Fraser marine boiler, and no matter how heavily stayed, its flat exterior placed very low limits on the steam pressure that could be carried and also left much to be desired from a maintenance and safety standpoint. The internal furnaces and tubes, however, were cylindrical and entirely satisfactory for the demands of their time. By 1870, marine boiler steam pressures had reached only 4 bar; by 1900 the marine boiler steam pressure had increased to about 20 bar.

Scotch fire-tube marine boilers with one to four furnaces

To overcome the steam boiler's structural weaknesses and at the same time reduce cost of fabrication, the marine boiler shell was made cylindrical with provision to install one or more combustion chambers, fire-tubes, between the two flat sides of the boiler shell. Known as the Scotch marine boilers, this boilers as finally developed, met with wide and enthusiastic approval by marine engineers. Although minor changes have been made throughout the years, the boiler's design has remained much the same and its qualities of ruggedness, reliability, ease of maintenance, and ability to stand abuse made it -- until recently -- the most popular boilers in the marine boiler field. Even though the Scotch marine boilers proved to be popular and well suited for steamships, the fact that its steam pressure was limited to 20 bar retarded the progress.

The single-ended return tube Scotch boiler consists of a cylindrical boiler shell of large diameter and short length, provided with two or more furnaces i.e. corrugated fire-tubes. Each furnace ends in a combustion chamber, surrounded by water. The gases pass through a bank of flue-tubes from the combustion chamber to the smoke-box at the boiler front.
A Scotch marine boiler contained large quantity of water, about six times more than a water-tube boiler, and was therefore slow to steam up and to change the output steam capacity. Due to the Scotch boiler's stiff construction it required also a long steaming up period to avoid leaks caused by thermal expansion of the material.

Water tube marine boilers

There was a realization that advanced steam boiler designs with greater steam generating capacity, higher pressure, and increased efficiency were needed to meet the changing requirements brought about by the development of turbine propulsion machinery. Stiff commercial competition among merchant fleets as well as various naval powers made these developments most urgent. Marine engineers began to adapt various types of water tube boilers to fit into the restricted space available for installations aboard steamships, Some adaptations proved highly advantageous with respect to heat transfer and weight, and offered a variety of designs suitable for steam pressures in excess of the maximum of fire-tube boiler types. Thus, new possibilities were presented for the utilization of steam aboard steamships. Even though the water-tube boiler almost has replaced the fire-tube boiler, Old steamships with Scotch marine boilers are still sailing in salt-water as well as lake-water, managed by enthusiastic marine boiler engineers. These boilers are often new build from the original marine boiler drawings.
A Yarrow boiler consist of an upper steam drum connected by banks of inclined water-tubes to two lower water drums
All the water-tubes discharge below the water level in the steam drum. The outer water-tubes function as down comer and the inner tubs function as evaporating tubes. This causes violent circulation of the water in the boiler and separate downcomers are not needed. To maintain such a circulation, the water level in the steam drum must always be kept well over the external tube-ends.
The furnace is placed between the lower drums and the flue gases flows between the tubes on both sides of the boiler steam drum. Yarrow boilers were widely used in the navy of many countries. Later Yarrow boilers had bended tubes to improve the elasticity of the boiler construction.

V2M9 marine boiler

By locating the marine boilers fixed points of support at approximately midheight of the boiler, expansion of the lower portion of the boiler is downward and expansion of the upper portion of the boiler is upward. This arrangement results in reduced amplitudes of the boiler expansion as compared to those which would occur if the boiler was supported at the bottom. In order to avoid problems of tube vibration in the boiler's convection generating bank, Combustion Engineering's designers placed a limitation on the dimensions between steam and water drums. Many of the higher powered ships have experienced severe vibration problems and it is essential that the boiler components must be designed to avoid natural frequencies which are within the range of low frequency excitations.

Boilers with Controlled Circulation

At high boiler pressure, providing a more positive means of maintaining the circulation becomes desirable and advantageous.
The Controlled Circulation Boiler design is an ideal arrangement for boilers in the high pressure range. With its features of positive circulation, compactness, light weight, suitability for high steam pressure and temperature, and adaptability to limited space conditions, Steam Boilers with Controlled Circulation can offer important advantages for advanced steamships boiler design.

Design principles for the construction of furnaces for marine boilers

A number of factors determine the configuration of a marine boiler furnace. First of all, the type of steam boiler under consideration sets some of the furnace dimensions; fire room space limitations, service requirements, and burner arrangement also influence the furnace layout. The furnace arrangement must also conform to criteria which are prerequisites for proper thermal and circulation performance. The amount of waterwall surface determines the furnace exit-gas temperature that is most significant in the design of the steam boiler's superheater. Practical requirements must also be considered; for instance, the firing equipment must be located where it can be easily operated.

© Steamesteem in a computerized world.
Steamesteem means that I like marine boilers, Yarrow water-tube marine boilers as well as Scotch marine boilers.

My name is Lars Josefsson. I am from Sweden and I have worked with marine boilers and heavy fuel oil burners almost all my life. During the years I have designed automatic control systems for more than one hundred boilers for ships that are sailing on the seven seas today in tankers, cruise liner, general cargo ships, etc
By Lars Josefsson

Mailing address:
Mr. Lars Josefsson
Prästslättsvägen 18
374 40 Karlshamn
Sweden
E-mail: josefsson@steamesteem.com