Rotary Claw Technology Technical White Paper By ERPL India

Table of Contents

1.0 Introduction: Rotary Claw vs. Liquid Ring ……………………………………3

1.1 What is a rotary claw blower? ……………………………………………………..3

2.0 The Rotary Claw Operating Principle……………………………………………4

3.0 Range of Application……………………………………………………………….5

3.1 VCX Performance data……………………………………………………………….6

4.0 Advantages of Rotary Claw Pumps vs. Liquid Ring Pumps…………….7

   4.1 Affordable ……………………………………………………………………………..7

   4.2 Clean……………………………………………………………………………………..7

   4.3 Efficient…………………………………………………………………………………8

   4.4 VFD compatible……………………………………………………………………..8

   4.5 Low maintenance……………………………………………………………………9

   4.6 Compact………………………………………………………………………………..10

5.0 Setting a new standard for Vacuum Application…………………………..11

6.0 About Us………………………………………………………………………………….12

1.0 INTRODUCTION: ROTARY CLAW VS. LIQUID RING

The rotary-claw pump is a well-established standard in many industries internationally due to its inherent efficiency.

Innovative new designs like the ‘VCX’ from Economy Refrigeration Pvt. Ltd. are bringing this technology into the mainstream and stealing the spotlight from that venerable old workhorse; the liquid-ring pump (LRP).

1.1 WHAT IS A ROTARY CLAW BLOWER?

Rotary-claw blowers are not new; they have been used in commercial applications in North America since the early 1990s, and since the mid-’80s in Japan.

At first glance, the inner-workings of a claw pump appear quite similar to those of a rotary-lobe or Roots-type blower. Like the rotary- lobe, the claw is a ‘dry’ positive-displacement pump meaning that there is no lubricant or sealing fluid in the pumping chamber; only close mechanical tolerances between the chamber casing and the precision-machined rotors or ‘claws’ provide the seal required.

In contrast, however, each of the two claw rotors has a unique profile so that as they counter-rotate separate expansion and compression chambers are created. Dry-operation and internal compression are the key features of the highly efficient claw principle.

2.0 THE ROTARY CLAW OPERATING PRINCIPLE

Driven through a set of exterior precision gears mounted on parallel shafts, two claw rotors rotate in opposite directions within the pumping chamber. There is no lubrication required in the chamber. The claws do not touch each other, nor do they touch the chamber walls. 

Figure  captures the key steps of the process as described below:

Position 1: A volume of air is captured at the inlet by the expanding space created as the claws rotate.

Position 2: Each claw effectively traps a fixed volume of air for part of the rotation.

Position 3: The two volumes of air are recombined and compressed until the exhaust port is exposed. Tolerance is very tight at the ‘would-be’ contact point of the claws to prevent backflow from the pressure side to the vacuum side.

One full rotation of the claws is equivalent to two expansion/compression cycles.

While one charge is being compressed and expelled, a fresh charge is being simultaneously drawn in.

3.0 RANGE OF APPLICATION

Airflow and vacuum capacities vary according to manufacturer and model. The Economy VCX series single-stage pump is capable of continuous operation at 75 Torr to180 Torr at flow rates, depending on the specific model, from 60 m3/hr to 500 m3/hr.

Larger airflows can be attained by connecting two or more units in parallel. Higher Vacuum is possible by running 2 VCX pumps in series.

PERFORMANCE CURVES 

3.1 VCX PERFORMANCE DATA

 

MODEL FREQUENCY VCX 60 VCX 100 VCX 150 VCX 250 VCX 300 VCX 400 VCX 505
M3/HR 60 Hz 72 120 180 282 360 462 600
50 Hz 60 100 150 234 300 385 500
ULTIMAGE VACUUM MAXIMUM TORR 38 TORR (50 mbar abs)
ULTIMATE VACUUM CONTINIOUS TORR 75 120 120 150 150 180 180
KW 60 Hz 1.5 2.6 3.6 4.8 6.6 9 11
50 Hz 1.1 2.2 3 4 5.5 7.5 9
R P M 60/50Hz 3450/2850
VOLTAGE AVAILABLE 208-230/460V,220-240/380V,400-690V
db(A) MAXIMUM +-3 TOLERENCE 60 Hz 80 82 82 82 83 85 85
50 Hz 78 80 81 80 82 83 84
OIL CAPACITY (GEAR BOX) LTR 0.6 0.75 0.75 1.1 1.1 1.1 1.1
INLET/OUTLET CONNECTION BSP(G) 1″ 1 -1/2″ 1 -1/2″ 2″ 2″ 3″ 3″
L* X W X H 60 Hz 758X321X461 717X553X368 769X553X368 903X698X526 918X698X526 1039X870X545 1277X870X545
(mm) 50 Hz 736X321X461 707X553X368 744X553X368 906X698X526 1001X870X545 1058X870X545
AMBIENT OPERATING TEMPERATURE DEG C 5 DEGC – 40 DEGC
APPROXIMATE WEIGHTS (KG) 60 Hz 60 113 125 224 228 312 317
50 Hz 55 108 121 218 235 280 285
ACCESSORIES NON RETURN VALVE,VACUUM REGULATOR,EXHAUST SILENCER

 

* Vapour carry over to the pump should not be acidic pH <5

4.0 ADVANTAGES OF ROTARY CLAW PUMPS VS. LIQUID RING PUMPS

4.1 Affordable

Rotary claw technology is now competitive with LRP systems on a capital-cost basis thanks to simplified and effective modern designs. As an example, the Economy VCX model line has been redesigned to reduce the number of parts and to create a more modular unit. Additional benefits include increased efficiency, ease of maintenance and quieter operation.

4.2 Clean

The rotary claw is a dry pump. There is nothing in the pumping chamber to contaminate the air stream. Unlike liquid ring pump systems, there is no fear of oil-carryover or leaks.

Cut-away view of a liquid ring pump.

Airflow necessarily contacts the sealing ring (blue) causing cross-contamination.

Energy is wasted as the impeller acts upon the liquid to maintain a seal.

4.3 Efficient

In comparison to a liquid ring pump, the efficiency advantage of the rotary claw process is obvious. Liquid-ring pumps consume significant energies in maintaining the liquid ring or seal. One can imagine each vane of the impeller pushing a volume of liquid, be it oil or water, around the pump housing on each revolution. Also, there are losses associated with reclaiming, cooling, and returning liquid that is carried over from the exhaust flow into downstream piping.

Additionally, a heat exchanger must be installed in the return line, consuming additional energy with no direct benefit to the actual pumping process. The rotary-claw pump has no seal liquid to push around, and air-cooling is easily achieved with a small, integrated fan. As a result, a rotary-claw pump can produce a vacuum- flow at typically minimum 25% less horsepower than an equivalent liquid-ring pump, which translates directly into significant operational cost savings.

As an example:

Based on published pump flow and power data, a flow of 300 m3/hr at 120 TORR  could be achieved with one 11 Kw LRP, or with one 5.5Kw claw pump. This does not take into account additional horsepower required for cooling the sealing liquid in an LRP system.

4.4 VFD Compatible

Claw vacuum pumps are suitable for use with variable frequency drives. Vacuum- flow versus motor speed is almost linear so that capacity can be easily adjusted to suit the application.

Additionally, with a suitable VFD-capable motor some pumps can be operated at up to 3600 rpm to take advantage of the reserve design capacity of the pump.

4.5 Low Maintenance

The typical LRP system employs a myriad of connections and components, each of which represents a potential for future problems. Liquid levels must be regularly adjusted, monitored and maintained. Seal fluid must be changed as part of a regular maintenance routine. LRP systems may utilize a collection of level switches and solenoids as controls; each of which adds complexity and another opportunity for failure.

The claw compressor has two small gears in a closed oil bath; regular maintenance is as simple as periodically checking the oil. The pump rotors and chamber are non-contacting, and that means no wear. In a typical system, the knock-out water separator and inline filter upstream protect the pump from particles or liquid slugs that would otherwise damage the mechanism.

To prepare the claw compressor for extended shutdown periods, it only requires a cool-down run with clean dilution air for several minutes, or long enough to evaporate any moisture from the pumping chamber.

 4.6 Compact

In comparison to the liquid-ring pump, the rotary claw is dramatically space-efficient. Although a liquid-ring pump is compact in itself, there is the supporting system component to consider. A complete LRP system including pump, motor, seal- fluid tank, and heat exchanger can easily occupy four or more times the floor space of the pump and motor alone. There is also the vertical space and added weight to consider, both of which can be of significance when considering site layout or shipping costs.

A claw pump is self-contained, occupying a fraction of the space of an equivalent LRP system.

Figure G: For vacuum applications this is a representative size comparison of a liquid ring pump with supporting components (right), versus the equivalent self-contained rotary claw pump (below)

5.0 SETTING A NEW STANDARD FOR VACUUM APPLICATION

The modern rotary claw is the product of an established technology that has come of age. Liquid-ring pumps may still have a place in Industry. However, for applications requiring flows up to 500 m3/hr and at continuous vacuum levels from 60 TORR to 180 Torr, the rotary-claw pumps offer competitive cost and none of the problems commonly associated with the LRP process.

The rotary claw vacuum pump can be expected to quickly move to the forefront of popularity in the Vacuum industry.

6.0 ABOUT ECONOMY

Economy Refrigeration Pvt. Ltd. established in 1926, is a leader in the design, engineering and supply of customized Vacuum Systems, Lobe Blowers, Process Gear Pumps, Liquid flow meters, Food X-Ray detection systems, Micronisers and Process equipment. Economy designs & builds complete process vacuum systems, offering solutions for Process /vacuum applications for various industries. The economy with its Corporate office in Fort, Mumbai, and Branches in Chennai, Nashik, Delhi, Hyderabad,   and a countrywide Dealer network reaches out to customers located across the region. The economy has its own works in Chakan, Pune where a stock of finished equipment and spares are available for quick response to customer requirements. We have established a strong and dynamic sales, service and dealer network emerging as one of the fastest-growing companies in these segments. The economy has an experienced, dedicated and technically skilled team of Technicians and Engineers to service a growing number of customers. Along with assistance for the commissioning of our systems, we are equipped to provide prompt after-sales service. We have supplied a large number of Vacuum Systems, Blowers, Pumps, and Flowmeters to several industries in India as well as overseas. These systems are satisfactorily performing in industrial segments like Cement, Steel, Sugar, Chemicals, Auto, Gas Process, Paint, Pharmaceutical, Food Processing, Water Treatment Solutions, etc. Economy supplies equipment to major OEM’s throughout India. We are approved by most Engineering / Project consultants. Excellence with the Economy is our commitment to our Partners.

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