This document provides an introduction to fuzes and their functions. It discusses the general requirements of fuzes including their construction, safety devices, classifications based on assembly, filling and function. It describes the typical parts of a fuze including the initiation, middle mechanism and magazine parts. Safety is a key consideration in fuzes to prevent premature functioning during production, storage, transportation and flight. Functional assurance of fuzes is tested through proof firing in instant, delay and safety modes.

1. 1
INTRODUCTION TO FUZE
& IT’S FUNCTION

2. 2
CONTENTS
• PREFACE
PREFACE
• EXPLOSIVE TRAIN OF ARTILLERY AMMUNITION
EXPLOSIVE TRAIN OF ARTILLERY AMMUNITION
• INTRODUCTION
INTRODUCTION
• GENERAL REQUIREMENT OF FUZE
• VARIOUS SAFETY DEVICES IN FUZE
• FUZE CLASSIFICATION
FUZE CLASSIFICATION
• GENERAL CONSTRUCTION
GENERAL CONSTRUCTION
• INITIATION PART
INITIATION PART
• MIDDLE MECHANISM
MIDDLE MECHANISM
• MAGAZINE PART
MAGAZINE PART
• SAFETY IN FUZES
SAFETY IN FUZES
• FUNCTIONAL ASSURANCE OF THE FUZE
FUNCTIONAL ASSURANCE OF THE FUZE
• FAILURE OF THE FUZES
FAILURE OF THE FUZES
• A LIST OF FUZES MANUFACTURED/USED BY ORDNANCE FACTORIES IS APPEN
• FUZES AT OF KHAMARIA UNDER PRODUCTION
FUZES AT OF KHAMARIA UNDER PRODUCTION
• FUZES AT OF KHAMARIA UNDER R&D
FUZES AT OF KHAMARIA UNDER R&D

3. 3
PREFACE
PREFACE
While doing Newton’s thinking & Marathon
efforts for production of fuze “Brain of the
ammunition”, we normally forget that one big
hole is sufficient in the cat’s house for
mother cat & child cat. The same situation
happens during fuze production sometimes.
Every scientist / officers/staff starts their
thinking with Einstein's solution and
generally forgets the basic of the start.
CONTENTS

4. 4
FUZE
BURSTING CHARGE SHELL
PROPELLING CHARGE
PRIMER
PERCUSSION ELEMENT
FIRING PIN OF WEAPON
BURSTING
CHARGE
EXPLOSIVE
TRAIN
(UPON IMPACT)
PROPELLING
CHARGE
EXPLOSIVE
TRAIN
(UPON FIRING)
CARTRIDGE CASE
EXPLOSIVE TRAIN OF ARTILLERY AMMUNITION
EXPLOSIVE TRAIN OF ARTILLERY AMMUNITION
CONTENTS

5. 5
INTRODUCTION
INTRODUCTION
It is known that in any conventional
ammunition, FUZE is one of the most important
parts apart from shell, Cartg. Case, propellant,
primer, Tracer, tail unit etc.
Fuze is generally a mechanical device in a
projectile designed to initiate its action at a pre-
determined time & place
CONTENTS

6. 6
General requirement of fuze
• 1. It must have a body to contain.
• 2. A striker to function the detonator.
• 3. A detonator.
• 4. Good streamlined shape.
• 5. Proper shape for ballistics efficiency.
• 6. Must have enough strength to withstand the
various forces acting on the the fuze.
CONTENTS

7. 7
General requirement of fuze
• 7. It must be air-tight.
• 8. On long storage the explosive content should
not get deteriorated.
CONTENTS

8. 8
Metals used in the manufacture of
fuzes
• 1. The bulk of material is non-ferrous. The
various forms of brass (Copper Zinc alloys) are
most widely used. The advantage are :-
b) Do not corrode easily.
c) Large numbers are produced quickly and
easily machined .
d) The mechanical strength is sufficient to
withstand the stresses encountered during
use.

9. 9
Metals used in the manufacture of
fuzes
• 2. Ferrous materials are used for various
components:-
b) Steel for set screws, washers and safety caps.
c) Stainless steel for strikers needles.
d) Tinned steel for spring.
3. Mazak is used for shutters and magazines.
4. Metals for manufacture of fuzes used with
Lyddite are Shellite filled shell must not contain
more than 0.1 % Lead to minimize the
formation of sensitive Picrates.

10. 10
Various safety devices in fuze
It is removed before loading
manually
----DO----
3. Safety cap
pin
Gets removed due to set-back
force.
Provides safety while
handling storage and
safety on transport.
2. Detent with
detent spring
Thr creep spring over comes the
striker due to rapid deceleration
or set forward motion of the
projectile on impact.
Provides safety during
flight by preventing the
inertia pellet from hitting
the striker thus preventing
pre-matures.
1. Creep spring
How it gets removed.
Purpose for which used
Safety Device
CONTENTS

11. 11
Various safety devices in fuze
By centrifugal force and shock of
discharge.
Making bolt shutter
segment, striker and
collars to provide safety in
the bore.
5.Centrifugal
bolt , Pea ball,
shutter,
masking bolt
etc.
Gets removed on centrifugal
force.
To mask the detonator
from striker.
4. Safety lever
and safety
catch
How it gets removed.
Purpose for which
used
Safety
Device
CONTENTS

12. 12
Various safety devices in fuze
By air pressure.
Provides safety in the
bore.
8. Plunger and
Pawl
By gas pressure.
Seals fire channel
7. Spindle
On shock of discharge.
Prevents shutter to reach
detonator.
6. Segment,
Tape and
Collar
How it gets removed.
Purpose for which
used
Safety
Device
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Fuze can be classified as under:-
Fuze can be classified as under:-
1.Based on assembly with shells :-
1.1 Nose fuse
Nose fuse – The fuze is assembled at
the top/nose of the shell e.g. Fuze Fz-104,
Fuze A 670M (OFK).
1.2 Base fuze
Base fuze – The fuze is assembled at
the rear portion of the shell e.g. Fuze L29-
A3 (OFCh).
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14. 14
2. Based on magazine filling :-
Based on magazine filling :-
2.1 Disruptive type
Disruptive type – In which the magazines
are filled with HE & produce a detonation
wave. Used only with HE, HEAT shells.
2.2 Igniferous type
Igniferous type – In which the magazines
are filled with gunpowder & produce only a
flash.Generally used with a powder filled
shell but can also be in conjunction with a
gaine.
Fuze classification
Fuze classification
CONTENTS

15. 15
3. Based on fuze function :-
3.1 Direct action
Direct action – The fuze requires head-on impact
& it functions instantaneously e.g. Fuze Mine-1C
(OFK).
3.2 Delay action
Delay action – The fuze has in-built delay. It may
be mechanical or chemical delay. Fuze A 670M has
Mechanical Delay whereas Fuze Fz-104, Fuze 259
have Chemical Delay (OFK).
3.3 Graze action
Graze action – The fuze is capable to function on
glancing blow/grazing of ammunition on ground e.g.
Fuze B-429, Fuze B-429E, Fuze DA 4A (OFCh).
Fuze classification
Fuze classification
CONTENTS

16. 16
3.4 Time action
Time action – Designed to function the
projectile at the end of a predetermined time of
flight, the time being adjusted by the gunner
before the round is loaded. These fuzes are sub-
divided into the following types.
3.4.1 Combustion type
Combustion type – The required delay is
given by train of powder which begin to burn
as soon as shell is fired from the gun. The
powder contained in two time rings, one of
which can be adjusted to give various times of
burning by altering the effective length of the
powder train.
Fuze classification
Fuze classification
CONTENTS

17. 17
3.4.2 Mechanical Type
Mechanical Type – The delay is obtained
by the unwinding of the spring of a clock work
mechanism which is set to a definite tension by
the gunner before loading.
3.4.3 Proximity action (Variable time (VT))–
Proximity action (Variable time (VT))–
It functions on reaching within a critical distance
from the target e.g. Fuze VT-8A (OFCh).
Fuze classification
Fuze classification
CONTENTS

18. 18
3.4.4 All fuzes used for surface to Air
ammunitions have in-built self destruction
which simultaneously works after firing
from gun. It ensures actuation of un-used
ammunition in trajectory after firing at
specified time limits.
Fuze classification
Fuze classification
CONTENTS

19. 19
In most of the nose fuzes, first two parts are
exposed over the shell whereas the third part is
within the shell in assembly. Due to this, all
threads for first two parts are RHT and for
third part is LHT, (exception –Fuze B429 &
B429E) since gun rifling gives clockwise
spinning normally. The above theory is vise-
versa for base fuzes.
Fuze classification
Fuze classification
CONTENTS

20. 20
General Construction
General Construction
Fuze can be divided in mainly three parts
1. Initiation part (Striker part)
2. Middle mechanism (Delay &/or Safety
part)
3. Magazine part
CONTENTS

21. 21
Initiation part
Initiation part
This part is generally activated on impact.
The striker moves forward to penetrate/impinge
the detonator or detonator moves backward to
get penetrated which is considered as first
action of the explosion train.
In electrical/electronics fuzes, piezo
generator gets crushed enabling to generate
high value of current for a small time which
enables the continuity of subsequent actions of
the explosive train.
CONTENTS

22. 22
Middle Mechanism
Middle Mechanism
In most fuzes middle mechanism is a delay
device. The fuze is allowed to penetrate to the
required depth into the target by imposing delay
in its function to get maximum lethality/damage.
Delay in fuze function is achieved
1. By chemical delay
2. By mechanical delay
CONTENTS

23. 23
The chemical delay is achieved by
introducing chemical powder of required sieve
size limits, specified pressure & dwell time to
achieve a specified density to attain a specified
delay time limit.
Mechanical delay is achieved
generally by a clock mechanism.
Middle Mechanism
Middle Mechanism
CONTENTS

24. 24
Magazine part
Magazine part
Magazine part has chemical pallet(s)
which have less VOD than detonator but
more flashes to transmit the detonation
wave to the chemicals of shell.
CONTENTS

25. 25
Safety in fuzes
Safety in fuzes
Our essential requirement of any fuze being
that the fuze MUST NOT function at my
courtyard but MUST function at
neighbour’s/enemy courtyard compels
introduction of safety parameters in the fuzes.
Safety is required during :-
1. Fuze production
2. Storage, handling & transportation
CONTENTS

26. 26
3. Shock of discharge from the weapon
4. Flight of the ammunition
5. Muzzle safety ( example-SDA)
The devices incorporated in a fuze to attain the
above objectives are called safety devices. In order
to make the fuze function, the safety is removed.
1. By hand/manually
2. By overcoming/attaining required forces.
Safety in fuzes
Safety in fuzes
CONTENTS

27. 27
The safety devices get removed or the fuze gets
armed normally after overcoming the desired value
of the following forces(especially for mechanical
fuzes)
2.1 by set back force due to acceleration.
2.2 by centrifugal force due to rotation.
2.3 by set forward force due to retardation
2.4 by removal of chemical safety.
Safety in fuzes
Safety in fuzes
CONTENTS

28. 28
Functional assurance of the fuze
Functional assurance of the fuze
Functional assurance of the fuzes is
ensured by proof at all related parameters
1. Instant mode
2. Delay mode
3. Safety of the gun
CONTENTS

29. 29
The fuzes may have following failures
1. Sealing failure
Sealing failure- Fuze in safe mode should
not function but it functions in static proof in
unarmed condition.
2. Blind
Blind- Fuze fails to transmit its detonation
wave to shell resulting non-function of the
ammunition termed as blind. In this case, fuze may
either partially function or may not function at all.
FAILURE
FAILURE OF THE FUZES
OF THE FUZES
CONTENTS

30. 30
3. Low detonation
Low detonation-Fuze functions with weak
detonation resulting failure of the fuze
function.
4. Premature
Premature- Fuze functions either inside
the bore of the gun or at the muzzle or in the
trajectory within the specified safety distance.
5. Improper delay
Improper delay- Fuze functions before or
after the specified time limits of delay.
6. There may be other defects specific to the
type of fuzes.
FAILURE OF THE FUZES
FAILURE OF THE FUZES
CONTENTS

31. 31
A list of fuzes manufactured/used by Ordnance Factories is
appended below:-
FUZE
FUZE AMMUNITION
AMMUNITION ORIGINAL DESIGN
ORIGINAL DESIGN
1. 104 M-12 40 MM L/70 BOFORS, SWEDEN
2. FFV 447 84 MM RCL/HE FFV, SWEDEN
3. FFV 651 84 MM HEAT FFV, SWEDEN
4. FFV 64 C 84 MM ILLG ROUND FFV, SWEDEN
5. 933 30 MM ADEN GUN ROYAL ORD.,UK
6. DASD 30 MM NAVAL OFK/ARDE
7. A670 M 30 MM BMP-II USSR
8. PDM 572C1 155 MM AMMN BOFORS,SWEDEN
9. BD 2B 106 MM RCL ACTION, USA
10. 213 MK-5 105 MM IFG UK
11. VT 8A 130 MM RVC/FVC USSR
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FUZE
FUZE AMMUNITION
AMMUNITION ORIGINAL DESIGN
ORIGINAL DESIGN
12. DA 4A 81/120 MM MORTER PEPA, FRANCE
13. B-5K 57 MM ROCKET USSR
14. L106 A3(NOSE) 155/105/130MM BRITISH AEROSPACE
15. L29-A3 105 ANTI TANK ROYAL ORD.,
UK
16. B-429 130 MM RVC/FVC USSR
17. B-429E 125 MM HE USSR
18. 117 105 IFG ROYAL ORD., UK
19. ALL WEATHER FZ 23 MM GHASHA USSR
20. FAIR WEATHER FZ 23 MM GHASHA USSR
21. MG-25 23 MM SCHILKA USSR
22. 259 40 MM L/60 ROF, UK
CONTENTS

33. 33
FUZE
FUZE AMMUNITION
AMMUNITION ORIGINAL DESIGN
ORIGINAL DESIGN
23. 162 MK-9 M1 120 MM MORTAR ROF, UK
24. B-15 125 MM HEAT USSR
25. AT-4A ND BAR MINE ARDE
26. FZ MINE BAR MINE ARDE
27. FZ KONKURS KONKURS MISILE USSR
28. FZ PROXIMITY 76.2 76.2 MM NAVAL ROF, UK
29. FBN 2-I 250 KG/450 KG
30. FBN 3-I 250 KG/450 KG
31. FZ PROXIMITY 76/62 MM SRGM NESHCHEM,AFRICA
32. PD M9030 76/62 MM SRGM NESHCHEM,AFRICA
33. FZ B-25 140 MM ROCKET
34. FZ AVU-ETM AREAL 100-120KG USSR
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34. 34
Fuzes at OF Khamaria under production
Fuzes at OF Khamaria under production
FUZE
FUZE AMMUNITION
AMMUNITION ORIGINAL DESIGN
ORIGINAL DESIGN
1. 104 M-12 40 MM L/70 BOFORS, SWEDEN
2. FFV 447 84 MM RCL/HE FFV, SWEDEN
3. FFV 651 84 MM HEAT FFV, SWEDEN
4. FFV 64 C 84 MM ILLG ROUND FFV, SWEDEN
5. 933 30 MM ADEN GUN ROYAL ORD.,UK
6. DASD 30 MM NAVAL OFK/ARDE
7. A670 M 30 MM BMP-II USSR
8. MG-25 23 MM SCHILKA USSR
9. 259 40 MM L/60 ROF, UK
CONTENTS

35. 35
Fuzes at OF Khamaria under R&D
Fuzes at OF Khamaria under R&D
FUZE
FUZE AMMUNITION
AMMUNITION ORIGINAL DESIGN
ORIGINAL DESIGN
1. PD M9030 76/62 MM SRGM NESHCHEM,AFRICA
2. FZ B-25 140 MM ROCKET
3. FZ AVU-ETM AREAL 100-120KG USSR
4. B-5K 57 MM ROCKET USSR
5. Fuze multi mode Multi Mode Hand Grenade TBRL (DRDO)
hand grenade
6. ALL WEATHER FZ 23 MM GHASHA USSR
7. FAIR WEATHER FZ 23 MM GHASHA USSR
CONTENTS

36. 36