Online differential pressure density gaugeIt is a device used for continuous online measurement of liquid concentration and density, widely used in industrial production processes. Its working principle is based on Pascal's principle, which calculates density by measuring the differential pressure of liquid at a certain vertical distance, and can automatically perform temperature compensation to ensure measurement accuracy. This device adopts an integrated two-wire transmitter structure, with no moving parts, simple installation and use, and easy maintenance.
The online differential pressure densitometer is suitable for flowing or stationary liquids and can be installed in pipelines or tanks. It supports various contact materials such as 316L stainless steel, tantalum, titanium, etc., to meet different working conditions. Its output signal is 4-20mA, which can be remotely calibrated and monitored through digital communication. It also has LCD display function, which can simultaneously display temperature and density parameters, making it easy to convert industry standards.
Online differential pressure density gaugeOperation steps:
Step 1: Pre Commissioning Check
Appearance inspection:
Check for damage, leaks, and looseness in the instrument casing, process connection flanges, pressure pipes, valves (three valve group/five valve group), and junction boxes.
Confirm that all valves are in the correct initial position (usually: high pressure valve closed, low pressure valve closed, balance valve open, drain valve closed).
Pipeline inspection:
Confirm that the pressure pipeline is unobstructed and free from severe bending or deformation.
Check if the isolation fluid (such as capillary filling fluid) system is intact and leak free.
Electrical inspection:
Check if the power and signal lines are securely connected.
Confirm that the power supply voltage meets the requirements of the instrument.
Check if the grounding is reliable.
Environmental confirmation:
Confirm that the ambient temperature and humidity are within the allowable range of the instrument.
If there is heat tracing, confirm that the heat tracing system is enabled and working properly.
Step 2: Commissioning/Cutting into Service
The core of this step is to safely and smoothly connect the instrument to the process system, avoiding any impact on the sensor.
Open the balance valve:
Firstly, ensure that the Vent/Balancing Valve is in the open position. This equalizes the pressure on the high (H) and low (L) sides of the differential pressure transmitter, protecting the sensor diaphragm.
Open the high-pressure side isolation valve:
Slowly open the High Pressure Isolation Valve and allow the process medium pressure to slowly fill the high pressure side pressure pipe.
Open the low pressure side isolation valve:
Slowly open the Low Pressure Isolation Valve and allow the process medium pressure to slowly fill the low-pressure side pressure pipe.
Close the balance valve:
After the pressure on the high and low pressure sides is balanced (which can be confirmed by the transmitter reading that Δ P ≈ 0), slowly close the balance valve. At this point, the differential pressure transmitter begins to sense the true differential pressure generated by the liquid level difference H.
Check for leaks:
After operating each valve, carefully check all connection points for leaks.
Observation reading:
The instrument should start displaying the differential pressure value (Δ P). According to the formula ρ=Δ P/(g * H) (where g is the acceleration due to gravity and H is the fixed height difference), the instrument calculates and outputs the density value internally.
Observe whether the reading is stable and reasonable.
Step 3: Operation Monitoring
Read data:
Read real-time density values through the local display screen of the instrument or DCS/SCADA system.
Simultaneously pay attention to auxiliary parameters such as differential pressure (Δ P) and temperature (if integrated).
Trend analysis:
Monitor the trend of density values and determine whether they meet the expected process requirements (such as reaction progress, mixing ratio, concentration changes).
Alarm response:
If the instrument issues high/low density alarms, sensor malfunctions, damping alarms, etc., immediately record and handle them according to regulations.
Regular inspection:
Check the appearance of instruments, pipelines, and valve status according to the inspection route.
Step 4: Zero Calibration (performed periodically or as needed)
When there is suspicion of systematic deviation in the measurement (such as readings that are not theoretical when using empty tubes or known density media).
prepare
Ensure that the process conditions permit (preferably under parking or stable operating conditions).
Confirm that the fluid inside the measured pipeline is filled and stationary, or use a liquid/gas with the same (or known) density as the measured medium to completely fill the measuring pipe section to the same horizontal plane, ensuring that Δ P is truly zero.
Perform calibration:
Enter the settings menu of the instrument panel.
Select the "Zero Calibration" or "Zero Trim" function.
Follow the prompts to confirm execution. The instrument will store the current Δ P reading as the new zero point.
verification:
After calibration, observe whether the reading has been corrected.
Step 5: Shutdown/Isolation
When maintenance, overhaul, or long-term shutdown is required.
Open the balance valve:
Firstly, slowly open the balance valve to allow the pressure on the H and L sides to balance again and protect the sensor.
Close the high-pressure side isolation valve:
Close the high-pressure side isolation valve.
Close the low pressure side isolation valve:
Close the low pressure side isolation valve.
Pressure relief and emptying (if necessary):
Open the Vent/Drain Valve on the high and low pressure sides to safely discharge the medium in the impulse piping to the designated container or system.
Attention: The discharged medium may be high temperature, high pressure, toxic or flammable, and must be handled in accordance with safety regulations.
Locking and Listing (LOTO):
Lock and tag relevant valves and power supplies to prevent accidental operation.
Step 6: Resume operation
When maintenance is completed and the instrument needs to be put back into use, strictly follow the steps of "Step 2: System Use" and do not directly open the isolation valve!