The quality and temperature of feedwater are essential for a boiler to maintain optimal operational efficiency. There are two ways to store and treat feedwater for a boiler — in a feedwater tank, which is open to the atmosphere, or a deaerator, which holds water inside a pressurized vessel. Facility managers looking to make the right investment for their facility and water treatment program often ask us which the better option is.
The main goals of storing and treating feedwater prior to entering the boiler are to:
- Prevent boiler corrosion by reducing oxygen levels
- Avoid thermal shock and pump damage by preheating water
Choosing which piece of equipment is right for your facility will depend on the upfront investment your company is willing to make, the amount of preventive maintenance you are able to conduct every month, and the level of risk you are willing to take on.
| Operational Differences |
A feedwater tank is open to the
atmosphere and holds makeup
water at temperatures ideal for
the boiler system. |
A deaerator holds water inside
a pressurized vessel. The
purpose of a deaerator is to
drive off excess oxygen from
makeup water.
|
| Operating Temperature |
Holds water at temperatures
between 155°F and 185°F.
|
Holds water at a steady
temperature of 225°F.
|
| Oxygen Levels |
Oxygen levels average 5-10
parts per million (ppm).
|
Oxygen levels average 5 parts
per billion (ppb). |
| Maintenance Implications |
A feedwater tank sends water
with high levels of oxygen into
the boiler. Water is treated with
chemicals inside the boiler to
remove oxygen.
A higher degree of preventive
maintenance and monitoring is
required to avoid water
management and equipment
issues.
|
Once the deaerator is installed
and running properly, only
regular scheduled maintenance
of the equipment is necessary. |
Risk of Corrosion or
Contamination |
If the feedwater tank empties
and needs to pull cold city
water to fill the boiler, the cold
water could cause thermal
shock, damaging tubes and
causing boiler leaks.
If the chemical feed is not
working properly and fails to
remove oxygen, the boiler
system could very quickly
corrode, which can cause a
significant amount of damage to
equipment and threaten water
quality.
|
The higher temperature
achieved by the deaerator
alleviates the risk of thermal
shock in instances when cold
water needs to be water
transferred to the boiler.
The higher water temperature
also drives off as much oxygen
as possible before water enters
the boiler, providing added
protection from chemical loss. |
Lifetime Operating Costs
|
The initial investment is lower
than a deaerator because you
are purchasing a container as
opposed to an equipment
system.
Once installed, chemical
treatment costs are
substantially higher than a
deaerator because all oxygen is
removed using chemical
treatment in the boiler. |
Deaerators come with an
upfront investment that covers
the cost of equipment,
installation, certification, and
training.
Additional investment
is in regularly scheduled
maintenance and chemicals to
treat low level of oxygen that is
sent to the boiler.
|
Watertech’s Take
Watertech
recommends facilities utilize deaerators for the consistency, reliability, and
lower lifetime operating cost, but most importantly, for the reduced risk they
provide. Since deaerators remove as much oxygen as possible before the
feedwater even enters the boiler system, if there is a case of thermal shock or
a lost chemical feed, the risk of damage and contamination is far less than
with a feedwater tank.