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TABLE OF CONTENTSDon’t Let Sterilization Bug You 5

Understand your options and the necessary calculations

Case Study: Supplement Company Combines Traditional with Modern 9

Pneumatic weighing moves blended products gently and quickly

Eliminate Static Electricity’s Effects on Analytical Weighing 13

Neutralization techniques keep sample and area around it free of charges

Consider LIW Feeders for Reactive Powders 19

Automated dispensing using loss-in-weight feeders improves the safety and efficiency of

powder handling

Additional Resources 24

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Vac-U-Max • vac-u-max.com 2

Pharmaceutical eHANDBOOK: Fine-Tune Your Pharma Functions 3

www.ChemicalProcessing.com

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The dryer was down. The product

was contaminated. That’s what

the operator called at 11 pm to say.

When I got to the plant, the operator and

I realized the culprit was the long-ignored

steam sterilizer at the inlet to the spray

dryer. The temperature profile showed

the telltale sign of scaling; I reviewed

the trends and discovered we had for-

gotten to pull the exchanger to remove

the scale buildup on the steam side. I

reminded maintenance also to remove

the caramelized coating on the other side:

non-uniformity can burn the product.

Sterilization is an everyday practice at

facilities subject to regulations govern-

ing production of pharmaceuticals and

foods. Several metrics define performance.

The probability that a single bacterium

survived sterilization is expressed as the

sterility assurance level (SAL). An SAL of

10-6 — also known as a “6th log reduction”

— is the minimum acceptable probability

in pharmaceuticals and foods. The “biobur-

den” is the opposite probability. However,

there’s more to it: there must be enough

cells to form a colony; a colony forming

unit (CFU) could range from 70–1,200 cells.

All methods of sterilization suffer from

reliance on a method to determine bug

survivability: usually they use a bacterium

as this “biological indicator.”

Bugs just don’t roll over and die. A rela-

tionship between time and exposure

Don’t Let Sterilization Bug YouUnderstand your options and the necessary calculationsBy Dirk Willard, Contributing Editor,



expresses their resistance. A “D-value”

defines the exposure time, in minutes, at

a given dwell temperature to kill 90% of

the organisms present. D-values intrinsi-

cally relate to conditions: temperature,

humidity and chemical concentration.

A “Z-value” is the temperature change

required to reduce the bug population

from 10 to one (log scale). It’s important

to define a bracket of bug population

versus time with divergent lines at maxi-

mum and minimum temperature. In simple

terms, if the bioburden is 100 CFU, with a

D-value of 0.7 min/log at 115°C, then the

dwell time for a 6th log reduction is: log

(100) + log (106)/0.7 = 11.4 min. There’s an

equation to find equivalent kill time, Fo, at

a different temperature: Fo = 10(T-T*)/Z-value

where T is the new temperature and T* is

the established temperature.

Pharmaceutical and food processors

generally rely on clean-in-place (CIP) pro-

cedures. These fall into three categories:

heat; chemical, e.g., ethylene oxide (EtO),

nitrogen oxide, hydrogen peroxide, chlo-

rine (Cl2) and ozone; and radiation. Plants

tend to favor the latter two categories

because they reduce contamination and

damage; with gas methods like EtO, it’s

easier to separate the product from the

agent. Unfortunately, those two categories

aren’t perfect. For instance, cardboard

absorbs EtO and Cl2 forms toxic chlo-

ramines with ammonia in water while

radiation hardens plastics and scrambles

electronics. In addition, some chemicals

pose a serious health and safety risk, as

exemplified by the 2006 EtO explosion at

Sterigenics. (For details on that incident,

see the video made by the U.S. Chemical

Safety Board: http://goo.gl/j5aJfD.)

Dry heat, which kills by oxidizing the bac-

teria, sometimes is an option. However, it

generally best suits wastes not production

materials. Dry heat lacks the penetration

capacity of wet heat.

You simply can’t beat the right kind of

steam for sterilization. What is the right

kind? A stream with 3–5% wet condensate

will penetrate more effectively than dry

steam, allowing a lower dwell temperature.

Besides, wet steam has a better heat trans-

fer coefficient.

What problems can you expect with

steam sterilization? Well, obviously, scale

buildup and caramelization; wet pack-

ing — allowing excess water to collect

— probably because of steam trap fail-

ure; trapped air — vent the steam and

air someplace; low temperature — often

Bugs just don’t roll over and die.



chosen to preserve products that are

more difficult to maintain at temperature

for the time needed to achieve steriliza-

tion; and, saving the worst for last, poor

CIP practices — cleaning must remove the

bulk of the waste in the pipe for steriliza-

tion to be effective.

Some equipment is especially difficult to

clean and sterilize: filters, sample valves,

thermowells, heat exchangers, centrifuges

and pumps. So, it’s sensible to give special

consideration during design and construc-

tion to avoiding the need for cleaning that

involves disassembly, i.e., clean out of

place (COP).

Most regulations offer some general guide-

lines but lack practical recommendations.

May I suggest:

• “Succeed at Steam Sterilization,”

http://goo.gl/hYi6Gg

• “Guidance for Industry,”

http://goo.gl/oGqNNy

• “Aseptic Processing and Packaging…,”

http://goo.gl/1YT6pb

• “USP Activities Impacting Sterilization…,”

http://goo.gl/jeCSvm

• “Fo Value, D Value and Z Value Calcula-

tions,” http://goo.gl/fUdpcY.

DIRK WILLARD is a contributing editor for Chemical

Processing. Email him at [email protected]

Understand Key Challenges in Process Safety Education

Process safety (PS) academic education has evolved slowly

over the past four decades. University chemical engineering

departments began to establish and deliver process safety

courses in the 1980s. However, the majority of chemical

engineering curricula still do not offer a standalone

course, and fewer make it a requirement.

Chemical Processing, in collaboration with the

Mary Kay O’Connor Process Safety Center, has

developed this Journal to help you better understand

process safety management and solve your challenges.

Predict and Prevent Well-Control EventsRethink Safety and Control Systems Design

UNDERSTAND KEY CHALLE NG ES IN PROCESS SAFETY EDUCATION

FEBRUARY 2021

MKO PROCESS SAFETY JOURNAL

Download the journal at www.chemicalprocessing.com/journals



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With more than 34 years in the

herbal supplement arena,

Traditional Medicinals has

combined the ancient art of traditional for-

mulating with modern scientific methods

of quality assurance and production and

remains dedicated to preserving the earth’s

natural resources, both human and natural.

Operating 70% from solar power, the Sebas-

topol, Calif. company also continues its

commitment to preserving human resources

by continually improving the work environ-

ment for its employees, striving for the most

desirable and safe workplace.

The facility operates 20 hours a day, four

days per week, to produce 2 million teabags

per week. Raw materials are brought in from

around the world in already tea cut form,

reinspected and repackaged into barrel con-

tainers to feed into the blenders via a hopper

system. After the formulas have been

blended, they are transferred to the packag-

ing area and gravity-fed from a mezzanine

level to IMA machines that process between

135 and 185 teabags per minute.

While working on a major efficiency proj-

ect that culminated in the building of new

rooms for the blending area, Mary Goff,

plant manager, says that the company also

wanted “to cut down the amount of lifting

that the operators were doing manually in

our production department.”

Previously, the operators were weighing

individual 100-lb. batches into barrels, taking

Case Study: Supplement Company Combines Traditional with ModernPneumatic weighing moves blended products gently and quicklyBy Doan Pendleton, Vac-U-Max



those barrels up to the top level and then

dumping them into hoppers by hand. In

search of a better method, the VP of quality

control and the site manager researched

open conveyor systems as an ergonomic

solution for transferring the raw materials.

Traditional Medicinals uses pharmaco-

peial-grade herbs, and one of its biggest

concerns was how to transfer the herbs and

blends from one area to another without

breaking down the product or losing any of it.

“We did a lot of studies up front,” says Goff,

of choosing the right systems to transfer

ingredients. “We spoke with some of our

raw materials vendors about the systems

they used to transfer materials, and a gen-

tleman from the consulting firm we were

working with on the efficiency project told

us about Vac-U-Max.”

Belleville, N.J.-based Vac-U-Max specializes

in the design and manufacture of pneumatic

systems and support equipment to convey,

weigh and batch dry materials in the phar-

maceutical, chemical and food industries.

Although the company’s herb suppliers

warned against conveying the herbs pneu-

matically, thinking that it would damage the

ingredients, Traditional Medicinals decided

to look into it anyway.

Pneumatic conveying systems have some

features open conveying systems such as

belt or bucket conveyors don’t have, includ-

ing ease of cleaning and a smaller footprint.

In addition, pneumatic conveying systems

are fully enclosed, protecting materials from

air, dirt and waste. Because product does

not escape from a pneumatic conveying

system, particulates that can endanger or

jam expensive equipment are prevented

from entering the environment.

Despite these advantages, Traditional Medic-

inals needed assurance that the vacuum

system (Figure 1) would perform reliably

without breaking down the product.

STAINLESS STEEL VACUUM RECEIVERFigure 1. Stainless steel vacuum receivers such as this one are ideal for sanitary pharmaceuti-cal and nutraceutical vacuum conveying appli-cations of powders and granular materials.



TRY BEFORE YOU BUY“If the product is too fine, it creates prob-

lems with separation and blending and also

creates problems with packaging if it is

too dusty,” says Goff. “Before purchasing

the equipment, we wanted to be sure that

it could transfer the product correctly and

that it was holding its integrity from a qual-

ity standpoint.”

Vac-U-Max offers testing in its fully func-

tional 6,000-sq.-ft. test and demonstration

facility equipped to conduct a plethora of

vacuum conveying tests to simulate the

actual conditions at a customer’s site.

After consultation with the company to

arrive at system design and equipment

specifications, Goff traveled with the VP

of quality control and the site manager to

New Jersey to test the equipment with 15 of

the company’s raw materials. “They spent a

whole morning with us running through the

testing, making sure that we were happy

with their equipment,” she says.

“One of our biggest concerns was the

breakdown of the materials themselves, and

that’s one of the negatives that we kept

hearing from our herb suppliers, but Vac-U-

Max assured us that it wouldn’t. And they’ve

proven that it is a very gentle way to move

product,” says Goff.

During the testing, it was determined that

the three-filter system initially specified for

the application was capturing more product

than desired, so Vac-U-Max came up with a

single-filter system instead and adjusted the

flow rate.

Because Traditional Medicinals runs

between three and four blends per day

in the department, the conveyor man-

ufacturer set the company up with a

cloth-type cleanable filter that can be

cleaned, sanitized and reused. The com-

pany has several filters on hand for

each blend.

IMPLEMENTATIONWhen the new blending area was finished,

the Vac-U-Max system was implemented

into the new process where raw materials

are brought in and taken to a second level,

run through magnets and then scaled into

a barrel. The pneumatic conveyor system

transfers the product back up to another

room where the system performs as the

hopper feed for the blender itself.

Now rather than operators using forklifts

to bring barrels up to the mezzanine level

and manually scooping materials into the

hopper, operators insert a wand into the

barrels and product pneumatically is trans-

ferred from the wand to the blenders.

“The system has eliminated all the forklift

traffic, and from an ergonomic standpoint

it’s saving a lot of wear and tear on our

blenders’ backs,” says Goff.



In addition to creating a better ergonomic

environment for the operators, Goff says

“their system is more efficient, too, and

we are really happy with that side of it.”

INCREASED EFFICIENCYAlthough Traditional Medicinals hasn’t been

working with the new system long, it has

performed a full protocol of validating the

equipment, process and cleaning proce-

dures. Goff says, “I am predicting that we’ll

be able to improve capacity by 20%.”

CLEANING AND MAINTENANCEWhen running three or four blends a day,

ease of cleaning quickly becomes an effi-

ciency point when sanitation between

runs is required. For this application,

the Vac-U-Max system has a food-grade

polished surface for effortless cleaning

and product flow, and all systems are

equipped with heavy-duty clamps that

enable quick take-apart without tools.

Goff says, “It is very easy to take it apart.

We’re taking it apart three to four times

a day, and we change the filter between

each blend.”

She’s happy with the system’s perfor-

mance, adding, “With the pneumatic

system, transferring the materials is a lot

quicker, and we expect that it will work

well when we bring in a higher capacity

machine later this year.”

DOAN PENDLETON is president of Vac-U-Max and can

be reached at [email protected].



Eliminate Static Electricity’s Effects on Analytical Weighing Neutralization techniques keep sample and area around it free of chargesBy Thomas Pertsch, Sartorius Lab Instruments

Static electricity is a physical phe-

nomenon that can have tremendous

significance in the chemical industry

in many quality control and research and

development laboratories. Electrostatic

charging of materials in industrial processes

and during production sequences or materi-

als analysis can have negative effects.

For example, dosing powders with a spat-

ula or dosing heads risks spreading the

substance so it cannot be brought into

the vessel without spilling. Electrostatic

discharges can damage electronic equip-

ment and components. Spark discharges

easily can ignite flammable substances in

the immediate vicinity, potentially lead-

ing to serious accidents. Millions of dollars

are spent around the world on efforts to

eliminate electrostatic charges and their

associated negative effects.

While simple, low-cost measures are avail-

able to eliminate static electricity during

analytical weighing, current metrological

and practical limitations render many of

them difficult and time-consuming to use,

and they are not universally applicable. Yet

methods exist that are both powerful and

space-saving, particularly when they are

integrated directly into the balance.

BASICS OF STATIC ELECTRICITYStatic electricity results from friction

between two objects (bodies). This fric-

tion process transfers electrons from



objects with a lower work function (dona-

tor) to objects with a higher work function

(acceptor), which results in ion production

(Figures 1a and 1b). A body with excess

electrons takes on a negative charge, while

a body lacking electrons takes on a positive

charge. However, this is only a temporary

change in the charge because any excess

electrons flow off of the body once it has a

certain conductivity or is grounded.

Friction can occur within the sample itself

or between the sample and container or

tare vessel. For example, during convec-

tion in a drying oven, air friction creates a

charge on glass containers, and internal fric-

tion of powders and liquids when they are

transferred between containers creates a

charge on particles within that sample.

In practice, it is impossible to avoid fric-

tion during the processing or transport of

substances. Thus, electrostatic charging

occurs almost 100% of the time. Disruptive

electrostatic forces also can occur in the

area around the balance because of the

direct transfer of charge carriers by people

moving around the balance.

DIRECT IMPACT ON WEIGHING All balance manufacturers are called upon

to respond to the problems of weighing

substances with electrostatic charges with

appropriate technological solutions. Static

electricity can have a negative effect on

either the weighing process itself or on

the results, thus requiring time-consuming

material selection or material handling pro-

cedures to address these effects.

In some cases, weighing

a material may be close

to impossible due to the

build-up of electrostatic

charges during handling.

In addition, the electro-

static properties of some

materials may vary as

ambient humidity rises

and falls, making the

attempt to weigh it even

more difficult. Electro-

static phenomena may be

worse when the relative

humidity falls below 45%,

often the case in winter

ION CREATIONFigure 1a. When two neutral atoms collide or experience friction, the body with the lower work function loses an electron.

Figure 1b. The lost electron moves to the body with the higher work function, and an ion is created. The total charge of the atom on the left is positive (positive ion); the total charge of the atom on the right is negative (negative ion).

a

b



in European latitudes or in air-conditioned

rooms. Therefore, balance users will experi-

ence different conditions from one season

to the next or from one day to the next,

making it difficult to reproduce their results.

Electrostatic charging of materials can

occur in the following conditions:

• in solids, when the surface resistance

of the material Rs > 10 GΩ (according

to IEC93)

• in liquids, with a conductivity of < 10 nS/m

• in conductive materials that are

not grounded

During a weighing operation, the interaction

of electrical charges that have built up on

the material being weighed and the fixed

parts of the balance, which are not conduc-

tively connected to the weighing pan, cause

this electrostatic force.

An electric field builds between the material

being weighed and the fixed parts of the

balance. Some examples of fixed balance

parts include the draft shield or housing

parts, such as the balance base plate.

The resulting electrostatic forces can cause

load changes (displayed values) up to the

order of a gram. In practice, a false absolute

weight is not the only negative effect asso-

ciated with static electricity. Severe drift of

weight readouts and poor results repeat-

ability also are serious problems.

Built-up charges flow off slowly via the

weighing pan, so that the resulting forces

are not constant over time, causing drift

and poor repeatability. Depending on the

polarity the charge carries, the interaction

can be either repulsive or attractive, mean-

ing the weight results can deviate both

positively and negatively. A repulsive inter-

action occurs when both the charge on the

sample and the ambient charge have the

same polarity (both + or both –) (Figure 2).

The material being weighed seems heavier

than it actually is.

REPULSIVE INTERACTION DURING WEIGHINGFigure 2. When both the weighing container and the environment are negatively charged, the resulting force is directed downward (yellow arrow). This makes the sample appear heavier.



An attractive interaction, on the other hand,

occurs when the charge on the sample and

the ambient charge have different polarities

(one + and one –). An attractive interaction

will make the material being weighed seem

lighter than it actually is (Figure 3).

NEUTRALIZING ELECTROSTATIC CHARGESTo eliminate the effects of static electric-

ity on weighing, keep both the sample and

the area around it free of any charges.

One method that has yielded excellent

results to shield the weighing chamber

and the weighing pan from electrostatic

fields is to use a fully transparent conduc-

tive coating on all glass elements of the

balance draft shield.

Another solution includes using ionizers

and antistatic pens near the balance. This

solution works on the principle of surface

neutralization via ion bombardment. In most

situations, surface neutralization is very

effective at reducing charge buildup when it

is helpful to eliminate electrostatic charges

on vessels and samples in the external envi-

ronment of the balance.

Below-balance weighing can be used for

weighing bulky materials, such as plas-

tic blocks. The sample is secured using a

hanger beneath the weighing pan to take

advantage of the proportional reduction

in electrostatic force that occurs with the

square of the distance between the charge

carriers.

This method of reduction of the influence

of electrostatic charges also can be used

while weighing on the weighing pan; any

influence of electrostatic forces on weigh-

ing results can be reduced if the distance

between the sample and the weighing pan

is significantly smaller than the distance

between the sample and the fixed parts of

the balance because the weighing pan pro-

vides an effective shield.

ATTRACTIVE INTERACTIONFigure 3. When the weighing container and the environment have opposite charges, the result-ing force is directed upward (yellow arrow). This makes the sample appear lighter.



However, if the opposite is true, electro-

static charges still will affect the weighing

process. Sometimes it is sufficient to place

an object between the sample and the

weighing pan, reducing the forces to the

point that they have no noticeable effect

on the weighing result. For some appli-

cations, it also is enough to increase the

weighing pan’s shielding effect. For this

purpose, special pans with a greater diam-

eter than standard pans are offered.

A specific balance for weighing filters

that uses a Faraday cage (a grounded

metal shield) can solve the problem of

electrostatic charges. While weighing,

the weighing pan and an electrically con-

ductive cover attached to the pan shield

the filters completely. This filter weighing

balance often is used to determine partic-

ulate matter in emission measurements in

the automotive industry or environmen-

tal institutes.

EQUIPMENT TO AVOID ELECTROSTATIC CHARGE INFLUENCES Generally, the time needed to neutral-

ize electrostatic charges depends on the

sample’s material, surface and shape, as

well as the relative humidity in the bal-

ance’s vicinity.

CUBIS II MICRO BALANCEFigure 4. The Cubis II motorized automatic draft shield includes an ionizer with four jet nozzles for effective elimination of electrostatic charges.



The Cubis II balance offers the Q-Stat

ionizer, which is integrated in the draft

shield I of the modular balance series and

eliminates electrostatic charges within a

few seconds. All glass draft shields use a

fully transparent conductive coating.

In the draft shield I of the Cubis II, four

nozzles jets are positioned in the rear

wall (Figure 4). The physical functional

principle of these nozzles is corona dis-

charge, a process by which a current

flows from an electrode with a high volt-

age into the air. Around the very thin

needle, the electric field strength is so

high that the air molecules are ionized

and create a region of plasma around the

electrode. The generated ions pass the

charge to areas of lower potential. After

recombination with free charges they

form neutral gas molecules again.

The use of four nozzles makes charge

elimination effective. By using opposite

polarity of the nozzles, a kind of focusing

effect in the area of the weighing pan

occurs. This makes the neutralization of

electrostatic charges from sample contain-

ers and substances, for instance, powders,

very effective without disturbing airflows.

This prevents errors from electrostatic

forces in the weight measurements.

Moreover, the fully transparent con-

ductive layer on the draft shield glass

panels provides additional protec-

tion from electrostatic fields in the

immediate proximity of the balance.

This, too, ensures stable and correct

weighing results independently of elec-

trostatic charges.

Cubis II supports different applications

in which an elimination of electrostatic

charges is essential to measure a very

small amount of particles on filters.

THOMAS PERTSCH is product manager at

Sartorius Lab Instruments GmbH & Co. KG,

[email protected].

The use of four nozzles makes charge elimination effective.



mailto:[email protected]

Many chemical and pharmaceutical

process engineers face the chal-

lenge of metered dispensing of

reactive powders into reactors and large

tanks. The requirement to dispense diffi-

cult-to-handle ingredients in a contained

and accurate method is an application that

can be fulfilled and completely automated

using specifically designed loss-in-weight

(LIW) feeders.

The combination of advanced weighing

technology and a contained and sani-

tary feeder design provides for an ideal

automated method of powder delivery,

without the dangers and inefficiencies

of traditional manual powder loading

techniques.

APPLICATION AND PROCESS DETAILSLIW feeders can be designed to dispense

powders into a reactor, tank or large pro-

cess vessel. Figure 1 illustrates a single

feeder, complete with a vacuum receiver

mounted directly above the feeder, that

transfers the powders from the floor below.

Figure 2 illustrates the ability to also incor-

porate a bulk bag frame system above the

feeder to deliver the powder to the feed-

ing/dispensing system. It uses a second,

smaller LIW feeder on a portable weigh

scale to dispense even smaller amounts of a

second powder to the tank.

To provide maximum flexibility, feeders can

be equipped with a special caster system on

Consider LIW Feeders for Reactive PowdersAutomated dispensing using loss-in-weight feeders improves the safety and efficiency of powder handling By Sharon Nowak, Coperion K-Tron



tracks. This enables the feeders to be rolled

in and out of place as required and also be

placed on pneumatic lifts. The feeder in

Figure 3 can be moved forward and back as

well as up and down, and the entire unit can

be moved in and out of position.

In all of these LIW batch designs, the effi-

cient batching program included in the

feeder controller is designed for a metered

flood flow of material out of the feeder until

the total weight of the material fed is within

90% of the batch weight setpoint.

At this point, the controller switches the

feeder automatically into a slower “trickle

SINGLE FEEDER Figure 1. This LIW feeder transfers the powders from the floor below.

LIW FEEDER WITH BULK BAGFigure 2. This feeder incorporates a bulk bag frame system above the feeder.

MOBILE SYSTEMFigure 3. This system can be moved vertically and horizontally as well as to a new location.



feed” mode to reach the final setpoint

weight accurately. Based on the maxi-

mum achievable speeds determined with

calibration, the controller also calculates

the minimum batch time for the speci-

fied material.

WHY LOSS-IN-WEIGHT BATCHING?Batch size, number of materials, material

characteristics and accuracy requirements

all influence which type of batching — LIW

or gain-in-weight (GIW) — is best used.

Figure 4 illustrates the differences in

equipment setup for these two modes of

batching. Typical accuracies to be expected

with the Coperion K-Tron GIW method of

batch weighing are ±0.5% of the full scale

capacity. In other words, when batching

into a reactor or vessel mounted on a scale

or suspended from load cells, the full weight

of the vessel and its contents must be

reflected in the full scale capacity.

Most floor scales or high-capacity load cells

do not have sufficient speed and resolution

to detect small amounts of batched prod-

ucts relative to the larger overall weights

of the tanks, reactors or process vessels.

If accuracy requirements on powders are

in the range of 0.1–0.5%, individual LIW

feeders typically are used with the feeders

mounted on high-speed digital load cells

with 1 part in 8 million resolution in 20 ms.

An LIW batch controller monitors material

weight loss from the feeder hopper and

controls the speed and start/stop function

of the feeder to control the achievement of

the batch weight setpoint.

WEIGHING SYSTEM AND FEEDER PERFORMANCEAny LIW process controller requires accu-

rate high-speed measurement of material

weight changes to provide optimal feeder

control and performance. The weigh-

ing system also must be able to filter out

erroneous measurements that in-plant

vibrations or disturbances cause and be

stable over changes in process room or pro-

cess material temperatures.

The keys to accurate batching are high-

er-resolution weight measurement and

LIW AND GIW SETUPFigure 4. LIW and GIW setups differ; which to use depends on batch size, materials and accuracy requirements.



controller speed. The faster those

weight measurements are taken, the

better the information provided to

the control algorithm, and the better

any vibration filtering algorithm

will work.

The advantages of weight control

through custom technologies can

be a factor in the product quality

and overall manufacturing costs. For

example, some load cells, as shown

in Figure 5, use a vibrating wire

technology based on the theory that

an oscillating wire’s resonance fre-

quency depends on the wire tension

produced when a load is applied.

An applied weight’s force is transferred

to the wire mechanically. The resonant

frequency is measured to determine the

weight. In Coperion K-Tron’s smart force

transducer (SFT) technology, a built-in

microprocessor converts the signal directly

into a digital weight signal. The signal then

is communicated noise-free via RS-485 to

the feeder controller. The KCM-III controller

includes a powerful and fast microproces-

sor, which is ideal for optimizing the batch

weight measurements and their control.

The most recent improvements to the

SFT technology result from a new custom

integrated circuit that allowed contin-

uous measurement and digital filtering

capability at even higher sample rates.

Previously, there were short gaps of time

between capturing the wire frequency,

processing the weight and restarting the

frequency capture.

The new system can capture an integer

number of periods of the weight frequency

using a 30 MHz reference frequency and

never miss a single pulse. The result is truly

continuous measurement. Every SFT pro-

vides a true 8,000,000:1 weight resolution

in 20 ms.

OPTIONS IN CLEANING, CONTAINMENT AND CONSTRUCTIONDepending on the powders to be batched

and frequency of batching, a variety of

VIBRATING WIRE TECHNOLOGYFigure 5. Some load cells use vibrating wire technology to determine batch weight.



design executions can be provided for

the equipment to reduce overall cleaning

or changeover steps. In the case of phar-

maceutical applications, pharmaceutical

feeders provide optimal modularity and

cleanability (Figure 6). The use of stainless

steel for the contact components allows

for ease in cleaning and corrosion-resistant

operation, which also is an advantage in

chemical applications.

Feeders and conveying receivers can

be designed with in-place retractable

spray balls for wash-in-place cleaning

to ensure quick changeover and min-

imal contamination between material

runs. In addition, for toxic chemicals

or pharmaceuticals, incorporating split

butterfly valves at the product outlet

can serve to ensure full powder con-

tainment when the batch is complete

and the feeder moved away from the

vessel or reactor.

When designing for a batching

system, it is important to discuss all

aspects of the design requirements,

including the expected changeover

and cleaning times, optimal desired

batch times, containment requirements

and any issues with height limitations, as

the design requirements for these situa-

tions can greatly affect the overall system

cost.

SHARON NOWAK is business development

manager for Coperion K-Tron USA, Food &

Pharmaceutical Industries. She can be reached at

[email protected].

PHARMACEUTICAL FEEDERSFigure 6. Stainless steel contact components reduce corrosion and make cleaning easier.




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