Technical Information - the professional expansion joint manufacturer in China

Home|Sitemap|Customers|Industries & Applications

1, What is an expansion joint ?

An expansion joint is a device that contains one or more bellows, which is used to assist with structural changes, such as those produced by the thermal expansion or tightening of a pipe, tube, or vessel. It can be used to allow movement in a pipeline system. The bellows is a flexible part of an expansion joint that normally consists of several folds. The expansion joint is the best solution when making a piping system more elastic. Flexibility is needed when there are different movements in a pipeline such as, frequent vibrations, pulsations and thermal growth.

2,Movements- What kind of movements can an expansion joint absorb?

There are three basic types of movement that can be applied to the bellows and these are: Axial,Lateral and Angular as illustrated below.

Axial Movement is either the stretching or flattening of the expansion joint along its length

Lateral Movement is a movement of the two ends of the joint where those ends stay parallel to each other

Angular Movement is simply the curving round of the joint along its axis.

The one type of movement they cannot deal with, however, is torsion, namely twisting along the piece's length. This is best avoided by keeping the joint fastened in place by external attachments, and taking care with the fastening when attaching it in the first place.

3,Accessories- How can I upgrade my expansion joint to handle different conditions?

Ties rods : attach to an Expansion Joint assembly to mitigate pressure loads, as well as ancillary forces such as dead weight.

Limit rods : a "fail-safe" addition which addresses the situation of occasional anchor overload or system malfunction which could cause bellows expansion beyond tolerance.

Liners : internal sleeves used to protect the internal surface of the metal bellows from media which may compromise its integrity.

Purge Connections : used in tandem with Liners, keep the bellows within high temperature tolerance conditions, such as oil industry applications.

Covers : are used to protect the Metal Bellows Expansion Joints from any detrimental external elements.

Main Anchors : resist the effects of all forces acting upon them, including pressure thrust, bellows spring resistance, frictional resistance of pipe guides, and inertial forces at bends and elbows.

Intermediate Anchors : used to divide a long pipe run into shorter individual expanding sections.

Directional Anchors : permit movement in one direction only.

Pipe Alignment Guides : control thermal expansion in the system so that the movement applied to the bellows assembly is axial only.

4,Testing and Quality Control

Testing:

CTA Company is a company who dedicated to provide our customers with quality products and services. Our products are inspected and evaluated extensively through each stage of our production .CTA Company is able to perform types of non-destructive testing such as fatigue life test, spring rate test, radiography, sulfur hexafluoride test, helium leak detection, penetrant testing and air tight test.

Quality Control:

The design, quality assurance, and manufacturing practices at CTA Company are in compliance with the following codes and standards: EJMA, KR, CCS, LIoyd’s Register and ISO9001:2000.

Quality is not just a word, but a passion at CTA Company, we regard the quality as the life of our company. All the designs of our expansion joints are as per the latest EJMA standards. CTA Company engineers use innovative design technology such as Finite Element Analysis (F.E.A.) and 3D Modeling software to analyze the performance of the bellows element and supporting hardware and inspection through all the stage of our production to ensure the quality of our products from the beginning to the delivery.

5,Delivery and Installation

Delivery:

An extensive material stocking program enable CTA Company employees provide the exceptional service our customers deserve. If custom-built expansion joints, shipping is handled on an individual basis. CTA Company can be responsible for shipping and send all the documents to you or you can use your own preferred carrier. CTA Company is committed to quick, on-time delivery of your expansion joints and looks forward to serving all your delivery needs.

Installation :

1. The bellows element shall be protected from damage such as dents, arc strikes, weld spatter, and other damage can cause the joint to fail. ALWAYS protect the bellows element from burn splatter with a flame-retardant cloth or other shielding material. Damage joints should not be used.

2. Align joint flange and pipe flange holes. Do not try to compensate for flange (vanstone flanges permit some rotational misalignment) or pipe misalignment by putting any torsional, compressive, extension, or offset loads on the expansion joints. If a bellows is subjected to torsional forces due to hole misalignment, it will reduced cycle life and/or bellows failure can occur. Good practice suggests that a mating flange in the piping system remain unwelded until the expansion joint has been bolted in position.

3. All anchors, guides, and supports must be installed according to engineering drawing and specifications.

4. When expansion joints are fitted with liners or internal sleeves, the unit is marked with an arrow indicating the direction of flow. They are to be installed in the proper orientation with respect to direction of flow.

5. Unit lengths must not be altered during installation except for the application of cold pull.

6. Remove shipping restraints after installation, but before hydrotesting.

7. If testing medium is significantly heavier than the product to be carried in the system, care must be taken to support the additional weight.

8. Paints containing low melting point metals or other compounds, particularly aluminum lead or zinc, must not be allowed to come into contact with the bellows convolutions.

9. All installation procedures should conform to E.J.M.A Safety Recommendations in Section B.

10. Expansion joints must be easily accessible to allow for period inspection. Bellows should be inspected for any signs of damage such as dents or scores. Damaged expansion joints should be replaced immediately.

11. Final System Check - After installation has been completed and shipping bars removed, check all anchors, guides, and pipe supports. Slowly apply test pressure to the system, checking for any unusual movement of the bellows anchors or guides. If movement is observed, immediately lower the pressure and re-examine the system for damage.

Note : Test pressure should not exceed 1-1/2 times design pressure.