Nitric Acid Solution Hydraulic Diaphragm Metering Pump

Nitric Acid Solution Hydraulic Diaphragm Metering Pump

For the application of 74% nitric acid solution, combined with the recommended YDJCM-300/1.7 hydraulic diaphragm metering pump, 

a technical analysis is conducted from four perspectives: material compatibility, pressure safety, precision control, and operation and

 maintenance risks.

1. Material Compatibility: 316L wetted material can meet the requirements, but the sealing structure requires optimization.

Pump Body Material:

Nitric acid solution (74%) is highly corrosive to metals. 304L stainless steel is only suitable for nitric acid concentrations ≤ 65% at room 

temperature. 316L stainless steel (containing 2-3% molybdenum) has significantly better nitric acid corrosion resistance than 304L and 

can withstand nitric acid at all concentrations (temperature control ≤ 60°C).

Recommendation: Confirm that the pump body is actually made of 316L (not coated or lined) and request the supplier to provide material

 certification (such as ASTM A240 standard).

Seal Material:

The original design used 304L as the wetted material. However, seals (such as O-rings and diaphragms) made of rubber (e.g., EPDM) can

 be corroded by nitric acid, leading to leakage.

Optimization Solution:

Diaphragms: Use PTFE (polytetrafluoroethylene) for excellent nitric acid corrosion resistance (corrosion rate <0.001 mm/year).

Seals: Replace with FFKM (perfluoroelastomer) or PTFE-coated rubber to prevent nitric acid penetration.

II. Pressure Safety: The 1.7 MPa rated pressure meets the requirements, but additional safety margins are required.

System Pressure Analysis:

The pump outlet pressure requirement is 1.7 MPa, and the built-in safety valve opening pressure is 2.3 MPa (135% of the rated pressure),

 complying with API 675 (safety valve opening pressure ≤ 1.25 times the rated pressure).

Risk Point: The saturated vapor pressure of nitric acid solution (approximately 0.05 MPa for 74% nitric acid at 20°C) is low, but transient 

pressure spikes (such as water hammer) may occur during pump startup/shutdown.

Optimization Suggestions:

Add a secondary safety valve: Install a safety valve with a cracking pressure of 2.0 MPa (such as the Anderson Greenwood 440 series 

from the US) on the pump outlet line to provide dual protection.

Install a pressure buffer: Install a pulse dampener (nitrogen-filled, pre-charge pressure = 1.5 x system average pressure) at the pump

 outlet to reduce pressure fluctuations.

III. Accuracy Control: Variable frequency motors can achieve flow regulation, but closed-loop control is required to maintain >1% accuracy.

Original Design Accuracy:

The pump's nominal accuracy is not specified, but hydraulic diaphragm metering pumps typically have an accuracy of ±1.5% (open-loop 

control).

The density of nitric acid is 1.42 g/cm³ (much higher than that of water), requiring a correction to the flow calculation: Actual mass flow 

rate = 300 L/h x 1.42 = 426 kg/h.

Optimization Solution:

Closed-loop variable frequency control:

Add an electromagnetic flowmeter (such as the Krohne MF series, made of nitric acid-resistant PTFE) to output a 4-20 mA signal to a

 variable frequency drive (such as the Schneider ATV630 series).

Inverter parameter settings: PID adjustment cycle ≤ 0.1 second, response frequency ≥ 50 Hz, ensuring flow fluctuation ≤ ±0.5%.

Density compensation: Integrate a density-flow correction algorithm into the DCS system (adjust the inverter output in real time based

 on the nitric acid concentration-temperature-density curve).

IV. Operation and Maintenance Risks: Diaphragm monitoring and hydraulic oil management need to be strengthened.

Key Risk Points:

Diaphragm rupture: 74% nitric acid accelerates diaphragm aging (PTFE diaphragms have a lifespan of approximately 8,000 hours). Nitric

 acid leakage after a rupture could cause a safety accident.

Hydraulic oil emulsification: Diaphragm rupture can cause nitric acid to seep into the hydraulic oil chamber. Emulsification of the hydraulic

 oil will cause the hydraulic oil to lose its lubricating properties, accelerating pump head wear.

Optimization Suggestions:

Diaphragm Monitoring:

Use a double diaphragm structure (such as the German Altech FKM series) and fill the space between the inner and outer diaphragms

 with glycerin (as a monitoring medium).

Install a diaphragm rupture sensor (pressure switch or level switch) to trigger an alarm and shut down the machine in the event of a leak.

Hydraulic Oil Management:

Use ISO VG32 anti-wear hydraulic oil (containing anti-corrosion additives) and replace it every three months.

Install a hydraulic oil acid value tester (such as the Koehler K83100). Replace the oil immediately if the acid value exceeds 0.5 mgKOH/g.

For further pricing or technical details on specific models, please contact a professional supplier

 CIXIFM winny, Email: sales01@cxflowmeter.com, WhatsApp: +86 18049841995