The key factors in each application - temperature, pressure and process media - determine the choice of material for the internal sealant in all feedthroughs.
Pressure ratings
The pressure and temperature ratings and typical leak rates quoted are given for guidance only. Pressure tests have been undertaken at 20ºC using elements appropriate to the feedthrough under test, i.e., Mineral insulated cable in probe feedthroughs, bare or insulated wire in wire feedthroughs, etc. Ratings vary with temperature and sealant used. With an increase in temperature, a reduction in the maximum pressure rating can be expected. Contact Spectite for further details. The BSPT and NPT mounting thread pressure rating is the same or is higher than the feedthrough pressure rating.

Spectite feedthroughs have been designed to provide an efficient seal on the elements and restrain them from moving under pressure and vacuum. It is good installation practice to provide additional, mechanical restraint to the elements when differential pressure exceeds 75% of the feedthrough pressure rating at 20ºC. (Not applicable to series EF feedthroughs with integral electrodes). Consult Spectite for further guidance on pressure ratings.

Feedthroughs with Graftite, Neoprene, PTFE and Viton sealants are suitable for vacuum applications to 5 x 10-6 torr (6.67 x 10-4 Pa or 6.67 x 10-6 mbar). Lava sealants are not suitable for vacuum applications.

Leak rates
A typical leak rate for Spectite feedthrough assemblies with Graftite, Neoprene, PTFE and Viton sealants is better than or equal to 1 x 10-6 scc/sec. under 1 Atm. He @ 20ºC. (1 Atm. = 9.87 x 104 Pa or 987.2 mbar) .

Ordering information
Feedthrough and sealed tube assemblies are specified for ordering by a simple composite description that includes the type of feedthrough, the size of the feedthrough body (defined by the size of the process connection), the size of the element(s) to pass through the feedthrough, the number of elements (not applicable to series PF & PSF for single elements) and the sealant material.

An example of a typical order code for a feedthrough for multiple sensors (8 x 1.5mm dia. probes):

MF - 1/2” BSPT - 1.5mm - 8 - T - Cap NPT

If a feedthrough is required with a cap with a threaded conduit extension, the word Cap and the threadform required is added to the end of the order code, as shown in shadow in the example above.

Order code arrangements for feedthroughs for multiple wires and with integral electrodes include additional parameters. Further details are given in the order code information for each series.

For assistance with specifying and ordering Spectite feedthrough assemblies, particularly where there are high temperatures, high pressures or difficult application environments, contact Spectite Ltd.

Replacement parts and thread lubricant
Sealants and other internal components for Spectite feedthrough assemblies are available as replacement parts. To specify the component needed, prefix the order code of the feedthrough assembly for which the part is required by: RS for a replacement sealant; RP for a set of internal components, (i) for series MF feedthroughs comprising follower, sealant and seat, or (ii) for series WF feedthroughs comprising two internal insulators and sealant; RI for a pair of insulators for series EF feedthroughs; RE for a replacement electrode (with nuts and washers) for series EF.

A lubricant is applied to feedthrough bodies, followers and caps during assembly in our factory. It helps to prevent these component parts from binding and minimises friction between mating surfaces. Each time a feedthrough assembly is opened so that elements or sealants can be replaced or elements adjusted, re-application of lubricant is recommended. Speclube Lubricant is available from Spectite in handy 10ml bottles with applicator brushes. Order as Speclube Thread Lubricant.

Process connections
Feedthrough bodies can be specified with a choice of threaded process connections. Feedthroughs with the common tapered threadforms, BSPT (Conical gas thread or ‘R’ thread) to BS21, DIN 2999 ISO 7/1 & JIS B0203; and NPT (National pipe tapered thread) to ANSI/ASME B1.20.1 are generally stocked items.

Feedthroughs with parallel threaded process connections, BSPP (parallel gas thread or ‘G’ thread) to BS2779, DIN ISO 228/1 & JIS B0202; and ISO metric to DIN13, may also be specified. Feedthroughs with parallel mounting threads need an ‘O’ ring or a gasket seal (not supplied) to prevent leakage at the process connection.

Feedthroughs without process connection threads may be specified for welded mounting and with a fitted flange from a range of styles including ISO-KF and -CF types for the vacuum industry and general applications as well as Triclover® and triclamp types for the food and pharmaceutical industries.

Custom engineered assemblies can be designed and made to meet customers’ specific application requirements.

Plain, hexagonal caps are available for all sizes of feedthrough. Additionally, caps with a threaded extension for a conduit connection are also available. Specifiers may choose NPT, BSPP (parallel gas thread) or BSPT (conical gas thread). These caps can be specified for feedthroughs with 1/4”, 1/2” & 3/4” process connections. Cap threads are the same size as the corresponding feedthrough body process connection.

Pressure Equipment Directive (PED)
Spectite sealed feedthroughs have been classified as ‘Piping’, satisfying the requirements of the category of Sound Engineering Practice (SEP), according to the European Pressure Equipment Directive (PED) 97/23/EC. The PED does not require the ‘CE’ symbol to be identified on Pressure Equipment that is categorised as SEP. Caps are marked SPECTITE on one of the hex. faces.

Feedthrough component materials
Spectite feedthrough bodies, followers, seats and series EF SS electrodes are manufactured in an Austenitic stainless steel UNS S31603, commonly designated 316L. Equivalent grades are: (UK) BS 316 S11; (Germany) W.-Nr. 1.4404, DIN CrNiMo 17.13.2; (France) AFNOR Z2 CND 17.12; (Italy) UNI X2 CrNiMo 17.12; (Sweden) SS2353; (USA) AISI 316L; (Japan) JIS SUS 316L. The typical chemical composition for this steel is 0.03%C, 16.0-18.0%Cr, 10-14%Ni, 2.0-3.0%Mo, 0.10%N. Caps are manufactured in stainless steel UNS S30300 (303).

When 316L is unsuitable for an application, the ‘wetted’ metal parts of feedthroughs, that come into contact with a process, can be manufactured in other stainless grades or other materials such as Hastelloy® and Inconel® grades, Monel® R-405 or mild (carbon) steel. There may be minimum manufacturing requirements for feedthroughs in ‘exotic’ materials.

Insulators in series WF feedthroughs with 1/8” process connections and in series EF feedthroughs are manufactured in high-purity recrystallised Alumina (Aluminium Oxide Al2O3).

External, single-bore insulators in series WF feedthroughs are manufactured in aluminous porcelain. Internal insulators are manufactured in a high-performance, engineering plastic for use at temperatures up to +230°C or machineable glass ceramic for use up to +870°C.

Electrical conductors for Series EF feedthroughs are made in grade C101, fire refined, tough pitch, high-conductivity copper or 316L stainless steel (as above). Nuts and washers on copper conductors are brass, stainless steel conductors have stainless steel nuts and washers.

The lubricant used on feedthrough components is Chlorotrifluoroethylene Polymer (PCTFE). A copy of the Safety Data Sheet is available on request. Spectite feedthroughs should not be degreased before installation.

Kapton® is a registered trademark of E.I. du Pont de Nemours and Company
Viton® is a registered trademark of DuPont Performance Elastomers
Hastelloy®is a registered trademark of Haynes International, Inc.
Inconel® and Monel® are registered trademarks of the Special Metals Corporation group of companies
Triclover® is a registered trademark of Alfa-Laval AB

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