Have you seen any single-flange differential pressure transmitters whose negative pressure side is connected to the vapor phase side of the container?

This method is commonly used for measuring the liquid level in atmospheric or open containers; if migration is required, it is positive migration

I have never seen this method of measurement before; I wonder if the original poster has seen it with their own eyes? Is the vapor temperature high? I mean temperatures above 100 degrees.

It’s a pressure vessel; the positive or negative pressure within the vessel needs to be balanced. Open tanks, on the other hand, do not require a venting system

When a single-flange level transmitter is used to measure the level in a container at atmospheric pressure, the negative pressure side can be connected to the atmosphere； When measuring the liquid level in a pressurized container, the negative pressure side must be connected to the gas phase.

No problem, but a drain valve must be installed on the negative pressure side

Where is the negative pressure side on a single-flange level gauge? If it is necessary to measure the level of equipment under pressure (either positive or negative pressure), a double-flange level gauge must be used. :lol :lol

It’s on the 7th floor; you can’t just make things up without seeing it, right? . Please refer to the automatic control installation manual HG/T21581-95, diagram HK04-415

Single-flange differential pressure level gauges are widely used. For containers that require a high level of leakage prevention, a double-flange differential pressure level gauge should be used, while for containers used for storing ordinary substances, a single-flange differential pressure level gauge is sufficient ； For a pressure vessel that is at atmospheric pressure, a single-flange negative pressure pressure transfer tube can be connected directly to the atmosphere. If the vessel is under pressure, the pressure transfer tube must be connected to the gas phase of the liquid tank; however, a vent valve should be installed on the negative pressure side to prevent the blockage of the negative pressure pressure transfer tube, which could lead to measurement errors in the instruments.

Sure, no problem. For measuring liquids that are corrosive, viscous, prone to crystallization, volatile, containing suspended solids, or prone to gelation and precipitation, flat flange or insert flange differential pressure transmitters are recommended. If the tank being measured is a device at atmospheric pressure, no pressure transfer tube is connected to the negative pressure chamber ； If the tank being measured is a constant-pressure device, a pressure transfer tube is connected to the gas-phase portion of the negative-pressure chamber. If the gas phase temperature is high, a condenser can be added ； If the gas phase also presents problems such as viscosity and tendency to crystallize, then a separator tank should be installed at the top of the pressure guiding pipe in the negative pressure chamber, or a dual-flange differential pressure transmitter should be used.

Correction: The term “equipment under normal pressure” that appears the second time should be “equipment under pressure”; it was a typing error.