Limitations of presently available Cargo Tank Portable Level gauging devices:
During a recent correspondence with the makers of Portable tank gauging instruments, it has been highlighted that so far no UTI's are available on the market for use on corrosive liquids, such as Sulphuric acid. Majority of the UTI's are IIB classified, while for gauging acids, IIC classified products are required.
Enraf Honeywell GTEX UTImeter have come up with a specific sensot, called Ultra sensor, which can withstand specific chemicals, such as acids. This special sensor would be able to stand sulphuric acid without any comparison with the standard sensor considering however that this part as the rest of the device shall be cleaned with an appropriate solution after every measuring campaign to neutralize the corrosive effect of this acid. However, this sensor is still IIB certified.
Below from the makers of Enraf:
Quote----
Lastly, I would like to highlight that:
- our STANDARD SENSORS DO NOT WITHSTAND and MUST NOT BE USED TO GAUGE SULPHURIC ACID. Only specific sensors equipped with a beige sensor head equipped with a metallic cap can withstand sulphuric acid (difference between standard Ultra sensors and specific sensors for specific chemicals).
- Referring to IBC Code, Section 11.5 Acids, our units shall not be used to gauge sulphuric acid. I recommend anybody to assess the suitability of our devices before using it to gauge acids and more specifically sulphuric acid. See attached letter.
- The units must be cleaned after every measurement campaign with an appropriate solution to neutralize the acids
----- Unquote
On a seperate issue, for Bitumen / Asphalt carriers, vessel's carrying cargoes at higher temperatures, like 150 DegC +, it is important to understand that all UTI's presently available in the market are only capable of measuring upto 90 DegC.
In short, there are no gas-tight device available off the shelf, as yet for using for measuring ullage / temperatures at high temperature. Asphalt temperatures could be as high as 180 Deg C.
In such case, it will be better to have onboard a Closed Sounding tape for ullaging only.
Further, for temperature measurement, that is where the real problem lies. For this, the best possibilities are (unless the UTI maker can provide an alternative solution – awaiting the details) to take a sample of the cargo, using the closed sampler and use a Marine Thermometer of range of 200 DegC to measure temperature, if need arises, with Risk Assessment done prior to usage. However, mostly in such cases, the tank fixed thermometers are always preferred and predominantly used, and thus it is imperative that the system is kept calibrated and serviced as soon as a problem is discovered.
Hope you’ve some spare temperature sensors for the system on board. If not, it may be prudent to request for a few standby sensors.
All I can think of is a modified system made of a normal brass marine thermometer of range upto 200DegC connecting to a normal sounding tape (minus the bob / weight) and inserted in the tank, if required, on each occasion through the vapor locks.
Further, understand, these thermometers will require to be yearly calibrated, preferably ashore or by a calibrated standard temperature device onboard to cover up SIRE / cargo surveyor requirements.
During a recent correspondence with the makers of Portable tank gauging instruments, it has been highlighted that so far no UTI's are available on the market for use on corrosive liquids, such as Sulphuric acid. Majority of the UTI's are IIB classified, while for gauging acids, IIC classified products are required.
Enraf Honeywell GTEX UTImeter have come up with a specific sensot, called Ultra sensor, which can withstand specific chemicals, such as acids. This special sensor would be able to stand sulphuric acid without any comparison with the standard sensor considering however that this part as the rest of the device shall be cleaned with an appropriate solution after every measuring campaign to neutralize the corrosive effect of this acid. However, this sensor is still IIB certified.
Below from the makers of Enraf:
Quote----
Lastly, I would like to highlight that:
- our STANDARD SENSORS DO NOT WITHSTAND and MUST NOT BE USED TO GAUGE SULPHURIC ACID. Only specific sensors equipped with a beige sensor head equipped with a metallic cap can withstand sulphuric acid (difference between standard Ultra sensors and specific sensors for specific chemicals).
- Referring to IBC Code, Section 11.5 Acids, our units shall not be used to gauge sulphuric acid. I recommend anybody to assess the suitability of our devices before using it to gauge acids and more specifically sulphuric acid. See attached letter.
- The units must be cleaned after every measurement campaign with an appropriate solution to neutralize the acids
----- Unquote
On a seperate issue, for Bitumen / Asphalt carriers, vessel's carrying cargoes at higher temperatures, like 150 DegC +, it is important to understand that all UTI's presently available in the market are only capable of measuring upto 90 DegC.
In short, there are no gas-tight device available off the shelf, as yet for using for measuring ullage / temperatures at high temperature. Asphalt temperatures could be as high as 180 Deg C.
In such case, it will be better to have onboard a Closed Sounding tape for ullaging only.
Further, for temperature measurement, that is where the real problem lies. For this, the best possibilities are (unless the UTI maker can provide an alternative solution – awaiting the details) to take a sample of the cargo, using the closed sampler and use a Marine Thermometer of range of 200 DegC to measure temperature, if need arises, with Risk Assessment done prior to usage. However, mostly in such cases, the tank fixed thermometers are always preferred and predominantly used, and thus it is imperative that the system is kept calibrated and serviced as soon as a problem is discovered.
Hope you’ve some spare temperature sensors for the system on board. If not, it may be prudent to request for a few standby sensors.
All I can think of is a modified system made of a normal brass marine thermometer of range upto 200DegC connecting to a normal sounding tape (minus the bob / weight) and inserted in the tank, if required, on each occasion through the vapor locks.
Further, understand, these thermometers will require to be yearly calibrated, preferably ashore or by a calibrated standard temperature device onboard to cover up SIRE / cargo surveyor requirements.
Good luck guys.
