आयुध निर्माणी बोर्ड
Ordnance Factory Board
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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.