How to Select a Pump?

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.

Case Histories: PT Vibration and T5 Topping

There is a gas turbine just come from general overhaul, RH ~ 0 hour.
Its power turbine exhibit high vibration at 1xRPM, and phase can not differentiate between unbalance or misalignment. Axial vibration relatively small.
Alignment recheck, field balancing, and rotate coupling hub had been done to solve the problem, but not solved the problem. NGP was still 94%-95%, with PT Vibration 0.4 ips pk.

Another clue was get. The vibration increase after after engine had run for some time, e.q: 2-4 hours. So it is suspected related to thermal growth problem, so: alignment. After check alignment target specification there was misunderstanding between field maintenance people, they used old standard before the centrifugal booster compressor restaged. So after the alignment redone with new alignment specification target, the PT Vibration run low, NGP can be increased.

But, unfortunately, at NGP 99%, T5 topping appeared. PCD at TCP was about 118 psig, PCD at dial gage at panel was about 123 psig. Inlet air filter dp was 2.0" WC. T5 compensator had been reset to match engine specs T5 Base, IGV angle was 4 degrees. Bleed valve gave no sign of leak.
So we planned to cek PCD gage, inlet air filter dp gage, swap T5 tehrmocouple, and check bleed valve, and wonder that why IGV set was so small (range = 3 deg - 9 deg) that can caused low inlet air flow.

After PCD gage checked, it is confirmed that gage of TCP is correct, actual. Low PCD is confirmed.
And next day it's found that inlet air dp actual pressure is 4.8" WC. So, we suspected that dirty/semi blocked inlet air filter was caused of T5 topping problem. But, unfortunately after all inlet air filter had been changed, the T5 problem still the same, even with inlet air new filter and inlet air dp low.

Then we tried to adjust IGV angle. After IGV angle was changed from 4 deg to 3 deg, NGP can reach 100% at T5 only 1180 F. The problem is solved.


Moral of the story =
the truth is out there.
never believe anything untill you reconfirm it.

Sedikit tentang Transfer

Bismillaahirrahmaanirraahiim.

Alhamdulillah akhirnya saya bisa menulis blog lagi setelah sejak bulan Maret 08 vacuum.

Saat ini posisi Rotating Equipment Engineer sedang laris manis, seiring dengan meningkatnya harga minyak dunia. Dengan tingginya harga minyak itu memacu negara produsen minyak untuk memproduksi minyak dan gas semaksimal-maksimalnya.

Ada produsen yang reservoirnya masih berproduksi dengan mantapnya karena masih tinggi kandungan reservoirnya sehingga pressurenya masih tinggi. Namun ada pula produsen yang reservoirnya berproduksi dengan megap-megap karena reservoirnya sudah tua, ”mature” kalau kata istilah keren eufimismenya.

Dua-duanya memerlukan rotating equipment yang prima. Produsen yang mantap tadi tidak ingin kehilangan opportunity menghasilkan minyak dan gas sebanyak-banyaknya sedangkan produsen yang mature tadi tidak ingin target produksinya gagal tercapai gara-gara sumur-sumurnya yang sudah tua mati akibat compressor mati di tengah jalan.

Rotating Engineer yang sedang mencari opportunity di tengah hiruk-pikuknya “transfer pemain” harus mempersiapkan diri luar dalam. “Dalam” maksudnya adalah skill, experience, dan knowledgenya. Sedangkan “luar” adalah ia harus mengetahui lika-liku perusahaan yang ditaksirnya. Mulai dari prospek produksinya, environment kerjanya, job description yang ditawarkan, lokasi kerja, budaya kerjanya, salary and benefit, serta dampaknya terhadap keluarga.

Perusahaan-perusahaan besar biasanya memberi tanggungjawab kerja yang spesifik, misalnya cuma mengurus turbin gas maintenance saja dari segi teknis. Namun untuk perusahaan medium atau small size akan memberi tanggung jawab dari a sampai z. Jadi misalnya akan ada overhaul turbin gas, maka sang rotating engineer akan mengurus mulai dari kontraknya dengan vendor, transportasi dari site ke shop vendor sampai ke site lagi, installation, sertifikasi crane, jumlah man power, dlsb. Ini semua dirangkum dalam spec pack. Jadi, ia bertindak sebagai project manager. Ini bagus untuk rotating engineer yang ingin belajar secara general operasional. Namun, untuk Rot Eng yang sudah berpengalaman ia akan lebih memilih yang spesifik saja, di perusahaan yang besar jadinya.

Penting bagi kita untuk selalu mereposisi diri, memiliki networking yang banyak, dan membentuk brand image yang baik tentang diri kita. Ini dilakukan dengan terus mengasah profesionalisme diri dan ringan tangan membantu siapa saja. Tidak ada jaminan seseorang itu akan tetap nomor 1. Hidup ini dinamis.

Jadi targetnya adalah: employer yang mencari kita, bukan kita yang apply untuk suatu posisi job.

Semoga bermanfaat.

Kritik dan komentar serta masukan terima kasih banyak.

Wasalam
290608

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.

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.

Kabar Gembira

Alhamdulillaahirobbil aalamiin.

Telah lahir anak kami yang ketiga: Sucihati Muhaimina Eira pada hari Jum'at tanggal 1 Safar 1429 H (bertepatan dengan tanggal 8 - Feb - 2008) pada pukul 08.20 WIB di Pontianak.

Semoga menjadi orang yang solehah, hidup selalu dalam taufik dan hidayah Allah SWT, khusnul khotimah, rezeki mulia, sehat wal afiat, dan dimudahkan segala urusannya. Amin ya Robbal alamiin.

Wasalam ww.

==============================================

Feira Budiarsyah Arief <....@...> wrote:
Assalamu'alaikum Wr Wb
Kami semua dari Depok mengucapkan selamat atas kelahiran anak ketiga
(adik Ilma dan Radia); JUMAT 30 MUHARRAM 1429 H / 8 FEBRUARI 2008 PUKUL 8.15 WIB PANJANG 48 CM BERAT 3,45 KG, semoga ALLAH SWT meridhoi, menjadi anak yang sholehah, berbakti kepada kedua orang tua, sehat, dan dimurahkan rezkinya, amin.
Wassalamualaikum Wr Wb
Yong Sekeluarga
Depok,

======================================================
From: aulia arfiansyah arief <">****@****>
Date: Sun, 10 Feb 2008 17:26:50 -0800 (PST)
Subject: Selamat Atas Kelahiran Suci Hati

Asww. Selamat Atas Kelahiran Adik Ilma dan Radia. Semoga menjadi anak yang solehah berbakti kepada orang tua dan agama Allah sampai anak keturunan hingga akhir zaman, Amin. Wasl
======================================================

From: Yanuar Z. Arief [mailto:ya*****@******]

Sent: Friday, February 08, 2008 12:00 PM

To:

Subject: Re: lahir
Assalamu'alaykum wr wb,
Barakallah, selamat ya!!
semoga menjadi anak salehah.
dan semoganya ibunya cepat sehat kembali.
wassalam,
yy

==================================================

From: Fahmi Muhanna *****@*****.com

Date: Feb 8, 2008 11:35 AM

Subject:

To: mailto:rotatingengineer@gmail.com

iya pak selamat ya pak atas amanah yang di berikanInsyaAllah menjadi anak yang sholaha.

Wassalam

Fahmi

========================================================

From: muhammad syaepudin <***@****>

Date: Jan 23, 2008 4:18 PM

Subject:

To:rotatingengineer@gmail.com

Selamat juga pak arief Smoga lancar dan dimudahkan proses kelahirannya, dan diluaskan rizkinya aamien.

========================================================

Pengalaman (memang) Mahal Harganya….

Ternyata ilmu dan pengalaman itu memang benar mahal harganya. Bermula dari mesin mobil yang seing mati jika dari kecepatan tinggi pindah persneling ke posisi netral. Misalnya, saat berjalan dengan gigi 3 kemudian ada tikungan belok kiri atau kanan saya sering posisikan gigi balik ke netral, nah saat telah balik ke netral itu mesin kok sering tiba-tiba mati. Bayangkankan, repot jadinya jika lalu lintas pas ramai kemudian kita start-start engine karena tiba-tiba mati.


Saya coba selesaikan dengan cara symptomp based troubleshooting. Idle screw dan power screw carburator serta setelan gas saya coba setel-setel. Dibuat rpm jadi lebih tinggi dari sebelumnya. Namun, masih gagal.
Saya coba bawa ke bengkel, bocor katanya gasket intake manifold. OK lah saya pikir sekalian benerin gasket exhaust dan lubang-lubang baut yang mulai dol di manifold. Juga kata bengkel distributor nya kotor. Dibersihkan. Setelah semua selesai bayar 450an ribu perak. Mesin jadi halus. Namun, problem awal tetap tidak terpecahkan, mesin masih sering mati saat netral.
Analisa pindah ke saringan bensin, jangan-jangan kotor. Ganti. Tetap tidak menyelesaikan masalah.


Karburator saya pikir kotor. Bongkar sendiri, bersihkan sendiri. Beli karburator kit. 53rb perak. Rendam pake minyak tanah dalam kaleng semalaman. Pasang lagi rapi-rapi. Gagal juga.
Ganti karbuator saja. Beli karburator kelas dua baru. 470rb perak. Mungkin akan menyelesaikan masalah karena saya punya kelihatannya sudah bulukan dan siapa tahu saya menyervisnya kemaren kurang baik, maklum baru belajar. Sekalian sama pompa bensin yang asli kyoshan punya toyota kijang. 270rb perak. Karena saya tidak ada dengar bunyi klik-klik dan saya pencet-pencet tuasnya tidak nyedot dan ndorong dari tubing inlet dan dischargenya. Gagal. Saya sumbat lubang di gasket tatakan (30 ribu perak), agak baikan. Namun tetap gagal. Saya cabut gasket tatakan, halus namun mesin tetap mati jika setelahj run 2 menit. Bunyi mesin pincang/sinjal. Wah, mungkin pengapian salah nih, saya coba ubah-ubah urutan pengapian busi, eh malah meledak-ledak. Tahu-tahu saya salah asumsi, saya pikir putaran distributor berlawanan arah jarum jam, eh ternyata setelah saya buka distributor cap-nya, kepala distributornya ternyata mutarnya searah jarum jam pas saya putar pakai kunci ring pulley timingnya. Oooh pantesan meledak-ledak. Jadi, urutan 1-3-4-2 sudah saya dapat dengan membuat TDC silinder 1, yaitu pas klep intake dan exhaust pas nutup (posisi spring valve/klep pada posisi extension) dan tanda strip (-) di timing pulley pas posisi 0o. Namun, tetap pincang juga bunyi mesin, kemungkinan busi ada yang jelek. Saya ganti dengan busi baru merek Bosch W8DC 4 biji ditebus dengan harga 49500 perak. Namun.. masih pincang juga.


Saya lihat aliran bensin di saringan bensin banyak gelembung udara, dan bunyi mesin pincang seirama dengan banyaknya gelembung udara itu. Saya buka, muncrat bensin hitam dan di dalam filternya sumbat. Agar tidak cepat sumbat filternya maka saya ganti dengan fuel filter yang lebih besar punya suzuki vitara/escudo/sidekick harga 10 ribu perak. Di samping lebih besar kebetulan posisi inlet dan outlet filternya posisinya bagus, 180o sehingga selang bensin tidak melintir-melintir.








Kalau yang sebelumnya yang punya kijang posisi inlet dan outletnya 90o sehingga selang bensin agak melintir. Setelah dipasang, alhamdulillah mesin tidak mati lagi setelah run 2 menitan.


Kyosan filter (punya kijang, yang lama)










Tetapi tetap sedikit pincang bunyinya dan masih tetap mati kalau dipindah persneling ke netral. Saya coba atur timing dengan mengendorkan baut distributor, idle speed sudah disetel dengan memutar power dan idle screw. Saya coba puter ke advance (kalau distributer mutar searah jarum jam, maka untuk membuat advance kita harus memutarnya berlawanan jarum jam), wah memang benar ternyata saat saya putar, speed engine makin naik artinya timing sebelumnya tidak tepat. Saya ambil posisi yang mengakibatkan idle speed paling tinggi. Setelah itu baut distributor dikencangkan.
Baru setelah timing dikoreksi sedikit, bunyi mesin jadi halus, tidak mati saat netral, dan tidak mati setelah run 2 menitan.


Namun, ada PR yang musti saya harus lakukan yaitu mencuci tangki bensin agar bersih dari kerak-kerak karat, endapan air, dan kotoran lainnya.


Ternyata ilmu dan penglaman itu memang mahal nilainya, saya harus keluar uang buat beli karburator, pompa bensin, busi yang memang seharusnya belum perlu diganti serta waktu dan tenaga���������..

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.

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.

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.

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

Noise Level

Sound Pressure Level

The fact that the ratio of the sound pressure of the loudest sound (before the sensation of sound is changed into pain) to the sound pressure of the lowest one is about 1,000,000 has led to the adoption of a compressed scale called a logarithmic scale. If we call Pref the sound pressure of a just audible sound and P the sound presure, then we can define the sound pressure level (SPL) Lp as:

Lp = 20 log (P / Pref)

where log stands for the logarithm to the base 10 (ordinary logarithm). The unit used to express the sound pressure level is the decibel, abbreviated dB. The sound pressure level of audible sounds ranges from 0 dB through 120 dB. Sounds in excess of 120 dB may cause immediate irreversible hearing impairment, besides being quite painful for most individuals.

A-Weighted Sound Level
The sound pressure level has the advantage of being an objective yet a handy measure of sound intensity, but it has the drawback that it is far from being an accurate measure of what is actually perceived. This is because the ear's sensitivity is strongly dependent on frequency. Indeed, whearas a sound of 1 kHz and 0 dB is already audible, you need to raise up to 37 dB to be able to hear a tone of 100 Hz. The same holds for sounds above 16 kHz.
When this dependence of the sensation of loudness with frequency was discovered and measured (by Fletcher and Munson, in 1933), it was thought that by using an adequate filtering (i.e., frequency weighting) network, it would be possible to objectively measure that sensation. This filtering network would work in a similar way as the ear does, i.e., it would attenuate low frequency and very high frequencies, leaving middle frequencies almost unchanged. In other words, it would perform a bass and a treble cut prior to actually measuring the sound.

Fletcher and Munson Contours

There were some difficulties, however, in achieving such a measuring instrument or system. The most obvious one was that the ear behaved in a different way as regards to frequency dependence for different physical levels of sound. For instance, at very low levels, only middle-pitched sounds are heard, whereas at high levels all frequencies are heard more or less with the same loudness. Thus, it seemed reasonable to design three weighting networks intended for use at 40 dB, 70 dB and 100 dB, called A, B and C. A-weighting would thus be used at low levels, B-weighting at medium levels, and C-weighting at high levels (see figure below). The result of a measurement obtained with the A-weighting network is expressed in A-weighted decibels, abbreviated dBA or sometimes db(A).



A-, B- and C-frequency weighting contours

Of course, a sort of recursiveness was needed to complete a measurement. First one had to get an approximate value in order to decide whether to use the A, B or C network, and then perform the actual measurement with the appropriate weighting.
The second important difficulty comes from the fact that the Fletcher and Munson contours (as well as those finally standardized by ISO, i.e., the International Organisation of Standardization) are only statistical averages, with a fairly high standard deviation (a statistical measure of spread), so every measured value is appliccable to a population rather than to a specific individual; moreover, it is appliccable to an otologically normal population, because the contours where obtained within screened populations of otologically normal people.
The third difficulty has to do with the fact that those curves were obtained using pure tones, that is, single frequency sounds, which are actually very rare. Most everyday sounds, such as environmental noise, music or speech contain many frequencies at the same time. This has been perhaps the main reason why the originally intended application of the A-, B- and C-weightings failed.
Later studies showed that the loudness level, that is, a figure expressed in a unit called "phon" which equals the sound pressure level (in unweighted decibels) of an equally loud 1 kHz pure tone, did not constitute an actual scale for loudness. For instance, an 80-phon sound is not twice as loud as a 40-phon one. A new unit was devised, the "son", which may be measured using a spectrum analyzer (a measurement instrument capable of separating and measuring the different frequencies which compose sound or noise) and some calculations. As this scale, known plainly as loudness, is better correlated with the sensation of loudness, the ISO has standadrized the procedure (actually, two accepted procedures, according to the available data) under the ISO 532 International Standard. Nowadays there are even commercially available devices which automatically measure all the needed information and make the required computations to provide the loudness figure expressed in son.

A-Weighting and the Effects of Noise
To be sure, this does not answer the question of how annoying or disturbing a given noise may be. It is simply a scale for loudness. Several studies have focused on this issue, and there are some scales, such as the "noy" scale which quantifies noisiness under given assumptions, and of course, as afunction of the frequency content of the noise being assessed.
We can see, thus, that no available scale succeeds at measuring noise from an annoyance point of view, simply because annoyance is a very personal and context-related reaction.
Why has the A-weighting scale survived and become so popular and widespread?
Good question. The main reason is that several studies have shown a good correlation between A-weighted sound level and hearing damage, as well as speech interference. Without any other information available, the A-weighted sound level is the best single-figure guess available for assessing noise problems and making decisions. It also exhibits a fairly good correlation with the tendency of people to complain for noise pollution.
Interestingly, in spite of having been originally devised to measure low level sounds, the dBA scale proved to be better suited to measure hearing damage, which is likely to result from the exposure to loud sounds. How this has been discovered, I don������t know; perhaps it is traceably to the lack of other measuring instruments, or to accidental luck, or to the use of all kinds of instruments available while striving to push the frontiers of knowledge further.
As to its use in legal matters, for instance its use in most Noise Ordinances or Acts, it is because it gives an objective measure of sound. It does not depend on the judgement of an officer or a sufferer or an offender. Everybody can measure it and then say whether it exceeds or not a given acceptable level. That������s valuable, even if not perfect. More perfect measures will perhaps arise in the future, suitable for different situations.


Sound Levels and Human Response from Common sounds
- Rocket launching pad(no ear protection) = 180 dB = Irreversible hearing loss
- Carrier deck jet operation/Air raid siren = 140 dB = Painfully loud
- Thunderclap = 130 dB
- Jet takeoff (200 ft)/Auto horn (3 ft) = 120 dB
- Maximum vocal effort/Pile driverRock concert = 110 dB
- Extremely loud/Garbage truckFirecrackers = 100 dB
- Very loud/Heavy truck (50 ft)/City traffic = 90 dB = Very annoyingHearing damage (8 Hrs)
- Alarm clock (2 ft)Hair dryer = 80 dB = Annoying
- Noisy restaurantFreeway trafficBusiness office = 70 dB = Telephone use difficult
- Air conditioning unitConversational speech = 60 dB = Intrusive
- Light auto traffic (100 ft) = 50 dB = Quiet
- Living roomBedroomQuiet office = 40 dB
- LibrarySoft whisper (15 ft) = 30 dB = Very quiet
- Broadcasting studio = 20 dB
- 10 dB = Just audible
- 0 dB =Hearing begins


trims

SAE Standard J2723

Specifies the procedure to be used for:

a. A manufacturer to certify the net power and torque rating of a production engine according to SAE J1349 or the gross engine power of a production engine according to SAE J1995.

b. Manufacturers who advertise their engine power and torque ratings as Certified to SAE J1349 or SAE J1995 shall follow this procedure. Certification of engine power and torque to SAE J1349 or SAE J1995 is voluntary, however, this power certification process is mandatory for those advertising power ratings as "Certified to SAE J1349".

Third-party witnessing is the main provision of J2723.

Trims

SAE Standard J1995

SAE Standard J1995

Date Published:
June 1995

Title:

Engine Power Test Code-Spark Ignition and Compression Ignition- Gross Power Rating

Issuing Committee:

Engine Power Test Code

Scope:

This SAE Standard has been adopted by SAE to specify:

a. A basis for gross engine power rating,
b. Reference inlet air and fuel supply test conditions,
c. A method for correcting observed power to reference conditions, and
d. A method for determining gross full load engine power with a dynamometer.

This test code document is applicable to both four- stroke and two-stroke spark ignition (SI) and compression ignition (CI) engines, naturally aspirated and pressure charged, with and without charge air cooling. This document does not apply to aircraft or marine engines. This test code supersedes those portions of SAE J1349 dealing with gross power rating. Standard CI diesel fuel specifications are range mean values for Type 2-D EPA test fuel per Title 40, Code of Federal Regulations, Part 86.1313-87. The corresponding test code for net power rating is SAE J1349. The document for mapping engine performance is SAE J1312.

ISO 2534 (1972) differs from SAE J1995 in several areas, among which are most important are:

a. This document is not limited to road vehicles;
b. This document requires inlet fuel temperature be controlled to 40 °C on CI engines;
c. This document includes a reference fuel specification and requires that engine power be corrected to that specification on all CI and certain SI engines;
d. This document includes a different procedure for testing engines with a laboratory charge air cooler (ISO method optional); and
e. This document includes a different procedure for correcting power to reference atmospheric conditions on turbocharged CI engines.

Complete correlation has not been established with ISO 3046. It is expected that this power test code will eventually align with ISO 1585 and ISO 2534.

trims

SAE Standard J1349

SAE Standard J1349

Date Published:
August 2004

Title:
Engine Power Test Code-Spark Ignition and Compression Ignition-Net Power Rating

Issuing Committee:
Engine Power Test Code

Scope:

This SAE Standard has been adopted by SAE to specify:

a. A basis for net engine power rating
b. Reference inlet air and fuel supply test conditions
c. A method for correcting observed power to reference conditions
d. A method for determining net full load engine power with a dynamometer.

Trims

Beberapa Kiat Membuat CV yang Bergreget

Ada pepatah yang mengatakan “Anda hanya punya 1x kesempatan untuk memberikan kesan pertama”.
Berdasarkan data dari CareerBuilder.com/Harris Interactive survey:

“74% para pekerja di AS telah berganti profesi sekali seumur hidup dan sekitar 35% berniat ganti pekerjaan.”

Jika CV merupakan kesan pertama yang dapat Anda berikan maka berikut ini beberapa kiat yang tidak ada salahnya Anda pertimbangkan:

Ø Ceritakan tentang kesuksesan Anda, bukan tugas sehari-hari Anda. Pemberi kerja tidak peduli dengan rutinitas dan tugas-tugas Anda, akan tetapi apa yang telah Anda hasilkan, apa yang dapat Anda berikan kepada mereka.
Ø Tekankan kemampuan-kemampuan praktis yang Anda miliki.
Ø Sertakan pernyataan objektif tujuan Anda pindah kerja atau ingin bekerja.
Ø Jika Anda merupakan pegawai yang sudah 10-20an tahun bekerja, masukkan riwayat kerja 10 tahun terakhir saja, serta sekelumit singkat saja yang mengenai riwayat awal karir.
Ø Masukkan kegiatan-kegiatan santai atau hobi Anda. Jika Anda sudah berumur di atas 40 tahun, memasukkan kegiatan fisik di kala santai sangat berarti karena akan menggambarkan kondisi kesehatan Anda. Tidak ada salahnya memasukkan hobi bersepeda jarak jauh Anda disebutkan saja, atau hobi lari marathon misalnya.

Berikut beberapa rujukan di internet mengenai karir:


AARP, aarp.org/money/careers/choosecareer
Berisi kiat-kiat memilih penasihat dalam memilih karir baru

About.com, careerplanning.
Mulailah dengan ikut kuis “Should you make a career change?”

eHow.com/how_138208_prepare-career-change.html
Berisi langkah-langkah untuk karir transisi

Linkedln.com
Dbase besar berisi para profesional dari banyak industri

Salary.com
Berguna untuk referensi mengenai nama pekerjaan, deskripsi, dan besaran gajinya

Toastmasters.org
Organisasi bagi profesional yang berusaha mengembangkan kemampuan komunikasi dan presentasi

WetFeet.com
Menjual “panduan orang dalam” tentang pemimpin serta fungsi-fungsi individual, kiat mencari kerja, dan masih banyak lagi

Yahoogroups.com
Ketik “[kota Anda]+karir” dalam kota search untuk mencari kelompok-kelompok diskusi guna mengubah karir

trims

Panduan Singkat Mencari Penyebab Kerusakan Mobil Bensin Berdasarkan Gejala yang Timbul (yg berhubungan dg fuel, emisi, & engine management system)

Troubleshooting mungkin dapat diartikan secara bebas sebagai mencari sebab permasalahan.
Berikut ini adalah panduan troubleshooting permasalahan pada mobil bensin berdasarkan gejala-gejala yang timbul. Panduan ini dibuat khusus untuk mobil yang memakai engine management system. Namun, bisa juga Anda gunakan untuk mobil-mobil konvensional sebagai panduan umum. Bedanya, mobil konvensional tidak memiliki sensor-sensor ataupun ada yang tidak memakai fuel injektor, melainkan memakai karburator.

MAP = Manifold Absolute Pressure
MAF = Manifold Air Flow
EGR = Exhaust Gas Regulator
TPS = Throttle Position Sensor
IAC = Idlespeed Control


Engine noise
- Hiss (bunyi mendesis) – vacuum leaks
- Adanya loncatan busur api atau Electrical arching (snapping noise)

Engine mau distart tetapi engine tidak mau hidup
- charcoal canister full of fuel
- faulty MAP, MAF, or coolant sensor or circuit
- EGR valve stuck open
- Faulty canister vent valve
- Fuel pressure lack
- Fuel empty
- Water in fuel
- Aki soak (putaran starter pelan/lemah)
- Busi kotor
- Severe vacuum leak
- Injektor mampet
- Sirkuit start rusak
- Faulty air flow sensor
- IAC valve defective

Engine sulit hidup – dingin
- Leaking injectors

Engine sulit hidup – panas
- Aki soak
- Air filter sumbat
- Defective coolant sensor/circuit
- Defective intake air temperature sensor/circuit
- Defective MAP or MAF
- Faulty TPS or circuit
- Aki kotor
- Ground jelek
- Busi kotor
- Fuel pressure
- Air flow sensor faulty
- PCV valve stuck open
- Vacuum/air leak

Engine hidup tetapi tidak mau jalan
- Faulty canister vent valve
- EGR stuck open
- Coil & alternator loose
- Intake manifold vacuum leaks
- Airflow kurang

Engine “lopes” idle, rough, erratic
- Air filter clogged
- Throttle plate/bore kotor
- EGR
- Vacuum leak
- Air leak in intake duct/manifold
- IAC
- Lean injector
- Rich injector
- Fuel pump
- Cold only = PCV stuk
- Warm only = TPS or MAF

Engine mati saat langsam/idle.
- Busi kotor/gap
- Kabel busi
- EGR valve
- Fuel filter/line
- Vacuum leak
- Incorrect timing
- Kompresi silinde low/sinjal

Excessive idle speed
- vacuum leak
- throttle linkage macet

Engine misses throughout driving speed range
- Fuel filter kotor
- Fuel pump pressure
- Busi
- Kabel busi
- Kompresi piston lemah
- Ignition system
- Vacuum leak
- Lean injector

Hesitation/stumbles/stalls kalau pedal gas diinjak/ditekan untuk akselerasi.
- Busi kotor
- Fuel filter
- TPS
- Air temperature sensor
- MAP
- Air leak di manifold
- MAF
- Throttle plate/bore kotor
- Ignition coil/kabel
- Fuel pump pressure
- Fuel injektor

Engine lack power/sluggish performance
- Air filter mampet
- Exhaust mampet
- Vacuum leak
- EGR valve stuck open
- MAP
- Busi gap
- Fuel filter
- Vacuum leak
- Injektor

Stall on decal/coming to a quick stop
- EGR valve stuck/leakage around base
- TPS
- Idle air control valve malfunction
- Fuel filter
- Gap busi
- Vacuum leak

Surging at steady speed
- Air filter
- Vacuum leak
- Air leak
- EGR valve stuck/leak at base
- O2 sensor
- TPS
- MAF, MAP
- Loose fuel injector connector
- TCC (torque converter connector)
- Fuel pressure, pump
- Lean injector
- Defective computer/information sensor

Engine tidak mau mati (diesel/runs on) saat kunci kontak di-off-kan atau idle speednya terlalu tinggi
- vacuum leak
- EGR Valve
- Excessive engine operation temperature, overheating
- Incorrect spark plug selection

Engine "nembak" /Back firing (baik dari intake dan/atau exhaust)
- vacuum leak di PCV or canister purgeline
- vacuum leak at fuel injector, intake manifold air control valve or vacuum line
- Faulty secondary ignition system (busi retak, kabel)
- EGR
- Emission control system
- Faulty air valve
- Valve clearance
- Damaged valve spring, sticking, burned check by vacuum gage

Bensin boros
- air filter mampet
- PCV
- O2 sensor
- Timing
- Fuel leak
- Injector worn/damage
- Rem mampet
- Ban kempes/kurang angin

Detonasi (spark knock)
- EGR valve inoperative
- Vacuum leak
- Busi
- Knck sensor
- Fuel quality

Exhaust banyak asapnya
- Black (rich): air filter, intake duct mampet, O2 sensor
- Blue (burning oil): PCV valve stuck, PCV filter
- Brown/yellow (lean): fuel filter, lean injector

Bau bensin
- tank overfilled
- tank cap gasket
- lines leaking
- injector stuck open
- injector leak internally
- injector leak externally
- EVAP canister filter in EEC mampet
- Vapor leaks from Evaporative Emission Control System lines


Beberapa Tools yang sangat baik untuk dimiliki karena akan sangat membantu dalam troubleshooting:

- stetoskop khusus otomotif (ujungnya yang ditempelkan berbentuk panjang seperti tubing, sedangkan yang punya dokter, yang ditempelkan berbentuk bulat)
- Analyzer
- Vacuum gage
- termometer laser
- timing light
- power cylinder pessure gage

trims

Pencucian Turbin Gas

Pencucian turbin gas atau biasa disebut dengan istilah crankwash, cranksoak wash, atau fire wash. Pada cranksoak wash dan crankwash digunakan detergen sedangkan fire wash hanya menggunakan air distillate (air suling). Untuk tiap manufacturer turbin gas merekomendasikan penggunanaa distillate water dengan syarat tertentu (misalnya kadar maksimum senyawa dalam distillate water yang diizinkan: chlorides, total dissolved salt, sulphates, acidity, silica, specific conductance), detergen apa saja yang diperbolehkan, konsentrasi pencampuran antara deterjen dengan water, samapai seberapa bersih pencucian dilakukan, serta frekwensi pencucian.

Tujuan pencucian turbin ini adalah untuk mempertahankan performa engine dengan cara meredam tingkat pertambahan fouling pada sudu-sudu compressor gas turbine. Adanya fouling ini menyebabkan efisiensi aerodinamis sudu-sudu berkurang yang ditandai dengan berkurangnya pressure kompresi dari final stage compressor (discharge compressor pressure). Jadi untuk mengkompensasikan kekurangan pressure ini, untuk mendapatkan gas turbine power output yang sama, maka konsumsi fuel akan meningkat. Sehingga indikasi yang dapat dipakai untuk menentukan kapan saat yang tepat untuk melakukan crankwash atau fie wash adalah: compressor discharge pressure, bellmouth static pressure, dan/atau combustor exhaust temperature.

Contohnya: Rolls Royce Avon 1535-G121 disarankan untuk dilakukan fire wash jika terjadi penurunan 3% bellmouth static pressure.


trims.