16/02/2019
Storage of goods in terminals and warehouse
Following are good practices guidelines:
Knowledge of the requirements of the cargo terminals
Calibration of tanks
Certificates for degassing
Cleaning certificate
Cargo terminal are required to maintain safety and security to ensure the cargo is not tampered with. Place is required to stack the containers. Lifts, movable hoists are required to lift the containers in designated place while loading. Procedure is required to accept the container in to terminal and exit of the container from the terminal. Some goods required fumigation and relevant certificates need to be produced. Cleaning and calibration certificates are required for storage and handling of various liquids.
Calibration of tanks:
Following are the methods to calibrate the tanks as under:
MANUAL STRAPPING
The manual strapping method involves strapping each ring of a tank with a certified tape. As the tank diameters and the tank heights increase it becomes difficult to tape the tank uniformly due to tape sag, tank indentations, and the limited length of tapes. Nonetheless, it is a popular method, and may still be a cost-effective application in many cases.'
LIQUID CALIBRATION
Liquid calibration is considered the most accurate and the most preferred method of calibration where and when possible. This method consists of metering a known quantity of liquid and gauging the tank at regular height intervals to develop a capacity table. It is time consuming and may not lend itself for easy and quick application. However, under certain circumstances this may be the only available option for calibration.
OPTICAL REFERENCE LINE
The optical reference line method, which can be applied internally or externally, uses an optical theodolite to establish a perpendicular ray in a vertical plane.'
With this optical ray, the deviations in the tank diameters at various course heights are measured with respect to a reference offset at the bottom course.
In addition, the reference circumference is measured at the bottom course. These deviations together with the reference offset and the reference circumference are then translated into appropriate tank diameters.
OPTICAL TRIANGULATION
Optical triangulation can be applied internally or externally.4 The principle of this method is that a tank profile can be defined by triangulation with two theodolites and a target point on the tank, or with one theodolite and two target points on the tank at a number of stations around the tank.
For external application, depending on the tank height, a minimum space around the tank will be required to apply this method. This method, already in use in some countries, is in the final stages of standardization within the International Standardization Organization (ISO).
ELECTRO OPTICAL DISTANCE RANGING
Electro-optical distance ranging currently under development towards standardization within ISO, is primarily intended for internal calibration. With 'a single optical laser, and a distance ranging device and on-line computer, circumferential target points on the tank shell wall, for any given course, are mathematically and statistically analyzed almost instantaneously to give the required course diameter. The calibration can be accomplished from the ground level by one person. This method is presently in use in Europe.
SELECTION FACTORS
The type of calibration method that one may select may often be dictated by a number of factors. These factors are broadly grouped into the following:
• Type of tank: floating or fixed roof
• Operational constraints: entry or no entry
• Insulation or no insulation
• Riveted or welded
• Other parameters such as number/size of wind girders.
Three Basic Rules for Calibration:
The following basic instrument calibration rules ensure a clear path to health and safety.
@ Follow the manufacturer‘s guidelines for proper calibration. No job, including instrument calibration, can be performed properly or safely without the right tools. The type and concentration of calibration gas, sample tubing, flow regulators, and calibration adapters are key links in the calibration chain. Using equipment provided by the original manufacturer should ensure a proper start to every calibration.
@ Use only certified calibration gas before its expiration date. The most important tool used in calibration is the gas itself. The instrument can only be as accurate as the gas used to calibrate it. Be certain your supplier can provide a traceable certificate of analysis for every calibration gas cylinder. The concentration of calibration gas, particularly the concentration of reactive gases such as hydrogen sulfide or chlorine, will remain stable only for a finite period of time. Never use calibration gas after its expiration date.
@ Train workers on the proper methods of calibration. Most instruments are designed to be field calibrated with instructions detailed in user manuals, training videos, or computer-based training modules. Everyone responsible for performing instrument calibration should be trained and tested accordingly.
