PUMPS Factors Affecting Pump Selection 1 The amount

PUMPS

Factors Affecting Pump Selection 1. The amount of fluid that must be pumped. 2. The properties of the fluid. 3. The increase in pressure of the fluid due to the work input of the pumps. 4. Type of flow distribution. 5. Type of power supply. 6. Cost and mechanical efficiency of the pump.

CENTRIFUGAL PUMPS Definition: A pump which uses centrifugal force to develop velocity in the liquid to be handled. The velocity is then converted to pressure as kinetic energy is decreased. Centrifugal pumps main components: Centrifugal pumps basically consist of: 1. Stationary pump casing 2. Impeller mounted on a rotating shaft 3. Suction line 4. Discharge line

Pump casing may be (one fabricated piece) or split casing (two or more parts together)

Classification of Centrifugal Pumps 1. According to the pump casing Volute Centrifugal Pump

Diffuser Centrifugal Pump

Diffuser Centrifugal Pump

2. According to the impeller type Open impeller Semi open impeller Enclosed impeller

To aid in understanding the pump details and to see the semi closed impeller

Single Suction and Double Suction Impellers

3. Classification by Flow Centrifugal pumps can be classified based on the manner in which fluid flows through the pump. The manner in which fluid flows through the pump is determined by the design of the pump casing and the impeller. The three types of flow through a centrifugal pump are: A. Radial flow, B. Axial flow, C. Mixed flow.

Multi-stage Centrifugal Pumps

Multi-stage Centrifugal Pumps

Centrifugal Pump Components Centrifugal pumps vary in design and construction from simple pumps with relatively few parts to extremely complicated pumps with hundreds of individual parts. Some of the most common components found in centrifugal pumps are: 1. wearings, 2. stuffing boxes, 3. packing, and 4. lantern rings.

The packing material may be: Asbestos, Nylon, Teflon, Lead, Copper or Aluminum Stuffing box and packing

Simple View for Lantern Ring and Stuffing Box

Mechanical Seals ØWhat are mechanical seals ØComponents of mechanical seals ØTypes of mechanical seals ØAdvantages and disadvantages of mechanical seals

Mechanical Seals ØUsed when packing material is not adequate for sealing the shaft. ØMechanical seals consist of two basic parts (faces), a rotating element attached to the pump shaft and a stationary element attached to the pump casing. ØOne of these element is called the sealing ring and is held in position by a spring. The other sealing element which is in contact with the sealing ring is called the mating ring. ØEach of these elements has a highly polished sealing surface. ØThe polished faces of the rotating and stationary elements come into contact with each other to form a seal that prevents leakage along the shaft.

Types of Mechanical Seals A. The rotating mechanical seal The sealing ring and the spring are rotating with the shaft and the mating ring is held stationary in the pump casing.

The rotating mechanical seal

B. Stationary Mechanical Seals ØThe sealing ring is held stationary within the pump housing. ØThe mating ring is fastened rigidly to the shaft. As the pump shaft turns so does the mating ring. ØThe stationary sealing ring bears against the rotating mating ring and leakage between the two faces is prevented.

Stationary Mechanical Seals

Advantages of Mechanical Seals ØThey require much less maintenance ØThey reduce leakage to a minimum ØThey can be designed to work under very high temperatures and pressures Disadvantages ØThey have greater capital cost than packing ØWhen they fail, pump must be stripped down for service for longer period to replace or repair seal.