LNG heat exchanger pressure difference issue

An increase in pressure difference may indicate a blockage; check whether the upstream filtering equipment is functioning properly and whether the upstream purification parameters are stable.

On the natural gas side, if the gas supply is stable, an increase in pressure may be caused by the freezing and blockage of heavier components; if the pressure on the refrigerant side increases or decreases, it is possible to check whether the step valve is functioning properly.

We are coke oven gas; the pressure difference of the raw materials is large

Inappropriate temperature control may lead to supercooling, and the mixture of gas and liquid causes fluctuations in pressure differences

In LNG (liquefied natural gas) heat exchangers, a sudden increase or decrease in pressure difference when the air intake volume remains stable is a common operational issue; the reasons behind this are complex and involve multiple factors. The following analysis is provided from the perspectives of a sudden increase and a sudden decrease in pressure difference: Reasons for a sudden increase in pressure difference: Fluctuations in fluid flow rate: Even if the overall air intake volume appears stable, there may be local fluctuations in flow rate. For example, gases may be mixed in LNG, and the gas-liquid flow pattern inside the heat exchanger changes; the presence of these gases reduces the effective flow area through the heat exchanger, resulting in an increase in flow velocity and thus a rise in pressure difference. Scaling or blockage: Certain impurities and moisture present in LNG can, over time as the heat exchanger operates, gradually form deposits on the inner walls of the heat exchange tubes or on the plates. These deposits narrow the flow channels, increasing the resistance to fluid flow and thus leading to an increase in pressure difference. Furthermore, if the filter screen of the heat exchanger is damaged or not cleaned in a timely manner, larger particles of impurities can enter the heat exchanger, causing local blockages that hinder the flow of fluid and increase the pressure difference. Damage to the internal structure of the heat exchanger: Prolonged operation or exposure to abnormal shocks can cause issues such as cracks in the heat exchange tubes inside the heat exchanger and deformation of the plates. When the heat exchange tube ruptures, the fluids in adjacent tube banks may mix with each other, altering the normal flow path, increasing flow resistance, and causing an increase in pressure difference. Deformation of the plates causes uneven spacing between them, which hinders fluid flow and leads to an increase in local pressure differences. Temperature changes: Abnormal changes in LNG temperature can affect physical properties such as its density and viscosity. If the inlet temperature drops suddenly, the density of LNG increases, and its viscosity may also increase, which raises the flow resistance of the fluid within the heat exchanger and thus leads to an increase in pressure difference. Valve failure: Abnormal conditions of the inlet and outlet valves of the heat exchanger can also affect the pressure difference. For example, if the opening degree of the valve suddenly decreases, the resistance to fluid flow through the valve increases, resulting in an elevated pressure difference between the inlet and outlet of the heat exchanger. Or issues such as sticking inside the valve or damage to the valve core can also affect the normal flow of the fluid, leading to fluctuations in pressure difference. Reasons for the sudden decrease in pressure difference: Changes in fluid properties: Contrary to the effect of temperature on properties when the pressure difference increases, if the temperature of LNG rises suddenly, its density decreases and its viscosity drops; as a result, the flow resistance of the fluid within the heat exchanger also decreases, leading to a reduction in the pressure difference. Furthermore, changes in the proportion of certain components in LNG can also cause changes in its physical properties, thereby affecting the pressure difference. Leakage issue: Leaks inside or outside the heat exchanger can both lead to a decrease in pressure difference. Internal leaks, such as perforations in the heat exchange tubes or failures in the gasket seals, can cause the fluid on the high-pressure side to leak to the low-pressure side, resulting in a decrease in the pressure difference between the inlet and outlet. External leakage causes some of the fluid to leak directly into the outside environment, resulting in a decrease in flow rate within the system and a drop in pressure, which in turn reduces the pressure difference across the heat exchanger. Abnormal opening of the valve: If the bypass valve of the heat exchanger opens accidentally, some of the fluid flows directly through the bypass instead of passing through the normal heat exchange channels of the heat exchanger. As a result, the actual flow rate through the heat exchanger decreases, the resistance drops, and the pressure difference also decreases. Or, if the inlet or outlet valves fail and open suddenly, this too can lead to a reduction in fluid flow resistance and a decrease in pressure difference. Instrument failure: Malfunctions in the differential pressure measuring instrument itself, such as faulty sensors or errors in signal transmission, can lead to inaccurate differential pressure readings, resulting in an apparent sudden decrease. In this case, the actual heat exchanger pressure difference may not have changed, and it is necessary to inspect and calibrate the measuring instruments.