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Mixing Resins in Your Float:
Can You? Should You? And What to Look Out For
By Dick Chmielewski
Summary: A little of this and a little of that may work
in spicing a pot of stew, but when it comes to ion exchange float,
you'd better know all the considerations in choosing new resin
to add. More often than not, it's a like-to-like equation. Here,
such issues are discussed in detail for the dealer, who may also
do commercial/light industrial work.
Substitutions of resin in softeners or demineralizers can
be made if proper attention to physical and chemical characteristics
of the resin are kept in mind. What should you consider when facing
the choice of mixing different manufacturers' products when you
need to top-off tanks or add to your float of resin? Not all resins
are identical, even from the same supplier and with the same brand
Important characteristics include
particle size, capacity, moisture content, physical strength,
resin color and taste and odor factors. In addition, floats that
contain anion resins require attention to the type of anion resin
to be used. This article outlines the steps you should take when
faced with this choice. In all cases, the first step is to make
sure you know what's in your float and all of its qualifying characteristics.
Make sure your resin supplier knows what's in the float as well.
In many cases, softening resins can be interchanged without undue
difficulty. Attributes such as capacity and moisture of the new
resins should be closely matched if the resin being topped off
has given satisfactory performance. Also, a float containing fine
mesh resin should generally not be mixed with one of coarse mesh
resin. A resin that has increased water retention due to swelling
from chlorine attack may best be topped off with similar used
resin from other resins from the same float when practical. Although
macroporous resins can be mixed with gel resins in some circumstances,
there is some danger that the stronger resin will crush and or
grind down the weaker resin. Therefore, most substitutions should
be of the same type gel-to-gel or macroporous-to-macroporous resins
as those already in the float.
Finally, while there's no technical
reason, some customers perceive an advantage to dark color or
to light color resin, so it's usually desirable to specify resin
color such that there's no surprise (see Table 1).
Mixed Resin Glossary
acrylicResin base made of polyacrylate rather
than the more common polystyrene.
coarse meshThe larger end of bead size spectrum.
Normal bead size is 16-50 mesh (0.3-1.2 mm). Coarse grade
is typically 16-30 mesh (0.6-1.2 mm). Results in lower
pressure drop for equivalent bed depth.
color throwThe tendency for a new resin to impart
"throw" color to the water being treated. It's
common to have some initial color throw with new resin
for the first several bed volumes.
crosslinkingMost resin beads are made with a polystyrene
crosslinked (chemical bonds
formed between polymer chains) using divinylbenzene (DVB)
as the crossslinking agent.
DVBDivinylbenzene the common crosslinking
agent for making resin beads.
fine meshThe smaller end of the bead size spectrum.
Normally 30-50 mesh (0.3-0.6
floatThe inventory of resin in PEDI (portable
exchange deionization) operation. If it's not designated
to a specific customer or account, it's part of the operator's
or gelularChemical definition of a gel is a colloid
consisting of macromolecules with
adsorbed water, although the macromolecules themselves
are not water soluble. Gels are clear and appear to be
uniform under low power magnification.
macroporousResin polymer structure contains discrete
pores or holes. These pores increase the total surface
area but reduce the capacity. Under low power magnification,
one can see the porous nature of a macroporous resin.
Macroporous resins are opaque.
contentResin beads contain a certain percentage
water. This is known as the moisture content. Oxidation
(or chlorination) of resin beads will increase moisture
content, decreasing bead hardness and strength. In extreme
cases, beads become "mushy" or "gummy".
styrenicResin base made of polystyrene crosslinked
SBAStrong Base Anion resins have the ability
to split a neutral salt, for example, exchanging OH- for
IIRefers to functional group used in SBA
resins. Type I uses trimethylamine. Type II uses dimethylethanolamine.
WBAWeak Base Anion resins do not have the
ability to split a neutral salt.
Separate bed deionizer
In separate bed deionization (DI), or demineralization, floats,
the above comments referring to softener resins generally apply
to those of the cation exchange resins.
Weak base anion resins
In a separate bed DI, the choice of anion resin is far more complicated
than the choice of cation resin. There are many more choices.
Some separate bed floats include weakly basic anion (WBA) resins.
These are almost exclusively macroporous, styrenic weak bases.
Here, the issue of resin color isn't important except for personal
taste and appearance, but the issue of moisture content and capacity
is even more important. The very high capacity weak based resins
with low moisture, such as are used in the sugar industry are
undesirable as make up of demineralizing resins because they are
slow kinetically and don't exchange ions rapidly enough to perform
These resins also have a small and
sometimes significant fraction of strong base capacity depending
on their intended application. With some WBA resins, the strong
base capacity is significant, resulting in high pH and fishy odors
coming from the weak based resin. This would not be a good choice
for potable water, unless specific conditioning of the resin is
practiced. On the other hand, some weakly basic floats depend
on the strongly basic functionality to help remove alkalinity
and carbon dioxide. Here, the weak base acrylic and weak base
polyamine have advantages over their styrenic counterparts, but
they're gel types with different kinetic rates and should be considered
only for total replacement. The polyamine weak base resins are
known to have poor physical stability and are not the best choice
in a float where the resins are regenerated frequently.
Overall, the styrenic macroporous
weak base resins have been the industrial choice due to the best
combination of capacity, durability and cost.
(See Table 2.)
Strong base anion resins
Strong base anion (SBA) resins include Type I, Type II and acrylic
resins. Type I resins are more thermally and chemically stable
than Type II resins. The ion exchange functionality in strong
base resins gradually converts from strongly basic to weakly basic.
The rate at which this happens slows dramatically after the first
year but not until a substantial amount of this conversion has
already happened. Since Type II resins lose salt-splitting capacity
faster than Type I resins, they're not the best choice for floats
where silica leakage is important to the end user. The resulting
combination of efficiently regenerated weak base and silica- and
CO2-removing strong base make these resins excellent performers
on certain waters especially those high in chlorides where silica
removal is also desired. Some operators use topping off as way
to maintain higher levels of strong base capacity of these mixed
The Type I resins are popular because
they provide better water quality, particularly from a silica
leakage standpoint. And, because they're more chemically stable,
they tend to last longer than the Type IIs. However, Type I resins
are more prone to organic fouling, than Type II resins and aren't
the best choice in waters with a tendency of organic fouling-that
is for waters with high total organic carbon (TOC) and/or color.
Acrylic resins are sometimes used in waters that have high levels
of organics, since their functional group makes them a Type I
anion resin that's made on a different polymer backbone. They
enjoy the same improved ability to remove silica.
Acrylic anion resins are thermally
and chemically less stable than styrenic anion resins and instead
of conversion from strongly to weakly basic, they simply lose
capacity. Except for color removal applications, they're rarely
used in portable exchange because of the stability issues and
In separate bed applications, particle
size and color are seldom important issues. However, operators
who identify resin strictly by color can be confused if a new
batch of resin of a different color is ordered. Keep in mind that
batch-to-batch variations occur in all resins, so some color variation
will always occur.
Mixed bed demineralizer
In mixed bed floats, color and particle size become extremely
important issues. Both cation and anion components need to be
evaluated and initial color and final color need to be considered.
Resin color is quite important in mixed beds because color difference
between the cation and anion resin is the primary means of verifying
proper separation during regeneration. In most cases, where Type
I anion resin is used, the cation resin should usually be dark
brown or black. However, when Type II anion resins are used-since
these resins turn very dark red during service-it may be better
to have a light color cation resin.
Particle size in a mixed bed is
far more important than in a separate bed, because the separation
of the two resins depends in part on particle size difference.
However, all resins deteriorate physically over time and an older
mixed bed may not have a significant particle size difference
between the cation and anion resin.
From a chemical standpoint, it's
generally unwise to mix the Type I and Type II resins together.
Thus, a mixed bed float using a Type II anion would generally
not be well served by topping off with the Type I. This is because
of stability and performance differences between the two types
Before making any decision as to
resin addition or full replacement, the float resin should be
evaluated to determine its present condition. This is generally
done by taking several samples at random and having them analyzed
by a qualified laboratory. The result of this analysis is a prediction
of the floats capabilities and overall opinion as to resin condition.
This information is used to determine whether it's time to replace
part or all of the resin or to simply add more resin to make up
for losses. The use of the float and end-user requirements must
be taken into account when deciding what type of resin needs to
be in the float. The industrial customers have far different needs
than pharmaceutical or semiconductor customers. Working mixed
beds have far less stringent purity requirements than polishing
mixed beds but may have faster kinetics, which suggests the same
resin may not do as well in both applications.
All of these factors need to be reviewed before the decision is
made as to whether to top off or fully replace a resin. It is
usually a decision based on performance and economics. Table 3
provides guidelines on replacing resin. The brand of resin to
use for replacement or a determination if a particular resin from
one manufacturer is compatible with an existing float resin can
be made using these facts instead of basing the decision on fear
or ignorance. In the final analysis, it's a combination of planning,
the technical ability and support of the resin supplier in helping
the user to make a good choice.
About the author
Dick Chmielewski is West Coast technical representative for ResinTech
Inc., of Cherry Hill, N.J., and has been in the water treatment
industry for 20 years. He has a bachelor's degree in chemical
engineering from the New Jersey Institute of Technology and a
master's degree in the same study from University of California-Berkeley.
Chmielewski can be reached at (760) 918-0803, (760) 918-0831 (fax)
or email: email@example.com
1. Features to Consider with Softening (Cation) Resin
Level (7, 8 or 10% DVB)
- Total exchange
capacity: Higher crosslinking = higher capacity
- Moisture content:
Higher crosslinking = lower moisture
- Standard distribution
- Coarse mesh
- Fine Mesh
- 50 mesh (0.3 - 1.2 mm)
16 - 30 mesh (0.6 - 1.2 mm)
30 - 50 mesh (0.3 - 0.6 mm)
Gel vs. Macroporous
- Gels are clear
- Macroporous are
Color (and variations)
2. Anion Resin Choices
- Styrenic Type
I and Type II (gels)
- Styrenic Type
I and Type II (porous gels)
- Acrylic Type
- Styrenic macroporous
- Epoxy polyamine
3. Guidelines for Replacing Resin
Acid Cation Resin
- Total capacity falls below 85%
of new capacity
- Moisture content increases more
than 10% above specification
8% crosslinked with spec of 1.95 meq/ml, consider replacing when
total capacity falls below 1.7 meq/ml
For resin with 45% moisture, consider replacing when moisture
increases beyond 50%
When quality can no longer be obtained
Base Anion Resin
- Moisture content
Type 1, when salt splitting capacity falls to 75% of specification
For Type II, when salt splitting capacity falls to 50% of
When silica leakage is excessive
(higher than your customer requires)
When resin no longer rinses to quality and cleaning isn't
Increases more than 10% above spec
Base Anion Resins
- Moisture content
capacity falls to 75% of spec
When resin no longer rinses to quality
Increases more than 10% above spec
Types of Resins
- When irreversible fouling occurs
- Bead integrity
When more than 20-25% beads broke
By Pete Simpson
Summary: The online attacks directed at Yahoo.com and Ebay.com
earlier this yearas well as the Y2K bug threat and imbedded viruses
from last yearhave businesses large and small concerned with breaches
of their information systems and data security. But it's often the things
you do to protect against the small things that will offer you the most
peace of mind.
Information technology, or IT, is a broad concept.
Breach of IT security can result in unauthorized
access of resources, intrusion of viruses, theft of data and loss of competitive
Media exposure leads the public to believe
that most security violations are the results of hackers or "outsiders."
However, many unauthorized acts-including malicious acts-are carried out
by disgruntled employees or "insiders." This illustrates the
importance of securing computer-based resources from both "outsiders"
Who is affected?
Technology has become so prevalent that it affects almost every aspect
of daily life. Computers are at the core of most businesses, ranging from
accounting to credit checking. Computers are responsible for maintaining
bank accounts, medical records, Department of Motor Vehicles reports and
personal and business credit history. Clearly, everyone who has a credit
card or uses an automated teller machine must be concerned with the accuracy
and privacy of their personal information and, therefore, must be concerned
with IT security.
Why is there concern?
Home users and businesses are finding online shopping, or e-commerce,
appealing because of the convenience, simplicity and robustness (not to
mention the often lack of sales taxes required). This widespread availability
and acceptance of computers has dramatically increased the number of people
with the ability to compromise data.
As prices continue to drop and people become
more comfortable with technology, the reliance on computer-based resources
will continue to increase. As this dependence develops, security exposures
may lead to disastrous results with possible financial and legal ramifications.
At a minimum, a security breach will result in lost time and decreased
productivity while a "clean up" effort occurs. More than likely,
however, the results will be much worse. Financial loss as well as non-monetary
effects will occur. For example, if a water conditioning dealership's
customer information was stolen, it would lose credibility, no longer
be able to attract clients and have their valuable information sold to
the highest bidder.
Make information unavailable to those who are unauthorized to access it.
Strict controls are a must to ensure that only those persons who need
access to certain information have that access. The "need-to-know"
works well as the key. The concept of allowing access to information or
resources only to those who need it is called access control.
Passwords are the most common form of access control and the most common
form of security breach is the compromising of these passwords. Requiring
strong passwords is the first step in preventing unauthorized individuals
from accessing sensitive information. Protecting these passwords is one
of the most fundamental principles of computer security.
Imagine your business as a typical suburban
house. A password can be likened to a front door key. No one can enter
the house without the key, but it can easily be lost, misplaced or stolen.
Implementing a strong password policy is inexpensive, doesn't require
technical skills and should be taken extremely seriously. Businesses should
create and implement computer security policy that educates employees
on good password selection, use duration and confidentiality.
Poorly chosen user passwords constitute
the most common threat to computerized data.
There are several recent, dangerous security
vulnerabilities that have been highlighted in national news-but nothing
matches the threat and ubiquity of poorly chosen passwords. In fact, you
could probably combine all the current buffer overflows, input-validation
attacks and data-driven attacks and still not match the menace of easily
Figure 1. Password policy
In general, the following
guidelines should be a part of any password policy:
1. Each Windows 95/98/NT password must be seven or 14 characters long.
Having any other length jeopardizes the strength of the password.
2. Passwords should never contain proper nouns or dictionary words.
3. Passwords should never be popular words, phrases, movies, names
and so on.
4. Each password must differ from the user's login name and any reverse
or circular shift of that login name.
5. Each password must contain at least one numeric character.
6. The new password must differ from the old one by at least three
There are certain policies that can be instituted
(see Figure 1) to make things more difficult for those that would try
to compromise your internal security. There's no easy way to enforce these
guidelines, but their importance has to be impressed on employees at all
levels. For instance, company policy should dictate that users change
their passwords immediately to something more difficult to guess.
Feel nervous about imposing strict password
policies and guidelines? The alternative is easily hack-able systems.
And for those managers and owners who can't understand why data processing
staffs have to make such demands, imagine your salary, stock options and
personal and corporate emails in the hands of the wrong person. Then reconsider
this "inconvenience." Are your systems vulnerable?
Limit resources available to an employee once they have been authenticated
into the computer network or computer. For example, the entire human resources
department might need access to employee information such as addresses
and birthdays, but only certain individuals within the department need
access to compensation information. Access control can be paralleled in
our model house as well. The maid has the front door key so she can come
in and clean, but that key does not unlock the door to your home office
or the safe in the bedroom that contains your important documents.
Integrity ensures that information cannot be modified in unexpected ways.
Loss of integrity could result from human error, intentional tampering
or even catastrophic events. The consequences of using inaccurate information
can be disastrous. Efforts must be made to ensure the accuracy and soundness
of data at all times.
When the validity of information is critical,
it's often helpful to design controls and checks to ensure accuracy such
as batch balancing and control logs.
As individuals and businesses increase information sharing and communication
via the Internet, vulnerability to attack or intrusion rises. Authorization,
access controls, confidentiality requirements and education are some examples
of the technological components available in multi-layered IT security
policy. In the world of technological evolution, everyone is a target
of electronic crime and needs to be concerned about security.
About the author
Pete Simpson is general
manager of UNCO Data Systems of Minneapolis, Minn. His master's degree
in business administration and information sciences is from Pepperdine
University, and he's with UNCO since 1994. UNCO has been in business since
1969 and specializes in information technology for the water conditioning
and bottled water industries.
If you have questions concerning this
column, or if there's a topic you would like addressed, please let
us know. Contact "ComputerWare: or "Dr. IT" at WC&P
Magazine, 2800 E. Fort Lowell Road, Tucson, AZ 85716; (520) 323-6144,
(520) 323-7412 (fax) or email: firstname.lastname@example.org