Determining Liquid Capacity 4 th Annual Pipeline Knowledge Retention Chris Sonneborn November 7, 2013
Outline What is important? Liquid Properties Thermal Conditions Hydraulic Gradient Flow Regime in Liquids Pump Analysis Batching Drag Reduction Surge Analysis a.k.a. Waterhammer 2
What is important? Pipe geometry Length, diameter, roughness Maximum Operating Pressure (MOP) Elevation Fluid properties Density / Specific Gravity Viscosity Bulk modulus Specific Heat Pump characteristics Head versus Flow and Efficiencies Available horsepower NPSH Thermal Conditions Thermal conductivity pipe and soil Ground temperature Seasonal variations Vapor Pressure versus Temperature Reference conditions 3
Liquid Properties Vapor Pressure versus Temperature Make sure we are moving liquids! Specific Gravity / Density / API Gravity Kinematic Viscosity (centistokes) versus Temperature Kinematic Viscosity = Absolute Viscosity / Density Bulk modulus Speed of sound calculations Specific Heat Energy required to alter fluid temperature Reference Conditions 60 F and 0 psig (or Vapor Pressure) What is a standard barrel? Special fluid characteristics decomposition risks, et cetera 4
Thermal Conditions Frictional heat may be significant with some fluids Burial depth and soil / pipe thermal conductivity important Run conservative isothermal scenarios, if conditions are unknown and cannot be estimated accurately SCAN sites US Government soil temperature monitoring sites ASHRAE soil conductivity data 5
Hydraulic Gradient Pipeline Elevation and Fluid Vapor Pressure Provides lower pressure limit; be sure to allow adequate margin Maximum Operating Pressure upper pressure limit Pressure/Head loss Frictional losses Elevation losses 6
Flow Regime in Liquids Hydraulic losses impacted by flow regime Reynolds number (Re) dimensionless parameter providing a ratio of inertial forces to viscous forces. For fully developed flow, approximate regimes are bounded by: Laminar flow Re <= 2,300 Critical flow 2,300 < Re < 4,100 Turbulent flow Re > 4,100 Be aware of Re, particularly with very viscous fluids!! 7
Pump Analysis Centrifugal, Reciprocating, and Positive Displacement Fixed and variable speed Centrifugal Pump Curves Head, Horsepower, and Efficiency versus Flow Min/max speed NPSH Nominal pump suction head 8
Batching Batching Flowing different products on the same pipeline Allows one pipe to serve multiple needs. Different fluids impact the system hydraulic gradient Interface / Slop Mixing will occur where different products contact one another, usually resulting in degradation of one or both product qualities Pump head requirements When a lower density product follows behind a higher density product, pump head requirements may increase until the higher density/viscosity product is cleared 9
Drag Reduction Drag Reducing Agent DRA Long polymers introduced into the flow to reduce pipe friction losses When do you use DRA? Improve batching performance Debottleneck pipeline segment Reduce pumping stations Characteristics Lose effectiveness over distance Destroyed by centrifugal pumps Most effective in turbulent flow conditions 10
Surge Analysis - Waterhammer Surge Pressure Pressure produced by a change in velocity of the moving stream that results from shutting down a pump station or pumping unit, closure of a valve, or any other blockage of the moving stream. 195.406 Maximum operating pressure (b) No operator may permit the pressure in a pipeline during surges or other variations from normal operations to exceed 110 percent of the operating pressure limit established under paragraph (a) of this section. Each operator must provide adequate controls and protective equipment to control the pressure within this limit. Joukowsky equation (1898) P = ρ c v Must consider whole system!! Pump shutdown, control points, fluid compressibility, Operator response, surge/breakout tanks, control valve response time, et cetera 11
The End Questions??? 12