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General
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This Document is a write-up
about the requirements of Tactical Hardened
Shelters intended for operations under NBC
Warfare conditions, as per Military
Standards, (Which we can achieve).
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2 The NBC Hardened shelters
will be designed for the three aspects of
Nuclear, Biological and Chemical Warfare |
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Minimization of NBC
Contamination
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Protection against NBC
Contamination &
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Ease of Decontamination
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Function
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The Shelters will provide a
Toxic Free Area (TFA) against N, B&C Agents,
wherein the personnel can function without
Individual Protective Equipment (IPE) and,
designed for protection from an Atomic Blast
(Nuclear Fission Bomb) of 20 KT at a
distance of 4000 m from Ground Zero (GZ).(Shelters
can also be designed for higher levels of
hardening) |
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The shelters will incorporate
the following features |
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Protection against Biological
& Chemical Warfare |
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The passage of military
vehicles through regions of NBC
contamination requires that the equipment be
so designed as to minimize the contamination
on the equipment and facilitate the
decontamination activities on the equipment.
For example, the heads of fasteners and
rivets are areas of contamination and are
difficult to de-contaminate. They also offer
points for the ingress of NBC contaminants
into the Shelters. (MIL-HDBK-784). Welded
Shelters are assembled by welding the
internal and external joints between the
structural sandwich panels, totally
eliminating the use of rivets / fasteners
and hence are ideal for NBC environs |
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The Shelters will be designed
as per MIL-HDBK-784: Guidelines: Design to
minimize contamination and facilitate
decontamination of Military vehicles and
other equipments: Interiors and exteriors |
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The joints will be welded to
meet the requirement of this standard, which
states that welded joints are preferred for
equipments that pass through NBC
contaminated areas. Rivets and fastener
heads may draw-in NBC agents into the TFA
zone (MIL-HDBK-784) and must be avoided |
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The exterior of the shelter
will be painted with CARC (Chemical
Agent Resistant Coating) paint |
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The decontamination agents
like STB, DS2 etc, are highly corrosive and
can damage rubber, certain plastics and
metal. CARC paints are resistant to the
corrosive action of the decontamination
agents |
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Environmental Control Units |
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MIL Grade ECU’s will be
provided in the shelter, as per the cooling
and heating requirements. Dehumidification
units can be provided as an option. The
output from the ECU’s will be ducted into
the shelter for air distribution |
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The ECU Units will be
installed in the shelter, as per the
requirements of MIL-HDBK-116: The Military
Handbook on the Environmental Control of
Small Shelters, considering the requirements
of blast, fragmentation and transit
protection |
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The installation will be
designed for withstanding 6g’s in the
vertical and lateral directions and 10g’s in
the longitudinal direction, which is the
requirement for NBC shelters |
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BC Ventilation system |
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This will be integrated to
the shelter to provide sufficient clean,
filtered air, to maintain a small positive
over pressure of 0.7 inch of water inside
the shelter TFA, to prevent penetration of
contaminants from the outside. During the
NBC operations, the ECU fresh intakes must
be closed |
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For example, considering the
requirement of providing clean air to 6
persons occupying the Shelter TFA, the
following type of NBC ventilation system can
be integrated to the shelter |
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This meets the requirements
of ISRAEL STANDARD SI 4570 Part 3: Air
Ventilation and Filtration systems for
Air-Raid Shelters: Filters and MIL STD 810.
The Manufacturers test certificate will be
provided for the BC system |
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The NBC Filtration system
(NATO Stock No. 4240-17-116-2728) is a
compact heavy duty, high performance
ventilation and filtration system, supplying
clean air to the shelter, at times of peace
or during conventional combat and filtered
air during NBC contamination |
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The system is designed as
over pressure system (i.e. mounted outside
and pressurizing filtered air inwards). The
purified air exhausts via an over pressure
valve, which regulates the positive pressure
in the shelter |
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The paint finish will be
according to MIL STD`s and allows for
decontamination |
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Heating and air conditioning
can easily be combined with this filtration
system |
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This system is in use by
several armies across the world and is
developed, produced and tested according to
MIL Standards |
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Air Flow rate:
For Example |
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(Ventilation / Filtration
mode) 230 / 150 cubic meter per hour, [
135/88 cfm] Please note that as per ASHRAE
Standard 62 requirement of maximum indoor
level for CO2 of 1000 ppm, minimum outdoor
air requirement is 15 cfm per person. (For
office environs, it is 20 cfm per persons).
This indicates that the rated airflow rate
of 88 cfm in filtration mode, will suffice
for 88/15 = 5.86 or 6 persons occupying the
shelter, during NBC attack |
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Anti blast valve, pneumatic
actuation, closing pressure 5 Kpa Blast
pulse |
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Separation efficiency with
particle size of 0.3 micron > 99.9995%. |
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Over pressure inside the
compartment in the filtration mode – 13 to
50 mm WC Adjustable |
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Pressure gage with alarm will
be provided to measure the indoor and
outdoor difference pressure and will warn in
case of shelter pressure failure |
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Integrated Protective
Entrance (IPE):
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This is a pressurized
transitional compartment. In it personnel
coming in from a contaminated atmosphere,
can be subjected to a recommended 5 minute
air wash and can perform personal
decontamination operations before entering
the TFA. |
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Protection against Nuclear
blast effects |
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The various effects of a
nuclear blast and how the shelter will
provide protection to men and equipment is
detailed below |
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EMP:
or Electromagnetic Pulse is a product of all
nuclear explosions. It is a high intensity,
short duration, 50 KV/m electromagnetic
wave, which can cause damage to sensitive
electronics. The frequency of EMP varies
from 10 KHz to 10 GHz. |
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The Shelter will provide EMI/EMP
attenuation levels of 60 dB+ over the
frequency range of 150 KHz to 10 GHz, as
mentioned in MIL-HDBK-116 requirements for
Tactical Shelters. We have achieved
shielding levels of 80dB+ @ 10 KHz to 18 GHz
frequencies, in our Welded Shelters.
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All the joints in the shelter
will be assembled by welding, without the
usage of riveting. Welding the joints offers
the best protection against the penetration
of EMP signals. – MIL-HDBK-419: Grounding,
Bonding and Shielding for Electronic
Equipments and Facilities. A comparison
between the EMITR’s of welded and riveted
shelters are shown here |
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Riveted Shelter: EMI
Test conducted at M/s LRDE as per IEEE 299,
Test report No. EMR/EMI/EMC/TEST/R :180 dt
25th – 26th Sep 2002
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Welded Shelter: EMI Test
conducted at M/s BEL-BG as per IEEE 299,
Test report No. 862
dt 01.03.04
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The entry of EMI/EMP and
lightning surge will be prevented from being
conducted into the shielded shelter via the
power and signal cables by using power line
filters / EMP Filters |
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All the shelter entry points
like the doors will incorporate EMI/EMP
gaskets and weather gaskets |
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Blast Overpressure Wave:
A nuclear blast initiates a high pressure
wave, which moves outward from the fireball.
The front of the blast wave i.e the shock
front, behaves as a moving wall of highly
compressed air, which is the cause of much
destruction. The Shelter is manufactured by
assembling structural sandwich panels,
exhibiting high strength to weight ratios |
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A blast wave from a 20 KT
nuclear explosion has the following effects: |
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- 3 psi at 2.68 Km and |
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- 1 psi at 8.8 Km from the GZ. |
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Thermal Radiation:
is the high intensity, short duration flash
of heat emanating from a nuclear explosion |
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For a 20 KT nuclear
explosion, thermal radiation is not of much
consideration at 4000 m from GZ – Effects of
Nuclear Weapons: Samuel glasstone, US Dept
of Defence). The effect is less than 5 cal/
cm sq. This temperature can be shielded by
the shelter, which incorporates high density
Polyurethane Foam as the core material. (As
a comparison: Solar radiation is 1 to 2
cal/cm sq and the requirement for 3 rd
degree burns is 8 cal/cm sq). |
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Blast Fragments:
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Objects like small stones,
pebbles etc, are converted into high speed
ballistic fragments due to the blast wave.
The protection from the threat of ballistic
fragmentation is essential to prevent the
cracking or penetration of the EMP shield
and the air tight seal essential to BC
protection. Ballistic panels will be
provided on the external surface of the
shelter panels for protection |
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As per the above mentioned
effects from a 20 KT atomic explosion, the
shelter will be designed as per Intermediate
Hardened Shelter (4 psi) as stated in
MIL-HDBK-116. The shelter will withstand |
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- An incident over pressure
nuclear blast of 4 psi (2813 Kg / meter sq)…
(ref ‘Why Vacuum
Bag Bonding?’) |
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- Ballistic fragmentation
protection from 60 grain fragment at 225 m /
sec. |
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- Thermal radiation shielding
(optional) |
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Nuclear Radiation Shielding:
For a 20 KT atomic blast, the estimated
value of radiation (gamma and neutron) at a
distance of 4000 m is about 0.03 cGy. (ref ‘Nuclear
Radiation Attenuation Lining’) |
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please note
that There is no known tolerance
for nuclear radiations. i.e there is no
definite proof that even small doses of
nuclear radiation, may not in some way be
harmful to the human body. As per NATO
specification, AMedP-6 (B), soldiers
receiving less than a total of 150 cGy will
remain combat effective with symptoms of
Nausea, Anorexia and Diarrhea (cramps) for 2
days post exposure. The shelter is designed
to provide maximum attenuation possible,
keeping in mind the mobility aspects of the
shelter (Nuclear shielding is achievable
only by the incorporation of Mass) |
