Rotary Unions, Swivel Joints,
Air Breather Filters, Flexible Hoses


Designed and Manufactured in the UK, Supplied Worldwide for over 75 years.

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The History of Filton - the 1990's

Wednesday 22nd June 2022

This year we are celebrating 80 years in manufacturing. Today's blog looks at the variety of special joints that we developed during the 1990’s.

Luckily the 1990’s began on a more positive note than the 1980’s.  For Filton there continued to be a wide variety of applications for special purpose products.  The proportion of the company’s turnover for specials increased but the volume of standard products dropped during this time.


The UK market lost a number of important machine builders during the 1980’s and this continued to a lesser extent during the 1990’s. This explained the reduction in the need for standard products in the home market. 


The major machinery builders in Europe were now located in Germany and Italy. Efforts in Germany compensated to some extent for the reduction in the sales of standard products in the UK but the main growth was seen in semi-standard products for machinery – mainly in the plastics industry.


One area of growth for special Rotary Unions and Swivel Joints was in the pharmaceutical industry. Rotary filling machines were utilised for example, for inhalers used for the treatment of asthma. The units were mainly double flow types for use on powered drug and propellant gas. The construction was mainly from stainless-steel with the internal design made to reduce areas where the drug could trap and to aid the cleaning process.


Following the success with the Rotary Union for the French blow moulding machines (in the late 80’s), a very wide range of special Rotary Unions were designed which varied from modified standards to complete bespoke units.  A typical variation on standard units was to equip them to carry 4 flows rather than the normal 2.  Generally, these were for water heating and water chilling circuits for the bottle moulds.  Other variations were for compressed air systems ranging from 12 bar to 40 bar.


During the construction of the channel tunnel locomotives were used to pull the trains for the undersea construction services.  There was an application on these engines for a Rotary Union on the transmission system.  A pneumatic clutch was used and a Rotary Union was needed to transfer air at 10 bar through the rotating shaft.  The fairly high shaft speed and lack of flow of the compressed air easily creates overheating due to seal face friction.  A balanced Filton mechanical seal was therefore used instead of the standard bellows seal.  This was also advantageous in resisting inherent vibration which can cause bellows to oscillate, depending on their natural frequency.


Around the same time an unusual application for a Filton Air Breather Filter occurred in connection with a gearbox for a high-speed railway locomotive. Initial trials gave problems due to the vibration, but a minor modification resolved this.  Due to the speed of gears within the gearbox and movement of the locomotive, oil was splashing up into the Breather covering the element and preventing the air from breathing correctly, to maintain atmospheric pressure within the gearbox.  The stem of the Breather was redesigned successfully with a baffle to prevent the oil reaching the element but allowing it to drain back into the gearbox.


The UK machine tool industry almost disappeared during the 1980’s, however, Filton had a small resurgence of interest in the 1990’s.  One application was for the coolant supply on a fairly large gun drilling application.  This required a 2 ½” nominal bore Rotary Union for a 20 bar coolant system pressure with a fairly high rotational speed.


Although the coolant was, in theory, clean, at times small swarf particles could be expected.  To cope with this situation the Filton mechanical seal used was fitted with a pair of tungsten carbide seal faces and situated out of the main coolant flow.  To obtain above average bearing life a pair of angular contact ball bearings were used instead of the conventional deep groove ball bearings to cope with the high thrust force experienced from the system pressure.


Another machine tool application was on automatic indexing heads.  To overcome space problems the bearing and seal arrangements from 3/8” nominal bore Rotary Unions were modified and built into the customer’s machine parts.  The application for coolant supply was critical and to avoid potential leakage problems the customer sent the machine components for Filton to complete with the seal parts and to carry out final pressure testing.


Through the Filton distributor in the Netherlands an enquiry was received for a Rotary Union to transmit cooling water to the take off rollers on a continuous casting machine in the steel industry. The take off rollers were designed with a counterbore for the Rotary Union to be inserted rather than cantilevered from the roller end.


The Filton distributor in Switzerland was approached with a problem with packed glands and mechanical seals on a waste water pump.  The water was contaminated with solids which jammed the close clearances in the mechanical seal hence losing its flexibility and leaking.  Furthermore, there was an angular variation of the rotary shaft with respect to the stationary housing.  The Filton bellows seal coped with the angular misalignment and was unaffected by the solids in the water due to the comparatively wide gaps between the bellows convolutions.  This 4” bellows seal fitted into the pump with minor housing modifications for the stationary bellows sub-assembly.  The rotary part of the seal was fitted to the pump shaft by utilising a clamped sleeve.


Following feedback from some customers regarding the ‘look’ of the Filton (RE) range, all were painted cast iron, Filton’s Rotary (PB) Union range was developed. This used a gravity diecast brass body. The choice of brass was carefully made as some waters leach out the zinc from brass in a very short time. A de-zincification resistant brass was chosen for the body to combat the potential problem, even though the cost was slightly higher than a conventional brass specification.


A variety of external shapes were considered, whilst keeping the seals and bearings identical to the Rotary (RE) Union. Originally it was planned that the cast iron range would be phased out to be replaced by the brass union range.  However, there were still many customers who demanded the cast iron unions and therefore the two ranges continue to run parallel to this day!

An interesting and unique enquiry came from a well known brewery to discuss the use of a Rotary Union on a filling machine.  Although cans had been filled for many years this was a new application for a new drinking experience. The Rotary Union was manufactured from stainless steel and had a body of 9”, an overall length of 29” and contained 6 Filton mechanical seals.  The seals were to withstand nitrogen, compressed air and typical beverage industry cleaning fluids with ports of different sizes.


A Swivel Joint was required to convey a 2” nominal bore air supply with the union immersed up to 200 metres (656 feet) under the sea.  A single seal was used for the air system and double seals were used to prevent the sea water entering the bearing chamber.  Additionally, the unit had to cope with a tensile force of 15 tonne, therefore a double row angular contact ball bearing was used.  Both stationary and rotary connections were special bolting flanges designed by the customer.  The apparatus also had to withstand sea temperatures from arctic to tropical.  The main material of construction was stainless steel with monel fasteners.


In the late 90’s a marine application enquiry was received for an hydraulic Swivel Joint on a sea-going sailing vessel.  The Swivel Joint had to be mounted on the bottom of the mast and had a bore size of 19.7” and an outer diameter of 25.7” with an approximate weight of 240 kg. Phospor bronze and stainless steel were used for the construction. The sailing vessel went on to sail all around the world.

This particular application would have delighted William Murray following his early shipyard experiences.


Next month – a new century.


If you have any questions or if we can help you with your applications you can contact us either by phone on +44 1926 423191 or emailing us on or


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