Stable Liquids: all components are liquid, none of the components are trying to boil
Unstable Liquids: a gaseous component exists

one or more component want to boil, gas bubbles out once the pressure is relieved

Tank Venting Emissions emotions while in storage occur due to the evaporative loss of the liquid and results with changes in the liquid level.
Emissions from a fixed roof tank:

losses during storage because of breathing/standing losses

losses during the emptying and filling operations known as working losses

external and internal floating roof tanks are emission sources duet the evaporative losses that occur during standing storage and withdrawal of liquid from the tank.

Standing Storage losses: result of evaporative losses through rim seals, deck fittings, deck seams

Total losses from fixed roof storage tanks slides 7,8,9 and 10

Vapor Space Expansion Factor: depends upon the properties of the liquid in the tank and the breather vent settings
if the tank location is known an equation in slide 10 can be used.

if location is unknown, the factor can be calculated using typical meteorological conditions.

Vapor Space Saturation Factor.

Molecular weight of gasoline changes with the change in Reid Vapor pressure.

Working losses: refers to the loss of product vapors as a result of tank filling or emptying operations.
equations for Lw are found in slide 13,14

Losses from Floating Roof Storage Tanks External Floating Roofs:
majority of rim seal vapor losses are wind induced.
they can also occur due to permeation of the rim seal material by the vapor. this doesn't occur if the correct material for seal fabric is used

Internal Floating Roofs:
deck seams are a source of emission due to the fact that they may not be completely vapor tight if the deck is not welded.

Total losses calculations are the sum of: rim seal, withdrawal, deck fitting, and deck seam losses

The equations are not intended for:

estimating losses from unstable or boiling stocks or from mixtures of hydrocarbons or petrochemical for which vapor pressure is not available

estimating losses from closed internal or closed domed external floating roof tanks, which hare vented using a pressure or vacuum vent

estimating losses from tanks in which the materials used in the rim seal/deck fitting are deteriorated or significantly permeated by the stored liquid

Slide 17 has the equations

Operational Issues:
Storm Water on Floating Roof tank - Drainage Operation:
storm water accumulated on the floating roof may affect its flotation.
a flexible pipe running from the floating roof down the tank and to an outlet above the ground is used to drain it

Operational Problems:

small/large volumes of the product can penetrate the pipe through pinhole or cracks. draining the product

product may run over the floating roof through the seal and exit through the pipe

the pipe can be bent or clogged preventing water to pass through it

Solutions:

Installation of Oily Sheen/Water Detector: it is a leak detector, alarms are triggered is the detector detects oil or oil on water.

Detection of Clogs in the Roff water drainage system: if air is indicated after a rainy day it means that the pipe is bent or clogged and no water is running through it

Savings on Water Treatment Costs: the Oil Sheen detect can be used to control valves, pumps, and sump gates. this way the user can decide on the discharge of the storm water, the oil water can then be diverted to treatment.

Operational problems:

an overflow spill due to the malfunction of level alarm systems or operation error

Ignited overflow spill can result in fire in the dike or funded are as well as fire at the surface level of the tank

spill fire should be controlled before surface fire

securing the spill area with a foam blanket works, foam may tilt the floater or sink it

if the floating roof is lost, the fire will intensify because the presence of a floating roof limits the amount of surface area

rim seal fires may take place, they're controllable with small hand-lines or dry chemical extinguishers.

Foaming methods:

subsurface foam injection
topside fixed foam chambers
hydrofoil monitor nozzels

they control a full surface fire.
when entire tank top surface area is involved, Large volume Aqueous Film Forming Foam streams are used.

	Created by Yasmina Moussa about 9 years ago

Normal-level (N-level) Transmission and Storage (Midterm 2 ) Note on Petroleum Storage Tanks Emission and Losses 8C, created by Yasmina Moussa on 27/11/2015.