The Basics of Reciprocating vs. Centrifugal Pumps

engineering column PD pumps Understanding the differences between these types of pumps can mean avoiding difficulties and reliability problems.

The demand for the duties that fall within the performance range of reciprocating pumps is rising. Process flows are falling while the pressures required are increasing.

Engineers are generally familiar with operating principles, performance curves and selection criteria for centrifugal pumps, but the training and knowledge around the operating principles of reciprocating pumps is not as common.

Unlike centrifugal pumps, reciprocating pumps have a stronger interaction with the system within which they sit. This is due to the pressure pulsations they generate.

If we think about any linear reciprocating motion of a piston, at some point the velocity of the piston is zero as it changes direction at the top and bottom of its stroke. This means that the pressure pulsations are much larger in a reciprocating machine than in a centrifugal machine.

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Asset Monitoring Improves Reliability & Visibility

Hydro remote condition monitoring A major pipeline transmission company found itself reconsidering the effectiveness of its maintenance strategy. The company faced a challenge: optimizing asset visibility and implementing remote condition monitoring of equipment health while avoiding a high-cost investment and installation disruptions.

This particular pipeline transfers a variety of products, ranging from gasoline to jet fuel, serving customers via pump stations and storage tanks across the United States. For this customer, it is imperative to ensure that pumping assets are efficient, reliable and safely maintained consistently. The pipeline supports the needs of more than 50 cities, thus making the pumping assets critical to the availability and overall operation.

Technology plays a vital role in day-to-day operations in supporting end user activities, ensuring strict safety regulations, optimizing maintenance and providing data on equipment health. In this case, the pipeline company wanted to significantly improve and innovate upon its current maintenance approach in two ways: by monitoring asset visibility in real-time and trending data for their critical pumping equipment.

Read the full article at pumpsandsystems.com.

Hydro’s Perspective On The Global Aftermarket

Written by: Sarah Schroer
Publisher: Pump Engineer Magazine / May, 2014

 

Hydro is a global leader in the pump aftermarket repairs, upgrades and engineering solutions.

Pump companies typically fall into one of two categories: the original equipment manufacturer (OEM) that design, build, and sell pumps; and smaller, local machine repair shops. But Hydro offers the pump industry the best of both worlds. George Harris, one of the original founding engineers and current CEO, explains Hydro’s unique worldwide market position: “We have developed a unique niche where we have the engineering services, the testing capabilities, and the worldwide footprint that the large OEMs have, but we still maintain the exibility and the cost-effectiveness of the smaller companies.”

Harris also emphasizes that engineers are the heart of the company. Nick Dagres, the Vice President of Nuclear Operations in Chicago, notes that “We focus on aftermarket services and support. We implement engineering modifications to improve the performance of pumps that are out in the field.” By offering pump rebuilding, engineering, and upgrading at each service centre, Hydro can more effectively service the special needs and requirements of customers in each region. Staying close to the customer is one of the fundamental tenets of Hydro’s strategy and culture.

 

(Left) Hydro’s long list of services include welding-related repairs, such as performed on this 2 ½” Pacific RL IJ charging pump. (Right) A thorough quality inspection is carried out by Hydro’s detail oriented engineers.

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New Technology Solves Aftermarket Parts Problems

Written by: Dr. T. Ravisundar and Dibu Chowdhury, HydroAire, Inc,. and Heinz P. Bloch, P.E., Process Machinery Consulting
Publisher: Pumps & Systems / March, 2014

 

Industrial equipment users are often confronted with pump parts issues and must make choices. Handling these issues requires making experience-based decisions and prioritizing. How pump hydraulic and wear components in existing inventory are treated is an issue that merits consideration. Plant size, age, past purchasing, maintenance and storage-related practices are among the factors that affect a facility’s status with respect to operational readiness and downtime risk.

As these generally-known facts are applied on a pump component level, it is often determined that the specific pump components in the storehouse may not be the same as the components currently operating in a particular process centrifugal pump. Nor is it always the case that truly optimized components are presently installed. Therefore, the risk of experiencing unforeseen downtime can be reduced by having the right parts on hand. If the parts are truly optimized, installing them at the next opportunity will take the facility beyond being back in business—it will actually take the equipment owners to greater profitability.

To ensure that pumps will perform their intended functions, inventoried or stocked parts should be thoroughly inspected and corrected as needed prior to installation. Incoming inspection is practiced by best-of-class equipment owners and only verified-as-correct parts will be placed in the storehouse. This case study examines a real-life scenario and demonstrates essential precautions that can be taken when procuring pump hydraulic and wear components.

 

A Condensate Pump Repaired & Improved

During a planned outage, a nuclear power plant (NPP) sent a three-stage condensate pump to a highly experienced service center with hydraulic pump design engineers on staff. The NPP provided the hydraulic components, wear rings and bearings from its stock inventory for the pump rebuild project. The hydraulic pump design engineers at the service center performed a thorough inspection of both the disassembled rotor and the parts supplied by the NPP. A visual inspection quickly revealed that the geometry of the replacement impellers did not match the impellers that were removed from the disassembled pump (see Figure 1).

 

Figure 1. Cross-section of a three-stage pump created by an experienced pump repair facility for this three-stage pump. Note semi-open impellers in stages two and three.

 

 

Left: Impeller from disassembled pump
A) Leading edge of vane is straight.
B) Ring turn face to leading edge dist ~ 7/16 inch

Right: Spare impeller supplied from inventory
A) Leading edge of vane edge is curved.
B) Ring turn face to leading edge dist ~ 1inch

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Collaboration and Innovation Result in Efficient Outage

Written by: Paul Gray, Joe Alvey, and Jackson Simmons, Calvert Cliffs Nuclear Power Plant,
Brian Hegarty, Hydro East, Simon Daou, P.E., HydroAire

Publisher: Nuclear News / September, 2013

 

A Hydro East welder repairs the impeller of a Foster Wheeler circulating water pump.

 

 A Hydro East welder repairs the impeller of a Foster Wheeler circulating water pump.

During the 2012 refueling and maintenance outage at Unit 1 of the two-unit Calvert Cliffs nuclear power plant, near Lusby, Md., Hydro East, a subsidiary of Hydro Inc. based in Aston, Pa., supported the on-site overhaul of two large circulating water pumps. Used to supply cooling water to the plant, the Foster Wheeler vertical pumps are 8 ft 3 in. in diameter, 11 ft 5 in. tall, and weigh approximately 25,000 lb.

After the 2012 refueling outage was completed, Calvert Cliffs engineers and Hydro East’s field service team convened to discuss the project, review lessons learned, and generate plans for making the 2013 refueling outage at Unit 2 even more efficient and cost-effective. In preparation, the two groups reviewed the process that had been used in 2012 to remove, rebuild, and reinstall the Unit 1 circulating water pumps, which had been rebuilt on-site. Hydro East’s field service technicians reconditioned the impellers on location, and the Fort Smallwood Fabrication Shop gathered the other parts required to complete the rotating assemblies. The complete disassembly of an entire pump took four 12-hour
shifts, requiring one shift to clean all the reusable parts and another shift to flip and stage the parts. Each shift required a significant number of site resources as well—including security, a crane, and the crane operator—and because other tasks being performed during the outage required the use of some of these same resources, the field service technicians experienced substantial downtime.

To eliminate downtime caused by plant-induced delays—such as having to wait for the crane to become available or for spare parts to be machined—Calvert Cliffs decided to remove the Unit 2 circulating water pump rotating assemblies in one piece and send them to the Hydro East service center to be rebuilt. This plan enabled Calvert Cliffs to achieve cost savings by maximizing the availability of its internal resources and by reducing the number of shifts needed to remove
the pump assemblies from four 12-hour shifts to two. More important, lifting the assemblies in one piece eliminated two high-risk rigging activities for each pump.

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