A method of measuring a minimum pressure for gas bubble generation (MPGBG) value of a capillary tube is disclosed. The capillary tube has an inlet and an output portion including an outlet. The inlet is connected to a regulated pneumatic system, configured to supply a gas to the inlet under pressure. The output portion is immersed in a liquid. The gas is supplied to the inlet under a range of pressures including a higher pressure range and a lower pressure range. In the higher pressure range, gas bubbles are generated in the liquid from the outlet. In the lower pressure range, no gas bubbles are generated in the liquid from the outlet. A value of the minimum pressure for gas bubble generation (MPGBG) for the liquid is determined.

Other methods include a method of measuring and storing MPGBG values of capillary tubes, methods of selecting at least one capillary tube from a plurality of capillary tubes, and a method of cutting a capillary tube to a desired MPGBG value.

In a method for measuring the vapor pressure of liquid and solid substances, in which a sample of the substance is arranged in a variable volume of a measuring cell, the measuring cell is gas-tightly closed. The volume of the measuring cell is increased until reaching a measuring volume, and at least one first value of the gas pressure prevailing after the increase in volume is measured. The volume of the measuring cell is additionally reduced until reaching the measuring volume, and at least one second value of the gas pressure prevailing after the reduction of the volume is measured. The vapor pressure is calculated from the at least one first and at least one second measured values.

In a method for measuring the vapor pressure of liquid and solid substances, in which a sample of the substance is arranged in a variable volume of a measuring cell, the measuring cell is gas-tightly closed. The volume of the measuring cell is increased until reaching a measuring volume, and at least one first value of the gas pressure prevailing after the increase in volume is measured. The volume of the measuring cell is additionally reduced until reaching the measuring volume, and at least one second value of the gas pressure prevailing after the reduction of the volume is measured. The vapor pressure is calculated from the at least one first and at least one second measured values.

In a nitrogen generator, multiple, concurrent gas pressure monitors constantly and simultaneously monitor gas pressures at key points in the nitrogen generation process, and a controller generates an alarm when the pressure at any point falls below a respective predetermined pressure level, and remains there for longer than a respective predetermined duration. In some embodiments, a run time of the nitrogen separation unit is additionally monitored. Additionally, in some embodiments, if the output pressure of nitrogen gas falls below a predetermined pressure level, a bypass route is activated to route compressed air directly to the output, thus sacrificing nitrogen gas purity but maintaining required minimum pressure for downstream systems.

In a nitrogen generator, multiple, concurrent gas pressure monitors constantly and simultaneously monitor gas pressures at key points in the nitrogen generation process, and a controller generates an alarm when the pressure at any point falls below a respective predetermined pressure level, and remains there for longer than a respective predetermined duration. In some embodiments, a run time of the nitrogen separation unit is additionally monitored. Additionally, in some embodiments, if the output pressure of nitrogen gas falls below a predetermined pressure level, a bypass route is activated to route compressed air directly to the output, thus sacrificing nitrogen gas purity but maintaining required minimum pressure for downstream systems.

An apparatus for measuring the vapour pressure of a liquid hydrocarbon sample is disclosed. The apparatus comprises a sealed chamber (25) for receiving the sample. The chamber (25) is at least partially defined by a moveable element (26) such that moving the moveable element (26) alters the volume of the chamber (25). The apparatus comprises a displacement sensor (29) configured to measure a displacement of the movable element (26).

An apparatus for measuring the vapour pressure of a liquid hydrocarbon sample is disclosed. The apparatus comprises a sealed chamber (25) for receiving the sample. The chamber (25) is at least partially defined by a moveable element (26) such that moving the moveable element (26) alters the volume of the chamber (25). The apparatus comprises a displacement sensor (29) configured to measure a displacement of the movable element (26).

Determining the thermodynamic state of fuel includes opening the venting connection to release the tank pressure while monitoring the derivative pressure (dP/dt), closing the venting connection when one of the following conditions is met, the derivative pressure (dP/dt) is lower than a predetermined threshold DP1 or the opening time t1 reaches a predetermined value, if the closing of the venting connection occurs when the opening time t1 reaches the said predetermined value, determining that the fuel is boiling and aborting the method if the closing of the venting connection occurs when the derivative pressure (dP/dt) is lower than the said threshold DP1, measuring an initial tank pressure at the closing of the venting connection, measuring the final tank pressure after a closure time t2, calculating the pressure variation (P/t2), comparing the pressure variation (P/t2) with a first threshold PV1, if the pressure is lower then aborting the method.

Determining the thermodynamic state of fuel includes opening the venting connection to release the tank pressure while monitoring the derivative pressure (dP/dt), closing the venting connection when one of the following conditions is met, the derivative pressure (dP/dt) is lower than a predetermined threshold DP1 or the opening time t1 reaches a predetermined value, if the closing of the venting connection occurs when the opening time t1 reaches the said predetermined value, determining that the fuel is boiling and aborting the method if the closing of the venting connection occurs when the derivative pressure (dP/dt) is lower than the said threshold DP1, measuring an initial tank pressure at the closing of the venting connection, measuring the final tank pressure after a closure time t2, calculating the pressure variation (P/t2), comparing the pressure variation (P/t2) with a first threshold PV1, if the pressure is lower then aborting the method.

A method of inspecting a degree of air bubbles which are mixed into an ultraviolet curable resin for an optical fiber having viscosity of 1.2 Pa.Math.s to 6.2 Pa.Math.s at a temperature of 255 C., is performed in such a manner that the ultraviolet curable resin for an optical fiber which is an inspecting target is put into a sealed apparatus, then the inside of the sealed apparatus is decompressed to be a predetermined pressure, and then the sealed apparatus is left to stand as it is for a predetermined time. If a ratio of the volume expansion of the ultraviolet curable resin for an optical fiber is equal to or less than a predetermined threshold, the ultraviolet curable resin for an optical fiber is recognized as an accepted product.