Have you ever wondered why you need valve containment boxes on you’re API 650 tank when you already have an internal PVC tank liner, one of the state’s acceptable secondary containment options? First, states that permit internal tank liners require valve containment boxes, so there really is no choice in the matter. Nevertheless, valve containment boxes are worth every penny in protection against a product leak if an above ground tank valve fails.
Talking about containment can be disheartening because it is centered on the undesired situation of part of a tank system failing or leaking. Remember though that such safety mechanisms are planning for an event that has a low probability of occurring. It’s just like having a fire alarm in your home. Most people go their entire life without their fire alarms being needed to indicate a fire. However, when people do experience a fire, that alarm is invaluable to their safety and security. Valve containment boxes provide that same safety and security for your above ground fertilizer tank system.
Here are three facts about valve containment boxes that will help you appreciate the work they do for you.
- Containment is the Name of the Game
The valve box is simply another part of the containment system for a tank system with an internal liner. Understanding how the internal PVC liner containment system works helps clarify the need for the valve containment boxes. Compared to other choices of secondary containment, a PVC liner becomes the primary containment of the product. The product is entirely stored in the PVC liner, so it never touches the tank wall unless there is a breach in the liner or the liner is overfilled. Thus, the above ground storage tank is what acts as the secondary containment.
The liner is connected to the valves of the tank, which are connected to the wall of the tank. These valves are the product’s only way in and out of the tank. The tank will contain the product if the liner has a leak. But if the valve leaked without more protecting it, there would be nothing to contain such a leak going through the valve.
So the valve containment box serves the purpose of containing any product if a valve were to fail. This prevents losing product as well as any environmental contamination.
- Can Handle the Pressure
So why not just put a bucket or small well below each valve to catch any escaping product if a valve leaked? The answer is the head pressure that the liquid product creates in the above ground storage tank. This pressure is always greatest at the bottom of a tank because the liquid at the bottom of the tank is under all of the pressure created by the liquid on top of it.
With the valves being located near the bottom of the tank, that means the head pressure is almost at its highest point. Thus, if a valve leaked, a great deal of pressure, 19 pounds per square inch, would be trying to push the product through any opening. This is why just hanging a bucket on the valve would no chance of containing such a leak. The product would very well create a spray out of the valve leak.
Enter the valve containment box. Valve containment boxes are engineered to withstand the tank head pressure, so that no matter how fast the product is flowing through the failed valve that every last drop of product will be contained within the box. The benefits to you in the rare event of a valve failure is no lost product, thus no lost revenue, and no environmental spill to remedy.
With these benefits, valve containment boxes should be a mechanism that earns your respect in how they protect your bottom line.
- Leak Monitors Present
There are leak monitors on the valve containment box that must be checked each time before the hatch on the containment box is opened. If a valve does fail, the leak monitor will have product in it. Thus, if you open a valve containment box leak monitor and product is present, this tells you that the valve has failed and you should not open the box hatch.
So what should you do if you have product in your box valve containment box leak monitor? The fix is that the valve needs to be replaced. In order to do that, the product in the tank needs to be drained through one of the other operative valves. Then the valve should be replaced to make your tank fully operational again.
So while you are in the processing of choosing a secondary containment method for your above ground tank construction, you can have confidence in the security that valve containment boxes provide you for an internal PVC liner secondary containment system.
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