Typical Fields of Application for Chemical Feeding and Proportioning Equipment Power Generation and Heating Plants Boiler feedwater treatment Inhibition of corrosion and scale formation Water softening Antifoam agent addition p H control Plating Industry Treatment of spent plating solutions Agriculture Plant food additions for irrigation systems and hydroponics Livestock water treatment Municipal Water Supply Addition of coagulating agents Addition of precipitating agents Injection of algicides Water softening Hypochlorination Fluoridation Corrosion inhibition Petroleum Industry Injection of corrosion inhibitors Water softening Equipment lubrication Addition of algicides and bactericides
Catalyst additions Solvent additions Coagulation agents Textile Industry Addition of wetting agents Bleach additions Sizing injection Corrosion inhibition Water treatment pH control Reduce iron content of water Alum additions Process Metallurgy Addition of frothing agents pH control Corrosion inhibition Addition of wetting agents Cement Production Inject Vinsol resin Water treatment Chemical Process and Production Corrosion inhibition pH control Automatic titration Water treatment Solvent injection Blending
Plastics Production Blending Solvent injection Addition of plasticizers pH control Catalyst injection Add softening oils Food Products Water treatment Preservative additions Paper Industry Addition of wetting agents Sizing additions Acid wash control . pH control Injection of antifoam agents Water treatment Photographic Industry Water treatment pH control Automatic titration Corrosion inhibition Blending
The preceding list represents only a portion of the field for application of chemical feeding and proportioning equipment. Almost any situation in which a liquid or liquid suspension is to be added to another liquid could well be studied as a potential application for this type of equipment.
Chemical Feeding and Proportioning Equipment RUSSELL W. HENKE Badger Mefer Mfg. Co., Milwaukee 45, Wir.
This i s a survey of the field of feeding and proportioning chemicals from the application and equipment viewpoints. Equipment discussed i s limited to solution feeding. Tables of corrosion resistance to chemical media for the various materials found in commercial equipment are included.
CHEMICAL
FEEDING equipment consists of units to deliver a specific chemical treatment from a reservoir or other container into the medium to be treated, in a quantity determined by the displacement of the feeder itself. Chemical proportioners, on the other hand, deliver the desired treatment in a quantity determined by a specific ratio of chemical to the quantity of medium being treated. A true proportioner maintains this ratio constant regardless of the quantities involved. It is obvious, then, that a chemical feeder cannot be a proportioner without the addition of equipment t o maintain the constant ratio feature. Applications of chemical feeding and proportioning equipment have developed at a rapid rate in the past decade.
684
Criteria for Equipment Selection Criteria for selecting chemical feeding o r proportioning equipment depend largely on cost, method of installation, and type of solution to be handled. Here are the questions to be answered:
What are the feed requirements? a. Type Solution Suspension Slurry b. Feedrate c. Pressures 2. What classes of equipment meet these requirements? 3. Of the classes available, which a. are most compatible with existing equipment? b. are simplest to operate? c. require the least attention? d. are simplest to maintain? e. require the least auxiliary equipment? 4. If auxiliary equipment is needed, which is a. simplest to opejate? b. easiest to maintain? 1.
INDUSTRIAL AND ENGINEERING CHEMISTRY
VoI. 47, No. 4
LIQUID PROPORTIONERS c.
most dependable?
d. simplest and easiest to install? 5. Will the materials of construction stand the conditions to which equipment will be subjected? 6. What are the economics a. initial cost? b. anticipated service life?
.
Feed requirements will be known; initial cost can be easily determined. Acceptability, auxiliary equipment, materials of construction, and anticipated service life can generally be determined by a study of manufacturer's literature. Compatibility, relative ease of operation and maintenance, some questions related to materials of construction, and need for auxiliary equipment will have to be determined by careful analysis of each individual case. Compatibility is important because a piece of equipment similar to that with which operators are already familiar will receive more ready acceptance and will require less education on operation and maintenance. Although ease of operation and maintenance must be weighed for each case, certain factors are general: accessibility of components which must be frequently inspected or replaced, lubrication points, and adjustments. Auxiliary equipment requires careful study because it is entirely possible for the auxiliaries to cost more and be more complicated than the primary equipment. This usually occurs where an auxiliary meter must be used for flow sensitivity, together with electrical or electronic controls to vary or maintain feed rates in proportion to flow. When aZE of the factors discussed have been carefully considered, then, and then only, should the initial cost be considered. If the cost of equipment selected is out of line with the allotment made, the alternatives are either t o select the equipment which the analysis shows is the best that can be purchased for the amount availa,ble, or to use the analysis in an attempt to get an increase in allotment in order to purchase the most desirable equipment. The engineering approach dictates that the least expensive unit just meeting the requirements is the best choice, but replacement costs, service life, maintenance, and future demands for additional capacity often make the least expensive unit not the rheapest on the market as far as initial cost is concerned.
Equipment Can be Classified According to Delivery Mechanism Piston or plunger pump Diaphragm pump Gear pump Decanter Orifice Crystal solution
Figure 1.
-
Typical piston pump
cPPp I
4
I
Figure 2.
1
Schematic diagram of meter control
. ....
Drive Electric motor Hydraulic ram or air ram Auxiliary take-off Meter driven Feed Intermittent Continuous
Piston- or Plunger-Type Pumps form the basis of the largest Mingle class of chemical feeding equipment. Usually these units i'ollow the design pattern of a single piston in a cylinder, one end of the cylihder fitted with a set of check valves for inlet and outlet, the other end having the packing gland installation. Figure 1 sliows a typical piston pump. A crank arrangement driven by a prime mover, in the case of motor-driven units, or a hydraulic or air ram impart reciprocating motion to the piston. Practically all commercially available units have manual stroke adjustment to vary pump output. This is necessary in order to adjust the rate of chemical injection to conform to variation in main stream flow rate, main stream composition, and similar factors requiring a change in pump displacement. Auxiliary equipment designed by some manufacturers automatically adjusts pump output to variations in flow rate to maintain a constant injection ratio. These units depend on a liquid meter as a flow sensing device, with suitable pickup on the meter
April 1955
I '
Figure 3.
Auxiliary meter flow control
head to relay flow information to a control unit. This type of equipment is usually expensive and should not be specified unless absolutely necessary. Figure 2 illustrates such an installation, and Figure 3 is an actual photograph. Piston- or plunger-type pumps have generally earned a reputation for reliability and accuracy, but have the usual maintenance problems associated with reciprocating equipment: Wearing of the piston cylinder by sliding, friction, and chemical action Packing breakdown, resulting in leakage Crank pin wear Wearing of stroke adjustment mechanism, with some loss of accuracy Necessary lubrication program Maintenance of electric equipment, or air or hydraulic motors Possible check valve difficulty (this has led t o designs incorporating dual check valves on both inlet and outlet sides of the circuit)
I N D U S T R I A L AND' E N G I N E E R I N G CHEMISTRY
685
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT The author has been able to find a dozen manufacturers of chemical proportioning equipment utilizing piston- or plungertype pumps. These are summarized in Table I. Diaphragm Pumps are also reciprocating and therefore are subject to the same driving mechanism difficulties as plunger pumps. These pumps have three advantages over plunger pumps in this regard: Elimination of wear between cylinder and plunger Packing not required Less critical machining
Figure 4. Typical diaphragm pump IN
Their main disadvantage is vulnerability of the diaphragm to puncture, rendering pump completely inoperative. The diaphragm pump cannot operate as a continuous pump unless two or more units are “stacked up” so that the discharge of one overlaps that of the others. Figure 4 is a typical diaphragm pump, and Table I1 lists commercially available equipment. Gear Pumps for chemical feeders are available in only two types, one intermittent, the other continuous. Figure 5 shows the basic configuration of a gear pump, and Table TIT the pertinent data. A New Idea in chemical feeds has recently been presented. Most of the units already discussed here require an independent driving unit. These drives must be installed and controls provided independent of the feed pump. All of these units also require an additional metering unit to sense flow variations if they are to be used in variable flow applications. The new type of unit, combining the flow sensing ability of a liquid meter with ability to perform as a fluid motor and drive the feed pump, is shown in Figure 7. This unit has been designed to utilize hydraulic pressure to drive the pump, thus relieving the meter of the mechanical load of driving the pump. Use of the meter as a driving element for the feed pump results in a unit fully responsive, automatically, to flow changes without need of auxiliary equipment. Nonpositive Displacement types of feeders may be so termed for the sake of comparison with the units discussed above, all of which mechanically displace a fixed volume of chemical each time a cycle is repeated. Nonpositive displacement types may be divided into Decanter Orifice or pressure differential Crystal solution
Figure
5.
Cutaway diagram of gear pump
Feeders of these classifications are listed in Table IV
n
Figure 6.
686
Wallace-Tiernan meter-controlled pump
Figure7.
New unit utilizing hydraulic pressure to drive pump
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 47, No. 4
LIQUID PROPORTIONERS TABLE 1. ’MANUFACTURER
Black, Sivalls & Bryson, Oklahoma
DRIVE POWER
PLUNGER PUMPS
DELIVERY, GAL./HOUR
Gas or air diaphragm ram 15-225
or 1/1-hp. electric 1.1t o 24 motor (hydraulic ram also available) Manzel Div., Frontier In- Electric or gas motors 0.06 to 2 dustries Inc., Buffalo (modification employs reciprocating gas motor) McCord Corp., Detroit, Electric motor; gas or air 0.06 to 6 Mich. cylinder
Hills-McCanna Co., Chicago
1/3-
OPERATING PRESSURE, LB./SQ. INCH
DESCRIPTION
To 10,000 Actuator controlled by toggle valve alternately energizing actuator and exhausting air pressure to atmosphere a t end of stroke. Chemical feed tank pressurized T p 5,000 Reciprocating action from rack and pinion. Plunger stroke set by varying . - “swell” in lostmotion linkage Verticallv mounted dunaer DumD with drive for coiwerting rotary to reiiproiating motion
Plunger pump; rate of injection controlled by prime mover speed or by auxiliary unit on fluid meter Plunger pump; reciprocation generated by crank M & M Tool & Die Co., Electric motor mechanism. Has arrangement where only one Springfield, Ohio . charge of treatment available for delivery to main line a t any one time. Two-stage pump, Only those companies are listed whose equipment is for controlled volume pumping, as contrasted t o general pumping and first drawing chemical from tank, and delivering to feeder, second delivering from feeder to pumping of corrosives. main line Milton Roy Co., Philadel- Electric motor; air cylin- 3 cc. to 405 To 25,000 Plunger pump ball check design; various comphia der variable speed gal./hour binations available. Adaptable to multiple installations in which pulsations of single cylinder pump can be overlapped to approximate continuous feed. “Self-propelled’ ’ Nelson Chemical Pumps, Electric motor; auxiliary 0.018 to 0,228 To 4,000 Cooper, Wyo. to other reciprocating equip. 0 to 15 To 1,000 Neptune Pump Mfg. Co., Electric motor Philadelphia Philadelphia Pump & Ma- Electric motor 7 . 3 to 14.6 To650 Plunger type; reciprocating, crank actuated. “Simplex’’ or “duplex” installations chinery Go., Wynnewood, Pa. %Proportioneers, Inc.%, Electric motor; air or hy- 0.36 to 234 T o 6,000 Multiple installations; auxiliary proportional Providence, R. I. draulic ram flow equipment Small piston-type pump; for low feed rates Wilson Chemical Feeder Electric motor 3cc./hour To 65 Co., Buffalo 6 @./hour Rite-Flo Engineering Co., Meter 24,000 ml./ To 1,000 Unit uses meter to control hydraulic actuated Milwaukee, Wis. hour piston pump; no outside driving means re(6.3 gal./hour) quired: proportional feed over entire flow range of meter without auxiliary equipment (see Figure 8) ~~
~~
TABLE II.
DIAPHRAGM PUMPS DELIVERY,
MANUFACTURER
DRIVE POWER
Infilco, Inc., Tuscon, Ariz.
Air powered
LaDo Insulator Process Equip. - - Div., LeRoy, N. Y. ’%Proportioners, Inc. yo,Providence, R. I. Wallace & Tiernan Co., Newark, N. J.
Electric motor Electric motor Electric or water motor
GAL./HOUR DESCRIPTION 0 to 10 Electrically controlled feed rate. Well suited to laboratory work 16 to 340 Crank adjusted: automatic ratio adiustine: device, air operated 1.75 to 12.38 Suitable for single or multiple unit installations 0.07 to 2 . 8 Pressures to 125 lb./sq. inch. Meter controlled proportioning device available (see Figure 6)
-
Figure
9.
Typical decanter feeder
c
Figure 8. Propor-
‘ROPORTIONER
Top. Typical “in line” installation for meter-driven or metercontrolled proportioners. Bottom. Typical “bypass “installation
April 1955
INDUSTRIAL AND ENGINEERING CHEMISTRY
ZM 687
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT TABLE 111.
GEAR PUMPS
MANUFACTGRER
DRIVE POWER
DELIVERY GAL./HOUR
Central Scientific Co., Chicago, Ill. Edward E. Robinson Co., Nutley, N. J.
Electric motor Electric motor
9 . 5 to 2 . 7 Up to 35.16
TABLE IV.
DESCRIPTION
Continuous feed gear pump; single or duplex units Ratchet mechanism gives intermittent feed, 200 lb./ sq. inch
MISCELLANEOUS FEEDERS
MANUFACTURER
DRIVE POWER
DESCRIPTION
American Paper Mach. and Engineering Wks., Philadelphia Graver Water Cond. Go.
Decanter feed
Hungerford & Terry Co., Clayton, N. J. D. W. Haering & Co., San Antonio, Tex.
Decanter feed Orifice feeder
Calgon, Inc., Pittsburgh, Pa.
Crystal solution
Fischer & Porter Co., Hatboro, Pa.
Rotameter type
Electrically controlled by means of auxiliary meter unit Electrically controlled by means of auxiliary meter unit (See Figure 9) Utilizes pressure drop across an orifice to displace treatment from a reservoir This feeder passes water over treating material in form of crystals in a container and depends' on solubility of the crystals in water Treatment is fed through a small rotameter-type metering tube under vacuum created by a main stream ejector. Reagent flow is controlled by a needle valve
Decanter feed
Materials of Construction Materials most commonly used in construction of chemical feeding and proportioning equipment are ferrous and nonferrous metals, plastics, and in some applications, ceramics. Ferrous materials will be cast iron, steel, the stainless steels, and the specialty high alloys. The alloys are used for pump housings, plungers, valve housings, etc., and selection of the alloy to be used will depend on the chemical to be handled. Copper base alloys are the most common nonferrous metals. Nickel could be used, but is very expensive. Application of light metals such as aluminum and magnesium is almost nonexistent, and titanium has not yet been exploited for this use. In general, the highly alloyed ferrous materials are best suited to oxidizing chemicals. Brasses and bronzes are very resistant to natural and salt waters and alkaline solutions except ammoniacal. Their resistance to oxidizing media and sulfur compounds is usually inadequate, and behavior with water acid solutions may
Plastic
IExcellent,
