valves, types and operations
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Valves,
Types, and
Operations Prepared by
Osama Hasan Intern ‘11 Batch 03 (Enven 1.3)
Engro Fertilizer
Mentor: Aah
1 July 2011
Outline
Valve
Construction
Types
Gate, Globe, Plug, Ball, Diaphragm, Check
Operations
Fouling, Stem Breakage, Packing Leakage,
Gaskets Leakage
Valves,Types and Operations
2
Valve
Mechanical devices that are used in
industrial piping for flow control by varying
the pipe opening in three positions:
Fully opening
Fully closed and
Throttling
3
Valves,Types and Operations
See Animation
Construction Body; connected to the pipe
Bonnet; mounted on the body to form a tight enclosure
Stem; attached the structure (gate or disk) that resist the flow
The body of the valve is flanged with bolt holes in them to be
held together with pipe; with a gasket in between to provide a
leak-proof connection
4
Valves,Types and Operations
Construction Gate or Disk; controls the
opening
Stuffing Box; located in bonnet and filled with packing, holds the stem and avoids leaks
Hand Wheel; lifts gate or disk on rotating and vice versa
Seat Rings; perpendicular to flow, make close fit with valve for complete shut down
5
Valves,Types and Operations
Construction Yoke (For OS & Y);
supports hand wheel and bushing
Flange (for NRS only); resists the stem to move up or down
Valves are characterized by the way they resist the
flow.
6
Valves,Types and Operations
Types
Gate Valve
Globe Valve
Plug Valve
Ball Valve
Diaphragm Valve
Butterfly Valve
Check Valve
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Valves,Types and Operations
Gate Valve Complete Open / Close
Emergency Shut Down
8 Valves,Types and Operations
Gate Valve
Regulates flow by placing a metal gate or
disc across the opening of pipe.
the gate has to be strong enough to
withstand the pressure of flow.
Gate valves are of two types:
Outside Stem and Yoke (OS & Y) and
Non-Rising Stem (NRS)
9
Valves,Types and Operations
See Animation
OS & Y Gate Valve Stem is Threaded at the
hand wheel and screwed through stem bushing
Solidly connected with the hand wheel and turns along with it
Bottom is solidly connected to the gate, neither of which can turn
10
Valves,Types and Operations
OS & Y Gate Valve
The hand wheel and
bushing are also
supported by an
outside yoke.
Stem can be seen
when the valve is
open, therefore needs
stem clearance.
11
Valves,Types and Operations
NRS Gate Valve
Stem threaded on
the bottom, with a
gate threaded on
the inside.
Used in areas,
where not much
overhead
clearance exists.
12
Valves,Types and Operations
NRS Gate Valve
The part of the stem that passes through the bonnet has a flange on it, due to which the stem cannot move up or down; instead engages the gate on turning wheel and pulls it up or down and vice versa.
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Valves,Types and Operations
Types of Gate
Solid wedge gate
Parallel disc gate and
Solid split gate
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Valves,Types and Operations
Solid Wedge Gate Made of one part and
bears pressure of the flow on one side only.
Complete shut off is accomplished through a close fit between gate and seat rings.
On lowering or raising of gate there is more friction between gate and seat rings which tends to wear out one seat rings quicker (against the side of flow).
15
Valves,Types and Operations
Parallel Disc Gate Made out of many parts.
When lower wedge or spreader reaches the stop, it forces the upper spreader to the lower one.
This pushes the discs outward against the seat rings and ensures a very tight closing.
Although one side of disc is more worn but tight closing produced by the wedging action, it still allows complete shutoff.
16
Valves,Types and Operations
Parallel Disc Gate
The discs are attached to the spreader in such a way that they rotate when the gate is raised or lowered, this causes an even wear.
As the upper wedge is raised, it releases the wedging pressure and disc become freer.
17
Valves,Types and Operations
Parallel Disc Gate
On high temperatures,
pipe expansions can
wrap the body of the
valve, causing extreme
pressure on the gate.
These gates are not used
with material with coarse
particles and in vertical
positions.
18
Valves,Types and Operations
Solid Split Gate
A solid split gate is made of one piece,
with flexible outer edges. These edges
bear pressure on the gate when a valve
body wraps up.
19
Valves,Types and Operations
Gate Valve Malfunction Gate valves malfunction due to erosion of
gate or seat rings which makes tight closure difficult.
This happens due to the friction between gate and seat rings on rising or dropping the gate very often.
It could be avoided by using gate valves in pipes who are not much disturbed during normal operation i.e. are completely open or completely closed.
20
Valves,Types and Operations
Globe Valve
21 Valves,Types and Operations
Globe Valve The line of flow changes
its direction, which creates higher pressure drop and turbulence.
Seat rings are parallel to the line of flow and stem guides the disc into the seating. Opening is controlled by a disc.
Flow starts as soon as the contact of disc and seat is broken.
22
Valves,Types and Operations
Globe Valve Very little wear due to
friction and even wear; however partial opening of valve exposes all parts of disc to flow.
Even wear permits complete closure even after long use.
Flow from under the disc creates less turbulence than flow from the disc.
23
Valves,Types and Operations
See Animation
Globe Valve
Globe valves are also
installed on turnings,
called Angle Globe
Valves.
Flow through angle
valve has fewer
changes of direction
and therefore is less
turbulent.
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Valves,Types and Operations
Types of Disc
Three types of disc are used in globe
valves:
Plug disc
Composition disc and
Conventional disc
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Valves,Types and Operations
Plug Disc
Cone shaped
Used for heavy
throttling service
Continues to give
positive shut off even
after some wear
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Valves,Types and Operations
Composition Disc Made of softer materials.
When completely closed, seat ring can make a contact with the soft part of disc.
Fine particles in flow often accumulated on seats or discs can be embedded on the soft part of the disc ensuring a tight closure.
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Valves,Types and Operations
Conventional Disc
Smaller disc-to-seat
area than plug discs.
Can crush small
particles more easily
but if nicked or worn,
tight closure is not
possible with them.
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Valves,Types and Operations
Plug Valve
29 Valves,Types and Operations
Plug Valve Controls the opening
through a hollow plug, which is turned/rotated and aligned with the pipe to permit a straight line of flow.
Plug is turned a quarter turn, to stop the flow.
The valve can be opened or closed more quickly than previous examples and produce little turbulence and pressure drop
30
Valves,Types and Operations
Plug Valve Friction develops between
the body and the plug, which wears the plug giving it a loose fit.
The shank of the plug has a lubricant fitting that makes it possible to apply special lubricant to the plug itself. Lubrication is done often to reduce friction and also prevent leakage.
31
Valves,Types and Operations
Ball Valve
32 Valves,Types and Operations
Ball Valve Good shut-off
capabilities.
Quarter-turn (90°) completely opens or closes the valve.
Minimal valve operation time and decreases the likelihood of leakage due to wear from the gland seal.
33
Valves,Types and Operations
See Animation
Ball Valve
Ball valves can be divided into two
categories:
Reduced bore: valve opening is smaller
than the diameter of the piping
Full bore: valve opening is the same size as
the diameter of the piping.
valued because they minimize the pressure
drop across the valve.
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Valves,Types and Operations
Ball Valve Recommended for use in the fully open or
fully closed position.
Not suited to regulate flow by being kept partially open because ball valves make use of a ring-shaped soft valve seat.
When used in the partially open position, pressure is applied to only a portion of the valve seat, which can cause it to deform.
If deforms, its sealing properties are impaired and will leak as a result.
35
Valves,Types and Operations
Diaphragm
Valve
36 Valves,Types and Operations
Diaphragm Valve ‘Pinching' method to stop the
valve flow using a flexible diaphragm.
Available in two types:
Weir and
Straight-way
The most common is the weir-type because the straight-way type requires additional stretching, which can shorten the diaphragm's life-span.
37
Valves,Types and Operations
See Animation
Diaphragm Valve Advantages:
Valve components can be isolated from the process fluid.
Construction helps prevent leakage of the fluid without the use of a gland seal (packing)
Disadvantages:
Diaphragm becomes worn more easily
Regular maintenance is necessary
Not suited for very high temperature fluids
Mainly used on liquid systems.
38
Valves,Types and Operations
Check Valve
39 Valves,Types and Operations
Check Valve Ensure that flow goes in
desired direction and does not reverses.
Valve is automatically opened by the flow pressure and is closed when the pressure falls.
It allows flow from one side only, and on reverse flow, disc gets closed restricting flow.
40
Valves,Types and Operations
Lift Check Valve Similar to globe valve
structure, with flow raising the disc and gravity pulling it down.
Direction of flow is always kept from under the disc to minimize turbulence.
It works in both horizontal and vertical positions, but with slight structural modifications.
41
Valves,Types and Operations
Ball Check Valve
A check valve with
flow not in a straight
line.
Similar to lift check
valve with the disk
replaced with a ball.
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Valves,Types and Operations
Operations
43 Valves,Types and Operations
Operations
Accumulation of Sludge/ Fouling
Incomplete shut off / opening
Remedy:
Addition of Anti fouling sludge
Dismantling of Valve
44
Valves,Types and Operations
Operations
Stem Breakage
Replacement of Valve
Else Raising the Stem
By using a Jack Screw
By using over had hoist
45
Valves,Types and Operations
Operations
Raising the Broken Stem by
using a Jack Screw
46
Valves,Types and Operations
Operations
Raising the Broken Stem by
using an Overhead Hoist
47
Valves,Types and Operations
Operations
Packing Leakage
Opening the valve to max. limit
Achieving Back-Seating
Dangerous and only opted in emergency
48
Valves,Types and Operations
Operations
Gaskets Leakage
49
Valves,Types and Operations
Thank You
Prepared by Osama Hasan School of Chemical and Materials Engineering (SCME)
National University of Sciences and Technology (NUST)
osama_hasan@hotmail.com
Valves,Types and Operations
50
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