Single, Dual or Gas-Barrier Seals: A Decision Framework Based on Hazard Level

A common question when choosing a pipe for a pump is whether to use a single or double pipe.The answer depends mainly on the level of danger of the pipe and the requirements for emissions.

Application to Arrangement 1)

Compatible with non-toxic liquid, not flammable, small leakage is acceptable. Low cost, simple system.

Double reduction without increasing pressure (Arrangement 2)

There are two pads with a buffer liquid in the middle that do not increase pressure. The outer pads do a backup task, suitable when a layer of safety needs to be added but still accepts a small amount of buffer material entering the buffer liquid.

Double reduction of pressure (Arrangement 3)

Blocking fluid has a higher pressure than the plasma, so the plasma does not get out. This is an option for toxic, flammable plasma or requires extremely low emissions, but requires auxiliary systems such as containers and refrigerators.

The gas barrier.

Some fittings use inert gas as a blocking layer instead of a liquid, which is suitable when you want to avoid fluid contamination blocking the process or when the fittings do not allow the fluid to be injected.

Proposal for Decision.

• Non-dangerous leather: single leakage priority.
• Medium hazardous substance leather: double rupture consideration does not increase pressure.
• Toxic or flammable leaves: double pressure lifting priority.

Source of reference.

Summary from the Arrangement concept in API 682 and common technical documentation.