Using polyphenylene sulphide in high-performance pumps Engineered plastics are of ten called upon to add durabi l i ty in pumps used wi th harsh fluids at e levated temperatures. Liquid Metronics Inc (LMI) fo l lowed this route when it chose Fortron ® polyphenylene sulphide, a l inear PPS, to prevent cracking and creep in key e lements of its e lectromagnet ic chemical meter ing pumps, which handle corrosive substances. Manufactured by Fortron Industries and sold by Ticona, Fortron PPS has broad appl icat ion in h igh-performance pumps because of its excellent mechanical and other properties, even at temperatures wel l above 200 °C. ~,, ,:i; and ~,o,~:; ........ ~:~ ~ ,::~,;~, ...... (Liquid Metronics lnc) and ~:;~::~= ~ (Ticona) provide the details.

W hen pumps must handle harsh fluids at elevated temperatures, designers are

challenged to find durable materials that consistently deliver high per- formance over the long life of these sturdy products. One option is to turn to an engineered plastic. This was the choice Liquid Metronics Inc (Acton, MA, USA) made to prevent cracking and creep in key elements of its electromagnetic, chemical metering pump line.

These positive-displacement pumps are used m water and wastewater treatraent, laboratory fluid metering, fertilizer injection, papermaking and other industries to dose precise amounts of chemicals. The polymer selected had to withstand exposure to aggressive chemicals, such as sodium hypochlorite, sodium hydroxide, hy- drogen peroxide and sulphuric acid, and their fumes at temperatures to 65 °C, while meeting all mechanical,

thermal and other requirements. LM[ chose Fortron ® polyphenylene sulph- ide (PPS) because it offered the best balance of properties. It is stiff, strong, hard and tough at temperatures well above 200 °C. In addition, it is vir- tually unaffected by acids, bases, alco- hols, oxidizing bleaches and many other chemicals, is inherently flame

retardant, has a low permeability to most liquids and gases, absorbs little moisture, and has excellent dimen- sional stability and electrical proper- ties. Fortron - a linear PPS - is manu- factured by Fortron Industries

(Wihnington, NC, USA) and offered

by Ticona (Summit, NJ, USA, and Kelsterbach, Germany), the technical polymers business of Celanese AG (Frankfurt, Germany). Fortron Indus- tries is a joint venture of Ticona and Kureha Chemical Industry of Japan.

In redesigning these pumps LMI used two grades of Fortron PPS, one to

replace a branched PPS in its Liqui- fram TM pump disc that supports the

diaphragm, and the second to replace a portion of the polypropylene (PP)

in its Duracore T~ spacer upon which the disc rests, forming an improved head-mating surface (Figure 1).

The switch to Fortron 1140L4 PPS in the pump disc greatly reduced the possibility of cracking along the knit line (that is, the zone where two or more streams of molten plastic

meet during injection moulding). The 0.5-cm-thick Liquifram TM disc has an

outside diameter of 5 cm. It is held in place by the circle of head bolts and has eight, 1.7-cm-long feet that

Figure 1. LMI pump parts moulded from Fortron PPS (1140L4-black and 4184L4-black} provide strength, chemical and thermal resistance, and prevent creep. The yellow housing is polypropylene.

0262 1762 /02 /$ - see front matter © 2002 Elsevier Science Ltd, All rights reserved W O R L D P U M P S November 2002 2 7

elevate it in the pumping chamber. A counterbore in the disc accommo- dates diaphragms having diameters of 1.3, 2.0, 2.3 and 4.6 cm to allow for different outputs and pumping pressures.

In addition to having the strongest knit lines of any Fortron product, Fortron 1140L4 has better chemical resistance and flow than the branched PPS used before. It also yields fewer sinks and less warpage and flash (a thin web of plastic that forms at the parting lines in a mould).

Low creep to prevent seepage

The reconfigured Duracore TM spacer

uses a pocket-moulded insert of Fortron 4184L4 PPS set in a glass- filled PP block. The PPS element is a 2.54-cm-deep bowl having an outside diameter of 7.6 cm at its widest point. The head mates with and bolts to the insert, which also supports the feet on the Liquifram TM disc. The mating

surface is moulded to a flatness of _+0.008 cm. The head bolts pass

through the PPS element and into the PP block.

The original design had an all- polypropylene spacer that worked well in all respects except that it would creep somewhat under the 24 inch-pound torque load (2.7 N.m)

Figure 2. Bank o f LMI e lec t romagne t i c chemical mete r ing pumps (ye l l ow & black).

imposed on it by the head bolts. This allowed the bolts to loosen over time, so chemicals having a low surface tension, such as sodium hypo- chlorite, could seep. Such seepage is unacceptable in these chemical pumps, which have service lives of

five or more years and can cycle more than a million times a week at press-

ures as high as 250 psi (about 17 bar).

TABLE 1: PROPERTIES OF FORTRON PP$ GI

Tensile strength, MPa Elongation @ break, % Flex strength, MPa Flex modulus, MPa Notched Izod impact, k Jim 2 Compressive strength, MPa Heat deflection temperature, °C @ 1.8 MPa Continuous use temperature range, °C* Coefficient of thermal expansion, 1/°C Outdoor & water immersion use** Flammability per UL*** Specific gravity, g/cm 3 Moisture absorption, % 24 h immersion Mould shrinkage, %

The inserts made with Fortron

4184L4 resolved the issue of creep in the head mating surface because it has twice the rigidity and flexural, compressive and tensile strength of PP. In addition to low creep, this

:I D] :1.111 J.'1:1 I l l I ~ I II lvi I B'~ IJ i'll ~i[J(

Fortron 1140L4, 40% glass fibre reinforced

Fortron 4184L4, 53% mineral & glass reinforced

165 1.4 250 16.2 7 245 270 200-220 4.6 x 10 -5 Yes VO @ 0.75 mm 1.80 0.02 0.3-0.7

t95 1.9 285 14.5 10 265 270 200-220 5.1 x 10 -5 Yes VO @ 0.38 mm 1.65 0.02 0,2-0.6

* Underwriters Laboratories (UL) 'relative thermal index ratings' ** Per UL746C (minimum thickness = 1.5 mm) *** Thinnest section obtaining 'self-extinguishing' rating

glass-mineral-filled grade has high dimensional stability and chemical resistance, as well as low warpage.

The Fortron linear PPS grades used in the disc and spacer meet stan- dards for an ' f l ' rating from Under- writers Laboratories for outdoor

weathering (UV resistance) and water immersion (resistance to hydrolysis and swelling due to water absorption). Few PPS grades or other plastics have fl ratings. Fortron ® PPS also can be given the distinctive black and yellow colours of LMI's pump line (Figure 2).

LMI solenoid-driven metering pumps undergo extensive testing, including evaluations of head-screw loosening, leakage and how well they meet pressure and thermal protocols. They

are also put through life study tests in simulated chemical metering situations for months at a time at 60 °C with sodium hypochlorite

solutions.

W h a t For t ron ® PPS of fers pump m a k e r s As a versatile pump material, Fortron

polyphenylene sulphide is stiff, strong, hard and tough (Table 1). [t retains these properties at temperatures well above 200 °C, is inherently flame retardant, absorbs little moisture and has excellent dimensional stability

211 WORLD P U M P S November 2002 www.worldpumpscom

and electrical properties. It also fills long, thin and complex parts well. Although PPS is available in bran- ched and linear structures, the linear form (namely, Fortron PPS) has great-

er strength, purity and melt stability.

Fortron PPS is virtually unaffected by acids, bases, alcohols, oxidizing bleaches and many other chemicals at elevated temperatures for exten- ded times. It does not dissolve in most common solvents below 200 -°C and retains its tensile strength and basis weight in contact with fluids ranging from diesel fuel and vege- table oil to hydrochloric acid. It also resists hydrolysis. Tests show Fortron PPS polymers exhibit little or no

change in tensile strength, elonga- tion or weight when exposed to 95 -°C water for more than lO00 hours at 15 psi (ca. 1 bar).

Its low ionic content makes Fortron PPS an excellent electrical insulator. Conductive grades having lower surface and volume resistivities are available for antistatic applications, such as in pumps for combustible

materials. PPS has a low permeability to most liquids and gases, so fugitive emissions through PPS pump walls and chambers are relatively low.

Given its balance of properties, PPS is often used for parts in hot, corro- sive enviromnents in the chemical, automotive, pharmaceutical, food and other industries. It is often used to replace metals, thermoset plastics and more expensive thermoplastics.

Compared to thermosets, Fortron PPS typically generates parts with less flash, replicates fine details better, has better flow properties and allows more design freedom, while delivering far superior mech- anical properties. It also has better hardness, abrasion resistance and weld line integrity than most other high-temperature thermo- plastics. Compared to higher-temp- erature polyesters, for instance,

Fortron PPS has better thermal and chemical resistance and dimensional stability and less creep, thermal expansion and moisture absorption. It also absorbs far less water, so it swells less than high temperature

Figure 3. Water pump impeller moulded from Fortron PPS by Airtex Products (USA) withstands aggressive coolants at elevated temperatures.

nylons during immersion or as

hmnidity levels change.

Fortron PPS is used in a great many applications from appliances, power tools and circuit boards to chemical tower packings, air intake systems, sensors and heater housings, its auto- motive uses include pumps, fuel rails, manifolds, connectors, light sockets and reflectors. Many of these appli- cations involve exposure to fuel,

antifreeze, and transmission and brake fluids at elevated engine compartment

temperatures.

Fortron PPS is especially useful in fuel applications because of its

stability during prolonged contact with gasoline formulations having different octane, sulphur, oxygenate and contaminant levels. A recent

5000-hour study compared how commonly used fuel system plastics

Figure 4. Fuel pump parts (Marwal Systems) moulded from Fortron PPS withstand aggressive automotive fuels over a wide temperature range.

........ www.worldpumps.com W O R L D P U M P S November 2002 2 9

About the companies Liquid Metronics Inc (LMI) man- ufactures electronic and motor- driven chemical metering pumps, controllers and accessories for the water treatment industry. It is headquartered in Acton, MA, and has provided pumps worldwide for over 20 years. The company introduced the first full line of electronic metering pumps, which now extends from low-cost models for domestic potable water treatment to those having sophisticated custom designs.

Ticona, the technical polymers busi- ness of Celanese AG, produces and markets a broad range of engineering polymers and achieved sales of ~g773 million in 2001. The company has production, compounding and research facilities in the USA, Germany, the UK and Brazil.

Headquartered in Frankfurt, Celanese AG is a global chemicals company with leading positions in its key products and world class process technology. The Celanese portfolio

consists of five main businesses: Acetyl Products, Intermediates, Acetate Products, Technical Poly- mers Ticona and Performance Products (oriented polypropylene films, sweeteners and food ingre- dients). Celanese AG (www.celanese. corn) generated sales of around ~g5.1 billion in 2001 and has about 11 800 employees. The company has 30 production plants and five research centres in 11 countries mainly in North America, Europe

and Asia.

age when exposed to nine automotive fuels. The study found that Fortron ® PPS had the least weight and dimensional change and the highest tensile strength retention at elevated fuel temperatures. (Information about the study is available at http://www. ticona-us.com/Literature/documents/ Fuel_Brochure 01 300res72dpi . PDE)

A u t o m o t i v e p u m p examples

Automotive manufacturers use Fortron PPS in a range of pump components, such as impellers, housings, valves, fittings, and filtration media and media support elements. Two automotive pump examples further illustrate the benefits of Fortron PPS.

Water pumps hnpellers made of Fortron PPS in automotive water pumps retain their size and strength while exposed to aggressive glycol 'world long-life coolants'. Organo-acid inhibitors in these coolants prevent particulate formation to extend coolant life to 100 000 miles, but attack aluminiun~ and many plastics.

3O WORLD P U M P S

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November 2002 www.worldpumps.com

In one case, Fortron PPS was chosen over aluminium, cast iron, poly- phthalamide (PPA) and a variety of other nylons for the impellers of automotive water pumps rated

at 115 to 380 litres per minute (Figure 3). Fortron PPS provides the mechanical integrity and dimen- sional stability needed during con- tinuous coolant immersion at temp- eratures to 130 °C. It also allows for complex impeller geometries that promote efficient interaction with the fluid and help the pump fit into tight spaces.

The impellers have diameters of 6.4 to 10 cm, heights of O.5 to 2.5 cm

and rotate at rates to 8000 rpm to circulate coolant through the radiator and engine. The impellers do not deform in the face of rapidly changing rpms and uneven pressures, which at times involve differentials of 30 to 40 psi (c. 2-2.75 bar) across the face of impeller.

Automot ive fuel pump Fortron PPS grades have also found applications in the manufacture of

automotive fuel pumps (Figure 4). In one example, a 65% mineral-glass- filled Fortron PPS provided excellent dimensional stability in high-

volume, gerotor fuel pumps. With running chamber clearances as tight as 0.0025 cm and rotational speeds of 6000 rpm or more, these two-step 39

and 44 mm pumps demand precise tolerances over wide temperature swings and exposures to aggressive fuel blends. Most of their internal components are made of Fortron PPS, including the impeller, cap, cover and inner and outer plates.

Fortron PPS was chosen over a

thermoset, a nylon and branched PPS because it had the best combination of fuel resistance, rnouldability, mach- inability and low mould wear and flash. It is also more resistant to spin welding should the fuel pump run dry because of its high thermal resistance and lubricity. The thermoset plastic had excessive flash and could not give the fine detail needed, especially on impeller fins, while the nylon posed chemical resistance and water

absorption problems.

In s u m m a r y

Fortron linear PPS gives pump makers the advanced properties they need in high-performance, long-life pumps

exposed to aggressive fluids at elevated temperatures. The use of this polymer in LMl's electromagnetic metering pumps is a good example, because it resolved key issues that enable these pumps to perform flawlessly for years while handling sodium hypochlorite, caustic soda, sulphuric acid and other chemicals in demanding industrial environments. •

CONTACTS Kevin Moran Liquid Metronics Inc 8 Post Office Square, Acton, MA, 01720, USA. Tel: +1-978-635-4959 Fax: +1-978-264-9172 E-mail: moran@lmipumps.com www.lmipumps.com

John Dole Ticona 90 Morris Avenue, Summit, N J, 07901, USA. Tel: +1-908-598-4139 Fax: +1-908-598-4319 E-maih John,Dole@ticona.com www.t icona.com

ISO9OO 1 Certif ied J Q A 2 5 ] 2

D A I D O I N T E R N A L G E A R P U M P S S E - S e r i e s a re s u i t a b l e s e r i e s f o r n e w age , b e r n e f r o m r e s e a r c h and d e v e l o p m e n t w o r k s e x e r t e d fo r a l o n g t i m e , b a s e d on G - S e r i e s w h i c h is n o t e d fo r n u m e r o u s s u p p l y r e c o r d s t o c h e m i c a l and e t h e r i n d u s t r i e s . N e w c o n s t r u c t i o n w i t h T a o c l o i d g e a r s d e r i v e d f r o m o u r o w n d e v e l o p m e n t p r o g r a m d e m o n s t r a t e s , f r o m f u n c t i o n a l p o i n t o f v i e w , s u p e r b p e r f o r m a n c e and c a p a b i l i t y f o r g e n e r a l p u r p o s e a p p l i c a t i o n .

• Outstanding performance Oaido Taocloid Gear Pumps have succeeded in reducing discharge fluctuation, vibration and noise at higher revolution to such the extent as to supersede concept of gear pumps thanks to minimum sliding of two mating gear surfaces and closure effect. Higher running speed and wider range of discharge flow than G-Series are attained.

• Logical design Application of one bearing and one metal system achieves compact pump assembly, Supporting structure of pump assembly by casing legs bears larger piping lead (Mechanical seal pumps are without metal but double bearing type)

• Outstanding durability Natural gear mating minimizes rotation load and extend longer service life cycle of wet components. By selecting pertinent material of pinion, water and water containing solution, which used to be dlfficGt to handle with conventional type, are transferable with taocloid gear.

• Easy maintenance Pump rotating assembly can be dismounted without removal of piping connection, thanks to back pull-out system. It is actually not necessary to replenish grease with exterior bearing, because of grease enclosed leak proof type

• Compliance with various piping layout As you may select any of two different arrangements of positioning discharge port in relation web suction port, i.e, V model (Vertical by 90°)and H model (Horizontal), pumps are compatible with various piping layout.

I:llIIII181 ~ Esf.~,11 ~[Cllli'i'4 II = II~ Iq;11Lvll • Larger area of blow section enables complete blow-out. • Liquid blown out from relief valve does not locally recirculate. Superiority in cooling effect minimizes heat generation. • The Dump is so constructed to install relief valve on the super structure regardless of V or H model that eliminates

protrusion and minimizes mounting space. Our built-in-casing relief valve is easy for disassembly works and very convenient for internal checkup.

DAIDO MACHINERY CORPORATION Head office £ Factory:l-26-26, Fukazawacho,Takatsuki, Osaka 569-0035, Japan Tokyo 0ffice:2-2-5, Shibadaimon, Sudo Bidg, 3F, Minatoku, Tokyo ] 05-00] 2, Japan

Tel:6]-796-7]-575] Fax:8]-726-74-4044 Tel :81-3-3433-8784 Fax:8]-3-3433-7590

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www.worldpumps.com W O R L D P U M P S November 2002 31