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INTRODUCTION TO FUZE & IT’S FUNCTION

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CONTENTS• PREFACE• EXPLOSIVE TRAIN OF ARTILLERY AMMUNITION• INTRODUCTION• GENERAL REQUIREMENT OF FUZE• VARIOUS SAFETY DEVICES IN FUZE• FUZE CLASSIFICATION• GENERAL CONSTRUCTION• INITIATION PART• MIDDLE MECHANISM• MAGAZINE PART• SAFETY IN FUZES• FUNCTIONAL ASSURANCE OF THE FUZE• FAILURE OF THE FUZES• A LIST OF FUZES MANUFACTURED/USED BY ORDNANCE FACTORIES IS APP

ENDED BELOW:- • FUZES AT OF KHAMARIA UNDER PRODUCTION• FUZES AT OF KHAMARIA UNDER R&D

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PREFACEPREFACE

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.

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FUZE

BURSTING CHARGE SHELL

PROPELLING CHARGE

PRIMERPERCUSSION ELEMENT

FIRING PIN OF WEAPON

BURSTING CHARGE EXPLOSIVE TRAIN(UPON IMPACT)

PROPELLINGCHARGE EXPLOSIVE TRAIN(UPON FIRING)

CARTRIDGE CASE

EXPLOSIVE TRAIN OF ARTILLERY AMMUNITIONEXPLOSIVE TRAIN OF ARTILLERY AMMUNITION

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INTRODUCTIONINTRODUCTION

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

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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.

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General requirement of fuze

• 7. It must be air-tight.

• 8. On long storage the explosive content should not get deteriorated.

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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 :-

a) Do not corrode easily.

b) Large numbers are produced quickly and easily machined .

c) The mechanical strength is sufficient to withstand the stresses encountered during use.

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Metals used in the manufacture of fuzes

• 2. Ferrous materials are used for various components:-

a) Steel for set screws, washers and safety caps.b) Stainless steel for strikers needles.c) 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.

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Various safety devices in fuze

Safety Device Purpose for which used How it gets removed.

1. Creep spring Provides safety during flight by preventing the inertia pellet from hitting the striker thus preventing pre-matures.

Thr creep spring over comes the striker due to rapid deceleration or set forward motion of the projectile on impact.

2. Detent with detent spring

Provides safety while handling storage and safety on transport.

Gets removed due to set-back force.

3. Safety cap pin

----DO---- It is removed before loading manually

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Various safety devices in fuze

Safety Device

Purpose for which used

How it gets removed.

4. Safety lever and safety catch

To mask the detonator from striker.

Gets removed on centrifugal force.

5.Centrifugal bolt , Pea ball, shutter, masking bolt etc.

Making bolt shutter segment, striker and collars to provide safety in the bore.

By centrifugal force and shock of discharge.

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Various safety devices in fuze

Safety Device

Purpose for which used

How it gets removed.

6. Segment, Tape and Collar

Prevents shutter to reach detonator.

On shock of discharge.

7. Spindle Seals fire channel By gas pressure.

8. Plunger and Pawl

Provides safety in the bore.

By air pressure.

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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 fuseNose fuse – The fuze is assembled at the top/nose of the shell e.g. Fuze Fz-104, Fuze A 670M (OFK).

1.2 Base fuzeBase fuze – The fuze is assembled at the rear portion of the shell e.g. Fuze L29-A3 (OFCh).

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2. Based on magazine filling :-Based on magazine filling :-

2.1 Disruptive typeDisruptive type – In which the magazines are filled with HE & produce a detonation wave. Used only with HE, HEAT shells.

2.2 Igniferous typeIgniferous 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 classificationFuze classification

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3. Based on fuze function :-3.1 Direct actionDirect action – The fuze requires head-on impact & it functions instantaneously e.g. Fuze Mine-1C (OFK).3.2 Delay actionDelay 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 actionGraze 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 classificationFuze classification

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3.4 Time actionTime 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 typeCombustion 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 classificationFuze classification

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3.4.2 Mechanical TypeMechanical 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 classificationFuze classification

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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 classificationFuze classification

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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 classificationFuze classification

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General ConstructionGeneral Construction

Fuze can be divided in mainly three parts

1. Initiation part (Striker part)

2. Middle mechanism (Delay &/or Safety part)

3. Magazine part

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Initiation partInitiation 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.

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Middle MechanismMiddle MechanismIn 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

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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 MechanismMiddle Mechanism

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Magazine partMagazine 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.

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Safety in fuzesSafety 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 production2. Storage, handling & transportation

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3. Shock of discharge from the weapon4. Flight of the ammunition5. 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/manually2. By overcoming/attaining required forces.

Safety in fuzesSafety in fuzes

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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 retardation2.4 by removal of chemical safety.

Safety in fuzesSafety in fuzes

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Functional assurance of the fuzeFunctional 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

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The fuzes may have following failures

1. Sealing failureSealing failure- Fuze in safe mode should not function but it functions in static proof in unarmed condition.

2. BlindBlind- 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.

FAILUREFAILURE OF THE FUZES OF THE FUZES

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3. Low detonationLow detonation-Fuze functions with weak detonation resulting failure of the fuze function.

4. PrematurePremature- Fuze functions either inside the bore of the gun or at the muzzle or in

the trajectory within the specified safety distance.

5. Improper delayImproper 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

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A list of fuzes manufactured/used by Ordnance Factories is appended below:-

FUZEFUZE AMMUNITIONAMMUNITION ORIGINAL DESIGN ORIGINAL DESIGN

1. 104 M-12 40 MM L/70 BOFORS, SWEDEN2. FFV 447 84 MM RCL/HE FFV, SWEDEN3. FFV 651 84 MM HEAT FFV, SWEDEN4. FFV 64 C 84 MM ILLG ROUND FFV, SWEDEN5. 933 30 MM ADEN GUN ROYAL ORD.,UK6. DASD 30 MM NAVAL OFK/ARDE7. A670 M 30 MM BMP-II USSR8. PDM 572C1 155 MM AMMN BOFORS,SWEDEN9. 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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FUZEFUZE AMMUNITIONAMMUNITION ORIGINAL DESIGNORIGINAL DESIGN

12. DA 4A 81/120 MM MORTER PEPA, FRANCE13. B-5K 57 MM ROCKET USSR14. L106 A3(NOSE) 155/105/130MM BRITISH AEROSPACE15. L29-A3 105 ANTI TANK ROYAL ORD., UK16. B-429 130 MM RVC/FVC USSR17. B-429E 125 MM HE USSR18. 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

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FUZEFUZE AMMUNITIONAMMUNITION ORIGINAL DESIGN ORIGINAL DESIGN

23. 162 MK-9 M1 120 MM MORTAR ROF, UK24. B-15 125 MM HEAT USSR25. AT-4A ND BAR MINE ARDE26. FZ MINE BAR MINE ARDE27. FZ KONKURS KONKURS MISILE USSR28. FZ PROXIMITY 76.2 76.2 MM NAVAL ROF, UK29. FBN 2-I 250 KG/450 KG30. FBN 3-I 250 KG/450 KG31. FZ PROXIMITY 76/62 MM SRGM

NESHCHEM,AFRICA32. PD M9030 76/62 MM SRGM

NESHCHEM,AFRICA33. FZ B-25 140 MM ROCKET34. FZ AVU-ETM AREAL 100-120KG USSR

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Fuzes at OF Khamaria under productionFuzes at OF Khamaria under production

FUZEFUZE AMMUNITIONAMMUNITION ORIGINAL DESIGNORIGINAL 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 USSR9. 259 40 MM L/60 ROF, UK

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Fuzes at OF Khamaria under R&DFuzes at OF Khamaria under R&DFUZEFUZE AMMUNITIONAMMUNITION ORIGINAL DESIGNORIGINAL DESIGN

1. PD M9030 76/62 MM SRGM NESHCHEM,AFRICA2. FZ B-25 140 MM ROCKET3. FZ AVU-ETM AREAL 100-120KG USSR4. B-5K 57 MM ROCKET USSR5. Fuze multi mode Multi Mode Hand Grenade TBRL (DRDO) hand grenade6. ALL WEATHER FZ 23 MM GHASHA USSR7. FAIR WEATHER FZ 23 MM GHASHA USSR

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