A bullet tank is the long, horizontal, rounded-end pressure vessel used to store liquefied gases like propane and other NGLs under pressure. Its shape - which gives it the name - is what lets it hold those products as a liquid at ambient temperature. This guide explains what a bullet tank is, why it is a pressure vessel, how it compares to other storage, and how it is monitored.
Bullet Tank in one line: A bullet tank is a horizontal cylindrical pressure vessel with rounded (usually hemispherical or elliptical) ends, used to store liquefied petroleum gas (LPG), propane, butane, and other natural gas liquids under pressure at ambient temperature. Its shape resembles a bullet, hence the name.
Products like propane and butane are gases at atmospheric pressure and ambient temperature - you cannot store them usefully in an open, atmospheric tank because they would simply boil off. To keep them as a compact liquid, you hold them under pressure: a bullet tank keeps propane liquefied at the vapor pressure of the product (well above atmospheric). That makes a bullet tank a true pressure vessel, designed and code-stamped to ASME Section VIII, with thick rounded heads that handle internal pressure far better than the flat components of an atmospheric tank.
The rounded, horizontal cylinder shape is efficient at containing pressure and easy to fabricate, ship, and set on saddles, which is why bullets are the standard for small-to-medium pressurized liquid storage.
Compared with an atmospheric stock tank, a bullet is a fundamentally different animal: pressurized rather than vented, horizontal rather than vertical, and built to a pressure-vessel code with relief valves rather than breather vents. Compared with a storage sphere (a spherical pressure vessel), a bullet is used for smaller volumes; spheres (sometimes called Hortonspheres) are chosen for very large pressurized storage where a sphere's geometry is more efficient.
For the largest LPG storage, refrigerated (low-temperature, near-atmospheric) tanks are used instead, but for the typical field, plant, and distribution volumes of NGLs and LPG, the pressurized bullet is the workhorse.
Bullet tanks show up wherever NGLs or LPG are produced, processed, or distributed: gas plant NGL storage, fractionation facilities, propane distribution terminals, and even large end-user sites. Because they hold flammable product under pressure, they carry relief valves, and installations follow safe spacing, fire protection, and code requirements.
The operational values that matter are level (how much liquid, often read as a percentage of a pressurized tank's capacity), pressure, and temperature, since all three interact for a liquefied gas. Field transmitters feed an RTU, flow computer, or PLC, and a cloud SCADA such as Merobix reads those tags over Modbus, DNP3, or OPC UA, so bullet-tank inventory, pressure, and high-level or high-pressure alarms are visible remotely across a plant or terminal.
A bullet tank is a horizontal cylindrical pressure vessel with rounded ends used to store liquefied gases like propane, butane, and other NGLs under pressure at ambient temperature. Its bullet-like shape efficiently contains the internal pressure needed to keep those products liquid.
Propane and butane are gases at atmospheric pressure, so an open atmospheric tank cannot hold them as liquid - they would boil off. A bullet tank keeps them liquefied under pressure, which requires a code-stamped pressure vessel with strong rounded heads and relief valves rather than a vented storage tank.
Both are pressure vessels for liquefied gases, but a bullet is a horizontal cylinder used for smaller-to-medium volumes, while a sphere is used for very large volumes where the spherical shape contains pressure most efficiently for the amount of steel. Bullets are far more common at field and distribution scale.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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