Low Shock and Positive Isolation with both Liquid and Gas Lines
EBAD’s highly reliable Hold Down & Release Mechanisms technology has been adapted for use in Non-Pyrotechnic Valves. The electrically redundant valves offer low shock and positive isolation with both liquid and gas lines. They are available in both normally closed and normally open configurations.
Principle of Operation
The NEA® Non-Pyrotechnic Valves consist of a spring-loaded plunger that is restrained using the same patented split-spool and fuse wire technology used in our Hold Down & Release Mechanisms. The spool subassembly includes two spool halves which are held together by a tight winding of a restraining wire that terminates in a fuse wire connecting two electrical terminals at the electrical interface to the device. The spool assembly, by virtue of the restraining wire winding, can prevent axial motion of the plunger. When sufficient electrical current is passed through the terminals and the fuse wire, the fuse wire heats up and breaks under the applied tension load. This allows the restraining wire to unwind, separating the spool halves and releasing the spring-preloaded plunger, which is directly connected to a ball and cone valve mechanism. Actuation can either separate the ball from the cone or engage the ball in the cone depending on the configuration selected.
The actuation method is simple and reliable and forms the basis of actuation for many of EBAD’s other products including; Battery Cell Bypass Switches and Pin Pullers.
The Non-Pyrotechnic Valves are most suited to one shot applications that are inaccessible and require maximum reliability such as:
- Spacecraft fuel lines
- Nuclear coolant valves
- Tamper proof hydraulic valves for security applications
- Electrically Redundant
- Low Shock
- Positive Isolation
- Available in normally closed or open configurations
- Hermetically-sealed designs are available
- Post actuation contamination: <15 items and <25 microns
- Predictable Actuation Times
- Material selections compatible with gas and liquid mediums
EBAD release device technology provides significant advantages.
Low Shock — There are three sources of shock with traditional pyrotechnic release devices; those include the pyrotechnic initiator and the resulting transfer of kinetic energy within the mechanism. The EBAD approach eliminates both of these sources of shock. There is no pyrotechnic initiator required so there is no initial shock and the restraint wire release mechanism is also not a significant contributor to shock.
A third source of shock is the energy stored in the release rod itself as well as any of the other components that are in the preload path. The nature of EBAD device’s gentle release of preload allows this stored energy to be dissipated over the release event minimizing the stored energy contribution to shock as well.
Fast Acting — With respect to shock, the action of EBAD devices is quite gentle yet the release event itself is still very fast. Since the fuse wire is extremely small the release event can be triggered in milliseconds. This capability allows multiple EBAD devices to be used in parallel where simultaneous release is required, such as large solar array panels and spacecraft stage separations.
Reliable —With simplicity comes reliability. The basic design of the NEA® HDRM is very simple with a minimum of moving components. The devices are robust and not sensitive to extreme environments or contaminants. High reliability is supported both analytically and by an extensive history of successful operation in mission critical applications.
Light Weight — EBAD devices offer extremely high preload release capacities versus unit mass. Some NEA® HDRM models have specific preload release capacities greater than 300N/g.
Temperature Insensitive — The simplicity of the EBAD release device mechanism is an asset not just for reliability but also with respect to temperature sensitivity. NEA® HDRMs are insensitive to extreme temperatures. Specific NEA® HDRMs have been qualified for operation at temperatures as low as 25K. The extreme low mass of the fuse wire results in actuation performance that insensitive to initial conditions.
Low Risk — NEA® HDRMs have an extensive history of use on a broad variety of spaceflight applications and are currently the baseline release device of choice on most major spacecraft buses. This history of reliability and mission success makes the NEA® HDRM our customers’ low risk option.
Compatible — NEA® HDRM devices have been designed to work with existing pyro firing circuits. The flexibility of the design however also allows operation with lower firing current if required.
In addition to our line of standard Non-Pyrotechnic Valves, NEA® can provide custom configurations that include: modifications to the mechanical interface, modified housing designs, changes to lead wires, revisions to pressure capability, additional connector housings, and materials changes. NEA® can also provide Non-Pyrotechnic Valves as part of a next higher assembly either built to our customer’s prints or designed at NEA® to our customer’s specifications. Many of our current customers rely on NEA®’s in-house engineering expertise to integrate our market leading split-spool Non-Pyrotechnic Valve technology into custom assemblies to improve their competitive edge.
For more information:
Model NPV9000 Mechanical Interface Drawing
Typical HDRM Actuation Curve
A typical HDRM actuation curve showing the actuation time as a function of the actuation current is presented below. Please contact our applications engineers for specific curves for each product.
|Model||Burst Pressure (5 minutes)||Maximum Operational Pressure||Minimum Operational Pressure||Minimum Actuation Current1||Actuation Time2||Cold Temperature Limit||Hot Temperature Limit||Mass3||Data Sheet|
|NPV9000||63.4 MPa (9,200 psi)||31 MPa (4,500 psi)||0 MPa (0 psi)||2 A||30 ms||-257°C (16 K)||+160°C||496.5 g||Download PDF|
1 Actuation can be achieved using a range of current, the value in the table is the value used for qualifying this device.
2 Actuation time is dependent on actuation current, contact applications engineering for more specific information on actuation time as a function of current.3 Actuation time is a function of actuation current, contact applications engineering for actuation time as a function of current curves.
3 Mass does not include harnessing and lead wires.