Developing a concept originally aimed at sealing liquids Feodor Burgmann has introduced a version of the CSR aerodynamic clearance seal for gases and gases containing solids.

The CSR type aerodynamic clearance seal consists of a split carbon graphite restricting ring that is held together by a tension spring around its circumference. Pockets are worked into the inner surface of the ring to generate a radial lifting force under operating conditions. A concentric gap thus forms automatically as the seal lifts off the shaft. Measuring no more than a few um this gap is small enough to keep leakage to a minimum. Good static sealing at standstill is guaranteed because the seal and the shaft are then in contact.

Now manufacturer Feodor Burgmann has launched a further development of this seal with a bi-directional gal lubricated version for gaseous media. It is suitable for all gas conveying machines such as gas turbines compressors turbochargers and turbo pumps. It can also be used with gases containing solid particles of grain sizes up to 10um. Liquid mist or flooding at standstill is withstood without damage as are radial movements of the shaft in the 0.1mm range.

The main advantage of this seal over comparable sealing elements for gases is that it achieves lower leakage rates whilst requiring the same installation space. For example its leakage is up to 50 times less than that of a labyrinth seal. Because a higher pressure differential is possible with a constant leakage rate the seal represents a simple form of differential pressure control for buffer gas systems. It runs together with the shaft but without making contact with it thereby enabling a machine to be shut down under controlled conditions in the event of a malfunction.

The cartridge design makes it easy to install. High sliding velocities are a feature: up to 200m/s cooled – ie with applied differential pressure) and up to 100m/s uncooled (unpressurised).

The operation of the CSR seal is independent of temperature in that the leakage rate remains almost unchanged throughout the entire temperature range (up to 500degC). Good emergency running properties are provided by the carbon graphite.

• Feodor Burgmann
• Ellen Neubarth
• +49 8171 23 14 53
• www.burgmann.com

September 1999

The European Sealing Association says that with the advent of asbestos-free sealing materials engineers need guidance about the new approaches required. Consequently it has published a technical glossary relating to flange and gasket sealing terminology aimed at end users OEMs and contractors.

The publication contains descriptions of all the common terms used in sealing and includes layouts for typical flange and gasket systems of which there are many in common use described below. Units of common usage in flange gasket terminology are listed with conversion factors. Relevant standards are listed together with the details of the organisations which issue them. Common abbreviations complete the lineup.

Flat face flanges contain a full face gasket. This is a non-confined gasket with both flange contact surfaces flat. This type of flange is normally used where the flange material is relatively fragile.

In the raised face flange flange contact surfaces are raised although the gasket is non-confined. Normally the gasket covers up to the inside of the bolts. This type of flange allows assembly and removal of the gasket without having to separate the complete flange system thereby making maintenance work easier. It is used commonly in pipework systems.

The tongue and groove flange has a totally confined gasket. The groove depth is equal to or greater than the tongue height. Normally the gasket has the same width as the tongue. In this design it is necessary to separate the flanges completely to change the gasket. This flange system exerts high seating pressure on the gasket and is not usually recommended for non-metallic gasket types.

The spigot flange also known as the male and female flange contains a semi-confined gasket. This can appear in a wide variety of forms. The depth of the female flange is equal to or less than the height of the male in order to avoid the possibility of direct contact between the flanges when the gasket is compressed. The flange system must be separated in order to change the gasket.

The flat face and groove flange system has a totally confined gasket. The external face of one of the flanges is plain and the other has a groove where the gasket is assembled. They are used in applications where the distance between the flanges must be precise. When the gasket is seated the flanges are usually in contract with each other. Only resilient gaskets should be used in this system.

The ring joint flange is also called an API ring. Both flanges have channels to accept the gasket which is normally made of solid metal.

• European Sealing Association
• 01524 844222

March 1998

Coriolis flowmeters are adding flexibility to fluid weigh platforms

For many years, manufacturers of industrial liquids have used weigh-filling systems to monitor the quantity of product delivered into the final drum or container. A recent design from RCS Filling Machines monitors the weight of fluid dispensed using a Coriolis Mass flowmeter from Micro Motion, a division of Fisher-Rosemount: this meter replaces the normal cumbersome static weigh platform, allowing the whole machine to become a mobile manoeuvrable unit.

There are growing numbers of applications like this where the Coriolis meter is displacing old-established flow or weigh measurement techniques. They all involve close co-operation between the meter manufacturer and the special purpose machine builder.

The new RCS Filling Machine incorporates a number of features: lance retraction and wiping systems as the container fills; an automatic two-stage valve closure as the end point approaches, to improve fill accuracy and reduce batch overrun; and drip tray insertion under the nozzle after closure. The electronic logic system is intelligent, learning the effects of flow rates and delivery pressures, by monitoring the overfill at the end of each cycle, and reducing such overshoot on subsequent deliveries.

The whole system has achieved full Weights and Measures Approval, and one such system is in operation with Polartech in Manchester.

Polartech manufactures additives for metal working fluids, and supplies these globally to lubricant blenders and marketing companies. Consignments can be in 20 or 25 litre packs, 205 litre drums, or 1000 litre IBC containers.

The new portable filling system has been a joint development effort between RCS and Micro Motion engineers. “The major advantage we are able to offer our customers is that multiple drums can be filled on a pallet, or even on stacked pallets, eliminating the need for individual drum handling,” says Ross Gammon, the MD of RCS Filling Machines. “By avoiding the requirement for the conventional static weigh platform, pre-adjusted for level, the flowmeter based fill system can be made portable: the operator can simply move from pallet to pallet around the warehouse.”

By using the Coriolis meter sizes now available, the volume dispensed from these RCS machines can range from as low as 50g, up to in excess of 1000kg. Fisher-Rosemount sees this co-operation with specialist companies and systems integrators like RCS as important in providing the best service and support to industries requiring detailed application expertise. Recent similar distribution agreements have been made for Micro Motion flowmeters to be sold through Fluid Management Technology, of Oxford, where a recent project involved edible oil measurement in an ice-cream factory, and Industrial Flow Control (IFC) of Essex, who specialise in road and rail tanker loading systems.

• Micro Motion
• Fisher-Rosemount

July 2000

Best known for its manufacture of magnetically coupled plastic pumps Totton Pumps has now entered into an agreement with Fluid Metering a company based in New York to produce an accurate metering pump for the European market.

AF piston pumps operate with only one moving part. The patented design utilises a single dimensionally stable and chemically inert ceramic piston in a ceramic or carbon cylinder. The pumps are infinitely adjustable from zero to maximum flow at rest or during operation. They can replace peristaltic and diaphragm pumps where absolute precision dosing over long periods is important. They are particularly useful when used with expensive wash and treatment chemicals.

The design eliminates diaphragms check valves peristaltic tubing and packings virtually eliminating downtime due to pump failure and/or routine maintenance. The valve-less pumping function is achieved by synchronous rotation and reciprocation of the ceramic piston in the precision mated ceramic liner. One complete piston revolution is required for each suction/discharge cycle (as shown). The piston always bottoms for maximum fluid and bubble clearance. Virtually maintenance-free accuracy and reliability is assured over millions of strokes. The new AF range carries BEAB EN 60335-2-4 approval.

Materials to suit hygienic or chemical applications

• Totton Pumps
• Tel: 01703 666685

May 1999

The selection of the right pump for the job is primarily a matter of matching the required performance range against the capability of each product type, as shown in the accompanying charts.

With over one million pump units sold into more than 35 countries, ASF Thomas supplies a broad product range of air compressors and vacuum pumps that fall into a number of major product groups. The operating principle of each product group is described and illustrated. Any special features which may influence its suitability or unsuitability for a particular application are also mentioned.

A peristaltic pump is required where integrity of the pumped medium is paramount and no leakage can be tolerated. This is achieved by enclosing the medium in a continuous tube which is mounted in a cylindrical casing. Within the cylinder is an eccentrically-mounted shaft, carrying a set of freely rotating rollers fixed on a pair of plates and these rollers are in near-continuous contact with the tube.

As the pump shaft rotates, the eccentric shaft initially causes the pumped medium in the tube to be t rapped against the casing and between adjacent rollers. It is then moved around the cylindrical casing until it exits the pump as the rollers release it. Flow rates can be closely controlled and fiarly aggressive materials can be handled.

In a diaphragm pump, reciprocating motion in a connecting rod is produced by an eccentric bearing on the pump’s drive shaft. Attached to the con rod is a diaphragm which is flexed in a closed chamber, alternately compressing and expanding the contents of the chamber, with inlet and outlet flapper valves controlling the direction of flow.

Whilst similar in concept to a piston pump, there is no sliding seal between moving parts, so integrity of the medium being pumped is preserved, making this the preferred pump when contamination is to be avoided. The chamber is fully exhausted during compression and while the stroke is much shorter than a piston pump, similar vacuum levels are achieved.

On a rotary vane pump, the pumping action is produced by a set of flat vanes fitted on a rotor eccentrically mounted in a cylindrical casing, thus producing a set of unequal swept volumes between vanes. As the rotor rotates on the pump shaft, these swept volumes gradually increase to a maximum, then decreases, with each cycle.

Inlet and outlet ports are carefully positioned in the casing so that the pumped medium is drawn into the expanding swept volumes during the suction half of the cycle, then compressed in the contracting swept volumes during the discharge half. This action produces relatively pulse-free flows from a compact, vibration-free unit.

WOB-L piston pumps operate on the same principle as conventional piston pumps, but with one essential difference: there is no bearing between piston head and connecting rod. This eliminates the need for piston rings. Instead, a rugged, flexible cup is fitted to the piston head.

With no small end bearing, the balanced eccentric cam on the pump shaft causes the integral rod and piston to wobble in operation. Resistance by the pumped medium during the compression stroke expands the cup during the compression stroke, compensating for the wobble and providing a highly efficient seal for consistent performance.

• ASF Thomas
• Tel: 01420 544184
• Fax: 01420 544183
• Contact: Warren Bease, Managing Director

Finally the Government has confirmed the long-awaited expectation that it would introduce a ban on the import supply and use of all asbestos-containing products. The sealing industry expects a ban on asbestos to be in force by the end of 1998 or early in 1999. So what now?

Comprehensive ranges of alternative gasket materials have been under development for many years and Beldam Crossley now claims to have a range which will match virtually every application where compressed asbestos fibre (CAF) is now employed.

But selecting a gasket material represents only half the story when aiming for optimum performance in a flange. Correct installation procedures and maintenance are equally important. To fit them correctly use a sensible “opposite pattern” procedure for tightening bolts or studs. Each bolt should be secured finger tight and then tightened to 30% of final torque then 60% then to final level.

Clean and lubricate bolt/stud threads prior to assembly wherever possible as this can result in 100% more stress on the gasket using the same bolt torque due to lower thread friction.

Generally the thinner the gasket the better the performance. 1.5mm thick material will usually be the correct choice for Class 150 standard flanges up to 600mm diameter. Use 1 on Class 300 flanges up to 600mm diameter. 3mm should only b needed for larger flanges or old/damaged flanges. For normal cut gasket applications a flange surface finish of 3.2um to 12.5um Ra (125 to 500uin) is acceptable.

Select a bolt torque which will create a gasket stress somewhere between the minimum and maximum recommended. It is usually best to use a bolt torque which represents somewhere between 50 and 80% of the yield stress of the bolt material at the operating temperature. But the 50% minimum may be reduced to 25% for higher tensile bolt materials.

Jointing compounds are not needed to effect a seal and they can often impair gasket performance. Their use should be avoided. And anti-stick finishes can be provided in other ways.

Re-tighten after one cycle or up to 24 hours but not after a longer period. This is particularly important for fibrous gaskets because they may become brittle in service and crack on re-tightening.

More gasket problems are caused by under-tightening than by over-tightening. Unfortunately asbestos-based gaskets were very tolerant in this respect but the asbestos-free grades ar eless so. Only on smaller flanges (eg 25mm and below) will over-tightening be more likely than under-tightening.

Most gaskets are not designed for re-use. A gasket is a precision component often containing a polymer binder. It needs good storage conditions to ensure that it is not degraded before it is fitted. And never re-use a gasket – the small saving involved may well result in extra cost later if a leak occurs.

Beldam Crossley is offering a special deal with the following elements:

• A free stores survey to highlight and identify all asbestos-containing sealing products.
• Offer specific advice on asbestos-free gaskets for critical flange applications including ideal thickness bolt torque etc.
• A comprehensive report to be submitted for less critical applications giving general recommendations and advice regarding asbestos-free substitutes.
• Formal in-house product training covering the technical aspects of gaskets such as gasket selection correct installation fugitive emissions reduction and troubleshooting.
• Free sample gaskets for evaluation on plant.
• Free removal and dispersal of any surplus asbestos-containing sealing product.
• 30% discount from the first order for asbestos-free gaskets.

• Beldam Crossley
• P Childs
• 01204 494711

September 1998

Gas-lubricated mechanical seals are a modern service-proven alternative for sealing gaseous or liquid media in machine components with rotating shafts. JOSEF NOSOWICZ ANFDREAS SCHRUFER and ULRICH RID of Feodor Burgmann explain the fundamentals.

In the compressor sector high performance gas-lubricated seals can replace throttle rings labyrinth seals and oil-lubricated mechanical seals. Low leakage rates wear-free operation and an extremely low level of power consumption are key characteristics of gas-lubricated seals and the reasons for their high efficiency.

The advantages of the gas-lubricated seal can be applied just as easily in pumps and agitators. However where double seal arrangements are operated they must use a suitable buffer gas supply system. Sealing of fans blowers steam turbines and use as safety seals for liquid-pressurised mechanical seals are other applications.

In its basic design a gas-lubricated seal resembles a conventional balanced mechanical seal. The seal consists of a spring-loaded seal face and a seat. While one ring is designed to be stationary the other rotates together with the shaft. A distinction is made between seals in which springs are on the rotor (flexible rotor designs) and those in which the springs are behind the stationary seal face (flexible stator design). The seal face and the seat are sealed from the housing and shaft respectively by secondary seals. Silicon carbide silicon nitride tungsten carbide or carbon are the materials used to manufacture the seal face and the seat. The flat faces of the seal face and seat form the sliding faces. Gas grooves measuring just a few microns in depth are machined into one of the sliding faces.

Unlike liquid-lubricated mechanical seals a gas-lubricated seal uses a stable film of gas between the sliding faces to keep the faces apart. Complete separation of the sliding faces during operation is absolutely essential because contrary to liquid-lubricated mechanical seals a gas-lubricated seal would be unable to dissipate the heat of friction. Unlubricated operation with contact would soon lead to the destruction of the sliding faces. The sealing gap attained by the sliding faces measures no more than a few microns.. A highly stable film of gas is created by gas grooves worked into the one sealing face thus enabling the seal to work safely. The gas medium flows through the sealing gap and is relieved. A small gap width means that leakage rates are kept to a minimum.

When the machine is at a standstill the axially moveable seal face is pressed by springs against the sliding face of the seat. Parting of the two sliding faces is brought about by differential pressure and the rotation of the shaft. For the two sealing faces to be separated with zero pressurisation they would have to be moved at a relative speed of about 0.5m/s. This is called aerodynamic lift-off. With a sufficiently high pressure differential it is possible however to reduce the loft-off speed considerably or indeed to make it completely unnecessary. This is called aerostatic lift-off.

Seals with a rotating seal face (flexible rotor designs) are generally used only in the low to medium speed range on account of the rotating springs. Seal faces of staitonary (flexible stator) design are used for high speeds. Gases and solid-free liquids are sealed by gas-lubricated seals featuring external pressurisation. Seals for media-containing solids are open to the product side in order to prevent deposits and are equipped with rotating seats and internal pressurisation in order to stop particles from getting into the sealing gap.

Feodor Burgmann Dichtungswerke has published a 76-page reference book on gas-lubricated seals ,well worth reading.

• Feodor Burgmann
• Ellen Neubarth
• 00 49 81 7123 1453

September 1998

Where water levels have to be controlled, an innovative solenoid-operated coaxial valve has allowed automatic self-priming water pumps to work reliably and almost independently

In the past, water pumps have needed to be manually primed at regular intervals. Now, a new smart priming system from Sterling Pumps is a fully automatic vacuum priming system which will operate from dry condition to a suction lift of almost 10m at sea level. The system is then able to maintain intermittent flows without the need to manually re-prime the pumpset. The unit can run dry without any damage, useful where continuous monitoring is just not possible.

The reliability of the pumps has been increased considerably by replacing a conventional lateral solenoid-operated valve with a coaxial solenoid valve. The valves can handle water with high levels of solid contaminants like silt, and are used to ensure no water reaches the vacuum pump, which forms part of the main pump’s priming system.

There are difficulties with conventional valves for this application. Small pilot orifices are needed to assist the diaphragm or piston open and close. They may only be a millimetre in diameter but they easily get blocked. The solids in the water often obstruct the seal between the valve piston and its seating. If water is allowed to reach and damage the vacuum pump, it needs to be replaced, at around (UK pounds)1000 a time.

The direct acting coaxial valves from KV, on the other hand, have no pilot orifices. They operate instead by moving a cylinder through which the working medium flows. This arrangement makes the valve self-cleaning and ensures dependable operation, even in the presence of heavy contamination.

Also, because the coaxial valve spool is balanced, the power needed to actuate the solenoid valve is very small, even at high media pressures. The balanced construction therefore simplifies the design of the control system. Also, unlike conventional solenoid valves, they can withstand up to 16 bar back pressure.

A great advantage for this application is that the valve has snap-action operation, which is important for the self-priming water pump. A ball valve could also be used if all that was necessary was to guard against contamination, because it also has no internal orifices. But electrically operated ball valves take 50-60 seconds to work, which could mean small amounts of water carrying over into the vacuum system. Again, this probably would mean that the vacuum pump, which should only ever see air, would have to be replaced. KV’s coaxial solenoid valve snaps into action after 100ms, thus ensuring the reliability of the pump.

A conventional solenoid-operated valve from KV’s high reliability range further protects the vacuum system of the water pump. The valve is controlled from a level probe, and operates automatically if the water level in the pump’s break tank reaches an excessively high level. Again, this guards against water entering the vacuum system. A proximity switch can be installed in the valves to send a signal to the controller to give positive confirmation of the valve position.

The self-priming water pumps are more reliable because of the coaxial and process valves and less maintenance is needed. Originally the coaxial valves were developed for a machine-tool coolant system and are used to working media, which have solids. This greatly increases the pump’s ability to deal with contaminated media in the construction and waste water industries.

These new coaxial valves come in 2/2 and 3/2-way solenoid and external pilot versions, and KV can supply them for use with media at pressures up to 500 bar. The types range from small valves for use in dosing applications, to robust flanged high-flow types used in the petrochemical industry. There are also valves certified for use in hazardous areas.

• Sterling Pumps
• KV

May 2000

Is it possible to have a pneumatic actuator that gives slow, smooth motion as well as a highly dynamic response? Tommy Miller investigates the Air Muscle

Pneumatic cylinders are commonly used where linear motion is required, but there are many applications where they are unsuitable. Their reliance on moving parts and seals makes pneumatic cylinders liable to leakage and wear, and they are not usually suitable for use in harsh environments.

A novel type of actuator that has a number of advantages over pneumatic cylinders is now being marketed by the West Group. The ‘air muscle’ is a lightweight single-acting pneumatic linear actuator with a high power-to-weight ratio. Although it is operated by compressed air, the air muscle has little else in common with pneumatic cylinders; for example, applying pressure causes the device to contract instead of extend.

Continuous development

Air muscles have been in continuous development for advanced robotics and animatronics work for several years. In these applications the attractive characteristics of the air muscles are their ability to provide slow, smooth, controlled movement as well as highly dynamic movements with immediate response. Manufactured by Shadow Robotics, the air muscles are now available through the West Group for use in industrial applications as a powerful lightweight actuator. The basic principle used in the air muscle is similar to that of a biological muscle. Consisting of a hermetically sealed rubber tube that is wrapped in a tough plastic woven sheath, the actuator is expanded radially by air filling the tube. The specially-shaped weave deforms in such a manner as to make the tube shorten axially as it expands radially – creating an axial pulling force.

Depending on the size, air muscles weigh as little as 10g, but they can have a power-to-weight ratio as high as 400:1, vastly out-performing both pneumatic cylinders and DC motors that can only attain a ratio of about 16:1. This characteristic makes them particularly useful for applications where weight is critical.

Air muscles behave in a very different manner to pneumatic cylinders; as the air muscle contracts under constant pressure, the pulling force produced between the end points decreases. The maximum possible force at a given pressure is obtained when the Air Muscle is extended as far as possible; if it is not taut, then the full potential will not be yielded. Furthermore, the relationship between pressure and force is linear at constant extensions, allowing the movement to be controlled by regulating the applied pressure.

Because of their simplicity, air muscles are cheaper to buy and install than other actuators and pneumatic cylinders – prices start at around (UK pounds)6. Being flexible, they can be operated when twisted axially or bent around corners, and they do not need to be aligned precisely.

Being sealed, the air muscles are suitable for difficult or dangerous situations, including cleanrooms and explosive atmospheres. And, having no sliding or rotating parts, they are also well-suited to situations where there are fine, abrasive particles such as on woodworking and grinding machines. One recent application employed a series of air muscles to uniformly tension fibreglass hull mouldings during boat construction. It must be remembered, however, that the air muscle is not able to guide the load directly, so this must be catered for in the application’s design. Neither is it capable of taking compressive loads.

Available in four standard sizes of 12, 20, 30 and 50mm diameter with active lengths of 150, 210, 290 and 400mm respectively, the air muscles are able to provide up to 160kg pull, and are capable of contracting by as much as 40% of their original length. The strength of the muscle increases with increasing diameter, but changes in length influence only the resulting motion.

The West Group can supply batches of air muscles to different lengths if required, and with alternative end fittings. Meanwhile, plenty of information covering the standard products is available by using the free information card.

• West Group

April 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