Steel Drums 101
Many plants use steel drums in their processes. The way they are used is as varied as the thousands of types of manufacturing plants they are found in. Some of the most common uses are bulk storage/transport of chemicals and waste collection (liquid or solid). The liquids and chemicals they come in contact with are varied and the jobs they do change with your plant’s needs, so different kinds of drums are needed to match your application. But how do you know which one you need?
Most drums are made of either carbon steel or stainless steel. Stainless steel offers better chemical resistance than carbon steel. So, if your plant uses aggressive chemicals or if there is a wide range of liquids the drum may come in contact with, a stainless steel drum will be more versatile and handle more jobs. The drums can also be lined for added corrosion resistance.
The thickness of the metal is important depending on the reason you’re using a drum. Thicker drums are recommended for shipping hazardous liquids, as they’re stronger than thinner drums. Plus, the thicker the drum, the more weight and pressure it can handle. Most drums show something like this – 1.5/1.2/1.2 mm – when describing the thickness of the drum, but what does that mean? This shows the thickness of the different parts of the drum – lid/body/base. In the above example, that would mean that the lid is 1.5 mm thick, the body is 1.2 mm thick and the base is 1.2 mm thick. Most drums fall in the range of 0.9 – 1.5 mm thick.
Open or Closed Head
Drums are either open head (lid can be removed) or tight/closed head (lid is permanently secured). Open-head drums are typically used in situations where frequent addition or extraction of the contents occurs. Open-head drums make it easier to work with solids and thicker liquids (soils, absorbents, syrups, glues, oils, etc.) while tight-head drums are typically used with lower viscosity liquids.
The lid on an open-head drum is typically attached with a nut and bolt ring, which can be tightened to a particular torque to meet UN Rating requirements. You can also use quick-opening lever lock rings for easy access and closure, eliminating the need to use tools every time you want to remove the lid. New Pig has developed a unique latching lid system that enables users to open and close an open-head drum with one hand and no tools. The latching lid system is the most convenient, easiest way to access your drum.
If you intend to use funnels to add liquids to your drum, or if you intend to add pump fittings for pumping liquids out of your drum directly into one of your processes, you will need to know what type of bung (top opening) is on the lid. A tight/closed-head drum would typically have 2 bungs, one 2” and one ¾” in diameter. The threads on the bungs are almost always NPT (National Pipe Taper), but occasionally could be Buttress type instead. NPT threads are a fine thread and Buttress threads are a coarse thread. They also have different head styles, which may require a specialized tool for tightening.
Unlike straight pipe threading that is used to join two pieces of pipe together, NPT-threaded fittings will pull tight to make a liquid-tight seal. Most steel drums have NPT-threaded bung openings and caps. Buttress threads are also designed to form a liquid-tight seal, but are larger and coarser than NPT threads. Buttress threads are also known as “saw threads” and are designed to handle high stress, such as tightening a funnel into the bung opening. Typically, Buttress-threaded openings and caps are found on plastic drums rather than steel.