How should the nitrogen pressure in the seal tank be set in the 53A flushing scheme?
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How should the nitrogen pressure in the seal tank be set for the flushing scheme of the centrifugal pump 53A? The requirement is an alarm for low nitrogen pressure, but what should be the appropriate value for this alarm threshold? Please help; the installation needs to start as soon as possible. Thank you.
First, determine the pressure in the sealing chamber; once this pressure is known, the pressure of the sealing fluid can be calculated (it is generally 0.2~0.3 MPa higher than the pressure in the sealing chamber). The sealing fluid comes from a storage tank, which is pressurized by gas. Therefore, it is appropriate to set the switch low-limit value at (seal chamber pressure + 0.05~0.1 MPa)~
How do I calculate the pressure in the sealed chamber? The relative density of the medium is 0.7; its viscosity is 0.6 CST. The flow rate is 20 cubic liters, the head is 100 meters, the inlet pressure is 0.3 kilograms of pressure, and the outlet pressure is 7.2 kilograms of pressure. Thank you.
The manufacturer has responded today: the pressure in the sealing chamber is 0.5 MPA, and the low-pressure alarm threshold is 0.05 MPA. Thank you for the help from *ao*ao1874.
Reply to 4# mantaray’s question: 1. The low-pressure alarm is set at 0.05 MPaA – why is this value so much lower than the pressure in the sealing chamber? Is this still the pressure-sealed Option 53? 2. The pressure in the sealed chamber is 0.5 MPaA – is it that high?
The pressure at the pump inlet is 0.3 kilograms, which is equivalent to 0.03 MPa. The pressure in the sealing chamber should be between 0.1 MPa and 0.2 MPa; it can’t be as high as 0.5 MPa, right? And why is the low-pressure alarm set so low?
For the flow rate and head you mentioned, a regular cantilever pump is used. The pressure in the sealing chamber is approximately equal to the inlet pressure plus the head pressure multiplied by a coefficient; this coefficient ranges from 0.1 to 0.3. If 0.2 is used, the pressure in the sealing chamber is around 0.17 MPa, which is roughly consistent with the calculations. However, if 0.1 is used, the pressure in the sealing chamber is 0.1 MPA. Using 0.05 MPA would be slightly too low, but it’s still reasonable. If the value chosen is too close to the actual pressure in the sealing chamber, fluctuations in the inlet pressure can lead to inaccurate readings. Please ask an expert to review it
Sorry, I didn’t take into account the pressure in the pressure vessel at 53. According to Fox’s approach, the pressure inside the sealed vessel should be 1.5 bar higher than the pressure in the sealing chamber; therefore, the pressure inside the sealed vessel is roughly around 0.25–0.35 MPa. Reporting a value that is 0.05 MPA lower is indeed too low.