Engineering a Long-Term Solution

Figure 1. The pump as received

Many pumps in operation today were designed and manufactured decades ago. As plants require increased capacity, pump systems are expected to meet these higher process flow demands. Without an impeller rerate or change in speed, this increased capacity can be achieved in one of two ways. The individual pumps can supply more flow to the system, resulting in operation out on the pump curve. Alternatively, capacity can be increased by operating more pumps in parallel; in this case operation is pushed back on the curve, as operating another pump in parallel requires less flow from each individual pump to meet total system demand.

Either operational change results in a move away from the pump best efficiency point (BEP). As a result, the original designs and hydraulic characteristics no longer effectively meet plant requirements and detrimental effects from hydraulic instability can occur.

By way of example, this article will discuss a fertilizer plant in the Gulf of Mexico that had a boiler feedwater pump unit that was experiencing performance problems after a significant plant expansion project. Unfortunately, it was not the first time this particular unit had experienced a loss of capacity; the pump had been in operation only 18 months prior to the current issue.

 

Root Cause Analysis Uncovers Casting Defects

Efficiency and reliability are at the forefront of a successful pumping system. As such, unplanned outages can be a detrimental disturbance to the overall operation. In this case, the end user’s high pressure multistage  BB5 barrel pump was experiencing severe vibration, unstable performance, and failure in the field leading to unit shutdown.

This particular unit, used in boiler feedwater operations, is critical to the plant’s uptime and throughput. Furthermore, continued failures can cause growing costs due to inevitable maintenance and repairs, often overlooking a long term solution. With each unplanned outage, the plant could face a significant loss in capital.

Previously, the pump had been running for six months before experiencing catastrophic failure, requiring a shutdown and removal for further analysis. Initially, the unit’s damaged components were repaired by welding, and the volute was reassembled and installed for use. Upon its installation, the power plant placed the unit back into service but encountered a second emergency shutdown after two months in operation.

Root Cause Analysis Uncovers Casting Defects in Critical Boiler Feedwater Unit from Hydro, Inc. on Vimeo.

Read the full article at pumpsandsystems.com

The Basics of Reciprocating vs. Centrifugal Pumps

Image 1. A reciprocating pump’s fixed volume. Flow is determined by stroke, area and speed. (Images courtesy of Hydro)

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.

Read the full column at pumpsandsystems.com

Increasing MTBR Under Emergency Conditions

increasing mtbr under emergency conidtionsAs the nuclear industry continues to adapt to new requirements under the Nuclear Promise, it is of key importance for utilities to strengthen existing safety protocols and execute efficiency improvements in day-to-day operations and maintenance to optimize overall costs.

One such nuclear plant found themselves  struggling in regards to a planned outage of a vertical service water pump, providing cooling water to safety-related heat exchangers in the power generation process. In this case, the operating pump was actively exhibiting performance issues and was reaching the end of its lifecycle, requiring their reserve unit be placed into service under expedited conditions.

The principle goal for the plant was increasing Mean Time Before Repair (MTBR) of their pump system to optimize efficiency and reduce costs. Unfortunately, upon initial review of the reserve unit, it was identified that it had a history of poor performance issues under previous use.

Read the full article at nuclearplantjournal.com on pages 40-42.

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.