Technical Bulletin # P-11
The Virtual Impossibility Of
Maintaining A Clean
Condenser Water System Using A Standard
Water
Treatment Program Alone
THE PROBLEM:
Under even the most watchful observation
and strict attention to an "effective" water treatment program, property
owners and managers are finding it increasingly difficult to provide good
corrosion control for their HVAC related piping systems - especially open
condenser water loops. After decades of use, most piping systems eventually
show evidence of fouling with interior deposits - which in turn produces a loss
of flow, reduced heat transfer, maintenance problems, and under deposit
pitting.
Such discoveries often follow years of
acceptable corrosion coupon reports, smooth equipment operation, and little or
no evidence that a corrosion problem even exists. Property managers seeking to
maintain reliable mechanical operations have seen water treatment contracts
increase tremendously in cost, as well as the need for more advanced testing
and automatic feeding equipment. Many have even turned to outside consultants
in order to monitor overall program effectiveness - often at at a cost equal to
that of the entire chemical treatment program!
Yet, even with such actions, condenser
water corrosion rates of 5 MPY are common today, and rates of over 15 MPY are
not unusual. Black pipe seems much more corrosion susceptible now than decades
ago, water treatment chemicals are less effective and more tightly regulated,
and operating demands are higher - just some of the many factors driving
corrosion rates upward.
Common to all severe corrosion problems
is the gradual accumulation of deposits. Typically made up from a combination
of iron oxide, scale, microbiological growths, and airborne particulates, the
buildup of foreign material at the piping interior has a lifelong negative
effect on the pipe itself.
Deposits prevent water treatment
chemicals from protecting the base metal, allow a foothold for microorganisms
to flourish, and eventually lead to under deposit corrosion.
See Technical Bulletin
# C-09 regarding the threat of interior deposits.While deposit
buildup problems are most often associated with open condenser water systems,
it is also a problem for closed circulating systems given a sufficient
corrosion rate over decades of service. See Technical Bulletin
# W-01 regarding corrosion problems at closed circulating
systems.
THE SOLUTION:
Necessary to good corrosion control is
the ability to maintain a physically clean piping system. And absolutely
necessary to producing a clean piping system is adequate filtration. While
closed circulating systems can be easily maintained by installing a small side
steam basket type filter, open systems present special demands.
The high dirt loading of an open system,
at typically large GPM flow rates, requires substantial surface area, and
therefore the need to install large and expensive filtration units. Effective
condenser water filtration requires consideration of all of the following
objectives:
- Full Flow Filtration Is Preferred To Side
Stream Filtration
- Maximum Flow Capacity Is Preferred To
Particle Size Capture
- Sub-Micron Filtration Is Rarely
Necessary
- Filter Placement Is Critical To Overall
Effectiveness
- Installation At The Lowest Point Of The
System Is Preferred
Under even the most ideal circumstances
of having a full flow filtration unit installed, it can only capture those
particulates which are in circulation. Iron oxide deposits which develop and
remain attached to the interior pipe wall will escape capture, as will any
particulates heavy enough to settle out in horizontal or low flow areas.
Testing
Services