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Latest Press Releases
- Seal Material
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Peter Paul EPDM seals, non-absorbent, high pressure uses
New Britain – Peter Paul now produces Ethylene Propylene Diene Monomer (EPDM) valve seals for high pressure gas applications in place of more absorbent standard rubber seals.
EPDM seals can be applied in medical environments, aerospace projects, and similar uses where gas absorption can interfere with normal equipment operation. EPDM seals are available for most Peter Paul valves lines, particularly in the 20, 30, and 50 Series.
Gas con be adsorbed by the material in standard seals and in instances of low pressure, which causes it to balloon, sometimes even fracture. The unique, high durometer EPDM seals, developed by Peter Paul and used in place of conventional seal material, however, have great resistance and are specified to minimize in-service absorption.
Peter Paul Electronics, established in 1947, provides through worldwide distribution a broad range of standard and miniature solenoid valves, explosion proof, high-flow and high pressure models - most UL and CSA listed; complementary manifolds and stacking bodies in stainless, brass or aluminum; solenoid valve operators for OEM use; and a vast array of body, housing and coil options for standard and special applications.
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| Typical Peter Paul Electronics 3-way and 2-way solenoid valves for use in medical applications such as hospital beds, breathing apparatus, and quiet, no-click operation (shown on cutaway). |
3-Way and 2-Way Solenoid Valves For Quiet (No-Click) Operation
Peter Paul Electronics Co., Inc. has recently developed solenoid valves for use in medical applications such as hospital beds, breathing apparatus, and inflatable mattresses for burn patients in which a bumper is installed for quiet operation.
In normal industrial applications, the click of a solenoid valve is not an issue, but in the quiet of a hospital environment it can be nerve wracking to hear constant clicking as the valve is actuated. Several new plunger and bumper designs used in the 3-way function have a top seal but eliminate the metal-to-metal contact.
One way to "eliminate the click" is to put in a rigid top seal that's non-compensating and doesn't move. The top seal contacts the end stop, but no metal contact is made. It requires a unique plunger and uses a special end stop to accommodate it. Many times the pressure ratings are reduced just a bit due to the increased air gap in the valve, affecting magnetic performance. Usually these applications are low-pressure air or vacuum, therefore the reduced rating of the valve is generally not an issue.
Rectified coils are also often specified in medical equipment, either full bridge or half bridge, to eliminate the potential for noise. A valve, which might potentially cause a hum or buzz can be very annoying to a patient, so a full wave rectified unit for AC service is often preferred. A DC unit, not requiring a rectifier, is sometimes used in specific applications.
Also common is a bumper in a 2-way valve, usually just a flat disk with no sealing action. Bumpers may be urethane or filled Teflon or special low cold-flow Teflon, which doesn't become deformed like virgin Teflon. Occasionally, a bumper is included in a valve for a non-medical application where long life is critical. With a bit more cost, a Teflon-coated plunger combined with a bumper will provide very long, quiet valve life under many operating conditions.
The 50-year-old Peter Paul Electronics Co., through a worldwide distributor network, provides a broad range of standard and miniature solenoid valves; Explosion-Proof, High-Flow, and High Pressure models; complimentary manifolds and stacking valves in stainless, brass, or aluminum; solenoid valve operators for OEM use; and a vast array of body, housing, and coil options for standard and special applications. Most Peter Paul solenoid valves are UL recognized and CSA listed.
For further information, write:
Valves For Quiet Applications
Peter Paul Electronics Co., Inc.
480 John Downey Drive
P.O. Box 1180
New Britain, CT 06050-1180
Phone: 860 229-4884
Fax: 860 223-1734
E-mail: info@peterpaul.com
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Making Kalrez® Seals Affordable for Volume Valve Applications
Kalrez® Perfluoroelastomer seals, a product of DuPont Dow Elastomers, are impervious to more than 1,600 chemicals and solvents, inert to most chemically induced swelling, useful in temperatures from –20°F to 600°F, and last much longer then other elastomer seals. Unfortunately, at about $2,000 per pound, Kalrez is also a very expensive design material, even in medical and chemical resistant applications for which no other seal material is nearly as durable.
We have been using Kalrez for solenoid valve plunger seals in applications where nothing else would do. These long lead-time, molded Kalrez seals often more than doubled the price of comparable valves incorporating other elastomer seals. And Kalrez is s tough material to form: It sticks in the mold, and is difficult to maintain dimensional accuracy in complex shapes…not to mention cost of Kalrez rejects and molding waste (which are not easily disposable).
But…design engineering to the rescue. Our Senior Design Engineer William Milish has helped develop a procedure for laser cutting Kalrez seals from 3” square sheet stock. “It took a little practice,” says Bill, “but we’ve now been able to cut the amount of Kalrez used per seal by about half, reducing the cost per seal, even in relatively small quantities, by about 40-60%.” Currently limited to 3/32” and smaller orifice sizes, the valve plunger assembly has been slightly modified to use a stainless steel cup to attach the Kalrez seal to the plunger. The use of the cup actually governs the plunger length better, and two tiny notches on the seal circumference allow the seal to vent gases from within the plunger. The result: A bubble-tight seal for the most difficult chemical applications, without the use of Teflon. “It’s an elegant solution to an expensive problem,” according to Bill Milish.
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| We can provide a wide variety of cryogenic valves and manifolds, if required, for low temperature operation involving refrigerants or liquid nitrogen. |
Cryogenic Valves For Low Temperature Applications
Our solenoid valves, those precision electro-mechanical “switches” required to perform millions of unattended cycles in applications ranging from coffee vending machines to metal cutting machine tools, are also widely employed at low temperatures to about –40°C involving gaseous and liquid refrigerants and liquid nitrogen.
For these uses, the full range of our 2 and 3 Way cryogenic valves can be specified with Teflon® or KEL-F seals required for processing semi-corrosives. Typically all cryogenic valve parts must be oxygen cleaned to remove oils and other surface contaminants. In many such applications, a compressed liquid is metered by the valve. Many of these cryogenic valves will be UL recognized and CSA listed.
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Swell Resistent Printers Gum
Another thing we've done is a special elastomer for use with water-based printing links. We think of ink as being almost benign, but sometimes it can be rather aggressive to certain materials, and swelling of the rubber typically causes a big problem in the dispensing valves for ink.
Peter Paul has worked with our existing rubber supplier on a specific material for ink that was originally developed for the rubber stamp industry and the automatic mailing label industry. If a rubber stamp were to swell up, lettering and logo would become distorted...so we've come up with a special material: We've developed an elastomer with customized nitrile rubber and very unique for the printing industry. We supply this in conventional plungers, disk compensated plungers and to media isolation diaphragms for ink dispensing and retrieval systems, some in high-speed ink jet printers.
Commercial ink jet printers do things like posters and large billboards. They fire all the ink jets at one time and deflect them so they have to pratically vacuum away the ink that isn't used. Some of these inks are magnetic so the media isolation valve is really the only way to control the flow of these inks. We found that while a number of diaphragm materials are useable, we picked a specific material for the water-based ink printer. It seems to mold well in existing tooling and is relatively ecomomical in cost, seeming to perform fairly well for the water-based inks. This product is currently available in Series 50 and 20 size in the diaphragm media isloation avlves.
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| Only a small amount of swell can shut off valve flow. For that reason, FKM seals are now installed for gasoline and propane solenoid valve applications. Note the seal swelling on the right...more than enough to impede plunger travel. |
Peter Paul Develops New FKM Seals for Gasoline and Propane Valve Applications
Today's alternative powered vehicles and reformulated gasoline’s are causing increased occurrences of solenoid valve seal swelling and cracking in service. This has created the need to reformulate existing FKM compounds to maximize their properties in reformulated gasoline’s, which have significant amounts of MTBE and alcohol.
Additives also have been causing problems with seal integrity, frequently in propane-powered vehicle applications. These fuel applications involve seal swelling with existing standard fluorocarbon elastomers, generically called FKM, but available with trade names such as Viton and Fluorel. Peter Paul discovered that, by maximizing the fluorine content of their FKM, the swelling was reduced. Further enhancement of the physical properties was made by removing the traditional colorant and adding carbon black. Therefore, the normal color of this new FKM is black.
Peter Paul sees more and more FKM problems in vehicle applications involving solenoid valves, both gasoline powered and alternative fuels (e.g. propane). In the state of Connecticut, for instance, reformulated gasoline can be up to 15% MTBE, causing problems with traditional FKM systems. Swelling and rubber decomposition appear with time. Beyond vehicular applications, other related uses, particularly in the medical field, have shown to be more stable and long-lasting when the new FKM is applied.
The 50-year-old Peter Paul Electronics Co., through a worldw1de distributor network, provides a broad range of standard and miniature solenoid valves; Explosion-Proof, High-Flow, and High Pressure models; complimentary manifolds and stacking valves in stainless, brass, or aluminum; solenoid valve operators for OEM use; and a vast array of body, housing, and coil options for standard and special applications. Most Peter Paul solenoid valves are UL recognized and CSA listed.
For further information, write:
Reformulated FKM
Peter Paul Electronics Co., Inc.
480 John Downey Drive, P.O. Box 1180
New Britain, CT 06050-1180
Phone: 860-229-4884
Fax: 860-223-1734
E-mail: info@peterpaul.com
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| Solenoid valve plunger travel stroke is typically 0.020 to 0.050 in., depending on orifice size. Choosing the wrong seal material could literally shut off the valve flow. Notice the swelling in the seal at right. |
EPDM Seals
Special EPDM (Ethylene Propylene Diene Monomers) solenoid valve seals are used for applications where high-pressure gases tend to be absorbed in standard rubber seals.
When gas is absorbed into a rubber solenoid valve seal, it doesn’t normally cause any physical degrading of properties but will cause the rubber to display a phenomenon called explosive decompression. If the system were to be vented or pressure reduced, gas that is trapped inside the rubber tends to cause the seal to balloon and swell, sometimes actually fracturing. Users in the fire extinguisher field, for instance, find that rubber swelling over a period of time may actually cause the fire extinguisher valve to shut off.
Used in place of conventional seal materials, such as urethanes, EPDM is more suitable for specific, hard-to-fill applications such as high-pressure gases used in aerospace projects.
For further information, write:
Peter Paul Electronics Co., Inc.
480 John Downey Dr.
PO Box 1180
New Britain, CT 06050-1180
Phone: 860 229-4884
Fax: 860 223-1734
E-mail: info@peterpaul.com
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