When you’re filling your chemical storage tank, it is important to ensure the safety of employees and equipment and to prevent loss of product. A fill line helps prevent spills while making it easy and efficient to fill the tank.
A fill line is a specially designed pipe system that is attached to the tank, the majority are composed of PVC or CPVC to ensure chemical compatibility. It normally comes with a ball valve and a quick disconnect camlock system to keep the line from transferring chemical when not in use. Fill lines are available in several configurations, including internal, external and combination. An anti-foam elbow is another option that can be used as a substitution for an internal fill line.
Let’s take a look at the different types of fill lines and their benefits, and how to prevent foaming.
Internal Fill Lines
Internal fill lines are supported inside your polyethylene tank and have a fitting at the top of the tank—typically a universal ball dome style fitting. The pipe itself is attached to the fitting with a coupling, and the pipe extends almost to the bottom of the tank. The standard length is two inches from the tank’s bottom, although this can be adjusted according to your needs.
Because the internal fill line reaches to the bottom of the tank, it reduces or even eliminates splashing and foaming. You can also use the pipe to drain the tank, eliminating the need for a lower sidewall fitting.
In certain circumstances, an internal fill line can create internal tank pressure during a fill. Dense fluids increase the possibility of hydraulic hammering, which occurs if pneumatic air pressure pushes air bubbles to the bottom of the tank which already has several feet of head pressure from a partially filled tank.
You can avoid hydraulic hammering by using an anti-foam elbow. The anti-foam elbow is a small elbow assembly that attaches to the top of the tank for filling. It comes down vertically and forms a 45-degree angle toward the sidewall of the tank. The fluid is poured into the tank along the sidewall, similar to pouring a carbonated beverage down the side of a glass.
This reduces foaming and prevents hydraulic hammering, because air bubbles can escape at the mouth of the elbow, without being trapped below the surface of the fluid.
The anti-foam elbow is a more cost-effective option because it is a small, singular assembly.
External Fill Lines
Exterior fill lines are attached to the outside of the chemical tank sidewall and connect to the top of the tank with a fitting—typically, a universal ball dome style fitting. An external pipe support braces the pipe to provide stability.
The beginning of the external fill line is fitted with a camlock system so that trucks can connect their hoses easily. The line can also be connected to additional pipes, allowing you to extend the tank system from indoors to an outdoor area, or across a warehouse for easier access to the tank.
Combination Fill Lines
A combination fill line marries the internal and external fill lines, giving you the best of both worlds. Combination fill lines provide easy connections to the polyethylene tank with an external line while reducing foaming and splashing during the fill.
In a combination fill line, a drop pipe extends into the tank almost to the tank bottom. This line is connected to a fitting at the top of the tank, which is coupled to the external pipe. The combination fill line is supported inside and outside of the tank for maximum safety and stability.
The best fill line for your needs depends on your chemical application and the configuration and placement of your tank system. Whether you choose to install an internal, external or combination fill line, it will need to be properly anchored to the tank. A properly designed support ensures that the line is durable and stable if a truck or piece of equipment inadvertently bumps the line.