Rohm and Haas - Emulsion polymer handling guide

24 Pages·4.959 MB·English

EMULSION POLYMER HANDLING GUIDE
TABLE OF CONTENTS
TABLE OF CONTENTS
INTRODUCTION 1
ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM 2-9
Storage Tank Capacity 3
Tank Placement 3-4
Materials of Construction 4
Insulation and Heating 4
Agitation 4
Head Space Humidification 5
Transfer Lines and Fittings 5-6
Pumps 6-7
Valves 7-8
Filtration 8-9
Meters 9
Level Indicators 9
HYGIENE,MAINTENANCE,& SPECIAL HANDLING 10-11
Plant Hygiene 10
Link to Bulletin on Best Practices for Preventing Biocontamination
Treating Biocontaminated Latex 10
Cleaning Tanks,Lines,& Processing Equipment 10
Special Handling Considerations 11
RECEIVING SHIPMENTS 12-15
Sampling 12
Material Sequencing 12
Best Practices for Offloading Tankwagons 12-14
Drumming or Toting Latex from Bulk Shipment 14
Railcar Shipments 14
Drum Shipments 15
Winterized Shipments 15
TEST METHODS 16-17
Solids Content 16
pH 16
Viscosity 16-17
Gel Content 17
PRODUCT STEWARDSHIP 18-20
Product Safety & Health Considerations 18
Toxicity 18
First Aid Measures 18
Ventilation 18
Personal Protection 18
Waste Disposal 18-19
Regulatory Affairs 19-20
Spill Cleanup 20
Fire Fighting 20
EQUIPMENT SUPPLIERS 21-22
continued on next page
INTRODUCTION
INTRODUCTION
Rohm and Haas Company manufactures high quality acrylic and
vinyl/acrylic emulsion polymers at nine facilities in North
America. We designed this bulletin to answer your general
Question: Are the terms "water-based" and "waterborne"
technical questions about these materials and offer tips on
interchangeable with respect to latex coatings?
handling latex products at your plant.For more detailed
information,please visit our Website at The terms have different meaning. "water-based" implies water
http://www.rohmhaas.com and type 'handling guide' in the solubility and as a result,water sensitivity. Top-of-the-line emulsion
polymers from Rohm and Haas are 'waterborne" - they are carried
search window. You may also find useful information in the
in water,but are not water soluble.
Rohm and Haas technical bulletin and material safety data
sheet (MSDS) for the product of interest.
After reviewing these materials,we invite you to discuss your
We would appreciate your feedback on this bulletin,and we'll
plans or unique handling difficulties with one of our technical
use this feedback to keep the brochure informative and up to
representatives,who can be reached at our Philadelphia
date. Please e-mail us at
headquarters @ [phone].
[email protected] or call 1.800.634.0550
The suggestions,procedures,and data in this brochure are
And thanks for your interest in Rohm and Haas products!
based on information we believe to be reliable. They are
offered in good faith,but without guarantee,as conditions and (Updated 09/29/07)
methods of use of our products are beyond our control. We
recommend that the prospective user determine the suitability
of our material and suggestions before adopting them on a
commercial scale. Suggestions for use of our products,or the
inclusion of descriptive material from patents and the citation
of specific patents in the publication,should not be understood
as recommending the use of our products in violation of any
patents or as permission or license to use any patent of the
Rohm and Haas Company. We also suggest that you consult
with the referenced equipment suppliers regarding the safe
installation and use of their products.
continued on next page
ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
Figure 1 is a sketch of a typical bulk storage facility.In designing such a plant,the major considerations
are availability of equipment items,ease of installation and maintenance,and good industry practices.
Other factors that should be taken into account include dependability of operation,service life,
versatility,adaptation of existing equipment,and provision for automated operation.The following
discussion describes the units chosen for the system illustrated in Figure 1 and suggests suitable
alternatives.
continued on next page
ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
STORAGE TANK CAPACITY facilitates cleaning them.A two-inch (or three-inch)
combination inlet/outlet opening at the sloped bottom
We recommend a minimum storage tank capacity of 1.5 to usually suffices.An additional opening with a block valve
2.0 times expected delivery volume to accommodate near the tank bottom is suggested to allow recirculation for
inventory and shipments,plus a reasonable safety factor. mixing or blending or as a alternative entry for emulsion.
You should also consider consumption rates in sizing your The outlet should permit complete drainage of the
tank. The tank should have a capacity equivalent to two contents.Leave a slot in the pad to accommodate this pipe.
weeks of anticipated consumption at the peak order period. All tank fittings should be flanged.
For a consumption rate of one tanktruck per month,an
8,000-gallon tank could hold emulsion sufficient for a week's [Back to Top]
production (1,200 gallons),could accept a full tanktruck
shipment (5,000 gallons),and would provide additional surge TANK PLACEMENT
capacity.We recommend the installation of a larger tank (up In regions where freezing is a concern,tanks for emulsion
to 20,000 gallons) to afford greater flexibility in scheduling service should be installed indoors. Most grades of polymer
deliveries and to furnish additional capacity for higher rates emulsions cannot withstand repeated freeze/thaw cycling.As
of latex consumption. a general rule,emulsions should be stored above 40ºF (5ºC)
at all times. Avoid storage temperatures of 100ºF (30ºC) or
higher for more than a few days at a time to minimize
Table 1 below summarizes common materials of skinning (surface drying).
construction in contact with typical emulsions.
Bulk shipments are normally loaded warm at Rohm and
TABLE 1
SUITABLE MATERIALSa OF CONSTRUCTION Haas plants to prevent freezing in transit in cold weather.
The material remains warm when delivered in insulated
Material Recommended Productsb Comments
tanktruck trailers,but cools quickly to ambient temperature

Austenitic stainless steel SS-304, SS-304L, SS-347, SS-321, SS-316, SS-316L
after unloading.Do not locate tanks in the direct line of

E(apior xdyr-iemdo)d ified phenolic-coated steel Plasite1 7122 radiant equipment such as space heaters and drying ovens

E(bpaokxeyd-)m odified phenolic-coated steel Amercoat2 75, Bisonite3 957, Lithcote4 LC-34 that may cause hot spots in the walls of the vessels.

Phenolic-coated steel (baked) 2A4m, eLrictohacot2t e747 L, CH-e7r3e,s Pitlea5s iPt-e41 0330,5 H5e, rPelsaistiet5e 1I n3d0u6s6t rial, Lithcote4 LC-
Vinyl ester-coated steel Plasite1 4300 Vertical tanks require less floor space than horizontal ones
and tend to be lower in cost because they can be made of
Glass-fiber-reinforced plastics P7o2l,y Hesetteror nty7 p7e0s0, such as Atlac6 382, Dion Cor-Res6 6694, Hetron7 Also suitable for AcrysolTM RM-825.
DVienryalk easntee8r 5ty1pOeNs,, asuncdh A atlsa Dc6e 5ra7k0a ne8 411, Derakane8 470, Atsoplw eccahiyefiscc k cp horeoncd ksuu cwittisat.hb ilrietys info sr upplier lriegchotemr-mgaeungdee dm,abteecraiauls.eH tohreizyo angtgarl atvaantkes sakrien nninogt problems

Plastics pToeflyloent9h yTlFeEn,e T, epfololynp9 rFoEpPy,l eTneefl oSna9r aPnF8A, ,K Kyenla-Fr1120,, nKyyldoenx 11, PVC, Swoitmh eR hpolapslteicxsTM n Eo-t3 c5o8m6.p atible and are difficult to work in and clean.Location above
ground level requires careful determination of the load-
Elastomers NEPaDtuMra Rl uRbubbebre/rN/oNredoepl rVeintreo Bn utyl Rubber Nitrile (Buna N) Rubber Semuiutalsbiloen fso.r F aolrl wsoaltveernbto brnaes ed bearing capacity of the upper floor.If gravity feed is planned,
egEmlPyDcuMolsl/sioN anonsrd dc eoelnt ihtsae rirnesic noognm lym ended. the tank can be installed on an elevated platform made of
reinforced concrete,cinderblock,steel,or timber. The tank
ab TThheessee rmeacotemrimales nhdaavteio bnes eanp ptelys tteod Rahnodp fleoxu nedm suulsitiaobnlse. f oCro unstaec wt Rithoh amll garnadd eHsa,a esx Cceopmtp wahneyr feo rn ostpeedc.i fic information bottom should then be completely supported by a steel
concerning suitability of construction materials.
c Demo unlosti ouns eh amnidldli nsgte eeql,u iirpomn,e ncto.p per, brass, bronze, aluminum, or zinc-coated in lines, tanks, valves, plugs, or in any other plate or a floor of one-inch marine plywood.

1 Wisconsin Protection Coating Corp. 7 Ashland Chemical, Inc., Columbus, OH
2 A Gmreeeronn B Paryo,t eWcIt ive Coatings Div., Brea, CA 89 DDuowPo UntS AC,o .M, iDdluaPnodn, tM CIh emicals, We strongly oppose the use of below-ground tanks.The
3 Trinity Industries, Inc., Dallas, TX Wilmington, DE
45 UHnerioens itTea nPkro Cteacrt iCvoe. ,C Coahticinaggso ,I nILc. , Manitowoc, WI 1 0 3 SMt .C Poarupl.,, MMNar keting Services, disadvantages of below-ground tanks,especially their
6 RReeiscehahroclhd TCrhiaenmgilcea Pl,a Irnkc, .N, C 11 12 KEPllfhe ieAlartdodecexhlp eChmoia .,N, PoMArtt .h L Aamureerl,ic Na,J Inc., inaccessibility for maintenance and the environmental
implications,greatly outweigh their possible benefits.
To prevent foaming,storage tanks should be filled from the
bottom.The tank should be fitted with a three-inch or four- Be sure to consult the applicable engineering,local building,
inch combination vent/overflow drain line (TD on Figure 1), and pollution control codes to determine the possible need
a 22-inch top manway (MW on Figure 1) on a flat or to surround the tank(s) with dikes.This provision may be of
domed roof,and/or a side cleanout manway.Locating the particular concern if tanks are located along waterways.
top manway and vent/overflow drain line close together Dikes around storage tanks will ensure that spilled material
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ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
HEAD SPACE HUMIDIFICATION be reduced by saturating the vapor space over the emulsion
Maintaining a high relative humidity in the tank vapor space with moisture.
will reduce emulsion skinning.Humidification may be
desired in outdoor installations where wide ambient One means of saturating the vapor space is a humidification
temperature variations occur,although with most Rohm and system whereby steam is injected whenever material is
Haas Company's polymer emulsions,such a system is drawn from the tank.Figure 1 shows a simple steam
optional. However,humidification is strongly recommended injection system (HS).Steam is injected through a 0.25-inch
for RhoplexTMWL and MaincoteTM polymers.This is discussed line that enters the top of the tank.A steam filter must be
in the Special Product Considerations Section. installed on the steam line to remove rust and condensate.
Instead of relying on the plant supply,which can be
To understand the need for humidification,it is important to contaminated with bacteria and thus contaminate the
understand the mechanism of film formation.(See Figure 2) emulsion,a small electrically heated boiler that provides 10
pounds per hour or higher is a convenient source of steam.
The lightweight boiler is mounted on a nearby wall
and can be run automatically.
Humidification is most beneficial in an environment where
the relative humidity drops to very low levels.For many
installations,humidification is not needed.
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TRANSFER LINES AND FITTINGS
Emulsions should be delivered to the tank through two- or
three-inch Schedule 5 or 10 stainless steel or two- or
three-inch Schedule 80 rigid plastic pipe.The trucker
connects his hose to this line through a quick-connect
fitting or a two-inch standard threaded male fitting. The
fitting should be supported metal,because plastic thread is
easily sheared off.The emulsion must be delivered below
When an emulsion is applied to a substrate,the polymer
the liquid surface near the bottom of the tank to prevent
particles are separated from each other in water.As water
free-fall and foaming.This is done best by means of an inlet
evaporates,the polymer particles are driven together until
(see Figure 1,'I',on page 2) that enters through the side no
they touch-the point of random densest packing.Capillary
more than 12 inches above the bottom.An external valve
pressure created by the evaporating water deforms the
should be fitted at the point of entry.Install a water-flush
polymer particles,so they coalesce into a continuous
line in the inlet line to permit flushing material into the
polymer film.Several factors,including relative humidity and
tanktruck when loading is complete.Besides cleaning the
temperature,affect the rate of evaporation. The
line,water can be added to the vehicle for the return trip
temperature at which the polymer particles begin to
(10 to 15 gallons is sufficient to avoid extra carrier charges).
coalesce into a continuous film is known as the Minimum
Film-Forming Temperature (MFFT).
Emulsion from the tank can be transferred to mixing vessels
or application equipment through similar stainless steel or
When water evaporates from an emulsion in a bulk storage
plastic pipe.If flow rates greater than 50 gallons/minute are
tank,local agglomeration of the polymer solids may occur
required or transfer is by gravity through long runs,three-
and a skin may then form over the surface and the tank
inch pipe is preferred.Larger pipe is also useful in pumping
walls.Grit may form and settle if the MFFT of the emulsion
formulations,especially viscous ones.
is above ambient temperatures.Skin and grit cannot
redisperse and may cause difficulties in pumping and
The selection of pipe material involves a choice between
formulating.To prevent these problems,the tank should not
the permanence and durability of stainless steel and the low
be emptied completely.Leaving at least two feet of material
cost and ease of installation of plastic.Schedule 5 or 10
is usually effective.In addition,the rate of evaporation can
continued on next page
ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
Type 304 or 304L stainless steel can be used for all lines. Lines should be pitched at least one-half inch per running
Stainless steel is much stronger than plastic pipe and requires foot toward a drain connection to permit draining when
less support.Skinning,however,can be much more necessary.
troublesome in stainless steel.Use stainless steel if the
pumping distance and/or head are great and necessitate the To prevent freezing in outdoor lines,they should be traced
use of positive-displacement pumps capable of producing high electrically or with hot water or water/ethylene glycol lines.
pressures.If threaded pipe is needed,or if lines may be The temperature of the circulating medium should not
subjected to stress or abuse,as in connecting hoses or exceed 120ºF (40ºC) because local coagulation can occur if
operating valves,use the heavier Schedule 40 pipe.Join pipes, the emulsion is overheated. We do not recommend steam
valves,and other connections with clamp couplings,flanged tracing for this reason.
fittings,or other quick-connect fittings.Clamp fittings are
installed more quickly and can be removed more easily for
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cleaning or modification.
PUMPS
Rigid polyvinyl chloride (PVC) pipe is acceptable for service
We recommend air-operated diaphragm (AOD) pumps for
with polymer emulsions. Schedule 80,rigid PVC pipe is
transferring all emulsion polymers. AOD pumps are
recommended for its greater strength.Other plastics,such as
particularly well suited for delivering emulsion polymer at
polyvinylidene chloride,polyethylene,polypropylene,or
high rates of transfer with a minimum amount of shear,and
fiberglass-reinforced polyester,may be employed,but usually
they can be run dry without damaging the pump. They are
at greater cost.Only rigid pipe is acceptable,since flexible
also preferred when the pump is used to handle several
hose requires total support.Plastic pipe can be joined by
grades of emulsions over a wide range of viscosities and flow
adhesive bonding,a rapid and relatively inexpensive process.
rates. The versatility of this type of pump offsets its higher
When using plastic pipe,keep in mind its temperature,
operating cost. When setting up an AOD system,we
pressure,and stress-resisting limitations.
recommend the following:
Most types of valves are suitable,but ball valves,either
stainless steel,plastic,or plastic-coated steel,are preferred
• Choose a pump with 2" min.diameter suction and
because they provide the least amount of restriction. Three-
discharge ports
way valves can be considered for connecting drain lines and
• Fit the pump with Buna-n,Santoprene™,or
water lines and in multiple,feed systems.Motorized valves
Teflon™ balls and seals
are used in automatic systems.
• Install air feed line with ¾" minimum diameter
When possible,the shortest distance should be taken
• Step down air pressure to 60 psi max.
between the tank and processing equipment.During transfer,
the emulsion must be protected from extremes of
temperature. Avoid passing near boilers,drying ovens,and
Protect your pump!
unheated regions in the plant,or insulate the piping if it must
traverse such areas.Include water,inlet and drain connections Install a strainer on the intake side of your pump to avoid
costly pump repairs and down time. See section on
at several points along all lines to allow periodic flushing.If
filtration for more information on strainers.
water is an ingredient of the formulation,it may be added
conveniently through the emulsion pump and lines,thereby
If
flushing residual emulsion and giving closer control of the
AOD pumps are not available,then other types of pumps
polymer content.In general,lines should be left filled with
may be considered for latex service. The suitability of a
emulsion unless they are flushed immediately after every use.
pump for your application may be determined by making a
trial run with several passes of five gallons of latex. An
What is a positive displacement pump? unsatisfactory pump usually fails after only a few minutes of
operation. Pump failure is indicated by coagulation of the
Positive displacement pumps displace liquid by creating a
space between the pumping elements and trapping the emulsion or by heavy gel formation. See our quick reference
liquid in the space.They deliver a known volume of liquid guide on the following page for more data on pumps.
with each cycle of pump operation. This volume is constant
regardless of the resistance to flow in the system. Pumps should be operated under conditions of flooded
suction to prevent working against a vacuum and to eliminate
continued on next page
ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
the need for priming. When used in conjunction with a
VALVES
storage tank,the pump should be installed at or below the
The clear choice among valves for latex service is the full-
base of the vessel. To prevent the buildup of pressure and
bore ball valve with stainless steel ball and TeflonTM seat.
excessive shear,do not run pumps with the discharge line
Plastic ball valves are also acceptable. Ball valves have no
closed. Consider installing a diaphragm type pressure
restrictions which can reduce flow rates or act as sites for
switch. Provide positive displacement pumps with a
shear-induced gel buildup. Use V-ball valves where control
pressure-relief valve on the discharge side to prevent the
valves are required (for ambient temperature products
buildup of pressure when the line is closed. Inspect the
only). Ball valves are also available in a 3-way configuration.
relief valve periodically and flush it after it has been
actuated to prevent sticking. Pumps should be kept full or
Avoid valves with a pivot point or sweeping action,such as
emptied and flushed between uses.
butterfly valves,which are easily fouled by polymer skins
and particles. If you need to adjust the product flow rate,
Stainless steel is the preferred material of construction for
consider controlling the speed of the pump rather than
surfaces of the pump that contact fluid latex. Although
partially closing the valve,as line constrictions impart shear
aluminum pumps have been used successfully in latex
on the polymer. Avoid check valves for the same reason.
service,it is a best practice to empty and flush the pump
between uses when pumping products outside of the
High pressure water cleaning can damage valve seats.
neutral (5 - 8) pH range. Plastic pumps may also be used in
Hence,reduce water pressure or remove valves when
some applications.
you're water-blasting latex equipment.
If using pumps other than AOD pumps,avoid using
As with all equipment in contact with emulsion polymers,
mechanical seals. The best pump packing materials are
avoid components with surfaces constructed of mild steel,
made from soft Teflon™ rope or similar materials. If a
brass,copper,bronze,aluminum,iron or zinc.
polymer emulsion leaks into the packing,it will form a gum
that can freeze the pump. To protect the packing,use a
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water gland through which water is added to the lantern
FILTRATION
ring through ports in the stuffing box or grease fittings. The
wetted packing is kept free of emulsion by the passage of Rohm and Haas filters its emulsion polymers through fine
water through the lantern ring into the pump chamber. Be filter media prior to shipment,so in most cases it is
aware that this arrangement will dilute the latex,although unnecessary to re-filter the material upon delivery.
the amount of dilution may be negligible. A solenoid valve However,dried foam and skins may form in transit
fitted on the water line and controlled by the starting depending on the type of product and conditions of
switch of the pump allows water to flow into the packing transportation. You may remove these undesirable
only while the pump is running. Again,to prevent damage particulates by straining the material when offloading. For
to the packing or other parts,do not allow the pump to bulk shipments,a removable basket strainer installed
run dry. between the tankwagon and storage tank is suitable for this
task. The best strainers are constructed of stainless steel
wire mesh with ? - ¼ inch openings and a total surface area
of at least two square feet,based on typical offloading flow
rates. The rounded edges of the wire reduce shear. Avoid
strainers constructed of punched or drilled metal sheet as
their orifices may shear the latex. Ball valves should be
located on both inlet and outlet sides of the strainer
housing to permit cleaning during the unloading operation.
If offloading with a positive-displacement (gear) pump,then
a pressure relief valve (set at ~60 psi) should be installed
between the discharge side of the pump and the strainer as
safety device in case plugging occurs.
click on chart to enlarge
[Back to Top] All polymer dispersions dry out when exposed to air,
forming non-redispersible particulates that build up in your
storage tank. Heavier coagulum sinks to the
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ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
bottom of the tank to form a sediment,while lighter skins, Avoid mechanical (gear) pumps,very small transfer lines,and
gel and dried foam may form a pad or mat which floats on metering devices with very small clearances. Do not place
the liquid surface of the latex. Don't worry! As long as the filters directly upstream of any metering device as this could
integrity of the gel pad is maintained,the pad will grow in cause inaccurate flow measurement. Always place strainers
size without causing any harm. The integrity of the gel pad on the suction side of pumps and filters on the
is particularly vulnerable when transferring fresh product discharge side.
into a tank with low liquid volume as turbulence from
incoming material may cause the pad to break up. To It is important to set pump speed and pressure as low as
prevent this from occurring,maintain a safe minimum liquid possible to minimize shear on the product. We highly
level in the storage tank. recommend pressure drop indicators to signal filter
blockage. Choose a gauging system that matches the
requirements of your transfer/filter arrangement. Factors
Am I straining or filtering?
include head pressure,filter rating,etc. Contact the
equipment manufacturer for assistance. At a minimum,
Simply put,straining is just coarse filtration - with 20 mesh
mount a single pressure gauge on the filter housing inlet to
(840 u) being the dividing line between the two. As a rule
of thumb,if your device is designed to remove particles alert the operator of the need to change a blocked filter
coarser than 20 mesh,it's a strainer;otherwise,it's a filter. before break-through. Establish and enforce a policy of
using pressure limits to initiate bag changes to prevent bag
failure.
Emulsion polymers should be strained when they are
withdrawn from storage to protect pumps,meters,and Are you over-filtering your latex?
processing equipment against damage by gels,skins and
sediments. Install the same type of coarse strainer assembly Over-filtration is the main cause of shear-induced gel in
many latex polymers. You can prevent gel formation by
as noted above and place it on the suction side of the
ensuring that the filter pore size is not too small and that
pump. Inspect the strainer at regular intervals and clean or
pump rates and pressures are not too high. Contact your
replace the inserts as indicated.
representative for more information.
Should your process require finer filtration,you can install a
filter assembly on the discharge side of the pump. Please Certain emulsion products are sensitive to shear forces and
note that fine filtration requires the use of a low-shear should not be fine filtered. Check with your account
pump;gravity feeds alone will not provide the flow rates representative on the shear sensitivity of your product.
required for efficient processing.All straining/filtering parts
which come into direct contact with emulsion polymers Rohm and Haas technicians draw and analyze a sample from
should be composed of stainless steel or plastic. each shipping container to ensure the quality of the product
delivered to you. All specifications,including maximum gel
Choose filter media composition,construction style,and content,must be met before the product can be shipped.
pore size which are appropriate for your process Contact your Rohm and Haas representative for a copy of
requirements. Bag or cartridge filters are commonly used our quantitative gel test method.
for this task. For bag assemblies,we recommend disposable
(polyester) monofilament mesh-type bags. The bag should [Back to Top]
be backed by a stainless steel support. When using
absorbent media,such as needle-punched felt (fuzzy) bags METERS
or cartridges,you should pre-wet the media to reduce the Weight tanks provide accurate measurements of emulsions,
formation of filter-blinding gels. It is a good practice to but are expensive and add to the necessary cleaning
install a new filter bag before each use. procedures.If you buy emulsions in bulk and use more than
If continuous flow is critical during fine filtration,then install 50 gallons at a time to make formulations,you should
dual filters connected in parallel through a 3-way valve to choose one of the following three automated systems:
permit flow through one filter while the other is being
cleaned or replaced. Alternately,you may consider multiple Batch Metering
bag units to prevent down-time. (VOLUMETRIC MEASUREMENT)
continued on next page
ELEMENTS OF A BULK STORAGE AND TRANSFER SYSTEM
Batch meters are positive-displacement devices used to LEVEL INDICATORS
monitor the feeding of emulsions and other components of If the emulsion is held in an FRP tank,the liquid level is
formulations into mixing tanks.They shorten the time clearly visible through the translucent wall.To improve
needed to charge the tanks by permitting simultaneous feed visibility,a bank of lights is set up behind the tank.
of several components through individual meters at high Calibration gauges are available with large black numerals
flow rates.The meters are equipped with controls that over a bright yellow background to indicate volumetric
automatically shut off pumps and/or close solenoid valves increments.If the contents are not visible,as in an insulated
after a specified volume has been delivered,thereby or metal tank,or to permit automatic readout and/or
reducing batch-to-batch variations in feed composition. monitoring at a distance,use a three- to four-inch
Accurate monitoring of raw material inventories and resin diaphragm load- transmitting cell.Float devices are
consumption is also possible,since most meters contain a unsuitable because of the difficulty in maintaining them in
totalizer to record the delivered volume continuously.Batch clean,workable condition.
meters with oscillating pistons and magnetic couplings
(Badger Model SP-1 or SP-2) work well and are easily For automatic readout and/or monitoring at a distance,use
cleaned,provided that the emulsion is passed through a a Foxboro or Rosemount diaphragm load- transmitting cell.
strainer before entering the meter.Neptune disc meters A port must be fitted on the tank to accommodate the
and Brooks oval-gear meters are also acceptable. indicator.Diaphragm gauges (Foxboro or Rosemount)
properly installed (diaphragm flush with tank wall and
Since these meters measure volume,the average density of electronically transmitted) are useable.Float indicators
the emulsion must be considered for accuracy. (Varec model 6700) with a Teflon,coated vapor-tight float
mechanism can be used in unagitated tanks,but may be
Process Feed Method (Rate of Flow Measurement) unreliable because keeping them clean is difficult.
Batch meters deliver a specific volume of material
regardless of the flow rate or overall time.Some processes Ultrasonic level indicators are also acceptable as a non-
require the feeding of emulsions or formulations into intrinsic method of measuring liquid level.
processing equipment at a defined flow rate.Devices for
measuring flow rate,such asrotometers,diaphragm meters, Glass indicators,such as sight gauges or Tank-O-Meters,
etc.,are unacceptable with polymer emulsion because gum however,are not recommended because they are likely to
formation within them prevents them from operating. plug and become unreadable by deposition of polymer.Do
not use level indicators to control batch feeding because of
If cost is not a consideration,we recommend devices possible inaccuracy in measurement.
without moving parts,like the Micro Motion mass flow
meter or a magnetic flow meter,which work well and are
the most accurate.
Some positive-displacement pumps can be calibrated to
provide a reliable measurement of flow rates.To obtain a
range of delivery rates,a variable-speedmotor or
transmission should be used.
continued on next page