Client:Thermal Expansion Assistance
Date:April 16, 2012

HASL Pipework Thermal Expansion


We, along with our partner manufacturers, are able to provide a full support service for the provision of both building movement and thermal expansion with full calculations to support the appropriate selection of bellows, anchors and guides.

In addition our unique software will demonstrate the resultant movement, support centres, pipework clearances required and much, much more to allow a fully considered solution to be applied.

Reliable Piping  Systems

The consideration of thermal expansion in pipework systems is often left far too late in the construction program. Once pipe routes have been fixed and brackets and supports have been selected it makes it much harder and sometimes even impossible to make adequate provisions for thermal growth due to temperature changes.

Example Of Pipe Work:

If pipes are designed to run too close to the ceiling and are suspended on short drop rods they will allow hardly any movement. Drop rods should be at least 12 x expansion and should have a swivel at both ends.

Significant savings can be made if expansion is considered at an early design stage when pipe routes and supporting methods can still be changed. With over 30 years of experience HASL can value engineer the piping design, minimizing the amount of expansion joints required, reducing anchor loads and optimising pipe guiding and anchoring.

Quality is Assured

BOA has a Lloyds Register accredited Quality Management System to ISO 9001. Their expansion joints are designed to the American EJMA standard, which incorporates large safety factors. All products are manufactured and finished to the highest standard using approved weld procedures to EN 288. Material certificates to EN 10204 and pressure test certificates are available upon request.

Advice Service

We have many years experience in analysing pipework expansion compensation. We stake our reputation on only including expansion joints where there is no alternative. Our engineers can often reduce the cost of a system providing they are involved at an early design stage, as the most economical solution should not just consider the cost of the expansion joint but also take into account the cost of anchoring, guiding and installation.

Frequently expansion joints are not required and can be designed out by using the natural flexibility of the pipework. Our rea Engineers are always pleased to advise you.

Unrestrained Expansion Joints

Axial Expansion Joints are the simplest way of absorbing expansion in pipework systems. They are designed to be installed in a straight run of pipe where they absorb axial (or longitudinal) expansion by being compressed. The fact that they can only compensate for expansion in one plane limits their application and offers little opportunity for engineering initiative. If it is not possible to build anchors of sufficient strength, a restrained expansion joint must be used. It is usually either not possible or uneconomical to use unrestrained units at high level.

Restrained Expansion Joints

Lateral, Anular or Gimbal Expansion Joints are designed not to extend when an internal pressure is applied.  The pressure thrust reaction force is restrained by means of hinges or tie bars. These Restrained Expansion Joints are versatile and can be used in many different configurations and combinations. The loads imposed on anchors is generally much lower than for unrestrained, axial, types. Movement in angular expansion joints and lateral expansion joints is achieved by controlled angulation of two bellows in opposite directions. They can generally only absorb movement at 90° to their axis. Angular expansion joints have to be used in pairs (2 pin system) or in threes (3 pin system).

The anchor load imposed by all restrained units is the sum of their spring rate plus restraint friction losses. However, generally the frictional loads caused by the pipe supports are by far the largest component of anchor load. No special guiding is required and they are therefore suitable for mounting at high level or wherever guiding and anchoring may prove difficult or expensive.

Restrained expansion joints are more complex than axial units and are therefore more expensive.However, to offset the higher cost, savings can result from reduced need for guiding anchoring and number of expansion Joints.


To offer fully integrated solutions to contractors HASL have developed their own range of low friction guides and a unique anchoring system which form part of a value engineered design solution.

The new range of pipe guides have been specifically developed to minimise guide friction and to accurately control the thermal expansion of pipes. All our experience has gone into the design of the guide to make it the most advanced on the market. HASL guides are precision engineered and incorporate a unique ultra low friction bearing surface to minimise anchor loads. It is important that pipe work expansion is accurately controlled allowing easy axial movement while guiding the pipe with minimal lateral tolerances.

The particular design limits lateral movement to less than 1mm while allowing up to 80mm of expansion as standard. The range has been developed specifically to work in conjunction with the BOA expansion joints. By using highly flexible multiply bellows with low reactive loads and ultra low friction guides, anchor forces and loads on the building structure can be substantially reduced resulting in tangible cost savings.


Completing the range is an innovative type of anchoring system. The HASL anchors are designed to be space saving and quick to install. Their unique clamping system fixes to the pipe without the need for welding. They then bolt to the soffit or a solid wall using four legs. These can be cut to size on site to exactly much the distance from the pipe to the soffit.

The HASL anchors not only restricts axial movement but also stabilizes the pipes laterally.

Please contact us  and we can guide you through to a fully engineered solution.