Kirloskar Corrocoat GFC CaseStudy

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IMPROVING LIFE AND EFFICIENCY OF PUMPS & SYSTEMS USING COMPOSITE COATINGS

Cost of energy for pumping water constitutes an important element of utilities for industries. The authorities responsible for pumping water are among the biggest consumer of electricity and in some locations largest single consumer. Cost of electricity in pumping the water over a period of its' life amounts to 90-95 % of the total cost, while 510% relates to purchase of pump and maintenance cost. In any pumping system, over the years, the hydraulic passages of casings and impeller vane shape gets damaged due to wear, tear and corrosion, also the clearance in wearing rings increases substantially. All these damages lead to head & flow losses and ultimately deteriorate hydraulic performance. Due to this deterioration of performance the power consumption increases putting pressure on energy demand due to inefficient operation of pump.

In order to keep balance of energy demand, frequent shutdown of plants are essential. These frequent shutdowns lead to production loss and lower utilization of scarce energy resource. To overcome these situations it is essential to have a longer period between shutdowns and minimal cost for maintenance.

To achieve these objectives high technology composite resin systems along with glass fiber matting technology are available which can be used to refurbish and restore the hydraulic passages of the pump. These passages can be applied with specially formulated energy improvement coating, Fluiglide. The Fluiglide system helps to achieve very low coefficient of friction as compared to original metal substrate. With this, not only performance is improved over existing one but the life of equipment is also increased. Over a period of last 8-10 years number of pumps have been applied with Fluiglide systems. These systems have following attributes: They limit the effect of mechanical damage. They resist chemically aggressive constituents in the service environment. They provide a barrier to prevent permeation of corrosion ions to the substrate. They provide low coefficient of friction.

Most of the pumps, medium and large size, can be effectively treated with polymer resin systems, both old and new. Before deciding the specific polymer system for the pump under consideration its operating and service conditions are studied. Based on the operating and service conditions a appropriate resin system is selected to give protection to the substrate from corrosion and /or erosion. This resin system is then over-coated with Fluiglide. These coatings are known to be effective by two established qualities: 1. The reduction in surface roughness. (Refer Illustration No. 1) 2. The hydrophobic nature of coating. (Refer Illustration No. 2)

1. The reduction in surface roughness : It is well known that surface roughness has substantial bearing on flow characteristics. A rough surface introduces micro or even macro turbulent eddies in the boundary layer causing an increase in velocity gradient. This velocity gradient creates resistance in passage of flow. With the application of coatings surface roughness is reduced by manifolds, thereby allowing the flow to be comparatively less turbulent. Due to this phenomenon overall performance i.e. head and flow characteristics increases. For example the surface roughness of a cast iron substrate is Ra 18.8 microns while surface roughness of Fluiglide coating is as low as Ra 0.4 to 0.08 microns (Refer illustration no. 1). Due to lower coefficient of friction, between the fluid and the coating and hydrophobic nature

2. The hydrophobic nature of coating: When the attractive forces between the substrate and the water molecules exceed the cohesive forces in the fluids, then the water or other media will spread across the surface until a state of equilibrium is reached between the two. Therefore, where the surface energy is high, low contact angles will be achieved and where surface energy or attraction is low, the high contact angles will result in large gradients in velocity between the mainstream flow and the boundary layer. In case of aqueous media, materials which have low surface attraction are hydrophobic and repel water, will result in lower frictional losses than surfaces which are highly attractive to water molecules.

As all common untreated metals have relatively high attraction energies wetting out of the surface with aqueous media and the consequent low contact angle is readily achieved. A substantial reduction in boundary layer friction can therefore be achieved by utilizing a coating, which is hydrophobic. The effects of these are demonstrated below

It has been observed that efficiency gains from coating are presented in two different ways: An increase in flow (water output) for the same input energy (electrical consumption). A reduction in input energy for the same water output. It is possible to obtain the combination of these two extremes and this is usually the case. The actual improvements achieved depend on various factors including the specific speed of the pump.

A lot of experimentation has been carried out by coating small as well as medium and large size pumps and testing them. After the study it has been established that low flow pumps having delivery sizes upto 100-mm size are not amenable to substantial efficiency enhancement by coating. But pumps of delivery sizes larger than 100 mm and impellers with outlet widths larger than 20 mm show a remarkable improvement in efficiency, and discharge rates and head development. The life of coating is generally more than 5 years. The coating can get damaged only by external causes like foreign matter with sharp corners and edges getting into the pump and passing through it or by operation of the pump under cavitation due to inadequate available NPSH or cavitation due to re-circulation during operation at part capacities.

GLASS FLAKE TECHNOLOGYTORTUOUS PATH

Tortuous path for corrosive ion Layers of glass flakes Coating

SUBSTRATE

ADVANCED GLASSFLAKE TECHNOLOGY

The development of in-house Glassflake technology has allowed for the production of the inner more uniform and consistent Glassflake Glassflake can now be made at sub micron thickness

COMPARISONS OF PHYSICAL PROPERTIESDENSITY lbs/cuft ALUMINIUM BRONZE CAST IRON MILD STEEL POLYESTER COMPOSITE EPOXY COMPOSITE 168 557 458 491 104 94 kg/m 2698 8920 7300 7860 166 1550 TENSILE STRENGTH PSIx10 22 33 32 47 117 90 MPa 155 230 220 325 807 621 MODULUS OF ELASTICIY PSIx106 10 15 17 30 18 17 GPa 70 103 120 210 123 120 SHEAR STRENGTH PSIx103 3.0 4.5 26.1 5.0 12.0 9.0 MPa 1.9 31 180 35 83 62

BENEFITS/PROPERTIES OF GLASSFLAKE COATINGS Excellent temperature resistance Excellent chemical resistance Excellent dry and immersed adhesion Low permeation rate Applicable over a wide range of substrates High abrasion resistance Machinability Dimensional stability Reparability Impact resistance High tensile strength High resistance to cathodic disbondment Durability, very long service lives Very low VOC Cost effective

Sr. No.

Liquid Type and Name Clear Water Fluiglide System

Description

Specifications

Attributing Properties of Coating Dry Film Thickness Adhesion layer to ensure proper bonding with respect to Base Metal Anticorrosion Layer

1

Dry Thickness Base Coat

Film

DFT 1000 microns Avg. 100 micron

Tolerance minus

A medium viscosity pre accelerated Bisphenol A polyester glass flake compound, cured by the addition of organic compound. A heavy Built Glass Flake coatings based on low reactivity , Bisphenol A Polyester resin pre accelerated, A two pack resin system sing organic peroxide

Intermediate Coat

Top Coat

A cold cured highly modified chemically resistant, two-pack resin system filled with stabilizing enforcement to reduce cold flow characteristics. The coating should have good gloss with waxy appearance when cured.Film DFT 1500 microns Avg. 100 micron Tolerance minus

Efficiency Layer

Improvement

2

Raw Water , ETP and Sewage Fluiglide E System

Dry Thickness Base Coat

Dry Film Thickness Adhesion layer to ensure proper bonding with respect to Base Metal

A solvent free, high build, two or three pack epoxy coating with excellent erosion resistance, toughness and outstanding erosion properties.

Intermediate Coat

A solvent free, two or three pack epoxy coating with excellent erosion resistance, toughness and outstanding erosion properties.A cold cured 100 % solid epoxide specially modified to give roughness amplitude of 0.08 microns.

Anticorrosion Layer

Top Coat

Efficiency Layer

Improvement

PUMPSAfter 4 years sea-water service

After 7 years service After refurbishment with Corrocoat Corroglass

PUMPSAfter 4 years sea-water service

After 7 years service

After refurbishment with Corrocoat Corroglass, note the wear ring areas using specialist casting techniques

Case Study Background: 20X24 horizontal split casing pumps, 8 Nos. are working for supplying cooling water. These pumps were designed for 70.4 meter head and 4500 M3 / Hr. flow at 90.5% efficiency. These pumps were installed in the year 1985. During the course of operation it was observed that these pumps were operating at lower head at 50.0 meter and higher flow consuming more power and operating with the danger of cavitation. The customer considered trimming of impeller to suit the actual site duties of 4500 M3 / Hr at 50.0 meter head. They approached the manufacturer and informed that with such a severe trimming of impeller there would be loss of efficiency. The trimming was carried out and this resulted in deterioration of efficienc