Wednesday, May 16, 2012

LIQUID HAMMER ON CHEMICAL TANKERS- CAPT AJIT VADAKAYIL




LIQUID HAMMER ON CHEMICAL TANKERS- CAPT AJIT VADAKAYIL

 When you allow a liquid hammer to happen on your ship, you must remember that you wake up all sleeping watchkeepers. Rest hours is NOT meant for shore auditors , but for your own safety.  In port if a liquid hammer breaks a pipeline, you may go offhire, and there are NO prizes.

On parcel chemical tankers you deliberately introduce compressed air in the cargo pipeline systems during the course of cargo work. It is important to understand the physics of liquid hammer.

Water hammer occurs as slugs of water are picked up at high speeds in a poorly designed steam main or in pipe coils or where there is a lift after a steam trap. When you heat cargo with high stern trim in cold weather , you will need to constantly drain the unlagged steam inlet line at the aftermost point. 

The danger on ageing ships is going off hire or having cargo delays.

As long as you remember to start heating very slowly using the small main inlet bypass, drain all water from the main inlet pipe, and keep the steam coils full of water ( not steam ) , do not allow steam to return to engine room by controlling only the return valve ( inlet to tank 100% open ) there will not be much scope for water hammer.

In some systems, the flow may be at 120 feet per second, which is about 82 m.p.h. As the slug of condensate is carried along the steam line it reaches an obstruction, such as a bend or a valve, where it is suddenly stopped. The effect of this impact can be imagined.

It is important to note that the damaging effect of waterhammer is due to steam velocity, NOT steam pressure. It can be as damaging in low pressure systems as it can in high. This can actually produce a safety hazard, as a valve or a strainer can be blown out by the force of water hammer.

Water Hammer in Condensate Return Lines

In most installations, water hammer in condensate return lines is caused by steam pockets forming and imploding. Frequently, the cause is a rise in the discharge line from a trap or a high pressure trap discharging into a low temperature wet return line ( steam winches return expanded steam , that is why the dia of the return pipe is more than inlet , unlike tank heating systems ) . A lift in the return line after the trap will cause water hammer because the temperature of the condensate leaving the trap exceeds 100 C.

Water hammer in steam lines is normally caused by the accumulation of condensate. All equipment using a modulating steam regulator on the steam supply must provide gravity condensate drainage from the steam traps. Lifts in the return line must be avoided. In a steam system, water hammer most often occurs when some of the steam condenses into water in a horizontal section of the steam piping. Subsequently, steam picks up the water, forms a "slug" and hurls it at high velocity into a pipe elbow, creating a loud hammering noise ( which can be heard by a nearby ship ) and greatly stressing thepipe. This condition is usually caused by a poor condensate drainage strategy.

Liquid for all practical purposes is not compressible, any energy that is applied to it is instantly transmitted. This energy becomes dynamic in nature when a force such as quick closing valve or a pump applies velocity to the fluid.

Surge or water hammer, as it is commonly known is the result of a sudden change in liquid velocity. Water hammer usually occurs when a transfer system is quickly started, stopped or is forced to make a rapid change in direction. Any of these events can lead to catastrophic system component failure. Without question, the primary cause of water hammer is the quick closing valve, whether manual or automatic. A valve closing in 1.5 sec. or less depending upon valve size and system conditions, causes an abrupt stoppage of flow. The pressure spike(acoustic wave)created at rapid valve closure can be high as five(5) times the system working pressure.

Unrestricted, this pressure spike or wave will rapidly accelerate to the speed of sound in liquid, which can exceed 4000 ft/sec.

Pressure surge is caused by Kinetic energy of a fluid in motion when it is forced to stop or change direction suddenly. It depends on the fluid compressibility where there are sudden changes in pressure. For example if a valve is closed suddenly at the end of a pipeline system a water hammer wave propagates in the pipe. Moving water in a pipe has kinetic energy proportional to the mass of the water in a given volume times the square of the velocity of the water.

Water hammer can cause pipelines to break or even explodeif the pressure is high enough. On the other hand, when a valve in a pipe is closed, the water downstream of the valve will attempt to continue flowing, creating a vacuum that may cause the pipe to collapse or implode. You must have seen shore cargo hoses often getting flattened this way at the end of dicharge. This problem can be particularly acute if the pipe is on a downhill slope depending on the ships trim.

Air in the pipes can be really difficult to get rid of. The laws of physics keeps air at the highest level and liquids at the lowest . As the water moves in the pipes it breaks the pockets of air up into tiny bubbles. Then the water flows past the bubbles, leaving the air still in the pipe. These tiny bubbles moving around, and expanding and contracting, are that rapid vibrating sound you hear in Framo hydraulic systems.

Remember to get rid of air from the highest point. Of course the jockey pump does its job of continious removal of air—but not from the highest point , which can sometimes be on top of the crane.



-------CAPT AJIT VADAKAYIL


3 comments:

  1. Such a great blog on freight shipping. Thanks for sharing sir.

    ReplyDelete
  2. nm rk
    November 2, 2017 at 12:02 PM
    Dear Captainji,Readers

    This is regarding NTPC RaeBareily Accident involving many lives.


    https://timesofindia.indiatimes.com/india/ntpc-plant-boiler-explosion-18-dead-toll-may-rise-as-many-feared-trapped/articleshow/61426217.cms
    XXXXXX

    Heads responsible must be dismissed and severely punished.I pray to Bhagwan wishing the departed souls to rest in peace.


    With Regards,
    Rajkiran

    Delete
    #####################
    Capt. Ajit Vadakayil
    November 2, 2017 at 1:05 PM

    I HAVE PREDICTED SEVERAL MAJOR DISASTERS AT SEA-- AND INCLUDED IT IN THE SHIPS SAFETY COMMITTEE REPORT WELL IN ADVANCE.

    ALL OF IT CAME TRUE

    AS A CAPTAIN I COULD NOT GO TO ENGINE ROOM TO SABOTAGE , RIGHT?

    LET ME REMEMBER THE LAST ONE ABOUT A BOILER

    I RAISED THE ISSUE IN THE SHIPs SAFETY COMMITEE MEETING --AND THE STUPID SARDARJEE CHIEF ENGINEER STARTED FIGHTING WITH ME-- HE SAID MY FEARS ARE UNFOUNDED

    BASICALLY HE WAS TRYING TO KEEP HIS OWN CHAIR SAFE— AND HE DID NOT EVEN UNDERSTAND BASICS .

    #################

    I JOINED THE SHIP AT PANAMA CANAL

    THE WINCHES WERE STEAM--THE BOILERS WERE HUGE

    WHILE ENTERING THE CANAL THE WINCHES WENT PHUTTT AS BOILERS TRIPPED

    SOMEHOW I MANAGED BY GETTING ALL HANDS ON DECK TO PULL ROPES WITH SHEER MUSCLE POWER-- AND I ASKED THE PILOT NOT TO REPORT IT ( WHISKY ) AND CAUSE A DELAY

    IN SUCH SCENARIOS IF CAPTAIN PUTS PRESSURE ON HIS ENGINE STAFF--THEY BYPASS USUAL SAFETY PROCEDURES, TO SAVE THEIR OWN JOBS

    THE SHIP HAD COME OUT OF DRYDOCK ONLY A MONTH AGO, AND DURING BRIEFING AT THE US OFFICE , I FOUND THAT THE ATMOSPHERIC CONDENSER TUBES -- 900 OF THEM WERE RENEWED.

    THE BOILER WAS TRIPPING AS WATER MUST ENTER THE BOILER -- NOT STEAM

    WHEN YOU HAVE STEAM WINCHES THE " NARROW" INLET TUBES ON DECK OF A 900 FOOT LONG SHIP TAKES THE STEAM TO THE WINCHES --IT EXPANDS AFTER THE WORK IS DONE AND THE DEPLETED STEAM COMES BACK VIA A " WIDE " RETURN PIPE.

    IT S THEN CONDENSED TO WATER AND SEND BACK TO BOILER --AS A CLOSED LOOP SYSTEM

    HOWEVER IF THE STEAM IS USED TO HEAT CARGO INSIDE TANKS -- THE ENGINEERING IS REVERSE—

    HERE THE INLET STEAM TUBES ARE "WIDE" AND THE RETURN WATER TUBES ARE "NARROW" AFTER EXCHANGING HEAT-- WATER IS INSIDE THE RETURN TUBES GO BACK TO THE BOILER HOTWELL AND THEN INTO THE BOILER --AS A CLOSED LOOP SYSTEM

    I HAVE NEVER SEEN ANY CUNT ENGINEER AT SEA UNDERSTANDING THIS SIMPLE CONCEPT

    EVERY SHIP I GO, I TELL THE SHORE OFFICE TO CHANGE THE INSTRUCTIONS IN THE TECHNICAL MANUALS .

    ON CHEMICAL TANKERS IGNORANCE CAN BE DANGEROUS

    http://ajitvadakayil.blogspot.in/2010/06/steam-heating-on-chemical-tankers-capt_06.html

    http://ajitvadakayil.blogspot.in/2011/11/marine-engineering-self-examiner.html

    SO SO SO

    AFTER TRANSITTING THE PANAMA CANAL, I HELD A SAFETY COMMITEE MEETING

    I FOUND THE SARDARJEE CHIEF ENGINEER ( WE HAD SAILED BEFORE WHEN I WAS SECOND MATE ON A 3 LAKH TONNER CRUDE CARRIER VLCC-- HE WAS TRAINEE FIFTH ENGINEER ) AND HIS ENGINEERING TEAM TO BE STUPID-NAY –CUNTS .

    ANYWAY I GAVE ORDERS - -THE STEAM WINCH "WIDE" SILVER PAINTED RETURN PIPE CARRYING STEAM BACK TO THE ATMOSPHERIC CONDENSER ( ALMOST ALL TUBES CHOKED BY TOUGH SCALE ) --800 FEET IN LENGTH MUST BE PAINTED BLACK--

    THE COLOUR BLACK IS A GOOD RADIATOR OF HEAT

    THE CUNT ENGINEER DID NOT EVEN KNOW THE PROPERTIES OF SILVER AND BLACK COLOUR

    CONTINUED TO 2-

    ReplyDelete
    Replies
    1. CONTINUED FROM 1-

      THE NEXT FIAT WAS-- TILL THE 90% CHOKED TUBES OF THE ATMOSHPERIC CONDENSOR WAS CLEARED , THE STEAM WINCH MUST BE KEPT ROTATING IDLE --FOR AT LEAST 20 MINUTES BEFORE ACTUAL USE

      THIS WAS TO PREVENT JHATKA ( SURGE )- WHERE WATER FROM COLD RETURN PIPES GOES INTO THE BOILER FIRST AND THEN SUDDENLY HOT STEAM ENTERS

      JATKA CAN MAKE HONI INTO ANHONI-- AND ANHONI INTO HONI ( MAKE OR BREAK WHERE REVERSE HOLDS TRUE )

      I USED JHATKA AS A CHANGE MANAGEMNT TOOL TOO.—THE FAMOUS VADAKAYIL KALARI TAP ON NOSE

      LATER I USED THE SAME JHATKA PRINCIPLE TO CLEAR THE SCALE CHOKED TUBES WITH HOT STEAM AND COLD FREON GAS

      http://ajitvadakayil.blogspot.in/2011/10/marine-engineering-self-examiner-water.html

      YOU KNOW HOW A CHAMPION RACE HORSE FEELS WHILE IN THE SOLE COMPANY OF DONKEYS -- AND HE IS FORCED TO BRAAAAY --JUST TO BLEND IN AND BE PART OF THE FUCKIN’ TEAM

      LATER THE SAME BOILER FURNACE HAD A EXPLOSION ( THE WEAK AREA OF THE FURNACE GAVE WAY ) AND SAVED THE SHIP-- I KNEW THE SPOT ..

      WHEN THE FURNACE EXPLODED I ASKED THE CHIEF ENGINEER TO CHECK THE DELIBERATE WEAK CRUMPLE ZONE SPOT AND HE CONFIRMED IT— LEST THE EXPLOSION BECOMES A BOMB . HERE A BOMB IS CONVERTED TO A WEAK POOFFFF

      I HAD PREDICTED THIS A WEEK IN ADVANCE AND SEND SEVERAL MESSAGES TO THE SHORE BOSSES.

      THIS WAS ABOUT THE WATER WALL PROTECTING THE REFRACTORY. IF THERE IS NO WATERWALL THE REFRACTORY OF THE FURNACE BECOME WHITE HOT --AND BECOMES A PERMANENT HEAT LEG OF THE FIRE TRAINGLE

      IN BOILER FURNACE-- AS SOON AS THE BOILER TRIPS HUGE FD FANS INJECT FRESH AIR BY ACC ( AUTOMATIC COMBUSTION CONTROL )

      SO SO SO

      HEAT IS THERE . FRESH OXYGEN IS INJECTED AND FUEL REMAINS IN A PUDDLE ( FURNACE OIL ) AT THE BOTTOMF THE FURNACE AS THE INJECTION NOZZLE AND SWIRLER IS NO GOOD WITH IMPROPERLY MAINTAINED OIL TEMPERATURES FOR FUEL INJECTION VISCOSITY

      http://ajitvadakayil.blogspot.in/2011/02/naive-sailor-low-sulphur-fuels-capt.html

      ASK ANY MARINE ENGINEER ANYWHERE ON THIS PLANET TO READ THIS COMMENT AND EXPLAIN THE GIST-- HE WILL SHIT IN HIS ENGINEERING LANGOT AND KEEP QUIET. HE WILL NOT BE GOOD ENOUGH TO COMMENT

      FUCKIN' CUNTS !

      READ THE SOLE COMMENT IN THE POST BELOW--

      http://defenseblog-njs.blogspot.in/2012/09/ins-vikramaditya-trial-malfunctions-to.html

      http://ajitvadakayil.blogspot.in/2011/01/economiser-on-chemical-tankers-capt.html

      http://ajitvadakayil.blogspot.in/2011/01/naive-sailor-fire-fighting-capt-ajit.html

      http://ajitvadakayil.blogspot.in/2011/02/me-crankcase-oil-mist-detector-alarm-on.html

      http://ajitvadakayil.blogspot.in/2011/02/main-engine-scavenge-fire-on-chemical.html

      BELOW IS AN EXAMPLE OF JHATKA—HONI CAN BECOME ANHONI

      http://ajitvadakayil.blogspot.in/2012/05/liquid-hammer-on-chemical-tankers-capt.html

      capt ajit vadakayil
      ..

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