FLUOROGLIDE® SLIDE BEARINGS AND PIPE SUPPORTS
Featured Product from Fluorocarbon Company Ltd
Fluoroglide® PTFE slide bearings are implemented to solve problems of a structure that moves as a result of thermal, seismic or differential force. PTFE Slide bearings operate at high loads and low speeds, and it is under these conditions that the self-lubricating properties of Fluorinoid® PTFE are at a maximum.
This, together with its no stick-slip and anti-weathering characteristics, is the main reason why Fluorinoid® PTFE has proved successful as a material for Fluoroglide® PTFE slide bearings.
THE SLIDE BEARING
Normally, a slide bearing consists simply of two pads of PTFE sliding against each other; for very high-pressure applications, a single pad may be used to counter face a polished stainless steel plate. The assembly is manufactured so that one pad (generally the top pad) is larger than the other by an amount in excess of the expected movement, so keeping the contact area constant throughout the cycle of motion.
TECHNICAL ADVANTAGES OF FLUOROGLIDE® PTFE SLIDE BEARINGS
- PTFE has the lowest coefficient of friction of any known solid 'engineering material' including lubricated metal.
- There is no stick-slip action.
- Fluoroglide® slide bearings have near infinite life, since chemicals and weather have no effect on PTFE - moisture absorption is less than 0.01% even under icing conditions or immersion, and the material is chemically inert.
- No maintenance is required. Fluorinoid® PTFE will never cold weld to itself and therefore requires no lubrication.
- Fluoroglide® slide bearings are easily installed, either pre-assembled or on site.
- Fluoroglide® slide bearings are less bulky than alternative assemblies.
- There is no possibility of fatigue failure.
- Electrical and thermal insulation minimise galvanic corrosion and heat transfer.
- Vibrations are dampened.
- Small particles which may become embedded do not cause binding of the surfaces.
- Fluoroglide® slide bearings can accommodate some misalignment in construction without setting up stress corrosion along a leading edge, as can occur in conventional bearings
PTFE SLIDE BEARING APPLICATIONS
- Heat exchangers
- Concrete decks
- Oil & water transportation
- Storage tanks/plants
- Buildings - multi-storey car parks, civic centres etc
- Subsea pumping stations
- Pedestrian walkways
OUR SLIDE BEARING SERVICE
- Fluorocarbon Company produces Fluoroglide® slide bearings in a range of configurations, though each bearing is designed specifically to suit the application.
- The basic element is usually 2.5mm Fluorinoid® PTFE sheet, factory bonded onto a 3mm carbon steel backing plate for straightforward field installation by welding or bolting.
- Alternative thicknesses and materials for the backing plate can be supplied. i.e. stainless steel 304 or 316
- Where operating conditions require them, thermal insulation and vibration dampening pads may be bonded between the backing plate and the structure.
- To allow operation at high ambient temperature, a high temperature epoxy resin is used for bonding and the adhesives are cured under strictly controlled conditions, ensuring that the bond is stronger than the PTFE itself.
- Peel testing results can be supplied where required
- Either virgin or glass filled Fluorinoid® PTFE is used as the slide bearing material.
- Fluorinoid F100 PTFE is recommended for bearing pressures up to around 70kg/cm² (7N/mm²).
- Using Fluorinoid® FL129 the load bearing capacity is increased to 140kg/cm² (14N/mm²).
- Loads in excess of these can be accommodated by confining the material within a recessed housing and by using a polished stainless steel counter plate - proposed configurations should be discussed with our designers
The slide bearing components can be fixed to the installation by bolting, tack-welding, full welding or mortar embedment, and the appropriate type of bearing should be chosen according to the installation method. During slide bearing installation the PTFE surface should be adequately protected against weld spatter, paint spray, etc.
PTFE SLIDE BEARING CONSIDERATIONS
The following steps will provide an indication of the slide bearing requirements for a particular application:
- Determine the total load of structure - this will indicate the total slide bearing area required at a suitable bearing pressure and temperature.
- Decide the number and positions of the slide bearings according to the rigidity and function of the structure.
- Take account of operating environment and specify grades of steel for backing plates.
- Consider any unusual conditions affecting the slide bearings, such as the need for additional thermal insulation, vibration pads and deflection of slide bearing surface.
- Decide the most appropriate method of mounting the slide bearings.
- Select the types of slide bearings required from the recommended design chart and specify their dimensions.
BONDING OF PTFE
We recommend chemical bonding for locating the slide bearing material on its support. The shear value of the epoxy adhesive is greater than that of the PTFE.
Our bonded Fluorinoid® PTFE elements supplied to meet the requirements of BS5400 and we recommend the use of black, glass-filled Fluorinoid® PTFE to ensure the slide bearing bond is not affected by exposure to ultraviolet light.
Site bonding of PTFE is not recommended - strictly controlled conditions of cleanliness, pressure and temperature are required to obtain a satisfactory bond between the PTFE and substrate. If site slide bearing bonding is unavoidable, we recommend that Fluorocarbon engineers are consulted.
From basic Fluorocarbon tests coupled with independent and empirical testing, the ideal thickness has been found to be 2.5mm, although this can be reduced to 1.5mm as an absolute minimum. This is thin enough to achieve the maximum reduction in cold flow and creep, yet thick enough to allow for some constructional misalignment and to allow for dirt and grit embedment.
The top slide bearing pad should be larger than the bottom slide bearing pad by an amount in excess of the expected movement, in order to maintain a constant contact area and prevent ingress of dirt on to the bearing surfaces.
The temperature at the surface of the PTFE should generally be less than 120°C and should never exceed 200°C. Typical data suggests that under normal conditions the temperature falls by 200°C for every 100mm from the heat source (in ambient air).
However, if the slide bearing temperature is likely to exceed 120°C a thermal insulator should be fitted between the structure and the slide bearing back plate.
VIBRATION / ACOUSTIC DAMPING PADS
Slide bearing units can be built with a variety of elastomeric composite interlayer’s or backings to suit customer's parameters when acoustic or vibration damping is necessary. Elastomers may be used when simple angular or rotational movements are required.