Valve selection Flashcards
Shut-off valve or?
Block or isolation valve
Can be manual or automatic
Control valve
Example of shut off valve
Gate
Plug
Ball
Gives positive seal in the close position and minimum resistance flow to flow when open
Shut off valve
+available in the widest range of sizes and can be operated manually or by a motor
• have a straight-through flow channel and low
pressure drop when fully open
Gate valve
best used when operated infrequently, as they
require several turns of the valve handle to close
Should not be opened partially as valve seals could be deformed
Gate / Slide
• have the advantage that they only require a
quarter turn to open or close
• often actuated by solenoids and are used
where quick on-off switching is needed
Plug and Ball valve
Normally used flow control valve
Globe valve
Commonly used control valve
Diaphragm valve
Used for the control of gas and vapour flows
Butterfly
Usually globe valves with special trim designs
Automatic control valves
Good flow while keeping
Pressure drops low
Valve must be sized to avoid:
Flashing out of hot liquid
Super critical flow of gases and vapours
are used to
prevent back-flow of fluid in a process
line.
• They do not normally give an absolute
shut-off of the reverse flow.
Non-return valves
depend
on gravity to close the valve, care
must be taken to orient the valve
properly when locating and installing it.
Swing- type check balvo
Two general types of pump
Dynamic
Positive displacement
Example of dynamic pump
Centri
Examples of positive displacement
Reciprocating and diaphragm
Most commonly used type in chem. Indus
Single-stage, horizontal, overhung centrifugal pump
When small flow rates of additive must be added to a process, what will you use?
Positive displacement metering pumps
Pp selection is made on? (2)
Flow rate
Head required
Impeller specific speeds usually lies between
400-20K based on impeller type
Pump impellers classification
Centri or radial
Mixed flow
Axial
Specific speeds between 400 and 4000
Centri or radial
