Kearflex Engineering Co.

Complex Assemblies Kearflex manufactures complex assemblies that are based upon our capsule sub-assemblies. These are sold to our customers to allow efficient installation in the next level assembly. Advantages to this approach are a “turn-key” product where the capsule related problems are solved and specialty manufacturing is performed. Customers can use these assemblies on a ship to stock basis with confidence that each unit is calibrated and interchangeable. Inspection and test activities, process fallout and specialty manufacturing efforts are all reduced. Closed loop calibration feedback from our customers allows the performance characteristics of the assembly to be optimized providing the best results in the finished product. Annual and blanket contract arrangements allow for just in time delivery, as well as demand pull formats. Reverse Engineering These complex assemblies can be provided on a build to specification basis, but it is usually more practical to reverse engineer the product and adapt the design to known and active Kearflex practices and processes. This is applicable to end of life situations where internal or external vendors have ceased to exist, or abandoned products. It is very common for there to be references to unavailable or inapplicable documents such as proprietary process instructions, obsolete engineering specifications and vendor specific test equipment procedures. The design can be converted to use existing Kearflex processes for welding, brazing, soldering and external processes such as plating, and anodizing. A good portion of the designs can be qualified by similarity, as these adaptations are based upon flight qualified practices that are in active and continuous use with similar products. It is worth noting that the legacy products of this type were all designed around the same time and used similar practices that differed with the particular manufacturer. The conversion to Kearflex practices represents a low design risk and a great deal of similarity to the original products.

FULL INSTRUMENTS Altitude Pressure vs Altitude This instrument uses an aneroid capsule assembly to measure the atmospheric pressure outside of an aircraft. The pressure at a given altitude is a function of the air supported above that point where the force is caused by gravity. As the column of air is taller closer to earth, there is more pressure. However, this is not a linear progression due to the fact that air is compressible. Altitude Pressure Chart Altitude Pressure Chart The Altitude Pressure Chart provides a visual representation of what the instrument must be calibrated to measure. There are only very slight changes in pressure past 30, 000 feet. The nature of an altitude instrument requires a great deal of sensitivity as the atmospheric air pressure approaches a vacuum. Aneroid Capsule The aneroid capsule assembly has a deep vacuum trapped inside, and measures the difference between the atmosphere outside of the aircraft, and this nearly perfect vacuum. The internal vacuum is constant and provides the reference pressure that the capsule uses to measure altitude. Temperature Effect An important consideration is temperature. Heat reduces the density of air resulting in a lower pressure due to the force of gravity. To know the true altitude, both the atmospheric pressure and the ambient temperature would be required. This class of altitude instrument is not temperature compensated. This does not invalidate the usefulness of this instrument - the temperature of the atmosphere gets colder, and is more predictable as altitude increases above 10, 000 feet. Operating from 20, 000 to 50, 000, the instrument will be accurate. As the aircraft approaches an airport the controller will advise the "temperature altitude" at the runway. In Denver during the summer, this value can be as high as 9, 000 feet. The pilot knows that when his altitude instrument indicates 11, 000 feet, the aircraft is really 2, 000 feet above the ground. Instrument Application This type of altitude instrument is not usually used for primary flight in newer general aviation. Contemporary microprocessor based altimeters, and radar altimeters coupled with heads up and in dash displays provide for more accuracy without other considerations on the part of the pilot. These instruments remain in the aircraft for emergency use, and in the hands of a skilled pilot will still allow for a safe landing. Other applications include balloons and ultra-light aircraft where un-powered mechanical instruments would be attractive.Airspeed Differential Pressure vs Airspeed This instrument uses a capsule assembly to measure the differential pressure produced by a pitot static tube mounted outside of the aircraft. The pressure at a given airspeed is a function of the impact pressure of the air hitting the aircraft, and the ambient pressure surrounding the aircraft. However, this is not a linear progression due to the fact that impact force is a function of kinetic energy which has a square function. Airspeed Pressure Chart Airspeed Pressure Chart The Airspeed Pressure Chart provides a visual representation of what the instrument must be calibrated to measure. There are only very slight changes in pressure below 50 knots. The nature of an airspeed instrument requires a great deal of sensitivity at low speeds.Differential Capsule The differential capsule assembly measures the difference between the impact pressure at the tip of a pitot tube, and the atmospheric pressure outside of the aircraft. If the aircraft is stationary with no impact pressure, the differential capsule will indicate zero at any altitude - this is because the ambient pressure is applied equally to both sides of the sensor. Altitude and Temperature Effect A consideration is altitude and temperature. Both heat and altitude reduce the density of air resulting in a lower impact pressure, and a reduced indicated airspeed. This class of altitude instrument is not temperature or altitude compensated. This does not reduce the usefulness of this instrument. Because the wing requires more airspeed to generate lift in less dense air, the indicated airspeed is very important - the plane will stall at the same indicated airspeed at any temperature altitude. At low altitudes during takeoff and landing, the errors are small. Glass Cockpit with legacy Altitude and Airspeed Instrument Application This type of airspeed instrument is not usually used for primary flight in newer general aviation. Contemporary microprocessor based air data computers, and radar sensors coupled with heads up and in dash displays, provide far more accuracy without other considerations on the part of the pilot. These instruments remain in the aircraft for emergency use, and in the hands of a skilled pilot will still allow for a safe landing.Other applications include balloons and ultra-light aircraft where un-powered mechanical instruments would be attractive. Vertical Speed Instrument Vertical Speed Differential Pressure Generated by Time Delay This instrument uses a capsule assembly to measure the differential pressure produced by changes in altitude. The differential pressure is created by measuring two volumes - one attached directly the atmosphere outside the aircraft, and the other attached via a restrictor. The restrictor makes the second volume respond slowly to changes in pressure, which are the result of changes in altitude. This time lag is directly related to the altitude rate of change.

Aneroid Capsule The aneroid capsule assembly has a deep vacuum trapped inside, and measures the difference between the atmosphere outside of the assembly and this nearly perfect vacuum. The internal vacuum is constant and provides the reference pressure that the capsule uses to measure altitude. Note the collapsed condition of the altitude capsule compared to the airspeed capsule. The atmospheric pressure is pressing on the assembly which has an internal vacuum. Increasing altitude up to the near vacuum at 40, 000 feet, the capsule will expand to nearly the same profile as the airspeed assembly. Both capsules measure a differential pressure and are neutral when the difference is at or near zero. For the aneroid, this occurs when exposed to a vacuum, and for the airspeed, this occurs when the inside and the outside pressure are equal. The aneroid capsule is used in measurement of the aircraft altitude, and for the cabin pressure. Differential Capsule The differential capsule measures the pressure outside the assembly with respect to the inside of the assembly. It operates as an analog computer in that any pressure applied equally to both sides of the capsule will result in zero deflection. In application, an airspeed capsule measures the difference between the impact pressure at the tip of a pitot tube and the static air pressure surrounding the side of the tube. The differential capsule ignores the altitude of the aircraft because this is applied to both sides equally. A stationary aircraft at sea level or in Denver will both have a zero differential. Principal of Operation In all cases, diaphragm based capsules convert a differential pressure to a displacement. It is important to remember that an aneroid is still a differential pressure measurement, with the special characteristic being that internally this value is held at zero, or full vacuum. Mechanically, the diaphragm functions the same way in sealed and un-sealed assemblies. Aneroid Note the natural direction of deflection is collapsing with the external air pressing against the internal vacuum. Differential Capsule Graphic Differential Note the natural direction of deflection is expanding with the internal air pressure exceeding the external air pressure. The direction of pressure application can be reversed so that the capsule would collapse on differential pressure. In addition, the higher pressure can be applied both internally and externally for a bi-directional deflection. This is how the capsule is used in the Altitude Rate of Change instrument – the applied differential is used for both climb and decent, and the capsule moves in both directions. Altitude Compensated Airspeed The altitude compensated airspeed capsule is a clever analog computer that provides a pitot static airspeed reading that is corrected for changes in altitude. Assuming that an aircraft was traveling at a constant 350 knots and went from 10, 000 feet to 30, 000 feet in altitude, the pitot static pressure would drop due to the lower density of the air at the higher altitude. This would cause the differential pressure capsule to collapse. At the same time, the smaller altitude capsule mounted on top of the differential would expand due to the lower pressures at the higher altitude. The altitude and airspeed capsules are approximately matched so that the overall travel is opposed and equal. The primary application for this assembly is in ejection seats. A single switch can be used to trip when the pilot is both below a specific altitude and a specific airspeed. The parachute must not deploy at high speed which would injure the pilot, or at too high an altitude where it would be too cold. This little analog computer is very powerful – it is small and non-electronic.

Altitude Switches Kearflex incorporates our diaphragms and capsule assemblies into altitude switches. In the altitude switch, the sensing element has a permanent vacuum trapped inside to allow the switch to respond to atmospheric pressure. The pressure port and housing can be configured to meet the customer needs. Airspeed Switch Airspeed Switches Kearflex integrates our diaphragms and capsule assemblies into airspeed switches. In the airspeed switch, the sensing element applies pressure to both sides allowing measurement of the pitot and static pressure signal. The pressure port and housing can be configured to meet the customer needs. Process Monitoring Switches Absolute Pressure Kearflex designs our diaphragms and capsule assemblies into absolute pressure (Psia) switches. In the absolute switch, the sensing element has a permanent vacuum trapped inside that provides a reference for the measurement. These are configured the same way as the altitude switches, but can be calibrated as required for Psia switch points. Applications include vacuum systems and monitoring sealed tanks such as fuel, water or waste. Differential Pressure Kearflex incorporates our diaphragms and capsule assemblies into differential pressure (Psid) switches. In the differential switch, the sensing element applies pressure to both sides allowing measurement of closed systems. These are configured the same way as the airspeed switches, but can be calibrated as required for differential pressure switch points. Applications include cabin pressure systems, air filter pressure drop monitoring and closed tank level monitoring. Gauge Pressure Kearflex integrates our diaphragms and capsule assemblies into gauge pressure (Psig) switches. In the gauge switch, the sensing element applies pressure to one side, and the other side is open to ambient. These are configured the same way as the differential switches, but can be calibrated as required for gauge pressure switch points with only one connection required. Applications include air pump output, bleed air systems and instrument supply air.

Mechanical Movements Mechanical movements amplify the displacement of the diaphragm to turn a pointer providing pressure indication. Specific advantages of the Kearflex Diaphragms: Ranges: 1 Psi to 400 Psi Linearity: 1% of full scale Consistent: 1% or less variance within a lot Hysteresis: 0.5% or less Materials: 316L, Nispan, Inconel, Hastelloy, or any available material that is formable. Note: The size of the diaphragm is based pressure range. 1.125 Inch Diameter: 10 Psi to 400 Psi 1.375 Inch Diameter: 10 Psi to 75 Psi 1.590 Inch Diameter: 10 Psi to 50 Psi 2.000 Inch Diameter: 5 Psi to 50 Psi 2.375 Inch Diameter: 1 Psi to 25 Psi Small Mechanical Gauge Using the small 1.125 inch diameter diaphragm, this mechanical gauge can be calibrated in ranges from 10 Psi to 400 Psi. A range of diaphragms is used providing the same deflection at the specified full scale pressure. This allows the mechanical movement and all other parts except the faceplate to be common for all ranges.

ANSI B16.5 Process Flange These are a very common type of flange used throughout the process industry. They bolt into the side of tanks, pressure vessels and piping systems. The flanges are available in Class 150, 300, 450 and 600, which allow operating pressures up to 1, 580 Psi. In level applications, the weight of the liquid above a point creates a pressure that is measured by the diaphragm based sensor. The density of the liquid needs to be known, and this type of measurement is suitable for liquids that are corrosive, have extreme temperature and contain solids. The flange assemblies can be liquid filled where the diaphragm isolates a delicate sense element, or direct where the diaphragm displacement is calibrated and the motion is used to measure level. ANSI Flange Cutaway Isolation Diaphragms Kearflex offers a line of diaphragms specifically used for isolation applications. This is where there is a fluid fill behind the diaphragm which trasmits pressure to a remote, or "isolated" sensor. The sensor can be of any type including strain, gauge, piezo, capacitive, inductive and optic. Direct Acting Switch In a direct acting assembly the diaphragm displacement with respect to pressure, and therefore level, is calibrated. The diaphragm acts like a linear spring and will move a known distance with pressure, and this displacement can be converted into level. The diagram shows a simple level switch. This direct acting switch has several advantages. No Liquid Fill There is no liquid fill as used with isolation diaphragms, and therefore no possibility of contaminating a critical process in the event a diaphragm is damaged. Very Sensitive Diaphragms A very sensitive diaphragm can be used which can detect down to a few inches of liquid. This allows quick detection if mounted in a spill containment vessel, or overfill protection if mounted at the top of a storage vessel. Alternative Technology The switch is not electronic or microprocessor based - it will remain operational in the event of electrical or electronic interference, and is a suitable backup of other technologies.