Suction Piping Consideration

On ship, transfer fluida is important system during operation ship. Like on main engine, engine operation can not run without transfer fuel from fuel oil daily tank to engine, similarly cooling line, on sea water cooling line, Main engine will black out or over heating if there is no transfer sea water from sea chest to main engine.

This transfer fluida need equipment, that equipment wee call pump. On pump have two important position, suction side and discharge side. Suction pump is important position on pump operation, because of that we need some consideration to make suction design. That's consideration are :

1. The suction line size should always be one size larger than the pump suction connection size.
2. The optimum lenght of full size straight pipe, devoid of any obstruction to flow, immedietly up-stream of the pump suction connection, should be 10x suction pipe diameter.
3. The number valve and fitting in the suction line should be minimized because can increase pipe looses.
4. Suction piping should be designed and installed to minimize entrapped air. This consist of, avoidance of horisontal plane concentric reducer and proper orientation of eccentric reducer and straight position install on the top, and positive slop line.
5. Directly connected elbows should be avoided and when absolutly necessary, should be of the long radius style oriented to minimized un-balanced flow to impeller.
6. Suction line pipe joint design should be air tight. This is particularly true in long suction line and in situations in wich the situation lift is large.
7. Pump install on position as low as posible with liquid source to get NPSH requirement.
8. On suction line, velocity of fluida is designed on 5 ft/sec or 1.5 m/s.
9. If on suction line connect to manifold, the branch manifold line should be have velocity range on 5-8 ft/ sec or 1.5-2.5 m/s.

All above consideration is designed to get some advantage as followed :

1. To avoid hydraulic noise and associated vibration.
2. To avoid cavitation damage and its detrimental effects on vobration, bearing life, and seal life.
3. To avoid noisy operation, random axial load oscillations.
4. To avoid collecting air or gas at hight point.

Pressure Test

On shipyard normally have 2 time pressure test. Like on ABS Steel Vessel Rule 4.6.2 / 7.3 Hydrostatic Test. 

1. On shop pressure test, this test doing after workshop fabrication complete and accepted by owner. On this test to check welding quality, any leaking or not on shop weld position. This is refer to ABS Rule 7.3.1 "Hydrostatic Test of Pipes Before Installation Onboard" 

2. On site pressure tested, this teste doing after on site pipe erection complete and accepted by class and owner.  On this test to check flange spool joint and field weld position. This refer to ABS rule 7.3.3 "Test After Installation"

On pressure test there is some rule must be followed :

1. Pressure tust must 1.5 working pressure.
2. Pressure gauge must have active calibration certivicate.
3. Pipe line must accepted for final pipe line inspection by owner and class.
4. Pressure test must aware with safety oriented, like using HP square ball valve etc.

On Shipyard industry, normally have 2 methode pressure test.

1. Hydrotest thats mean pressure test using water pressure
2. Pneumatic test pressure thats mean pressure test using air pressure.

For item no 2 or pneumatic test, following ABS Steel rule 2012 no 4.6.2 / 7.3.4 "Pneumatic Test in Lieu of Hydrostatic Test" on this rule mention that's In general, Pneumatic test in lieu of hydrostatic test are not permitted. Only on special case, where it is impracticable to carry out the required hydrostatic tests, pneumatic tests may be considered. In such cases, the procedure for carrying out pneumatic test, having regard to safety of personnel, is to be submitted to the surveyor review.

Why pneumatic not permitted for pressure test, may be this is about safety reason. On pneumatic test we use compress air, the nature of the air is easy to expands. this is dangerous if we doing on open area, the weather will give dirrect effect to air, if we start test on morning and then we keep pressure untill noon, the air pressure will increase fastly and some time air pressure will be over presure requirement and will be explosion.

Other reason is, pneumatic difficult to check leaking position. This is not like on hydrotest, on hydrotest at least we will found seepage water on pipe joint when pipe leaking but on pneumatic test for small leaking difficult to identify althought we use shoap water to spry around pipe joint but this one not evective action.

Last reason, to avoid cheating trick, If we compare between pneumatic test and hydrotest, hydrotest is more difficult to cheat, because if any little leaking will show or identify with water drops, and for that case very easy to looking for. I f we use pneumatic test, we need good water foam to make air bubbles for leaking identification. And sometime, we can not see this air bubbles.

Piping Shipyard Flow of Work

On  ship building there are some part of job, like Hull, mechanic, piping, electric, carpentry, painting, etc. On this opportunity I want to explain about piping work flow on shipyard from begining untill end of process.

A. Making Pipe Flow Diagradm (PFD).

This is first step for piping job on shipyard, on this step will be discusion between owner and piping consultant about pipe flow requierement. on this step, for begining owner will explain to consultant what they needed, like :

• How long owner requirement for loading/unloading process may be 3 hours 5 hours, etc.
• What Fluida will use for this system.
• Loding/Unloding position on board, like port side only or star board side only or on both side.

After consultant get that basic Data, they will determain what owner requirement on PFD drawing. Normally consultant will make some optional drawing for approval to owner. After discus with owner, and owner make decision about Pipe Flow Diagram they need, owner will sign approval letter to continue next step design.

B.Making Pipe & Instrument Diagram (P&ID).

After consultant gat approval for PFD drawing, Consultant will make detail drawing for that PFD drawing. That drawing we call P&ID drawing on shipyard we more familiar with Piping Schematic Drawing.On this drawing will show complete pipe system equipment from type of pipe, valve, etc. Calculation of pump, size of pipe will be done on this step.

Schematic Pipe / P&ID Drawing

C. Making Piping Route Drawing.

This drawing is implementation P&ID drawing on site. Some consideration for this step are :

1. Good looking route pipe, pipe we route as straight as posible end then we try put bigger size pipe on bellow position. Avoid route pipe like "SNAKE". because will increase Head Losess and will give effect on pump performance.
2. Easy for treatment and maintenance, we must make pipe spool not to loong on narrow engine room. normally on narrow room/engine room longgest pipe spool straight lenght is 3000 mm. we must aware about Flange position, dont put flange above elctric equipment this one to avoid leaking pipe. One and other flange dont put straight vertically because will make difficult when install or repair it.
3. Shortline as Posible, we try to looking for shortest distance when we connect 2 eqipment using pipe. 
4. Following Class rule,on each class rule like ABS, BV, BKI they have some rule about pipe routing line, like some pipe can not throught some thank.
5. Minimize Bend of Pipe line. Espesially on bend 90 deg and 180 deg. Bend of pipe will increase looses pipe and will give dirrect effect to pump performance.

There are some 3D modeling software ussually use to route pipe on ship, there are :

1. Tribon 
2. Nupas 
3. Shipconstructor 
4. Autodesk Inventor 

Bellow is sample drawing, if only we use Autodesk Inbentor 2011

Autodesk Inventor 2011

Another methode to route pipe on site on shipyard ussually using Pipe Lay Out Drawing. on this methode we can use Auto Cad or may be manually we draw on paper work. On this methode, we only can see pipe on 4 view position, looking up, looking down bellow, looking port, looking stb. Bellow is drawing sample, if only we using Auto Cad 2010 for pipe lay out mathode.

Auto Cad 2010

D. Pipe Spool Drawing.

After we route pipe on site using some above software, next step is making pipe spool drawing. There are 3 methode to make pipe spool drawing :

1. Using 3D Software Like Tribon, Nupas, Autodesk Inventor.
2. Using Auto Cad.
3. Manually using isometric paper work. 

There are some pipe fabrication and installation problem if we use 3D software. On 3D software they use milimeter size use for their pipe drawing. This problem espsecially on steel ship bellow 90M or on narrow ship area like on Engine Room or Accomodation room. On this case, the problem is starting from pipe designer when they route pipe on site using 3D modeling. when they route some pipe system on this area they will found crouded area, not only piping run, but they will see electrical, ducting, and some mechanical equipment like pump, engine, etc. To avoid those all equipment sometime the piping designer will make "NON" Factory elbow bend, like pipe bend 33 degree or may be pipe bend 24 degree. This is special pipe elbow bend and on site pipe fitter will cut elbow bend with manually method to get this special elbow size, becuse they use manual methode so degree accuracy is not too accurate. 

After drawing problem, on site when they errect that pipe, when they take pipe position they will use manual methode to get pipe postion. Normally they will use some plate/small pipe scrub to hit the bulkhead. they use their listening filling to get right frame position. And for NOted, normally this methode is less accurate.

Differrent on Oil & Gas industry, when they check pipe position esspecially on end pipe connection  they use theodolit or may be field people said Tennol. this equipment will give accurate pipe position, and normally they have +/- 10 mm tollerance.

Base on above 2 problem, this pipe will continued. for longger pipe line will give effect bigger un-accurate position. That problem will give some effect for piping production progress.

1. Re-work. On workshop, normally pipe spool has fabricated complete following pipe spool drawing. And they will welded it complete and fix. If on site errection fitter can not install that pipe spool the last methode is CUT that pipe spool and then modify on site.
2. Loose Time. Because of that re-work will give direct effect loose time production. we can easy emagine. If 1 spool only we modify on site, may be will not give big effect for piping production but if many pipe spool must modify on site how long time we need to repair it.
3. Poor pipe quality. Ussually on site fabrication is worse than on shop fabrication. On site re-works thats mean on site fabrication, because will do pipe fabrication on site. Why on site fabrication is worse? esspecially on ship production, first narrow warking area, on site they will difficult to get pipe fit up position like to move or to rotate pipe. Second one, work atmosphere, on narrow area like Engine Room they will meet crouded area. Many other trade worker will work on this area Third one minim air sirculation, this will give dirrect effect to pipe fitter because pipe fitter can not full 100% consentration. 
4. Re-Galvanize. On hot dipped Galvanize pipe after get cutting norrmaly must re-galvanize on new welding position this one to avoid faster pipe corroded. cheapper galvanize is using cold galvanize methode, but to get the better pipe spool quality. pipe spool after get on site modify and there is cutting thats pipe spool sent to hot dipped galvanize proscess.

To minimize Re-work when they errect pipe on site, on piping shipyard production, normally we put or give remark on pipe fabrication drawing. That remark is FW or Field Weld and other one is SW or shope weld. FW thats mean pipe weld joint position must welded on site. On this position, pipe fitter can adjust pipe fitting to get the best position. they will cut and re-fit up untill pipe spool get best on site position after that pipe welder will complete this pipe spool job with welding progress. SW is shop welding, on this pipe welding position pipe welder will full weld completed on piping workshop.

E. FIT-UP.

After spool drawing has completed, that drawing we call AFC (Approved For Construction) drawing. And this drawing will distribute to production department to produce it. This step we call Fit Up process. this step we do on workshop. On this step we have some factor will give effect to productivity speed,

1. AFC drawing
2. Material Available.
3. Tool & Equipment.
4. Man Power.

All this factor must meet together, when 1 item is not available that's mean productivity will slower and may be will stop.

On this step, all pipe spool will check by QC and client. for pipe edge praparation and pipe dimension following AFC pipe spool drawing.

F. Welding.

This step is important step, because will give effect for live time pipe for using. Normally on shipyard using 2 welding technic. there are, SMAW or "Stick Welding" and GTAW or "Argon Welding". For GTAW we use for small diameter pipe (bellow 2"). On bigger pipe, ussually using combination welding for root using GTAW after that using SMAW for capping.

G. NDT Tested.

To make sure that pipe have good pipe quality, pipe must be checked first. There are 2 checked. First is Visual Welding Check and the other is NDT check.

Pipe after get good result for visual inspection will be followed for NDT test, normally using X-Ray tested. On this tested, norrmally builder and user have agrement about tested percentage, how many percentage pipe must be taked.

H. Galvanizing.

After welding completed, we will collect pipe to be 2 type. 1 type is galvanize pipe and other one is non galvanize pipe. For Galvanize pipe use for corroded system like Ballast line, Sea Chest etc. For Non Galvanize pipe use for oil contamination like Fuel Oil Pipe, Lube Oil Pipe etc.

All Pipe After welding before following that's type will Blast first, after blasting process completed that pipe will collect which one is for galvanizing and which one for non galvanizing. For galvanizing, after got blasting process ussually will bring to galvanize company. And for non galvanize pipe will paint with primer coating.

To Be Continued