Quaterly Technical Bulletin Issue No.1

June 2015

KGO NewsKGO Group Ltd. is an innovative experienced supplier of a wide range of chemical feed, metering and processing equipment. We offer a range of standard and customized equipment packages, for liquid and bulk solid dry materials and products. We incorporate and provide all the required elements of a complete packaged system, including instrumentation, controls, electrical and mechanical components.

Our equipment supply includes:

• Liquid and Dry Polymer Systems

• Custom Packaged Pump Systems

• Tank & Mixer Packages

• Dispersing Dissolving & Wetting Systems

• Bulk Handling & Storage Equipment

• Starch Cookers

• Specialty Equipment Packages

KGO Group Ltd. incorporates a “proven quality process system” that yields exceptional results, ensuring our clients that each system performs as required, is delivered on time and on budget.

Due to the ever increasing demands of users on the economic efficiency, there is a continuous pressure on the pump manufacturers to challenge the design of progressive cavity pumps. In this edition of Roto Tech, different design variants for universal joints are presented and discussed with regard to their advantages and disadvantages. By the systematic implementation of innovative design concepts in universal joint, it has been possible to realize a leap in technology & create a new generation of progressive cavity pump on a considerably higher technological level.

Progressive cavity pumps are a type of positive displacement pump. Like all type of positive displacement pumps, progressive cavity pump capture liquid in a defined cavity. This cavity is created between a rotating member, usually constructed of steel machined into a single helix, and a stationary member, normally molded elastomers, with a corresponding double internal helix that has a pitch length twice that of the rotating member.

An important consideration of drive train design is the unfortunate characteristics of eccentric motion by the helical rotor. This is an inherent feature of the progressive cavity design. The eccentricity of its rotation is actually a design consideration affecting the capacity or cavity volume of the pump: hence, larger pumps have rotors with greater eccentricities than smaller pumps. Of course, the eccentric motion of the rotor cannot be conveyed into the sealing area of the pumps, where mechanical packing or seals must run on a concentric shaft. To accommodate this transition, a variety of mechanical devices have been employed, the most common of which are the universal joints.

Pump Users International Forum INNOVATIVE DESIGN CONCEPTS FOR OPTIMIZING LIFE COST OF PROGRESSIVE CAVITY PUMPS;

Pin and Bush Type Universal JointIn the widely used pin Joint, the pin transmits forces and moments; i.e. there is no functional separation between axial force and torque transmission. The forces are transferred in undefined line contact under r e l a t i v e m o t i o n . Only a short lever arm is available for f o r c e transmission, so that sliding contact is established with relatively high surface pressure on the pin. The kinematics of this design principle result in relatively h igh wear on the p in jo ints . Systematic analyses of pin joint failures have shown that wear starts in the contact lines of the torque transmission. The axial force acts on t h e p i n , c a u s i n g a n g u l a r displacement relative to the bore of the connecting rod, which in turn results in wear' spirals around the pin circumference.

A further refinement, capitalizing on the purported advantage of the double pin joint, is the Cardan joint. Everyone should be familiar with this design because of its universal use in the automobile industry.

Accepted and refined over the last 100 years, this joint can absorb massive amounts of thrust load and torque. Dynamic loading is distributed over large surface areas covered with needle bearings. Even when used in applications requiring

several hundred horse power, it has proven extremely reliable and durable.

But when applied to a pump, it too has some limitations. The bearings are normally only protected against intrusion from the pumpage of lip seals. Just as these seals are

unacceptable for pin joint pumps, so are they unacceptable for Cardan joint pumps. While

produced in large numbers and relatively inexpensive, Cardan joints are normally not

practically used in applications for less than 75 hp , the power requirement for a fairly small automobile but a fairly large progressive cavity pump. For medium to small pumps, the Cardan joint is too large and will restrict the pumping element inlet.

An interesting characteristic of the Cardan joint is that it must operate with a great deal of angularity. It must “flex”. The motion is required to have needle bearings rotate so they will wear evenly.It becomes a latent advantage and helps to reduce the length of the progressive cavity pumps.

Cardan Type universal joint

50

40

30

20

10

0

25%

Glandpacking

20%

Pinjoint

15%

Rotor

35%

Stator

5%

Other

Perc

enta

ge o

f 10

0 fa

ilure

s Conventional Universal JointsContributes to 20% of Pump Failures.

( )Source: VDMA Frankfurt, Germany.

Sliding block joint

Gear JointIn a Curved tooth joint, torque is transmitted by the gear tooth system. On this design, too however, there is an undefined contact point at relatively high surface pressure at the tooth flanks. Curved tooth joints require joint heads with a large diameter, as the

torque transmission toothed rings extend all the way to the outer diameter of the joint

head, and space is needed for attaching the toothed ring to the shaft and hub. In order to optimize production costs, the toothed rings are often produced

with relatively small diameters, which results in high pressure on the tooth

flanks and hence, high material loss by abrasion at the tooth flanks. Curved tooth

Joints, therefore, also have only relatively short service lives.

Another design variant which is the flexible bar joint. Its kinematics, however, cause high transverse forces on the stator via the rotor, and the axes of rotor and stator do not move in parallel. This results in significantly higher wear on the rotor and stator. As the relatively long flexible bars with their relatively small diameter are prone to become wrapped in the long-fibrous material in the pumped medium, which, may in turn, result in malfunction or failure.

Flexible Shaft

Conclusion

Roto has standardized on the Cardan Type of Universal joints in their Progressive Cavity Range of pumps. Advantages offered include:

Longer Service Life.

Overall length of the pump in reduced.

The limitations of Cardan Joints identified in the article have already been worked on by Roto.

Sealing: By improving the compound of the elastomer and having a much more effective clamping arrangement of the seal cover (Boot Seal). Further, Boot Seal Protectors are also available for highly abrasive and hard solid laden media.

Restricting flow into Pumping elements: Roto has designed the stators with a Tapered entry and this facilitates easy flow of the media into the pumping element.

High Costs / Expensive Design: Well nothing comes for free. Roto believes in providing products that would result lower life cycle costs for the users. This is a standard feature of Roto Progressive Cavity Pumps and comes at a competitive price.

Serv

ice

life

in h

ours

2.000 h

Pin joint

4.000 h

Curved tooth joint

6.000 h

Cardan joint

10.000 h

Sliding block joint

Summary –Comparing service lives of different design variants for Joints

( )Source: VDMA Frankfurt, Germany.

The sliding block joint is a completely new joint technology. Unlike conventional design variants, axial and radial forces are completely separated in a sliding block joint. This patented design principle makes for a clear kinematic situation and allows longer lever arms for torque transmission, so that relatively high torques can be transmitted with smaller joint diameters, compared with conventional solutions. The relatively large contact surfaces for torque and axial force transmission which can be realized, thanks to this design principle result in minor surface pressures and therefore reduced wear.

Roto Pumps forLow & Medium Consistency Pulp

INNOVATIVE SOLUTIONFor handling Medium Consistency Paper Pulp

Benefits of Roto Medium consistencypulp pump

Indian Paper mills were facing difficulties in conveying 12% consistency of paper pulp. The production was getting hampered due to the frequent breakdown of pumps and not able to deliver flow due to the variation of discharge pressure.

The mills were using series of medium consistency centrifugal pumps for conveying the pulp. Since the pulp contains relatively large volume of air, inspite of inducer used at the suction and vacuum system in place, these centrifugal pumps were not able to cope up with the changing pulp consistency ranging from 9% to 12% bulk density. This resulted in the variation of pressure drop in the pipeline and drop in the pump efficiency.

Problem

SolutionThe customer approached ROTO PUMPS for the solution.

Our R&D team developed a progressive cavity pump with a customized oversize hopper and augur arrangement particularly built for handling the difficult task of conveying medium consistency pulp suspensions up to 18% bulk density.

WM series pumps can handle the pulp without any use of the auxiliary vacuum system thus reducing the power consumption and maintenance. These pumps come with a variable-speed drive that can optimize to meet the desired flow rate. The high efficiency and ease of operation makes this technology self sufficient.

• Variable consistencies ranging from 6% to 25%

bulk density during the process can be handled.

• Variable pressure handling capabilities.

• No auxiliary vacuum system required, can

handle air with the pulp.

• Low maintenance cost and easy to maintain.

• Power saving up to 50%.

WM Series Pump3Flow Rate: 120 M /hr.

Discharge Pressure: 24 Bar

The pumps are available in bare shaft and closed-coupled configuration. The hopper size can be customized to suit the customer chute requirement. Material options available as per application requirement.

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