HVAC - Choosing and Installing Expansion Joints in HVAC Systems

Why are HVAC expansion joints important?

Expansion joints or hose & braid are key components of any heating, ventilation, and air conditioning (HVAC) system to prevent stress being transferred to the pump due to thermal movement therefore avoiding unnecessary bearing wear or seal failure. As well as increasing the life of system components, well placed expansion joints or braided hoses in your HVAC system reduce vibration which in turn reduces noise. Noise reduction is especially important for larger operations, with more complex systems and low noise operation making for a better working environment for staff and visitors. Proco Products operates globally and helps companies to understand the role of correctly specified quality expansion joints in their systems with the optimal composition and design. We have to date prevented multiple downtime periods by identifying and replacing expansion joints as part of our preventative maintenance survey program

Placing Expansion Joints in HVAC Systems

Positioning and support are key to long term maintenance free system, a working expansion joint needs anchors, guides and supports. Anchoring is required both on straight pipeline runs and when the pipeline changes direction, and in all cases, expansion joints should be located as close as possible to anchor points. Ensure that piping to and from the location of a rubber expansion joint or braided hose is supported and guided to prevent the weight of the piping being transferred to the expansion joint. Here are three items to check when specifying expansion joints:

Anchoring System for Pipework

Employing high-quality, dependable anchors capable of withstanding joint pressure thrust and pipe motion forces is crucial. Supplementing anchors with control rods or limit bolts should be placed upstream and downstream of the expansion joints at both ends of the thermally expanding or contracting pipe length. Expansion joints will function without overextending with these full thrust anchors in place.

Pressure and Temperature Specification

Determine the temperature range and the pressure conditions that the expansion joint will encounter during operation. A useful tip to bear in mind is that expansion joints or flexible connectors should withstand four times the system working pressure to mitigate shock pressure effects.

Evaluate Vibration Reduction Needs

Vibration from operating pumps can affect HVAC system efficiency and cause noise disruption. Neoprene or EPDM expansion joints are the best materials to minimize vibration and ensure quiet operation or use of 321 Hose/304 Braid with C/S Plate Flanges or NPT threaded ends.

How to Check Pipeline Alignment When Fitting Expansion Joints

Piping misalignment in the system is important for the joint to perform correctly and should not exceed a maximum of ±1/8” as recommended by the Fluid Sealing Association (FSA). Where the maximum allowable misalignment is exceeded, the pipeline should be corrected before installation of the expansion joint takes place. Here is how to measure alignment:

Axial Alignment: To measure for axial misalignment, measure from the inside of one mating flange to the inside of the other, the area in which the expansion joint is to be installed.

Lateral Alignment: To measure lateral misalignment, place a level on the outer edge of the mating flanges and measure across. Repeat the measurement at least three times to obtain a total of four measurements evenly distributed around the circumference of the mating flanges (6-8 total measurements for large ID expansion joints).

Angular Alignment: To measure for angular misalignment between mating flanges, measure from the edge of one flange to the same corresponding spot on the opposing flange. Record this value and then repeat the same measurement on the opposite side of the flanges (180º from the initial measurement). Repeat these measurements to obtain a total of at least four paired measurements evenly distributed around the circumference of the flanges. Compare the measured dimensions and any variation in the measured dimensions indicates that the mating flanges are not parallel and are angularly misaligned. Check the flange bolt pattern on each mating flange and ensure the bolt holes on each flange line up to each other.

Torsional Alignment: Check the flange bolt pattern on each mating flange and ensure the bolt holes on each flange line up to each other. Any variation will indicate a torsional misalignment.

How to Check for Concurrent Movement When Fitting Expansion Joints

Concurrent movements occur when two or more movements in a pipe system happen at the same time. To calculate concurrent movement, use the following formula:

(Actual Axial / Rated Axial) + (Actual Lateral / Rated Lateral) + (Actual Angular / Rated Angular) + (Actual Torsional / Rated Torsional) < 1

A result of < 1 is needed to allow an expansion joint to operate within concurrent movement capabilities.

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Types of HVAC Expansion Joints

Rubber Expansion Joints:

Rubber expansion joints offer high flexibility, they are also cost effective, corrosion resistant and easy to install. Proco Style 240 molded single-sphere rubber expansion joints are the logical choice for absorption of directional movement, vibration, noise and shock.

PTFE Expansion Joints:

Within environments that require a non-reactive material, moulded PTFE or PTFE lined rubber expansion joints can withstand extreme temperatures, ranging from -200°C to +260°C. With low permeability, PTFE also helps prevent leakage. See our PTFE expansion joints.

Ducting Expansion Joints:

Ducting expansion joints are designed to add flexibility to ducting systems, effectively isolating vibration, and noise in industrial environments. These are recommended for movement absorption and thermal expansion. See our ducting expansion joints.

Braided Pipe Connectors:

Systems which feature braided metal hose are designed to control vibration, reduce noise, relieve stress and compensate for potential misalignment while withstanding higher operational temperature and pressures. These connectors are made from a variety of different metals, including copper and stainless steel, to suit pumps, compressors and other heavy equipment. Proco Products designs and manufactures leading braided pipe connectors which support the internal hose to withstand pressure whilst allowing necessary movement. See our braided pipe connectors.

Pipe Penetration Seals:

Pipe penetration seals provides a robust, watertight seal for pipes passing through walls, floors, or tanks, ensuring efficient HVAC system performance. These provide long lasting protection against air leakage, water infiltration and fire spread when installed and maintained properly. See our pipe penetration seals.

Tips For Storing and Protecting Rubber Expansion Joints

  • Use a dry, cool location for storing an expansion joint. Store face down on a pallet or wooden platform without any other boxes on top of expansion joint or expansion joint box.
  • Remember when welding near an expansion joint, that splatter can damage rubber material. It is recommended to use a welding blanket to protect against damage.
  • It is suggested not to insulate a non-metallic expansion joint however if insulation is required, it should be removable to permit easy access for periodic inspection of the expansion joint material and tightening of expansion joint bolts. Note that insulation could cause restriction of expansion joint movement and heating of the expansion joint material to exceed the maximum rated capability.
  • Inspect the mating flanges to ensure that they are clean before installing the rubber expansion joint.

See more about selecting expansion joints and a summary of Why do HVAC systems need expansion joints?

Contact Proco Products for Expansion Joints in HVAC Systems

Proco operates worldwide and maintains one of the largest product inventories in North America. For more information on expansion joints from Proco Products, Inc. and to check pricing and availability, contact us today. 

To find out more about sealing standards, safety, reliability and best practices see the Fluid Sealing Association.