Wednesday, December 15, 2010

PROPYLENE OXIDE ON CHEMICAL TANKERS-- CAPT AJIT VADAKAYIL




PROPYLENE OXIDE

In general the cargo temperature should be kept/ maintained below 25C. If the ambient temperatures are low cooling systems need not be run.

It is mandatory to have 100% emergency backup cooling capacity is required. The backup unit can be used ONLY if the the working unit has broken down.
A slow increase in temperature due to sun on deck can be kept in check by sprinkler system. A sudden unexplained increase in temperature is highly unlikely, but in case that happens it could be due to polymerization. The Ship Operator and company must be contacted immediately. Jettisoning of cargo may be the answer.
Greedy charterers will try to use low ambient temperatures and keep ship at the borderline without cooling systems --  Master is the man on the spot and the best judge, about temperatures expected during the voyage .
Propylene oxide , Butylene oxide and Mixtures of Propylene and Ethylene oxide containing upto 26% are all included under ALKYLENE OXIDE. They can only be carried on ships which have the chemical approved in the COF.  Ships that have never carried Alkylene oxide will be inspected by a surveyor under the CDI scheme, to verify compliance. Zinc based coatings are acceptable.
Loading temperatures will NOT exceed:--
PO/ 25 C
BO/ 35 C
MO/ 20 C
If the ship does NOT have a refrigeration system with separate cooling SW lines and pumps , the tanks must have 6000 mm Aq pressure rating, unless the ambient temperatures are very low, and the BP of the chemical can never be breached. The ship must be able to provide high purity nitrogen pad during the entire transit.
Past 3 cargoes in the cargo tank earmarked should not have contained acids, alkalies, amines , ammonia or oxidizing substances. Review the USCG compatible chart for adjacent cargo . Cargo systems must be free of all residues of polymerization inhibitors such as TBC ( Tertiary Butyl Catechol ) , from prior cargoes of Vinvl Chloride Monomer, Butadiene, Isoprene or Styrene. A waterwash cannot effectively remove TBC, only a copius methanol spray wash can.
Master should request the specific product safety data sheet before commencement of loading. A product safety data sheet for Propylene Oxide must be posted .

Used for making polyurethane foams, coatings, adhesives, fumigant, insecticide etc.
Recognised carcinogen
Colorless liquid
Sweet Ether-like odour above 200ppm
Marpol category /Y
SG/ 0.83
Correction Factor 0.001248
Cargo group/ Alkylene Oxide
CHRIS code/ POX
BP/ 33 C
MP/ -104.4C
AH/ 30 deg C
VP at 20 deg C /  449 mm Hg
VP at 34.5 deg C / 760mm Hg
Vapor density (air =1.0)/ 2
Solubility in water at 20C/ 40.5%

An extremely reactive, flammable liquid with a wide explosive range. Ignited by heat, sparks or open flame. Flashback along vapor trail may occur. Fire or contamination may cause violent rupture of the tank.
FP/ less than-29°C
Flammable limits/ 2.1% to 37%
Autoignition temperature/ 465 deg C
Nitrogen of high purity 99.9% N2  , with oxygen content <0.05% ( 500 ppm )

Massive water spray can extinguish small Propylene Oxide fires
Personnel will not usually tolerate moderate or high vapor concentrations
Will bum skin and eyes.  Diluted solution is more irritating than undiluted.
Very destructive on mucose membranes
If vapor inhaled, it will cause dyspnea ( difficulty in breathing ), pulmonary odema, headache, nausea, vomiting or loss of consciousness

Irritation of eyes and respiratory tract. Overexposing will cause serious injury.  Contact with uncovered skin produces frostbite. Ingestion by skin will cause serious illness or death.

Coughing, watering eyes, nausea, frostbitten skin.

Prolonged contact with skin causes frostbite burn. Smarting of skin and first-degree bums on short exposure; may cause secondary bums on lung exposure.

Soluble in water, Alchohol , Acetone, Benzene and Ether.

In case of spillage use sand to absorb, not saw dust.

Polymerize violently on distillation or in the presence of catalysts such as nonoxidizing mineral acids, Sulfuric acid, Nitric acid, Organic acids, Caustics, Ammonia, Aliphatic amines, Alkanolamines and certain salts.

Stainless Steel,  Zinc Silicate Coatings are materials resistant to Propylene Oxide.

USCG compatibility chart/16

During activities where the potential for exposure is high, like connection and disconnection, sampling and opening the tank after discharge for cleaning, the personnel involved should wear full personal protective equipment, which includes full eye, body, and respiratory protection
All crew members should be advised about the hazards of the Propylene Oxide and be instructed to stay away from the deck area around the manifold during cargo operations. Appropriate warning signs should be posted at the gangway and around the deck also indicting that double skin and bottoms as well as cofferdams are inerted.
Vessel ventilation systems drawing air from the weather deck area should not be used during all loading, discharging, and cleaning operations involving Propylene Oxide.
Fit  P/V valves (3 PSI) are fitted on the double skin to be inerted .
Rig Nitrogen purging hose) for inerting double skin.
Have on board sufficient supply of N2 for the maintenance of the N2 blanket during the voyage.
Have full sets of spares for all cooling units and compressors.
Keep sufficient Propylene Glycol for cooling cargo during the voyage.
Have sufficient portable stainless steel valves for doubling up on cargo line and vapor return line—in case of leak.
Install provision for sampling of the double skin atmosphere.
Vapor return will be used.
Spirally wound Teflon gaskets are required .

LOAD PREPARATION
1.       Check the pH of the cleaning water and pipeline drains during the final rinsing.
2.       Ballast and void spaces double skin must be well drained and inerted.
3.       Each ballast space must be fitted with a P/V valve and nitrogen filling arrangement.
4.       Conduct pressure drop test of cofferdam to check for cargo seal leak.
5.       Heating coils to be hydraulic pressure tested for leaks, air blown , purged with N2 and blanked.
6.       Cooling units to be test run .
7.       Ensure all tank pressure sensors are corrected for zero error.
8.       Pressure gauges (if any sensors are faulty) to be installed on each tank.
9.       Nitrogen generators to be test run—or bottle bank to be ready.
10.    If additional Y-piece and reducer are used, position a stainless steel valve at the outside (to prevent spill from extra pipe space when disconnecting the shore hose).
11.    All valves, piping and  tanks to be pressure tested .
12.    The deck sprinkler system to be tried out.
13.    Closed MMC sampling device to be tested.
14.    Use dedicated seamless stainless steelhoses or Hosta Flon (Teflon lined) hoses marked: "For alkylene oxide transfer only."
15.    Manifold drip trays to be cleaned and bottom covered with two inches fresh water.
16.    Check Teflon vapor return hoses and connections.
All tanks must be VISUALLY inspected for readiness first,  and then nitrogen purged to 2% oxygen level ( DOW needs lower level of 0.5% or 5000 ppm ). Double skin must be nitrogen purged to bring down oxygen content to 2% ( 20000 ppm ) , only then ship is load ready.
Connecting the cargo hose must be supervised by Chief officer.
Prior to loading the manifold and the tank area to be taped off and unauthorized personnel not allowed in this area. Post proper warning signs.
The pre-loading inspection includes; High level and overflow alarms testing, tank tightness, remote temperature accuracy check, tank pressure gauge, closed ullage device and safety equipment preparedness check.
Before commencement of loading the piping system to be pressurized and tested for leaks, using Nitrogen.
Under no circumstances must open ullaging/ sampling be done. First foot sample is a must in narrow mouth bottles with Polyseal caps. Loading cannot resume unless the results are received. Samples must be retained for 6 months.
Ship's equipped with IGG can use the same for purging of void spaces and double bottoms.
Adjacent cargo tanks must either be inerted, loaded with compatible cargo or ballasted.
Double skin must be inerted or ballasted.

IMMEDIATE AFTER LOADING
For line clearing use Nitrogen.
Cargo lines must not be allowed to be drained into the drip tray.
Manifold , domes and valves o be sealed.
Disconnecting the cargo hose must be supervised by the Chief Officer.
After loading is completed and ullaging, sampling is completed immediately reduce tank pressure to 1400 mm Aq and monitor if pressure holds steady.
Start cooling units and run them for system function check, provided cargo level is sufficient    in the tank.
In general the cargo temperature should be kept/maintained below 25C.  If the ambient temperatures are low cooling systems need not be run.
It is mandatory to have 100% emergency backup cooling capacity is required. The backup unit can be used ONLY if the the working unit has broken down.
Positive pressure between 700-1400 mm Aq must be maintained throughout the voyage.
Observe and record tankwise cargo temperature/ pressure  every 4 hours. The carriage log will be attached to the surveyors report at Disport.
Daily measure the Oxygen content in ballast tanks and void spaces surrounding the cargo tanks. Keep a slight overpressure in these spaces.
Rise in Temperature means  either the cooling units are not working or that the cargo may be reacting.
If it is loss of cooling , change over to back up cooler. if possible, repair the inoperative cooler. The coolers must  never be removed from the tank loaded with Propylene Oxide. Watch the cargo temperature and tank pressure closely. Notify the Ship Operator and company.
A slow increase in temperature due to sun on deck can be kept in check by sprinkler system. A sudden unexplained increase in temperature is highly unlikely, but in case that happens it could be due to polymerization. The Chemical Operator must be contacted immediately.  Jettisoning of cargo may be the answer.

Loss of pressure means there are leaks.

PRIOR TO DISCHARGE PREPARATIONS
Purge the pumps) cofferdam by N2 before commencement of pumping.
Manifold drip trays to be cleaned and filled with 2 inches fresh water.
The tank pressure to be closely monitored and kept at positive pressure by nitrogen balancing.

TANK WASHING
Without opening any butterworth ports take in a few cubic meters of fresh water into the tank from the manifold. Pump this water overboard at sea.
Ventilate the tank .
During the ventilation operation, all flammable/ toxic precautions must be taken. Crew members should be kept away from the area.
Propylene Oxide vapors are heavier ( double ) than air and in certain weather conditions, Propylene Oxide vapor may concentrate above deck-level and travel a considerable distance along deck or enter into any other tank or spaces that may be left open.
Propylene Oxide vapors are highly soluble in water, such that a water spray (Butterworthing) into a tank containing Propylene Oxide vapor may result in a rapid reduction of the tank interior pressure and COLLAPSE the tank. Use of inert gas is an acceptable method of purging cargo tanks for cleaning.

-------CAPT AJIT VADAKAYIL ( 28 YEARS IN COMMAND )

20 comments:

  1. Do you ever come to Houston or Texas City? Give me a call if you come in. I have a TWIC card and sometimes I go to the port.
    One of my customers is Talleres Industriales in Panama. I supply some parts to Lino Arosemena down there. Just recently I went to Texas City to retrieve an electric motor that was placed, by accident, on the wrong ship. I forwarded it to Rodderdam.
    Saludos,
    HH

    ReplyDelete
  2. thanks for good information

    can you post more information about cooling units on chemical tankers , or is there any refrigerated tanks on chemical tankers ?

    ReplyDelete
  3. hi mahmoud,

    if the ambient temperatures are high, propylene oxide is usually carried on refrigerated gas tankers- not chemical tankers.

    capt ajit vadakayil
    ..

    ReplyDelete
  4. thanks for replay

    is that mean that there are no refrigerated tanks can be used on chemical tankers ( in general ) ? and why ?

    ReplyDelete
  5. hi mahmoud,

    it is far more cheaper to charter a refrigerated gas tanker, that to waste a whole ship to carry DEDICATED propylene oxide.

    there are a few ships who have a couple of tanks which can be cooled (like couple of tanks for oil in steam coil heating ) -- for small parcels.

    capt ajit vadakayil..

    ReplyDelete
  6. Can PO be stored in container other than stainless steel? What coating should be provided internally if required?

    ReplyDelete
    Replies
    1. hi sj,

      stainless steel and zinc silicate lining are ok.

      capt ajit vadakayil
      ..

      Delete
  7. Captain,
    I have a question regarding the adjacent cargo tanks. Is a cargo tank which has only corner tot corner intersection with the loaded cargo tank to be considered as an adjacent space?

    ReplyDelete
    Replies
    1. hi m,

      corner to corner tanks have cruciform welds. this is NOT a 4 way jucntion weld--but rather a 3 way junction. cargo can never leak from corner to corner--however heat can transmit say from a heated veg oil tank to say polymerising styrene , causing a polymerised corner .

      common CRUCIFORM welds is NOT permitted between Bunker tanks and toxic chemical tank—but it IS allowed between water reactive chemical tank and Ballast tanks.

      For HEAT segregation to prevent polymerization/ decomposition/ evolution of dangerous gas—cruciform weld touching is NOT allowed.

      Touching CRUCIFORM welds NOT involving heat segregation between incompatible chemicals are allowed.

      capt ajit vadakayil
      ..

      Delete
  8. Dear Captain,

    First of all, I would like to thank you that you are doing such a beatiful task. We are planning to store PO in storage tanks near Meditterenean sea. How can I learn the special equipments using during unloading operation. For example, somewhere I read that Dry Disconnect Coupling are used. Could you give some information about that. On the other hand, we are thinking to construct the PO pipelines under sea instead of over jetty. Is it possible, did you see any port like this.

    Best Regards

    ReplyDelete
    Replies
    1. hi t,

      they use DDC for chemicals like benzene, acrylonitrile , propylene oxide etc.

      PUSH and TWIST to connect TWIST and PULL to disconnect
      • Safe-Valve cannot be opened until unit is fully coupled
      • Economical -No fluid loss on disconnection of hoses.

      When PO is handled under low ambient temperature coolers are NOT requires. Pipeline content gets hot in sunlight.

      capt ajit vadakayil
      ..

      Delete
  9. Hi Captain,

    Do you carry PO in ISO Containers or in a bulk form? What is the practical pipeline size from ship to storage tank? Did you see any Port carrying PO under sea from ship to land?

    Regards

    ReplyDelete
    Replies
    1. hi t,

      i have carried only in ship's tanks.

      pipeline size depends on the quantity and distance from manifold to shore tank.

      NO-- not seen underwater pipelines for PO.

      capt ajit vadakayil
      ..

      Delete
  10. Hi captain,

    Is there any limitation during discharging like velocity of fluid?

    - What is the range of DWT and max. Draft of ship in order to use for bulk transportation of P0 (it is requİred for Dolphın pier design).

    How the ship is designed as compartment?

    -What is the typical unloading method from ship to site storage tank? İs it maintained under the Nitrogen blanketing within the tank design limit? What is the typical pump pressure and debt of ship for unloading purpose?

    -What is the typıcal pipe (generally you experienced) line and loading arm size from ship to site storage tank? Is there any safety limitation for pipe length between vessel and site tank storage facilities for unloading of PO?

    Thanks in advance. You are very helpfull

    ReplyDelete
    Replies
    1. hi t,

      chemical tankers can carry this cargo --if ship's COF allows it.

      limitations in loading/ dischg depends on CP parameters and local terminal regulations.

      capt ajit vadakayil
      ..

      Delete
  11. What is the range of DWT and max. Draft of ship in order to use for bulk transportation of P0 (it is requİred for Dolphın pier design).

    ReplyDelete
    Replies
    1. hi t,

      you do NOT need a ship of more than 20000 DWT , 13 mtrs draft .

      capt ajit vadakayil
      ..

      Delete
  12. -What is the typical unloading method from ship to site storage tank? Is it maintained under the Nitrogen blanketing within the tank design limit? What is the typical pump pressure and debt of ship for unloading purpose?

    ReplyDelete
    Replies
    1. hi t,

      use deepwell pump and follow the guidelines in the post.

      capt ajit vadakayil
      ..

      Delete
  13. Hi captain,

    do you come also to Meditterenean Sea for PO transport.

    ReplyDelete