It should be clarified that the head is not geometrical characteristic and is not the height to which a pump can lift pumped medium. It is denoted by letter H and has dimension in meters. Head – energy imparted by pump to the pumped medium and attributed to unit of pumped medium mass. In the majority of cases a pump is selected for the particular pipeline system and flow rate value is set in advance. The theoretical and factual flow rate ratio is expressed by volumetric efficiency quantity:īut in modern pumps thanks to reliable sealing of pipelines and joints the factual capacity coincides with theoretical. Flow rate quantity includes only factual volume of displaced fluid ignoring return leakages. It is denoted by letter Q and has dimension in m 3/h, l/s, etc. Regardless of diversity of machines used for pumping of fluids and gases, a number of key parameters defining their functioning: capacity, power consumption and head can be singled out.Ĭapacity (delivery, flow rate) – volume of medium pumped by a pump per unit of time. Tables which in general terms reflect application boundaries of most wide-spread types of pumps are given below.įield of application (selection) of pumps by the created head In the situation like this preference is given to the type of pump which is most suitable under concrete values of key design parameters (capacity, head and power consumption). Operational requirements specified by different industries can be satisfied by several types of pumps. Corrosion properties of the pumped medium determine material design of the selected pump, and toxicity – degree of its air-tightness. So screw pumps can pump viscous media with different inclusions without damaging structure of the medium, and can successfully be used in food-processing industry for pumping of jams and pastes with various fillers. Different types of pumps are suitable for pumping of various media differing in viscosity, toxicity, abrasiveness and many other parameters. The pump process and design requirements are seldom definitive, and ranges of suitable types of pumps for various specific cases of application are known as a matter of experience accumulated by humanity, and there is no need to enumerate them in detail.Ĭharacteristics of the pumped medium often become a decisive factor in pumping equipment selection.
#Negative pressure in watergems install
Example of definitive design requirements can be the use of submerged pumps in cases, when it is necessary and only possible to install the pump below level of the pumped fluid. At the same time, delivery of pumped medium in discrete portions of set volume can also be a process requirement. Unlike piston-type pumps, centrifugal pumps can provide uniform delivery of pumped medium, whereas in order to meet uniformity condition on a piston-type pump its design has to be made noticeably complicated, by arranging on the crankshaft several pistons making reciprocating movements with certain delay from each other. In some cases the pump selection is determined by some stringent requirements for a number of design or process parameters. During selection of the type of pump three groups of criteria can be distinguished: Selection of the pumping equipment is a crucial point that determines both process parameters and in-use performance of the unit under development.