Wednesday, July 27, 2016

How to Handle Expansion Joints in Piping Systems

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Expansion joints are of great use in the Philippines especially in piping systems. According to Pumps and Systems, expansion joints or bellows can “absorb all directional movements, reduce noise and vibration, resist shock, relieve pipe and anchor stresses, compensate for misalignment and provide access to piping and equipment.” Aside from piping systems, it can be seen in buildings, bridges and roads.

There are also types of expansion joints, and these are free type, guide rod type, reinforced type, universal type, hinge type, gimbal type, straight pipe pressure balanced type, and bent pipe pressure balanced type. It allows pipes to be flexible due to movement and thermal expansion. It should be able to adjust to axial movement, lateral deflection, angular rotation, torsional rotation and pressure thrust.

But for expansion joints to last, proper care and maintenance should be enforced. Ramachandran explained how to do this in his paper entitled “Metal Expansion Joints/Bellows.”

Bellows should be properly stored. The area should be dry and clean and free of work traffic. Keep it away from weld spatter, molten metal, and heavy and sharp objects. The primary ‘enemy’ of metal expansion joint is corrosion. Cover it with water resistant sheets and place it in an enclosed space. The protective coating in the packing should be intact and don’t stack it above another.

Several things must be kept in mind in order to retain the original shape of the bellow. The shipping brackets with yellow coating should remain in place. The surface or ground is smooth and flat. But don’t let it touch the ground directly or on bare earth; rest it on a weld end pipe or flange.

Treat bellows with utmost care during installation. Conduct a thorough inspection before installing the expansion joints. It should not have damages like broken hardware, loose shipping bars, dents and scratches. Check also the accessories or components of the bellow such as gaskets, fasteners and removable liners.

Mind also how the expansion joints are lifted and handled. Pick it up using the lifting lugs, and avoid using chains or any other handling devices. Do not use the shipping bars because this is not designed as handle bars of the expansion joints. In addition, do not lift an unrestrained bellow.

The shipping bars must remain in position and only remove it after installation is complete. In cleaning bellows, avoid using cleaning chemicals containing chlorides, caustics or sulphides. These substances may corrode the expansion joints. If the bellow needs to be insulated, apply it with chloride free insulation material. It is not just chemicals that may harm bellows. Avoid abrasive tools such as wire brush and steel wool.

Assign a construction personnel who is well-trained and knowledgeable in installing expansion joints. One of his basic tasks is to ensure the piping fits the bellows. The personnel should inspect if the system drawings are strictly followed. After installation, make sure any damage had not been made; no expansion joint is misaligned; the shipping bars are removed and ensure it is free of foreign materials. A pressure test should also be performed.

Expansion joints in the Philippines are not just simple commodity based on the preparations that should be done before and after installation, and even on how it should be stored. Every unit should be handled with care or it will lead to irreparable damage.

An article by: GCK 


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