Union End Metal Bellows

FlexEJ union-end HVAC axial compression expansion joints come with a BSP union swivel at both ends complete with fibre washer and stainless steel convoluted bellows from DN15 (15mm) to DN50 (50mm):


Union End Metal Bellows

What is a Union End Metal Bellow?

BSP female unions for threaded connections and axial compression..

  • Materials
    Stainless steel 316 bellows with iron BSP unions.
  • Application
    Heating water and most water services, not suitable for drinking water.
  • Rating
    6 Barg @ 150°C.
  • Web Shop
    Available online with next day delivery from our web shop.

How to specify a metal expansion joint

1 Standard or Engineered?2 Movements & Cycles3 Temperature & Pressure4 Media Compatibility5 Diameter, Length & Ends6 Let us help
Metal bellow engineeringWe design and manufacture metal expansion joints so you are not restricted to our range of standard products, some of which are available in our web shop. For simpler applications a standard product may be entirely suitable but if not we will design to meet your exact requirements.
Metal bellow movementMetal bellows have a defined fatigue life based on movement cycles. Understanding the movements, if they are concurrent or not and the realistic number of times the movements can occur is fundamental to metal bellows design.
Metal bellow pressureMetal bellows work well up to around 500ºC, above that we use insulation to control the actual bellows metal temperature if the media is above this temperature. Pressure and temperature must be known to select a metal expansion joint.
Metal bellow compatibilityThe most common material used for metal bellows is Stainless Steel - 304, 321, 316 - and for more demanding applications Nickel Alloys - 625, 800, 825. Corrosion is the most likely failure mode for the bellows itself so the correct material selection is important.
Metal bellow diametersOur standard ranges have set lengths for each diameter / movement range but we can design to meet your exact requirements. Making the bellows longer will increase the available movement. Most commonly a flange, we can provide to any specification, or pipe weld ends. Our HVAC standard product is available with BSP Union ends and Copper Pipe ends. If you are uncertain about what flange type you already have installed our Flange Finder will help you identify it.
Metal bellow Help Call our expert team on +44 (0) 1384 881188 or email us at sales@flexej.co.uk or use Live Chat on this web site - we are here to help, please get in touch.

Can't see what you want? Need help?

Call us. Or use Live Chat.

For instant advice. We can custom-design and engineer almost any expansion joint you need for delivery in the UK or worldwide. Call our expert team on +44 (0) 1384 881188. Or email us sales@flexej.co.uk

FlexEJ's Union End Metal Bellows

For use on threaded connections and axial compression

316 stainless steel bellows Threaded female BSP
Iron swivel unions Rated 6 Barg @ 150°C
Minimum length design For axial compression

Union End Metal Bellows


All sizes available from our web shop

For ratings and dimensions please see our catalogue or range tab above.

Got a quick question?

Use Live Chat. Or call us.

For instant advice use the Live Chat link to message one of the sales team. Or call them direct on +44 (0) 1384 881188

HVAC Union End Metal Bellows Product Comparison Chart

Is the HVAC Union End metal bellows the best option for your application? Two potential alternatives to consider:

Not sure what flange spec you need?

Use the FlexEJ Flange Finder to find out

FlexEJ stock a full range of specs and types for our bellows. Or call our expert team on +44 (0) 1384 881188.


Who can you talk to?

Try our sales and customer service team on 01384 881188

They don't bite. And they know what they're talking about. Call the team any time from 8:30am to 3:30pm weekdays, 12:30pm Fridays or use LIVE CHAT if you would prefer a quick text answer. For more complex queries, send us any pro-forma documentation using the get a quote form below or email us sales@flexej.co.uk.

Call Us

Can't quite find the right bellow?

Try the FlexEJ Bellows Finder

Or call our expert team on +44 (0) 1384 881188

Frequently Asked Questions

Q. Do you hold stock of metal bellows ?
A. Yes. We hold stock of the most popular metal bellows for HVAC. Many of these items are available on 24hr delivery from our online web shop. We can also manufacture to order. For sales assistance please contact us or use our Live Chat facility. In addition, FlexEJ holds a large stock of the most popular sizes and types of Elaflex rubber bellows as well as our HVAC value bellows range.
Q. How do you identify flanges?
A. Our Flange Finder contains details for many common flanges. Typically, to be able to make the identification you need to know the bore size or outside diameter and number of bolts. For technical assistance contact us or use our Live Chat facility.
Q. Do you design your own metal expansion joints or rubber bellows?
A. Yes, FlexEJ has full design capability for engineered metal expansion joints and can work to any recognised standard – typically EJMA, B31.3/Appendix X, EN14917 plus PED and/or other customer specifications. Engineered rubber expansion joints are typically designed to meet the FSA guidelines plus PED and/or other customer specifications For technical assistance please contact us or use the Live Help link on this page.
Q. Can you match another brand / manufacturer of expansion joint or bellows?
A. Yes, if you have the details we can normally offer an equivalent, our FAQ here gives the information we will need for a full selection. For technical assistance please contact us or use the Live Chat link on this page.
Q. What do I need to know to identify an existing expansion joint or bellows?
A. To identify an existing expansion joint we need to know: nominal bore, overall length and flange type plus service, temperature, pressure and required movement if known. Try our Flange Finder to help identify the flange and you can send us a picture of the existing part using the Contact us form. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. Do you have metal bellows for drinking / potable water or with WRAS approval?
A. Yes, our MRCA copper ended metal expansion joints also have WRAS approval. We laso have DWI approval for stainless steel expansion joints. For technical assistance please contact us or use the Live Chat link on this page.

Please visit our full FAQ page to see all our frequently asked questions.

Need a detailed quote?

Get A Quote. On us.

We will provide full technical details together with, pricing and shipping timescales. For more complex engineered quotes, preliminary sketches and calculations will be available.

Got a quick question?

Use Live Chat. Or call us.

For instant advice use the Live Chat link to message one of the sales team. Or call them direct on +44 (0) 1384 881188

Get A Quote

Please complete the short form here and we'll get back to you within 24hrs Monday to Friday (quicker if marked urgent).

Alternatively, you can also call our expert team directly on +44 (0) 1384 881 118 from 8:30AM to 4:30PM weekdays (12:30PM Fridays), who will be only too pleased to talk through your requirements and technical queries over the phone.

Visitors are also welcome Monday to Friday although please get in touch beforehand to let us know you're coming.

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    Industry experience

    FLEXEJ Ltd was formed in 2002 by two professional engineers who brought together an already highly respected design capability with business and commercial skills gained in large multinational companies.
    • Our focus has always been on application and design – helping our customers find the best value solution.
    • We have a strong engineering and manufacturing team with experience in petrochemicals, refining, nuclear, desalination though to HVAC.
    • The team is also very familiar with meeting complex requirements for documentation, in process NDT and test on projects. We have supplied many large end-users such as EDF, Exxon, Shell, Reliance & QatarGas working with major contractors such as JGC, Foster Wheeler & Technip.
    FlexEJ Industry Experience