Mitigating Practical Issues with Pumps, Compressors, and Turbines

When completing designs for heavy equipment applications, engineers assess the client’s various needs to ensure all the project requirements are met. Occasionally, some parameters must be modified based on the advice of suppliers and manufacturers. It is therefore important to have a thorough understanding of these assets to ensure that all necessary modifications have appropriate alternative solutions. Naitik Mehta, a Rotating Equipment Engineer at Bechtel, spoke to Pump Engineer regarding his experiences working with design plans for pumps, compressors, and turbines, and the solutions he requires to ensure the plant runs efficiently.

By Shopia Ketheeswararajah

A Day in the Life

In his current role, Naitik Mehta creates and executes design plans for heavy machinery. “When I was pursuing my Masters’ Degree at Texas A&M University, my research was geared towards rotating equipment and rotordynamics. After graduating in 2012, I began working at Bechtel and a lot of my experience aligns with working closely on the pumps, turbines, and compressors designs,” he said.

Depending on the phase of the project, Mehta reviews design documents from equipment manufacturers to ensure the project requirements are being followed. “We must always make sure that the equipment fits properly within the process parameters and ensure that the safety and integrity of the equipment are met. By coordinating between various engineering disciplines, we can tie together any loose ends seamlessly.”

When a project is in its initial phase, FEED (Front End Engineering Design) operations begin. This is a basic procedure for understanding the premise of the project. “Once I know what process parameters that the machine has to operate within, my team and I begin creating the design plan.”

Once the design phase commences, suppliers are brought in to ensure that the equipment is sized correctly. A bid form, which is a document that details all the requirements that must be met for a successful operation, is then used.

“Once the supplier provides us with quotes, it is reviewed to finalize all the technical details of the proposal,” Mehta added. Various engineering disciplines are required to coordinate with one another to clarify the bid evaluation. After this step is completed, Mehta proposes the evaluation to a procurement team. “The bid form would then be approved and an order for the equipment is placed.”

This is when the EPC phase begins. “We ensure all the fluid compositions are correct, if there are any changes, we go back to the supplier and fine-tune the equipment,” he said. The engineering phase involves several critical meetings, from HAZOP reviews and 3D models to alarms and trip reviews. In the engineering phase, the vendor starts designing the application and submits the system review documentation. “This includes a systematic review of piping and instrumentation diagrams, general arrangement drawings, control system narratives, cause and effect diagrams, equipment data sheets, and performance maps”, he mentioned. Upon review, comments are made and recorded to make sure the equipment is in line with the rest of the project, its product specifications, industry standards and safety regulations. “We make sure everything looks good and works great,” he stated.

The Big Three: Pumps, Compressors, and Turbines

When working with any complex equipment, Mehta’s role remains the same. “The sizing, selection, design review, test witnessing, construction, and start-up support are similar. There are challenges that show up on a day-to-day basis, this is because the system is often complex.” When determining the best turbine or compressor for an application, it is important to remember that when purchasing a compressor the end user is investing in an entire package. “The compressor package includes the compressor, the driver, auxiliary and piping systems.”

When speaking of the relationship between the big three, Mehta shared that the major difference is the fluid that is used when these components are in operation. With pumps, the fluids that are most often used are non-compressible. Turbines and compressors on the other hand, almost always use compressible fluids or gases.

“There are a lot of aerodynamic properties that are associated with compressible fluids, the gas dynamic and rotordynamic issues are present because of the rotating speeds in the turbines and compressors that are in operation,” he added.

The parameters that need to be considered, align with the flow, the inlet and outlet pressures, temperatures, the gas molecular weight of the media that will be run through the application, and the material used for the component.

“Hydrogen sulfide has different material requirements. The same thing could be said for hydrogen or carbon dioxide. The gas that is being run through the special component can demand different metallurgical suggestions,” Mehta stated. There are application-specific details that must be reviewed.

“In the case of pumps, they are often times operating  at driver speed. For example, when coupled with motor operating at a line frequency of 60 Hz, the speed is either 1,800 or 3,600 rpm. It is rare to see a pump working at higher speed.” In terms of designing pumps, factors such as differential head, system curves, NPSH, and the margins between the shutoff and operating head must be considered. This, however, is not the case with compressors or turbines. Often, these are operated at high speeds. “For this reason, it is common to see a lot of rotordynamic analysis when it comes to turbine and compressors.” Compressors and turbines generally have more complexities than pumps.

Working Through Maintenance Challenges

One of the most challenging parts of Mehta’s line of work is to make the correct decision when it is time to evaluate deviations. “The deviations and clarifications that the vendors send back usually do not align with the industry standards and project specifications; the supplier might not be in compliance with every requirement and the deviation requests often acknowledge what was asked of the manufacturers. Since they cannot accommodate the requirement for a specific reason, the suppliers ensure the engineers have alternate solutions,” he said.

Once these alternative solutions and deviations are communicated, it is up to Mehta and his team to determine whether the suggestions would be feasible by understanding the impact the deviation would create if it were to be accepted.

“Another thing about my work that I find a little challenging would be reviewing the maintenance requirements for the equipment,” added Mehta. The maintenance requirements are reviewed during the equipment’s manufacturing phase when there is no operating information available. “We ask for the maintenance schedule and then compare that to previous designs to ensure accuracy. Whenever possible, we seek input from the client’s maintenance and operations team. Typically, the maintenance schedule comes from the manufacturers, who determine how often maintenance should occur,” he said. Most of the maintenance that occurs is preventative; this includes oil changes, filter cleaning, and making sure the equipment is operating within the design limits.

“When looking at the maintenance needed for a compressor, for example, the most common practices include checking oil filters and strainers. Upstream equipment also need to be cleaned. The compressors are shut off from production periodically, so operators can open them up and check on components such as bearings. This is to ensure there is no corrosion or erosion.  A lot of this information is available through machine monitoring systems which often predict failures early enough for the operators to take preventive actions.”

“Turbines are a little similar in this case, these components also have quite a bit of ongoing maintenance, especially when steam or water is involved; the blades in the turbine need to be well tended to for optimal performance.”

Practical Issues and Test Witnessing

Usually with EPC companies, the operation experience is imminent. “Our operating experience is limited and mostly is in start-up or commissioning phases. We have a list of lessons learned that we apply across the board. Whenever there are issues at the job site, we do everything in our power to make sure it is not repeated.” It is therefore important to have the client’s input when it comes to the operating experience and the use of his expertise when product specifications are being drafted. “We include any requirements that we may feel is important, this way the clients do not have to run the repeating previous mistakes.”

For Mehta, the best part of his role is being able to witness test runs of the designs that he has created. “When reviewing the design documents, I have to make sure the operability and maintainability are fully functional,” he said. When the equipment manufacturing begins,  the job site visits to complete testing are performed. Engineers often ask for permission to observe. “The testing typically determines whether or not the component is functional and if it follows  project specifications and industry standards. One of the most exciting parts about test witnessing is to see if the design you have been working on is the perfect fit, it is most exciting when it actually works,” he said.

Looking Ahead

When looking ahead, Mehta believes that the global push toward reducing the carbon footprint within the industry will become more prevalent. “The resources are available, we have solar energy, wind energy, hydropower, and so on. Of course, we can use these alternative resources, but it would be difficult to completely rely on only wind or solar power,” he said. He argues that with the constant fluctuation in weather, it becomes increasingly difficult to provide energy, irrespective of what the weather condition is outside. Alternative fuel sources solutions such as hydrogen are still not mature enough to replace hydrocarbons completely. “I think we will still continue with the hydrocarbon industry, but we will also take more part in carbon reduction activities, such as carbon capture and sequestration and an increase in the use of hydrogen,” he said.

In addition to this, Mehta provides some insight into the new generation of engineers in the industry. “There is a lot of fear around new engineers entering the oil &  gas industry. The cyclic nature of the business has brought on a little bit of misinformation on the industry; that we are dying out and becoming more reliant on renewable resources, which we are beginning to incorporate, but the renewable resources will not entirely eradicate the oil & gas industry.” Mehta advises new engineers that are grappling with this idea that “the energy industry is not dying; it is not going anywhere.”

Final Thoughts

The process of creating designs for heavy equipment applications entails multiple stages of planning, evaluation, and approval. Several requirements need to be fulfilled and carefully considered when preparing for the beginning stages of the project’s development. It is essential engineers have a clear understanding of the complex machinery to successfully provide alternative solutions for clients, while keeping the integrity and safety of the equipment.

About the Expert

Naitik J. Mehta, a Senior Rotating Equipment Engineer at Bechtel Energy in Houston, TX, has over 11 years of experience working with various Rotating Machinery and Packed Equipment. Naitik holds a Master of Science in Mechanical Engineering from the Texas A&M University and is a Registered P.E. in the states of Texas and Louisiana.

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Shopia Ketheeswararajah is a feature editor contributing to Pump Engineer, Stainless steel World Americas, Hose and Coupling World, and other related print & online media.