It is a simple question with complex answer. Firstly we must know basic data: Total Discharge Head (TDH), Nett Pressure Suction Head Available (NPSHA), flowrate required, composition of fluid to be pumped, environment where pump to be istalled, source of power, operation mode, available budget, and reliability required.
Then you might need additional data and guidance to select pump for example API 610 (Centrifugal pump). Or you can read in Pump Handbook by Igor J. Karassik. Also, you might need best practice data, historical data, MTBF, and input from maintenance and operation people.
Thank you very much.
Regards,
eira
I would be happy if there is any comment or questions.
Tampilkan postingan dengan label PUMP. Tampilkan semua postingan
Tampilkan postingan dengan label PUMP. Tampilkan semua postingan
Sabtu, 26 Juli 2008
Jumat, 07 Maret 2008
Bagaimana Cara Menghitung Power Output Gas Turbin di Lapangan?
Yg sering pake ngeliat kurva performance. Lebih enak euy..
Kalau pake ngitung ribet.
1. Bisa pake hitung dari torque meter (T):
POWER = 2 X pi x N x T
2. ngitung termodinamika. Utk open cycle:
Work aktual kompresor = entalpi spesifik di titik keluar kompresor – entalpi spesifik di inlet kompresor
Work aktual turbin = [1+(laju aliran massa fuel/laju aliran massa udara)] x (entalpi spesifik sebelum masuk turbin – entalpi spesifik setelah keluar turbin)
Kerja net shaft turbin = work aktual turbin – work aktual kompressor
Power output = laju aliran massa aktual x kerja net turbin shaft
Ente tinggal mengkonversi data-data PCD, Tinlet compressor, T emp PCD, TRIT, Texhast, inlet air pressure, fuel flow, fuel heating value, S.G fuel, ambient temperature ke entalpi dan mass flowrate.
Cuma kalo mau ngukur-ngukur harus ada limit max fluktuasi datanya (lihat PTC-10)
3. derating dari data nameplate.
Power available at site = ISO rated HP x altitude correction factor x inlet loss correction factor x exhaust loss correction factor x ambient temperature correction factor
4. Hitung mundur dari power yg di drive, misalnya pompa, kW yg dibangkitkan, gas yang dikompres, dll. Cuma musti hati-hati dalam menentukan efisiensi gearbox, kopling, isentropic efisiensi, efisiensi pompa, efisiensi alternator, ataupun efisiensi pentransmisian daya lainnya.
trims.
Kalau pake ngitung ribet.
1. Bisa pake hitung dari torque meter (T):
POWER = 2 X pi x N x T
2. ngitung termodinamika. Utk open cycle:
Work aktual kompresor = entalpi spesifik di titik keluar kompresor – entalpi spesifik di inlet kompresor
Work aktual turbin = [1+(laju aliran massa fuel/laju aliran massa udara)] x (entalpi spesifik sebelum masuk turbin – entalpi spesifik setelah keluar turbin)
Kerja net shaft turbin = work aktual turbin – work aktual kompressor
Power output = laju aliran massa aktual x kerja net turbin shaft
Ente tinggal mengkonversi data-data PCD, Tinlet compressor, T emp PCD, TRIT, Texhast, inlet air pressure, fuel flow, fuel heating value, S.G fuel, ambient temperature ke entalpi dan mass flowrate.
Cuma kalo mau ngukur-ngukur harus ada limit max fluktuasi datanya (lihat PTC-10)
3. derating dari data nameplate.
Power available at site = ISO rated HP x altitude correction factor x inlet loss correction factor x exhaust loss correction factor x ambient temperature correction factor
4. Hitung mundur dari power yg di drive, misalnya pompa, kW yg dibangkitkan, gas yang dikompres, dll. Cuma musti hati-hati dalam menentukan efisiensi gearbox, kopling, isentropic efisiensi, efisiensi pompa, efisiensi alternator, ataupun efisiensi pentransmisian daya lainnya.
trims.
Rabu, 05 Maret 2008
Pump Prime Chamber
Mancing pompa.
Kita tentu sudah sering mendengar dan mungkin melakukan mancing pompa. Mancing pompa adalah memasukkan sejumlah cairan (kalau pompa air maka cairannya ya air) ke dalam rumah pompa agar pompanya bisa menyedot dan mengalikan liquid yang posisi elevasinya berada di bawah (static lift) centerline suction flange pompa. Umumnya pompa yang dipancing adalah tipe pompa sentrifugal horisontal single stage.
Mengapa pompa perlu dipancing?
Jawab singkatnya = Agar bisa mompa. Pompa sentrifugal memakai prinsip mengubah energi kinetik menjadi energi potensial. Aliran fluida dinaikkan pressurenya di daerah volute impeller. Impeller harus berputar, agar tidak terjadi rubbing dan putaran impeller tidak terganggu maka antara impeller (rotor) dengan stator harus ada celah (clearance). Karena adanya clearance/celah ini maka putaran impeller tidak akan cukup kuat membuat tekanan vacuum sampai ke permukaan cairan yang ada di bawah/mulut pipa suction. Nah, di sinilah letak pentingnya caian liquid yang ada dalam prime chamber (beberapa manufacturer membuat casing pompa agak besar dan dinamakan selfpriming pump). Liquid itu akan membentuk lapisan/barrier kedap pembatas antara udara di sisi discharge pompa dengan udara yang ada antara liquid dalam chamber dengan liquid yang ada di bawah, di reservoir. Liquid ini akan memenuhi ruang celah clearance di antara impeller dan stator. Pada saat impeller berputar, kolom liquid ini bergerak terdorong/terpompa ke arah discharge, maka kolom udara yang terperangkap antara kolom liquid prime chamber dengan kolom di pipa suction akan ikut terbawa ke pipa discharge. Sebagian priming liquid akan kembali ke priming chamber tetapi udara tidak akan kembali ke dalam pipa suction. Akan terbentuk vacuum di dalam pipa suction tadi. Proses pembuangan udara dari dalam pipa suction ini akan berlangsung terus hingga liquid yg ada di bawah akan naik semuanya (pipa suction dipenuhi liquid). Tekanan vacuum inilah yang akan mendorong liquid yang ada di bawah untuk naik ke mulut (suction flange) pompa.
Ada 2 macam priming chamber, ada yang priming liquidnya tinggal di dalam casing pompa (disebut self priming pump), dan yang priming liquidnya terpisah dalam suatu accessories priming chamber.
Hal-hal yang harus dilakukan pada priming chamber:
1. priming chamber harus dalam keadaan bersih (tidak penuh lumpur atau pasir atau bocor) sehingga priming liquid selalu tersedia cukup. Suction strainer harus rutin dicek.
2. Static lift atau suction line jangan terlalu panjang sehingga priming timenya tidak terlalu lama yang dapat mengakibatkan priming liquid vaporized, menguap dan pompa menjadi panas, sebelum liquid di suction line sempat terangkat.
3. Suction line haus bebas dari kebocoran/kedap udara.
4. Harus tersedia priming bypass line agar tidak terjadi backpressure yang sampai dapat menyebabkan pompa menjadi kompresor angin hehe….
5. Tidak boleh ada lekukan atau elbow pada suction line yang dapat menyebabkan udara terperangkap.
Kita tentu sudah sering mendengar dan mungkin melakukan mancing pompa. Mancing pompa adalah memasukkan sejumlah cairan (kalau pompa air maka cairannya ya air) ke dalam rumah pompa agar pompanya bisa menyedot dan mengalikan liquid yang posisi elevasinya berada di bawah (static lift) centerline suction flange pompa. Umumnya pompa yang dipancing adalah tipe pompa sentrifugal horisontal single stage.
Mengapa pompa perlu dipancing?
Jawab singkatnya = Agar bisa mompa. Pompa sentrifugal memakai prinsip mengubah energi kinetik menjadi energi potensial. Aliran fluida dinaikkan pressurenya di daerah volute impeller. Impeller harus berputar, agar tidak terjadi rubbing dan putaran impeller tidak terganggu maka antara impeller (rotor) dengan stator harus ada celah (clearance). Karena adanya clearance/celah ini maka putaran impeller tidak akan cukup kuat membuat tekanan vacuum sampai ke permukaan cairan yang ada di bawah/mulut pipa suction. Nah, di sinilah letak pentingnya caian liquid yang ada dalam prime chamber (beberapa manufacturer membuat casing pompa agak besar dan dinamakan selfpriming pump). Liquid itu akan membentuk lapisan/barrier kedap pembatas antara udara di sisi discharge pompa dengan udara yang ada antara liquid dalam chamber dengan liquid yang ada di bawah, di reservoir. Liquid ini akan memenuhi ruang celah clearance di antara impeller dan stator. Pada saat impeller berputar, kolom liquid ini bergerak terdorong/terpompa ke arah discharge, maka kolom udara yang terperangkap antara kolom liquid prime chamber dengan kolom di pipa suction akan ikut terbawa ke pipa discharge. Sebagian priming liquid akan kembali ke priming chamber tetapi udara tidak akan kembali ke dalam pipa suction. Akan terbentuk vacuum di dalam pipa suction tadi. Proses pembuangan udara dari dalam pipa suction ini akan berlangsung terus hingga liquid yg ada di bawah akan naik semuanya (pipa suction dipenuhi liquid). Tekanan vacuum inilah yang akan mendorong liquid yang ada di bawah untuk naik ke mulut (suction flange) pompa.
Ada 2 macam priming chamber, ada yang priming liquidnya tinggal di dalam casing pompa (disebut self priming pump), dan yang priming liquidnya terpisah dalam suatu accessories priming chamber.
Hal-hal yang harus dilakukan pada priming chamber:
1. priming chamber harus dalam keadaan bersih (tidak penuh lumpur atau pasir atau bocor) sehingga priming liquid selalu tersedia cukup. Suction strainer harus rutin dicek.
2. Static lift atau suction line jangan terlalu panjang sehingga priming timenya tidak terlalu lama yang dapat mengakibatkan priming liquid vaporized, menguap dan pompa menjadi panas, sebelum liquid di suction line sempat terangkat.
3. Suction line haus bebas dari kebocoran/kedap udara.
4. Harus tersedia priming bypass line agar tidak terjadi backpressure yang sampai dapat menyebabkan pompa menjadi kompresor angin hehe….
5. Tidak boleh ada lekukan atau elbow pada suction line yang dapat menyebabkan udara terperangkap.
Kamis, 17 Januari 2008
Perbedaan ANSI Pump dengan API Pump
During design phase of pumping system, operation, and maintenance trouble shooting we must know which pump is most suited with our requirements. This article try to explain the differences between API pump and ANSI pump. Below is a table that summarize pumps general feature comparison.
Below are some pump differences more explanation.
The API design in Figure 4 bolts the back cover directly to the casing and uses a confined controlled compression gasket with metal to metal fits. The adaptor is bolted independently to the back cover and does not play a part in the pressure boundary of the pump casing.
Mounting Feet & Bearing Housing
Another difference between the two pump styles is the configuration of the mounting feet. All ANSI pump casings are mounted on feet projecting from the underside of the casing and bolted to the baseplate. If these pumps are used on high-temperature applications, the casing will expand upwards from the mounting feet and cause severe thermal stresses in the casing that will detrimentally affect the reliability of the pump. Operation at lower temperatures will not be affected by this feature. On the other hand, API pumps are mounted at the horizontal centerline of the casing on feet projecting from each side of the casing and bolted to pedestals that form part of the baseplate. This arrangement provides the API pump with the advantage of being able to operate with pumpage at elevated temperatures. As the pump comes up to temperature in such cases, any expansion of the metal will be above and below the casing centerline, and will exert minimal amounts of stress to the casing, thus contributing to optimum reliability of the
pump. The ability to handle higher temperature services is also evident in the bearing housings of the API pumps, which tend to be much more robust in design and also accommodate cooling jackets with a greater capacity of cooling water.
Materials of Construction
Pump manufacturers can provide ANSI and API pumps in a wide assortment of materials, the selection of which depends on the operating stress and effects, as well as the type of wear from the product being pumped. The most common materials used in these centrifugal pumps are:
��������� Cast iron
��������� Ductile iron
��������� Bronze
��������� Carbon and low alloy steels such as 4140
��������� Chrome steels such as 11%, 12% or 13%
��������� Martenistic stainless steels: the 400 series
��������� Precipitation hardening stainless steels: 17-4 PH
��������� Austenitic stainless steels: the 300 series or alloy 20
��������� Duplex stainless steels: CD4MCu
��������� exotic alloys: Hastelloy, Titanium, dll.
Repair Considerations
It is important to remember, before any repair procedures are performed on any pump component, that the material of construction must be accurately identified by means of the appropriate tests. Prior to any repairs being conducted on a pump casing, it is also
advisable to consider the economic advantage of the repair under consideration. Smaller and medium-sized ANSI pumps are designed with a high degree of interchangeability
and produced in volume. Consequently, it can frequently be more cost effective to replace the entire pump rather than a combination of the impeller, casing and back cover. In addition, both the individual parts and complete pumps are available fairly quickly. This can make it more cost effective to replace rather than repair the parts, unless the wet
ends are made of the more exotic alloys. It is clear, in the case of non-metallic pumps (which may also conform to ANSI standards), that the components must be replaced, as they generally cannot be repaired. API pumps, however, are generally more economical to repair than to replace. These units are usually installed in more rugged duties and hazardous applications in refineries or other petrochemical industries, and are consequently more durable and more expensive. Delivery periods are also frequently longer, and the parts more costly than their ANSI equivalents���������particularly the cases and impellers.
This makes it very tempting to source these parts from an after-market supplier rather than the Original Equipment Manufacturer (OEM). It should be noted, though, that the major parts of a centrifugal pump (i.e. the casing, the impeller and the back cover) are all cast from patterns involving intricate hydraulic designs, which are of a proprietary nature. These parts are also the ones that provide the hydraulic performance of the pump. While the parts might be available from after-market suppliers at slightly lower prices than they are from the OEM, that cost saving will fade into insignificance if the pump does not meet its hydraulic performance. Your OEM can accept the responsibility for thesubsequent hydraulic performance of these replacement parts.
Price
API pumps is more expensive than ANSI pump.
CONCLUSION
So, Let���������s Stay Focused and Practical. Pump selection is not a beauty contest���������ANSI and API are not brands to be ���������preferred.��������� Instead, it���������s up to the system designer and equipment supplier to cooperate as much as possible to ensure that the best possible and most reliable pump selection ensues.
Trims
Below are some pump differences more explanation.Pump Rating
ANSI Pump Rating = 300 PSIG at 300������ F
API Pump Rating = 750 PSIG at 500������ F
Volute Cases & Suction/Discharge Flanges
Both pump styles have a radial split casing, and most ANSI pumps and some API pumps employ a single volute design of the interior passages. This is particularly evident in the smaller sizes that involve low-flow rates and lower specific speeds of the impeller. As shown in Figure 1, the area of the volute increases at a rate that is proportional to the rate of discharge from the impeller, thus producing a constant velocity at the periphery of the impeller. This velocity energy is then changed into a pressure energy by the time the fluid enters the discharge nozzle. Most of the larger API pumps are produced with a double volute design to reduce these loads on high-flow and high-head units.
The top suction/top discharge arrangement, which has also been used in a slightly different configuration in a vertical inline pump design. In this arrangement with a horizontal pump, the suction nozzle is located at the top of the casing adjacent to the discharge nozzle, rather than on the end. On the vertical inline design, the suction nozzle is once again on the side, but now it is opposite to the discharge nozzle, thus creating the ���������inline��������� appearance. The drawback of this design is, for most of these pumps, that the NPSH required is often considerably greater than it would be in the end suction arrangement. More NPSH is needed in order to accommodate the friction losses in the tortuous path from the suction flange to the eye of the impeller.
ANSI Pump Rating = 300 PSIG at 300������ F
API Pump Rating = 750 PSIG at 500������ F
Volute Cases & Suction/Discharge Flanges
Both pump styles have a radial split casing, and most ANSI pumps and some API pumps employ a single volute design of the interior passages. This is particularly evident in the smaller sizes that involve low-flow rates and lower specific speeds of the impeller. As shown in Figure 1, the area of the volute increases at a rate that is proportional to the rate of discharge from the impeller, thus producing a constant velocity at the periphery of the impeller. This velocity energy is then changed into a pressure energy by the time the fluid enters the discharge nozzle. Most of the larger API pumps are produced with a double volute design to reduce these loads on high-flow and high-head units.
The top suction/top discharge arrangement, which has also been used in a slightly different configuration in a vertical inline pump design. In this arrangement with a horizontal pump, the suction nozzle is located at the top of the casing adjacent to the discharge nozzle, rather than on the end. On the vertical inline design, the suction nozzle is once again on the side, but now it is opposite to the discharge nozzle, thus creating the ���������inline��������� appearance. The drawback of this design is, for most of these pumps, that the NPSH required is often considerably greater than it would be in the end suction arrangement. More NPSH is needed in order to accommodate the friction losses in the tortuous path from the suction flange to the eye of the impeller.
Back Cover Arrangements
One of the major differences between the ANSI and API pump casings is in the manner in which the back cover is secured to the casing. In the ANSI design shown in Figure 3, the back cover and gasket are held against the pump casing by the bearing frame adaptor, which is most frequently supplied in cast iron. This usually results in a gap between the mating faces of the frame adaptor and the pump casing that has the potential to permit uneven torquing of the bolts. In the event of a higher-than-normal pressurization of the casing by the process system, this may cause a fracture of the adaptor.
One of the major differences between the ANSI and API pump casings is in the manner in which the back cover is secured to the casing. In the ANSI design shown in Figure 3, the back cover and gasket are held against the pump casing by the bearing frame adaptor, which is most frequently supplied in cast iron. This usually results in a gap between the mating faces of the frame adaptor and the pump casing that has the potential to permit uneven torquing of the bolts. In the event of a higher-than-normal pressurization of the casing by the process system, this may cause a fracture of the adaptor.
The API design in Figure 4 bolts the back cover directly to the casing and uses a confined controlled compression gasket with metal to metal fits. The adaptor is bolted independently to the back cover and does not play a part in the pressure boundary of the pump casing.
Mounting Feet & Bearing Housing
Another difference between the two pump styles is the configuration of the mounting feet. All ANSI pump casings are mounted on feet projecting from the underside of the casing and bolted to the baseplate. If these pumps are used on high-temperature applications, the casing will expand upwards from the mounting feet and cause severe thermal stresses in the casing that will detrimentally affect the reliability of the pump. Operation at lower temperatures will not be affected by this feature. On the other hand, API pumps are mounted at the horizontal centerline of the casing on feet projecting from each side of the casing and bolted to pedestals that form part of the baseplate. This arrangement provides the API pump with the advantage of being able to operate with pumpage at elevated temperatures. As the pump comes up to temperature in such cases, any expansion of the metal will be above and below the casing centerline, and will exert minimal amounts of stress to the casing, thus contributing to optimum reliability of the
pump. The ability to handle higher temperature services is also evident in the bearing housings of the API pumps, which tend to be much more robust in design and also accommodate cooling jackets with a greater capacity of cooling water.
Materials of Construction
Pump manufacturers can provide ANSI and API pumps in a wide assortment of materials, the selection of which depends on the operating stress and effects, as well as the type of wear from the product being pumped. The most common materials used in these centrifugal pumps are:
��������� Cast iron
��������� Ductile iron
��������� Bronze
��������� Carbon and low alloy steels such as 4140
��������� Chrome steels such as 11%, 12% or 13%
��������� Martenistic stainless steels: the 400 series
��������� Precipitation hardening stainless steels: 17-4 PH
��������� Austenitic stainless steels: the 300 series or alloy 20
��������� Duplex stainless steels: CD4MCu
��������� exotic alloys: Hastelloy, Titanium, dll.
Repair Considerations
It is important to remember, before any repair procedures are performed on any pump component, that the material of construction must be accurately identified by means of the appropriate tests. Prior to any repairs being conducted on a pump casing, it is also
advisable to consider the economic advantage of the repair under consideration. Smaller and medium-sized ANSI pumps are designed with a high degree of interchangeability
and produced in volume. Consequently, it can frequently be more cost effective to replace the entire pump rather than a combination of the impeller, casing and back cover. In addition, both the individual parts and complete pumps are available fairly quickly. This can make it more cost effective to replace rather than repair the parts, unless the wet
ends are made of the more exotic alloys. It is clear, in the case of non-metallic pumps (which may also conform to ANSI standards), that the components must be replaced, as they generally cannot be repaired. API pumps, however, are generally more economical to repair than to replace. These units are usually installed in more rugged duties and hazardous applications in refineries or other petrochemical industries, and are consequently more durable and more expensive. Delivery periods are also frequently longer, and the parts more costly than their ANSI equivalents���������particularly the cases and impellers.
This makes it very tempting to source these parts from an after-market supplier rather than the Original Equipment Manufacturer (OEM). It should be noted, though, that the major parts of a centrifugal pump (i.e. the casing, the impeller and the back cover) are all cast from patterns involving intricate hydraulic designs, which are of a proprietary nature. These parts are also the ones that provide the hydraulic performance of the pump. While the parts might be available from after-market suppliers at slightly lower prices than they are from the OEM, that cost saving will fade into insignificance if the pump does not meet its hydraulic performance. Your OEM can accept the responsibility for thesubsequent hydraulic performance of these replacement parts.
Price
API pumps is more expensive than ANSI pump.
CONCLUSION
So, Let���������s Stay Focused and Practical. Pump selection is not a beauty contest���������ANSI and API are not brands to be ���������preferred.��������� Instead, it���������s up to the system designer and equipment supplier to cooperate as much as possible to ensure that the best possible and most reliable pump selection ensues.
Trims
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