Chemical dosing systems are essential equipment for controlling and optimizing industrial processes in the oil and gas, petrochemical, water treatment, and energy industries. These systems are used for the precise dosing of corrosive substances, corrosion inhibitors, antiscalants, or acidity regulators into process lines.
Safety and pressure stability are crucial in these systems, as a sudden increase in pressure can damage the dosing pump, piping, or downstream equipment. This is where pressure relief valves come into play.
What is a safety valve?
A pressure relief valve is a mechanical device that protects a system from excessive pressure. If the pressure in any part of the system exceeds the permissible limit, the valve automatically opens and releases fluid until the pressure returns to a safe level. Once the pressure drops, the valve closes, and the system resumes normal operation.
The importance of pressure relief valves in chemical injection systems
In chemical injection systems, injection pumps are typically metering pumps capable of generating relatively high pressures . A blockage in the injection line or increased pressure in the discharge line for any reason can cause severe damage to the pump or rupture of the piping . Therefore, the installation of pressure relief valves at the pump outlet and upstream of the main injection line is a technical and safety requirement.
The main functions of the pressure relief valve in this system are:
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Protects the high-pressure fuel pump from overpressure.
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Do not allow pipes and fittings to burst.
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Ensuring the safety of operators and the environment.
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Helps extend equipment life and reduce maintenance costs .
The operating principle of a safety valve
A pressure relief valve typically consists of a spring and a disc (or piston) . Fluid pressure acts on the disc, and the reaction force of the spring prevents the valve from opening.
If the system pressure exceeds a set value , the fluid pressure overcomes the spring force, causing the valve to open. If fluid escapes, the pressure drops, and the spring returns the disc to its original position, closing the valve.
In injection systems , the opening pressure of the pressure relief valve is usually set 10–15% higher than the operating pressure of the system so that the normal operation of the pump is not disturbed and the pump is only activated in emergency situations.
Types of pressure relief valves used in chemical injection systems
Depending on the type of fluid and operating conditions, different types of safety valves are used:
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spring-loaded safety valve
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This is the most common type of pressure relief valve.
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It is characterized by its simple structure and low maintenance costs.
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Suitable for liquid and gaseous fluids.
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pilot-operated safety valve
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Suitable for high pressure systems or systems requiring more precise control.
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Smoother and more responsive operation than the spring type.
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Diaphragm safety valve
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Suitable for use with corrosive or toxic liquids where contact with metal parts must be minimized.
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The membrane is usually made of PTFE or FEP.
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Material and type of valve body
For chemical injection equipment, the materials of the pressure relief valves should be selected based on the type of material being injected, the temperature, and the operating pressure . The following materials are commonly used:
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For acidic and weak chemicals, PVC or PP materials are used.
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PVDF or PTFE are suitable for highly corrosive media such as sulfuric acid or caustic soda.
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Stainless steel grades 316 or 304 are suitable for general industrial applications and high-pressure environments.
For critical projects , valves made entirely of PTFE are recommended to ensure maximum corrosion resistance.
Installation location of the safety valve
In chemical injection systems, a pressure relief valve is preferably installed at the injection pump outlet, upstream of the main check valve
. When pressure rises, the fluid flows back through the pressure relief valve into the storage tank or return line . This prevents chemical loss and ensures safe, closed-loop operation of the system.
Important points when choosing a safety valve
To select the right safety valve, the following criteria must be considered:
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Working pressure of the system
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Valve opening pressure (set pressure)
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Discharge capacity
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Type of liquid and its chemical properties
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Temperature and viscosity of the liquid
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Housing materials, springs and internal parts
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Pipe connection (thread or flange)
Selecting the wrong pressure relief valve can result in poor system performance , leaks, or even serious hazards.
Regular maintenance and inspection
Like other components of the injection unit, the pressure relief valve must be checked and maintained regularly . It is recommended to check its function at least every six months to prevent spring seizure or damage to the valve plate.
When performing maintenance, please note the following:
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Remove all deposits and residues from the internal parts.
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Make sure the spring and diaphragm are intact.
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Restore the opening pressure if necessary.
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Use original and standard spare parts.
Relevant rules
Safety valves are typically designed and tested according to international standards, including:
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API 520/API 526
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ASME Section V
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ISO 4126
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DIN EN 4126
Compliance with these standards ensures accurate and reliable operation of safety valves in emergency situations.
Finally
Safety valves are not only a technical requirement in chemical injection systems , but also a key factor for safety , operational stability, and equipment protection . Choosing the right valve type, housing material, and correct opening pressure setting helps prevent serious damage and sudden system failures. Choosing a reliable brand and regular maintenance also ensure reliable operation and a long service life of the injection system.
Final quote
When designing or purchasing a chemical delivery system, pay special attention to the configuration and quality of the pressure relief valve . In many cases, the lower cost of a standard pressure relief valve can prevent tens of millions of dollars in damage from pump failures or chemical leaks.