Two of the most important factors in the design of any chemical tank storage system are the way the system is vented and whether or not the system requires flexible connections. Proper venting ensures correct atmospheric-only pressurization of the tank, which can prolong the life of the tank. The placement of appropriate flexible connectors will not only help ensure a tank’s longevity, but can also protect the tank from hinge points that can cause dangerous leaks.
Let’s take a closer look at flexible connections, specifically how they should and should not be used and installed.
One of the biggest advantages of polyethylene chemical storage tanks is that they expand and contract with the pressure changes they experience during loading and unloading of chemical and even weather variations. Whereas a rigid tank is more susceptible to cracking and damage over time, a more flexible tank not only keeps your chemical safer, but it also gives you peace of mind and saves money in the long run, because of its resiliency. It’s important to note, however, that a polyethylene storage tank is only as good as the fittings and accessories you pair it with. Flexible expansion joints allow the tank to move as it must while avoiding the damage that can arise from using hard piping.
For many years, an industry standard was hard piping that came directly into the side of the tank. In a polyethylene tank, hard piping can create damage to the tank in a number of ways:
- Piping vibration from pumps
- Fulcrums that crack the tank
- Hinge points that stress the tank
All of these situations can be avoided by using flexible connections, but there are do’s and don’ts regarding the use of flexible hoses and expansion joints that will help prolong the life of your chemical storage tank.
Flexible Connectors – The Do’s
There are a few best practices for flexible connections that are important to note:
Understand the types of flexible connectors available – Flexible hose connections are resilient, flexible connectors that meet many needs. They can be 3-4 feet long and bend freely to allow the tank to move. There isn’t much concern needed when using a flexible hose because it is so flexible, but it may be considered a tripping hazard in some setups.
Expansion joints are in-line flexible connectors designed to accommodate the tank’s expansion and contraction, absorb damaging shock and vibration, and compensate for misalignment in the piping it feeds. They are inline, and very compact – only about 6 inches long, and can fit in very tight areas.
Use a flex that meets the spec of tank movement needs – Specify that the flex will be provided by the tank manufacturer or call out the specific parameters needed in terms of axial, lateral and differential movement in units of minimal and maximum distance. Some flex joints are intended for other purposes such as misaligned pipe and may not satisfy the tank manufacturers needs. By calling out exact parameters such as travel distance and spring rates, a contractor or installer will not accidentally use a flex that is insufficient for the job.
Understand the space requirement of your tank system – Because flexible hose connections are longer than expansion joints, if you have limited space it’s likely that you’ll need an expansion joint.
Read the installation manual – be mindful of the warnings and techniques called for. Several proper and improper illustrations are provided.
Flexible Connectors – The Don’ts
For a flexible connector to serve its purpose, it has to be installed correctly and supported properly.
Don’t install flexible connectors in the wrong spot – flexible connectors only need to be installed on the lower third of the tank sidewall, since this is the section of the tank that moves the most.
Don’t fail to correctly support the flexible connector – when using a flexible connection, it is important for it to be supported properly but the support cannot restrict the horizontal plane movement of the tank. If a hose is used, it must have a bend since hose will not flex in a linear outward movement along a straight position. When using an expansion joint, the pipe support should be placed after the flex to allow the tank to move slightly outward when filled. If the pipe support bracket is placed before the expansion joint, it negates the flex and prohibits the tank from expanding and contracting, which leads to cracks in the tank or piping.
Don’t use flexible connectors to fix a pipe misalignment – Using a flexible connector to correct piping misalignments can damage the joint and restrict the flexible connector’s ability to move with the tank’s expansion and contraction- its intended purpose.
Flexible connectors are one of the primary keys to a fully functioning, safe and effective chemical tank storage system that will perform well and last the desired life.