Viking Universal Seal Internal Gear Pump Options for the Sugar Industry

Viking Universal Seal Internal Gear Pumps are designed to meet the demands of heavy-duty, industrial pumping applications and incorporate essential features for reliable, low-maintenance pumping, even in the most challenging environments.  For applications in sugar refineries, the pumps can be customised with various seal options, increased clearances to minimize shear, and a ribbed idler gear is available for applications involving the handling of solid particles.

Ribbed Idler Option for pumping magma or massacuite

Viking’s ribbed idler reduces gear-to-gear contact - one of the causes of damage to solids, such as sugar crystals, and shear sensitive liquids.  This has been achieved by removing 0.9 mm (0.035” or 900 microns) of material from 80% of the flank of each idler gear tooth, on both sides.  The rib alternates position on each tooth to minimize wear on the rotor teeth in any given spot, and since the idler turns at a different speed than the rotor, the contact point changes with each revolution of the rotor gear.

Ribbed idlers can have an impact on pump performance although this depends on the viscosity of the liquid.  The increased clearances result in additional slip paths that allow liquid to slip back from the high pressure (discharge) side of the pump to the low pressure (inlet) side.  On water-thin liquids, there is a significant decrease in capacity, especially at higher pressures.  On the other hand, with high viscosity liquids, pump capacity is virtually identical to the performance with a standard idler gear.

By selecting a standard or ribbed idler gear, and by changing pump speeds and internal clearances, most sugar producers plants can cover all of their positive displacement pumping needs with one or two sizes of the same Viking pump.  This standardisation simplifies plant operation and maintenance, while increasing reliability and uptime.

The ribbed idler gear is available in hardened iron or hardened steel materials and can be cross-drilled for improved lubrication.

Minimising Shear

Shear can reduce conversion effiency in two phase slurries like massacuite and so needs to be kept as low as possible.  Positive displacement pumps, and in particular, internal gear pumps, are preferred in applications involving shear-sensitive liquids, for example:

• Emulsions (e.g. chocolate and mayonnaise)

• Suspensions (e.g. microspheres in carrier liquids)

• Polymers (e.g. latex, synthetic rubber and long chain polyelectrolytes)

Shear is the relative motion between adjacent layers of moving liquid, and shear rate is the rate of relative motion between adjacent layers of a moving liquid. In a pump, shear rate is a function of:

• The radial clearances between the I.D. of the casing and the O.D. of the rotor

• The rotor diameter

• The rotor RPM

Shear can be minimized by selecting a pump with extra clearances, and by running it very slowly.  For most shear-sensitive liquids, Viking recommends a rotor rim speed of <300 feet/minute.

Syrups and molasses are not shear sensitive so maximum rotational speed is only limited by viscosity and to avoid heat generation which can cause caramelization. 

Seal Options for pumping sugar liquids

An important feature of Viking Universal Seal Internal Gear Pumps is that they are designed to accommodate virtually all types of seal.

Packed Gland

Packed Glands are the most common shaft sealing for sugar liquids because they are simple, forgiving, and handle very high viscosities.  The downside is that they must be tensioned to allow some leakage of liquid for cooling and lubrication of the packing.  Viking’s Universal pumps feature a drip well with tapped port on the bracket to collect leakage at the seal gland and divert it to a collection container.  Packing can be replaced without removing the pump, by loosening the seal gland and sliding it toward the bearing housing, removing the packing rings with a packing hook, and re-packing, alternating the location of the cut on the seal rings.  The bearing housing can be easily removed to slide the gland even further back to provide best access.

Behind-the-Rotor Mechanical Seal

Where leakage is not allowable, mechanical seal options are available.  On H through QS size Viking pumps, the 4124B (non-jacketed) or 4224B (jacketed) series pumps offer an optional Abrasive Liquid Seal with Silicon Carbide faces located immediately behind the rotor.  The rotating face is pinned to the shaft and the stationary face is pinned to the bracket bushing, enabling use on viscosities up to 250,000 SSU, or 55,000 cSt.  The bracket is filled with grease, retained by a lip seal, to lubricate the bracket bushing and minimize air which could enable crystallization at the seal faces.  Viking’s Abrasive Liquid (4624B) Series offers these seals as standard, along with Tungsten Carbide idler pin and idler bushing.

Cartridge Double Seal

Double cartridge seals with hard faces inboard and water barrier can successfully handle sugar liquids to about 50,000 SSU, or 11,000 cSt, which makes them suitable for some syrups and molasses.  These are available on all sizes of Viking pumps.

Cartridge Triple Lip Seal

Cartridge-style triple lip seals are capable of virtually unlimited viscosities, but are not well suited to abrasives.  These are available on all sizes of Viking pumps.  These seals should be used on syrups and molasses with a water flush or steam quench.  They shouldn't be used when pumping massacuite or magma. 

 

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