L.K. Vijh, Executive Director (Plant Operations & Safety Division), Engineers India Limited

Mounded LPG Bullets – Safety in Design, Construction,

Inspection and Operation

Engineers India Limited

National Seminar on ‘Safety in Hydrocarbon Sector : Drilling to Dispensing’

Thursday, September 27th, 2012

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Slide No.-2

Presentation Plan

Introduction to LPG Storage and Transfer

BLEVE

What is Mounded Bullet !!!!!!!?

Design Codes Applicable

Facility Sitting

Design Parameters

Instrumentation and fittings on vessel

Fire and Gas Detection

Operation, Maintenance and Inspection

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Introduction

LPG is a mixture of propane and Butane with an explosive range of 1.8% to 9.5% in air

LPG is colorless with an thermal expansion coefficient of 0.00237 per °C

LPG due to its inherent properties is susceptible to fire and explosion hazards

The conventional method of storage of LPG in India is in a pressurized vessel installed aboveground. For large volumes cryogenic storage option can be used

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BLEVE

Boiling Liquid Expanding Vapor Explosion (BLEVE)

Caused by external flame impinging on the shell of a vessel above the liquid level, weakening the container leading to shell rupture

Causes a sudden release of a large mass of pressurized superheated liquid

Superheated liquids flash typically increasing the volume over 200 times.

Results in heavy damage due to fire ball, pressure wave and impact by vessel fragments.

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BLEVE– Incident

San Juanico Disaster PEMEX, Mexico, 1984

BEFORE AFTER

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San Juanico Disaster, PEMEX, Mexico, November 19,1984

8” Pipe rupture occurred near the sphere

The Control Room operator tried to identify the cause of pressure fall but without success.

The release of LPG occurred for more than 5-10 minute

The gas cloud grew to cover a large area and ignited from a ignition by ground flare.

The VCE severely damaged the tank farm and resulted in LPG leak from other damaged tanks

Just 4 minutes later first tank underwent BLEVE.

Over the next hour, 12 separate BLEVE explosions were recorded.

The two largest BLEVE’s(from 2400 m3 spherical tanks) registered 5.0 seismic reading on R.S

The explosions destroyed the local town of San Juan Ixhuatepec.

Approximately 500-600 people killed and 5000-7000 others suffering severe burns.

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Lessons Learned - San Juanico Disaster

Sitting of Major Hazard Installation

• The high death toll occurred because the housing was too near to the plant. At the time the plant was constructed the area was underdeveloped, but over the years the built-up area had gradually crept up to the site.

Layout and Protection of large LPG Storages

• The total destruction of the facility occurred because there was a failure of the overall system of protection, which includes layout, emergency isolation and water spray systems.

Gas Detection and Emergency Isolation

• One feature which might have averted the disaster is more effective gas detection and emergency isolation. The plant had no gas detector system and probably as a consequence, emergency isolation was too late.

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Mounded LPG Storage

A storage vessel sited above ground and completely covered by a mound of earth or similar inert material except for nozzles, manhole covers

Mounded Storage of LPG has proved to be safer compared to above ground storage

Eliminates the possibility of fire engulfment and radiation from a fire in close proximity.

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Mounded LPG Storage

Mounded bullets have a sand cover around that can take impact of external projectiles/ flying object

Area of Land required to locate mounded bullet is minimal compared to conventional storage

Mounded storage is designed considering maximum working temperature as 55 deg C

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Mounded Storage

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Mound - Fabrication

Mounded vessel(s) shall be placed on a firm foundation & installed so as to prevent movement or floatation.

The preferred type of foundation is a continuous sand bed, supporting the vessel over its full length.

The foundation shall be constructed with a slope of at least 1:200 to facilitate draining of the vessel.

The sand beneath the vessel shall be adequate elevation not less that 0.76 m to facilitate drainage.

Mound shall be earth, sand or non-combustible (vermiculate or perlite) for atleast 700 mm thickness.

The mound shall protect the vessel from radiation and robust against jet fire impingement.

The surrounding of bottom nozzle should be filled with such material that can absorb settlement.

Provision for monitoring settlement of the vessel at minimum 3 reference points shall be provided.

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Mounded Storage Construction Methodology

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Mounded Bullet

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Mounded Bullet

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Engineers India Limited

Design ,Operation, maintenance of LPG Mounded Bullet

26th September 2012

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Inherent Safety Aspects

Cover of Mounded Bullet protects the vessel from Fire engulfment and

radiation from a fire in close proximity

Intrinsically passive and safe environment eliminates possibility of

Boiling Liquid Expanding vapour cloud explosion(BLEVE)

No “Domino Effect”

Reduced Fire case PSV loads as compared to Spheres

Reduced firewater requirement for fire fighting.

Difficult for external agencies to identify the mound as a storage facility

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Facility Sitting/ Layout Considerations

S.No Description Separation

Distances* (m)

1 Between mounded storage and boundary, property line, group

of buildings not associated with LPG Plant. 15

2 Between mounded storage and any other (other than pump/

compressor) facility associated with LPG plant. 15

3 Between mounded storage and fire water pump house and/ or

fire water tank 30

Road of minimum 3.5 m width shall be provided around the mound for movement of earth

moving/ fire fighting equipment

Accessibility to Fire tender at least two sides.

Location of Fire hydrants and monitors at Safe distance.

Locate LPG storage far away from Main Units in downwind direction

Bullet dished ends not to face vital installation

2 m of Minimum inter-distance between the edge of the vessel(s) in a mound is maintained

for bullets having diameter 2m and above to facilitate safe installation, testing,

maintenance and removal of vessels.

* Reference from OISD-150

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Storage Principles

LPG is commercial Butane and commercial Propane.

LPG may be liquefied by moderately increasing the pressure or

reducing temperature

Refrigerated storage is used by suppliers to store large volume of LPG

The main form of LPG storage is LPG Bullets

Normally 85% of capacity is filled with liquid and the remaining space

being taken up with vapor.

As LPG is drawn from the Bullet ,vapor pressure in the Bullet drops and

eventually the liquid boils and producing more vapor and restoring the

pressure.

When liquid temperature rises for instance in summer the vapor

pressure increases .

When liquid temperature drops, the vapor pressure drops.

Typical Bullet size3500m3 of size 8000 MM ID X 80,000 MM (T/T)

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Design Codes

Standards

• OISD-STD-150 (Design and Safety Requirements For LPG Mounded Storage Facility

• OISD-STD-144 (LPG Installations)

• OISD-STD-169 (Guidelines for small LPG Plants)

• OISD-STD-116 (Fire Protection facilities for Petroleum Refineries and Oil/Gas Processing)

• OISD-STD-118 (Layouts for Oil and Gas Installations)

• OISD-STD-152 (Safety instrumentation for process system in HC industry)

• OISD-STD-164 (Fire Proofing in Oil & Gas Industry)

• PD:5500, Specification of Unfired Fusion Welded Pressure Vessels, 2009 Edition

• The Static and Mobile Pressure Vessels (Unfired) Rules, 1981, (with latest amendments)

Approval Given by Chief Controller of Explosives (CCOE ) as per SMPV Rules

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Design Parameters

Description Values*

Design Code ASME SEC VIII or PD – 5500 or equivalent duly approved by CCE

MOC (no H2S) ASTM A 516 Gr. 70 (IT) or SA 537 C II (IT) or PD : 5500 or equiv

MOC (with H2S) ASTM A 516 Gr. 60 or Equiv

Design Temperature -27 °C to + 55 °C

Design Pressure 14.5 kg/cm2.g at top of the vessel

Corrosion Allowance Minimum 1.5 mm (Internal)

Corrosion Protection Cathodic Protection System Provided

External surface of vessel are surface coated for protection from corrosion

Radiography Full

Stress Relieving 100% irrespective of thickness

* Reference from OISD-150

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Fittings and Instrumentation on Vessel

Emergency Isolation • Fire Safe ROV shall be provided on first flange on liquid line (s), vapour outlet and re-circulation

lines from the vessel either from bottom or. No other flanges is provided up to ROVs.

• In case of liquid line from the bottom of the vessel, the minimum distance of 3 m from the vessel to ROV is maintained

• The ROV is provided with volume bottle arrangement for two operation of ROV during instrumentation air failure

Safety Relief Valves • Each vessel shall be provided with at-least two safety relief valves whose capacity shall be

minimum 30% of the capacity required for an equivalent size of above ground vessel.

• All vents and drains are routed to closed Flare system where Flare is available. Otherwise vented vertically upwards to atmosphere ensuring effective dispersion of hydrocarbons

Level Indication • Minimum two different types of level indicators and one independent high level switch shall be

provided. One transmitter shall be of Servo type and other Radar type.

• Radar type level instrument shall have facility to measure RVP and temperature.

• Min two number of manholes on the top of vessel is provided

Pressure and Temperature Indication • One pressure and temperature measuring instrument shall be provided.

• PG shall be provided with two isolation valves and an excess flow check valve.

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Mounded Lpg Storage

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Bottom Oulet Nozzle

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LPG - Water Drain System

Problem of ice formation preventing valve closure.

ANTIFREEZE GLOBE VALVE provided.

DEAD MAN HANDLE VALVE provided in series to ensure operator presence during the entire draining operation.

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Gas Detection System

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Fire Detection System

Fire Detectors

• Automatic fire detectors based on heat detection through thermal fuses/ quartz bulbs/ EP detectors shall be used

Sensor Location

• Minimum one detector on each exposed portion of vessel. If nozzles are covered in dome, each group shall have at least two detectors.

• At least one detector near ROV on all liquid line.

General Scheme for Quartzoid Bulb Detection

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Actions on Fire Detection

Audiovisual alarm at the local/ main control panel and fire water station, indicating the fire

All ROVs on the affected vessel shall close

LPG Pumps and Compressors in LPG Storage area shall trip.

Sprinklers if provided shall operate

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Fire Water System & Fire Proofing

Active Fire Protection

Hydrants and monitors are considered for adequate coverage of

unprotected portions exposed to thermal radiation including the top of

the mound and product pipelines

Hydrants and monitors are located at a safe place and shall not be

installed within 15 meters from the exposed portion facilities/equipment

Auto actuated WaterSprinkler arrangement for top exposed domes,

structures and pumps

Passive Fire Protection

The fire proofing ( 2 Hours rating) of all exposed portion of the vessel is

done including piping up to the first ROVs, appurtenances etc

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Mounded Bullet

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Mounded Bullet

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Slide No.-31

Operation, Maintenance and Inspection

Vessel shall be hydro-tested once every 10 years or at every welding whichever is earlier.

Vessel shall be tested every 5 years internally using visual and NDT Testing. Wall thickness shall be measured ultrasonically.

Safety relief valves shall be tested and calibrated every year.

Settlement of the vessel shall be monitored at least on half yearly basis.

Sprinkler spray density, flow rate and response time for every facility shall be verified once in every 6 months

Cathodic protection System

•CP system given for the bullet is to provide protection against soil side corrosion.

•Protective potential readings to be monitored at fortnightly and quarterly intervals.

• Insulating joints shall be inspected once in a year.

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Operation, Maintenance and Inspection

Maintenance & Testing stipulation given in the code aims to ensure integrity for continued operation.

LPG Vessels are known to suffer deterioration and failures.

Tests at 5 years intervals are extremely critical as the vessel is taken out of service and offers rare opportunity to inspect it from inside.

Operators must engage specialist over and above NDT agency to get full benefit.

Other special NDT tests to be carried out are

•Magnetic Particle Inspection

•Ultrasonic Flaw Detection

•Dye Penetrant Test

•Hardness Measurement

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Operation, Maintenance and Inspection

It has been experienced that mounded bullets have suffered deterioration which was revealed during internal inspection.

In one such instance the defect was serious enough to call for derating of the vessel.

EIL’s specialist group was approached by the owner to avoid derating.

After thorough study, a rectification scheme was given which met the statutory approval and the bullet was brought back to sound health for normal operation.

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Operation

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Commissioning

Commissioning of bullets are carried out as per following steps:

Cleaning and flushing /blowing of system

Tightness test with water/air/Nitrogen with maximum possible pressure

app 10-12 kg/cm2 g

Simulated check of all controls and interlock

Check of all Security System

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Slide No.-36

Commissioning

Inertise with Nitrogen or completely fill up with water to displace air.

In case of water,

displace slowly water with LPG vapors by slowly draining water

When pressure in bullet is equivalent to vapor pressure , pump in liquid

LPG

In case of Nitrogen ,

Nitrogen is to be purged with LPG vapor and also vent out to remove

residual Nitrogen

When pressure in bullet is equivalent to vapor pressure , pump in liquid

LPG

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Slide No.-37

Operation

Receiving LPG product from Unit

Unloading LPG and receiving in bullet for initial requirement

Loading of LPG to Railway wagon

Loading of LPG to Road tanker

Transfer of LPG to Pipelines to Pump to other storage

Pump out of LPG received off-spec for reprocessing

Unloading of sick wagon or sick Tanker

Pump out for LPG vaporizer for Refinery scenario

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Operation - Receiving

Receiving LPG product from Unit

Normally all the vapor lines of Bullets are kept open

Outlet and recirculation line valves are closed

Inlet valve is opened and receiving line is lined up

in the inlet manifold.

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Operation-pump Out

Pump out for Reprocessing/Pump out for

vaporizer/Transfer of LPG to Pipelines to Pump to

other storage

Outlet valve of Bullet is opened and lined up to

Reprocessing Pump /Sale Pump/Vaporizer Feed

Pump

Inlet valve of Bullet is opened and MCF line is

lined up to the Inlet manifold

Pump is started with MCF lined up

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Operation - Loading

Loading of LPG to Railway wagon/Loading of LPG

to Road tanker

Outlet valve of Bullet is opened and lined up to

Loading Pump

Recirculation line valves are opened and lined up

to the same bullet

Vapor space of the Wagon tanker /Road tanker is

line up to vapor line to displace vapor while loading

Pump is started with MCF lined up

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Operation –Unloading Sick Tanker

Unloading LPG and receiving in bullet for initial requirement/Unloading of

sick tanker

Vapor line valve of Bullets are kept open an

Inlet opened and liquid line from tanker line is lined up to Inlet Header

Unloading compressor shall take vapor from vapor line and compress

and route to tankers .

Tanker liquid is displaced with vapor

Liquid is routed to Bullet through Recirculation line

After complete unloading of liquid compressor is used to draw residual

vapor from tanker and route to vapor phase of bullet through vapor line

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Slide No.-42

Operation –Unloading Sick Tanker

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Slide No.-43

THANK YOU