Semi open impeller

Open Impeller Semi-open Impeller Closed Impeller... 

A semi-open impeller has exposed blades, but with a support plate or shroud on one side. Some people prefer the name semi-enelosed. These types of impeller are generally used for liquids with a small percentage of solid particles like sediment from the bottom of a tank or river, or crystals mixed with the liquid (Figure 6-17). 

The internal volute wall and/or hack plate on pumps with open and semi open impellers. 

KOpen Impeller Semi-open Impeller Closedimpeller... 

Pumps with semi-open impellers in an erosive service shall have a replaceable casing liner. 

Fig 19b Semi-open impeller for handling fluids containing pulpy solids (courtesy of Nagle Pumps)... 

The sani-open impellers have only one wearing ring. For liquids having comparatively high viscosity like molten sulfur a semi-open type impeller is usually preferred. These impellers are non-clogging and easy to clean whenever the pump is removed for maintenance. The frontal clearance, i.e., the distance between the suction plate/cover face and the impeller is very important when using a semi-open impeller. An increase in the frontal clearance drastically reduces the head or flow of the pump. 

These are used in phosphatic fertiliser industries where silica/other particulate matter tend to deposit on the walls of the tower. The vendor should specify the number of nozzles, flow rate through each, circulation pump capacity (it should have semi-open impeller) and MOC of pipes, valves, etc. 

Impellers can be open, semi-open, or enclosed. The open impeller consists only of blades attached to a hub. The semi-open impeller is constructed with a circular plate (the web) attached to one side of the blade. The enclosed impeller has circular plates attached to both sides of the blades. 

There are three basic impeller styles, full open, semi-open, and full closed, see Figure 4. The full open impeller has its vanes extended from its hub without front cover plate and back sliroud. The semi-open impeller has its vanes on the biEick shroud, but without front cover plate. The full closed impeller has its vanes enclosed and supported by both the front cover plate and back shroud. Most vanes on the impeller are curved backward to the direction of rotation. 

Semi-open or seml-enclosed impeller. (Courtesy Goulds Pumps Inc.)... 

Impeller type shall be selected for the application and may be open, semi-open, or fully enclosed. 

Types. Impellers of open, semi-open, and closed designs are optional. 

Circulation pump capacity, head, impeller design (shonld be semi-open type if more suspended solids or ciystals will be present in the solution), power consumption, shaft seals to be informed by vendor. This will depend on the length of the tubes, flow velocity, density of the solntion and whether boiling will be allowed or not allowed in the tnbes. 

Figure 21.10 Open, semi-open, and enclosed impellers...

---