Maindeka is an advanced limpet mine. It is primarily meant for use by Naval divers for underwater sabotage.


It is an underwater charge incorporating a built in time delay exploder intended to be fixed to the hull of a ship magnetically or held in a place by a nylon belt. Highly effective against submarines, war / merchant ships riding at anchor or moored along the pier, or alongside a jetty as well as port installations, pipelines and offshore drilling / processing platforms. It can be easily carried on chariots, when required.


The limpet mine design also lends itself for army applications for use by commandos.


The limpet mines are placed at specific points of ship's underwater hull and are held in position by powerful magnets. After arming, the mine detonates at a set time and the explosive charge damages ship's bottom either to sufficiently cripple the ship rendering it non-operational, or even sink the ship in case of heavy damage when mines are used in large numbers.


Limpet mine, ‘MAINDEKA' is a generation ahead of the existing limpet mines in the international market. It incorporates latest technology of fibreglass body, mechanical and electrical safeties and a reliable programmable electronic timer.


1. Maindeka has been designed to meet the User's requirement with the following variants:

Combat (Naval & Army)





2. The Naval Combat Mine has a fibreglass body. It has ‘Admiralty Grey' colour and can be deployed upto 50 mtrs. of depth. It houses Mechanical Timer, Programmable Electronic Timer, Arming Device, Antilifting Device and Modular type of explosive Container with approximately 1.0 kg of explosive (RDX – TNT).

Practice variant is similar to the Combat Version except that its fibreglass body is painted Yellow and the explosive container is filled with high explosive substitute (HES). It is meant for use by drivers for familiarization with handling and operating techniques. The arming of the mine is seen by a green light and the detonation of mines can be seen by the glowing of red light.


The army Combat ‘Maindeka' is similar to the Naval Combat ‘Maindeka' except that the body is olive green in colour.

5. The Drill Version is same both for the Navy and the Army. It is meant purely for carrying out peacetime exercises. It weighs identical to combat mine, but does not incorporate any magnets / timer etc.


The mine is made to following technical specifications:


Max. diameter 310 mm
Max. height

135 mm

Max. weight 6.00 kgs

Explosive weight

1 kg
Type of explosive RDX/TNT

Arming Delay

a) Mechanical Min. one minute (not to be set)
b) Electronic

Max. 9999 minutes in steps of one minute. Minimum One minute.

c) Total combined Delay Upto 25 + 9999 minutes.
4. Firing Delay (after arming) Min. one minute (not to be set) Recommended 20 minutes set on Mechanical Timer and on electronic timer as per set delay.
5. Safety Devices Safety Pin (Arming pin), shortening of Detonators, Mechanical Arming Delay, Electronic Arming Delay.
6. Max. Operating Depth

50 meters.

7. Adhesivebility Upto 8 knots
8. Damage Potential Hole diameter 240 mm on 22 mm thick MS plate.
9. Shelf life 15 years with medium repairs at every 3 years interval. Arming to be done prior to deployment with Serviceable detonators etc.
10. Buoyancy in water 100 to 350 gms (Negative)
Complete Assembly

The complete ‘Maindeka' Assembly consists of the following:

Mechanical, Electronic Timer Assembly
Safety Device
Arming Device
Antilifting Device
Sealing Components
Power pack
Detonator No. 79 MK1
CE Pellet in holder
Explosives (RDX/TNT)
Magnets assembly or belt assembly

Mechanical Timer

2. The Mechanical Timer is a general purpose timer with a high accuracy at 300 beats per minute. It is fitted with two micro switches separated at an interval of 20 min. A cam fitted on the main drive of the timer operates these micro switches at 5 and 25 min. when started from fully wound position.
3. The timer is tested for vibration, heat, cold, jolting, speed test and other environmental tests, as called for by the Users.

Electronic Timer

4. The Electronic Timer is a quartz-controlled clock which provides an output to actuate the mine after a set delay. The clock operates at 3 MHz and gives accurate timings. The time can be set by a 4-digit thumb wheel switch. Timings can be set on the mine varying from 1 minute to 9999 minutes almost 7 days). The clock counts the time set in minutes and actuate the mine through an SCR.
5. The Limpet Mine along with the Electronic Timer is fully tested for environmental test.


Safety & Arming Mechanism
This assembly provides for safety of Limpet Mine during transport and operation and also keeps the Mine waterproof. This assembly consists of a arming shaft, a conical rubber washer and associated water sealing arrangements. A safety pin is assembled in the upper shaft which keeps the mine in unarmed condition. When the pin is removed the shaft moves down and releases a stopper to start the mechanical timer. The shaft further tries to push out the shaft of the antilifting device (ALD) to operate ALD when any effort is made to dislodge the mine.

The explosive filled in the mine is a composition of High Explosives giving maximum cutting effect. This is filled in modular type of container, the explosive container can easily be separated from the main body.

‘Maindeka’ fully assembled weighs max 6 kgs in air and its negative buoyancy is kept at 100 to 350 gm to ensure ease of carrying underwater by the divers.

Belts and Handles
A system of belts for fastening the Maindeka to the targets (especially in army version where non-magnetic targets are predominant) has also been provided, which holds the mine against any target firmly in lieu of magnetic attachment of Maindeka.

A handle has also been provided for carrying the Maindeka during transit and during deployment.
1. Maindeka has undergone comprehensive static, environmental and sea trials and is considered absolutely safe & reliable throughout its service life. Proper regulations for testing, assembly are to be strictly adhered.

The mine has been subjected to following tests prior to induction:

a)  Design strength
b)  Explosive firing
c)  Damage potential
d)  Drop test
e) Arming and Safety
f)  Adhesivability
g) Environmental tests
i)  Ease of deployment
j)  Water tight integrity upto 50 metres depth of water
k) Anti-lifting test
i)  Delay setting test

Safety incorporated in Mine



a) Clock mechanism is locked by a stopper.
b) The shaft operating stopper is kept locked by an arming pin.
c)  Explosives stored separately till required for deployment.


a) Detonator is kept shorted till the mine is fixed on target.
b) Power supply not connected till arming time is completed.
c) Output circuit is disconnected from detonator till arming time is completed.
d) Four digit switching by thumbwheel switch.
Contact :
Marketing & Export Division
Ordnance Factory Board
Ayudh Bhawan
Government of India
Ministry of Defence
10A, S. K. Bose Road, Kolkata – 700 001, India.

Tel: 0091-33-2248 9027 / 2248 2103 / 2248 5077-80
Fax : 0091-33-2248 1748/2210 8235
Mail :