Frequent asked questions (FAQ) for CALM   Is it necessary with Non-return valves (check valves)? Is it necessary with isolation valves? Which material and tube diameter is recommended? Will the performance of the system be better with larger diameter pipes? What is the Output/Input? How accurate is the system? What is the updating time for each tank? How often it is necessary to purge the pipes? How important is it to have tight pipes? We have problems with traditional type compression couplings. Is there any alternative method? What are the air supply requirements? Is it possible to measure draft, trim and heel with CALM? What is a draft pot and when is it used? Is it possible to measure potable water level? How dry should the supply air be? Our dryer is not working. Can you recommend an economic, sufficient device? Is it possible to measure cargo level by CALM? Is it possible to feed CALM with other gas? Is it possible to measure liquid density? How long time will the PLC store the program?             Q: Is it necessary with Non-return valves (check valves)?  A: The CALM cabinet is connected to tanks via internal solenoid valves. All valves are normally closed and open only during each measurement, it is 3 sec/cycle. If the pressure of the supply air is to low a pressure guard installed in the cabinet switches off the power, measurements are interrupted and all valves remain closed. The valves remain closed even with other type of malfunction, like leakage or PLC defect. As the valves connecting the cabinet and the tank can only be opened with pressure supply higher than liquid pressure, the liquid can never enter to the cabinet, and, assuming that the pipe is tight, the liquid will not even enter the pipe. From the function of the CALM point of view any non-return valves or isolation valves are not necessary. However, for double security, we strongly recommend to use it in every case. The Non-Return Valve will: prevent the liquid to run out in case of damaged pipe prevent the liquid to enter into the cabinet, regardless of its position re highest water level allow to disconnect pipes without risk for water backflow. The non-return valve shall be mounted in vertical position. If a non-return valve is supplied from other source than Kockum Sonics AB, please contact us for conformation. Some of the valves with forced closing may cause unacceptable large pressure drop.         Q: Is it necessary with isolation valves? A: Similar to the non-return valves, from the function of the CALM point of view any isolation valves are not necessary. However, in case of very long storage without air supply, in order to simplify service and in case of any uncertainty, it is recommended to install a simple manual ball valve on each tank. It should be placed as close to the tank as possible. In case where the penetration to the tank is made under the highest level of liquid (side penetration) isolation valve is required (DNV).         Q: Which material and tube diameter is recommended?  A: Ballast Oil   Top penetration Side penetration Top penetration Side penetration  Non-return valve  Not requested but recommended if cabinet or plastic tubes are placed below  highest liquid level.  Isolation valve  Recommended  Requested  Recommended  Requested  Dip pipe  PA with end  piece in metal  PA with end  piece in metal  Steel 1”  Steel 1”  Pipes between  cabinet and dip  pipe (deck pipe)  L <100 m Ø10/8  L >100 m Ø12/10  PA or metal  Metal to highest  level  PA or metal  Metal to highest  level Notes: • For installations in hazardous areas follow appropriate regulations. • In tanks adjacent to crude oil tanks the dip pipe shall be of metal. • Tubes on deck in oil- chemical- or gas carrier shall be of metal. • For measurements in other liquids the dip pipe shall be made of appropriate material. • Non-return valves shall be mounted in vertical position. • At side penetration pipe to highest level or to non-return valve shall be of metal. The complete installation kit with absolutely tight press fittings is available in stainless steel (AISI 316), copper and plastic.       Q: Will the performance of the system be better with larger diameter pipes? A: No, in contrary. The pipe inner diameter must not have bigger diameter than recommended, i.e. 8 mm for pipes < 100m, 10 mm for pipes > 100m. Too big diameter is more difficult to tighten. Use copper, or if allowed, plastic pipes in longest possible pieces.         Q: What is the Output/Input? A: The PLC transmits the measured signal with its address via an RS 485 port (RS 232 optional) to several display units (DU 350), PC or other displays or systems. When requested, analogue outputs/inputs (4-20 mA) can be provided.         Q: How accurate is the system? A: The standard cabinet is equipped with pressure sensors with nominal pressure of 4b, which gives the standard measuring range of 30 m (water). In order to improve the accuracy, the system may be fitted with 2b pressure sensor, but the measuring range is than limited to 15 m. The max inaccuracy of the system is ± 0.3% of full range (that is 12 resp 6 cm water) The typical system accuracy for 98% of all measurements is ± 2 cm.         Q: What is the updating time for each tank? A: In the standard version the time between measurements on the same tank (updating time) is 30 seconds. If necessary, the updating time can be reduced to 15 or 10 seconds, individually for every tank.         Q: How often is it necessary to purge the pipes? A: Any manual purging is not necessary. At pre-programmed intervals the PLC controlled Blowing Through Valve sc purge valve bypasses the choking hole and blows the pipe clear of any debris. Each tank is cleaned on a 24 hourly cycles as standard. Please contact Kockum Sonics if other intervals should be preferred. In order to utilize all available air capacity, only one tank is blown at a time.         Q: How important is it to have tight pipes? A: The tightness of the pipes between the cabinet and the tank is essential for the proper measurements. In order to check the tightness each pipe should be equipped with an isolation valves (simple manual ball valve) as close to the tank as possible. With closed isolation valves, the air pressure in the pipe should remain on the nominal level, see also pre-commissioning test.         Q: We have problems with traditional type compression couplings. Is there any alternative method? A: A very reliable and fast method based on press fittings can be applied to the pipes used in our case. The press fittings are installed by means of an electrical tool, which gives always the same pressing power. The built-in O-rings guarantees absolute tightness. The fittings are very simple and much cheaper than any other couplings. This, together with very short connection time makes the entire installation very economical. The press fittings are available in stainless steel (AISI 316) and copper. See also our instructions on the support page.   For plastic tubes we can offer very reliable, vibrations proof push-in couplings. The fittings may be purchase separately or in installation kits complete with tube, valves etc.         Q: What are the air supply requirements? A: The air for the level gauging system must be of instrument quality, free from oil and moisture and filtered to not more than 25 microns. Wherever possible the system should be provided with a primary air supply from an independent compressor and reservoir, together with suitable air-drying and filtration plant, used only for the gauging equipment. The air pressure should not be lower than 150 % of the nominal pressure (3 or 6 b) and not higher than 10 b. The air consumption during measurements is not higher than 0.5 l/min/tank and during purging (blowing-through) 5 l/min/tank. The average air consumption is 0.1 l / min / tank.         Q: Is it possible to measure draft, trim and heel with CALM? A: Similar to tank measurements, the draft measurement pipe can be connected via a shut off valve (Shipside valve) directly to the ship’s hull. The most common measurement of draft is in four points, but it is also possible to measure with three points, two points with one inclinometer or one point with two inclinometers. The CALM unit is carrying out measurements only, calculation and display DU 350, KSL 450 or other computer shall perform presentation.         Q: What is a draft pot and when is it used? A: The draft pot is a device connected with seawater and vented to atmosphere. This device was formerly used for draft measurements by means of electronic pressure transmitters possible. It is not required whit CALM, but, if exists, CALM can naturally be connected to this device.         Q: Is it possible to measure potable water level? A: When it is not desirable to introduce air into a liquid such as potable water, the pressure repeater can be installed. Pressure repeater is made of stainless steel (AISI 316) and PTFE (Teflon) isolates the air side from the liquid side, pressure on both sides is equal.         Q: How dry should the supply air be? A: The CALM cabinet is equipped with a very fine oil and particle removal filter (0.01μm). This filter is sufficient for air with normal content of water, oil and impurities. The humidity of air is not critical when its dew point is below the ambient temperature. If the cabinet is placed indoors, air with dew point below 15°C does not require any additional treatment. However, when the dew point is higher or, even worse when the air contain liquid water, the built-in filter will be fast filled up und its function will be jeopardized. Therefore, in such case, the water should be removed from the air, and at dew point higher than 15°C, the air should be dried.         Q: Our dryer is not working. Can you recommend an economic, sufficient device? A: Kockum Sonics can provide a simple, economic air treatment device especially projected for CALM. The unit consists of a general-purpose filter with automatic drain, an oil removal filter and membrane water vapour removal filter. The device will reduce the supply air dew point to below 15°C, depending on air consumption.         Q: Is it possible to measure cargo level by CALM? A: Yes, from CALM point of view it does not mater what is the tank content, as far as it is in liquid form. If air is not desired, CALM can be driven by e.g. nitrogen. For very accurate measurements, CALM can be equipped with difference pressure sensors.         Q: Is it possible to feed CALM with other gas? A: Yes, providing the gas is clean, dry and not explosive (see also air supply requirements)         Q: Is it possible to measure liquid density? A: Yes, simply by measurements of pressure in two points placed in fixed and known vertical distance from each other.         Q: How long time will the PLC store the program? A: The CPU 214 programmable logic controller is completely maintenance-free. That is, the program and various default values, such as password, station number, and some of the data are permanently stored in EEPROM. A super capacitor provides short-term storage of all retentive user data, such as calibrations. The capacitor’s storage time is typical 200 hr (powerless). If the retentive data shall be stored for longer time, an optional battery cartridge with 200 days continuous use can be installed. Therefore, from the CPU’s point of view any software for reloading is not necessary. If the CPU will loss the memory stored in EEPROM, the whole CPU has to be exchanged. The battery cartridge can be useful if there is expected shut off time longer than 200 hours. However, even if the CPU will loss the memory stored in the super capacitor (after 200 hours without power), the retentive data can be restored by simple manual recalibration.