We need to seal a coaxial instrument cable in a feedthrough for an autoclave study. Can you do this?

We can seal against the outer jacket of any instrument cables except wide, flat cables in our custom fittings. The reason that we state the seal is on the outer jacket is that coaxial and multi wire cables can leak inside the wire bundle and through the multi wire shielding strands. Some end connectors between the wire and the sensor plug are hermetic and will seal the wire end. If these are not hermetic, we can open the wire bundle at either the connector end or the point where the wire goes through the feedthrough and inject sealing polymers to close off these leak paths. This usually work for all but the highest vacuum applications where glass frit or potted seals must be employed.

December 18, 2009 at 3:26 pm | Uncategorized | No comment

Can you seal on spiral cross section 2, 3 and 4 wire sensor cables?

Yes, Skyl-Tech, Inc. is the only company that can do this because of our low force soft seal technology. We mold the required spiral into each hole in the sealant and also include 4 integral “O” rings that conform to the 2, 3, or 4 wire cross section of the wire. Our soft seal prevents the crossing wires in the spiral from cutting into each other when the fitting is tightened to affect the seal. “Sandwich” seals used by all other companies can not seal on these wires because of the high compression forces required that will cut the insulation on the wires and cause shorts.

December 16, 2009 at 10:40 am | Uncategorized | No comment

We need a feedthrough for three very different size probe wires in the same feedthrough. Can you do this?

Yes. While this is not a standard application for our products, we can design and fabricate a custom feedthrough to accomplish this requirement. Also, because of our large number of feedthrough options, we may be able to supply individual feedthroughs for each wire size at a lower cost than a custom designed single unit. Because of the compact size of our feedthrough designs, the solution will be smaller in size than you might have thought possible. The fittings can be placed in a manifold if only one vessel penetration is available.

December 8, 2009 at 8:31 am | Uncategorized | No comment

Is your silicone rubber compound FDA approved? Certified Class VI?

Our feedthrough sealants are fabricated from a platinum cured silicone resin system that is in compliance with 21 CFR 177.2600. It is approved for food contact in manufacturing equipment.

The silicone rubber is not Class VI certified because it does not need to be. We had a firm and urgent request from a customer for Class VI certification for use in an autoclave. We convinced the customer that if this was necessary, then every gasket seal, instrument sensor seal, door seal, instrument sensor wire, and every contact surface in the autoclave would have to be Class VI. All possible, but so expensive that no one would be able to afford it. The requirement quickly went away.

November 20, 2009 at 4:37 pm | Uncategorized | No comment

Do you supply numbers for Kapton insulated thermocouples?

We can supply silicone rubber impregnated fiber glass numbered tubes for thermocouples that are to be used up to 250 ºC. Above this temperature, you can make numbers inexpensively by getting 0.010” to 0.020″  thick soft aluminum shim stock and cutting 0.5” by 1.5” strips and punching 1/8” holes in each end and scribing the numbers with a ball point pen. The thermocouples fit very nicely through the holes and do not require the thermocouple wire to be deformed to string the numbers. Some suppliers will sell you 1” diameter, 0.03” to 0.04” thick disks with stamped numbers with the same two holes that require that the thermocouple be seriously deformed to install. This deformation has the potential to cold work the wire affecting calibration and also damaging the Kapton insulation. The soft aluminum extends the life of your thermocouples and cost far less.

November 17, 2009 at 11:17 am | Uncategorized | No comment

The copper wire on our Kapton insulated thermocouples used in oven validation is being pushed out of the end of the thermocouple containing the junction. Is this a defect?

No, this is caused by differential expansion of the copper wire relative to the expansion of the Constantan wire. Because of the high temperatures found in ovens, the degree of differential expansion eventually forces the copper wire out the point of least resistance in the wire which is the exposed junction end. This can be stopped by installing a metal tip over the end of the junction and wire insulation and potting it in place. This produces enough resistance to stop the protrusion of the copper wire. It also slows the oxidation of the copper wire which eventually destroys the thermocouple.

October 20, 2009 at 2:27 pm | Uncategorized | No comment

Our Kapton insulated thermocouples used in oven validation are fraying, the insulation is unwinding, and the copper wire is turning black. Are they defective?

No, this is a normal occurrence in Kapton insulated thermocouple wire used in high temperature depyrogenation applications. The fraying and unwinding of the insulation is caused by degradation of the fluorocarbon binder on the Kapton film wound on the wire. The higher the oven temperature, the more quickly this occurs. The black color on the copper wire is oxidation also caused by the high temperature found in the oven. And here also, the higher the oven temperature, the more quickly this occurs and progresses more deeply into the copper. This deep oxidation can affect wire uniformity and accuracy and will eventually cause loss of conductivity in the copper wire and failure of the thermocouple. Thermocouples should be replaced once unwinding begins as wire failure is not far behind.

September 23, 2009 at 4:29 pm | Uncategorized | No comment

Customers have observed that the copper wire in the thermocouples turns black. What causes this and is it harmful to the thermocouple?

This is a normal occurrence when copper is exposed to high temperatures in the presence of oxygen and/or water vapor/steam. This can occur in both autoclaves and ovens. The oxidation is much faster in ovens. There is still some debate as to the harm caused by light oxidation. But when the oxidation turns black and then to dull porous or fractured black with the generation of particulates, the agreement is more universal that the uniformity along the wire and the conformity will be detrimentally affected. At this point, it is best to replace the thermocouples rather than risk inaccurate data.

September 9, 2009 at 10:25 am | Uncategorized | No comment

Our lyophilizer will not pass the leak test with the thermocouples installed. Can your feedthrough solve this problem?

Yes and maybe no! Yes, if you use our feedthrough and thermocouples. Maybe no, if you use your existing thermocouples. A thorough analysis and understanding of the situation is required.

A leak rate test on a lyophilizer is a particularly difficult test even without the presence of thermocouples and a feedthrough. Our validation quality thermocouples will hold leak free for a leak test when new. Our feedthrough will leak test down to 10 microns of mercury. The combination in a properly made assembly will hold down to 10 microns of mercury. If we make and vacuum certify the assembly, it will pass vacuum leak test if your lyophilizer will pass the test without the assembly installed. No other company will even try to match this guarantee and still supply validation quality thermocouples. Why is this so?

Even new properly fabricated thermocouples can leak under high vacuum levels found in lyophilizers. During the process of extruding the outer jacket over the two conductors, the molten FEP or PFA can have non uniform melt properties that result in thin areas, fisheyes, and microscopic holes in the jacket. These defects leak under high vacuum. The only way to find them is to vacuum test each thermocouple. The other source of leaks is the feedthrough. Skyl-Tech, Inc is the only company that makes a feedthrough with a resilient sealant with oval holes containing a labyrinth “O” ring system in each hole. This gives a positive seal around the oval cross section of the thermocouple. All other feedthrough manufacturers use a “sandwich” seal of two flat sheets of rubber squeezed over the thermocouples placed between them. It is physically impossible to affect an acceptable vacuum tight seal in this configuration. It is also very difficult to get a good seal between the two rubber disks and the sensor wires without tightening the assembly until the jacket and conductor insulation on the thermocouple deforms and fractures leading to serious leaks in the thermocouple.

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 customers and fabricators will use low conformity grade solid conductor wire in an attempt to stop these leaks and accept the lower accuracy readings as the only solution.

Another consideration for lyophilizer and Ethylene Oxide applications is proper training for operational personnel and validation technicians. Any rough handling of the thermocouples can cause abrasions or cuts in the insulation, both visible and microscopic, which will result in leaks. Training must include a thorough understanding of the delicate nature of the thermocouples and the problems caused by the leaks.

September 9, 2009 at 10:23 am | Uncategorized | No comment

What is the temperature limit for your feedthroughs? Can they be used on ovens?

Our silicone rubber sealants are usable from -40ºC to 200ºC for continuous use and 250ºC for intermittent use. Please remember that in oven applications, the wall protrusion that holds the feedthrough does not see the high oven temperature, but rather a temperature much closer to ambient.

August 28, 2009 at 9:07 am | Uncategorized | No comment

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