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Propeller
Propeller and the stern tube is an independent survey items from the docking survey. But the
classification rules in docking survey say as follows:" The propeller and the after end of the stern bush are to be examined. The clearance in the stern
bush and the efficiency of the oil gland should be ascertained. In the case where a controllable pitch propeller is fitted, it is to be ascertained that the pitch control device is in good workingorder, and, if considered necessary, the device is to be opened up for further examination." These
survey are responsible on the Machinery surveyor . But hull surveyor also have some
elementary knowledge on propeller and stern tube. The followings are only guidance
concerning to these items.
11-1 Propeller Damage
The biggest damage of propelle is the broken blades; while sailing, when abnormal vibration
suddenly happens in the stern and continues, it may be caused because of the broken propeller blade . In this case, the engine should be stopped, then the extent of damage to be checked and
depending on the damage, the ship should visit to the nearest port for an Occasional Survey.If more than one-third of the blade is broken, there is a possibility that the damage also occurred
to the stern tube. In the dry dockd not only propeller but stern tube should be carafully examined.Sometimes propeller shaft should be
withdrawn.
The causes of this damage are contacting with a submerged or floating object or small materialdefect during manufacturing which developt to hair cracks, and or metal fatigue.
11.1.2 Bend of blade Bend occurs because of impact of the propeller with other objects; they can be detected easilyeven before the propeller is cleaned.
11.1.3 CracksSmall cracks are overlooked in many cases. They cannot be detected unless stagings are erectedand after cleaning of each blade. Even the hair cracks they have a possibility of expanding and
breaking the propeller blade. Thse hair cracks are discovered by dye penetration test.
Generally this test need not be carried out for the entire surface of the blade; it is customary tocheck only the area from the root to 0.4R of the blade.
In the previous dock if a stop-hole has been drilled at the crack end and the hole has been filled
with a wooden plug, pay attention whether crack ia extended or not. In this case refer to previous
Survey Record on this matter.
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Photo.11-1 Blade broken (1)
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Photo.11-2 Blade broken (2)
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Photo.11-3 Blade bent
11.1.4 Corrosion Similar to the rudder, the propeller blade may be subjected to spongiform corrosion (erosion) dueto cavitation. There is no good repair method; the surface can be smoothed using a grinder, or
depending on the position, the blade can be built up by welding, If the corrosion is severe, the
corroded part may be cut out and using the approved material and repaired by welding. These
welding repairs should be entrusted to the propeller manufacturers because welding of copper alloys is very difficult.
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Photo.11-4 Hair crack on the blade
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Photo.11-5 Blade errosion
11-2 Inspection of Blades According to data on cracks and broken blades, the blade is frequently cut at the location called
the P point; therefore, this part should be inspected with particular care. The P point lies on the
pressure side of the blade, and it is the point where the thickness of the blade is maximum andwhere the rounded radius of the boss terminates. The indication of the position on the propeller is
similar to the concept of the frame space indicating the position of the frame and beam shown in
the figure 11-1 below.
The blade is divided into parts formed by measuring arcs from the centre
of the propeller at every 10% of the radius of the propeller, such as 0.4R, 0.7R. The names of the blades are generally assigned as A, B, C, D and
E or (1), (2), (3), (4), and (5) in case of five-bladed propeller.
The name of each blade is engraved at the root of the blade. It can be find easily after green algae
or dirt on the propeller blade has been removed.The area shown in the figure should be inspected with special care. After polishing the surface
using a disk sander along the length of the blade, the surface should be examined using a hand
magnifying glass or by performing the dye penetrant test. For details of the dye penetrant test,
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以下未校正
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Fig.11-1 Propeller Nomenclature (1)
Fig.11-2 Propeller Nomenclature (2)
11.3 Propeller Repair The surface of the propeller blade is divided into three regions: A, B and C. The table belowshows the kinds of repairs that can or cannot be carried out in each region.
However, only typical damage and inspection procedures are covered here.
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Fig.11-3 The area for dye penetration test
Fig.11-4 Propeller blade
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R = Radius, Ct = Chode lenght in rudius r
Table 11-2-2 Kind of repair
11.4 Fall of Guard Ring A guard ring (also called a rope guard) is fitted between the propeller front face and the sternframe to prevent floating objects such as fishing nets from being fouled with the propeller shaft.
The guard ring is a split ring welded to the boss of the stern frame. It can come off easily if an
object hits it. A guard ring is not prescribed by the Rules, but if it has fallen off,it must be replaced by manufacturing a new ring and fitting it in place.
Fig.11-4 Gurd ring
12.5 Clearance Measurement
The clearance between the propeller shaft and the bearing should be measured during the bottom
inspection. There are two methods of
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measuring clearance, depending on the water — sealing method for the shaft. For the rudder, the
clearances in the longitudinal (fore-aft) and
transverse (p-s) directions of the rudder shaft are measured, but for the propeller shaft, becausethe lower surface of the shaft is in contact with the bearing, only the clearance of the upper
surface of the shaft has to be measured in case of a water--lubricated system.
Fig.11-5 Clearance of stern tube bearingFor an oil lubrication system, also measure the clearance at the lower surface.
However, for an oil — lubricated system, clearances of the upper and lower surfaces have to be
measured, because the shaft sinkage is small. Clearances in the transverse direction need not be
measured because the shaft is rotating all the time.
11.5.1 Clearances of sea water — lubricated bearingsSimilar to measuring the clearance of the rudder pintle, remove the guard ring, insert the feeler
gauge or the measuring wedge from the stern tube side and measure the clearance. Before the
lignumvitae dries out after the ship is drydocked, measure the clearance of the upper surface andrecord the results of the measure-ments in the Inspection Record Form M-1. For
a ship with twin shafts, item 1. in the form is for the propeller on starboard side, and item 2. isfor the port side. If a twin — shaft ship has shaft
brackets, enter the measurements in the lower Dart of the form
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Fig.11-6 Measurement of Clrarance
Table 11-2 Results of mesurement (1)
The allowable maximum clearances according to shaft diameter are given below. If the values below are exceeded, the stern tube bearing material should be replaced or repaired.
Table 11-3 Allowable max. clarance
12.5.2 Weardown of oil — lubricated bearings Unlike lignumvitae used in water
— lubricated bearings, metal can be used in oil
— lubricated
bearings, and the clearance between shaft and bearing can be reduced. Wear is also small, and
most modern ships use oil — lubricated bearings.Clearances should be measured at the same shaft positions as the previous measurement. To
specify the shaft position, use the position of
the propeller blade or the position of the main engine piston. Generally, this position is specifiedaccording to the position of the propeller blade; for example, measure clearance with blade A at
the top. If no hole for measuring sinkage is provided in the guard ring, the guard ring should be
removed, the screwed cap of the measuring hole removed, and a measuring instrument such as
Vernier calipers, so — called wear down gauge, inserted and distances from the bearing to the
upper and lower surface of the shaft measured. The measued records is to be entered in the
survey report showing the position of measured point sucha sa the Key Top or No. 6 Crank Top.;however, unless the bonnet is removed, the key position cannot be judged; therefore, it is
convenient to take a specific blade (cylinder) as the reference for sinkage measurement. In largeships today, propellers are generally keyless. Sinkage is the difference in measurement at the
time of inspection and measurement when the ship was built. The standard limit for sinkage is
0.3 mm irrespective of the shaftdiameter. Sinkage should be determined by studying the properties of lubricating oil, and the
history of temperatures of the lubricating oil and bearing material. An example of the Inspection
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Record is shown below.
Photo.11-6 Measuring clearnce
Example of position propeller shaft
Fig.11-7 Position of propeller blade
Table 11-4 Results of measurement (2)
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(1) Example of measuring clearance in a oil-lubricated bearing
(1) Original
(2) Overhaul of guard ring and cap bolt
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(3) Inserting the gauge
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(4) Measurenent
Fig. 11-5 Measuring of propeller shaft clearance
(2) Example of measurement results for sinkage
Measurement results for two ships and their graphs are provided below for reference.The part above the kinked line shows the top, and the part below the kinked line shows the
bottom measurement values. The position of the blade does not conform to the key top position
but the No. 8 piston top position.
Ship (1) : Tanker, 72,368G/T,built in 1975
Month Measurement Month Measurement
4/1977 114.30114.85 6/1978 115.40/114.75
9/1979 115.50/114.80 11/1980 115.50/114.80
5/1982 115.60/114.80 9/1983 115.30/114.70
5/1985 114.90/114.70 11/1986 114.90/114.60
10/1988 114.90/114.60 10/1990 115.10/114.90
9/1992 115.40/115.00
Ship (2) : Tanker, 43,444G/T, built in 1975
Month Measurement Month Measurement
12/1981 72.7/73.1 4/1984 72.6/73.2
5/1986 72.9/73.1 6/1988 73.3/73.3
4/1990 73.4/73.3 5/1992 73.3/73.4
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Fig.11-6 Results of measurement (3)
11.6 Inspection of Stern Tube Seal Oil leaks from the propeller boss in the stern frame of an oil — lubricated system can sometimes
be detected during a bottom inspection. This is probably due to a defective seal, therefore, adetailed examination of the
seal is necessary.
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Fig.11-7 Oil leakage from propeller boss
11.7 Bow Thruster and Side Thruster
These items are shipowner's options, therefore, they need not be inspected under class
requirements. However, if these items areinstalled on the ship, they should be inspected at the docking survey. Frequently observed
damage includes damage to guards at sea water ports due to impact with submerged or floatingobjects, and bent propeller blades. If the shaft seal is defective, water entersin to the ship;however, such incidents are not reported. Inspection results should be entered in the Survey
Report.
When the stainless plate is used in the surface of the nozzle, the corrosion of adjusent steel plate suould be carafully inspected.
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Fig.11-8 Damage of side thruster guard
Fig.11-9 Damage to side thruster
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Terjemahan
Baling-baling
Propeller dan tabung buritan merupakan item survei independen dari survei docking. Tapiaturan klasifikasi dalam survei docking mengatakan sebagai berikut:
"Baling-baling dan setelah akhir buritan semak harus diperiksa. Clearance di buritan semak dan
efisiensi kelenjar minyak harus dipastikan. Dalam kasus di mana baling-baling lapangan
dikontrol dipasang, itu adalah untuk dipastikan bahwa perangkat kontrol pitch adalah dalamrangka kerja yang baik, dan, jika dianggap perlu, perangkat ini harus dibuka untuk pemeriksaan
lebih lanjut. " Survei ini bertanggung jawab pada surveyor Mesin. Tapi lambung surveyor
juga memiliki beberapa pengetahuan dasar pada baling-baling dan tabung buritan.Berikut ini adalah hanya pedoman mengenai item ini.
11-1 Kerusakan Propeller
Kerusakan terbesar propelle adalah pisau patah, sedangkan sailin g, ketika tiba-tiba terjadi
getaran yang abnormal di buritan dan terus, mungkin disebabkan karena pisau baling-balingrusak. Dalam hal ini, mesin harus dihentikan, maka tingkat kerusakan yang akan diperiksa dan
tergantung kerusakan, kapal harus mengunjungi ke pelabuhan terdekat untuk Survey Sesekali.
Jika lebih dari sepertiga dari pisau rusak, ada kemungkinan bahwa kerusakan juga terjadi padatabung buritan. Dalam dockd kering tidak hanya baling-baling tapi tegas tabung harus carafully
diperiksa. Terkadang poros baling-baling harus
ditarik.Penyebab kerusakan ini dengan menghubungi terendam atau mengambang objek atau cacat
bahan kecil selama manufaktur yang developt untuk retak rambut, dan atau kelelahan logam.
11.1.2 Bend pisau Bend terjadi karena dampak dari baling-baling dengan benda lain, mereka dapat dideteksi
dengan mudah bahkan sebelum baling-baling dibersihkan.
11.1.3 Retak Retakan kecil diabaikan dalam banyak kasus. Mereka tidak dapat dideteksi kecuali stagings yang
didirikan dan setelah membersihkan pisau masing-masing. Bahkan rambut retak mereka
memiliki kemungkinan untuk memperluas dan melanggar pisau baling-baling. Thse retak rambut
yang ditemukan oleh uji penetrasi pewarna.Umumnya tes ini tidak perlu dilakukan untuk seluruh permukaan pisau, adalah kebiasaan untuk
memeriksa hanya daerah dari akar ke 0.4R pisau.
Di dermaga sebelumnya jika stop-lubang telah dibor pada akhir retak dan lubang telah diisi
dengan plug kayu, perhatikan apakah retak besarbesaran diperpanjang atau tidak. Dalam hal inimengacu pada sebelumnya Survei Record pada hal ini.
Photo.11-1 pisau rusak (1)
Photo.11-2 pisau patah (2)
Membungkuk Photo.11-3 pisau
11.1.4 Korosi
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Mirip dengan kemudi, pisau baling-baling dapat dikenakan spongiform korosi (erosi) akibat
kavitasi. Tidak ada metode perbaikan yang baik, permukaan dapat merapikan menggunakan
penggiling, atau tergantung pada posisi, pisau dapat dibangun dengan pengelasan, Jika korosi parah, bagian yang berkarat dapat dipotong dan menggunakan bahan dan disetujui diperbaiki
dengan pengelasan. Ini perbaikan pengelasan harus dipercayakan kepada produsen baling-baling
karena pengelasan paduan tembaga sangat sulit.
Photo.11-4 retak rambut pada pisau
Photo.11-5 pisau errosion
11-2 Pemeriksaan Blades Menurut data retak dan pisau patah, pisau sering dipotong di lokasi disebut titik P, karena itu,
bagian ini harus diperiksa dengan penanganan khusus. P Titik terletak pada sisi tekanan pisau,
dan itu adalah titik di mana ketebalan pisau maksimum dan di mana jari-jari bulat bos berakhir.Indikasi posisi pada baling-baling ini mirip dengan konsep ruang bingkai menunjukkan posisi
dari frame dan balok yang ditunjukkan pada gambar 11-1 di bawah ini.
Pisau ini dibagi menjadi bagian-bagian yang dibentuk dengan mengukur busur dari pusat
baling-baling pada setiap 10% dari radius baling-baling, seperti 0.4R, 0.7R. Nama-nama pisauumumnya ditugaskan sebagai A, B, C, D dan
E atau (1), (2), (3), (4), dan (5) dalam kasus propeller lima berbilah.
Nama masing-masing pisau yang terukir pada akar pisau. Hal ini dapat menemukan dengan
mudah setelah ganggang hijau atau kotoran pada pisau baling-baling telah dihapus.Area yang ditunjukkan pada gambar harus diperiksa dengan perawatan khusus. Setelah polishing
permukaan menggunakan sander disk yang sepanjang pisau, permukaan harus diperiksa dengan
menggunakan kaca pembesar tangan atau dengan melakukan uji dye penetrant. Untuk rinciandari uji dye penetrant,
以下未校正
Gbr.11-1 Propeller Nomenklatur (1)
Gbr.11-2 Propeller Nomenklatur (2)
11.3 Propeller Perbaikan Permukaan pisau baling-baling dibagi menjadi tiga wilayah: A, B dan C. Tabel di bawah inimenunjukkan jenis perbaikan yang dapat atau tidak dapat dilaksanakan di setiap daerah.
Namun, kerusakan dan prosedur inspeksi hanya khas yang dibahas di sini.
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Gbr.11-3 Daerah untuk uji penetrasi pewarna
Pisau Gbr.11-4 Propeller
R = Radius, Ct = Chode panjang di rudius r
Tabel 11-2-2 Jenis perbaikan
11.4 Kejatuhan Penjaga Cincin Sebuah cincin penjaga (juga disebut penjaga tali) dipasang antara wajah depan baling-baling dan
frame tegas untuk mencegah benda mengambang seperti jaring ikan dari diganjal dengan poros baling-baling. Cincin penjaga adalah split ring dilas ke bos dari frame buritan. Hal ini dapat
datang dengan mudah jika sebuah objek hits itu. Sebuah cincin penjaga tidak diresepkan oleh
Aturan, tetapi jika itu telah jatuh,
harus diganti oleh manufaktur cincin baru dan pas pada tempatnya.
Gbr.11-4 Gurd cincin
12.5 Pengukuran Izin Clearance antara poros baling-baling dan bantalan harus diukur selama pemeriksaan bawah. Adadua metode
mengukur clearance, tergantung pada metode air penyegelan untuk poros. Untuk kemudi, jarak
bagian memanjang (depan-belakang) dan
melintang (ps) arah dari poros kemudi diukur, tapi untuk poros baling-baling, karena permukaan bawah poros dalam kontak dengan bantalan, hanya pembersihan permukaan atas poros harus
diukur dalam kasus air - sistem dilumasi.
Gbr.11-5 Izin tabung bantalan tegasUntuk minyak pelumas sistem, juga mengukur clearance di permukaan bawah.
Namun, untuk sistem minyak pelumas, jarak dari permukaan atas dan bawah harus diukur,
karena sinkage poros kecil. Kelonggaran dalam arah melintang tidak perlu diukur karena poros berputar sepanjang waktu.
11.5.1 Jarak bebas laut bantalan air dilumasi Mirip dengan mengukur clearance