Selection and Verification of Liquid Ammonia Pump

With the development of the mechanical industry, the usage rate of pumps has greatly increased. Liquid ammonia pumps are a type of chemical pump suitable for transporting flammable, explosive, toxic, harmful, and corrosive liquid media. Although widely used, it is not a universal pump and has its own scope of application. If it does not meet its scope of application, it is not enough to choose. Therefore, users need to preliminarily determine the process parameters of the pump based on the following content:
1、 Physical and chemical properties of the conveying medium
The physical and chemical properties of the conveying medium directly affect the performance, materials, and structure of the liquid ammonia pump, and are important factors to consider when selecting. The physical and chemical properties of the medium include: medium name, medium characteristics (such as corrosiveness, toxicity, etc.), presence or absence of solid particles and crystals, density (specific gravity), viscosity, vaporization pressure, etc.
2、 Process parameters
Process parameters are an important basis for selecting liquid ammonia pumps, and should be carefully determined based on the requirements of the process flow and the range of operational changes.
1. Flow (Q): Flow refers to the mass of medium required to be pumped by the process unit during production and operation. Users should generally provide normal traffic, lower traffic limit, and upper traffic limit. The flow rate listed on the product sample is the rated flow rate, also known as the upper limit of flow rate. When selecting models, it is required that the rated flow rate is not less than the upper limit of the device's flow rate. Generally speaking, the rated flow rate is 1.15 times the normal flow rate. The lower limit of flow shall not be less than 30% of the rated flow.
2. Head (H): Refers to the required head value of the process unit, also known as the calculated head. The head value on the product sample is the rated head, which is the upper limit total head. The rated head of the pump is generally required to be 1.1 times the required head of the device. For media with a viscosity greater than 20mm2/s, it is also necessary to convert it into the rated flow rate and head when transporting clean water. By comparing the type spectrum of the pump series with the rated flow rate and head, the flow rate and head are placed within the corresponding operating range of the pump, thus proposing the specific models and specifications of one or more liquid ammonia pumps.
3. Inlet pressure and outlet pressure: The inlet and outlet pressure refers to the pressure at the flange of the pump suction and discharge nozzles. The magnitude of inlet and outlet pressure affects the pressure resistance requirements of the pump body and sealing isolation sleeve.
4. Temperature: Refers to the temperature of the pumped medium. Users should generally provide the normal temperature, lower limit temperature, and upper limit temperature of the pump inlet medium during the process.
5. Device NPSHa: The NPSHa of a device is determined by the pump system (based on the rated flow rate and normal pumping temperature of the liquid), also known as the effective or available NPSHa (measured in meters of liquid column). Its size is determined by the parameters of the suction pipeline system and the flow rate in the pipeline, and is independent of the pump structure. The NPSH of the device should be provided by the user. To ensure that cavitation does not occur, the device NPSHa of the liquid ammonia pump must have a safety margin S. Generally speaking, S is taken as 0.6m~1.0m.
The selection and calibration of liquid ammonia pumps are very important steps for both users and manufacturers. Users can preliminarily select the parameters and requirements of the liquid ammonia pump based on the above guidelines. In order to ensure that there are no errors in the selection and that the selected pump can meet the process requirements, it is advisable to communicate with the manufacturer as much as possible.