Ruhrpumpen Pump Solutions Increasing Efficiency ... - Greene Tweed

Case Study

45678

Pump Solutions

INTRODUCTION: Greene, Tweed & Company and RUHRPUMPEN Inc. jointly present this case study. Greene, Tweed is a technological leader in the design, application and manufacture of thermoplastic composite materials. RUHRPUMPEN and its affiliate companies around the world, are innovative leaders in pump technology, design, and manufacture, offering a wide range of products for diverse applications.

According to the DOE, pumping systems account for nearly 20% of the world’s energy demand. The DOE states that “because pumps function as a component of larger systems, companies may overlook opportunities for savings and improved pump system performance”. Additionally, the HI estimates that the typical life span of industrial pumps can be 15 to 20 years. PUMP INTERSTAGE LEAKAGE:

The purpose of this case study is to demonstrate the energy savings, improvements in operational performance, and the resulting positive environmental impact that industrial end users can realize by replacing metal wear parts in pumps with modern thermoplastic composite materials. OVERVIEW: Our focus is on the chemical and refining industries, API, (American Petroleum Institute) pumps and total LCC (Life Cycle Cost) reductions available. This case study will quantifiably document the savings realized in the selected application. We will show that the aggregate available energy savings and resultant positive environmental impact is extremely significant. According to the U.S. DOE (US Department of Energy) statistics, the U.S. Chemical Industry accounts for 25% of all U.S. manufacturing energy consumption. The DOE further reports that in certain industrial plant operations pumping systems can account for up to 50% of all energy consumed. The HI (Hydraulic Institute) estimates that energy consumption can comprise as much as 90% of the total lifecycle cost of owning a pump. Therefore, the opportunities for improving pump system efficiencies, total LCC reductions and positive environmental impacts are extremely significant in this industry sector. Electric power plants are the largest industrial source of air pollutants. The offending pollutants are in the form of smog, soot, carbon dioxide, mercury and particulate matter. Reducing electrical consumption results in lower emissions, leading to a cleaner environment for everyone.

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Pump interstage leakage and internal recirculation are major contributors in overall pump efficiency. Excessively large clearances account for significant decrease in pump efficiency and an increase in energy consumed to operate the pump. Historically, pump manufacturers and repair shops have used metallic parts for wear rings, sleeves, and bushings in API pumps. These metallic parts have the potential to gall and under certain conditions seize. To resolve this, large wear ring clearances were created to prevent the pump rotor and stator from touching off. Although these precautions are taken, galling and seizing problems still haunt end users during conditions of slow roll, pump starts, and in applications where pump suction pressure is close to the vapor pressure of the media being pumped. COMPOSITE WEAR COMPONENTS: In recent years thermoplastic composite materials have been used in place of metal wear rings. These polymer composites have the mechanical strength of metal with the added benefits of non-galling and non-seizing characteristics. As is the case with all materials, there are certain limitations to thermoplastic composite materials. The material is suitable for the majority of API pump applications where the potential gain is significant. We will recommend appropriate materials for specific applications once our customers have provided accurate operational data. Greene, Tweed manufactures various high performance wear materials that will not gall or seize. These W materials enable the pump to operate safely at clearances that are approximately half what API currently recom-

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Case Study

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Pump Solutions

mends for metal wear rings (see Table 1). In reducing wear ring clearances, interstage leakage and recirculation are reduced. The result of reduced internal recirculation is increased pump efficiency. Table 1 Diameter of Rotating Member at Clearance Joint (Inches)

Minimum Diametrical Clearance (Inches)

API 610

W Composite

4.500 to 4.999

.016

.006

5.000 to 5.999

.017

.006

6.000 to 6.999

.018

.007

7.000 to 7.999

.019

.008

8.000 to 8.999

.020

.009

Polymer composite materials are not new to the centrifugal pump market. These materials have been used for a number of years by some of the worlds leading refineries and petrochemical producers to improve pump efficiency and reliability. In the recently released API 610, Ninth Edition, polymer based composites are listed as an acceptable option for the replacement of metal wear materials in appropriate applications.

performance test was then performed complete with NPSHR (Net Positive Suction Head Required) test. The pump was then disassembled and inspected for any rubbing or other problems. No problems were found. The performance curves in Figure 2 are identified for the W wear parts. The composite parts were then replaced with standard chrome wear rings. The chrome ring clearances were Impeller Eye .020" (API stated minimum clearance) and Impeller Hub was .023" (slightly larger than API stated minimum of .019"). The composite wear ring clearances were .009" for the Impeller Eye and .008" for the Impeller Hub. TEST RESULTS: The pump curve in Figure 2 shows pump efficiency increased significantly with the W composite wear rings. Measurements show the average efficiency improvement is 2.5%, with an improvement in NPSHR. A retrofit and test on a larger multi-stage pump would achieve an even higher efficiency gain. Figure 2

PUMP TESTING: We selected for testing a RUHRPUMPEN 6X8X13'L SCE single stage overhung process pump API Eighth Edition, with 8" suction, 6" discharge, and 13.469" diameter impeller. The pump was driven by a 125HP electric motor, pump speed was 1770 RPM, and water was used as the test media (specific gravity .9989 at 61°F). We selected this popular pump design because it is the workhorse pump of chemical plants and refineries. It is common for individual plants and refineries to have hundreds of single stage overhung pumps of varying capacities running twenty-four hours a day, 365 days a year. For our test the SCE pump was fitted with W composite material for the impeller eye and hub wear rings, and throat bushing. A standard API 610, Eight Edition


The 2.5% improvement in efficiency gains translates directly to bottom line savings, where the same amount of process flow is achieved for less money. Actual savings realized will vary based upon hours of operation and local energy costs. For comparison purposes we have selected typical industrial electric rates for the states of Texas and California (see Table 3).


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Pump Solutions

Table 3 State

Texas

Table 4 Cost per Reduction in Dollars Cost of kWh kWh usage saved W retrofit $ 0.0442 (20,148) $ 891 $ 980

California $ 0.072

(20,148)

$ 1,455

$ 980

Simple payback (years) 1.10 .67

Note: The $980 retrofit cost represents typical costs for the size and type of pump tested. Actual costs will vary by pump type, application and other factors.

Table 3 shows the annual savings based upon energy costs of $0.0442 and $.0.072 per kWh (the industrial average costs for Texas and California respectively) for 8760 annual hours of operation. The reduction in kWh usage translates into significant savings even in the case of relatively inexpensive Texas power costs. In the case of higher California electricity costs the results are much more dramatic. In either scenario, the simple payback for the initial investment in the superior W material is less than 1.1 years. ENVIRONMENTAL IMPACT: The testing demonstrates that the available annual reduction in electricity consumed is 20,148 kWh when fitting the pump with W composite materials. This reduction in consumption will also minimize the pollutants caused by the generation of electricity. The reduction in pollutants will vary from state to state due to differing methods of electrical generation. The overall reduction in pollutants from the 20,148 kWh decrease in electricity consumed is dramatic (see Table 4). In comparing Texas and California, you can see the state to state variances in pollutants reduced and the environmental magnitude of the energy savings. For example, a typical automobile puts about 1 pound of CO2 into the air for each mile it is driven. The average American family drives about 21,000 miles per year producing roughly 21,000 pounds of CO2. The reduction in CO2 shown in Table 4 has the effect of reducing the greenhouse gas or CO2 equal to that of taking 1 car off the road in California and 1.5 cars off the road in Texas. In fact, the combined available reduction in carbon dioxide shown in Table 4 would fill more than two Goodyear Blimps!


Annual reduction in pollution from 20,148 kWh decrease in electricity usage Type of Pollution

Texas

Greenhouse Gases (CO2) Volatile Organic Compounds (VOC) Nitrogen Oxides (NOx) Carbon Monoxide (CO) Sulfur Dioxide (SO2)

33,123

23,875

Pounds

1

1

Pounds

52

19

Pounds

9

8

Pounds

69

6

Pounds

Particulates (PM10)

2

0

Pounds

278

1

Milligrams

Toxic Metals Pollution Mercury (Hg)

California Unit of measure

SUMMARY: It is common knowledge within the pump industry that pump efficiency and operation can be improved by reducing recirculation. Our testing has confirmed this point and quantified the magnitude of efficiency gain available on the most common API pump applied in chemical plants and refineries. Additionally, modern polymer composite wear materials such as Greene, Tweed’s W composite wear materials that do not gall or seize are a proven, reliable and practical solution to operate API pumps safely at reduced clearances and for reduced costs. The demonstrated energy savings available by applying polymer composite materials coupled with the positive environmental impact of reduced pollution should help end users identify favorable ROI (Returns On Investment) and install these materials in API pumps as appropriate. CONCLUSION: The initial investment for installing thermoplastic composite materials in properly selected candidate pumps will demonstrate positive economic payback. However, combining economic, environmental, and operational


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gains makes a very compelling case for the proper utilization of these materials on candidate API pumps.

house gases which is equal to removing 1.5 automobiles from the Texas highways for every year of pump operation.

For example, a chemical plant on the gulf coast of Texas with 300 candidate API pumps, (similar to the pump tested) operating under the conditions shown in Table 2 could conservatively achieve $267,300 in annual electricity costs savings. These savings can be realized through the utilization of composite wear material on new pumps, and as replacement parts in repaired pumps.

Companies can realize significant benefits from the proper application of composite wear materials. They are able to reduce cost, increase performance, and show positive environmental impact. The initial investment of upgrading pumps with composite wear materials is insignificant when you realize the potential payback of the investment.

For every new installation, annual savings of $891.00 can be added to the bottom line. In addition, everyone benefits from the reduction in the emission of green-

RUHRPUMPEN, Inc. and Greene, Tweed & Company are working together to bring the best resolutions and benefits to our customers.

REFERENCES AND RESOURCES: 1) United States Department of Energy, Office of Industrial Technologies www.oit.doe.gov/ (a) Industries of the Future www.oit.doe.gov/industries.shtml (b) Best Practices www.oit.doe.gov/bestpractices/

the Hydraulic Institute, Europump, and the US Department of Energy’s Office of Industrial Technologies.

2) Pump Life Cycle Costs, a Guide to LCC Analysis for Pumping Systems, a collaborative effort between

4) Community Office for Resource Efficiency www.aspencore.org/

Greene, Tweed & Co.

RUHRPUMPEN, Inc.

Houston, TX 77073, USA Tel: +1.281.821.2094 Fax: +1.281.821.2696 www.gtweed.com

Tulsa, OK 74145, USA Tel: +1.918.627.8400 www.ruhrpumpen.com

3) Cleaner and GreenerTM, a Program of Leonardo Academy Inc. [email protected]

Statements and recommendations in this publication are based on our experience and knowledge of typical applications of this product and shall not constitute a guarantee of performance nor a modification or alteration of our standard warranty which shall be applicable to such products. Copyright 2003, Greene, Tweed

03/03-GT

TA-US-FH-001