Calculation of intact stability and unsinkability for ASD Tug FV_34m

Calculation of intact stability and unsinkability for ASD Tug FV_34m
1. Introduction- „For whom it is necessary?”
I have informed with the familiar ship-building engineer that will be very interesting if to one computer model of a vessel to calculate Stability and Unsinkability on several of programs. Personally to me it would be very curious what outcomes will be received and how much they will differ. Absolutely logical question at once has followed: „ And for whom it is necessary?” I shall try to answer completely fairly:
I have made all this not about commercial purpose as well no engagement to make what - be advertising for software product. My overall objective it is to orientation young students and young ship-building engineers how to do similar calculations.
If I shall help at least to 10 people, I shall consider that I not for nothing have passed transactions.

2. The author of computer model of the tug and the arrangements of the tanks which have been carried out on the program “Delftship Professional” is the young engineer from Brazil Fellipe Verissimo. The model is alternative of his degree design. If it is necessary to be critical to model, we shall remark absence of an auxiliary thrust device in the fore, which device is very much typical of such tows.
3. Principal dimensions and characteristics of the tug:
Type: Azimuting Stern Drive Tug for Sea Towing
L bp=34m; L hull=34,436m; B=11,2m; H min=5,6m; H middle=6,247m; H max=7,337m
Design Draft T = 4m
Navigating Zone - Unlimited, without icing
Power of Main Engines: 2 x 2000kW=4000kW
Navigation Speed-13 knots; Draw Pull-about 70t
Arrangement of the towing hook: X=14m from AP; Y=0 and Z=7,8m from BL
Downflooding Points-ventilation openings in the funnels on PS and SB for ensure the circulation of the air in the ER:
X=15,8m from AP; Y=± 3,5m from CL and Z=10,7m from BL
The tow is fitted both to salvage operations and for fire-extinguishing in the open sea or in a port.
Except for marine towing it is possible to operate him and as harbor tug.
Crew 12 person
Definition of the weight and coordinates of CG of the Lightship- on prototype data:
D Lightship=651,08t; Xg=17,958m; Yg=0 and Zg=4,556m
Example: for project 21110 “Harbor Tug with engine power 3960kW and DW 195t” from book “Quick reference on the loads of mass of ocean vessels ”-2007 - Kireev, Matskevich and Ryazantsev, from page 130 it is visible that Zg Lightship =4,74m with LDWL = 35m; BDWL=12,6m and Hmain deck=6,2m
Or Zg Lightship / Hmain deck = 4,74 / 6,2=0,76
In the our case Zg Lightship / Hmiddle = 4,556/6,247 = 0,73
In the following calculation with Maxsurf Stability it is visible that the size for Zg Lightship is correctly accepted.
By ship with 100 % store and fuel / Full Displacement / in the part “Limiting KG” in Maxsurf Stability Booklet we can see Zgmax = 4,512m when Zg actual =3,952m. By ship with 10% store and fuel and ballast in aftpeak Zgmax=5,14m when (Zg fluid)actual =4,841m.
Date of the Lightship serve as the basic common base for comparison between three computer programs.
Differences in programs predetermine different Deadweight as at registration of tanks differences / though also inappreciable / in volumes under three programs are received.
From emergency cases the smallest size for Zg max is received at the Case 16 on program Dialog-Static:
Zg max = 4,96m when Zg actual=3,938m
4. Computer programs with which are made calculations
Computer model from Delftship Professional is transfer as IGES file in program Maxsurf Modeler Advanced then it is already possible to make out tanks and to do calculations on intact stability and unsinkability in program Maxsurf Stability Enterprise v.20.00.02.31 from 17 Dec. 2013-absolutely new version on replacement old Hydromax.
It is necessary to act with the same method with IGES file in program Sea Solution then the model should be unclosed in Sea Hydro v.6.10 from 02.11.2009, tanks are made out and accounts are fulfilled. It is very flexible and rapid program. There is also a lack - absence of functions for graphic exhibiting outcomes. But it is natural each program prolongs to explicate and be updated.
More especially position with third program Dialog-Static v. Win.02/2009/. She does not accept everyone’s IGES files. The communications are carried out the lightest method through AutoCAD 3D file, with dimension in mm, with cross sections of model only for SB at the symmetric construction, it is necessary polylines. Program Dialog-Static does not accept splines from AutoCAD. Notwithstanding what the program is designed for extremely much numbers of types of vessels and on availability of probability account of the index of division of the vessel compartments, in her there are also things which likely hereafter will be changed and supplemented. An example what for it is necessary to inject extra the Deck line and CL at injected already data on all cross sections of model. It would be logical if the program itself withdraws data from the general base.
Except for that actualization of two programs Sea Hydro and Dialog-Static under new Russian Rules RMRS-2014 is necessary.
But before to make what - be comparisons of accounts on intact stability and unsinkability it is necessary to compare the maximum volumes and coordinates of CG of these volumes for all tanks, made out on three programs. Only when we shall be convinced that variances insignificant / and it very much precisely has been tested/, it is possible to transfer to the following stage.
5. Stability and unsinkability booklet of the vessel, made out with program Maxsurf Stability
5.1 Used criteria for intact stability and unsinkability
5.1.1 For Intact stability
5.1.1.1 General criterion
IMO-MSC.267 (85) Code on Intact Stability
Part A-Mandatory Criteria
267 (85) Ch2-General Criteria
5.1.1.2 Additional criterion at circulation
Part A-267 (85) Ch3-Special Criteria for Certain Types of Ships
3.1 Passenger Ships
3.1.2 Turn: angle of equilibrium
5.1.1.3 Additional criterion for sudden action on the vessel of the stretched towline cable
By Australian rules RAN A015866 Intact
4.4.7 Towline pull
5.1.2 For unsinkability
IMO-SOLAS, II - 1/8
5.2 In the Stability booklet instead of the Silhouette it is necessary to show General arrangement of the vessel. But I think that it is necessary to respect copyrights of founders of mothers which have been used by development of the degree design, for this purpose and we publish only the Silhouette.
5.3 Calibration of tanks
It is carried out only for an even keel.
5.4 Cases of loads for unimpaired vessel under Rules RMRS-2014
By Rules the following 2 cases are obligatory:
5.4.1 Full Displacement / Ship with 100 % store and fuel/
5.4.2 Ship with 10 % store and fuel
Full Displacement is received on even keel, but at 10 % store and fuel we have unpleasant trim, for this purpose we shall consider the case from 10 % store and fuel with extra accepted liquid ballast in the aftpeak for trim on even keel.
5.5 Emergency cases of loads under Rules RMRS-2014
The following cases for tows are obligatory:
5.5.1 Damage in forepeak
5.5.2 Damage in aftpeak
Except for that check is recommended also at accident of the ER.
In the original degree design there are not accounts on unsinkability.
The chosen location of transverse bulkheads ensures unsinkability at filling of one what - be compartment that is visible in section „ Floodable Length” in the Stability Booklet.
Meaning the small length of the aftpeak, we shall test also a case of accident in steering compartment /Rudderpropeller Room /, as well share accident of the aftpeak and the steering compartment.
16 emergency cases surveyed, thus cases are included in them also at which it is necessary to accept ballast for reduction of the trim after accident. All 16 cases are calculated disregarding effects of heaving.
5.6 Account of an intact stability at circulation and at suddenly stretched tow cable it is carried out only for unimpaired vessel. It is supposed that at a state of failure the vessel will not fulfill the functions as tow or as rescue ship.
5.7 Curves of the Bonjean diagram in section "Hydrostatics" show only half of immersed area of each frame lines.
5.8 Account shear forces and bending moments it is shown only for unimpaired vessel that the volume of the document has not increased excessively.
5.9 Initial Stability / section”Specified Condition” / is shown only for two cases of loads of unimpaired vessel. In the document initial stability is not included the emergency cases of a loads from reasons already evocative in 5.8 /regardless of the fact that accounts carried out / .
6. Criteria on unsinkability under Rules RMRS-2014
We accept rules for tows with L > 40m at symmetrical flooding:
6.1 Transversal metacentric height > 0,05m
6.2 Maximum arm of the Righting lever curve > 0,1m
6.3 Length of the positive part of the Diagram at symmetrical flooding in final phases of filling > 20 deg
6.4 Area of the positive part of the Diagram > 0,0175 m.rad
6.5 Distance from Damage WL up to Downflooding Point > 0,3m
6.6 Angle of the maximum of the Righting lever curve > 20 deg
7. In comparative tables for emergency cases data on Moment trimming on 1 cm, Moment heeling on 1deg, Numbers of tons on 1cm draft, coefficients of fineness and trim with the purpose to decrease volume of additional information which is irrelevant with the proof about sufficing of criteria are not included.
8. At unsinkability calculations in those cases when to have to fill in unimpaired tank ballast for reduction or liquidation of the trim, two alternatives are accepted:
8.1 The foreseen ballast to be introduced as additional weight in case of loads, i.e. coordinates Xg and Zg are changed / Yg=0 at the symmetric filling / and displacement D is augmented.
The unsinkability calculation of the vessel with an emergency compartment on the constant displacement method as required under Rules RMRS is then fulfilled.
8.2 We accept, that the unimpaired tank which it is necessary to fill ballast for trim, it is spuriously damaged also it is included to compartment undergoing accident, but not up to emergency WL, and up to concrete level expressed % of filling. Thus weight displacement and coordinates of CG remain equal before accident.
Accounts on unsinkability it is executable also on the constant displacement method as required under Rules RMRS.
This alternative is more successful when it is unknown % of filling of the tank for trim. To suffice to make only a few approaching for guided.
If we shall accept these two alternatives at some emergency case of loads and we execute account on one of programs we shall see the following theoretical dependence:
D1 x GMt1 = D x GMt / this is known in theory of the ship as "Stability factor"/
Where D1 = D + P
P - quantity of the accepted ballast for trim
Hence GMt1 < GMt / and at two alternatives effect of free surfaces of the fluid in tanks is taken into account/
But the variance is small also it is practically possible to neglect.
Example: For the Case 9 at account on Sea Hydro it is received GMt1 = 2,024m < GMt = 2,059m
Respectively and the difference in Righting lever curves is very inappreciable, for example too for the Case 9:
(GZmax) 1 = 0,91m and GZmax = 0,926m
It agrees the Theory of unsinkability of the vessel and at two alternatives it is necessary to be received an equal draft and trim.
9. Outputs from accounts
9.1 Outputs for intact vessel
9.1.1 It is visible that for this type of ship the heaviest is demands under program Sea Hydro
In the comparative table for intact vessel it is visible what even at navigation area Limited I (R1) the tow satisfies demands under Rules RMRS only at 100 % store, and at 10 %- not. It means that the navigation area should be changed for operation at smaller wind pressure, for example for class “М-СП” / the mixed river - sea floating / we have wind pressure: 275Pa at 100 % store and 279 Pa at 10 % store; wind velocity <24m/s (46,6 knots); Height of waves - 3,5m. For such restricted navigation area the stability coefficient by the basic / Weather / criterion is received K = 17,8 at 100 % store and K = 11,5 at 10 % store and ballast in the aft peak.
9.1.2 On remaining two programs - Maxsurf Stability and Dialog-Static the tow satisfies demands both on IMO-MSC.267 (85) and under Rules RMRS for marine towing in unlimited navigation area at wind pressure 504 Pa.
If it is necessary to pick between these three programs, I in firstly would trust in Maxsurf Stability as her last version from December, 2013 include extremely affluent and diverse choice of stability and unsinkability criteria on very much numbers of Rules of Classification societies.
9.2 Outputs for emergency cases
From comparative tables for emergency cases / page 1-4 / it is visible as under three programs for all 16 cases the vessel satisfies demands on IMO-SOLAS, II - 1/8 and to Rules RMRS-2014 for symmetrical flooding.

10. The body line of the tow can be seen in his most effective sort, carried out on program Delftship Professional /see figs 1/.
11. How the tanks on Sea Hydro looks and on Dialog-Static it is possible to see on figs 2 and figs 3. On figs 3 it is visible and as data in Dialog-Static in the emergency case 7 replenish.
12. For successful performance of the calculations on the publication I am obliged to the following specialists:
- Naval architect Fellipe Verissimo for the computer model of the tug
- Naval architect Petr Ezhov-General Director of the company “Sea Tech Ltd“ which has kindly concede me the possibility to work with license copy of the program Sea Hydro
- Naval architect Valeriy Berezovsky - the ship-building engineer from the Ukraine which oriented me to programs Maxsurf Stability and Dialog-Static and to help me to transfer model in Dialog-Static.
Without their assistance I could not carry out the intention.
13. As I for first time work with programs Maxsurf Stability and Dialog-Static, irrespective of the careful calculations, the check and the analysis of the received outcomes, all the same is very probable somewhere that - be to miss.
With gratitude any critical remarks of professional character only if they are polite and tolerant will be taken into consideration. I shall try to answer all.
Naval architect: dipl. eng. Razmik Baharyan
05.07.2014- Bulgaria

 

I do not know exactly what you need from us because, honestly, I´m not able to read a so long paragraph.
I have enough experience in tug calculations. Attached is a file with the 3D model of a tug tanks.
If what you want is us to review your calculations, I have to tell you that you should give us much more data and, of course, we have to use a long time to analyze it, so it will be difficult to find someone willing to do it.
When it is necessary to define many tanks, I do not work with MaxSurf because it seems a program bit quick for the definition of tanks.

 

Hi Tansl,
You are mistake in your conjectures. I anywhere did not write that I need help. Also did not ask anybody to test my accounts. It in the right to do only the Surveyor of Classification Organization and only when I shall award him the completed engineering design of the vessel for approval,if there is the contract for construction.
Now on questions: What for basic text of the publication is long?
The answer is simply: If that which really is interested from the problem will study closely added files and requires from answers he at once will discover them in the basic text.
And as to up to that to you to like whether or not program Maxsurf Stability this question on mine has only subjective character.
Except for 3 programs already evocative in the publication I can work also with Dutch "Delftship Professional". But more all is pleasant to me Maxsurf Stability and I have written what for. And you at all do not specify other alternate program.
Obviously you are obliged to warn the forum of undesirable or irrelevant publications. I have intentionally waited for some days from the answer and have seen that already 78 persons have become interested from a published subject. Whether and for me the most important criterion is the subject actual whether or not it is reaction of readers. Let we shall keep they to decide.
Yours faithfully, Rabah

 

Clearly I do not understand you. You speak very poor English and I understand it worse.
I still do not understand the purpose of your thread. But no need to waste time with me.
Cheers

 

Dear Tansl,
That you have not understood the purpose of my publication, especially when I have clearly written her, to speak that you have serious difficulties with the English language.
Out of regard for my readers I always previously test the texts for grammar and spelling.
With in a word my publication is made for people which fathom her. And those which do not fathom, I cannot help them.

 

I appreciate that you are so kind to me. I know better than you my limited English. Fortunately I do not need your help.
I still do not understand what you meant by posting this thread. Seriously, I would appreciate you to explain me.
It amazes me the amount of glowing reviews that your thread has deserved.
I wish you all the best.

 

Rabah выполнил большой объём работы и это вызывает к нему большое уважение.
Я занимаюсь расчётами остойчивости и непотопляемости речных и морских судов. Имею большой опыт, так как 20 лет работаю в конструкторском бюро и ранее работал 10 лет инспектором речного Регистра. Поэтому я понимаю, сколько времени потребовалось Rabah, чтобы выполнить эту работу.
Я работаю с программой SeaHydro и очень доволен.
В Attached Thumbnails помещён скриншот интерфейса какой-то российской программы по расчёту непотопляемости.
Хочу спросить у Rabah: Как называется эта программа и кто её владелец?


--Computer Translation to English--
Rabah carried out a large amount of work and it causes him great respect.
I do stability calculations and flooding river and sea vessels. I have extensive experience since 20 years working in the design office and previously worked for 10 years inspector River Register. So I understand how long it took Rabah, to do the job.
I work with the program SeaHydro and very satisfied.
In Attached Thumbnails placed screenshot interface some Russian program for the calculation of flooding.
I want to ask Rabah: How is this program and who is the owner?

 

Dear Veniamin,
I am very pleased that you have evaluated my work. Thanks. I respond on your question: On figs 3 you have seen a fragment from program Dialog-Static from 2009 /Saint Petersburg/.

 

See more attachment files-Fig 4 and Fig 5

 

Hi guys,
I am sure that some from readers of the forum understanding Russian better and are hindered with English. For all of you which prefer Russian I add good translation of the text of the publication on Russian, made ship-building expert Valeriy Berezovsky.
Я уверен что некоторые из читателей форума более хорошо понимают русского языка и затрудняются с английским. Для всех вас которые предпочитают русского я добавляю хороший перевод текста публикации на русский, сделанным судостроительным специалистом Валерий Березовский.