Pressure adakala tidak mudah difahami dari aspek praktical bagi kebanyakan jurutera . Dalam sistem Piping . ia lebih mudah dipandang dari segi Halangan atau"resistance " .Bermakna . piping yang lebih kecil mempunyai halangan(resistance ) yang lebih tinggi iaitu dikenali sebagai ' " higher head loss in piping "
Pressure dalam Pumping , biasa di kenali sebagai " Head "
1 bar =10 M head atau 14,5 psi
Pressure Tidak Mencukupi
Sebelum membuat keputusan untuk mendapatkan pam baru ,kerana pam yang sedia ada tidak dapat memberi pressure yang perlu , apakah sebab sebabnya?
A) WEAR AND TEAR
B ) ATAU SYSTEM PRESSURE TERLALU TINGGI
C) ATAU PAM DI BELI,TIDAK MEMENUH SPECIFIKASI
D) ATAU SYSTEM PROBLEm
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30.7.08
Treated Effluent Pumping -Land Disposal
Dear Oil Mill Users
Generally this application can be about 60 to 100 m3/hr pumping rate
And pressure will depend on piping distance
If the distance is short , open impeller centrifugal pumps can be used
However is the distance is 1.5 Kilometer .you may need a Two Stage Screw Pump to do the job with operating pressure of about 8 to 10 bar ,depending on the pipe diameter
Again ,I wish to highlight the importance of designing an optimum pipe diameter
A smaller diameter would mean higher operating pressure and on the other hand too big a diameter will incur higher capital cost
Work out cost of pipes over operating cost in term of power cost
Pipes are buried underground and Polypipe are being used .
If pressure is too high ,then breakages are likely to occur often and it is goiung to be very
difficult to trace the leakage
Go for as low as posiible the operating head to minimise this problem
PolyPipe is rated 10 bar and joints may be weak .When there is blockage along the pipe . a two stage pump can develop a pressure of 12 to 15 bar and hence . pipe or joints may burst
Suggest instal a pressure switch which cut off pump when the pressure exceed the limit
to protect the system
Also choose a right pressure switch .Diaphragm seal type designed for cleaning
Generally this application can be about 60 to 100 m3/hr pumping rate
And pressure will depend on piping distance
If the distance is short , open impeller centrifugal pumps can be used
However is the distance is 1.5 Kilometer .you may need a Two Stage Screw Pump to do the job with operating pressure of about 8 to 10 bar ,depending on the pipe diameter
Again ,I wish to highlight the importance of designing an optimum pipe diameter
A smaller diameter would mean higher operating pressure and on the other hand too big a diameter will incur higher capital cost
Work out cost of pipes over operating cost in term of power cost
Pipes are buried underground and Polypipe are being used .
If pressure is too high ,then breakages are likely to occur often and it is goiung to be very
difficult to trace the leakage
Go for as low as posiible the operating head to minimise this problem
PolyPipe is rated 10 bar and joints may be weak .When there is blockage along the pipe . a two stage pump can develop a pressure of 12 to 15 bar and hence . pipe or joints may burst
Suggest instal a pressure switch which cut off pump when the pressure exceed the limit
to protect the system
Also choose a right pressure switch .Diaphragm seal type designed for cleaning
25.7.08
SLUDGE DESANDING BOOSTER FEED PUMP (PALM OIL MILL)
Dear Azhar
The sludge oil to the desanding system contains high amount of sand /dirt which causes the excessive wear and tear on the pump
You are operating at 3 bar pressure and the existing pump will need about 1600 rpm which is a bit high
to do the job
Ideally ,select a pump at can operate at about 1000 rpm
Material can be Nihard or rubber lined pumps
The system pressure is 3 bar ,the OEM or Supplier of the Equipemet or system could have design the system to
be about 1.5 bar , and this simplify the operation
Initially there was some problem during commissioning stage ,but it was not the pump problem
as reported
a) complaint from mill that if valve is fully opened the Overload Relay tripped
we checked and found that the Ampheres setting was too low .therefore trip
as valve opened fully, the BHP increased .The motor rating is more than sufficient and it is fuuny that
electrical chargeman did not reliase this and ampheres of overload not set correctly
b) when valve is not fully openned .the flow was reduced at feed inlet to Desander .and hence the pressure
of only 1.7 bar
Pressure = Quantity / Area
How to determine if it is pump problem or system problem
Very often ,Engineer's mindset is that .
" NOT PERFORMING .MUST BE THE PUMP SUPPLIER PROBLEM OR OR PUMP NO GOOD "
a) First check the pump condition . If the pump condition is in order ,next
You can do a shut off Test on the pump .if pressure can be achieved at shut off ,then you can
confirm that the pumps 100 % ok
b) Check pump performance curve .see if rating done correctly for pump installed
Example ,for this duty
capacity : 20 m3/hr at 30 M head
pump Model :OB 1 1/4
pump Speed : 1800 rpm
If this is in order ,than move on the system
a) checked inlet . for any obstruction by sand /dirt accumulated at tank bottom or inlet line
b) Checked motor maximum Amps and setting amps ( your initial setting was 18.4 amps for 11 kw motor , Star Delta connection , it was later set to 22 amps )
Job Done
The overload relay resetted and valve can be fully open .pressure achieved and running in
required parameter
The problem now is high wear & tear , suggest resize a pump to operate at lower rpm and material compatible to this operation
Another pump OB 1 1/4 -33 , can operate same duty point at 1200 rpm , lower speed and hence lower
wear and tear
The sludge oil to the desanding system contains high amount of sand /dirt which causes the excessive wear and tear on the pump
You are operating at 3 bar pressure and the existing pump will need about 1600 rpm which is a bit high
to do the job
Ideally ,select a pump at can operate at about 1000 rpm
Material can be Nihard or rubber lined pumps
The system pressure is 3 bar ,the OEM or Supplier of the Equipemet or system could have design the system to
be about 1.5 bar , and this simplify the operation
Initially there was some problem during commissioning stage ,but it was not the pump problem
as reported
a) complaint from mill that if valve is fully opened the Overload Relay tripped
we checked and found that the Ampheres setting was too low .therefore trip
as valve opened fully, the BHP increased .The motor rating is more than sufficient and it is fuuny that
electrical chargeman did not reliase this and ampheres of overload not set correctly
b) when valve is not fully openned .the flow was reduced at feed inlet to Desander .and hence the pressure
of only 1.7 bar
Pressure = Quantity / Area
How to determine if it is pump problem or system problem
Very often ,Engineer's mindset is that .
" NOT PERFORMING .MUST BE THE PUMP SUPPLIER PROBLEM OR OR PUMP NO GOOD "
a) First check the pump condition . If the pump condition is in order ,next
You can do a shut off Test on the pump .if pressure can be achieved at shut off ,then you can
confirm that the pumps 100 % ok
b) Check pump performance curve .see if rating done correctly for pump installed
Example ,for this duty
capacity : 20 m3/hr at 30 M head
pump Model :OB 1 1/4
pump Speed : 1800 rpm
If this is in order ,than move on the system
a) checked inlet . for any obstruction by sand /dirt accumulated at tank bottom or inlet line
b) Checked motor maximum Amps and setting amps ( your initial setting was 18.4 amps for 11 kw motor , Star Delta connection , it was later set to 22 amps )
Job Done
The overload relay resetted and valve can be fully open .pressure achieved and running in
required parameter
The problem now is high wear & tear , suggest resize a pump to operate at lower rpm and material compatible to this operation
Another pump OB 1 1/4 -33 , can operate same duty point at 1200 rpm , lower speed and hence lower
wear and tear
10.7.08
Liquid Ring Vacuum Pump -Cavitation and Excessive Water
CAVITATION
How to Observe
When the pump cavitate ,pump will prme a rattllig noise and in worst case the pump also vibrates
On visual inspection . you will see pittings on the impeller in between the blades and edge of blades .The finger valve will also get pitted and broken
CAUSES
Usually is cuased by
1) big amont of steam being sucked in from the process
2) too high temperature of sucked gas and/or service liquid
3) too high vacuum at suction
4) service liquid with vapour pressure ( eg mixture of solvent)
Remedy
Anti cavitation valve is a good preventive measure ,but it is not a solution when the
cavitation is serious and continous, other alternative could be looked into
One of which if the Guage reading is showing about 35 m bar and below . see if can operate at lower vacuum
EXCESS OF WATER
You will notice cases of impeller blades bent or broken
Causes
1) Water is not drained when the pump stopped .the pump will start with too much water
in the pump(instal an automatic drained valve )
2) too much pressure or head of service liquid feeding(instal regulating valve for this purpose )
3) too much water or condensable steam being sucked from the process
Typical problem , for pumps used in drying process without good condensor /separator
between the pump and the process
In one soap noodle plant, the condenser is feeded water from the cooling tower
.At the water discharge area ,choked by dirt from the water system and the water
flooded the nozzle at vacuum suction line .Big amount of water is being drawn to the vacuum line
How to Observe
When the pump cavitate ,pump will prme a rattllig noise and in worst case the pump also vibrates
On visual inspection . you will see pittings on the impeller in between the blades and edge of blades .The finger valve will also get pitted and broken
CAUSES
Usually is cuased by
1) big amont of steam being sucked in from the process
2) too high temperature of sucked gas and/or service liquid
3) too high vacuum at suction
4) service liquid with vapour pressure ( eg mixture of solvent)
Remedy
Anti cavitation valve is a good preventive measure ,but it is not a solution when the
cavitation is serious and continous, other alternative could be looked into
One of which if the Guage reading is showing about 35 m bar and below . see if can operate at lower vacuum
EXCESS OF WATER
You will notice cases of impeller blades bent or broken
Causes
1) Water is not drained when the pump stopped .the pump will start with too much water
in the pump(instal an automatic drained valve )
2) too much pressure or head of service liquid feeding(instal regulating valve for this purpose )
3) too much water or condensable steam being sucked from the process
Typical problem , for pumps used in drying process without good condensor /separator
between the pump and the process
In one soap noodle plant, the condenser is feeded water from the cooling tower
.At the water discharge area ,choked by dirt from the water system and the water
flooded the nozzle at vacuum suction line .Big amount of water is being drawn to the vacuum line
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