Custom engineered, miniature rupture disk assemblies designed for low to high pressure and cycles are ideal for many aerospace applications.
To ensure safety and reliability, aerospace original equipment manufacturers (OEMs) depend on integrated, specific, rupture disk solutions for applications ranging from compressed gas cylinders to propulsion systems, aircraft wheels, environmental and fire protection equipment, and fuel storage systems. Rupture disks serve as an effective passive safety mechanism to protect against overpressure in many such aerospace applications. The disk, which is a one-time-use membrane made of various metals including exotic alloys, is designed to activate within milliseconds when a pre-determined differential pressure is achieved.
Aerospace equipment reliability is essential and demands high integrity from the pressure relief technology used to protect low- and high-pressure OEM systems. Instead of loose rupture disk and holder devices, OEMs are increasingly turning to integrated rupture disk assemblies with all components combined by the manufacturer. These assemblies are tailored to the application, miniaturized, and use a wide range of standard and exotic materials. This approach ensures the rupture disk device performs as expected, enhancing equipment safety, reliability, and longevity while simplifying installation and replacement.
The integrated assembly is also ideal for numerous hydraulic, pneumatic, and other low-, medium- and high-pressure applications including pumps, piston & bladder accumulators, propulsion systems, pressure vessels, and piping.
From satellites to aircraft to drones, tailoring integrated rupture disk applications for use with lightweight, compact materials such as titanium and aluminum are also important since it takes more energy to get heavier vehicles off the ground.
When tremendous corrosion resistance is required for aggressive fluid conditions, titanium is often the material of choice. Where light weight and economy are required, an aluminum welded assembly may be the right solution.
Separate components versus integrated assemblies Traditionally in aerospace, rupture disks begin as standalone components that are combined with the manufacturer's separate holder at the point of use. The installation actions of the user contribute significantly to the function of the rupture disk device. When installed improperly, the rupture disk may not burst at the expected set pressure. There is a delicate balance between the rupture disk membrane, its supporting holder, and the flanged, threaded, or other fastening arrangement used to locate the safety device on the protected equipment.
For this reason, an integrated rupture disk assembly is often a better choice than separable parts. Available ready-to-use and with no assembly required, integrated units are certified as a device to perform at the desired set pressure. The one-piece design allows for easier installation and quick removal if the rupture disk is activated.
The assembly includes the rupture disk and housing and is custom engineered to work with the user's desired interface to the pressurized equipment. The devices are typically threaded or flanged, or even configured for industry specific connections such as CF/KFVCR couplings. The rupture disk and holder are combined by the manufacturer by welding, bolting, tube stub, adhesive bonding, or crimping based on the application conditions and leak tightness requirements.
This approach has additional advantages. Integrated assemblies can be mistake-proofed by design to ensure correct direction of installation such as by use of a different screw thread configuration at the inlet and outlet of the device. The physical characteristics of increasingly miniaturized rupture disks as small as 1/8" can also make it challenging for personnel to pick up the disk and place it into a separate holder.
“Aerospace OEMs are driven to deliver the best performance while respecting the budget of their customers, says Geof Brazier, Managing Director of BS&B Safety Systems Custom Engineered Products Division. “The use of an integral assembly maximizes the quality assurance for the pressure relief technology by providing a ready to use component.”
Integrated assemblies - rupture disk design According to Brazier, the most important considerations in rupture disk device design for aerospace are having the right operating pressure and temperature information along with the dimensional constraints of the application. Service performance is sometimes expressed as the number of cycles the device is expected to endure during its lifetime. Since pressure and cycling varies depending on the application along with the space available and weight that is acceptable, each requires a custom engineered solution.
“Coming up with a good, high reliability, cost-effective, and application specific solution for an aerospace OEM involves selecting the right disk technology, the correct interface (weld, screw threads, compression fittings, single machined part), and the right options as dictated by the codes and standards or end-user validation requirements,” Brazier says.
Because user material selection can also be very specific to the application conditions, rupture disk device can be manufactured from metals and alloys such as stainless steel, nickel, aluminum, Monel, Inconel, titanium, columbium [niobium], and Hastelloy.
For aerospace applications, it can be important for rupture disks to have a miniaturized reverse buckling capability in both standard and exotic materials, Brazier notes.
In almost all cases, reverse-buckling rupture disks are used because they outperform the alternatives in accuracy and resistance to normal operating conditions.
In a reverse-buckling design, the rupture disk’s dome is inverted toward the pressure source. Burst pressure is accurately controlled by a combination of material properties and the shape of the domed structure. By loading the reverse-buckling disk in compression, it can resist operating pressures up to 95% of minimum burst pressure even under pressure-cycling or pulsating conditions. The result is greater longevity, accuracy, and reliability.
“The process industry has relied on reverse-buckling disks for decades. Now the technology is available to aerospace OEMs in miniature form as small as 1/8" burst diameter from BS&B. Until recently, obtaining disks of that size and performance was impossible,” Brazier says.
He adds that the benefits of such miniaturized, reverse-buckling disks include the lowest possible burst pressure ratings in small diameters, enabling low profile, light-weight design, superior performance in cycling service conditions, minimal or no fragmentation upon activation, and the ability to withstand full vacuum or back pressure without extra support components.
However, miniaturization of reverse-buckling technology presents its own unique challenges. To resolve this issue, BS&B created novel structures that control the reversal of the rupture disk to always activate predictably. In this type of design, a line of weakness is also typically placed into the rupture disk structure to define a specific opening flow area when the reverse-type disk activates and retains the disk petal within the assembly housing.
“Reverse buckling – and therefore having the material in compression – does a few things,” Brazier says. “Number one, repeatable structural integrity is achieved. Second, it allows you to obtain a lower burst pressure from thicker materials, which contributes to enhanced accuracy as well as durability.”
Small, nominal size rupture disks are sensitive to the detailed characteristics of the orifice through which they burst. This requires strict control of normal variations in the disk holder.
“With small size pressure relief devices, the influence of every feature of both the rupture disk and its holder is amplified,” Brazier explains. “With the correct design of the holder and the correct rupture disk selection, the customer’s expectations will be achieved and exceeded.”
Because customers are often accustomed to certain types of fittings to integrate into a piping scheme, different connections can be used on the housing. Threading is popular, but BS&B is increasingly using several other connection types to attach the rupture disk assembly to the application. Once the integral assembly leaves the factory, the set pressure is fixed, and the device is ready for use.
“If you rely on someone to put a loose disk in a system and then capture it by threading over the top of it, unless they follow the installation instructions and apply the correct torque value, there is still potential for a leak or the disk may not activate at the designed burst pressure,” Brazier warns. “When welded into an assembly, the rupture disk device is intrinsically leak tight and the set-burst pressure fixed.”
While aerospace OEMs have long relied on rupture disks in their compressed gas, hydraulic and pneumatic equipment, high and low pressure, high-cycling environments have been particularly challenging. Fortunately, with the availability of integrated, miniaturized rupture disk solutions tailored to the application in a variety of standard and exotic materials, aerospace OEMs can significantly enhance equipment safety, compliance, and reliability even in extreme work conditions.
About the author: Jeff Elliott is a Torrance, California-based technical writer who has researched and written about industrial technologies and issues for the past 15 years.
Achieving wastewater treatment compliance Automated wastewater treatment systems help the industry remain in compliance with EPA and local standards, while significantly reducing the cost of treatment, labor, and disposal.
In the manufacture, maintenance, and cleaning of aircraft, the aerospace industry must meet federal Environmental Protection Agency (EPA) and local wastewater requirements for effluent. Failing to do so can result in severe fines that quickly escalate.
Under the Clean Water Act, the EPA has identified 65 pollutants and classes of pollutants as toxic, of which 126 specific substances have been designated priority toxic pollutants.
Typically, manufacturing military or commercial aircraft, jet engines, helicopters, or specialized parts can involve using process rinse water. This can be used while producing, deburring, or finishing aluminum, titanium, or composite parts. Water is also used for plating metals, molding composites, and manufacturing electronics. For example, in defense, to improve wear and tolerance, aerospace components can use cyanide cadmium plating, a process that produces a toxic waste that must be treated.
In addition, in the maintenance and cleaning of aircraft, washing may be used to rid everything from components to aircraft fleets of any dirt, debris, or residues that could degrade performance or aesthetics. For commercial airlines, even running onboard amenities such as toilets and sinks can produce wastewater.
These uses require installing a wastewater treatment system that effectively separates contaminants from the water so it can be legally discharged into sewer systems or even re-used.
However, traditional wastewater treatment systems can be complex, often requiring multiple steps, a variety of chemicals, and a considerable amount of labor. Even when the process is supposedly automated, too often technicians must still monitor the equipment in person. This usually requires oversight of mixing and separation, adding chemicals, and other tasks required to maintain the process. Even then, the water produced can still fall below mandated requirements.
Although paying to have wastewater hauled away is an option, it’s extraordinarily expensive. In contrast, it’s much more cost effective to treat the industrial wastewater at its source, so treated effluent can go into a sewer and treated sludge passes a toxicity characteristics leaching procedure (TCLP) test and can be disposed of as non-hazardous waste in a local landfill.
Fortunately, complying with EPA and local wastewater regulation has become much easier with fully automated wastewater treatment systems. Such systems not only reliably meet regulatory wastewater requirements, but also significantly reduce the cost of treatment, labor, and disposal when the proper Cleartreat® separating agents are also used.
Automated wastewater treatment In contrast to labor-intensive multiple-step processes, automated wastewater treatment can help to streamline production, usually with a one-step process, while lowering costs.
An automated wastewater treatment system can eliminate the need to monitor equipment in person while complying with EPA and locally mandated requirements. Such automated systems separate suspended solids, emulsified oil, and heavy metals, and encapsulate the contaminants, producing an easily de-waterable sludge in minutes, according to aerospace industry consultants at Sabo Industrial Corp., a New York-based manufacturer, distributor, and integrator of industrial waste treatment equipment and solutions, including batch and fully automated systems, Cleartreat separating agents, bag filters, and accessories.
The water is separated using a de-watering table or bag filters before it is discharged into sewer systems or further filtered for re-use as process water. Other options for de-watering include using a filter press or rotary drum vacuum. The resulting solids are non-leachable and are considered non-hazardous, so will pass all required testing.
These systems are available as manual batch processors, semi-automatic, automatic, and can be designed as a closed-loop system for water reuse or provide a legally dischargeable effluent suitable for the sewer system. A new, fully customized system is not always required. In many cases, it can be faster and more cost effective to add to or modify a facility’s current wastewater treatment systems when this is feasible.
However, because every wastewater stream is unique to its industry and application, each wastewater treatment solution must be suited to or specifically tailored to the application. The first step in evaluating the potential cost savings and effectiveness of a new system is to sample the wastewater to determine its chemical make-up, followed by a full review of local water authority requirements, say aerospace industry consultants at Sabo Industrial.
The volume of wastewater to be treated is also analyzed, to determine if a batch unit or flow-through system is required. Other considerations include size restrictions, to make sure the system fits within the facility’s available footprint.
Separating agents Despite all the advances in automating wastewater treatment equipment, any such system requires effective separating agents to agglomerate with wastewater solids so they can be safely and effectively separated out.
Because of the importance of separating agents for wastewater treatment, Sabo Industrial uses a special type of bentonite clay in its ClearTreat line of wastewater treatment chemicals. These wastewater treatment chemicals are formulated to break oil and water emulsion, provide heavy metals removal, and promote flocculation, agglomeration, and suspended solids removal.
Bentonite has a large specific surface area with a net negative charge that makes it a particularly effective adsorbent and ion exchange for wastewater treatment applications to remove heavy metals, organic pollutants, nutrients, etc. Bentonite is essential to effectively encapsulate these materials, which can usually be achieved in one-step treatment, lowering process and disposal costs.
In contrast, systems that use polymer-based products do not encapsulate the toxins, so are more prone to having waste products leach out through time or upon further agitation.
Today’s automated systems, along with the most effective Cleartreat separating agents, can provide industrial facilities with an easy, cost-effective alternative so they remain compliant with local ordinances and the EPA. Although there is a cost to these systems, they don’t require much attention and can easily be more economical than paying fines or hauling.
Adds unclassified satellite line for national defense.
L3Harris Technologies is expanding its satellite production site to include advanced production of unclassified satellites, which will deliver experimental capabilities for national defense.
The Central Florida location is home to more than 100,000ft2 of space used for development, manufacturing, and testing of full satellites and components which already deliver complex, classified capabilities for national defense. The increased production capability allows L3Harris to develop and test the experimental Navigation Technology Satellite-3 (NTS-3), which is a priority program for the U.S. Air Force. Facility investments also make it possible to develop and integrate three sizes of small-to-medium responsive satellites in support of urgent U.S. Department of Defense missions addressing evolving threats.
“Our customers face urgent threats that must be addressed in months rather than years,” said Ed Zoiss, president of L3Harris Space and Airborne Systems. “We prioritized facility investments to meet their accelerating timelines.”
Two of the company’s eight buildings have recently been upgraded to manufacture multiple end-to-end satellites per month. L3Harris has built eight satellites at the expanded Palm Bay facility that are currently on orbit and another 10 are in various stages of development. The company plans to add more production capacity by the end of the year to produce six satellites per month.
VITA increases satellite payload capacity, helping propel satellites to final orbit and maintain their orbital position.
Power management company Eaton has successfully completed qualification testing for the aerospace industry’s first Valve in Tank Assembly (VITA) propulsion feed system. As the first satellite electric propulsion solution that integrates valves inside the propellant tank, the VITA eliminates the need for a traditional feed system envelope, creating room for more payload.
“Our VITA can help transform the satellite industry,” said Craig Ryan, integrated product team director, Space Systems, Eaton’s Aerospace Group. “The efficient design of the VITA feed system requires less space on the satellite bus, plus it saves integrators significant procurement, assembly, testing, troubleshooting, and rework effort.”
VITA will play a critical role in helping propel satellites to final orbit and in station-keeping to maintain orbital position. By enabling additional payload flexibility and control over which type of fuel can be included on a satellite mission, the VITA design supports the growing satellite industry, especially in the highly competitive area of small satellite providers.
“We have the infrastructure to quickly meet high demand volume and are currently taking orders,” said Ryan. “We look forward to supporting the success of a wide range of leaders and emerging innovators in the rapidly growing satellite market.”
The innovative design of Eaton’s VITA eliminates the feed system envelope by integrating proportional flow valve technology into a housing that is then integrated into the neck of a lightweight composite propellant tank. The initial configuration of the VITA solution has two redundant shut-off valves to support one thruster for increased reliability. The drop-in VITA design approach supports modular satellite configurations, making architectural changes easier. Qualified in testing with xenon, this system has demonstrated to be fully compatible with krypton as well. The valve and tank assembly can be pre-filled with propellant and shipped ready to install.
Eaton’s space propulsion technologies include tanks, valves, regulators, and feed systems to provide customized solutions to meet customer requirements.
The award, which is in its third year, recognizes groundbreaking design innovation in engineered fasteners.
Multi Piece Fastener has won a 2021 Fastener Innovation Award for its ForeverLok™ fastener design from Worldwide Fastener Sources.com, a comprehensive source for fasteners globally.
The award, which is in its third year, recognizes groundbreaking design innovation in engineered fasteners today that will become a standard in future years. The Fastener Innovation Award is one of three prestigious awards in the fastener industry, along with the Soaring Eagle Awards from the Industrial Fastener Institute (IFI), and the Fastener Hall of Fame awards from the International Fastener Expo (IFE).
“It is an honor to be named a winner of the Fastener Innovation Award,” said Earl Size, Founder of Multi Piece Fastener. “As engineers incorporate innovative fasteners as part of the design process to solve challenging issues of vibration, we are proud to be part of the solution.”
In industries such as aerospace, marine, defense, construction, heavy equipment, oil and gas production, wind turbines, and automotive, tremendous repetitive forces contribute to fastener self-loosening. To prevent such self-loosening, the ForeverLok design involves three items: a central threaded fastener, a threaded intermediate fastener, and a retaining fastener. Essentially, the fastener system holds the nut in place to physically prevent it from loosening. The locking design does not use special pins, bolts, or tools to install or remove the nut. Only common tools are needed to fasten/unfasten.
The ForeverLoK™ design is available for licensing. For more information, contact Multi Piece Fastener at (248) 928-9602 or write to sales@multipiecefastener.com.