L&T-CHIYODA LIMITED
Equipment Engineering Dept.
LAKSHYA-2
FUNDAMENTALS
OF
MOUNDED BULLETS
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
PRESENTATION OBJECTIVES
 Definition
 Introduction
 Why Mounded Bullets ?
 Advantages
 Design Codes and Standards
 Materials of Construction
 Design Loads and Cases
 General Design guidelines
 Location
 Safety distances.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
DEFINITION
 Mounded Bullets:
A storage vessels sited above ground and completely covered
by a mound of earth or similar inert material except for
nozzles, manhole covers, inspection covers fitted on vessels.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
INTRODUCTION
 Mounded bullets are Horizontal cylindrical vessels used
for storage of pressurized gases (i.e. LPG) at ambient
temperature.
 The vessel is installed above the highest ground water
level and the soil cover usually protrudes above grade,
as an Earth mound, hence the term mounded storage.
Mounded LPG Bullets are large, horizontal cylindrical
steel tanks with dished ends of size ranging between 3.5 to
7.0 meter diameter and lengths of 35 to 70 meters or more.
Mounded bullets allow storage of large quantities of
LPG - up to 2,000 MT or more in a single location!
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
WHY MOUNDED BULLETS ?
 Earlier bulk storage of highly inflammable gases (i.e.
Liquefied Petroleum Gas (LPG) etc.) was being stored above
ground storage (i.e. Tanks & Spheres).
 Some major fire & explosions underlined the need to review
the design, procedure, maintenance, fire fighting and safety
aspects of LPG handling.
 A safer option was introduced in the form of Mounded LPG
Storage Bullets since it provides intrinsically passive and safe
environment and eliminates the possibility of BLEVE
(Boiling Liquid Expanding Vapor Explosion).
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
ADVANTAGES

The advantages of mounded storage over above ground
storage:
•
BLEVE can be totally avoided.
•
Protection of equipment against.
o Heat radiation from a nearby fire
o Pressure wave originating from an explosion
o Impact of flying objects.
o Sabotage
•
It results in reduced site area due to less stringent interspacing requirements.
•
The safety distance to the site boundary can be reduced
considerably.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
DESIGN CODES AND STANDARDS
 ASME Sec VIII or PD 5500.
 EEMUA (Engineering Equipment & Materials Users
Association) Publication No.190:00
 OISD (Oil Industry Safety Directorate) - 150 : Design &
safety requirements for LPG mounded storage facility
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
MATERIAL OF CONSTRUCTION
 Material of Construction shall generally be as follows:
Components
MOC
Shell and Heads
SA 516 Gr. 60 / 70
(Impact tested)
SA 537 Cl1
Nozzles necks
SA 333 Gr. 6
Nozzle flanges
SA 350 LF2
External studs / nuts
SA 320 Gr. L7 / SA 194 Gr.
4
Pipe fitting
SA 420 Gr. WPL6
Gaskets
SS 304 SPWD
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
DESIGN LOADS AND CASES 1/2

Design Loads:
Dead weight of the vessel.
2. Weight of the liquid in the vessel.
3. Internal Pressure.
4. Internal vacuum.
5. Loads due to the mound.
6. Loads due to uneven support by the foundation.
7. Loads due to variation of the vessels length (Thermal
expansion & Thermal contraction).
8. Loads due to earthquake.
9. Loads due to an external explosion
1.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
DESIGN LOADS AND CASES 2/2

Design Cases and loads to be considered:
Operating
condition
Hydrotest
condition
X
X
Weight of the liquid in the vessel.
X
X
Internal Pressure.
X
X
Loads
Design Cases Empty condition
with vacuum
Dead weight of the vessel.
X
Internal Vacuum.
X
Loads due to the mound
X
X
Loads due to uneven support by
the foundation
X
X
Loads due to variation of the
vessels length
X
X
Loads due to earthquake
X
X
X
Loads due to an external explosion
X
X
X 10
L&T-CHIYODA LIMITED
Equipment Engineering Dept.
GENERAL DESIGN GUIDELINE 1/2







The vessels should be installed at least 0.6 m above the highest
ground water level in a sand foundation of atleast 1 m thickness in
order to obtain proper bedding.
The foundation of the bullet shall be constructed such that for
the operational lifetime of the bullet, its longitudinal slope shall
be in 1 : 200 minimum and 1 : 50 maximum.
The thickness of the mound shall be 1 meter minimum.
Longitudinal weld seams shall be avoided in the bottom 120
deg.
The ratio of distance between internal stiffeners to bullet
diameter is in the order of 1 : 2.
Minimum 2 no. manholes shall be provided, one at each end of
the bullet.
All plates, welds, HAZ shall be impact tested . Impact test
temperature shall be determined as per design code.
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Equipment Engineering Dept.
GENERAL DESIGN GUIDELINE 2/2




PWHT shall be carried out for the complete bullet.
Radiography shall be full.
There are two methods of arranging nozzles :

All nozzles except manholes and large size nozzles (liquid inlet)
shall be grouped and shall be installed on a dome and not directly
on the shell. Sleeves shall be provided around the domes,
manholes and large size nozzles .This construction is called
DOME TYPE CONSTRUCTION.

All nozzles except manholes and large size nozzles (liquid
inlet) shall be grouped on the shell. Rectangular box shall
be provided around the grouped nozzles, manholes and
large size nozzles . This construction is called BOX TYPE
CONSTRUCTION.
Settlement of soil bearing foundation :

Immediate settlement shall be limited to 50 mm.

Long-term settlement shall be limited to 25 mm.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
LOCATION
Location to be decided after careful consideration of following
influencing factors:
• The area to be covered by mound & the area within the safety
distances, shall be clear of any trees, stumps, combustible material
and other objectionable matter.
• Space requirement for movement of construction/fabrication
equipment and for maintenance.
• Each mound shall have accessibility to fire tendor from at least
two sides.
• Bullets shall be located such that they do not affect or are affected
by other underground structures. e.g. foundations, pipe lines,
sewers, electrical cables.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
SAFETY DISTANCE
The safety distances for mounded storage shall be as follows:
• Minimum safety distance between mounded LPG storage and LPG
pump/compressor house shall be 15 meters.
• Minimum safety distance between mounded LPG storage bullets
and fire water pump house and / or firewater tank shall be 30
meters.
• Minimum inter-distance between the edge of the bullet(s) in
mound shall not be less than 1.5 meters for bullets having diameter
of 1.5 meters and 2 meters for all other cases.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
ANSYS MODEL - 1
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
ANSYS MODEL -2
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
Thank You
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
21
BLEVE
 This means that, if a system catches fire due to leakage or
there is any fire in the near by surroundings, the liquid inside
the container starts expanding due to heat radiation. This will
lead to rise in internal pressure continuously and the container
may explode causing huge damage. This can be avoided by
using mounded storage concept.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
ANSYS MODEL -3
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
ANSYS RESULT (STRESS INTENSITY)
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
ANSYS RESULT (DISPLACEMENT IN “Y” DIRECTION)
CENTER SOFT
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
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L&T-CHIYODA LIMITED
Equipment Engineering Dept.
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