Skip to main content

Shaft Alignment


 Optical Alignment
At the for'd end of the engine room a light box emitting light through a pin hole is fixed from the design height of the crankshaft.

Using the sighting gear in stern frame boss with solid piece fitted. The stern frame boss is marked off for boring . The solid piece is then exchanged for a sighting piece.
A second sighting gear with sighting piece is fitted to the bore hole in the aft peak bulkhead. This is adjusted until the light source can be seen through the boss and aft peak bulkhead sighting pieces. The sighting piece is replaced by the fixed piece and the bulkhead may be machined. The stern tube is scribed out and the p.c.d. of the bolts which will support the stern tube flange marked off. A similar procedure us repeated for other bulkheads. When boring out is completed the stern tube is hauled into position, wood packing being fitted under the flange before bolting up at the aft peak bulkhead, the external stern tube nut is screwed up hard making a rigid connection at the after end. The tail end shaft is now fitted into the stern tube, the flange of the tail end shaft is now the standard by which the remaining line shafting will be aligned.
The trailing block (or towing block), of fitted, sometimes an ordinary plummer block is fitted (bearing material all round) is mow fitted around tail end shaft using feelers and wedging, chocked and bolted sown. The bearing acts also as an auxiliary thrust with a large clearance so that there is no possibility of it taking over from the main thrust under normal conditions other wise the towing block would shear.
This takes the form of a split brass ring fitted to the for'd end of the towing block which allows the tail end shaft to be disconnected from the intermediate shaft and hence rotate freely whilst the ship is under extended towing . The after face of the connecting flange then rides against this brass ring.

Coupling relationship method
The rest of the intermediate shafting is dropped into position on lower half bearings and using tail end flange as a standard they are lined up . This is done by using feelers between the faces of adjoining flanges, wedging the lower half bearings until faces are parallel with a 1/10mm gap between.
A parallel block is used around the periphery of the flanges. The intermediate bearings are chocked up by cast iron chocks about 50mm thick and bolted down. Couplings are continually rechecked. The thrust block is now aligned coupling to coupling and secured.

Main engine alignment
Bedplate and crankshaft now landed on hardwood blocks in approximately the position, slightly lower than true. It is now raised and jacked into position by lining the mating couplings on thrust and crankshaft. Cast iron chock thickness now measured, a small allowance being made to allow for individual fitting after machining. As each chock fitted its corresponding stud bolt is screwed through to engine seating and secured top to bottom. Checks made to ensure that shaft alignment is maintained, interference fit coupling bolts fitted and nuts screwed up.
It should be understood that the lining up of the shaft will only be true for one set of conditions such as on the building stocks or floating in a light condition. During service with variable loading some hogging and sagging takes place but there is sufficient flexibility in the shaft system to take care of this variation. Any bearing which runs chronically hot is almost certainly due to bad initial alignment.

Optical sight line method
This method uses a micro alignment telescope which generates a sight line between an illuminated reflective target at one end of the shafting and the telescope mounted at the other end. The sight line is generated at a uniform height above the shaft vertically above the centreline of the shaft. A movable scale or target is employed on the intermediate shaft at bearing support points to measure distance from shaft to the sight line. The reflective target and movable scale consists of a magnetic 'v'-block fitted with transverse inclinometer and vertical stand with micrometer and scale.

Laser system
Similar to optical arrangement except that a laser housing generates a collimated red laser beam above the shaft which is detected by a centring detector at the other end of the shafting. A moving scale detector is used at intermediate bearing position.

Taut wire method (Pilgrims wire)
Consists of steel wire anchored above shaft at one end of system and led over a pulley with suspended weight at the other end.
The height of the pulley and fixed anchorage are adjusted so that they are the same distance above the shaft and are positioned vertically over the shaft centre line. A microstaff is employed to measure the differences in height at bearing support points between shafts and wire, an allowance being made for wire sag.
A master inclinometer is employed to monitor ships movement during the aligning process.

 
Bearing load method

Top cover off and horizontal alignment checked by measuring the side clearances of the shaft within the bearings. By using the system shown the shaft is carefully jacked up and a graph plotted. Initially a curve will be plotted as the ships structure stress relieves itself from the weight of the shafting, shaft still sitting on bearing material.
When curve assumes a straight line shaft has left bearing and in order to avoid damaging the shaft only sufficient plots will be taken to establish the slope of the straight line. The slope of the line for each bearing is put into a computer program which establishes the shaft system characteristic.

 

Comments

  1. You have a genuine ability to create something useful for us. You have shared a wonderful post about A2-70 Stainless Steel Hex Bolt and thank you very much for your effort to share such information with us.

    ReplyDelete
  2. <a href="https://saihouselifting.com/services/house-alignment-services/> House Alignment Services </a></strong>
    House Alignment services are required to strengthen the building, straighten the floors and walls, make the foundation stronger, etc. When the building becomes old, it starts to tilt and it starts putting pressure on different sections of the structure and leads to the weakening of the building, hence it is always advised to make use of house alignment services to take care of such problems.
    Cracks in the wall, the non-opening of doors, and the tilted ceiling are signs that you need the help of house alignment services.
    We have the required skilled manpower and modern machinery to undertake and complete house alignment services with ease.
    Sai House Lifting is one of the leading name House Alignment services providers in the country. We can undertake the House Alignment of a Building having up to 10 floors. We also undertake the strengthening of the foundation. We ensure our services are economical, safe, and are completed within the stipulated period.

    ReplyDelete
  3. House Lifting Service
    Looking for Reliable House Lifting Services by Jacks Company in Your Area Which provides the Best services at an Affordable Cost? Want to Lift your House? We at Sai House Lifting with the help of Jack technology do the lifting of houses, buildings, temples, etc with a 100% Guarantee of Service and 0% Risk.

    For further queries contact us on 9671511915.

    ReplyDelete
  4. This article contains really valuable strategies for making our thoughts more productive. Define a step-by-step procedure that we can readily understand. For more information about Stainless Steel 17-4ph Fateners, please visit Vision Alloys.

    ReplyDelete
  5. After exploring this blog, I discovered a wealth of material that has helped me get started. I am delighted to have found this type of blog Duplex 2205 Fasteners. For more information, please visit.

    ReplyDelete
  6. More such things might interest my curiosity. I found your page to be informative, and I will return frequently. If you looking for best UNS N10276 Fasteners visit Shree Ashapura Steel Center.

    ReplyDelete
  7. Your blog is fantastic. I had been searching for this information for quite some time. You have a wealth of knowledge about Stainless Steel 316 Coil. Thank you for sharing your expertise. Continue to post.

    ReplyDelete
  8. I found your blog. It contains the best information about the products. We also provide the best quality of ASTM A790 Duplex 2205 Pipe. We have various types of pipes. Please visit here.

    ReplyDelete
  9. We are very glad to read your article. Which gives the best knowledge about those products. 304 Stainless Steel Hex Bolt, we provide premium quality at a reasonable price. Please click here and checkout.

    ReplyDelete
  10. Reading this article, we got very valuable and informative information. It looks like some thing better than others. We also offering Stainless Steel 316 Fasteners.

    ReplyDelete
  11. Thanks for sharing this article, We get more information. It is valuable for us. We produce high quality 304 Stainless Steel Shim at a reasonable price.

    ReplyDelete
  12. Amazing Site. I was quite impressed by the team's work.
    UNS S32760 Sheet, SS 317L Sheets

    ReplyDelete

Post a Comment

If you have any doubts.Please let me know

Popular posts from this blog

Differences between MC/MC-C and ME/ME-C engines

The electrohydraulic control mechanisms of the ME engine replace the following components of the conventional MC engine: Chain drive for camshaft Camshaft with fuel cams, exhaust cams and indicator cams Fuel pump actuating gear, including roller guides and reversing mechanism Conventional fuel pressure booster and VIT system Exhaust valve actuating gear and roller guides Engine driven starting air distributor Electronic governor with actuator Regulating shaft Engine side control console Mechanical cylinder lubricators. The Engine Control System of the ME engine comprises: Control units Hydraulic power supply unit Hydraulic cylinder units, including: Electronically controlled fuel injection, and Electronically controlled exhaust valve activation Electronically controlled starting air valves Electronically controlled auxiliary blowers Integrated electronic governor functions Tacho system Electronically controlled Alpha lubricators

Why is a man hole door elliptical in shape?

Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole  is lesser in size than the corresponding circular hole. More over it is prime concern to have a  smoothed generous radius at the corners to eliminate stress concentration. Hence other  geometrical shapes like rectangle and square are ruled out.  To compensate for the loss of material in the shell due to opening, a doubler ring has to be  provided around the opening. The thickness of the ring depends on the axis length along the  dirrection in which the stresses are maximum and the thickness of the shell. It is important to  align the minor axis along the length of the vessel, as the stress in this direction is  maximum. Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t=  thickness of the shell plating  Circumferential stress: Pd/4t  More over a considerable material and weight saving is achieved as minor is along the  direction of maximum stress.

Shell Expansion Plan

It is a two dimensional drawing of a three dimensional surface of the ship’s hull form. This plan is very useful for the following information:It is used for marking the location of a hull Damage on this plan by identifying the strake number , letter and frame number so that the exact location of the damage and also suggested repairs are marked in a localised copy. The shell expansion can be used for finding areas of painting surfaces such as topside, boot topping and bottom areas by applying Simpsons rules directly.  In the shell expansion the vertical scale used is different from the horizontal scale and a suitable adjustment has to be made when calculating areas. This becomes useful in solving disputes concerning areas of preparation and painting. It gives information on the thickness of the original strake which is indicated by the number in the circle shown in the strake.  The quality of steel used is also shown by letters A,B,D E and AH, BH,DH, EH.