Proper design requires knowledge of valve types
By William Miller, Humphrey Products
Valves used in the medical device industry are designed with precise specifications so they are compatible with the requirements of the applications. Meanwhile, valves used in factory automation are designed to work within specific safety regulations. Every project has unique requirements and choosing the best pneumatic valve design for your application will provide optimum results.
While each design has its strengths and weakness to be considered, knowing your application’s requirements is essential. For example, the media of the application varies between industries. Compressed air and other gases can be extremely powerful—even fatal—so understanding how the valve will be used is important. Certain valve designs are compatible but limited by specific media. Some other factors that dictate the required valve are the external variables such as temperature range of the application, and purity of the air or media (moisture, contamination). Once you know the critical requirements for the application, the valve design can be chosen based on its specific features.
Poppet-design valves
Poppet-design valves use a rubber molded poppet wrapped around the stem that moves along the bore of the valve, creating a seal when the poppet is in its seat. One specific advantage to using a valve with this type of internal design is the compatibility with a variety of media other than compressed air. The unique feature that allows this compatibility is less lubrication sensitivity due to few sliding parts or (dynamic seals).
Another benefit to this poppet design is that the valves are more tolerant of minor air sediment or debris. They also have excellent exhaust capacity and are capable of high flow rates. The poppet design provides a faster response rate due to short stroke and can be mounted in several ways.
Poppet valves more readily lend themselves to 2-or 3-way configurations, although 4-way configurations can be achieved by using dual 3-way poppet sets in one valve body. Poppet valves are typically unbalanced designs, which use the air pressure as the primary force to return the valve to a given position. This concept provides assurances that the valve will return to the desired position, even if the return spring fails. Balanced poppet valves are used to reduce actuation force and achieve lower current consumption in solenoid valves. Balanced valves typically provide smaller overall physical size and produce greater flow capacity.
Applications in which this design are most commonly found are in the medical device and analytical instrumentation industries, where air purity is required (absence of dirty or wet media/air), the need for reliability is mandatory (could be saving lives), low leakage rate is critical, and gases other than compressed air will be used as a medium.
Diaphragm-poppet design valves
Diaphragm-poppet design valves expand the poppet valves’ design by the use of a diaphragm. Its outer webbing guides the poppet to its seat without using sliding seals. Diaphragm-poppet designs are usually unbalanced providing the same assurance of return to a given position as the poppet valve. The diaphragm increases durability especially with different or non-lubricated media.
A variety of durameter and diaphragm compounds make it simple to modify a valve based on the environmental or application requirements for operation. Also, expect extremely low leak rates due to strong sealing control. Diaphragm-poppet valves make 2-way or 3-way configurations available, as well as the possibility of 4-way valves, by using dual 3-way diaphragm poppet sets in one valve body. This valve’s durability and reliability make it a great candidate for applications such as critical life support devices (e.g. heart ventricular support assistance or pulmonary supply devices).
Its non-lubrication capability makes it appealing to be used with devices used for respiratory and anesthesia gases. Diaphragm-poppet designs are great solutions in leak testing devices, due to the very low leak rate. Lastly, these designs are suitable for critical or contaminated vacuum applications.
Spoppet-design valves
Spoppet-design valves combine two designs to provide a blend of primary poppet sealing in conjunction with a minimal number of sliding seals, thus emulating characteristics of a poppet and spool valve design. Spoppet designs retain some unbalance characteristics but with some balance of pressure to reduce actuation forces. This design provides the benefits of the poppet valve with a reduced sensitivity to lubrication.
Only one sliding seal engaged at a time reduces the drag within the valve body. These designs can sometimes bridge the gaps or limitations of poppet and spool valves making them more useable in numerous critical applications. By blending the designs, spoppets provide more cost efficient 3-way and 4-way valves, and can be used in many different environments and applications.
Spool-design valves
Spool-design valves are available in three types: lapped-/shear-design with no seals, dynamic seals, or O-rings. Spool valves are designed to be more cost-effective when manufacturing for 4-way valves and are conversely less adaptable for 2-or 3-way configurations. Spool valves can be either balanced or unbalanced, depending on desired position control required. Therefore, understanding this valves’ function is critical to the application requirements. Lapped- or shear-design spool valves can operate without lubrication but are less tolerant of variations in lubrication or by-products of compressing the air at the air compressor. Hence, further conditioning of the compressed air is required prior to use.
Dynamic seal spool valves generally require lubrication. Lapped spool valves have higher leak rates that may make them unacceptable for control of medias other than air, or limited media sources (air/gas tanks/bottles). Consequently, these valve designs are better suited to applications in factory automation where the leak rates are not critical. The requirement for conditioned media also limits their use for vacuum where contaminates are ingested into the vacuum lines and valves.
Custom-designed valves
Custom-designed valves are becoming more common, using a combination of the fore-mentioned design technologies to provide solutions unique to the customers’ challenges. In a perfect world, off-the-shelf components would meet every application’s need. But that doesn’t often happen, especially when faced with trade-offs such as space constraints versus performance. Sometimes a complex solution is needed, such as squeezing multiple components into a small space or incorporating multiple valve designs for a solution.
Custom designs using known and proven design technologies offer the potential of lower cost pneumatic systems. Once the specifications are agreed upon with the manufacturer’s design engineers and the application’s product engineers, a custom designed solution may be the best way to meet the applications’ challenges if a specific design is close but not does not meet exact specifications.
Ultimately when it comes to valves, each design technology offers unique capabilities but not every design suits specific applications. No matter whether you are replacing a component or designing a pneumatic system, consult a valve manufacturer who has knowledge in many different design principles so that the best solution can be achieved.
New valve catalog from Humphrey Products
Humphrey Products has released its newest Valve Catalog, HKV-7, for distribution. The new catalog provides basic decision-making information about our broad range of valve products. Within each of the eight sections, there are pages devoted to valve fundamentals, principles and background information, along with a comprehensive index to quickly navigate to the best solution. The ultimate goal of the catalog is to provide an overview of our products, guiding the customer to www.humphrey-products.com for more information.
Once at the website, the customer can access an Online Product Guide, which provides more detailed specifications, CAD drawings, how to order information, and the ability to request a quote for the product. Additionally, the new catalog can be viewed as an interactive PDF.
iB Series features digital pneumatic flow controller
Koganei and Humphrey introduce the iB Series, which includes the iB Move and the iB Flow. The iB Move is a Linear Stepper Motor Actuator which boasts high speed yet quiet operation for lightweight work—in an affordable design. The iB Flow is a digital flow controller that optimizes the cycle time settings of a cylinder or pneumatic actuator.
iB Move
A new value category of electrical motion—the iB Move is suitable for those applications where pneumatic cylinders are insufficient (too slow, too noisy, too dirty, or need acceleration/decal functioning), while traditional electric linear actuators are too costly. iB Move is perfect for small, compact positioning applications requiring movements of less than 2 in.
Special features include:
- Easy Operation
- Easy to pre-set/program
- Low Price / Great value
- Silent and Clean
- Compact – Small size
The iB Move features a newly developed and unique shaft-type, Linear Stepper Motor Actuator. iB Move is:
- Simple, using 2-phase open loop control, to accomplish cost reduction objectives.
- Utilizes a Moving Magnet principle (2-phase stepping “Moving Magnet” method is fixed electromagnets (coils) while permanent magnets move).
- Direct drive – Does not use a ball screw, belt, or gear, so backlash is avoided, and a high level of silence achieved.
- Easy to program, requiring little training.
- Quiet Operation – No exhaust noise as with pneumatic cylinders, nor the sliding noise of ball screw & linear guide.
- Low price, despite being an electric linear motor.
iB Flow
The iB Flow is a digital pneumatic flow controller, creating an alternative to the traditional “manual” speed controller. The iB Flow features two electronic needle settings, either based on percent open, or based on cylinder extending and retracting times, both much more accurate and repeatable than the manual speed controller. Once set, the iB Flow has a safety-lock mechanism, preventing the needle from any adjustment. Plus, its “copy” function allows for setting speeds on multiple cylinders quickly and accurately, thereby reducing machine set-up time.
Applications for the iB Flow:
- Air cylinder operation time adjustment.
- Simultaneous operation of multiple cylinders.
- Precision flow adjustment during vacuum breaking.
- Precision flow adjustment during air blow-off.
- Monitoring actual versus previously programmed settings (due to cylinder wear or friction changes).
Humphrey Products Receives ISO-13485 Accreditation
June 23, 2010 by admin
Filed under Actuators, Equipment, Industry News, Valves
Kalamazoo, MI — Humphrey Products is proud to announce that it received the accreditation for ISO 13485: 2003 in addition to its continued accreditation of ISO 9001 status. ISO 13485 represents the requirements that medical device manufacturers must incorporate into their management, engineering, distribution and quality systems.
Adding to all the normal benefits that the ISO 9001 registration provides customers and distribution, ISO-13485 certification provides the system controls, serialization, process change controls and notification that are currently required for products used and sold within medical markets.
“The medical market is a huge and all encompassing category and can cover many and varied applications,” said Robert Humphrey, President and CEO of Humphrey Products, “anywhere from process equipment used in the automated preparation and evaluation of biopsy materials on test slides, to those applications such as oxygen concentrators used by the patient within their own homes, or all the way into the ER, and patient invasive devices used by surgeons to assist with various medical procedures.”
Humphrey Products
www.humphrey-products.com
Humphrey Products 410M Series Manifold
The Humphrey Products 410M Series Manifold is designed to accommodate the standard 310 and 410 inline solenoid valves. This special design enables mounting both 3-way and 4-way valves on the same manifold, with the 310 Series mounting orientation determining the normally closed (NC) or normally open (NO) function. Manifolds are available in 2, 4, 6, 8 or 12 station lengths. The manifold contains two galleys, one is common media supply port and the other is a common vent/exhaust port. Other accessories include manifold station block-off plates, a separate 12-station control board that simplifies electrical connections between valves and/or sensors.
The Humphrey Products 310 and 410 solenoid valves are versatile, robust components for any pneumatic application. This balanced poppet design makes them ideal for low power and high flow applications. The 310 and 410 Series valves are compact 1/8-inch ported 3-way and 4-way direct acting solenoid valves. The short-stroke balanced poppet design permits rapid cycling and requires no lubrication. The 310 series can be plumbed normally open, normally closed or as a selector or diverter.
The 310 Series valves have a 0.12 CV; the 410 Series valves have a 0.14 CV. Both valves are rated for air and inert gas from vacuum at 28-inches Hg to 125 psig. The continuous duty coil has a power consumption of 4.5 Watts, comes with flying leads and is available in a range of AC and DC voltages. A push, non-locking manual override is standard. Options include conduit connectors, plug-in DIN-type connectors, locking override, and built-in flow controls on the 410 Series valves to save space, weight and the additional cost of external flow controls.
Humphrey Products
www.humphrey-products.com
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