POLYDischarge Gear Pump

POLY high-pressure gear pump for thedischarge of medium to high viscosity mediafrom the reactor. The extra large inlet ope-ning guarantees an even flow of product tothe gearwheels even under vacuum or extre-mely low NPSH conditions.

Offered with either a round inlet port, bymeans of which the suction flange of thepump is directly connected to the outletflange of the reactor or as a low NPSH ver-sion, where the pump is connected betweenthe pump and reactor flanges, in order toachieve an even larger and shorter inlet port.

Technical Features

HousingNon-alloyed and alloyed steels . cast steel .

with optional surface coating

GearsNitrated steel . tool steel . special steel .

with optional surface coating . helical gea-ring . herringbone gearing

Friction BearingsTool steel . NiAg (nickel-silver) . Al-bronze .

special materials * with optional surfacecoating

Shaft Seals(Vacuum) viscoseal . stuffing box . combina-tion of viscoseal and stuffing box . double-action, buffered mechanical seal

Heating SystemsHeat transfer oil . steam

Operating Parameters

Viscosityup to 40000 Pas

Temperatureup to 350° (662°F)

Inlet pressureVacuum to max. 40 bar (580 psig)

Differential PressureUp to 250 bar (3225 psig)

The values listed are maximum values andmust not coincide under certain circumstan-ces.

Pump SizesFrom 22/22 (4.7 cm3/U – 10 kg/h) up to280/280 (12000 cm3/U – 30000 kg/h).Intermediate sizes, with wider gear wheelsfor lower differential pressure, are availableas standard, e.g. 152/254 (3,170 cm3/U).

Application Examples

Polymer processingPET . PBT . PA . PC . PS . SAN . ABS . HIPS .

PP . PE . POM . Bio-polymers

There are two types of Poly:a) Standard design: The suction flange is alsothe fastening flange to the reactor.

b) The Low NPSH design: In this case, thefastening flange is designed as an aligningflange and is seated on the delivery side ofthe pump. The pump is clamped betweenthe aligning flange and the reactor flange.This design provides an extremely large andshort suction opening, promoting productflow. The opening can be circular, square orrectangular.

Low NPSH Version

The loss of pressure on the suction side ofthe pump is dependent upon a number offactors. Parameters like viscosity and flowrate are largely predetermined by the pro-cess. According to the Hagen-Poiseuilleequation, the pressure loss is linearly propor-tional to the length of the inlet path andinversely proportional to the fourth power ofthe diameter.

The unique WITTE low NPSH version utilisesthis knowledge and offers an extremely largediameter, short suction inlet.

With the Low NPSH version, the connectingflange is foreseen as a loose flange and islocated on the pressure side of the pump.The pump itself is connected between theloose flange and the reactor flange. This con-figuration allows an extremely large diameter,short suction inlet to be incorporated into thehousing. The shape of the inlet is variableand can for example be round, quadratic orsquare.

Due to the fact that the pressure losses at thesuction side have been reduced to a mini-mum, even critical applications can be relia-bly realised, e.g. discharging high viscosity orfoaming melts.

Typs of Seals

Vacuum Viscoseal with Stuffing BoxThe vacuum viscoseal is a special version ofthe viscoseal and can also be provided withheating or cooling. The return flow to thesuction side is adjusted by means of a needlevalve, so that the choked product forms abarrier. This makes it possible to operate thepump with vacuum conditions on the suc-tion side. Due to the fact that it is a dynamicseal, it is often combined with a bufferedstuffing box. This combination prevents airfrom entering the reactor, even when thepump is at a standstill.

Stuffing BoxThe stuffing box is a simple (static) seal forWITTE gear pumps. It can be provided withbuffering if so desired. The range of applica-tion is similar to that of the viscoseal. Thestandard material used for the packing ismade of expanded pure graphite with struc-tural textile fibres. But it goes without saying,that other materials are also available.

Vacuum viscoseal with lip sealAs an alternative, the vacuum viscoseal canalso be combined with a lip seal instead of astuffing box. The buffer fluid of this staticshaft seal acts as barrier. If the pump is stop-ped for a short time this design prevents airgetting sucked in the pump through the shaftseal.

POLY high-pressure gear pump for the discharge ofmedium to high viscosity media from a reactor

Vacuum-viscoseal withstuffing box

Suction pressure:Vacuum up to 10 bar(abs) (145 psig)

Viscosity:10 - 40000 Pas

Temperature:max. 350° (662°F)

Vacuum-viscoseal withlip seal

Suction pressure:Vacuum up to 10 bar(abs) (145 psig)

Viscosity:10-20000 Pas

Temperature:max. 275° (527°F)

Stuffing box, buffered

Suction pressure:Vacuum up to 10 bar(abs) (145 psig)

Viscosity:0.001-10000 Pas

Temperature:max. 300° (580°F)

The herringbone gearing reduces the pulsa-tion of the medium being conveyed in com-parison to straight and helical gearing. Thisis a great advantage, particularly for poly-mers.

Products with a high solids content are con-veyed better, as the product is more easilydisplaced from between spaces between theteeth. The polymer is also subjected to lessstress. This is particularly advantageous forhighly sensitive polymers, as both shearingand heating effects are reduced during thepumping process.

Existing gear pumps can be converted toherringbone gearing. This merely entailsreplacement of the friction bearings andshafts. Sizes available are: 4 (45/45) to 11(224/224).

Advantages at a glance:

• larger diameter shaft journals, thus increased differential pressure

• Less pulsation• Less stress on the polymers /shearing• Decreased product heating effect• Existing pumps can be converted

Produktes

Differing designs:The "O" design displaces the medium

towards the centre.The "X" design displaces the medium towards

The Herringbone Gearing POLY - Models

Herringbone gears: comparison of pulsation

Poly3D model

Spure gears Helical gears Herringbone gears

Time

46,3-4

92,6-5

176-6

371-7

716-8

1482-9/1

3200-10

6100-11

12000 -12

315

320

380

450

520

584

730

915

1150

125

150

175

200

250

300

400

500

600

50

68

80

100

125

150

200

250

300

260

290

350

400

430

530

640

770

960

1/1 (22/6)

1/2 (22/13)

1 (22/22)

2 (28/28)

3 (36/36)

4 (45/45)

5 (56/56)

6 (70/70)

7 (90/90)

8 (110/110)

9 (140/140)

10 (180/180)

11 (224/224)

12 (280/280)

1,28

2,78

4,7

10,2

25,6

46,3

92,6

176

371

716

1.482

3.200

6.100

12.000

1 - 14

2 - 33

3 - 56

6 - 92

15 - 230

28 - 417

55 - 722

105 - 1370

222 - 2890

430 - 4700

900 - 8850

1920 - 17000

3660 - 32000

6590 - 58000

Size (axial distance width)

Spec. displacement volume (ccm/U)

Capacity (l/h)*

* Dependent on the fluid characteristics and operating conditions

POLY - operating conditions

POLY-Dimensions„Classic“

Pumpsize

371-7

716-8

1482-9/1

3200-10

6100-11

12000-12

18L-320/320

25L-360/360

A

380

450

520

580

715

915

1035

1150

B

200

250

300

400

500

600

700

800

C

80

100

125

150

200

250

250

300

D

377

430

471

540

635

775

850

950

POLY-Dimensions„POLY-S“

Pump size

suction side outside- ∅∅

A

suction side inside- ∅∅

B

suction side inside- ∅∅C

Size

D

CHEM• Transfer• Metering

BOOSTER• Increase pressure• Metering• Transfer

POLY/CHEM• Pre-polymer

discharge and transfer

POLY• Polymer discharge

and transfer

GranulationSpinneryFibre pro-duction

WITTE Presence world wide

Witte Pumps & Technology GmbHEsinger Steinweg 44 a . 25436 Uetersen / GermanyPhone. +49-4122 / 92 87-0 . Fax +49-4122 / 92 87- 49e-mail: info@witte-pumps.de . www.witte-pumps.com

Visit us at: www.witte-pumps.com