A Look At Chemical Storage Tank Expansion Joints

Chemical storage tanks expand and contract due to seasonal temperature variations, pressure changes from loading and unloading the contents within the tank, and vibrations from pumps during filling and discharge from the storage tank.

A flexible expansion joint is a special performance-maximizing plumbing component that can be installed on any polyethylene tank to maximize tank performance and longevity. The expansion joint enables safe operation of the storage tank in fluctuating seasonal temperatures and can protect against damage caused by pressure changes. They expand freely during loading and unloading of the tank.

Flexibility of the expansion joint also eliminates damage from piping vibrations caused by pumps or hard piping. Hard piping creates a fulcrum that would damage the fitting or crack the tank, and the expansion joint virtually eliminates that threat.

Two Types of Flexible Expansion Joints

Poly Processing offers two types of expansion joints, the PTFE Expansion Joint and a Flexible Hose Connection.

PTFE Expansion Joint

The PTFE Expansion Joint is a PTFE connector that is designed to protect polyethylene tanks by compensating for misalignment, absorbing expansion and contraction, and isolating vibration and shock.

Below, you’ll find the minimum parameters for connecting an expansion joint on the bottom third of a polyethylene tank.

Flexible Connection Minimum Specifications are below: (For common size fittings and piping systems up to 6”) Contact Poly Processing for information on larger expansion joints.

• Axial Compression ≥ 1.5˝
• Axial Extension ≥ 0.625˝
• Lateral Deflection ≥ 0.750˝
• Angular Deflection ≥ 14°
• Torsional Rotation ≥ 4°

Flexible Hose Connection

Flexible Hose Connections isolate the tank from the stresses and forces associated with pumps and piping. Ultra-high molecular weight hose that makes up these connections offers tremendous chemical resistance.  These connections are good choices for transitioning through secondary containment and are available in 1” - 4” sizes. 

To determine the proper and safe expansion joint fittings for your application, talk to a Poly Processing storage tank expert.