A boiler is an element of a larger system (see Water-Steam-Condensate Cycle section) and as such, its proper operation depends on several secondary components, normally referred to as auxiliary equipment. Key boiler auxiliary equipment includes the following:
A. Boiler Feedwater Pump
Selecting a multi-pass, centrifugal pump with high efficiency stainless steel interiors is recommended for boilers from 30 HP on. For smaller boilers, a turbine pump can be used.
There exist a number of options in the pump market (including Goulds eSV model and Grundfos CR model) that comply with the requirements discussed above and that can be repaired without having to be disassembled. Furthermore, by keeping spare parts kits on hand you avoid having to have a second, stand-by pump installed.
B. Condensate Tank or Atmospheric Deaerator:
The condensate tank should have sufficient water storage capacity to feed a boiler for 20 minutes. (If two or three boilers share the same condensate tank, the same principle should be applied, multiplying by the number of boilers in operation simultaneously with the same tank.)
If the tank will operate efficiently, with a high rate of condensate return, it makes sense to order a larger capacity condensate tank (between 20-25% bigger) from the beginning of the project as this will permit the storage of large amounts of condensates in a short amount of time. (Increasing the size of a condensate tank still at the factory is easy and economical; however increasing the size of a tank already in operation is both difficult and costly.)
If your process does not factor in a percentage (even if it is small) of condensate return, it will be necessary to install a steam preheating system, which at the same time will operate as an atmospheric deaerator, eliminating 99% of the oxygen from the boiler feedwater.
The height of the condensate tank is a function of the height required by the feedwater pump so that cavitation does not occur.
C. Steam Header:
When the system has two or more boilers, it is convenient to install a steam header. The steam header is a large tube with cap lids where the steam from two or more boilers is collected and then distributed via separate outlets to the different processes. It is necessary to use steam valves in a steam header.
The header must have an upper connection for the pressure gauge and two lower connections – one for drain and the other for a filter and a condensate trap.
D. Water Softener:
A water softener is a fundamental piece of auxiliary equipment for any boiler as it removes the hardness from any water entering the boiler and therefore protects against scale (see Water Treatment section) that reduce the useful life of the boiler and void its guarantee.
Water treatment plants (for demineralization or reverse osmosis) can be used in conjunction with or in place of the water softener.