Title of Invention

A PROCESS-SAFE DETONATOR.

Abstract The present invention provides a process safe lA/1 W detonator with cylindrical housing with an open and a closed end. An initiator unit disposed at the open end of the hollow housing to provide a hot-wire sensitive pyrotechnic charge, a diaphragm member disposed by pasting on the said initiator unit, a stem channel extending from the initiator unit member to the closed end of the hollow housing disposed in said housing, Nickel Hydrazine Nitrate (NHN) acting as a low friction sensitive primary explosive disposed in said stem channel in proximity to the initiator unit to receive flame from the pyrotechnic charge of the initiator unit, a secondary high explosive disposed in functional contact with said Nickel Hydrazine Nitrate, to receive the explosive force for detonation, and a sealing member disposed on the open end of the hollow housing for effective sealing of the detonator.
Full Text



A FROCESS-SAFE DETONATOR Technical Field
The present invention is in the field of detonators with a primary explosive having low sensitivity to friction. The present invention more particularly relates to a process-safe detonator with Nickel Hydrazine Nitrate (NHN) as a primary explosive. Background and prior art
Detonators are extensively used for triggering high explosive systems of various applications. A conventional electrical detonator usually consists of a hot wire initiated pyrotechnic charge of required electrical rating, followed by a primary and a secondary detonating explosive in close contact to each other. The primary explosive in detonators gets initiated by the flame from the initiator unit (squib element) and generates a shock wave required for detonating the adjacent high explosive, like RDX. U.S Patent 5,889,228 describes a detonator assembled from housing, an output charge and an initiation means which includes a pulverulent ignition charge disposed in direct initiation relation to the initiation means, and an output charge that may contain a pulverulent deflagration-to-detonation transition (DDT) charge and a base charge. The ignition charge has an average particle size of less than 10 microns. The initiation means may include a semiconductor bridge and the ignition charge may be compacted with a force less than about 40.5 MPa.
The conventional detonators generally contain Lead Azide as primary explosive. However, Lead Azide based detonators have several disadvantages. The main disadvantages are, i) Lead Azide, due to its high sensitivity to friction, calls for extreme care in operations like manufacture, handling, transportation and processing of detonators, which in turn makes the plants expensive and ii) drainage of lead containing poisonous waste water from the manufacture of Lead Azide creates serious environmental pollution. The above disadvantages can be overcome using the present invention that depicts a detonator, using a safe explosive coordination compound, Nickel Hydrazine Nitrate as the primary explosive. Objects of the invention
The primary object of the present invention is to provide a safe and easily processable detonator using environmental-friendly non-azide and non-lead based primary explosive.

An object ot Uie present invention is to provide a detonator using a low friction sensitive
primary explosive.
Another object of the present invention is to provide a non-azide Nickel Hydrazine
Nitrate (NHN) detonator as a primary explosive.
Another object of the present invention is to produce a detonator that is capable of
initiating full order detonation in the high explosive systems.
Yet another object of the present invention is to provide a detonator, which is simple in
its design and construction.
Summary of the invention
The present invention provides a process safe 1A/1W detonator with cylindrical housing
with an open and a closed end. An initiator unit disposed at the open end of the hollow
housing to provide a hot wire initiated pyrotechnic charge, a diaphragm disposed by
pasting on the said initiator unit, a stem channel extending from the initiator unit to the
closed end of the hollow housing disposed in said housing, Nickel Hydrazine Nitrate
(NHN) acting as a low friction sensitive primary explosive disposed in said stem channel
in proximity to the initiator unit to receive flame from the pyrotechnic charge of the
initiator unit, RDX (Cyclotrimethylenetrinitramine) acting as a secondary high explosive
is disposed in functional contact with said Nickel Hydrazine Nitrate, to receive the
explosive force, and a sealing member disposed on the open end of the hollow housing
for effective sealing of the detonator. Primary explosive in detonators gets ignited by the
flame from the squib and generates a shock wave due to detonation of the primary
explosive namely NHN in the present invention. The shock wave thus formed is
transmitted to the adjacent high explosive, like RDX and sets it off.
Brief description of the drawing
FIG. 1 depicts the longitudinal cross-sectional view of the detonator along with the parts
of the squib, of this invention, using Nickel Hydrazine Nitrate as the primary explosive.
Description of the invention
The present invention is described by referring to Fig 1. The detonator of the present
invention comprises a substantially hollow cylindrical housing 1 within which entire
detonator assembly is enclosed. The cylindrical housing 1 is constructed from material
which is chosen from steel or any other compatible material that can withstand the

detonation shock on its own. In case the material used to construct the housing 1 cannot withstand the detonation shock on its own, then the housing 1 should be enclosed within a suitable hardware that acts as confinement. The cylindrical housing 1 is provided with an open end and a closed end. In the present invention, as an exemplary embodiment the thickness of steel used for construction of the detonator housing 1 is in the range 0.15 -0.3 mm. The outer diameter and length of the housing 1 is 5.8 - 10.6 mm and 16.2 - 37.3 mm respectively. It is within the purview of the invention to select a variable configuration for the housing 1 as per the requirements.
At the open end of the housing 1, an initiator unit of 1A/1W electrical rating is accommodated within the housing 1. The squib, which is a flame producing device containing a hot wire sensitive pyrotechnic charge, which is based on boron and potassium nitrate that gets ignited by passing the required electric current. The squib element of the present invention further comprises a charge holder 5, a base 6, a sleeve 7, a pyrotechnic charge 8, a diaphragm 9 and a pair of lead wires 10 having the ends soldered with a bridge wire 11 after inserting through the base 6.
The charge holder 5 of the squib element is accommodated within the inner periphery of the open end of the detonator housing 1. The charge holder 5 is selected from suitable material that helps to hold the charge. In the present invention aluminium alloy is adopted for the charge holder. However, alternate materials that can hold the charge can also be employed. Various charges can be selected for the squib element to meet required specifications, such as electrical ratings, ground/high altitude ignitability, gas-to-solid ratio of the reaction products, flame temperature etc. A base 6 of the squib element is disposed within the charge holder 5. Towards the open end of the housing 1, a pair of lead wires 10 is partially inserted into the base 6 of the squib to flush seat with the inner surface of the base 6 across which a lohm resistance bridge wire 11 is soldered. Towards the closed end of the housing 1, the base 6 acts as a platform on which a sleeve 7 is accommodated.
A pyrotechnic charge 8 is press loaded under sufficient pressure with the base 6 as the platform at the bottom and the sleeve 7 acting as an enclosure for said pyrotechnic charge 8 at the sides. The base 6 also does the function of providing insulation. The lead wires 10 of the squib element connect the detonator of the present invention to the external

electrical energy source for heating the bridge wire 11 and subsequently igniting the pyrotechnic charge 8.
A diaphragm 9 is disposed by pasting on the brim of the charge holder 5, adjacent to the sleeve 7 and above the pyrotechnic charge 8. The diaphragm 9 acts as a closure for the initiator unit and prevents entry of moisture till the squib is assembled in the detonator housing 1. The diaphragm 9 which is pasted on the brim of the squib charge holder of the detonator of the present invention acts as a closure for the initiator unit and prevents entry of moisture till the squib is assembled in the detonator housing. The paper, which acts as diaphragm, in the present invention will be consumed by the flame generated by the squib. The flame directly initiates the primary explosive NHN. The deflagration-to-detonation transition process (DDT) is occurring in the NHN only. There is no role for the diaphragm in the DDT process.
On the open end of the housing 1, the squib element as described above is accommodated and towards the closed end of the housing 1, a stem channel 2 is disposed. The stem channel 2 is made of similar material as that of the housing 1 i.e. steel or any other material that can withstand the detonation shock on its own. The thickness of the stem channel 2 is in the range of 1.25-3.0 mm and having a uniform bore of 3.0-4.0 mm and of 7-28 mm length. The stem channel 2 further comprises of a low friction sensitive primary explosive 4 and a secondary high explosive 3. In the present invention an environment friendly non-azide and non-lead based compound Nickel Hydrazine Nitrate (NHN) 4 is used as a low friction-sensitive primary explosive. RDX (Cyclotrimethylenetrinitramine) 3 is used as the secondary high explosive. The functional contact arrangement of the primary 4 and the secondary explosives 3 within the stem channel 2 is such that the secondary high explosive RDX 3 is placed facing the closed end of the housing whereas the primary explosive 4 is placed adjacent to the secondary explosive 3 on one side and without touching the diaphragm 9 of the squib element on the other side. In between the primary and the secondary explosives 4 and 3 there is no physical barrier separating them. Instead, the primary and the secondary explosives 4 & 3 are pressed one over the other. The loading densities for the RDX and NHN are selected so as to get the required out put effect.

The primary explosive Nickel Hydrazine Nitrate is an energetic coordination compound that has explosive properties in between that of primary and secondary explosives. The friction sensitivity of Nickel Hydrazine Nitrate is 1.6 kgf as compared to Lead Azide which is 0.02 kgf. The particle size of the Nickel Hydrazine Nitrate is in the range of 10-25 microns and the quantity and density of Nickel Hydrazine Nitrate is in the range of 70-160 mg and 1.35-1.45 g/cm respectively. The quantity and density of RDX are in the range of 50-120 mg and 1.55-1.65 g/cm respectively.
Once the squib element is inserted in the open end of the detonator housing 1 over the stem channel 2 which is at the closed end of the detonator housing 1, the housing 1 is crimped 12 at the open end and a suitable resin which acts as a sealing means 13 is applied at the crimped end 12 to yield leak tightness. The sealing means 13 selected from a resin, preferably an epoxy amine resin. Working of the low friction detonator
An electrical current of required rating is provided as an input to the low friction detonator of the present invention. The electrical current is received by the detonator by means of lead wires of the squib element of the detonator. Due to the electrical current the soldered bridge 11 in the lead wires gets heated up. The heat is transmitted from the bridge to the contacting layer of the pyrotechnic charge 8 pressed over the bridge wire 11. This increased temperature results in generation of a flame. The flame that is generated by the squib element is carried to the Nickel Hydrazine Nitrate of the stem channel 2. The flame from the squib element then ignites the primary explosive, Nickel Hydrazine Nitrate in the stem channel 2. When exposed to the flame from the squib the Nickel Hydrazine Nitrate starts burning. The pressure in the burning region continues to rise so as to violently accelerate the burning to the formation of a weak shock wave. This weak shock wave becomes very intense after passing through some run-distance in the Nickel Hydrazine Nitrate column thereby producing a strong shock wave. This process is termed as deflagration-to-detonation transition (DDT) process. Since the output charge, i.e., RDX is pressed in close contact with the Nickel Hydrazine Nitrate, the strong shock wave produced by the Nickel Hydrazine Nitrate causes compression in the adjacent layer of RDX, thereby rising the temperature to many folds instantaneously and which

subsequently causes the required detonation of the secondary high explosive, RDX at the closed end of the housing 1.
The embodiments of the present invention are further explained in the form of the following examples/tests. However, these examples/tests are for illustrative purposes only and should not be construed as limiting the scope of the invention. In order to ascertain the initiating capability of detonator of the present invention, the appropriate tests including, like lead block volume expansion (Trauzl) test, the aluminium witness plate dent test, and full order detonation in mild detonating cord (MDC) are carried out.
Example 1 The working potential of an explosive to perform a defined kind of mechanical work is determined by several parameters such as the amount of gases formed in the reactions, the liberated heat and the detonation velocity. The amount of gases formed in the reactions and the liberated heat is useful in estimating the strength or blasting capacity of the explosive where as the detonation velocity is useful in assessing the shattering effect or brisance of the explosive. Experimentally the strength and the brisance of the explosive can be determined using lead block expansion test (Trauzl test) and plate dent test respectively in the form of a detonator or after giving proper confinement and construction.
The detonator of the present invention was test fired for the volume expansion in lead blocks of a defined quality and size. Lead azide based detonator, which contains RDX as base charge, was used as reference to compare the strength of the detonator of the present invention. The mass of the RDX was the same for the reference as well as for the detonator of the present invention. Lead block test was conducted by placing a detonator of the present invention in the appropriate cavity of the lead block (O 80 x 90) cast at 390-400 °C from soft and qualified lead with no tin or antimony impurities. Dry sand (-150 BSS) was used for stemming the cavity after the insertion of the detonator. After the initiation of the detonator of the present invention, the expansion of the cavity was measured by pouring into it the required volume of water. The net volume expansion obtained from the difference of the cavity volume after and before initiation was found to be 0.8-4.5 cm . These lead block expansion values were matching with the lead azide

based detonators. On the basis of the principle that equal lead block expansion values should be the result of equal works done, it is inferred that both the lead azide based detonator and the detonator of the present invention are having the same strength. Further it is known that the primary explosive, NHN, is capable of initiating full order detonation inRDX.
Example 2 Experimentally the brisance of the explosive can be determined by plate dent test. Plate denting test was conducted by firing a detonator of the present invention into a 40 x 40 x 5 mm qualified aluminum alloy witness plate fixed tightly with the help of a fixture. The hardness of the aluminum alloy is 95 BHN. After the initiation of the detonator, the witness plate was brushed off and the depth of the produced dent was measured using a depth gauge and taken as the measure of the brisance. Also a relative brisance as a ratio between the depths of the dents produced by the detonator of the present invention and the lead azide based detonator was taken. The dent depth was found to be in the range of 2.0 - 3.5 mm besides chips falling out at opposite side of the dent for the reference as well as the detonator of the present invention. On the basis of the plate denting test, it is inferred that the RDX was initiated fully to give maximum detonation velocity.
Example 3
The detonator of the present invention was fired against the mild detonating cord containing RDX at 0.95g/m linear density. By using Explonet-FO-multi channel YOD meter of Kontinitro AG, the velocity of detonation of RDX in the MDC at five positions were measured and found to be 8200 m/s across the length up to 1.6 m tested. This test infers that full order detonation propagation was achieved through out the length of the MDC tested confirming the initiating ability of the detonator of the present invention.
Example 4
The detonators of the present invention were tested for electrical ratings. According to the Bruceton Statistical method thirty numbers each of the detonators of the present invention were subjected to current level which fired 50% of the detonators, for finding no-fire current (NFC) and all-fire current (AFC) ratings. The NFC and AFC were found to be

above 1A and below 3A respectively. From this test it is inferred that the electrical ratings of the detonator of the present invention were of international standard (1A/1W). The detonators of the present invention were safe from all types of stray currents including the human electro static discharge. NFC above 1A means that no detonator of the present invention will be initiated by applying 1A current. AFC below 3 A means that all the detonators of the present invention can be fired by applying the current of 3 A.
Example 5 Four systems were tested to assess the ability of the detonator of the present invention to initiate a detonation in the adjacent explosive train and achieve the assigned task. The systems tested include 1) detonator of the present invention with simulated ETA (Explosive transfer assembly) and measurement of the output as the dent depth in the witness plate. As explained in example 2, the plate denting test is carried for estimating the brisance of an explosive system, namely simulated ETA that contains RDX, initiated by the detonator of the present invention. The short length ETA got initiated fully and under gone full order detonation resulting in the dent depth same as that of one meter long ETA. This test infers that the detonator of the present invention is capable of giving sufficient shock energy to initiate the RDX in short length RDX column.
2) The detonator of the present invention assembled with Thru Bulkhead Initiator (TBI) and simulated ETA was test fired in closed vessel and obtained the specified pressure (Pmax 9 maximum pressure) as output by the combustion of the pyrotechnic composition that is contained in the TBI. For initiating the TBI, which also contains a secondary explosive, an explosive shock is required. In this test the required shock energy was given to the secondary explosive of the TBI through simulated ETA by firing the detonator of the present invention. From this test it is known that the detonator of the present invention can be used in the ignition train of propellant.
3) The detonator of the present invention was assembled in a detonating cartridge with booster (RDX) and test fired in a separation system that uses an elliptical steel tube containing RDX and assessed the output as becoming of the elliptical steel tube into circular after initiation. The elliptical tube will become circular only when the RDX core in the steel tube was initiated fully, which is possible only on the receipt of sufficient explosive shock energy from the detonator of the present invention. From this test it is

inferred that the detonator of the present invention can be used in linear cord based separation systems.
4) The detonator of the present invention was assembled in a detonating cartridge and achieved the output as rupturing'the diaphragm completely of the fire extinguishing bottle. Fire extinguishing bottles are used in aircrafts for extinguishing the fires when engine catches fires. In such emergency situations the diaphragm of the Fire extinguishing bottles should be ruptured rapidly to release the gas to put off the fires. The detonator of the present invention was tested in such system and found opening the diaphragm fully.
The applications for the detonator of the present invention include triggering the high explosive systems, in mining the precious treasures of the earth as well as in quarrying operations and other critical applications where friction-sensitive detonators are used. Advantages
1. The detonator of the present invention wherein the less friction sensitive Nickel Hydrazine Nitrate is used as a primary explosive which results in safe handling during operations like manufacture, transportation and serves to process a detonator safely by replacing the sensitive primary explosive, lead azide (LA), commonly used in conventional detonators, without sacrificing the performance.
2. The detonator of the present invention having a non-lead primary explosive is environment friendly.
3. The detonator of the present invention wherein Nickel Hydrazine Nitrate used as primary explosive is capable of initiating full order detonation in all the high explosive systems tested.



We claim
1. A process-safe detonator, said detonator comprising, a substantially hollow
cylindrical housing with a longitudinal axis, said housing including a closed and an
open end, an initiator unit disposed at the open end of the hollow housing to provide a
hot-wire initiated pyrotechnic charge, a diaphragm, a stem channel extending from
the initiator unit to the closed end of the hollow housing disposed in said housing,
Nickel Hydrazine Nitrate (NHN) acting as a low friction sensitive primary explosive
disposed in said stem channel in proximity to the initiator unit to receive flame from
the pyrotechnic charge of the initiator unit, a secondary high explosive disposed in
functional contact with said Nickel Hydrazine Nitrate, to receive the explosive force
for detonation, and a sealing member disposed on the open end of the hollow housing
for effective sealing of the detonator.
2. The detonator as claimed in claim 1, wherein the secondary explosive used in
conjunction with primary explosive is selected from RDX
(Cyclotrimethylenetrinitramine)orPETN(pentaerythritoltetranitrate),preferablyRDX.
3. The detonator as claimed in claim 1, wherein the friction sensitivity of NHN is 1.6
kgf.
4. The detonator as claimed in claim 1, wherein the particle size of the NHN is in the
range of 10-25 microns.
5. The detonator as claimed in claim 1, wherein the quantity and density of NHN is in
the range of 70-160 mg and 1.35-1.45 g/cm3 respectively.
6. The detonator as claimed in claim 1, wherein the quantity and density of RDX are in the range of 50-120 mg and 1.55-1.65 g/cm3 respectively.
7. The detonator as claimed in claim 1, wherein the material for the sealing member is a resin, preferably an epoxy amine resin.
8. The detonator as claimed in claim 1, wherein the NHN of the deflagration-to-
detonation transition member and the secondary explosive of the output member are
pressed against each other to form a functional contact.


Documents:

797-che-2004-abstract.pdf

797-che-2004-claims duplicate.pdf

797-che-2004-claims original.pdf

797-che-2004-correspondnece-others.pdf

797-che-2004-correspondnece-po.pdf

797-che-2004-description(complete) duplicate.pdf

797-che-2004-description(complete) original.pdf

797-che-2004-drawings.pdf

797-che-2004-form 1.pdf

797-che-2004-form 26.pdf

797-che-2004-form 3.pdf

797-che-2004-form 5.pdf

797-che-2004-other documents.pdf


Patent Number 205207
Indian Patent Application Number 797/CHE/2004
PG Journal Number 26/2007
Publication Date 29-Jun-2007
Grant Date 22-Mar-2007
Date of Filing 11-Aug-2004
Name of Patentee M/S. DEPARTMENT OF SPACE, INDIAN SPACE RESEARCH ORGANISATION
Applicant Address INDIAN SPACE RESEARCH ORGANISATION (ISRO) HEADQUARTERS,,ANTARIKSH BHAVAN,NEW BEL ROAD,,BANGALORE-560094,KARANATAKA
Inventors:
# Inventor's Name Inventor's Address
1 RAVINDRAN MUTHUKUMARASAMY VIKRAM SARABHAI SPACE CENTRE DE3PARTMENT OF SPACE INDIAN SPACE RESEARCHY ORGANISATION (ISRO) TRIVANDRUM KERALA 695 022
2 HARI HARA NATH BODAGALA, VIKRAM SARABHAI SPACE CENTRE DEPARTMENT OF SPACE INDIA SPACE RESEARCH ORGANISATION (ISRO) TRIVANDRUM KERALA 695 022
3 RAJENDRAN AROLICKAL GOPALAN VIKRAM SARABHAI SPACE CENTRE DEPARTMENT OF SPACE INDIA SPACE RESEARCH ORGANISATION (ISRO) TRIVANDRUM KERALA 695 022
4 CHANDRABHANU KANDATHIL SUKUMARAN, VIKRAM SARABHAI SPACE CENTRE DEPARTMENT OF SPACE INDIAN SPACE RESEARCH ORGANISATION (ISRO)TRIVANDRUM KERALA 695 022
5 BHASKARAN KARTHA CHERANELLOOR. VIKRAM SARABHAI SPACE CENTRE DE3PARTMENT OF SPACE INDIAN SPACE RESEARCHY ORGANISATION (ISRO) TRIVANDRUM KERALA 695 022
PCT International Classification Number C 06 C 9/10
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA