Isocyanates characteristics & handling methods -Chemical tankers safety guide

Isocyanates require sophisticated handling for safety, health and loss prevention reasons. They need careful consideration prior loading , tank coating compatibility, cross compatibility with other cargoes carried, special tank cleaning procedures & environmental controls .

Product safety data sheets may be available from various sources. For safety preparation, until the specific product safety data sheet can be obtained, Chemical Data Guide for Bulk Shipment by Water (U.S. DoT), should be used. Concerning the IBC/BCH code (respective 16.2/5.2) the Master should request the specific product safety data sheet before commencement of loading. The safety data sheet posted must be in a language understood by ship's Officers and Crew.

Isocyanates handling special arrangements - Equipment Planning

Ensure that sufficient and suitable hoses for vapour return are on board.

Ensure that sufficient nitrogen hoses are on board

Ensure that closed sampling device is on board.

Ensure to have on board sufficient quantity of Dioctyl Phthalate (DOP) to fill the cargo pump cofferdam(s) before the loading.

If the permanent cargo line is not used for loading/discharging ensure that sufficient suitable cargo hoses, valves for the hose connections, any stainless steel bends for cargo handling and cleaning including drip pans for the connection/disconnection points are available. The rigging must have connections for line blowing.

If gas oil is used for cleaning, the Ship Operator will arrange gas oil supply with a moisture specification of less than 400 ppm.

For TDI, if gas oil is to be used as the tank cleaning medium (recirculation via fixed tank cleaning machines in an inerted tank atmosphere) ensure that the product is received at loading or at discharge port. The quantity should be approximately 10 M3 per tank, depending on the tank size.

If a chlorinated solvent is used as the tank cleaning medium (when portable tank cleaning machines have to be used for tank cleaning or when cleaning Isocyanates other than TDI) ensure that the product is received before discharging the cargo. The quantity should be approximately 10-15 M/T per tank, depending on the tank size. The moisture specifications of chlorinated solvent should be less than 400 ppm.

For line cleaning after loading (regardless the cleaning mediums selected for the tank cleaning), ensure to order sufficient quantity of toluene (drums). To calculate the quantity to order, calculate the capacity of the cargo transfer line system including the crossover.

For personal protection and spill neutralization, ensure to have on board 2 drums (2 x 200 litres) of Isopropyl Alcohol (IPA), before the loading.

For personal protection and spill neutralization, ensure to have on board 1 drum (200 litres) of Aqua Ammonia, before the loading.

For personal protection (decontamination of protective gear), ensure to have on board two spray cans (garden type can of approximately 20 litres capacity), before the loading

For personal protection including cleaning of personal protective gear ensures to have 1% Tincture of Green Soap. 14 Ensure to have valid vapour test tubes and medications according to regulations (IMO MFAG).

Ensure to have on board the equipment for maintaining and monitoring the nitrogen blanket.

As steam or hot water cannot be used as the heating medium for isocyanates, arrange for suitable heating capability. This might be thermal oil or adjacent compatible cargoes. Prevent stowage of adjacent "cold cargoes" that may cause solidification of Isocyanate on the bulkheads/tank top.

Preparation before loading

Check with the Ship Operator if the particular customer requires tank cleanliness beyond water white standard.

Heating coils to be tested. Finally (when thermal oil is not used as heating medium), blow the heating coils with nitrogen and blank them off.

Cargo pump(s) cofferdam to be purged with nitrogen and filled with Dioctyl Phthalate (DOP).

As the cargo is reacting with water/moisture it is extremely important to have the tank, cargo line system, tank venting system, fixed tank cleaning machines, level gauging systems (coamings & floats), level alarm systems (tubes & floats), any drain cocks or drain plugs in valves and line systems completely free from water before commencement of nitrogen purging.

The cargo should not be stowed adjacent to tanks containing water.

Tank(s) to be fitted/equipped with tank pressure gauge(s

Prepare for N2 purging and blanketing. Sufficient high pressure hoses and regulating valves must be on board and pre-rigged.

Prepare for vapour return to shore.

Install the specially sampling device (if required). Sampling is often done by cargo surveyor at the pump stack.

Tank(s) to be battened down and pressure tested

Leaking packings, etc., must be renewed. Ensure that the P/V valve(s) operates properly.

If not loading through the ship's manifold, install an SS valve with the blind flange on the pump stack fitted with N2 connection.

If loading through hoses Hostaflon or Chemflex hoses should be used. Do not use stainless steel hoses. There should be a double valve at the pump stack. There should be a valve at any "Y" pieces so each section can be blown individually. There should be a valve between the shoreline valve and the ship's portable line.

A valve must be fitted at each outlet in use so each line can be blown to the tank individually. If this method is used then the ship staff must be completely satisfied with the integrity of all valves on the system. At the end of the loading it must be ensured that no trace of product is left in the lines or cross-overs.

Final loading preparation

Follow procedure in "N2 purging of lines and tanks". Purging will continue until the dew point in the tank has been reached as governed by regulation contained in the IBC/BCH code (minus 40°C.) for dry tank environment. Before commencement of loading, following must be arranged and observed:

The affected loading area must be roped off.

All crew on board must be notified of the danger and t hose not directly involved in the loading instructed to stay away from the loading area.

Communication links between ship/shore and on board must be tested and agreed upon.

Safety showers and eye washes must be tested and under pressure.

One drum (55 gal.) of the neutralizer (50% IPA, 10% Aqua Ammonia, and 40% water) must be placed close to the loading area ready with barrel pump and spray hose of sufficient length to cover the entire loading area.

Two spray cans of neutralizer for personal decontamination (99% IPA and 1% tincture of green soap) must be readily available.

Isocyanate vapour test (Draeger) tubes must be available and used on and around the loading area during the loading.

After loading

When sampling, upon completion of loading, use the portable closed sampling device.

When loading is completed and cargo samples taken, the line must be blown with N2 from shore for at least 15 minutes. For final line clearing (ship's responsibility) follow the line clearing procedure in the Cargo Handling procedures.

If loading more than one tank, be sure that each line is blown independently, also for 15 minutes.

If any spill occurs during hose disconnection, spray the area immediately with the neutralizer.

When the line clearing has completed (all valves and flanges closed) secure the pump stack valve in closed position with a rope or wire.

Without allowing air/moisture into the cargo line, immediately after line clearing, fill the cargo line (from the pump stack to the manifold headers) with toluene. Leave the toluene in the line for 3 days. During the 3 days period, operate the valve in the manifold crossover (without removing the end flanges) to dissolve trapped Isocyanate residue. Before draining the cargo line, operate all drain cocks while flushing some toluene into a bucket.

Upon completion of draining the cargo line, thoroughly blow the cargo line with nitrogen without allowing air/moisture into the line system. Secure the line, unsecure the pump stack valve Different operators have different ways of handling the cargoes, therefore it is in order to have the cargo lines blown through with Nitrogen and also kept under Nitrogen pressure for the loaded passage.

A second option is to blow through the lines with Nitrogen and then keep it under Nitrogen pressure for the entire voyage. Nitrogen utilised for this will be on the charterer’s account.

Discharging Isocyanates

The same safety precautions must be taken as during loading.

When discharging, the tank must be inerted with N2 from shore during the entire operation (via the vapour return line). Refer to Section 9.9 of these procedures.

For efficient stripping and line clearing use Nitrogen.

4. If any spill during disconnecting of the shore hose occurs, spray the area immediately with the neutralizer.

Cleaning & slop disposal / Isocyanates - Cleaning from TDI using gas oil

This cleaning procedure may only be used in cargo tanks that are fitted with fixed tank cleaning machines. However, if portable equipment is used, sufficient inert gas or nitrogen must be available to keep the tank(s) inerted throughout the operation.

Ensure that the gas oil is handled/stored under dry conditions (e.g. dry lines and storage tank).

To remove possible water in the gas oil, it is advisable to flush some product into a drum before entering the tank to be cleaned.

To obtain good cleaning results, the gas oil may have to be pre-heated (above the freezing point of the TDI but always remain below its own flash point of 38C).

Before adding the gas oil, the tank must be tested for oxygen content; one meter below the deck level and at the middle of the tank height.

If the measured oxygen level exceeds 8% then the tank must be purged with nitrogen to below 8% prior to proceeding further. (If nitrogen is unavailable locally then the tank should remain closed until sufficient nitrogen can be supplied).

Once the safe oxygen level is measured (below 8%), a sufficient quantity of gas oil usually 5-15 M3 depending the actual tank size) is added to the tank to be recirculated.

Prior to commencing recirculation, supply and maintain a positive N2 pressure throughout the cleaning operation. (Closely monitor the positive). If portable equipment is used a continuous flow of inert gas or nitrogen must be piped into the tank.

When re-circulating, via the pump stack or manifold, all fixed tank cleaning machines must be used.

Recirculate the gas oil for a minimum of 2 hours.

Vent line, cargo line, drop line and stripping line must also be flushed with gas oil as part of the cleaning procedure.

Upon completion of recirculation the tank may be "electrically charged" and must therefore, be allowed to sit for a minimum of 30 minutes before transferring the gas oil.

The gas oil mixture may be reused in additional tanks by repeating the above procedure. (Four parts of gas oil are required to dissolve one part of TDI).

Cleaning from Isocyanates using chlorinated solvents

This cleaning procedure is used when cleaning from Isocyanates such as MDI, PAPI and TDI, with exception (for TDI when using gas oil and fixed tank cleaning machines).

Ensure that the tank lining is resistant to the particular chlorinated solvent being used. (Some coatings e.g. Phenoline and Devchem 253 are not resistant to MEC).

Ensure that the selected chlorinated solvent is handled/stored under dry conditions (e.g., dry lines and storage tank).

The chlorinated solvent should be heated to a point above the melting point of the Isocyanate to be cleaned. Ensure that the temperature of the chlorinated solvent is kept below the boiling point of the selected chlorinated solvent.

Transfer a sufficient quantity (approximately 10 M3) into the tank to be recirculated.

Prior to placing the portable cleaning machines, supply and maintain a positive N2 pressure throughout the cleaning operation. (Closely monitor the pressure).

When re-circulating, via the pump stack or manifold, all tank cleaning machines (as fitted or each section) must be used.

Recirculate the selected chlorinated solvent for a minimum of 2 hours.

Vent line, cargo line, drop line and stripping line must also be flushed with chlorinated solvent as part of the cleaning procedure.

Chlorinated solvent may be reused in additional tanks by repeating the above procedure.

Cleaning from TDI using water

Safety is always first and everyone onboard is to be made aware and given specific guidance on precautions that the Shipboard Management Team has put in place.

TDI is to be discharged via the pump stack connection. If this is not possible then after the discharge the ship’s line will be cleaned, using Toluene or other solvent as per normal procedure. This may require some slight modifications to the stripping line system onboard, to ensure the tank is properly stripped.

After discharge is completed ensure the tank is properly stripped. If for any reason the tank cannot be properly stripped consult the Ship Operator before cleaning.

Once the tank is confirmed to be properly stripped (dipped and/or sighted ensuring proper safety measures are taken if in doubt) cargo lines, vent lines, stripping lines, and fixed tank cleaning machines must be blown with nitrogen to ensure all free liquid has been removed.

Ensure heating coils are free of product and blanked.

Ensure pump cofferdam is filled with DOP throughout the entire time.

It is very important that the tank is kept tight and under positive nitrogen pressure until the actual cleaning is performed.

Ensure only the designated people that are required to carry out the operation are allowed in the vicinity, with the proper safety gear throughout the entire cleaning operation.

Prior to introducing any water to the tank the cargo pump should be turning over at slow speed. Once washing starts the pump speed should be adjusted as per normal cleaning operations.

It is important that as much ambient temperature water (but above the melting point of the TDI which is approx 19c) is introduced at the initial cleaning stage. To ensure sufficient quantity and coverage, it may be necessary to supplement fixed cleaning machines with portable machines.

Ensure all associated equipment lines, drain cocks, valves etc. are cleaned during the initial cleaning.

The slops are to be disposed of as per regulations.

The tank should be washed for a minimum of six hours with fresh or saltwater. Since TDI is not water-soluble this will ensure that all TDI has been displaced from the tank.

Once the tank is gas free, dry, and confirmed safe it should be inspected and advise the Ship Operator of the results.

The above procedure has proven to be a useful alternative to Chlorinated Solvent re-circulation when there is time at sea for cleaning.

A sufficient amount of water is the key. Please consider this as if you were using MEC and then cleaning after. If you re-circulated four hours with MEC and washed four hours after that, then you should be washing with water for eight hours. The above procedure shows six hours, this should be the minimum wash time. It is not uncommon to have traces of white powder remaining in shadow areas. These areas should be dealt with immediately using white spirit. One should avoid spraying or wiping with alcohols or ketones, as these will encourage any reaction, making removal more difficult.

Experience has shown when larger amounts of white powder are left over; chlorinated solvent re- circulation will remove any left over areas.

We have summarized below some of the special chemical cargoes frequently carried onboard chemical tankers

Handling benzene & methanol safety precautions

Handling carcinogens requirements for certain chemical cargoes

Handling ACRYLONITRILE safety precautions

handling ISOCYANATES safety precautions

handling Sulfuric acid safety precautions

handling Phenol safety precautions

Requirements of various grade chemical cargo heating

Handling benzene & methanol safety precautions

Personal protective equipments for carcinogens & cyanide-like cargoes onboard chemical tankers

Following detail pages explain all liquid chemical hazards & precautionary measures while carrying at sea.

Following reference publications provide useful guidance and international regulations for carrying hazardous chemicals at sea.

SOLAS (latest consolidated edition)
MARPOL – 73/78 (latest consolidated edition)
BCH / IBC Code
International Safety Guide for Oil Tankers and Terminals (ISGOTT)
Tanker Safety Guide (Chemicals)
Ship to Ship Transfer Guide (Petroleum)
Safety in Oil Tankers
Safety in Chemical Tankers
IMDG Code
Supplement to IMDG Code (Including MFAG and Ems)
SOPEP
Clean Seas Guide for Oil Tankers
FOSFA (for Oils, Seeds and Fats)
Prevention of Oil Spillage through Cargo Pumproom Sea Valves
CHRIS Guide (USCG)
Chemical Data Guide for Bulk Shipment by Water (Condensed Chris)
MSDS for particular cargo carried
Chemical Tank Cleaning Guide

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