Mechanical Engineering, bridge bearings, structural engineering Specialists In Structural Movement Control

Ekspan EQF Sliding Strip

Modular sliding bearings are used extensively to permit structural movement to take place with the minimum coefficient of friction. Often. the excellent properties of PTFE fail to be realized because of the use of inadequate mating surfaces or a poor method of application.

 

Ekspan EQF is a most advantageous way to use PTFE for sliding supports.

 

1. The PTFE is retained mechanically in a steel backing strip.

2. Under the designed loads the PTFE will not cold flow.

3. Ekspan EQF strip is easily attached to the support members. e.g. by welding  or screwing. Hence the problems of adhesive bonding caused by inadequate preparation, unskilled labour andunsuitable working conditions, are eliminated.

 

Ekspan EQF is designed to enable engineers to obtainfull advantage of the low frictional properties of PTFE by offering it in a form which is easy to handle and fix. Its steel backing can be welded. screwed or riveted to the sub-base. Provided the working environment is suitable and skilled labour is available, adhesive bonding may be used.The design details of Ekspan EQF are shown here. PTFE discs are inset in steel strip, which provides a rigid backing and securely retains the PTFE to restrict cold flow under load.

 

Friction

When Ekspan EQF slides against the recommended mating surface, polished stainless steel, at the maximum continuous loading and at sliding speeds below 2 mm/second at normal atmospherictemperatures, a coefficient of friction of 0.05 should be used.

 

High Temperatures

At sustained temperatures above 100°C we recommend use of an alternative DU bearing material.If high temperatures apply, please specify when ordering.

 

Mating Surface

We recommend polished stainless steel sheet affixed to a flat steel backing plate. We stock stainless steel sheet of the requisite standard and can supply as sheet cut to size or fixed to a steel backing plate. See below for the size calculation.

 

Mating Plate Size

Ekspan EQF strip should remain covered at the extremes of movement of the mating surface. Add the total movements in each direction to the length and width of the EQF strip. See diagram:-Standard Sizes Ekspan EQF is manufactured in 1.0 metre lengths.Shorter lengths are available in multiples of the strip width, e.g. EQF50 can be cut to lengths of 50, 100,150mm etc. We will be pleased to supply the mating surfaces when required.

 

Installation Notes

Welding -Tack welding to a steel sub-base is sufficient.Fixing by Screws or Rivets -Drill holes along the edges of the strip and between the PTFE discs, countersink if required and secure to backing plate or concrete plinth as appropriate.Bonding -Use only adhesives recommended for the materials to be bonded. Follow the adhesivemanufacturers’ instructions. CLEANLINESS is essential.Painting - Ekspan “EQF” strip is supplied primer painted only. The strip should be finish painted during installation to a level appropriate to the working environment.Note:  Should the PTFE surface be accidentally painted, it can be wiped with a clean cloth.

 

CAUTION

The “EQF” strip and its mating surface should be installed on to a smooth flat surface capable of providing uniform support. Failure to install correctly may cause uneven loading of the PTFE resulting in unsatisfactory performance and possible damage. Care should be taken to seal the edges around the EQF strip to prevent the ingress of moisture. If welding is used make sure that the PTFE faces are protected from welding spatter. Any spatter on the bearing surface must be removed before assembling the stainless steel mating surface.