Cryogenic liquids include liquid hydrocarbons such as ethylene, liquefied petroleum gas (LPG), liquefied natural gas (LNG), liquid oxygen, and liquid nitrogen. These substances are typically stored and transported at temperatures ranging from -30°C to -196°C. Pumps used for handling these media are known as cryogenic pumps or magnetically driven pumps. Today’s latest order updates are available for free! Don’t miss out on the newest buyer information—grab it now!
First, let's take a closer look at the key characteristics of cryogenic pumps:
1. **High Inlet Pressure**
Liquefied gases are usually in a gaseous state at ambient temperature and pressure. They only become liquid under specific conditions of low temperature and high pressure. For example, methane is liquefied at around 3 MPa and -100°C, while ethylene requires about 2 MPa and -30°C. This means that the pump must operate with a relatively high inlet pressure to maintain the liquid state.
2. **Sensitivity to Temperature Changes**
The vapor pressure of cryogenic liquids changes significantly with temperature. These liquids are often delivered in a saturated or slightly subcooled state. A small temperature fluctuation can lead to a dramatic change in vapor pressure—sometimes as much as 100% to 200% when the temperature varies by just ±25%. Alongside this, physical properties like density, specific heat capacity, and latent heat of vaporization also vary. As temperature increases, vapor pressure rises rapidly, density drops, and the latent heat of vaporization decreases, making the liquid more prone to evaporation. This can increase the inlet pressure, affecting the pump's structural integrity. Meanwhile, a drop in tank pressure may cause the liquid to absorb heat from the environment, leading to reduced NPSH (Net Positive Suction Head) and poor cavitation performance. Therefore, the suction pipe must be fully insulated to prevent temperature fluctuations, and unnecessary throttling devices such as valves, filters, or orifice plates should be avoided to prevent local pressure drops and vaporization.
3. **Strict Sealing Requirements**
Most cryogenic fluids are highly corrosive and hazardous. Any leakage can pose serious safety risks. Additionally, the latent heat of vaporization of these liquids can cause ice formation around the sealing areas, which further complicates the sealing process. As a result, cryogenic pumps require extremely reliable and tight seals to ensure safe and efficient operation.
In summary, cryogenic pumps are specialized equipment designed to handle extreme temperature and pressure conditions. Their design and operation demand careful consideration of thermal effects, material selection, and sealing technology to ensure long-term reliability and safety.
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