Cord Relay and Cord Relay-MS
Explosives Division of GULF OIL Corporation Limited
manufactures non-electric detonating relays under the name
Cord Relay and Cord Relay-MS. They are used in conjunction
with detonating cord trunklines in opencast metal and
coal mines, quarrying, civil construction and in underground
metal mines various types of stoping operations.
They provide an accurate delay between blastholes in a row
or across the burden in multi-row blasts. Cord Relay and
Cord Relay-MS can be used for developing various delay
patterns such as Row delay, Diagonal, V or V1 patterns.
Cord Relay consists of two millisecond delay detonators of the
same delay interval placed in a specially designed plastic housing.
The configuration of the delay detonators inside the plastic
housing renders the Cord Relay bi-directional. The plastic housing
has a provision for hooking up detonating cord at either
end. The delay interval is printed on the plastic housing.
Cord Relay-MS consists of a small length of shock tube
with delay detonators of same delay factory assembled on
both ends. Each delay detonators is placed inside a
unique ergonomically designed plastic housing. The
plastic housing has provision for simple and fast hook-up
of detonating cord. The revolutionary design of
CORD RELAY-MS results in accurate delay firing times and
eliminates fast actions and flash-overs. They are bidirectional
in use. The delay interval is indicated through a
sticker placed on the shock tube.
Advantages of Using Cord Relay and
Cord Relay-MS
Safe:They are non-electric delay devices, thus immune to
extraneous electricity sources such as stray currents, static
electricity and Radio Frequency (RF) energies.
Simple to Use: They are ‘bi-directional’ and very simple to
use.
Misfire Free: Use of tie-lines in the surface detonating cord
hook-up provides two or three surface detonation paths,
thus minimizing the risk of misfire.
Accurate:They provide accurate delays. They get initiated
sequentially and hence eliminates the problem of overlap,
which is common in delay detonators.
Unlimited Delays: As they are initiated sequentially, firing
of infinite number of drillholes is possible, facilitating in
conducting large blasts.
Less vibrations: Maximum charge per delay can be
controlled by using relays of different delay intervals n the
surface hook-up.
Firing of one drillhole at a time is possible, where required.
Hook-Up for Cord Relay
- Lay the detonating cord trunkline with minimum slack
between drillholes.
- Cut the trunkline at the point using a sharp knife at the
point where relay is to be connected.
- Pass one cut end of the detonating cord through hole
provided at one end in the plastic housing and double loop
as shown in sketch.
- Repeat the same procedure at the other end.
Hook-Up for Cord Relay MS
- Lay the detonating cord trunkline with minimum slack
between drillholes.
- Cut the detonating cord trunkline using a sharp knife at
the point where relay has to be connected.
- Pass one cut end of detonating cord through the two
holes provided in the plastic housing of CORD RELAY-MS
as shown in the sketch.
- Repeat the same procedure at the other end
Usage Guidelines for Cord Relay
and Cord Relay-MS
- Never use relays under water. Keep them away from
water puddles during use.
- The cut ends of detonating cord should be kept dry.
- Position the relays close to the borehole or row being
delayed.
- In multi-row blasting, detonating cord safety lines should
be placed in the surface hook-up as an insurance to guard
against possible risk of misfire due to ground movement
cut-off of cord.
- Where individual drillholes are fired in sequence, use of
two relays ‘in parallel’ is recommended.
- Where parallel safety lines are provided, the loose ends
of detonating cord must be kept apart to avoid ‘flash-over’.
- Do not allow detonating cord to lie over the relay, as it
can damage the unit upon detonation. During hook-up,
avoid long pig-tails of detonating cord, as it can fall over the
shock tube and result in cut-off (see sketch). Both can result
in misfire.
While blasting using relays, closed loop surface hook-up
should be used. Tie-lines must be placed in such a manner
that:
- Two or three surface detonation paths are available for
drillholes.
- The previously intended delay sequence is not altered viz
the firing time of drillhole or a set of drillholes should be
same from all directions.
- While carrying out Row delay blasting, cross-ties must be
provided at every 35-40 meters of trunkline to eliminate
the effect of long surface detonation path.
Delay Intervals Available
17, 25, 42/50, 65/67, 100/109 & 176 milliseconds
Precautions
- Do NOT subject explosives and detonators to impact,
friction or fire.
- Do NOT use Cord Relay and Cord Relay-MS under water.
- Do NOT carry out charging of explosives during an
approaching storm or when there is lightning activity in
the blast area. Vacate the blast area and resume
operations only after the storm has passed.
- Do NOT attempt to fight explosive fires.
Hook-Up of Detonating Cord on to
Cord Relay-MS
Packaging
100 nos. of Cord Relays are packed in a carton, and placed in a
wooden case. Markings on the case indicate manufacturer’s
name, product name, delay interval, case number, date of
manufacture, net weight and gross weight.
Quantity per case: 1500 nos. (Home), 1000 nos. (Export)
Placement of Cord Relay-MS
Statutory Classification and
Shipping Information
Petroleum & Explosives Safety
Organization (PESO),Government of India |
Class 6
Division 3 |
| IMDG Classification |
|
| Class |
1 |
| Division |
1.1 |
| Group |
D |
| U.N Number |
0029 |
| Page Number |
1259 |
| Stowage Category |
II Type ‘C’ |
|
