Piping, pump, compressor & control valve Process Engineering

Right sizing pipes is essential in process design, as it influences fluid velocity, pressure drop, and two-phase flow, while a poorly sized pipe risks disturbances, shutdowns, and higher costs.

Determine the proper pipe size by considering fluid velocity, pressure drop, and flow regime, including two-phase flow, and confirm sizing criteria with colleagues to ensure consistency.

Analyze how higher fluid velocity increases pipe friction, lowers pressure, and may reduce flow. Apply preliminary sizing and system-wide pressure checks to ensure adequate pipe size.

Explore liquid pipe velocity criteria for sizing, including suction versus discharge ranges (2–6 ft/s vs 9–15 ft/s) and how fluids, solids, and standards like API 14E shape conservative limits.

Examine gases and two-phase flow velocity criteria in piping, showing how velocity depends on fluid density and a coefficient C (90–120) from momentum concepts.

Understand how higher flow increases velocity and friction against pipe surfaces, lowering pressure, then use preliminary sizing or system-wide analysis—consider isometrics, fittings, and control valves—to ensure acceptable total pressure drop.

Calculate pressure drop using the Darcy–Weisbach equation, dependent on density, velocity, diameter, and friction factor. Use Reynolds number to select laminar or Colebrook equations and account for pipe roughness.

Master two phase pressure drop calculations with Beggs and Brill correlation for both horizontal and vertical pipes, while understanding uncertainties and alternative methods supported by practical resources and Excel sheets.

Analyze how suction pressure drops and condenser reboiler hydraulics, including NPSH and P1–P2, influence pump operation, flow, and tower performance.

Explore two-phase flow regimes, including wave, stratified, bubble, mist, annulus, and slug flow, and learn how Mandhane and Aziz charts guide pipe sizing.

avoid slug flow in sizing two-phase piping. use pipe supports to handle slug flow and consider riser placement before the control valve to keep upward piping liquid only.

Explore how nominal pipe diameter relates to internal diameter through pipe schedules, detailing schedule 80 and xs versus schedule 40 standards, and considering design pressure, corrosion allowance, and material.

Learn how fittings and valves increase pressure drop via equivalent length, with elbows and valves as examples, underscoring the need for accurate firm sizing calculations.

Calculate pipe size using velocity and pressure drop equations, exploring single and two-phase flow with Excel sizing sheets and online tools like checalc and the Process Engineer Toolbox.

Learn pipe sizing with an Excel workflow that uses flow, density, viscosity, diameter, length, fittings, and roughness to compute velocity, pressure drop, and RoV^2 for single and two-phase flows.

Size a condensate discharge line from 4 to 8 inches to meet a 3.5 m/s velocity and pressure drop for 10 km at 150 m3/h, density 750 kg/m3, viscosity 0.8.

Analyze LPG at pump suction to ensure adequate net positive suction head by evaluating pipe size, fittings, and pressure drop, preventing cavitation and selecting 18 inch line.

Analyze compressor suction pipe sizing for gas at 4000 m3/h, density 9.6, viscosity 0.096, applying velocity criteria and pressure-drop criteria to show 12 inches meets the limits.

Explore a two-phase flow example, analyzing gas-liquid interaction, slug, bubble, and stratified regimes as pipe diameter and orientation—horizontal and vertical—affect velocity, pressure drop, and slug intensity.

Analyze a tower condenser loop in a shell and tube exchanger, balancing driving force vs resistance, and two phase flow to move vapor to the vessel while preserving tower pressure.

Analyze reboiler hydraulics by evaluating driving forces and pressure drops to ensure safe vapor return and liquid recirculation, optimizing pipe sizes and elevations for stable tower operation.

Explains the central role of pumps in plant operation and how sizing, suction systems, and pump response to process requirements, changes, or disturbances shape flow and pressure.

Pumps overcome losses and static head to guarantee a specific flow and pressure through piping, enabling towers, reboilers, and reactors to operate efficiently.

Calculate the available net positive suction head on the suction side, pump differential head, and motor power to drive the pump under operating conditions to ensure correct pump selection.

Assess the available net positive suction head (NPSHA) to prevent cavitation and compare it with the required NPSHR, applying a 10 to 50% margin for safe operation.

Explore how to calculate the available net positive suction head (NPSHA) and how operating pressure, vapor pressure, and static head influence it, with loss-reduction strategies.

Learn about pump suction strainers that keep fluids clean upstream and prevent startup debris plugging. They measure pressure drop by absolute value, NPSH deduction, or length, typically 0.01–0.1 bar.

Explain how a vertical can pump places the impeller at the bottom to lift fluid upward, relaxing the NPSH and enabling a cheap solution despite deep drilling needs.

Explore methods to ensure sufficient NPSH margin, including elevating the vessel, reducing suction losses with strainers, and using vertical can pumps or booster pumps in series.

Demonstrates an NPSH calculation for a 50 m3/hr pump drawing from a 6 barg separator, accounting for elevation, pressure drop, and strainer losses to determine the NPSHA.

Solve an npsh problem by evaluating suction line pressure drop, strainer losses, and vessel elevation to meet a 3.5 npsh plus 0.8 margin, and explore design options to optimize it.

Analyze a condensate tank with a 200 m3/hr pump to determine NPSH margins, calculate suction line size and minimum tank level to ensure 6.6 m available NPSH, guiding pump selection.

Calculate the suction head margin for a condensate pump by setting a 1 m margin to achieve 6.6 m available NPSH through suction line sizing and minimum tank level.

Compute the pump differential head by subtracting suction from discharge pressure and adding static and dynamic losses to meet destination pressure; a flow yields head, while pressure varies with density.

Calculate the required differential head by summing static and dynamic losses and destination pressure. Compare with the pump curve’s rated flow, noting control valve head drop and valve authority.

Calculate pump differential head for a tower feed at 18 bar gauge, including 15 m elevation, 0.3 and 0.6 bar drops, and 200 m piping with elbows, tees, valves.

Compute discharge line pressure drops for three lines, including single and two-phase segments with vaporization, to determine the differential head and assess control valve authority against resistances.

Continue the differential head analysis for a second pump example, calculating flow through a tank with a flow element control valve and 2000 metre line, and add a check valve.

Evaluate suction conditions for a 200 m3/hr condensate pump, focusing on vapor pressure, margins, and the required NPSH of 6.6 m, then calculate suction line size and minimum tank level.

Size the pump motor by calculating hydraulic power from flow, density, and head, then apply pump efficiency to find shaft horsepower and avoid overload at varying flow.

Solve the pump power example by analyzing head, flow, density, and efficiency, showing how density changes motor power under a fixed-speed pump, and how pump curves relate to fixed head.

Determine the operating point by pairing the pump and system curves, and adjust the control valve to shift the system curve through changing dynamic losses.

Explore pump curves, including shut-off head and operating point, how impeller size affects flow and pressure, and design considerations to withstand shut-off pressure while ensuring best efficiency.

Examine how positive displacement pumps show constant flow at varying discharge pressures, with flow slippage reducing output and potentially causing overpressure unless a pressure safety valve protects downstream systems.

Learn how to adjust pump flow to hit the operating point using a control valve or a variable speed drive, and see how these methods affect pump performance curves.

Learn how a discharge control valve with flow or pressure controllers shifts the system curve to meet the required flow, using recycle lines for low-flow operation.

Compare energy-efficient pump control using variable frequency drive motors to valve-based methods, showing how VFD shifts the pump curve to meet flow with less head and power.

Explore how variable speed control lowers pump head and power consumption by reducing impeller speed, and removing control valve pressure drop to achieve significant savings, especially at low flow.

Learn how to configure pumps in series and in parallel, including single pump with a spare for maintenance. Explore the advantages, disadvantages, and appropriate when-to-use scenarios.

Use parallel pump configurations to achieve high or flexible flow when a single pump can't meet demand, ensuring identical pumps and symmetrical piping to balance flow and avoid NPSH/cavitation issues.

Parallel pumps increase flow while head stays the same, but system losses prevent doubling; adjust with pipe sizing or pump controls (control valve or VFD) to shift the system curve.

Two pumps in series boost head and improve net positive suction head (NPSH) for high head or low NPSH conditions, using a booster and a main pump in long pipelines.

Explore two identical pumps in series, where head sums while flow remains constant, compare operating points of each pump against the system curve, and control flow with a valve.

Introduce compressors as devices that transfer gases and raise pressure, highlighting shared principles with pumps and the key differences, and explain how they work.

Compare pumping liquids and compressing gases: gases compress and heat under pressure, needing cooling and separation stages; liquids stay nearly constant; compressors are more complex and costly than pumps.

Identify two main compressor types—dynamic and positive displacement—explaining centrifugal and axial dynamic compressors, and reciprocating and rotary positive displacement variants; highlight selection criteria such as flow, pressure, cost, and maintenance.

Choose dynamic or positive displacement compressors by considering capacity, pressure ratio, and discharge temperature; reciprocating units provide high pressure with limited flow, while dynamic types handle high flow.

Dynamic compressors offer high capacity; axial compressors achieve higher capacity and efficiency at high flow and pressure ratios but require complex maintenance and higher costs, making centrifugal compressors more common.

Compare positive displacement compressors, including reciprocating pistons and rotary vanes, highlighting direct compression, pressure ratios, efficiency, and maintenance, plus pulsation dampeners for reciprocating units.

Use a multi-stage compressor with intercoolers and a separator to keep discharge temperatures below 180 degree Celsius while reaching 15 bar gauge, and employ suction scrubber and sloped piping.

Determine the head–pressure relation by selecting adiabatic or polytropic compressor behavior; adiabatic uses gamma and no heat exchange, while polytropic includes heat transfer with n linked to gamma via η.

Calculate the compressor head from the derived equation using Z, R, suction temperature, and polytropic or adiabatic constants, then compare with compressor curves at the desired flow.

Explore how inlet temperature and gas molecular weight affect compressor head and flow in centrifugal and positive displacement types, and note API 617 head-vs-flow and discharge pressure-vs-flow curves.

Explore adiabatic (isentropic) efficiency in compressors, highlighting ideal vs actual work, the impact on discharge temperature, power needs, and how inter-stage cooling and entropy paths affect reciprocating and centrifugal compressors.

Explain why adiabatic efficiency misleads for centrifugal compressors due to gas slippage, and present polytropic efficiency as the integral measure predicting outlet temperature and overall performance.

Explore surge and stone wall boundaries in dynamic centrifugal and axial compressors. Surge occurs when head cannot meet discharge pressure, reducing flow; stone wall causes choked flow at sonic velocity.

Analyze how system resistance shapes compressor curve by adding static pressure to dynamic resistance, producing a system curve that intersects compressor curve to yield operating point and discharge pressure.

Learn how to protect compressors from surge by maintaining flow above the surge limit with a 10% margin and using an anti-surge system that recycles gas to suction.

An anti-surge system uses a fast-opening valve and dynamic simulation to prevent surge, with bypass lines for startup or unforeseen gas changes, cooling of recycled gas and settling-out pressure considerations.

Size the anti-surge take-off point and recycle line to control discharge and suction volumes, ensuring rapid overpressure sensing and timely surge protection near the compressor discharge.

Explore dynamic compressor control methods for centrifugal and axial machines, including discharge and suction throttling, inlet guide vane changes, and variable speed drives that regulate flow and pressure.

Discharge throttling controls a discharge line valve via a pressure or flow signal, adjusting opening and shifting system curve. Common for pumps, it risks compressor surge and power loss.

Suction throttling uses a control valve to reduce suction flow and density, maintaining constant discharge pressure. It lowers power but can cause surge and safety risks with flammable gases.

Install inlet guide vanes before the compressor impeller to adjust flow by vane angle, offering suction-throttling-like control with lower power use but higher initial costs, maintenance, and frequent adjustment.

Learn how variable speed drivers control centrifugal compressor speed to meet the system curve and provide the desired pressure or flow, while lowering power use.

Discover how reciprocating compressors control capacity through spillback to the suction line, step control with discrete 25%, 50%, or 75% flow, and selective variable-speed drives in turbine-driven systems.

Explore spill back and recycle control for positive displacement compressors, balancing discharge flow by recycling excess to the suction while managing temperature and efficiency with a step controller.

Explore how reciprocating compressor cylinders operate, comparing single acting and double acting designs, and learn unloading and clearance pocket control to adjust capacity, throughput, and efficiency.

Step control for reciprocating compressors uses 0–100% capacity with 3-step or 5-step schemes, employing multiple valves, suction and clearance pocket controls, and spill back with unloading for intermediate percentages.

Explore variable speed control for reciprocating compressors driven by steam turbines to reduce power use, manage capacity, with spillback or unloading when needed, and vendor-checked critical shaft speeds, 25–60% limits.

Simulate compressor performance in Aspen HYSYS using data from Excel, then analyze operating points, compressor curves, and the impact of single or two-stage configurations on pressure, temperature, power, and efficiency.

Plot compressor curves from five data sets at different speeds to determine operating points, visualizing shifts between the search and stonewall regions under a variable speed drive.

Explore how varying gas molecular weight and composition affects centrifugal compressor performance, comparing pressures, temperatures, head, power, and polytropic efficiency across different operating cases.

Explores how changing inlet pressure, flow, and compressor speed impacts head, pressure, temperature, efficiency, surge and stonewall behavior, highlighting the benefits of variable speed drives for power savings.

Explore how varying compressor inlet temperature influences outlet pressure, head, power, and polytropic efficiency, and how speed and fixed conditions shift surge risk and overall performance.

Explore how to perform compressor surge analysis using a dynamic search tool in Aspen HYSYS, including anti-surge protection, flow sheet setup, valve sizing, bypass strategies, and emergency shutdown scenarios.

Simulate compressor performance in Aspen HYSYS using Excel data and curves, assess surge, operating point, and adiabatic vs polytropic efficiencies for single and two-stage setups with suction cooler.

Explore designing a two-stage centrifugal compressor, ensuring equal load distribution across stages, controlling outlet temperatures below 150 C, and using intercooling and scrubbers to maintain efficiency as pressure rises.

Control valves act as final control elements to adjust level and temperature by regulating flow; they shape system hydraulics and enable back pressure control in reactors and processes.

The control valve adjusts opening to vary flow area, creating a vena contracta; velocity rises and pressure drops per Bernoulli, with cavitation or flashing possible.

Cavitation forms vapor bubbles in the vena contracta when pressure drops below vapor pressure, causing implosion and valve damage. Mitigate by managing downstream pressure or using low recovery valves.

Explore flashing as a vapor-liquid phenomenon in valves, distinct from cavitation, where outlet vapors and droplets erode the plug and seat. Minimize impact through material choice and geometry optimization.

Cv, the valve flow coefficient, equals gallons per minute at 1 psi drop for a fully open valve (60 f). Cv varies with opening and fluid characteristics.

Calculate valve Cv with phase- and fluid-dependent equations, including steam and non-ideal gases. Cv is proportional to flow and inversely to pressure drop; manufacturers provide data and openings for sizing.

Explore how choked flow limits valve performance, creating plateau as pressure drop rises, when vena contracta pressure falls below vapor pressure or gas reaches sonic velocity, cavitation and flashing occur.

Explore how a control valve’s inherent curve shows CV versus opening under a constant pressure drop, and compare linear, equal percentage, and quick opening behaviors that predict installed valve performance.

Define control valve authority as the fraction of the total system pressure drop that occurs across the valve. Upstream and downstream losses make authority less than one.

Understand how actual pressure drop in the control valve relates to the pump curve and system losses to determine valve authority across flow.

See how actual valve pressure drops, like 0.8 psi and 0.6 psi, alter installed characteristics and yield smaller flow increases (8.9 gpm to 13.1 gpm) than inherent equal percent curves.

Analyze how system pressure losses shape valve behavior, from equal percentage to linear and quick opening valves, and assess control valve authority for improved controllability and pump power balance.

Explain plug geometry creating valve characteristics: quick opening, equal percentage, and linear. Describe curvature governing flow, with equal percentage starting small and rising, while linear remains nearly constant.

Explore how butterfly valves compare with globe valves for control services, highlighting cheaper cost, lower pressure drop, higher cv at the same size, and limitations in precise control.

Understand why butterfly valves exhibit less precise control due to their inherent curve, and how installation yields linear or quick opening behavior influenced by dynamic pressure drop and system resistance.

Size the control valve by evaluating all expected process scenarios, accounting for system losses and static elevations to determine the true pressure drop and Cv requirements.

Calculate the control valve pressure drop by subtracting outlet pressure from inlet pressure, accounting for vessel and tower pressures, piping resistances, flow element losses, static elevation, and density differences.

Determine controlling cases for a control valve by evaluating min, normal, and max scenarios, accounting for flow, density, pressure drop, cv, and design margins.

Assess pressure drops from pump discharge through a control valve across three cases, considering two-phase flow, turndown, and design margins to size the CV and piping.

Analyze a tower overhead control valve scheme with backpressure control, air cooler, and reflux loop; compare three cases to determine valve type and sizing using CV and pressure drop.

The supplier calculates the maximum CV and selects a valve size with a rated CV just above it from catalog, ensuring opening stays within max, normal, and min CV ranges.

Evaluate valve sizing impact on performance and control. Oversized valves waste capacity and hamper precision; undersized valves cannot meet required cv, risking on-off behavior and shutdown.