AFT Application Topics

Accumulators

2017-08-28T14:43:11-06:00

Gas accumulators are used as surge suppression devices during waterhammer events. For new systems, gas accumulators must be sized for volume and located properly. AFT Impulse can model gas accumulators and assist engineers with accumulator sizing and finding the best location.

Gas accumulators can have a bladder separator, as well as a differential orifice plate. Both can be modeled in AFT Impulse.

Resources

Product Tip – Making a Difference, No Power Needed

Product Tip – Using Liquid Accumulators in AFT Impulse

ANSI/HI 12.1-12.6 Slurry Pump De-Rating

2020-11-30T13:53:06-07:00

American National Standards Institute (ANSI)/Hydraulic Institute (HI) - Slurry Pump De-Rating - ANSI/HI 12.1-12.6: Rotodynamic (centrifugal) Slurry Pumps. Slurry pumps convey the pumping of solid particles which degrades the pump performance (pump de-rating).

AFT Fathom and the AFT Fathom Settling Slurry Add-on Module

AFT Impulse and the AFT Impulse Settling Slurry Add-on Module

ANSI/HI 9.6.7 Pump Viscosity Corrections

2020-11-30T13:49:30-07:00

American National Standards Institute (ANSI)/Hydraulic Institute (HI) - Pump Viscosity Corrections - ANSI/HI 9.6.7: Effects of Liquid Viscosity on Rotodynamic (centrifugal and vertical) Pump Performance. Important for many types of applications including crude oil pumps.

ANSI/HI 9.8 Pump Submergence

2020-11-06T15:20:08-07:00

American National Standards Institute (ANSI)/Hydraulic Institute (HI) - Pump Submergence. ANSI/HI 9.8: Rotodynamic Pumps for Pump Intake Design Submergence relates to having adequate supply liquid depth to avoid vortices from forming and reaching the pump.

API 674 Pump Pulsation Pressures

2020-11-30T14:07:55-07:00

American Petroleum Institute (API) Pump Pulsation Pressures - API 674: Petroleum, petrochemical and natural gas industries

Covers the minimum requirements for reciprocating positive displacement pumps for use in service in the petroleum, chemical, and gas industries. Both direct-acting and power-frame types are included.
Defines topics such as maximum and minimum speeds, pulsation and vibration control requirements, and testing requirements.

AFT Impulse

API/ASME/ISO Gas Relief System Piping

2020-11-30T14:00:50-07:00

American Petroleum Institute (API), American Society of Mechanical Engineers (ASME) and International Organization for Standardization (ISO) - Gas Relief System Piping

API RP520: Design and Installation of Pressure Relieving Systems in Refineries (recommended practice)
ASME Boiler and Pressure Vessel Code, Sec. VIII-Non-Mandatory Appendix M
ISO 4126-9 Safety Devices for Protection Against Excessive Pressure -Mandatory.
All three standards have different requirements for the inlet piping to the relief valve and the discharge piping. They also can vary depending on the operating conditions, the gas involved, and the type of relief valve used.

AFT Arrow

ASME B31.3 Surge Forces

2020-11-30T14:06:37-07:00

American Society of Mechanical Engineers (ASME) Surge Forces - B31.3: Process Piping –

Contains requirements for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals. It covers materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping.
This Code applies to piping for all fluids including:
(1) raw, intermediate, and finished chemicals;
(2) petroleum products;
(3) gas, steam, air and water;
(4) fluidized solids;
(5) refrigerants; and
(6) cryogenic fluids.

AFT Impulse

ASME B31.4 Surge Analysis and Allowable Pressure

2020-11-30T14:04:59-07:00

American Society of Mechanical Engineers (ASME) Surge Analysis and Allowable Pressure - B31.4: Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids

Prescribes requirements for the design, materials, construction, assembly, inspection, testing, operation, and maintenance of liquid pipeline systems between production fields or facilities, tank farms, above- or belowground storage facilities, natural gas processing plants, refineries, pump stations, ammonia plants, terminals (marine, rail, and truck), and other delivery and receiving points, as well as pipelines transporting liquids within pump stations, tank farms, and terminals associated with liquid pipeline systems.
Also prescribes requirements for the design, materials, construction, assembly, inspection, testing, operation, and maintenance of piping transporting aqueous slurries of nonhazardous materials such as coal, mineral ores, concentrates, and other solid materials, between a slurry processing plant or terminal and a receiving plant or terminal.

AFT Impulse

ASTM C1055 Surface Temperature Allowables

2020-11-30T14:03:24-07:00

American Society for Testing and Materials (ASTM) - Surface Temperature Allowables - ASTM C1055: Standard Guide for Heated System Surface Conditions that Produce Contact Burn Injuries.

AFT Arrow

ASTM Surface Temperature Allowables

2020-11-06T15:04:31-07:00

AFT Fathom or AFT Arrow output will help engineers identify American Society for Testing and Materials (ASTM) - Surface Temperature Allowables. The ASTM C1055: Standard Guide for Heated System Surface Conditions that Produce Contact Burn Injuries.

Best Efficiency Point – BEP

2017-08-28T14:44:57-06:00

Every pump has an ideal range of operation where the pump is most efficient. The peak of the efficiency curve is known as the best efficiency point. AFT Fathom models pump curves with efficiency data and will determine the margin between the simulated operation of the pump and the actual best efficiency point (BEP). The HI Standard ANSI/HI 9.6.3 specifies allowable ranges of operation. Operating closer to a BEP increases reliability and reduces maintenance costs.

Resources

Product tip – What About Viscosity Corrections?

Standard – ANSI/HI 9.6.3 Rotodynamic (Centrifugal and Vertical) Pumps – Guideline for Allowable Operating Region

Cavitation

2017-08-28T14:46:24-06:00

Cavitation is a hydraulic phenomenon that occurs when the system fluid reaches vapor pressure, causing the fluid to flash into vapor. AFT Fathom can alert users to steady-state cavitation, which is persistent and can cause rapid degradation of pipe walls. Transient cavitation can be modeled with AFT Impulse, and is commonly referred to as liquid column separation.

AFT Impulse offers two transient cavitation models: The Discrete Vapor Cavity Model and the Discrete Gas Cavity Model.

Centrifugal Pumps

2018-05-17T17:53:00-06:00

Centrifugal pumps are the most common type of pump used in piping systems. Basically, anything that is modeled with a pump curve is centrifugal. These pumps use an impeller to impart pressure on fluid flowing through them.

AFT software allows users to model centrifugal pumps, fans, and compressors by inputting the respective curve. Based on the system hydraulics, the location of the curve on which the pump, fan, or compressor will operate is determined.

These calculations allow engineers to assess the suitability of a centrifugal pump, fan, or compressor by reporting a wide range of parameters including head rise, flow rate, NPSHA (for pumps), and speed, as well as efficiency, BEP, and NPSHR (for pumps) with additional input.

AFT Arrow used centrifugal fans and compressors
AFT Fathom & AFT Impulse use centrifugal pumps

In AFT Fathom, The Pump Properties window provides clear distinction between rotodynamic (or centrifugal) and positive displacement pumps. Note that PD pump models can calculate acceleration head in the suction line and AFT can also model multistage pumps with interstage takeoff flows.

The Hydraulic Institute wrote an article highlighting centrifugal pumps: https://www.pumpsandsystems.com/how-centrifugal-pumps-work

Codes and Standards

2020-11-05T22:10:23-07:00

Industry Standards are a set of criteria within an industry relating to the standard functioning and carrying out of operations in their respective fields of production. In other words, it is the generally accepted requirements followed by the members of an industry.
Many prospects and customers are not aware of these Standards and the importance for the security of the plant or pipeline to include them in their design.
Not all countries use the same standards but most of the standards use similar criteria.
AFT strives to create awareness of these standards and how AFT products can help engineers meet these requirements.

AFT Fathom

API and HI Pump Preferred Operating Range
NFPA Fire System Calculations
ASTM Surface Temperature Allowables
ANSI/HI Pump Submergence
ANSI/HI Pump Viscosity Corrections
ANSI/HI Slurry Pump De-Rating
ASME/ISO Energy Standards

AFT Arrow

NFPA Dust Collection
ASME, API and ISO Gas Relief System Piping
ASTM Surface Temperature Allowables

AFT Impulse

ASME Surge Analysis and Allowable Pressure
ASME Surge Forces
API Pump Pulsation Pressures
API: Allowable Compressor Pulsation
ANSI/HI Pump Viscosity Corrections
ANSI/HI Slurry Pump De-Rating

Compressor Modeling

2017-08-28T14:48:37-06:00

It is important to properly size and characterize compressors. AFT Arrow allows engineers to model centrifugal and reciprocating compressors. Centrifugal compressors can be modeled by entering a performance curve. Reciprocating compressors can be modeled with a fixed flow rate through the compressor. The heat of compression can also be modeled in AFT Arrow for both compressor types, quantifying the temperature rise of the fluid.

Resources

Product tip – Feeling Compressed? Don’t Forget Your Thermodynamics

Condensing Gas Flow in Pipes

2017-08-28T14:50:14-06:00

Compressible flow systems may be subject to condensation which is often undesirable for system operation. It is important to ensure system operation above the saturation line to avoid this operation condition. AFT Arrow has two fluid property sets available, one for purchase, in the forms of the 1997 ASME Steam Tables and the Chempak Property Database. Both data sets include information on fluid saturation lines, which allows AFT Arrow to notify the user when they have moved to a point of operation that would result in condensation. While this notification is crucial, AFT Arrow does not model two phase flow and the results after the point of condensation will likely be inaccurate.

Discharge Coefficients

2017-08-28T14:51:31-06:00

Discharge coefficients are constants that can be used to determine the pressure drop across fittings and devices. AFT Fathom, AFT Arrow and AFT Impulse allow users to specify the discharge coefficient for various types of junctions and the pressure drop will be automatically calculated.

Dust Collection

2017-08-28T14:55:10-06:00

Dust collection systems must be properly designed to ensure that all dust collected is adequately removed. If velocities in dust collection systems are not high enough, dust may aggregate and can ignite. AFT Arrow can model dust collection systems and allow engineers to determine if the local velocities are high enough to safely remove the dust.

Using various pipe friction models, AFT Arrow allows users to be compliant with NFPA regulations regarding dust collection systems. Strong correlation to field data has been found to exist using this feature in a published case study (see Case Study 1).

Resources

Case study 1 – AFT Arrow Results Support Manufacturing Facility Data – Dust Collection Systems Rebalanced

Energy Costs in Rotating and Reciprocating Equipment

2017-08-28T14:58:30-06:00

Motor energy used to drive rotating and reciprocating equipment like pumps, fans and compressors, is one of the largest consumers of electricity in industrial applications. To reduce life cycle cost and make more efficient use of energy, the energy costs associated with pumps, fans and compressors should be well understood. AFT Fathom and AFT Arrow can calculate energy costs for pumps, fans and compressors. The user needs to supply electricity costs and lifetime of the system. Additional cost information such as interest rates and inflation can also be input to quantify the impact on net present value.

Equivalent Length

2017-08-28T14:59:50-06:00

Methods for calculating losses for valves and fittings vary across all industries. One method is to convert the losses to an equivalent length of pipe. AFT Fathom has the option to use equivalent length. AFT Fathom also ensures compliance with NFPA 13, and activating the extended option equivalent length feature enables users to specify equivalent lengths that are used with the NFPA 13 standard.

Resources

Product Tip – Using Equivalent Lengths in AFT Fathom