Inter-tank Transfer: Plant Operations

Inter-tank Transfer Overview

• Inter-tank transfer involves the transfer of materials between storage tanks in a process plant or tank farm facility
• The lesson covers shift teams, line tracing and symbols, the process plant, storage tanks, piping, hoses, transfer operations, and hazards

Shift Teams

• Process plants and tank farms operate using shift teams.
• An outgoing shift team will hand over to incoming shift teams, ensuring continuous around-the-clock operation
• The shift superintendent manages the plant, overseeing operational safety to meet production targets
• Safety briefings occur at each shift's start to ensure safety and efficient operation
• Shift team members include field technicians and console operators

Field Technician

• Field technicians work in the outside area, performing routine checks and area rounds using checklists
• Their tasks include performing start-up and shut-down procedures alongside product sampling: collecting samples for the lab
• Material handling includes transferring materials between process units, and loading/unloading feed and finished products
• Housekeeping duties involve using steam to clean oil leaks from pump seals and properly draining hazardous materials
• Purging and flushing piping with water, air, nitrogen, and steam is a key task
• They uphold safety, health, and environmental standards in the plant
• Unit responsibilities require understanding equipment behavior to detect distress in order to perform minor maintenance jobs like line spading, valve greasing, pipe tightening and shaft alignment
• Equipment checks include monitoring flow, pressure, noise, vibration, motor current, bearing temperature(max 80oC), lube oil level, and leakage

Line Tracing and Symbols

• Line tracing, a large part of technician training, helps interpret process flow and instrumentation
• Engineering drawings include Process Flow Diagrams (PFD) and Piping & Instrumentation Diagrams (P&ID)
• Technicians are trained to interpret valve symbols and draw PFDs
• PFDs include major equipment, flows, key operating parameters, variables, pump capacities, heat exchangers, equipment symbols/designations, and major piping/control instruments
• PFDs exclude secondary flows, utilities, and standby equipment
• P&IDs include equipment with tag names/numbers, capacity, size, parameters
• Piping details include line number, code(pipe size/material/insulation), and location
• P&IDs show control loops, valves, instrumentation, fittings, safety valve settings, equipment and material
• They also include material tables, flow arrows, materials of construction and insulation information.

Process Plant Introduction

• Process plants convert raw materials into products
• Petroleum products contain carbon, hydrogen, sulfur, and oxygen
• Petroleum chemistry includes hydrocarbons, naphthenes, olefins, and aromatics
• Compounds are named based on carbon atoms: methane (1), ethane (2), propane (3), and butane (4)
• Hydrocarbons are either paraffin(straight chain prefix n) or branched(prefix iso) compounds with various boiling points -Ring or cyclo compounds which form a ring structure, like cyclopentane are considered Naphthenes
• Olefins are carbon compounds with double bonds e.g., propylene and butylene
• Aromatics have double bonds on carbons and a ring, e.g., benzene, toluene, and xylene
• As the carbon number increases, the hydrocarbon weight increases: dodecane (C12H26) > octane (C8H18)
• Process plants run in continuous(steady rate) or batch modes(small amounts, big variety)
• Petroleum byproducts are named after their processing stage: feed, intermediate, and finished product kept in tanks according to volatility
• Volatility is the ease with which a liquid becomes a vapor/gas

Storage Tanks

• Tank farms house many different types of storage tanks
• Atmospheric storage tanks include open-top, fixed-roof, and floating-roof tanks -Pressure storage tanks include low and high-pressure options

Atmospheric Storage Tanks

• Open-top tanks have no roof and store non-volatile liquids unaffected by weather or pollutants like water or brine
• Fixed-roof tanks have a cone-shaped roof and store low vapor pressure liquids like kerosene, gas oil, and chemicals
• Fixed-roof tanks store less volatile products for higher flash points
• Tank breathing, i.e. vapor release/air drawn into the tank is a problem with both of these tank types
• Floating-roof tanks include pontoons and seals to prevent air/vapor flow
• They store volatile liquids below 65°C, like crude oil, gasolines, naphthas, and alkylates
• Automatic bleeder vents are used to vent the air from the underside floating roof, to reduce evaporation losses and increase safety from fire

Pressure Storage Tanks

• Liquid vapor pressure above 15 psig (1 barg) is stored in pressure storage tanks like cylindrical tanks, sphere tanks, or a dome roof tank

Piping

• Piping is used to transfer fluid from one place to another
• Pipe fittings connect those pipes through threading or welding, but they can cause pressure drops
• Common fittings include tees(a letter T shape), elbows, reducers, plugs, and blinds
• Tee fittings sample a branch line from the main stream
• Tee fittings can be knockout lines which, when moist air is flowed into, the heavier water droplets are separated while the dry air continues to flow into knockout line
• Elbows conjoin two pipes at an angle, and are known for corrosion and erosion at high velocity locations resulting in thinning
• Reducers connect pipes of different diameters
• Plugs have exterior threads to screw into pipes, blocking fluid flow
• Blinds prevent accidental mixing in multi-purpose plants and stop foreign chemicals from transferring to another process/equipment
• Blinds close off piping systems and pressure vessel openings
• Blinds include spade blinds(handle that sticks the flange out), spectacle(disk out of the flange), and flange blinds(round plate)

Hose, Selection, Connection, and Handling

• Hoses support plant tasks, such as temporary connections, purging, cleaning and draining, and transferring chemicals
• Couplings provide attachment to the equipment through press-loks and cam and groove
• Hose selection depends on system type, operating temp/pressure, ambient temperature, and bend radius
• System type selection considers pump pressure, operating cycles, flow medium, and the inner diameter of pipes
• Operating pressure selection needs to withstand high-pressure build-up: hose rupture and a ratio of operating pressure should be 1:4
• Operate at maximum operating pressure for hoses
• Select based on max fluid/gas temperature, as constant high temps can degrade hose
• Fluctuating ambient temps impact cover/reinforcement lifespan. Select proper bend radius to avoid flexing
• Withstand max vibrations via design, and use a neutral braid angle to reduce expansion for Volumetric Expansion safety
• Hoses are colour-coded to identify its application, these include low pressure steam, cleaning and purging, water hose, hot fluid hose, hydrocarbon hose and a corrosive liquid hose
• One end of the hose should be avoided from the unconnected when Handling: could whip or use a safety whiplash
• Do not allow torque which means any twisting that is harmful reduces the service life, which can prevented with floating flange or union for smooth flexing
• Do not bend beyond the minimum recommended bend radius as a fatigue and premature failure could occur
• Storage requires one to lift but not drag, store in locations free of corrosive chemicals, cool, dark, and capped
• Pressure drop in pipelines result from fluid velocity changes because of elevation, pipe and hose fittings, friction, turbulence, and valve or porous media openings

Transfer Operation - Measurement, Hazards, Safeguarding

• The transfer operation moves product from one tank to another, however there can be pressure effects given the tank level of the tank farm
• Improper tank level, static electricity, vapor space etc, can also cause safety issues
• Volume, Time and Length Unit measurements are needed -The S.I unit for volume is cubic meter (m3). -Rectangle tank formula = L x B x H whereas Cylindrical tank formula = 𝜋𝜋𝑟𝑟 2 ℎ -Conversion: 1m3 = 1000 L = 264.17 gallon -The S.I unit for time is seconds (s)
• Conversion: 1h = 60 minute = 3600s -The S.I unit for length is metre (m)
• Conversion: 1m = 100 cm = 1000 mm and 12 inch = 1 feet and 1 inch = 25.4mm
• Pre-startup steps include systematic checks for transfer readiness: check for blinds, check power/air and perform functional checks to see if fluid systems are adequately blocked / not blocked
• Line up ensures correct valves are opened in a specific sequence
• Insufficient tank space can be problematic and causes spillage/ overflow and environment hazard
• The incorrect material sent into a process unit can cause violent material reactions, fire or explosion
• Making preparations require estimated final level work with transfer rates which are measured via Volumetric flowrate (L/min, gal/min), mass flowrate (kg/s, kg/min), and molar flowrate (mol/s)
• Mass flowrate equals Volume/second x Density and Density equals Mass (kg)/ Volume (m3)
• Molar Flowrate, n(mol) equals Mass(g) / Molar Mass(g) (mol)
• Initiate transfers at low pump stroke to attain the required stroke and monitor the tank level for correct rates using glass tube, magnetic and reflex sight glasses and floats to avoid incidents
• Flowmeters are placed on volumetric flow lines that can be classified as volumetric flow with the use of rotameters and turbine flowmeters to indicate the values of products
• Complete transfers by blocking out the inventory in the correct valve sequence and document quantity
• Mole fractions exist in all components but transferring streams contain more than one component
• X A,(mol/mol) is achieved with multiplying moles of A(mol/mol)/ Sum of all moles (mol)

Hazards in Tank Farms and How To Solve Them

• The tank farm has several hazards, these include and cause loss or harm
• Negative or positive/reverse flow can occur where atmospheric and external pressures affect readings and may buckle
• Static electricity, which cause spark ignition depends on the materials near the pipeline, how fast the fluid flows, diameter, use of micro filters or liners such as glass etc.
• Relaxation from use of high purified hydrocarbons have a slower rate reduction of electrons (>100 secs), conductivity(>10,00 pS/m) and a higher number of charges that build up because of Poor Conductors(i.e. long relaxation time)
• Solutions involve bonding and grounding lines to tanks to earth
• The containers are purged with safe oxygen concentrations or transfer in/out at the bottom using dip pipes or transfer-in
• Workers can minimize static via clothing, lower pump regulations and increase or agents are
• Vapor Spaces in Tanks can create ignition sources which can be avoided by controlling the composition and temperature of the produce involved, along with the gas blanketing via vapor-roofs with hatches regularly and avoiding ignition sources under thunder and lightning
• Overfilling results in loss of product, a fire, or damages through lifting. To avoid or fix, adjust or note high fill limits with controllers and cutoff limit at designated fill rates for workers
• Dips sticks identify underground or at ground level limits Boilover, in which hot liquids enter and causes the boil that pushes other contents, must be mitigated with rainwater checks at floating seals or with water detection sampling
• Fires, where pool fires occur given the low surface tension, flash fires due to gas ignition, or with jet fires which trigger the long heat release that needs arrestors made of brick or foundation materials, can be mitigated with separation distances.
• A wall or solid barriers must be made of at least 4-hour fire rating stone or concrete
• Leaks require bunds to retain any spillages with an at least 1 m earthen wall with brick or store and is capable of water drains

Console/Panel Operators

• Console/Panel Man
• Operates the control and manages the tank farm via a Distribution Control System to call up important trends for specification reasons
• Requires an SPC i.e., Statistical Process Control with control charts, distributions, deviations and limits to show defects for consistent quality which is achieved for higher cost They are collected via visual representation at different variable conditions whether they are variable(temp, pressure) or attribute (visuals via different readings or defective ones at 100 percent) -It is a plot of against time to understand variable levels that might destabilize situations(like in collection of readings) for control based on data points within control limits(and indication of the problems past the set points)
• There normal distributions that account for variation - Data, frequency of occurrence, and mean reading are each at a peak of the curve
• Standard deviations are then derived as percentages of 68 points
• Each percent range or normal distribution center has different value line levels that are three squared away

Learn about inter-tank transfer operations in process plants and tank farms. This includes shift teams, line tracing, plant components, and safe transfer procedures. Understand the roles of field technicians and console operators.