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2. What is the difference between a watertube and a firetube boiler?
3. What do I need to know before purchasing a boiler?
4. What is the boiler's fireside and what is the boiler's waterside?
1.What is a rental boiler?
A rental boiler is a packaged boiler either installed inside a container to create a portable boiler room or mounted on a trailer to create a trailer-mounted boiler.
Rental boilers are easily transportable by road, rail or air.
Rental boilers have easy connections for steam/hot water, city water, electric, etc., making for speedy hookups.
You can rent a boiler for a variety of reasons and terms are often flexible.
2.What is the difference between a watertube boiler and a firetube boiler?
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Firetube |
Watertube |
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Description |
A steam boiler in which hot gaseous products of combustion pass through tubes surrounded by boiler water. The water and steam in fire-tube boilers are contained within a large-diameter drum or shell, and such units often are referred to as shell-type boilers. Heat from the products of combustion is transferred to the boiler water by tubes or flues of relatively small diameter through which the hot gases flow. The tubes are connected to tube sheets at each end of the cylindrical shell and serve as structural reinforcements to support the flat tube sheets against the force of the internal water and steam pressure. Braces or tension rods also are used in those areas of the tube sheets not penetrated by the tubes. Fire-tube boiler may be designed for vertical, inclined, or horizontal positions. |
A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Water tube boilers are used for high-pressure boilers. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes. In smaller boilers, additional generating tubes are separate in the furnace, while larger utility boilers rely on the water-filled tubes that make up the walls of the furnace to generate steam. The heated water then rises into the steam drum. Here, saturated steam is drawn off the top of the drum. In some services, the steam will reenter the furnace through a superheater to become superheated. Superheated steam is used to drive turbines. Since water droplets can severely damage turbine blades, steam is superheated to 730 °F (388 °C) or higher to ensure that there is no water entrained in the steam. |
Advantages |
Relatively inexpensive |
Almost unlimited capacities to several million pounds per hour of steam. |
Disadvantages |
Typically not suitable for high pressure applications above 250 PSIG |
High initial cost |
3. What do I need to know about purchasing a new boiler?
What is your desired service? Low pressure or High Pressure steam, saturated or unsaturated, domestic or heating hot water?
What is your process load? What are your storage (on demand) requirements?
How critical is your operation? Do you have a backup?
Your primary and auxiliary fuels: boilers can burn many types of fuels including #2 Oil (Diesel), #4/#6 oil, natural gas, propane, yellow grease, tallow, etc.
What type of combustion air system is required? Forced draft systems are more efficient and also more expensive than atmospheric burners. Local jurasidictions, emission regulation and space restrictions must be considered. Is additional support required for stack height requirements? boilers can typically self support stacks from 4’ to 12’. What is your budget? A reconditioned boiler may offer a better purchasing alternative and comparable performance to a brand new boiler.
4. What is the boiler's fireside and what is the boiler's waterside?
The fireside of a boiler refers to any area that is exposed to direct heat. On a firetube, this is the furnace, inner door(s), refractory and inside the tubes. On a watertube, this is the furnace, refractory, and outside of the tubes.
The waterside of a boiler refers to any area that is exposed to water or steam. On a firetube, this is the inner shell, outer furnace and the outside of the tubes. On a watertube, this is the steam and mud drums and the inside of the tubes.
Boilers are constructed with hand-holes and manways for access to these areas for inspection purposes.
5. What are the elements of combustion?
Initial combustion requires 3 elements – Fuel, Heat and Oxygen. Air is comprised of approximately 21% oxygen, 78% nitrogen and 1% miscellaneous gases and therefore a large amount of combustion air is required to achieve a proper mix. The fuel must contain sufficient BTU content and must be oil must be either air, steam or mechanically atomized to burn properly.
To maintain combustion, there are 3 requirements 1. Time for combustion to take place, 2. Proper temperature, generated by the combustion process and 3. Turbulence: proper mixing of air and fuel.