Seeking help with liquid level measurement in ammonia spherical tanks
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The company has an ammonia spherical tank, whose level is measured using an Emerson 3051S ERS transmitter. Initially, it was estimated that about 40% of the tank would be filled with ammonia, after which no more ammonia was added to the tank, and it has remained in standby mode. But recently, around 8:30 every morning, the liquid level in that tank rises automatically, reaching over 60% by noon and remaining at that level until 5:00 in the afternoon; after that it starts to drop, falling to around 40% by around 2:00 in the early morning, and this happens every day! ! ! I wonder if the experts in this forum have encountered such a situation before? I hope some experts can provide an answer! ! ! ! !
It seems to be related to the ambient temperature.
At first, I thought the same way, so I insulated both the main and auxiliary transmitters on site to rule out the impact of temperature differences between them. After studying their structure and measurement principles in detail, it’s unlikely; though if it were possible! So how do we solve it then
Insulation does not maintain a constant temperature either; it changes along with the external temperature. Insulation only delays this change.
Check the status of the positive pressure valve and whether the pressure lead piping is blocked.
Periodic changes are likely related to the environment; it’s hard to say exactly though
To explain this in terms of the working principle of the level measurement device in this tank, pressure-based methods are currently used for level measurement. In an ammonia tank, the liquid ammonia vaporizes as the temperature rises, which leads to an increase in pressure and thus an elevation in the liquid level. At night, as the temperature drops, the vaporized ammonia returns to a liquid state, the pressure decreases, and consequently the liquid level drops as well.
There is no issue with the measurement by this level gauge. No material enters or exits this spherical tank; in other words, the mass of the medium inside the tank remains almost constant ； And changes in ambient temperature cause changes in the density of the medium, so naturally the liquid level will change as well.
This post was last edited by hyqing2007 on 2016-3-7 at 10:45. The transmitter is connected directly to the ammonia sphere tank via flanges; there are no valves between the transmitter and the tank, so the possibility of blockage is low
This post was last edited by hyqing2007 on 2016-3-7 at 10:40. The temperature difference is now only around 10°C, so the change in density is minimal; consequently, the change in liquid level should also be small. There’s no chance of a change of around 20% – that would be too large!
In the case of a diaphragm transmitter, check what type of silicone oil is used and whether it is suitable for the current ambient temperature.