For the nitrogen sealing control scheme in atmospheric pressure tanks, what are the specified pressure values before the nitrogen sealing valve?
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Dear teachers: I would like to ask about your company’s control scheme for nitrogen sealing in atmospheric-pressure tanks – what are the specifications regarding the pressure value before the nitrogen sealing control valve?
The pressure in the tank is maintained under nitrogen at atmospheric pressure; the pressure before the control valve is reduced using a self-acting control valve, with the resulting pressure being 0.15 MPaG
Thank you for Lingyun’s reply! That’s right, Teacher Lingyun. Our company currently has 29 atmospheric pressure intermediate tanks. Our superiors have hired a team of experts for design review, who have requested that a nitrogen sealing and control system be added to each tank. Our preliminary idea, in collaboration with the design institute, is to install a pressure transmitter on each tank to generate a 4-20MA signal for measuring pressure. We also plan to use two sets of control valves to regulate the inflow and outflow of nitrogen. I’m not sure whether this approach complies with the latest design standards, and what risks might arise from using this design in the future For example, what is the risk if any one of these valves loses control?
@For Dugu Lingyun, the pressure before the nitrogen regulation valve in the tank is currently 0.6 MPa.
This post was last edited by ssln123 on 2022-5-26 at 17:42. The method of range regulation is currently used for automatic control in applications that require high precision. From a safety perspective, using FC for the nitrogen make-up valve and FO for the pressure relief valve can meet the safety requirements. If we go for something simpler, it could be a self-acting control valve combined with a vent valve.
Using a single pressure point to control two control valves for nitrogen inlet and exhaust is a typical proportional control approach, which is a well-established control scheme. For safety reasons, it is necessary to define the failure modes of the nitrogen valve and the exhaust valve; what was said on the 5th floor is very good
It is difficult to control the nitrogen pressure from 0.6 MPa to 50 kPa using a single valve. Our current implementation plan is to use a pressure reducing valve of 0.6 MPa, of the self-acting type (located after the stabilizing valve), to reduce the nitrogen pressure to XXX value, and then install an adjustable valve. For reference only among peers
There is no better solution for proportional control at the moment
Thank you to the teachers on floors 5, 6, 7, and 8!
1. It is recommended to install 2 pressure transmitters in the tank. 2. A float flow meter should be installed on the nitrogen inlet pipeline, as this provides the most direct way to monitor the flow rate. 3. For the safety of the tank, a control valve or a self-acting valve should be installed to reduce the nitrogen pressure to a safe level; a pressure transmitter should also be installed on the main nitrogen inlet pipeline. 4. A check valve should be installed on the nitrogen inlet pipeline. 5. For large tanks, step control is not very effective