The nitrogen seal valve continuously supplies nitrogen on rainy days
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The company has several nitrogen seal valves of the Pivo K25108 type for use with tanks; these valves have a rated pressure of 0.8–1.2 KPA. They functioned normally at first, but recently one of the tanks began to require significant amounts of nitrogen to be added whenever it rained – the pressure would rise above 2.8 KPA each time, and this continued for about half an hour after the rain stopped. No leaks were detected in the tank, and a new valve was installed, but the problem persisted even after that, within less than a month of use. Solve? The other tanks are functioning normally.
What drives this valve to perform its on/off function? This driving mechanism may change when it is raining. Or, due to differences in the heat transfer properties of the medium or the casing, the pressure changes on rainy days are different from those in other situations
Thin-film, self-acting (post-valve) micro-pressure control valve. Normally, nitrogen supplementation stops automatically at around 1.4 KPA; for tanks of the same type, if only one tank has a problem, it has been checked that the medium inside the tank and the heat transfer properties of the tank’s exterior are identical. It is sunny now, and the nitrogen seal valve has returned to normal.
Is the medium in this tank different from that in the other tanks? Moreover, this medium is highly affected by temperature! !
Two tanks have the same medium, and the pressure change in the other tank is within the allowable range. In the problem tank, when the sun came out and the intake valve was closed, the pressure increased from 0.093 KPA to 1.497 KPA. The liquid levels, medium, and temperature of the two tanks are identical.
The nitrogen sealing pressure isn’t high, so there’s no need to worry too much; if you’re concerned, have the instruments checked it.
What is the medium in the storage tank? Whether nitrogen is added through the nitrogen seal depends mainly on the pressure in the storage tank; when the pressure drops, the feed valve for the nitrogen seal opens to add nitrogen, while if the pressure is high, nitrogen is released. Given that this situation occurred on a rainy day, and it may be due to temperature changes – the pipe walls being exposed to rain causing the storage tank to cool down, which in turn reduces the vapor pressure inside the tank – nitrogen is then added. Once the rain stops and the temperature rises, the vapor pressure increases, and nitrogen is released from the tank. Recommendation: Insulate the outer wall of the storage tank.
1. Is there a low point between the nitrogen seal valve and the monitoring pressure, which results in the data collected by the valve not being accurate and leads to continuous pressure replenishment?； 2. Has the zero point of the nitrogen seal valve shifted?
Where is the original poster? Is it because of poor insulation of the storage tank, with temperature dropping and pressure falling on rainy days, which in turn requires nitrogen to be added?~ ? ?
This post was last edited by ylb913 on 2015-6-23 at 15:20. 1. It’s likely that the pressure tapping port of the self-regulating valve is blocked; clearing it should resolve the issue. A certain amount of gas is trapped between the blockage site and the pressure measurement site; when the temperature is high and the sun shines directly, the pressure increases. If no additional pressure is applied, the pressure inside the storage tank may be relatively low (though this is not always the case, as the pressure in the gas phase above the tank also rises with increasing temperature). When it rains, the temperature drops, or external factors affect the heat tracing effect, this pressure will decrease. Since it is a very small space with its surroundings in contact with the atmosphere, the degree of pressure drop must be greater than that in the storage tank; this is why over-compensation for pressure occurs. 2. We have two atmospheric-pressure storage tanks, each equipped with a pressure display. Under normal conditions, the pressure range is -500 to 2000 Pa. The gas outlets from these tanks are combined before being discharged outside; sometimes one of the pressures remains relatively stable, while the other changes very sensitively with temperature (especially when exposed to direct sunlight). In such cases, the issue is resolved by clearing the blockages.
The conditions are not complete; nitrogen is added only when the internal pressure of the equipment is too low. Reasons for low pressure include nitrogen leaks, temperature changes that result in insufficient gas pressure, and excessive use of the material stored in the tank. After nitrogen is added, once the rain stops and the ambient temperature rises, the pressure inside the tank increases, causing the valve to release pressure due to overpressure. However, you mentioned that conditions such as heat transfer are the same as those in other tanks, so a leak in the tank itself can be ruled out. Please check the sealing material of the valve to rule out any valve-related faults