Tank Cleaning Recommendations
Never open and ventilate several tanks at the same time. All normal safety precautions must be taken. (No smoking, accommodation ventilation on recirculation etc.) To the air: As always when ventilating, special care must be taken to prevent the risk of explosion (flammable products) or with regard to toxic vapors. The wind strength and wind direction must also be a decisive parameter for the Master to allow ventilation. To avoid a buildup of explosive or toxic vapors on deck the amount of gas to be escaped from the tanks should be limited. Never open and ventilate several tanks at the same time.
Tank Cleaner Fast Running
Rxsol Chlorox or Bleach Substitute
Description: Bleach, which is also referred to as RXSOL-Chlorox , is a strong oxidizer. These products become more aggressive with temperature increase, and should not be allowed to dry on tank walls or stored in cargo tanks as cleaning solution or slops.
Rxsol Chlorox will –
- Remove odors.
- Remove color.
- Improve permanganate time.
Spraying: Following rough washing to a good Water White or better, apply dilute Bleach to 1 – 3% strength. First wet the tank surface (spray with DI water), then spray all over with Bleach, wait 30 minute (but do not allow to dry) and then rinse very well with DI water, including the tank top towards the sump. To ensure that you have covered all areas properly, this process should be carried out at least twice with good DI water.
Re-circulation: Following rough washing to a good Water White standard or better, apply dilute Bleach to 1-3% strength. Mix sufficient Bleach with fresh water in the tank and heat this mixture to 40 – 50degreeC, circulate through the drop line if fitted and than circulate through butterworth machine for 3 hours. After re-circulation immediately warm butterworth to (50 degree C) the tank for 3 hours at maximum pressure, increase the water temperature to 80-85 o C after 45 minutes. Check (by smell) that there is no Bleach remaining, then fresh water rinse and dry.
When there are a number of tanks requiring re-circulation, it may be significantly more efficient to make up a large batch or number of batches that can be transferred on between tanks as required.
Use a strainer at the pump stack when circulating any solution.
Tank Lining – Stainless / Zinc / Epoxy / Phenolic (Extreme care must be taken if product other than bleach substitute is to be used in any coated space).
Mek or Acetone
Description: Methyl Ethyl Ketone and Acetone are both non-static generators and can therefore be sprayed using a barrel pump. *Always check the quality of the product before using inside a cargo tank.
Spraying: When the cargo tank has been cleaned to a point where there are very slight hydrocarbons showing in the Wall Wash, then MEK or Acetone can be used to remove these small amounts of residue. The spraying should only take place if the tank is very dry. Following spraying, eject and ventilate and re-check the Wall Wash.
Re- circulation: No.
Tank Lining: Stainless / Zinc / Epoxy / Phenolic
Description: This is a non-static generator and can therefore be sprayed using a barrel pump. Always test the Methanol in the drum before use for color/odor/hydrocarbon/chloride and permanganate time.
Methanol not a good cleaner and therefore should not be wasted on tanks that are showing anything above a very light trace of hydrocarbons.
Spray: Tanks which are showing dampness can be sprayed with Methanol a short period to presentation for Wall Wash as product will dry the walls quickly and hold them in that condition for at least 1.5 hour. Tanks showing a very light trace of hydrocarbons can also be sprayed down with Methanol, but you must be aware that, depending upon the type of hydrocarbons, there may be little or no improvement. Methanol will not dissolve chlorides: use DI water for this purpose. Methanol will help improve permanganate time, but only a little and any improvement will generally not last very long.
Re – circulation: No.
Tank Lining: Stainless / Zinc / Epoxy & Phenolic
Description: A colorless liquid with a Benzene like odor. It has a density of 0.866 at 20 0 C, a flash point of 6 0 C, boiling point of 1110 C and auto ignition temperature 5360 C, with a vapor pressure of 29 mbar at 20 degrees and pollution category “C” Toluene is one of the most static generating products, and all care must be taken when handling this product with regard to bonding of transfer equipment and tank cleaning equipment. Always check the solubility of the pervious cargo residue with Toluene before using it in the cargo tank, because it may not be soluble and you may therefore need to use an alternative method of cleaning. Toluene can be supplied in 210 liter drums of in bulk.
Toluene supplied in bulk can be placed directly into one of the tanks to be “floated”, after the tank has been rough washed . Either hook up the loading hose to the cargo line, or lower a smaller hose down into the tank, close to the bottom. Transfer by this second option should only be by gravity and great care should be taken to ensure that the end of the hose does not whip about, generating a statically charged spray or a spark by striking tank sides or fittings. The hose should not be disconnected until it has been removed from the tank after the transfer. Any equipment used with Toluene must be checked for conductivity before being used. Example Butterworth machines, hoses, and portable blowers etc.
Toluene Floating: This is an efficient method of bringing even the worst coated cargo tank close to a Wall Wash standard, if carried out properly. The ship should be trimmed in such a way that when you fill the Toluene, it covers the tank top to approx 10 centimeters. In this way, it will touch all the tank surfaces when it moves up and down. The same Toluene can be used for many tanks, and still maintain its power. Once the Toluene is in the first tank then – Fill ballast into the tank through the cargo line or drop line or drop line until the tank is approximately 95 % – 98 % full. Where possible, the ballast should be warm 400 C.
Use a line type float tap or remote ullage equipment to check level in the tank. Discharge the water slowly. Careful attention to detail and clear instruction to those involved on how to proceed must be given, otherwise the desired results may not be achieved. Make sure that when transferring the ballast out of the ship, personnel must have an ullage to work to for transferring into the next tank, or holding tank, thereby avoiding losing the Toluene overboard. Once the transfer changeover is made, then ambient followed by hot washing for 45 minutes and stripping continued into the holding or next tank.