TechArchive

Original article date: March 2000

A new free brochure from Conax Buffalo shows what’s available to assist when probes must pass through an environmental barrier without loss of integrity.

The plastic deformation of a sealant material within a fixed housing is the fundamental concept of Conax sealing technology, which is designed for situations where probes and other elements must pass through a pressure environmental barrier without loss of integrity at the point of penetration.

There are 10 basic forms of gland assembly which include models accepting sheathed single or multi sensors and probes, including thermocouples and RTDs and units for sealing directly onto insulated leads, as well as glands sealing onto ceramic insulators, as required in high voltage applications

When an element is inserted in a gland and the cap is torqued to the recommended setting, the torque on the cap translates an axial force on the follower, which compresses or crushes the sealant that is contained within the body, thus creating a seal on the element. Tension in the body acts as a spring to maintain compression – friction between the sealant and the element restrains the element from moving under pressure or vacuum.

Glands for single sensors and probes (PG glands): These are excellent for applications such as single, sheathed thermocouples, resistance thermometers, thermistor probes and other types of sensors. They are easily assembled by simply inserting the sensor element and torqueing the cap.

Multiple sensor and probe glands for elements (MHC glands): These enable multiple tubes, probes, thermocouples or other sensors to pass through a single gland. Each probe is electrically isolated and its immersion length is adjustable.

Multiple sensor and probe glands for non standard sizes and configurations (MHM glands): These can often be used where other types of probe glands are not suitable. They can be customised to accommodate non-standard sizes and a mixture of element sizes, for special hole patterns and for a higher density of elements than can be accommodated by other types of sealing assemblies.

Single and multiple sensor glands with split internal components (PGS, SPG and DSPG glands): These are used when the elements to be sealed can pass through the gland body but not through the internal components. For example, their process ends may be of a larger diameter than at the sealing point, there may be connectors to pass through the gland, elements may be long and difficult to handle or there are other installation constraints.

PGS glands are for a single element and SPG glands are for multiple elements, as their internal components have a single spit. DSPG glands are for multiple elements and have internal components with a double split.

Single electrode power glands (EG and EGT glands): These single conductor sealing glands are used for high voltage and/or high current feedthroughs to vacuum chambers, autoclaves, transformers, motors, reactor vessels and environmental chambers. EG glands are available with a choice of sealants and have ceramic insulators. EGT glands employ a single Teflon, combined insulator/sealant component to surround the electrode.

Insulated wire sealing (PL glands): These power lead glands have Kapton (polyimide) insulated copper wire in a number of wire sizes. They are used to feedthrough power leads to autoclaves and sterilisers, transformers, motors and heaters. Wires are individually marked at both ends and are easily installed or replaced.

Bare wire sealing and insulated wire sealing with 24 AWG Teflon insulated wire (TG glands): TG glands seal multiple bare wires in a range of wire sizes. They can be used for solid bare wire transducers such as thermocouples, strain gauges, thermistors, resistance element leads and low voltage, low current supplies and signal wires to instrumentation. The same glands can also be specified as complete assemblies, ready for installation.

Bearing sensor wire seals (type BSWS): Bearing sensor wire sealing assemblies efficiently seal directly onto the insulated leads of an embedded temperature sensor in an oil-filled bearing housing to prevent oil migrating along the leads. They are suitable for motors, turbines and pumps.

High density, mechanically sealed, wire feedthroughs using single or multiple probe glands (type HD): These feedthrough assemblies comprise a high density, wire feedthrough mounted in a sealing gland. A Teflon-lined, stainless steel tube is swaged over solid, Teflon-coated, copper and/or thermocouple material wires to make the high density continuous wire feedthrough for thermocouples, RTDs and low voltage instrumentation.

Fibre optic seal assemblies for sealing on optical fibre cables (type FSA): FSA optical fibre sealing assemblies enable a range of sizes of fibre optic cable to pass through environmental boundaries. Fibres are housed in individual, protective stainless steel tube seals. These may be supplied as a complete integral assembly, with connectors if required, in one of the standard pressure and vacuum sealing glands.

• Conax Buffalo

March 2000