tank storage magazine edisi okt 2014 (pages 71-91)

TANK STORAGE • September/October 2014 71

Experience from smaller fires,

with an area of just a few

square metres of liquid fuel,

is that fuels containing a

high proportion of alcohol,

such as E85, radiate less

heat. This, therefore, has

less thermal effect on their

surroundings compared

to petroleum-based fires

of fuels, such as petrol.

However, the large-

scale tests that the SP

Swedish Technical Research

Institute performed in its

Etankfire project show

the circumstances are

the opposite in the case

of a fire the size of a fuel

storage tank. The thermal

radiation from ethanol fires

is several times higher than

that from petroleum fuels.

Ethanol has a lower calorific

value than, for example,

petrol. This means complete

combustion of ethanol releases

much less energy (about 27MJ/

kg) than complete combustion

of petrol (about 44MJ/kg).

A natural result of this is that

the thermal radiation from

pool fires burning ethanol is

less than that from similar fires

of petrol, which is confirmed

by test results from 2m² pool

fires of fuels containing

varying ethanol contents.

The radiant intensity

(thermal power per unit of

area) of an E97 fire (a mixture

of 97% ethanol and 3% petrol) is

about half of that from burning

commercial petrol. Tests of the

combustion efficiency at this

scale give a value of about

80%, i.e. about 20% of the

theoretically possible power is

not released due to incomplete

combustion. One effect of

incomplete combustion is

the formation of soot.

Changing behaviours

The behaviour of fires of these

fuels changes when the

size of the fire alters. In the

case of a fire burning over

a considerably larger area,

diffusion of oxygen into it will

not be sufficient to maintain a

combustion efficiency of 80%.

Combustion is therefore less

complete, with more smoke

and soot being formed in the

plume. The smoke generally

shields large parts of the flame,

with the result that radiation

from the flame does not

penetrate through the smoke

to the surroundings. In the

case of large petrol or oil fires,

it is actually generally only a

zone of a few metres, closest

to the surface of the burning

fuel, where the flame can be

seen and from which radiation

is efficiently emitted. Further

up, above the fire, the smoke

tends to prevent radiation

to the surrounding area.

Combustion of ethanol,

on the other hand, is much

more efficient than that

of petroleum-based fuels.

One reason for this is that

ethanol does not need as

much oxygen for complete

combustion, and that it does

not consist of long hydrocarbon

chains that form soot particles.

Admittedly, the combustion

efficiency of burning ethanol

falls somewhat as the area of

the fire increases, but by no

means as much as for petrol.

The result is that the radiant

intensity from a large ethanol

fire can be as high as, or higher

than, that from a petrol fire.

Last year, SP investigated

the behaviour of ethanol fuels

in a 254m² pool. The results

showed clearly that smoke

production is less than that from

fires of petroleum-based fuels.

The radiant intensity was

measured in all directions

and at several distances in

order to build up a complete

picture of the distribution of the

radiation in the surroundings.

The measured results were

Radiant heat fluxes from the 254m² pool fire trial of ethanol (E97) [blue] and calculated values for a corresponding petrol fire [green/red lines]. For comparison, the diagram also shows some experimental results from similar petrol fires [grey symbols]

fire safety

Radiant heat flux from 2m² pool fires of ethanol/petrol mixtures at two different distances from the pool edge

fire safety

72 September/October 2014 • TANK STORAGE

compared with corresponding

petrol fires evaluated using

two different established

simulation programmes. In

addition, a certain amount of

experimental data for petrol is

available for comparison. The

results are striking: close to the

fire, an ethanol fire radiates

two to three times as much

heat as a petrol fire, with the

radiant density still being about

twice as high further away.

The difference between

petrol and ethanol fires is

expected to increase further

for even larger fuel surface

areas, as ethanol seems to

be less dependent on the

size of the fuel surface area.

As present day fuel storage

tanks for ethanol often have a

considerably larger area than

the 250m² that were used in

the trials, the results of this work

are definitely relevant for safety

assessments of the storage of

ethanol fuels. At present, these

risk assessments are generally

based on guide values for

petrol which, according to

these results, means there is

considerable underestimation

of the risks associated with

the storage of ethanol.

As storage is an important

link in the chain using bio-

based fuels such as ethanol, a

better understanding of how

to reduce the risks of storing

the fuel is required. As ethanol

is water soluble, it is doubtful

whether a fire in an ethanol

tank could be suppressed using

the same methods as used

against petroleum-based fires,

i.e. by foam application from

high capacity foam monitors.

To date, SP has not been

able to find any example

of a successful suppression

operation against a burning

ethanol storage tank; instead,

all known fires of this type have

concluded with the total loss

of both the ethanol content

and the storage tank.

Further work on ethanol

tank fire fighting is planned

in the Etankfire project, see

www.sp.se/en/index/research/

etankfire/sidor/default.aspx

For more information: Contact [email protected]

The flame from an E97 pool fire

Corporate Offi ce · Cincinnati, Ohio · 513.321.4511www.mesarubber.com/tanks

Memo from the CEO: I am pleased to announce that Mesa Industries has received national certifi cation as a Women’s Business Enterprise by the Women’s Business Enterprise National Council, the nation’s largest third-party certifi er of the businesses owned and operated by women in the U.S. This means we can now help our clients meet their vendor diversity goals.Now clients have one more reason to choose Mesa Industries.We appreciate your business.

Sincerely,Sincerely,

Terry Segerberg, CEO

An American-based company delivering American-made products for the petroleum and aboveground storage tank industry since 1967. Mesa is proud to help our customers achieve their supplier diversity goals.

I am pleased to announce that Mesa Industries has received national certifi cation as a Women’s Business Enterprise by the Women’s Business Enterprise National Council, the nation’s largest third-party certifi er of the businesses owned and operated by women in the U.S. This means we can now help

Now clients have one more reason to choose Mesa Industries.

An American-based company delivering American-made products for the petroleum and aboveground storage tank industry since 1967. Mesa is proud to help our

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lightning protection

Handling a stormysituation

Pipeline and terminal operator Buckeye

Partners owns a large storage terminal

facility in the Bahamas known as BORCO.

As this terminal is located in the tropics

and semi-tropics, Buckeye is justifiably

concerned about the possibility of

lightning damage. Protecting against

lightning is costly. It does not make the

terminal work better or faster, or allow

the tanks to hold more product. In some

cases, lightning protection systems

may actually limit tank fill height.

Lightning protection has historically

been covered under API 2003. Several

years ago, it was broken out of 2003, and

API 545 was established to address this

subject. Since industry codes, standards

and practices have been based upon

historical subjective experience and not

upon empirical evidence, API set aside

funds to study the matter as related

to storage tanks. Culham Laboratories

was hired to test specific assumptions

and protection techniques in laboratory

simulations, and to make both general

and specific recommendations to the

newly formed API 545 committee.

One of the main lessons learned in

that research was the need for bypass

conductors located at intervals around

the perimeter of an external floating

roof (EFR) tank. These fixed conductors

equalise the potential and provide

a path for current flow between a

floating roof and the tank shell. For

years, shunts have been considered

adequate to perform this function.

However, research has shown otherwise.

Lightning is actually a multiple-part

event. It begins with a short duration,

high-energy current flow, followed by

a tail of lower-energy flowing over a

much longer time. As these two events

are electrically vastly different, different

types of conductors are needed.

Shunts are typically located at 10’

intervals around the roof perimeter, and

are spring-loaded to press up against

the inside of the tank shell, providing

a sliding electrical connection. Shunts

provide short, direct low-impedance

paths. As such, they are more effective

at conducting the short duration, high-

energy portion of the lightning discharge.

However, research has shown that it is

actually the long-duration, lower energy

component of the lightning strike that

is responsible for most ignitions. Since

the shunts are sliding contacts, they

may present a high-resistance between

the floating roof and the tank shell.

Current flow across resistance generates

Fixed bypass conductors run from the perimeter of the floating roof to the rim of the tank shell at 100’ intervals around the perimeter of the tank

What you don’t know about tank

farm static and lightning couldmake your hair

stand on end

lightning protection


heat. It is that heat that

causes most ignitions.

Therefore, it became

obvious that supplemental,

low-resistance conductors

are also required. Hence,

the introduction of bypass

conductors. These are fixed

conductors running from the

perimeter of the floating roof

to the rim of the tank shell

at 100’ intervals around the

perimeter of the tank. Since

they must be of sufficient

length to accommodate

the range of motion of the

floating roof, they may present

a high-impedance and a

relatively long response time.

However, those limitations

are compensated for by the

shunts. The bypass conductors

supplement and complement

the performance of the shunts,

performing the tasks for which

the shunts are not suited.

When BORCO built two

new large, 583,000 barrel

EFR tanks at the Freeport,

Bahamas terminal, a study of

best practices was conducted

based upon new knowledge,

terminal experiences, and

discussions with vendors.

Most recommended installing

bypass conductors. In the past,

Buckeye had had operational

problems with certain types

of bypass conductors, so

was looking for an effective

alternative. The company

was most interested in the

simplicity of gravity-powered

bypass conductors, and went

with them as opposed to

mechanical systems. Providing

lightning protection along with

a low maintenance alternative

were the key factors.

Buckeye was also

concerned with the possibility

of direct lightning strikes to

the tanks, as that has been

a problem in the past, so it

also looked at the various

structural lightning protection

systems available.

In order to evaluate

structural lightning protection,

an accurate understanding

of the lightning ignition

mechanism is required. Most

lightning ignitions are not

caused by the heat of the

lightning channel directly

igniting flammable gas or

liquid. It is not like throwing

a burning cigarette on the

tank. The ignitions are actually

caused by incendive arcing

between the perimeter edge

of the floating roof and the

inside wall of the tank shell.

Therefore, Buckeye

ruled out conventional

lightning protection. Installing

Franklin-type lightning rods

on the tanks would have

provided no benefit. In

fact, according to National

Fire Protection Association

NFPA 780, the US lightning

protection standard, tanks are

considered to be inherently

self-protecting, so lightning

rods are not even required.

The theory is that the

tanks are of a sufficient metal

thickness that a direct lightning

attachment would cause no

physical damage. It is worth

noting that the lightning

protection standard was

originally written to protect

wooden buildings, such as

houses and barns, preventing

them from burning down. That

is why it is covered in a fire

protection document. Tanks

are not likely to burn down as

a result of current flow down

the shell of the tank. On the

down side, even if a lightning

rod system performed exactly

as it was designed to do and

lightning attached to the

lightning rod on the tank,

it would cause maximum

difference in potential

between the floating roof and

tank shell, thereby providing

the maximum opportunity

for arcing and ignition.

Buckeye also ruled out

early streamer emitting

(ESE) lightning rods, as

they are basically Franklin

rods on steroids. They are

designed to actively attract

lightning to themselves,

again exacerbating the

difference in potential and

likelihood of ignition.

The company also looked

at overhead wire systems. The

overhead wire is intended

to intercept any lightning

strike to the tank and convey

the energy to ground. This

would keep the heat of the

lightning channel from causing

ignitions. However, the heat

of the lightning channel is not

responsible

for most

ignitions.

It is the

arcing.

As the

overhead

wire system

brings the

lightning

energy to ground very near

to the tank shell, and the

grounding system is also

grounded to the tank shell,

it again makes the problem

of incendive arcing worse.

Attracting lightning to

the tank with any type of

system was unappealing.

Therefore, Buckeye elected

to install streamer-delaying

technology on its new EFRs.

During a lightning strike, the

breakdown of air begins with

the formation of stepped-

leaders branching downward

from the cloud in 150’ steps.

When the stepped-leaders

reach to about 500’ or so from

the ground, they begin to pull

streamers of ground charge

off structures on the surface of

the earth. Whichever streamer

reaches a stepped leader first

determines which structure

or object is struck. This is one

reason the highest profile items

are the most likely to be struck.

Therefore, Buckeye

wanted a system designed

to reduce direct lightning

strikes by delaying the

formation of streamers from

our tanks. The company

was aware of two types of

systems: a rim array system

and a system employing

individual air terminals with

streamer-delaying properties.

Although the rim array system

did reduce the incidence

of lightning strikes, the

individual air terminal system

was equally effective, less

expensive and much easier

to install. Operations was also

ready for a change, as the

rim array system is not very

robust and requires a lot of

inspection and maintenance.

Buckeye has now had

these air terminals and bypass

conductors on its new tanks

for almost two years with zero

complaints. During the summer

of 2013, a storm passed

directly through the terminal

and a tank with the rim system

south of the new tanks was

struck by lightning creating a

seal fire. Minutes later a stack

north of the new tanks was

struck as well. The new tanks

located between the two

objects struck by lightning

were not. This may have been

coincidence, mother-nature,

or modern engineering. Either

way, Buckeye believe it made

the correct decision when it

chose the protection system

and the bypass conductors.

For more information: This article was written by Nate Werner, BORCO Operations at Buckeye Partners and Bruce Kaiser, president at Lightning Master

Bypass conductors and air terminals have been installed on tanks at BuckeyePartners’ BORCO terminal for almost two years with zero complaints

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fire safety


ISO 14001 sets out the criteria for

an environmental management

system. It does not state requirements

for environmental performance,

but maps out a framework that a

company or organisation can follow

to set up an effective environmental

management system.

The standard can be applied to a

variety of levels in the business, from

organisational level, right down to

the product and service level (RMIT

university). Rather than focusing on exact

measures and goals of environmental

performance, the standard highlights

what an organisation needs to do

to meet these goals (IISD 2010).

Environmental impacts of fire

Environmental impacts due to

combustion and the use of extinguishing

agents can be successfully mitigated

by selecting the appropriate

extinguishing agent and technology.

The primary environmental impact is

caused by the fire itself. Not only is there

the value of the material destroyed

by the fire, but the condition of our

common asset - the environment - also

deteriorates. The resulting combustion

products are often extremely harmful

to health. The burning of fossil fuels

changes the composition of the

atmosphere; carbon stored under the

ground for millions of years now re-enters

the atmosphere in the form of carbon

dioxide, causing the greenhouse effect.

The secondary environmental

impact is caused by the extinguishing

agents getting into the environment.

Excessive use of water may cause

water damage, while the use of

extinguishing agents of artificial origin may

pollute the environment. The extent of the

pollution, in other words the secondary

environmental impact, largely depends

on the quality of the used extinguishing

agent and its application technology,

because the volume of the material

required for extinguishing a particular

fire is determined by these two factors.

Classification of extinguishing agentsExtinguishing agents of natural origin

• Water (direct jet, spray, mist)

• Mixtures of gas extracted from

the atmosphere (IG541, INERGEN,

ARGONITE, ARGOTEC, etc.)

• Exploited gases (CO2)

Extinguishing agents of artificial origin

• Extinguishing powders (BC, ABC, D)

• Solid aerosols

• Aqueous solutions (foam

solutions, P, FP, AFFF, AR)

• Halogenated extinguishing

gases of zero ODP (FM-200,

FE-125, TRIIODIDE, NAF

• S 125, NOVEC1230, etc.)

Successful prevention gives the highest

level of environmental safety. The

inertisation of confined spaces serves as

an example in the field of fire protection.

Environmental awareness in firefighting

The law clearly states that when

considering the environment, the best

available techniques (BAT) must be

used for the purpose of prevention.

In eliminating fire incidents,

the following depend on the

appropriate choice of technology:

Burning time (sum of the preparation

time and the extinguishing time),

that determines air pollution.

Specific extinguishing agent

need (total extinguishing agent

need), that determines the water

and soil contamination.

How to deal with 60,000m3+ tanks

Experiences unambiguously show that

the combustion of over 60,000m3 tanks

Fighting fire against the odds

One fire expert suggests a method

of ensuring effective, environmentally safe

fire fighting technology at a hydrocarbon

storage site in extreme circumstances, such

as a lack of water, lack of energy supply and

human resources or extremely low ambient

temperature

fire safety


cannot be extinguished with most of

the applied extinguishing methods.

At the present time, the fire

prevention strategy used by oil and

chemical companies is based on national

environment safety laws, the national

general and professional laws and

standards based on the said laws, and

the guidelines of professional associations,

and primarily relies on the use of mobile

and semi-stable extinguishing equipment.

In essence, the former

extinguishing strategy is that:

• A person or a sensor detects the fire

• Alarms the fire station

• The fire brigade gets to the site

• Assembles the devices

necessary for extinguishing

• Starts and executes extinguishing.

In the case of fire in small-sized tanks,

ideally, the arrival time within the refinery

is 10 minutes or less. After the assembly

of the light technology, extinguishing

can be started less than 15 minutes

from the outbreak of the fire.

In the case of large tanks, high-

capacity extinguishing equipment must

be taken to and set up on the site. In this

case, the time taken to arrive is longer,

as are the assembly and set-up times.

During this, the fire will reach the

stationary combustion stage, and the

metal parts of the tank will start glowing.

During the combustion of a 80,000m3

tank, 14 tonnes of carbon black is

given off into the air every minute.

The problem with traditional semi-fixed extinguishing equipment

The drawbacks to the former known

extinguishing methods and the

essence of the problem are:

• Tank fire prevention is principally

based on the fire prevention

standards, guidelines and semi-

fixed extinguishing concept

formulated some 40-50 years ago

• The operating parameters (foam

solution intensity, extinguishing

time) are prescribed in standards

which are constrained by the

technical possibilities of the time

• The plant has the task of assembling

the foam jet pipes and foam

introduction devices on the tanks

• The foam generation tools, the

foam generators are mounted on

the side of the storage tank, at a

place that is difficult to access

• As a narrow nozzle is used,

foam generators often do not

work and get clogged

• Traditional extinguishing devices

do not operate safely because of

the difficulty of maintaining them

• A fire fighting water network is

necessary to operate this type

of extinguishing equipment

• Devices compulsorily installed in

advance are put into operation

by the arriving fire brigade

• Because of the need to call the

fire brigade and the time it takes to

arrive and assemble the necessary

equipment, extinguishing is started

with considerable delay

• The foam and pump necessary

for extinguishing is brought to

the site by the fire brigade

• Any contamination of the fire

water network may cause

an operating failure

• Because of the low application

intensity value prescribed in the

relevant standards, a large amount

of extinguishing agent is used and

the extinguishing time is long

• As the fire continues for a

long time, the loss is big,

• Environmental pollution is considerable

• The fire endangers health,

life and technique.

No such thing as an eternal flame

International experience shows that

the combustion of 60,000-80,00m3 tanks

cannot be extinguished with most

applied extinguishing techniques.

The fire goes on for tens of hours until

there is no more combustible material,

and then it goes out. During this period,

there is enormous environmental pollution.

The repeated failure to put

out extensive fire has triggered

research to develop new, effective

fire prevention systems.

Tank fire fighting development at US

companies is based on the assumption

that in the case of fire, because of

the long preparation time, fire will

inevitably destroy the devices necessary

to conduct the built-in or semi-stable

extinguishing procedure, so they will

not function when extinguishing starts.

Therefore, the devices previously

built onto the tank by the plant in

accordance with the specifications

of the relevant standards should be

ignored, and purely mobile devices

should be used to extinguish the fire.

This idea can be realised with

high-capacity foam guns.

In some instances of tank fire in the

US, plants in an emergency leased the

equipment from the manufacturer of

the high-capacity mobile extinguisher,

and storage tank fire fighting was

carried out by the specialists of the

same company under contract.

Results are uncertain. It has been

reported in some cases that the team

arriving 17 hours after the ignition of the

fire at the site, started the extinguishing

only after four hours’ preparation.

After all of this, the fire was successfully

extinguished in just 65 minutes.

All together 22 hours and five minutes

burning. And a new world record.

The value of the material ‘saved’ in

the tank was only a small portion of the

cost of the contracted extinguishing,

and even the tank was destroyed.

Tank fire fighting with foam guns

Drawbacks of high performance

mobile extinguishers:

• It is not suitable for putting out the rim

seal fire of tanks with a floating roof

• For its operation, a high-pressure and

high-output fire water system has to

be built, which is very costly in itself

• This critical infrastructure is highly

vulnerable, the complete extinguishing

system is paralysed in the case of an

earthquake or a terrorist attack.

Despite these drawbacks, awareness of

this strategic solution is being increased

because of lthe ack of other solutions.

Main features of the latest tank fire extinguishing systems

• The amount of foaming agent

necessary for extinguishing is

less than 10% of the amount

used by former techniques

• The foam is not produced at the

‘During the combustion of a 80,000m3 tank,14 tonnes of carbon black is given off into theair every minute’

fire safety


place and time of fire fighting,

but well in advance, when the

extinguishing equipment is installed

• Until the moment of starting the tank

fire extinguishing, the pre-mixed foam

is stored in a pressure vessel near the

flammable liquid tank to be protected

• When calculating the foam amount

necessary for extinguishing, foam

intensity and the prescribed

foam cover thickness increases in

proportion to the fire surface, and

the total foam volume is calculated

with a 200-500% safety factor

• The pipelines and nozzles used for

foam introduction are dimensioned

by hydraulic calculations in order to

comply with the prescribed foam

introduction time limit: the upper

time limit for introducing the entire

foam volume is two minutes

• No pressure booster device is

necessary, the foam flow is driven by

the internal pressure of the foam tank.

• No auxiliary energy is needed for the

operation of the fire alarm system

and the start of extinguishing

• An independent extinguishing

apparatus is installed for each tank or

tank group, and these apparatuses

have no common elements

• The response time of the fire sensors is

five to 10 seconds, the extinguishing

time is a maximum of two minutes.

• The equipment only has one moving

part: a valve. Therefore, it offers

extremely high operation safety

• Human error caused by

stress is excluded

• Maintenance and periodical checks

are cheap and very simple

• Foam pipes are simple devices

without any opening and

diminution in diameter

• This system can even be deployed

at places without fire water

supply (military deployment sites,

provisional fuel tanks, storage sites

in a desert or in exposed places)

• Besides tank protection, it is also

suitable for the protection of

other dangerous substance stores

(engine compartment of military

vehicles, generator motors, stores of

flammable chemicals, ammunition

and pyrotechnic substances).

Impact of the new technology on environmental safety

From the aspect of environmental safety,

this is unambiguously the best solution due

to the very short burning time. Additionally,

the small amount of extinguishing

agent used means air, soil and water

pollution can be practically avoided:

• Its operation is not dependent

on any critical infrastructure

• Individual independent systems

provide an increased level of safety

• Time lost by preparations is avoided

by automatic operation

• A small amount of agent is used

which ensures cost efficiency

• The technology has a simple

structure and thus a high level

of operating safety. During

experiments, the equipment was

able to put out petrol fire spread

over 500m2 in 25 and 46 seconds.

Extinguishing tank fire – outline of the task

In the northern provinces of Canada,

oil pipelines run in a length of several

thousands of kilometers in uninhabited

areas. The pump stations that convey

the oil operate without an operator,

under remote supervision. Buffer storage

sites have been built next to the pump

stations; they are used as strategic stores

on the one part, and serve to equate

the varying oil reception capacity of the

pipeline terminal on the other. In the case

of maintenance, repair or technological

change-over, oil is moved to these

buffer stores with a capacity of a few

hundred thousands of m3. These stocks are

drawn when there is greater demand.

These unmanned sites have no

infrastructure at all. The environmental

temperature is far below zero in most

part of the year, the technical equipment

of the plant are designed for -40°C.

The nearest fire service is at a distance

of several hundreds of kilometers,

but could not help anyway without

water and appropriate technology.

Extinguishing tank fire – the mission impossible

Until now, no cost-effective solution was

found to protect tank farms against fire.

The lack of such solution increased the

economic risk of the operators, and

the fire authority was dissatisfied with

the level of safety. The environmental

authority and NGOs strongly opposed

to the construction of the pipelines, and

the lack of fire prevention made it even

more difficult to obtain their consent.

At last, they resigned themselves to the

operation of the unmanned storage sites

at a temperature of -40°C, without fire

prevention for the lack of water supply.

The solution

Having understood the technical nature

of the FoamFatale technology, the

operator decided to request a bid for the

installation of the system, that will be able

extinguishing tank fire at a storage site

under construction. The designer team

prepared the plans for their evaluation.

Technical details

In the first phase, three storage tanks

with an internal floating roof will be

built; one with a diameter of 49m

and two with a diameter of 36m.

Crude oil will be stored in them.

The main point of the fire prevention

concept is that in a heated room, a

pressure vessel will be placed in which

pre-mixed foam will be stored under

pressure, in the volume necessary for

the safe extinguishing of the maximum

potential fire surface. The foam

tank will be connected to the three

hydrocarbon tanks to be protected

with a closed carbon steel pipeline

of appropriate diameter. The foam

pipes will be connected to the foam

tank through pneumatically driven

valves opening when receiving

a signal from the fire sensor.

Design criteria

1. The first step is to determine the

foam cover thickness to be created.

This value increases with the size of

the fire surface, and the expected

higher degree of foam destruction

‘Excessive use of water may cause water damage, while extinguishing agents of artificial origin may pollute the environment’

fire safety


will be taken into account. The

foam blanket thickness will be

calculated with a safety factor

of at least 300% compared to the

effective extinguishing thickness.

2. The second step is to calculate the

total foam volume, which is given by

the multiplication of the fire surface

and the foam blanket thickness.

3. The third step is to determine the

volume of the compressed foam

tank necessary for storing the foam

volume calculated above.

4. The last step is the hydraulic

dimensioning of the foam pipe in

order to meet the most important

criterion, namely, the upper

foam introduction time limit.

5. According to our specifications, at

extinguishing tank fire the entire foam

volume has to be introduced into the

burning tank within two minutes or

less in the case of liquids with a flash

point below 52°C and within three

minutes or less in the case of liquids

with a flash point above 52°C. The

volume flow rate of the foam, which

can be calculated from this, serves

as the basic data for the hydraulic

dimensioning of foam pipes.

Fire protection: how an environmental aware system works

In the case of fire in any of the A, B or

C storage tanks, its fire detector sends

an alarm signal to the pneumatically

operated foam valve control unit. This

valve opens without using any external

auxiliary energy, upon the pressure of

the foam stored in the T1 foam pressure

vessel. The foam flows into the burning

hydrocarbon tank. Inside the tank, a

ring-shaped nozzle conveys the foam to

the tank shell in a curtain-like manner,

and so the foam promptly cools the

shell and protects it from the effect of

the heat transported by convection

and radiation. Flowing down, the foam

reaches the floating roof and fills up the

seal area to reach the upper level of

the foam dam. Falling over the foam

dam, it covers the whole surface of the

floating roof. The process will be the

same when the floating roof submerges

for any reason. Now, flowing down, the

foam reaches the liquid surface and

there, taking a horizontal direction,

closes in the middle of the surface of the

burning liquid and thus puts out the fire.

No more technical or technological obstacles

Similar solutions can be used in a

desert where keeping water ready for

extinguishing tank fire is extremely costly.

In other areas where the traditional

fire prevention solutions cannot be used

because the object (e.g. the fuel depot

of a military unit) is constantly on the

move and the traditional fire fighting

infrastructure is completely missing, the

compacted foam technology is able to

provide the appropriate level of safety.

There are no longer technical or

technological obstacles to introducing

environmental awareness in the work

processes of disaster recovery. This is

now only a matter of resolution to enact

and comply with the relevant laws.

For more information: This article was written by Dr. István Szöcs, aninternational fire fighting expert, inventor andscientist of storage tank fire protectiontechnologies, www.foamfatale.com

Superior solutions and services that exceed customers’ expectations

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Telephone: +44 (0) 1329 284145

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fire safety


tank heating


The rising number of

infrastructure projects around

the globe means higher

volumes of product such as

asphalt and bitumen. These

heavy oils need to be heated

to reduce the viscosity for

pumping and transportation.

Traditionally, heating

in these tanks had been

less important due to

factors such as:

- Smaller capacity tanks

- Tank heating being

part of the tank

manufacturer’s scope

- Changing ambient

temperatures leaving

heat calculations subject

to interpretation

- No accurate method

available to predict

performance.

Heavy oils need to be heated

at the final usage point for

performance and quality

purposes. However, it is also

important to heat these

products at intermediate

stages for transportation

and it is this type of heating

that must be reduced.

There are several direct

as well as indirect costs

associated with heating.

Direct heating can be easily

measured and optimised.

Indirect costs must also be

monitored and reduced

using efficient tank design.

Various petroleum

products are heated to

different temperatures. Factors

to be taken into consideration

for deciding heating options

include: ambient conditions,

storage duration, product

discharge condition (flow rate,

continuous or intermittent

discharge, frequency of

discharge), heating medium

and heating costs, etc.

Immersion heating

This heats the product to

the required temperature,

ranging from 50°C to 150°C.

The intention is to keep the

product ready (low enough

viscosity) for pumping

and transportation.

Traditional methods

involve laying a serpentine

pipe at the bottom of the tank

and passing steam through

it. This apparently simple

design was perceived as

acceptable in smaller tanks

owing to the easy availability

of the raw material. However,

this method is becoming

increasingly complicated

with large storage capacities.

Since steam or hot oil entering

the heating coil loop will

continue to lose heat on

its way, the heating inside

the tank is not uniform. To

improve this, the heating

coils are being made

increasingly complicated.

Inefficient heating

increases start-up time, and

surface and insulation losses

are greater over a longer

duration. Non-uniform heating

leads to non-uniform viscosity

and difficulty in pumping.

Inefficient heating also leads

to increased sedimentation

and additional maintenance.

Platecoil heating can

improve efficiency, internal

circulation and ensure

uniform product properties

inside the tank. The vertically

oriented heating coils situated

at the correct location

induce proper convection

currents inside the fluid and

ensure uniform heating.

Reduced hold-up volume

of the heating coil minimises

start-up time and reduces

the indirect heating costs.

By maintaining uniform

viscosity, pumping is

facilitated. This can also

ensure lower pumping

costs. Reduced sludge

sedimentation due to proper

Tank heating: a new way of thinking

Large tank pipecoil arrangement Small tank pipecoil arrangement

tank heating


circulation also minimises

maintenance costs.

Thus by using proper

heating techniques many

indirect heating costs

can be reduced.

Discharge/outflow heating:

Keeping the entire product

at elevated temperatures is

expensive. Instead, outflow

or suction heaters can be

installed in the discharge

line. With suction heaters

installed inside or outside

the tank, surface losses to

the atmosphere can be

reduced for the period

when the product is simply

stored inside the tank.

Consider a case where

HFO is being stored at 50°C.

If this HFO is stored at 35°C

and heated only at discharge

to the desired temperature,

the atmospheric heat loss

can be reduced. The sample

calculation below shows how

a simple change in heating

philosophy can reduce the

heating costs significantly.

This saving in fuel

consumption will reduce

CO2 emissions and make

operations more eco friendly.

Operators are sometimes

wary of suction heaters due

to concerns over choking.

However, platecoil technology

can overcome this problem.

The concerns of choking

the suction heaters sometimes

deter the operators in using

suction heating technology.

However, with the help of

Platecoil technology internally

or externally installed suction

heaters can address the

concern about choking

while helping the customers

in the application.

For more information: www.tranter.com

Improved convection due to Platecoil technology

Externally installed suction/outflow heater

Simplified heating coil arrangement in a large tank (40,000m3)

Internally installed suction/outflow heater

HFO volume 20m3 20m3

HFO flow at discharge 120m3/hr 120m3/hr

Initial temperature 25°C 25°C

Maintenance temp 35°C 50°C

Discharge temperature 50°C 50°C

Heat for temperature maintenance (kcal/hr) 413,325 1,033,312

Heat for product temp increase (kcal/hr) 769,500 -

Total heat load (kcal/hr) 1,182,825 1,033,312

Fuel (diesel) consumption (lit/year) 81,044 202,610

Saving in fuel (diesel) consumption (lit/year) 121,566

A green comparisonFull tank inheated state

Outflow/ discharge heating

Contact: Carl Bracken • [email protected] • 713.725.6939See us in action on Keyword: Mass Technology Corporation

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Contact: Carl Bracken • [email protected] • 713.725.6939See us in action on Keyword: Mass Technology Corporation

M O B I L E C O L D C U T T I N G S E R V I C E S

Safe-Cut is a service of Mass Technology Corporation.

Ultra High PressureMobile Water-jet CuttingSPECIALIZING IN CUTTING OF

TANKSPIPES

VESSELSCONCRETE

ASPHALTFIBERGLASS

• Environmently Friendly• Adaptable Configurations• Design & Fabrication of Specialty Cutting Tools• Simultaneous Multiple Cutting Head Systems• Easy Set-up & Minimal Support

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YOUR REPUTATION IS MINE.

CAN YOUR REPUTATION BECOME OUR RESPONSIBILITY?

At Vinçotte we want to help guarantee the reputation of our industrial and regular clients when it comes to quality, safety and the environment.

The GATE terminal off the coast of Rotterdam is the first LNG-importterminal in the Netherlands. Our involvement in this project is a perfect example of the wide variety of Testing, Inspection and Certification services we can offer your business.

The Vinçotte group has an annual turnover of 201 million euros and 17 offices worldwide. Our headquarters are situated in Vilvoorde, Belgium.

Take a look at our services on

www.vincotte.com

floating roofs


A floating roof, as its name implies, floats

on the surface of the product in the

storage tank. As the liquid level changes,

during filling, emptying, or expansion and

contraction due to temperature changes,

the roof, by design, will move up and

down with the fluid level in the tank.

The floating roof was designed to

minimise the vapour space between it

and the liquid surface of the product in

the tank. The floating roof has support

legs hanging down into the liquid. At low

liquid levels the roof eventually lands and

a vapour space forms between the liquid

surface and the roof. The support legs are

usually retractable to increase the working

volume of the tank. Since there is no large

vapour space for the liquid to evaporate

into, vapour losses are kept to a minimum.

Types of floating roof designs include

flat pan, vapour mounted and peripheral

pontoon. In its simplest form, the floating

roof is merely a large flat pan, or disk,

slightly smaller in diameter than the tank

shell that floats on the product in the

tank. The circumference of the roof is

fitted with a system of flexible ‘shoes’ to

close the space between the edge of

the floating roof and the tank shell to

minimise vapour loss. The shoe (seal) used

is generally comprised of a continuous

strip of flexible, special rubber material

which is attached to the roof and to the

seal ring around the inside circumference

of the tank shell. The complete seal unit

moves with the roof maintaining a virtually

vapour tight seal. In principle, the floating

roof eliminates losses by greatly reducing

the evaporative loss of the stored product.

Floating roofs, while effective at reducing

evaporative loss and emissions, depending

on the postion when the floating roof

lands on the bottom of the tank could

pose several potential environmental,

production and engineering issues.

The majority of floating roofs have

support legs, such as pinned, tabbed,

sleeved and cable suspended legs.

These leg designs affect how the high

and low leg positions are calculated with

respect to the elevation of the floating

roof for the flow of the tanks, clear of

any obstruction, hardwares below. It is

critical that low and high legs should

be trimmed to correct for the shape of

the bottom (cone up, cone down, etc),

with respect to the apperatures present

beneath the underside of the roof.

Floating roof issues

Recent tank surveys have revealed that

floating roofs do not always remain level

when landing on the tank bottom during

emptying or subsequent filling of tank

might have some remaining liquid in the

tank. If the vacuum breakers happen

to be placed on the low elevation of

the floating roof during these events,

the breaker may fail to open potentially

resulting in damage to the seals around

the floating roof. If the seal is broken then

the vapour that was being prevented

from entering the atmosphere will be

emitted, with possible environmental

and/or regulatory consequences.

Other potential issues that have been

identified include alarm tank gauges

(ATGs) that have been connected to

the floating roof and therefore stops

moving freely once the roof has landed

on its legs. In such a situation, during the

process of emptying the tanks, the ATGs

movement ceases with the roof and the

alarm fails to activate, resulting in the

potential damage to the floating roof,

seals, internal deadwood and other

hardware devices. The vacuum created

could also result in the cavitation of a

suction pump and could also potentially

damage the seals to the floating roof

requiring expensive repairs and loss of

revenue due to the inability for use of the

tank, not to mention the environmental

impact and the regulatory implications.

Importance of FRCZS

A Floating

Roof Critical

Zone Survey

(FRCZS) aids

in minimising

many potentially costly and hazardous

issues and damage that could occur.

FRCZS are performed during the out-

of-service inspection of a tank. This

inspection assists the tank manager in

calculating the appropriate floating roof

leg elevation in the landing position,

the correct positioning of the vacuum/

pressure relief valve and the proper

installation of the mechanical alarm

systems during the emptying of the tank.

There are currently no recommended

or required American Petroleum Industries

(API) methodologies to perform a FRCZS.

However, in API Chapter 2, Section 2A,

the use of the equipment (a laser level

and hand tape) and the certifications

required for each piece of equipment, are

commonly employed during the surveying

and calibration (strapping) of tanks.

Calculations performed should also follow

the best available engineering practices

recommended by API and its shareholders.

Why use a floating roof critical zone survey?

Floating roof leg types

YOUR REPUTATION IS MINE.

CAN YOUR REPUTATION BECOME OUR RESPONSIBILITY?

At Vinçotte we want to help guarantee the reputation of our industrial and regular clients when it comes to quality, safety and the environment.

The GATE terminal off the coast of Rotterdam is the first LNG-importterminal in the Netherlands. Our involvement in this project is a perfect example of the wide variety of Testing, Inspection and Certification services we can offer your business.

The Vinçotte group has an annual turnover of 201 million euros and 17 offices worldwide. Our headquarters are situated in Vilvoorde, Belgium.

Take a look at our services on

www.vincotte.com

floating roofs


Safety and procedure

The FRCZS measurements are performed

on the interior of an out-of-service tank.

All appropriate safety regulations and

procedures should be strictly enforced,

specifically for permitted confined space

entry. Due to the use of a laser in the laser

level, access should be limited to only

personnel performing the survey and care

should be taken not to stare directly into the

beam during the operation of the laser.

Once the laser level has been set,

preferably in the centre of the tank, and,

if possible an unobstructed view to all

the roof legs is afforded, the instrument is

field calibrated to verify that it is working

correctly. When verification of the proper

operation/placement of the level has been

achieved, measurements are made on

each individual leg above the laser beam

(a positive measurement) and below

the beam (a negative measurement)

using a certified hand tape in 1/100th

of a foot demarcations. Measurements

should start at the outside leg closest to

the shell of the tank and the strike point,

and proceed in a clock-wise fashion

until all the legs have been measured.

It should also be noted what type

of roof leg is present in the tank. At the

conclusion of measuring the roof legs, the

vacuum breaker leg should be measured

in the same fashion and its location with

respect to the strike point noted. If an

ATG or other mechanical device is used,

its freedom of movement, independent

of the floating roof, should be verified.

At the conclusion of the measurements,

using the most recent capacity tables, it

should be determined what the current

alarm levels or levels of concern (LOC)

are being used during emptying of the

tank, and what the corresponding roof

leg, if applicable, position elevation, is

during normal operation. Measurement

of the internal deadwood should be

completed to confirm the lowest elevation

the floating roof can descend inside the

tank before damage would occur.

Once the current LOCs are

established they should be compared

with the measurements taken during

the survey. Because the underside of

the floating roof and the bottom of the

tank are not level surfaces, care should

be taken when analysing the data to

first determine where the floating roof

lands on its first leg and where the roof

rests in its final lowest elevation. This will

assist in the determination that the roof

and vacuum breaker leg lengths and

the corresponding LOCs have been

Filling tank: roof legs still touching at high elevation. Floating roof starting to level out. VBis closed. Emptying tank: ATG stops working

Roof floating on product: all legs no longer contacting bottom. Roof is level. VB closed.ATG is working

Empty tank: floating roof resting on out of level roof legs

Filling tank: product reaches low elevation of out of level floating roof. VB still open

floating roofs


accurately calculated and properly set.

Prior to the landing, the floating roof

is level, the roof and the closed vacuum

breaker (VB) legs are floating in product

and the ATG is moving with the roof. If

the length leg of the vacuum breaker is

set so that it opens (lands) when the first

roof leg sets on the tank bottom, then no

vacuum is created under the floating roof

and the ATG is activated even with an

uneven floating roof. If, however, the VB

leg does not touch when the first roof leg

is set on the bottom of the tank during the

removal of product, the air space created

beneath the floating roof has the potential

to create a vacuum. When the negative

pressure (vacuum) reaches a critical level,

the tank will attempt to achieve equilibrium

with ambient conditions. This action could

potentially cause damage to floating roof

seals, cavitation or damage to the pumps.

In summary FRCZS provide the tank

manager verification and/or confirmation

that the apparatus necessary to prevent

damage to the tank, specifically the

floating roof legs, vacuum breakers and

the ATGs, are positioned properly to allow

for safe emptying of the tank and provide

maximum available tank capacity. The

FRCZS can be performed during out-

of-service inspections using standard

equipment, such as a certified laser level

and hand tape, with minimal cost and man-

power. The FRCZS provides the operator

with confidence that when emptying the

tank, best available engineering practices

were employed to calculate the safest

settings for landing the floating roof, and

the placement of the vacuum breaker.

For more information: This article was written by Gauge Point Calibration, Inc., www.gaugepoint.com

HDS plan view of floating roof with high and low elevation

HDS elevation snapshot of cone up bottom tank with floating roof following contour

asset management


Tank inspection is an

important part of effective

asset management,

from both regulatory

and operating efficiency

perspectives. A failure of a

tank can be catastrophic,

but probably more likely

is degradation resulting in

slow loss of stored product

and possibly contamination

of the environment.

Any unscheduled

removal from service can

impact revenues from loss

of capacity, and potentially

lead to higher repair costs as

a faster response is required.

To manage this degradation,

inspections are carried out

on a regular basis and repair

work planned accordingly.

These inspections must

therefore inspire confidence

that they have identified

any degradation correctly

to avoid either unnecessary

repairs or unexpected failure.

A particular issue with any

tank floor inspection is that

once the tank is re-filled it

is very expensive to cross

check any inspection.

Inspections are often

carried out by experienced

third party inspection

companies which deliver a

report on condition. Careful

selection of these companies

will certainly improve

confidence in results, but

any asset operator should

be aware of the inspection

process and challenge the

inspection to deliver the

highest possible quality.

Training

Any task can be improved by

ensuring people are trained

to perform what is required

and this is no different in tank

inspection. There are very

good training programmes

for tank engineers and

inspectors such as API 653

and EEMUA for understanding

tank assessment, and any

inspection should be overseen

by a qualified engineer. In

addition to these tank specific

engineering qualifications

the inspection team should

also be certified in the non-

destructive testing (NDT)

techniques applied. This should

cover as a minimum ultrasonic

testing (UT), Magnetic particle

testing (MPI), and preferably

Magnetic Flux Leakage

(MFL), or other techniques

used to inspect the tank

floor. Certainly UT and MPI

training is widely available

through PCN or ASNT schemes.

Specific technologies

such as MFL are not so

prevalent, but manufacturers

of this equipment can

provide bespoke training

programmes which should be

completed as a minimum.

Alongside these technical

programmes thought should

also be given to simple visual

testing as much can be

identified from a trained eye

before any measurement

tools are used. The technician

should be

trained to

complete

an initial

assessment to

not only identify

any visual

defects, but

also to ensure

the tank to

be inspected

actually meets

the design

specifications.

It is not unusual

on an older

tank for the as built condition,

or subsequently repaired state,

to be different to that detailed

in design documentation.

Procedures

Assuming there are trained

technicians, the next

important control is effective,

detailed procedures. These

procedures should cover every

aspect of the inspection in

detail so the asset owner can

be sure of what will be done.

Any procedure should also be

signed off by an appropriate

Level III trained person. An

effective procedure will:

• Identify the required

preparation of the tank

• Guide the technician to

ensure correct application

of equipment.

• Explain how to assess

any indications

• How to record any

indications

• Ensure safe working

practices

• Apply the most efficient

work methods.

The inspection provider

should also be able to

demonstrate the procedures

it has are implemented

correctly and independently

verified for compliance by

third party assessment such

as ISO9000, or UKAS and

international equivalents.

Any procedures to be

used should be recorded for

future reference as these will

be clear about what has, and

has not, been inspected.

Capability of equipment

As with any task, having the

best tools available will help

the technician to achieve

best results. There are

continued advances in new

NDT technologies that can

improve detection of defects

and accuracy of sizing. The

better the inspection tools

the higher confidence in

the results, assuming the

aforementioned procedures

are implemented correctly.

However, all systems

have some limitations and

knowing which tool is best to

apply for each measurement

is important. The actual

condition of the tank being

inspected will also influence

measurement accuracy, and

this should be considered.

For example, a clean 6mm

thick floor with no coating

will give very good results

tank inspection

Example data archive with Silverwing C-map inspection management tool

asset management


in MFL, but a thick 15mm

annular plate with coating

will reduce the accuracy

and detection capability.

NDT techniques can be

complimentary, and in some

cases they may need to be

combined to give the best

result. Again this comes back

to the detailed procedure

to guide the technician,

and what assessment on site

should be done to decide

which approach to take.

Verification of results

As an inspection is performed,

verification of results should

be carried out to cross check

any indications, and also

ensure the procedures are

being followed. This is easier to

do with the latest inspection

tools such as the Silverwing

Floormap 3Di or Scorpion wall

crawlers as all calibration

data and measurements are

recorded digitally. It is entirely

possible for inspection results

to be sent off site for review by

a level III, who can see what

has been done and make an

assessment of the inspection.

For in tank inspection it is

very important to complete

the verification whilst tank

access is available, but for

external inspections these can

be carried out later. There

is at least one inspection

company in the US that

has embraced this and

can provide remote level III

assessment of its inspections

by sending live inspection

data to its assessment team.

Archiving of results and data sharing

Traditionally an inspection

will deliver a paper copy of

the results with an assessment

that can be archived. This is

a very useful document but

does not give full access to

the inspection data, limiting

any future analysis of results.

When full data capture

of measurements and

calibrations is done this

data can be subsequently

reviewed to see what the

technicians carried out,

and also re-process with

new accept/reject limits

as requirements change.

By recording all

measurement data it also

gives the opportunity to re-

process with new analysis

techniques that can improve

the quality of measurements

without re-scanning. It is

therefore possible to improve

understanding of asset

condition, and potentially

extend working life as a result.

Companies such as

Silverwing are also developing

inspection database

management tools, such as

C-Map, that will provide easy

access to inspection results

across multiple sites, making

an inspection a live document

that can be shared between

engineers and sub-contractors

such as repair teams,

and also make historical

comparisons for risk based

inspection (RBI) much easier.

Conclusion

If an inspection is performed

with attention to training,

procedures employed, use

of the latest technologies,

verification and data analysis

it is possible to have a high

confidence in the inspection,

whilst remaining efficient and

cost effective. With improved

archiving through database

management tools, leading

to easy interpretation of data

with powerful analysis tools, it

will in future aid tank engineers

to make decisions based

on higher confidence in the

inspection, with potential to

reduce the operating safety

margins and therefore cost.

For more information: This article was written by Wayne Woodhead, CEO, Silverwing, www.silverwingndt.com

0151 355 2685 www.fenelontanks.com [email protected]

Fenelon Storage Tanks offer customers a unique one-stop shop service for all new build tank

projects and repair/refurbishment requirements. Expertise from our in-house Design Department and fully equipped workshop/fabrication facilities provide

support for our on-site construction teams.

• Technical advice and support for clients.

• Finite Element Analysis reports using the latest Solidworks 3D modelling simulation software.

• Calculations and drawings for all types of storage tanks.

• All designs carried out to the latest British, European or API tank codes.

• Certified EEMUA and API 653 Storage Tank Inspectors.

• Professional Project Management/HSQA Department.

• Fully qualified & employed Site Management, experienced Tank Erectors and Welders.

• Employed Appointed Persons for the planning and supervision of crane lifting operations.

tank storage magazine edisi okt 2014 (pages 71-91)

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