Frequently Asked Questions


If you have any questions you would like to ask us directly please use the Contact Us form below or call us on +44 (0) 1384 881 188 or use the Live Chat facility for an immediate response to anything you require. Please see our frequently asked questions and answers below. Use may also use the form to ask a new question about FlexEJ's products and services.

AIR AND DIRT SEPARATORS

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. Are FlexEJ’s Air and Dirt Separators available to purchase directly online?
A. Yes, the majority of FlexEJ’s current range of Air and Dirt Separators are available from the FlexEJ shop on a same-day despatch basis although our largest Air and Dirt Separators (DN100 to DN150) need to be pallet-delivered and require an extra 2-3 days for delivery. We can also supply Air and Dirt Separators on an ongoing OEM basis and can cater for custom requirements. Please ask for details.
Q. What is the delivery time for air & dirt separators?
A. Most of our air & dirt separators are available from stock on a 24hr delivery basis. Non-stock separators or custom-manufactured items typically take 7-14 working days, depending on options and quantities required.

APPLICATIONS

Q. Where should expansion joints or bellows be used?
A. There are three broad applications which may exist in any combination:

> to reduce vibration or noise being transmitted through the piping
> to allow for installation misalignment in the piping
> to allow piping to move in operation, normally due to thermal growth, so to avoid high pipe stress and loads on equipment.

If significant thermal movement is expected, a pipe stress analysis should be carried out for the system and that analysis will identify the ideal location for any expansion joints required to achieve acceptable pipe stress and loads. For technical assistance contact us or use our Live Chat facility.

Q. What information do I need to design or select a rubber bellows or metal expansion joint?
A. To design or select a rubber bellows or metal expansion joint we need to know: nominal bore, end type, service, temperature, pressure and required movements. You may also specify in addition your requirements for external hardware – tie rods, hinges, gimbals – internal liner, external cover and instrumentation. Material selections should also be specified to suit the service and associated system piping. For technical assistance please 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. What kind of expansion bellow do I need for different media types?
A. Do use FlexEJ’s new Bellows Finder available on our Expansion Joints page to find recommended expansion joints by media (application) such as waters, oils, acids, etc, as well as by bore size, length, end type and more. Generally speaking, any of our HVAC bellows (rubber or metal) might be suitable for general purposes whereas our high-quality Elaflex ranges are recommended for more specific requirements you may have. And metal expansion joints can generally be designed and built to accommodate any media and temperature range, environment and pressure ranges you are likely to encounter. Do call us or use LIVE CHAT for more direct advice.

DOSING POTS

Q. What connections do your dosing pots support?
All our stock chemical dosing pots come preconfigured using DN25 PN40 female-threaded ball valves. We can manufacture to other specifications but not from stock.

ELAFLEX

Q. Do you hold stock of rubber bellows?
A. Yes. FlexEJ holds a large stock of the most popular sizes and types of Elaflex rubber bellows as well as our HVAC value bellows range. We also 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.
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. How do you install a rubber bellows or a metal bellows?
A. Please refer to our guidelines for installation, anchoring & guides. They are available in the Downloads section of this website: Elaflex Rubber Bellows Installation Instructions and FlexEJ Metal Bellows Installation Instructions. For technical assistance please contact us or use our Live Chat facility.
Q. Do you have rubber bellows for drinking / potable water or with WRAS approval?
A. Yes, our Elaflex ERV-R and ERP rubber bellows have WRAS, DVGW and ACS approval for drinking water. The Safetech manufactured to order rubber bellows can be supplied with WRAS approved EPDM linings. Our MRCA copper ended metal expansion joints also have WRAS approval. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. Are your Elaflex bellows available to purchase directly online?
A. The ERP Redspot, ERV-R Redband and Rotex DoubleRed bellows are now available from FLEXEJDIRECT from stock for the most common sizes and configuration of these popular high-quality bellows. The shop items and can be despatched same day (Monday to Thursday) on a 24hr service if in stock. More advanced configurations and the other nine Elaflex bellows ranges are available to assemble to exact specifications and typically take 7-10 days (depending on size, quantities and configurations required).

EXPANSION JOINTS

Q. What is spring rate?
A. Spring rate is the reaction force of the bellows when it is moved. It is a different force to pressure thrust – both forces act together on the piping. For technical assistance contact us or use our Live Chat facility.
Q. What does bellows ply mean?
A. This is a metal bellows term : ply refers to the number of sheets of metal used in the forming of the bellows, so a 2 ply bellows is made from two sheets of material. A multi ply bellows is generally more flexible that an equivalent single ply bellows. For technical assistance please contact us
Q. What is the difference between a bellows and an expansion joint?
A. In this field, the terminology can be confusing, often with no universally accepted meaning. We tend to use the following definitions but the terms “bellows” and “expansion joint” are typically considered as interchangeable:

> Expansion Joint – an expansion joint is a complete unit with metal bellows or rubber bellows and end fittings, plus, optionally, liner, cover and external hardware. Other terms used : compensator, flexible connector.

> Rubber Bellows – the flexible element within a rubber expansion joint

> Metal Bellows – the flexible element within a metal expansion joint

> Liner – The liner fits within the expansion joint under the metal bellows or rubber bellows to prevent the flowing media directly impinging on the bellows. This this reduces flow disturbance and allows the temperature of the bellows to be controlled in the design.

For technical assistance please contact us or use our Live Chat facility.

Q. What are tie rods or a tied metal or rubber bellows?
A. A tie rod is a simple pressure thrust restraint. It will allow reasonable lateral movement but not axial extension; it can allow axial compression if the pressure thrust is overcome by the piping movement. See the movements and pressure thrust FAQs for definitions. For technical assistance please contact us or use our Live Chat facility.
Q. What is pressure thrust or force?
A. All expansion joints exert a force, pushing the pipe ends apart – pressure thrust – which is proportional to the operating pressure and diameter of the bellows. If the expansion joint is unrestrained the piping system must withstand the force, or, alternatively, the expansion joint may have restraints built in to constrain the pressure thrust force. For instance types, tie rod, hinge or gimbal.

For technical assistance please contact us or use our Live Chat facility.

Q. What information do I need to design or select a rubber bellows or metal expansion joint?
A. To design or select a rubber bellows or metal expansion joint we need to know: nominal bore, end type, service, temperature, pressure and required movements. You may also specify in addition your requirements for external hardware – tie rods, hinges, gimbals – internal liner, external cover and instrumentation. Material selections should also be specified to suit the service and associated system piping. For technical assistance please contact us or use our Live Chat facility.
Q. What is EJMA?
A. The EJMA is the Expansion Joints Manufacturers Association. Their bellows calculation method is most frequently used for metal bellows expansion joint design. EJMA does not cover rubber bellows or metal hose design. For technical assistance please contact us or use the LIVE CHAT link on this page.

FLEXEJ

Q. Do you take credit cards?
A. Yes, please call us with your details. For sales assistance please contact us or use our Live Chat facility.

See also our web shop – secure purchasing with 24hr delivery.

Q. Can I pick what I want from a picture?
A. Yes, scroll down on any of our product pages and you’ll see our comprehensive gallery. Browse this to see examples of what we offer and/or have designed and built for previous customers. For sales assistance please contact us or use our Live Chat facility.
Q. What is the delivery time for metal and rubber expansion joints?
A. For in-stock items, standard items ordered via our web shop we offer 24hr delivery (if order placed by 13.00hrs). Please see our web shop for more details. Other items : typically 7-14 working days. Engineered or special items will be individually quoted. For sales assistance contact us or use our Live Chat facility.
Q. What are your bank details?
A. Bank details for payments in GBP, Euro and USD can be found here. For sales assistance please contact us or use the Live Chat link on this page.
Q. Can I open a credit account?
A. Yes, subject to the normal checks, please download our application form. For sales assistance please contact us or use the Live Chat link on this page.
Q. Are you ISO9001 and ISO14001 accredited?
A. Yes, FlexEJ is accredited to ISO9001:2015 and ISO14001:2015. For sales assistance please contact us or use the Live Chat link on this page.
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.

LOW LOSS HEADERS

Q. Does a Low Loss Header work as an air and dirt separator?
A. Yes, to some extent, as the flow velocity in the body is low. We provide a Flamco AAV and DN25 drain valve on all FlexEJ low loss headers. However, separation is not as efficient as using a dedicated air/dirt separator as the main low velocity section in the LLH is bounded by turbulent cross flows.
Q. Should a horizontal manifold be used to connect to the Low Loss Header?
A. Opinions vary but ideally all the primary circuit and secondary circuit flow and returns should be brought together in horizontal manifolds before connection to the low loss header.
Q. Where do the primary and secondary circuits connect to a Low Loss Header?
A. On a vertical low loss header the returns connect at the bottom and the flows at the top. If the connections are staggered side to side then the lower pair are normally the primary side.
Q. What size Low Loss Header do I need?
A. Sizing can be expressed in terms of flow rate or power. In heating systems, the total boiler power in the primary circuit is often taken as the sizing criteria. The power rating is directly proportional to the flow rate and temperature difference as given by m.Cp.Δt – Power (kW) = Mass flow rate (kg/s) * Specific Heat of Water (kJ/kg°K) * Temperature difference (°K). Our product table above shows both nominal flow rate and power ratings.
Q. Is there a Low Loss Header calculation?
A. We have a calculator set up, please get in touch with the details of your system and we will be pleased to help.
Q. How is a Low Loss Header designed?
A. Based on the flow rate through the low loss header the body is sized to achieve a very low flow velocity – typically less than 0.3m/s. This low velocity ensures a low pressure drop between flow and return.
Q. Is a Hydraulic Separator the same as a Low Loss Header?
A. Yes – strictly speaking hydraulic separation between circuits is achieved using a low loss header.
Q. What is a Low Loss Header?
A. A low loss header (LLH) provides hydraulic separation between multiple pumped circuits. This allows each circuit to operate independently and to be controlled for optimum efficiency. The header presents very low pressure drop bypass between the flow and return. FlexEJ low loss headers are provided with sensor ports on all four branches so whatever control system is being implemented you will have the port you need.
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.

MANUFACTURING

Q. Do you manufacture pressure vessel packages?
A. Yes, we can package the vessel with associated piping, valves, instrumentation and equipment, skid mounted or free standing. To view some examples of our past projects, go to the pressure vessels page and scroll down to the gallery. For technical assistance please contact us or use our Live Chat facility.
Q. Do you design your own pressure vessels?
A. Yes, FlexEJ designs and manufactures engineered pressure vessels to PED, ASME 8, EN13445 and PD5500 as required – plus customer specifications. We can also manufacture to your design and drawing. For technical assistance contact us or use our Live Chat facility.
Q. Are you ISO9001 and ISO14001 accredited?
A. Yes, FlexEJ is accredited to ISO9001:2015 and ISO14001:2015. For sales assistance please contact us or use the Live Chat link on this page.
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. Who can I talk to at FlexEJ?
A. If you have any questions you would like to ask us directly please use LIVE CHAT or call us directly on 01384 881188 or use the CONTACT US form and we’ll get back you asap, usually within 24hrs, sooner if more urgent.

METAL BELLOWS

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.

METAL HOSE

Q. Can metal hose assemblies have liners?
A. Yes, a strip wound hose can be used as a liner within a convoluted metal hose assembly. Flexibility is reduced to some extent. For technical assistance contact us or use our Live Chat facility.
Q. What is a jacketed metal hose assembly?
A. A jacketed hose has a second outer hose over the inner which allows (typically) a cooling or heating medium to be introduced. An example is shown in the gallery : scroll to the bottom on the metal hose page. For technical assistance contact us or use our Live Chat facility.
Q. What is the bend radius for a metal hose assembly?
A. The bend radius depends on the hose diameter and the type of motion. The static bend radius is the minimum radius the hose can bend to for a few movement cycles without fatigue failure. The dynamic bend radius is the minimum radius the hose can bend to for many movement cycles without fatigue failure. ISO10380 defines these parameters. For technical assistance please contact us or use our Live Chat facility.
Q. What is metal hose?
A. Metal hose is manufactured in continuous lengths from metal strip which is welded and then formed. We offer U form convoluted metal hose which is mechanically or hydraulically formed, with standard or close pitch. Typically the hose conforms to ISO ISO10380. For technical assistance please contact us or use our Live Chat facility.
Q. Do you stock metal hose assemblies?
A. No, we only manufacture to order but lead times can be very short. For sales assistance please contact us or use our Live Chat facility.
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.

PRESSURE VESSELS

Q. Do you manufacture pressure vessel packages?
A. Yes, we can package the vessel with associated piping, valves, instrumentation and equipment, skid mounted or free standing. To view some examples of our past projects, go to the pressure vessels page and scroll down to the gallery. For technical assistance please contact us or use our Live Chat facility.
Q. Do you have a standard range of pressure vessels?
A. No, we only manufacture to order. For technical assistance please contact us or use our Live Chat facility.
Q. What size pressure vessels do you manufacture?
A. Typically up to 3m diameter, 10m long, 15t weight. Please let us know your requirements and we can quickly advise if it is within our capability. There are some examples shown in our gallery – take a look by scrolling down to the bottom of the pressure vessels page. For technical assistance please contact us or use our Live Chat facility.
Q. Do you design your own pressure vessels?
A. Yes, FlexEJ designs and manufactures engineered pressure vessels to PED, ASME 8, EN13445 and PD5500 as required – plus customer specifications. We can also manufacture to your design and drawing. For technical assistance contact us or use our Live Chat facility.
Q. Do you hold the ASME U Stamp?
A. No, at present FlexEJ is not U Stamp accredited. For technical assistance please contact us or use our Live Chat facility.
Q. What is PD5500?
A. A. PD5500 is a Specification for unfired, fusion welded pressure vessels. Formerly known as BS5500, it is a UK standard FlexEJ uses to design pressure vessels. For technical assistance contact us or use our Live Chat facility.
Q. Do you stock pressure vessels?
A. No, we only manufacture to order. For sales assistance please contact us or use our Live Chat facility.
Q. What do I need to specify a pressure vessel?
A. To design a pressure vessel we need to know the design pressure, temperature, working fluid, volume (or length & diameter) and what material is required. The number and size of connections to the vessel has a big impact on both the design and cost so this is also useful early design information. For technical assistance please contact us or use the LIVE CHAT link on this page.

RUBBER BELLOWS

Q. Do you hold stock of rubber bellows?
A. Yes. FlexEJ holds a large stock of the most popular sizes and types of Elaflex rubber bellows as well as our HVAC value bellows range. We also 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.
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. How do you install a rubber bellows or a metal bellows?
A. Please refer to our guidelines for installation, anchoring & guides. They are available in the Downloads section of this website: Elaflex Rubber Bellows Installation Instructions and FlexEJ Metal Bellows Installation Instructions. For technical assistance please contact us or use our Live Chat facility.
Q. What lengths of rubber bellows do you offer?
A. FlexEJ Value HVAC and Elaflex rubber bellows are stocked in a number of standard lengths from 105mm to 300mm, a summary of lengths, diameters and types can be found on each product page. We also offer fully engineered rubber bellows which are available in custom lengths to suit the application. You can use our bellows finder to find the most suitable product. For technical assistance please contact us or use our Live Chat facility.
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 rubber bellows for drinking / potable water or with WRAS approval?
A. Yes, our Elaflex ERV-R and ERP rubber bellows have WRAS, DVGW and ACS approval for drinking water. The Safetech manufactured to order rubber bellows can be supplied with WRAS approved EPDM linings. Our MRCA copper ended metal expansion joints also have WRAS approval. For technical assistance please contact us or use the LIVE CHAT link on this page.

SAFETECH

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 rubber bellows for drinking / potable water or with WRAS approval?
A. Yes, our Elaflex ERV-R and ERP rubber bellows have WRAS, DVGW and ACS approval for drinking water. The Safetech manufactured to order rubber bellows can be supplied with WRAS approved EPDM linings. Our MRCA copper ended metal expansion joints also have WRAS approval. For technical assistance please contact us or use the LIVE CHAT link on this page.

TECHNICAL - PIPE EXPANSION

Q. What diameters are metal hose assemblies?
A. DN6 to DN200mm, larger possible. For technical assistance contact us or use our Live Chat facility.
Q. What is a jacketed metal hose assembly?
A. A jacketed hose has a second outer hose over the inner which allows (typically) a cooling or heating medium to be introduced. An example is shown in the gallery : scroll to the bottom on the metal hose page. For technical assistance contact us or use our Live Chat facility.
Q. What end fittings can metal hoses assemblies have?
A. Any standard or custom flange pattern for fixed flange or lap flange. Pipe ends and threaded ends allow virtually any end fitting to be supplied either welded or screwed. Generally it is preferred to have one end that allows rotation at installation to avoid the hose being under torsion. For technical assistance contact us or use our Live Chat facility.
Q. What is temperature deration for a metal hose assembly?
A. As materials get hotter their mechanical properties – strength – tend to decrease. This has to be taken into account when stating a pressure rating for a metal hose; the pressure rating decreases with increasing temperature. For technical assistance contact us or use our Live Chat facility.
Q. What is the best shape for a metal hose assembly to take up?
A. Two movements must be avoided in the installation : torsion and axial movement. Torsion can result from many apparently acceptable hose installations and will reduce the life of the hose considerably. Axial extension for a braided hose assembly is impossible as the braid prevents the hose getting longer. Axial compression is also to be avoided wherever possible. Generally, lateral and loop installations are the most advantageous. Please refer to the Downloads section on our website. For technical assistance please contact us or use our Live Chat facility.
Q. What temperature can a metal hose assembly operate at?
A. Metal hose assemblies can operate with media temperatures from cryogenic to over 550 deg C. For technical assistance contact us or use our Live Chat facility.
Q. What pressure can a metal hose assembly operate at?
A. Metal hose assemblies can operate from full vacuum to over 200 Barg. The actual rating depends on the temperature, material, diameter and braid – we can quickly advise what is possible for your application. For technical assistance contact us or use our Live Chat facility.
Q. What materials is metal hose braid available in?
A. Metal hose braid is available in Stainless Steel 304, 316, Alloy 625, Monel and Hastelloy. For technical assistance contact us or use our Live Chat facility.
Q. What is metal hose braid?
A. Hose braid is a woven wire mesh which encases the metal hose. It adds greatly to the pressure retaining capability of the hose and for very high pressure applications we use a double braid. The braid stops the hose growing in length under pressure and also helps prevent mechanical damage to the convoluted core. For technical assistance please contact us or use our Live Chat facility.
Q. What is PED?
A. PED is the Pressure Equipment Directive which applies to any pressurised equipment used in the EU. FlexEJ is accredited to ISO9001:2008 and complies with the requirements of module(s) D,D1, E1 & H of Annexe III of the Pressure Equipment Directive 97/23/EC and Schedule 4 of the UK Pressure Equipment Regulations 1999 (SI 2001). For technical assistance contact us or use our Live Chat facility.
Q. What flanges are available?
A. All industry standard flanges are available or we can supply any bespoke flange design you require. Our Flange Finder contains details for many common flanges. For technical assistance contact us or use our Live Chat facility.
Q. What are liners?
A. The liner deflects the flow away from the arch or convolution. This results in smoother flow, less abrasion of the bellows and can provide a reduction in bellows material temperature used in conjunction with insulation. For technical assistance please contact us or use our Live Chat facility.
Q. What is spring rate?
A. Spring rate is the reaction force of the bellows when it is moved. It is a different force to pressure thrust – both forces act together on the piping. For technical assistance contact us or use our Live Chat facility.
Q. What is EN14917?
A. EN14917 is a recent EN harmonised standard for metal bellows calculation which is based EJMA. For technical assistance contact us or use our Live Chat facility.
Q. What does bellows ply mean?
A. This is a metal bellows term : ply refers to the number of sheets of metal used in the forming of the bellows, so a 2 ply bellows is made from two sheets of material. A multi ply bellows is generally more flexible that an equivalent single ply bellows. For technical assistance please contact us
Q. What is the difference between a bellows and an expansion joint?
A. In this field, the terminology can be confusing, often with no universally accepted meaning. We tend to use the following definitions but the terms “bellows” and “expansion joint” are typically considered as interchangeable:

> Expansion Joint – an expansion joint is a complete unit with metal bellows or rubber bellows and end fittings, plus, optionally, liner, cover and external hardware. Other terms used : compensator, flexible connector.

> Rubber Bellows – the flexible element within a rubber expansion joint

> Metal Bellows – the flexible element within a metal expansion joint

> Liner – The liner fits within the expansion joint under the metal bellows or rubber bellows to prevent the flowing media directly impinging on the bellows. This this reduces flow disturbance and allows the temperature of the bellows to be controlled in the design.

For technical assistance please contact us or use our Live Chat facility.

Q. What is a pressure balanced bellows or expansion joint?
A. A pressure balanced design uses an additional bellows to provide an equal and opposite reaction force to the pressure thrust. It’s typically used to allow axial movement but not subject the piping system to the pressure thrust force. See the movements and pressure thrust FAQs for definitions. For technical assistance please contact us or use our Live Chat facility.
Q. What is a gimbal bellows or expansion joint?
A. A gimbal is a pressure thrust restraint which allows angular movement in two planes and no axial movement. Gimbals are often used in pairs to create restrained expansion joints for large two plane lateral movements. See the movements and pressure thrust FAQs for definitions. For technical assistance please contact us or use our Live Chat facility.
Q. What is a hinged bellows or hinged expansion joint?
A. A hinge is a pressure thrust restraint which allows angular movement only in one plane and no axial movement. Hinges are often used in pairs to create restrained expansion joints for large single plane lateral movements. See the movements and pressure thrust FAQs for definitions. For technical assistance please contact us or use our Live Chat facility.
Q. What are tie rods or a tied metal or rubber bellows?
A. A tie rod is a simple pressure thrust restraint. It will allow reasonable lateral movement but not axial extension; it can allow axial compression if the pressure thrust is overcome by the piping movement. See the movements and pressure thrust FAQs for definitions. For technical assistance please contact us or use our Live Chat facility.
Q. What is pressure thrust or force?
A. All expansion joints exert a force, pushing the pipe ends apart – pressure thrust – which is proportional to the operating pressure and diameter of the bellows. If the expansion joint is unrestrained the piping system must withstand the force, or, alternatively, the expansion joint may have restraints built in to constrain the pressure thrust force. For instance types, tie rod, hinge or gimbal.

For technical assistance please contact us or use our Live Chat facility.

Q. Should I select a metal bellow or a rubber bellow?
A. Very roughly, above 6 Barg / 130 DegC or above 16 Barg at any temperature a metal expansion joint will be required. For technical assistance please contact us or use our Live Chat facility.
Q. Can you install a bellows in other than its neutral position?
A. Yes, you may pre-set the bellows within its existing movement capability but care must be taken to ensure the resulting movement cycle is acceptable. For technical assistance please contact us or use our Live Chat facility.
Q. Can you join metal expansion joints together?
A. No, it is not recommended to join metal expansion joints together. However, we may be able to manufacture to your exact requirements so please contact us or use our Live Chat facility.
Q. Can you join rubber bellows together?
A. Yes – if correctly guided and anchored – our rubber bellows can be joined together using a mating flange to seal up on. For technical assistance please contact us or use our Live Chat facility.
Q. What does concurrent mean?
A. Concurrent movements are treated in simultaneous combination. For example, if an expansion joint or bellows is specified with concurrent movements of +/- 25mm axial and +/- 25mm lateral, both movements can occur simultaneously and – for a metal expansion joint – the fatigue life will be stated for that case.

If movements are stated as being non-concurrent the expansion joint or bellows is capable of achieving the individual movements but not both simultaneously – or not within the stated fatigue life for a metal expansion joint.

For technical assistance please contact us or use our Live Chat facility.

Q. How much movement can be achieved with expansion joints or bellows?
A. As a rough guide rubber expansion joints allow around +/-25mm axial, +/- 25mm lateral, +/-5 Deg angular of non-concurrent movement per arch.

There is no easy guide for metal bellows; please contact us with your requirements.

Note that large axial movements are often best accommodated by placing a lateral expansion joint at 90 Deg to the main run of pipe.

See our FAQ list for a definition of bellows movements – and concurrent vs non-concurrent.

For technical assistance please contact us or use our Live Chat facility.

Q. What are expansion joints or bellows movements?
A. There are three types of allowable movements:

> Axial movement is the movement of the bellows or expansion joint parallel to the centre line of the expansion joint – compression and extension.

> Lateral movement is the movement of the bellows or expansion joint in a plane perpendicular to the centre line of the expansion joint

> Angular movement is the movement of the bellows or expansion joint causing the centre line of the expansion joint to follow an arc.

Rotation, end to end, is not an allowable movement and will cause the bellows or expansion joint to fail.

For technical assistance please contact us or use our Live Chat facility.

Q. What materials can metal expansion joints be manufactured from?
A. Engineered metal bellows can be manufactured from any high ductility metal. The material selection is normally based on either high temperature strength or corrosion resistance. The most frequently used materials are stainless steel 304 / 321 / 316 , high nickel alloys 625 / 825, titanium and Duplex. The pipe ends for the expansion joint are often manufactured from a less costly material than the bellows – carbon steel or CrMo for example – but frequently Stainless Steel is specified. For technical assistance please contact us or use our Live Chat facility.
Q. Are rubber bellows flameproof?
A. The Elaflex YellowSteel ERV-GS Rubber Bellows and Elaflex YellowSteel ERV-GS HNBR Rubber Bellows are fire resistant for 30 minutes at 800 DegC. Flame protection covers are available to fit to all the Elaflex rubber bellows. For technical assistance please contact us or use our Live Chat facility.
Q. Are metal bellows suitable for use with abrasive media?
A. Yes, but all metal bellows MUST have a heavy-duty internal liner fitted. We can help you with this. Please get in touch : contact us or use our Live Chat facility.
Q. Are rubber bellows suitable for abrasive material?
A. Yes, some rubber materials can be used directly with abrasive material, the Elaflex YellowSteel ERV-GS HNBR Rubber Bellow and Elaflex BlueSpot ERV-BR Rubber Bellow being the most abrasion resistant. For any Elaflex rubber bellows or engineered rubber expansion joints a stainless steel internal liner can be supplied which prevents the abrasive flow from directly impacting the rubber. For technical assistance please contact us or use our Live Chat facility.
Q. What temperature rating do rubber bellows have?
A. The temperature rating depends on the expansion joint material and the expected lifetime of the bellows. Elaflex rubber bellows are typically rated up to 100 DegC (130 DegC for the DIN4809 DoubleRed Rotex type). Engineered rubber expansion joints can be rated up to 180 DegC. For technical assistance please contact us or use our Live Chat facility.
Q. What temperature rating do metal expansion joints have?
A. FlexEJ metal expansion joints for HVAC are rated for between 90 to 300 DegC depending on type. Engineered metal expansion joints can be designed for flowing media temperatures up to 800 DegC and above, the bellows metal temperature is controlled to not normally exceed 400 Deg C by the internal liner and insulation design. For technical assistance please contact us or use our Live Chat facility.
Q. What pressure rating do rubber bellows have?
A. Elaflex rubber bellows are typically rated 16 Barg at 50 DegC up to DN400 decreasing to 6 Barg at 100 DegC for DN1000; please refer to the individual product rating information for each type which can be found in the brochure or click on the Range tab on any rubber bellows page. The pressure rating depends on the material, diameter and design temperature of the bellows; for engineered rubber expansion joints we can normally meet any reasonable requirement. For technical assistance please contact us or use our Live Chat facility.
Q. What pressure rating do metal expansion joints have?
A. FlexEJ metal expansion joints for HVAC are rated: flanged -16 Barg, copper ended MRCA and union ended MRUA – 6 Barg. The pressure rating depends on the material, diameter and design temperature of the bellows. For engineered metal expansion joints we can normally meet any requirement. For technical assistance please contact us or use our Live Chat facility.
Q. What lengths of metal expansion joint do you offer?
A. FlexEJ metal expansion joints for HVAC are stocked in up to 2 standard lengths for each type. Industrial configurable metal expansion joints have a range of length for each size which can be chosen at order. Manufactured to order metal expansion joints can be manufactured to any desired length greater than the minimum length required for the design movements. You can use the bellows finder to find the most suitable product. For technical assistance please contact us or use our Live Chat facility.
Q. How do I know which metal expansion joint to use?
A. You can use our bellows finder to find the most suitable product and our FAQs here give information. For technical assistance please contact us or use our Live Chat facility.
Q. How do I know which rubber bellows to use?
A. You can use our bellows finder to find the most suitable product and our FAQs here give more information. For technical assistance please contact us or use our Live Chat facility.
Q. What certification / approvals do metal expansion joints have?
A. Standard metal expansion joints may have a pressure test certificate issued if requested with order. Engineered metal expansion joints are provided with very extensive certification depending on customer requirements, PED if applicable and industry specifications such as ANSI B31.3. The certification required and applicable specifications must be agreed prior to order placement. For technical assistance please contact us or use our Live Chat facility.
Q. What certification / approvals do rubber bellows have?
A. Our ranges have many approvals and certification. A summary for the Elaflex range of high quality rubber bellows can be found in our catalogue. The individual product data sheets for rubber bellows also show the certification and approvals. We can also provide specific material certification for all items if requested at time of PO. For technical assistance please contact us or use our Live Chat facility.
Q. Can you have different flanges on the same rubber bellows or metal expansion joint?
A. Yes, we can normally accommodate any combination and also different nominal bores. A selection of common flanges are shown in our Flange Finder. For technical assistance please contact us or use use our Live Chat facility.
Q. What is ISO10380?
A. ISO 10380 is the standard to which our metal hose is typically manufactured; it defines the physical properties of the hose, deration with temperature and movement cycles. For technical assistance please contact us or use the Live Chat link on this page.
Q. What certification / approvals do FlexEJ metal hose assemblies have?
A. Full material traceability / PMI, DP examination of all welds (including hose long seam), hydrotest are all typical for engineered metal hose assemblies. The certification required and applicable specifications must be agreed prior to order placement. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. What is B31.3 / Appendix X?
A. B31.3 is the ANSI process piping specification frequently applied to industrial, petrochemical and refinery piping systems. Appendix X contains a version of the EJMA metal bellows calculation which uses a different fatigue curve to EJMA. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. What is EJMA?
A. The EJMA is the Expansion Joints Manufacturers Association. Their bellows calculation method is most frequently used for metal bellows expansion joint design. EJMA does not cover rubber bellows or metal hose design. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. Are rubber bellows suitable for a vacuum?
A. Yes, typically for Elaflex rubber bellows above DN50 a vacuum support ring or spiral is required for FV, the partial vacuum performance varies by type and diameter, please refer to the product data sheets. Support rings or spirals are an option for all standard rubber bellows and may be specified for integration into all our manufactured rubber expansion joints. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. What materials is metal hose available in?
A. Metal hose is available in Stainless Steel 304, 321, 316, Alloy 625, Monel and Hastelloy. It may be possible to meet requirements for other specific grades and materials but this will depend on volume and the suitability of the material to be formed. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. How do you install a metal hose assembly?
A. Please refer to our guidelines for metal hose installation. For technical assistance please contact us or use the LIVE CHAT link on this page.
Q. What is an Elaflex rubber expansion bellow?
A. Elaflex rubber expansion bellows (joints) are high-quality rubber joints used extensively in piping systems in the UK and worldwide to join piping systems, manage pressure and movement within the system caused by changes in pressure, materials or temperatures in the system.

TECHNICAL - PRESSURE VESSELS

Q. What certification / approvals do pressure vessels have?
A. The pressure vessel design code will stipulate the minimum certification and test requirements. These can then be augmented by customer specifications – typically we can meet all these requirements. The certification required and applicable specifications must be agreed prior to order placement. For technical assistance contact us or use our Live Chat facility.
Q. What size pressure vessels do you manufacture?
A. Typically up to 3m diameter, 10m long, 15t weight. Please let us know your requirements and we can quickly advise if it is within our capability. There are some examples shown in our gallery – take a look by scrolling down to the bottom of the pressure vessels page. For technical assistance please contact us or use our Live Chat facility.
Q. Do you hold the ASME U Stamp?
A. No, at present FlexEJ is not U Stamp accredited. For technical assistance please contact us or use our Live Chat facility.
Q. What is ASME 8?
A. ASME BPVC Section VIII – Rules for Construction of Pressure Vessels, is a standard FlexEJ uses to design pressure vessels. For technical assistance contact us or use our Live Chat facility.
Q. What is EN13445?
A. EN13445, Unfired Pressure Vessels, is a standard FlexEJ uses to design pressure vessels. It is harmonised under the
PED. For technical assistance please contact us or use our Live Chat facility.
Q. What is PED?
A. PED is the Pressure Equipment Directive which applies to any pressurised equipment used in the EU. FlexEJ is accredited to ISO9001:2008 and complies with the requirements of module(s) D,D1, E1 & H of Annexe III of the Pressure Equipment Directive 97/23/EC and Schedule 4 of the UK Pressure Equipment Regulations 1999 (SI 2001). For technical assistance contact us or use our Live Chat facility.
Q. What material can pressure vessels be manufactured from?
A. We can work with most weldable high strength metals – typically Carbon Steel, CrMo, Stainless Steel, Titanium, Duplex Stainless Steel. For technical assistance please contact us or use the LIVE CHAT link on this page.

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

 

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They don't bite. And they know what they're talking about. Call the team any time from 9am to 4pm weekdays 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.

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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