Frequently Asked Questions


 • Why are Skyl-Tech PV Seal FEEDTHRUs superior to sandwich flanges and potted seals?

 • What is wrong with attaching my sensor wires to the short lengths of copper lead
   wires found in commercial potted seals?

 • What makes Skyl-Tech FEEDTHRUs unique?

 • What is Skyl-Tech's PV-SEAL technology?

 • What is Skyl-Tech's delivery policy?

 • Why can't I buy Skyl-Tech sealants without buying a FEEDTHRU?

 • But what if I need to replace a sealant?

 • Can Skyl-Tech provide custom solutions or design validation studies?

 • What if I need fewer holes than are available in standard sized FEEDTHRUs?

 • Where can I find "use and assembly" directions for your FEEDTHRUs?

 • The feedthru is leaking. What do I do?

 • Why should I use stranded thermocouple wire instead of solid wire?









Why are Skyl-Tech PV Seal FEEDTHRUs superior to sandwich flanges and potted seals?

Sandwich flanges and potted seals are inherently flawed. Sandwich flanges are difficult to assemble because you must hold the 24 loose sensor wires separated from one another while holding and aligning the two flanges and two rubber sealing disks while inserting and tightening the four sets of bolts, nuts, washers, and lock washers with two wrenches. Accomplishing this feat is extremely difficult, even with multiple people and must be repeated every time you have to change a broken sensor wire.

It is also very difficult to get a good seal between the two rubber disks and the sensor wires without tightening the assembly to the point of crushing and damaging the sensor wires. The sandwich flange cannot be used in high vacuum applications such as lyophilizers and definitely should not be used on Ethylene Oxide sterilizers where even leaks resulting in part-per-million concentrations outside the chamber cannot be tolerated.

Some recent attempts to modernize the sandwich flange have made it slightly easier to assemble but have not cured the leakage problems. It is still very difficult to get a good seal between the two flat rubber disks and the sensor wires without tightening the assembly to the point of crushing and damaging the sensor wires.

Creating a potted seal is easier than assembling a sandwich flange, but RTV rubber or epoxy take a long time to repair and the resulting seals are impossible to repair. Broken sensor wires cannot be removed without the risk of damaging other sensor wires. A broken sensor could force you to discard an assembly worth thousands of dollars.

Potted seals also present a safety concern. The RTV rubber and epoxy soften at sterilization temperatures and could be forced out of the metal retaining cylinder with catastrophic results due to the pressure inside the sterilizer. Rigid epoxies present other problems. With multiple uses the heating and cooling of the assembly can cause the bonds between the epoxy and wire insulation and the epoxy and the metal cylinder to rupture and form leaks that are impossible to permanently repair. The first heat/cool cycle will usually reopen the leaks.

The Skyl-Tech PV-Seal FEEDTHRU solves all of these problems.
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What is wrong with attaching my sensor wires to the short lengths of copper lead wires found in commercial potted seals?

Copper lead wires impair the accuracy of the thermocouple system. All connections must be completely insulated to prevent moderate to high resistance shorts in the steam environment inside the sterilizer. Further, the conformity of the copper lead wires will not perfectly match the conformity of your thermocouples, resulting in unacceptable calibration and measurement errors.
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What makes Skyl-Tech FEEDTHRUs unique?

Our FEEDTHRUs provide an easier way to introduce sensor wires into pressure and vacuum vessels such as sterilizers, lyophilizers, vacuum ovens and barometric chambers. Skyl-Tech FEEDTHRUs eliminate the problems associated with other sealing glands, cumbersome sandwiched double flanges and in-house potted seals. Our FEEDTHRUs do not develop leaks with handling and usage. Broken sensors are easy to remove and replace: simply loosen the pressure cap, pull out the old sensor, insert a new sensor and hand-tighten the pressure. The seal is restored.
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What is Skyl-Tech's PV-SEAL technology?

Skyl-Tech sealants are specially designed to seal effectively and effortlessly. Unlike other sealing solutions, Skyl-Tech sealants are available with oval holes for oval cross-section duplex thermocouple wire. And, since our sealants are fabricated from a durable but resilient material, they only need to be hand-tightened to produce a perfect seal. No wrenches. No leaks. Easy probe replacement.
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What is Skyl-Tech's delivery policy?

Delivery times range from 1 week for in-stock items to 4-6 weeks for non-inventory items. Please specify UPS Next Day Air for speedier shipment once your order has been processed. Depending on the complexity of the project, custom solutions may be subject to a lengthier delivery time.
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Why can't I buy Skyl-Tech sealants without buying a FEEDTHRU?

While PV-SEAL technology is at the heart of all Skyl-Tech FEEDTHRUs, it is only one part of a complete validation system. We cannot guarantee how a sealant would function if used outside a Skyl-Tech FEEDTHRU.
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But what if I need to replace a sealant?

When used properly, Skyl-Tech sealants will provide you with many years of service. If a sealant fails, it is almost always as a result of mishandling. Skyl-Tech FEEDTHRUs should only be tightened by hand. We cannot emphasize this enough: technicians should NEVER use a wrench to tighten a Skyl-Tech FEEDTHRU. Such force is unnecessary and will often destroy the sealant. Please see our "proper use" white paper for more information. In the event that a sealant does fail, Skyl-Tech can replace it and rebuild the damaged FEEDTHRU.
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Can Skyl-Tech provide custom solutions or design validation studies?

Yes. Over 25 years of industry experience go into every validation product we make. We have designed custom solutions (specialty FEEDTHRUs, in particular) that are used throughout the world. We are also available for on-site consultations and the design of thermal validation studies. Please contact us for more information.
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What if I need fewer holes than are available in standard sized FEEDTHRUs?

Skyl-Tech FEEDTHRUs are available in several sizes, ranging from 1 to 24 holes. If we do not have a standard size with the exact number of holes you need, then you should order the next larger size we do carry. (For example, if you need 4 holes, order a 5 hole FEEDTHRU.) For a nominal fee, Skyl-Tech will provide you with specially designed, Stainless Steel "hole plugs," which will allow you to block the FEEDTHRU holes you are not using while maintaining a perfect seal. For high-volume requests, we can also design FEEDTHRUs with special hole configurations. See our consulting page for more information.
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Where can I find "use and assembly" directions for your FEEDTHRUs?

Directions are sent with each FEEDTHRU and custom assembly. They can be found here. The directions for making an entire assembly are also available.
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My FEEDTHRU is leaking. What do I do?

1| Before you place the thermocouples into the sterilizer, make sure that the chamber is leak free. If it is not, then you might have wrongfully attributed the leak to the thermocouples or the FEEDTHRU.

2| Check that all of the FEEDTHRU holes are either filled with sensor wires or hole plugs. Empty holes will leak.

3| The sensor tips must be encased in an impervious cover such as fused FEP or PFE. Potted metal tips sometimes begin to leak after hard use. Make sure that the junction is fused in FEP or PFE before the metal tip is placed over the junction.

4| If the insulation over the wire (either the outer covering or the inner conductor insulation) is broken, the air or steam will leak through the channels between the over cover and the inner insulation and/or through the channels between the strands of the wire.

5| Check how the assembly was put together. Dust on wire must be wiped off using a damp, lint free cloth as the wire is drawn through the hole. If not, the dust will pack up in the hole entrance and eventually pull into and through the hole forming a leak path.

6| Skyl-Tech FEEDTHRUs only require hand tightening. The final possibility is that the FEEDTHRU was over-tightened using a wrench. If this has occurred, the sealant has been ruined and must be replaced.
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Why should I use stranded thermocouple wire instead of solid wire?

Thermocouples are not perfect and can produce many kinds of errors. One of the most significant errors is caused by non-uniformity of the wires. This non-uniformity exhibits itself in two forms: non-uniformity of the alloy in the wires along the length of the wire and non-uniformity in the crystal structure of the wire due to incomplete annealing or handling and bending of the wire.

Stranded wire addresses the second type of non-uniformity. Solid conductor thermocouple wire is stiff and difficult to handle. Getting it to conform to the desired paths inside a sterilizer requires that the wires be bent and sometimes severely kinked over a small radius to get the sensor tip into the desired position. After the run, the wires are straightened out which requires further bending. This bending and unbending causes the metal of the wire to work harden and crystallize. These crystals are of different sizes depending upon the amount of bending they experience. If the wire is an alloy such as Constantan, the crystals can actually cause the alloy to separate into different alloys and possibly crystals of the individual metals in the alloy. This results in non-uniformity of the wire, which causes errors. Stranded wire is limp and easily drapes and conforms around the load inside the sterilizer. It can be bent over a 0.5 inch radius and straightened without work hardening. As a result, it is less prone to non-uniformity errors due to handling and will have a much longer useful life.
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Sensors with number rings installed will not go through the FEEDTHRU holes. How do I solve this problem?

Ask your supplier to supply sensors with the numbers rings not yet installed. You can install them after the sensors are inserted into the FEEDTHRU. Your other option is to order your sensors directly from Skyl-Tech, Inc. We have developed a number ring that is only 0.001 inches thick that does not interfere with inserting the sensor into the holes. It is also more durable than conventional rings and does not come loose in the heat of a steam sterilizer. The rings also have a slick surface that does not attract dirt or discolor during long periods of use.
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