HEATEC TEC-NOTE. Setting Siemens Pressure Transmitter. Used on Heatec Vertical Asphalt Tanks. Publication No , Revised

Transcription

1 HEATEC TEC-NOTE, Revised Setting Siemens Pressure Transmitter Used on Heatec Vertical Asphalt Tanks This document provides information on setting Siemens pressure transmitters used on Heatec vertical asphalt tanks TAV-10, TAV-15, TAV-20, TAV-25, TAV-30 and TAV-35 (Figure 1). These tanks are used to store liquid asphalt. The transmitter indicates the level of liquid material in the tank. This document covers Siemens pressure transmitter SITRANS P, 7MF4133-1CA70-1NC6-Z B21+M43+Y01 (Figure 2). It is the transmitter model used by Heatec starting in September This document also covers Siemens pressure transmitter SITRANS P, 7MF4033-1CY10-1NC6-Z+B21+Y01 (Figure 3) (fitted with remote seal (sensor) 7MF4810-2QA02). It is the transmitter model Heatec provided prior to September liquid level display and control. A controller (Figures 12 and 13) is normally used in combination with the pressure transmitter. The controller also indicates the liquid levels and provides important safety controls. Remote displays can also use output signals from the transmitter to indicate liquid levels. Settings for controllers and remote displays are covered in other Heatec Tec-Notes. ISOLATION VALVE MOUNTING FLANGE WITH DIAPHRAGM PRESSURE TRANSMITTER Instructions in this document are the same for both transmitters unless noted otherwise. The information herein should enable operators to enter settings into the transmitters after the tanks are delivered to locations where they will be used. This document also provides information for converting levels to gallons. The transmitters have a sensor diaphragm in their mounting flange (Figure 2). Liquid pressure against the diaphragm is converted into a 4 to 20 ma (milliampere) output signal for ENGRAVED PLACARD Figure 2. Siemens pressure transmitter used September 2013 and later. DO NOT TILT TRANSMITTER Figure 1. Heatec vertical asphalt tanks. Figure 3. Siemens pressure transmitter used prior to September 2013.

2 QUICK CHECK When we install pressure transmitters on new asphalt tanks at our factory we program them for asphalt cements that have a specific gravity of 60 degrees F adjusted to for a storage temperature of 300 degrees F. These settings should enable the transmitter and its related controller to provide level indications very close to actual levels in the tank. When you first put the new tank into service, you should verify that our factory settings provide level indications with the accuracy you need. Verify the accuracy as follows: 1. Before putting asphalt into the tank, open the isolation valve (Figure 2) to vent the diaphragm to atmosphere and release trapped air. 2. Partially fill the tank (about 36 inches below the top) with asphalt and allow the transmitter to heat up from contact with the asphalt. 3. Note the level shown on the transmitter display. (Levels are displayed in inches as shown in Figure 4.) 4. Using a measuring tape for inches, determine the actual level of asphalt above the bottom of the tank. For instructions on how to measure actual levels refer to the information under the heading VERIFYING ACCURACY OF LEVELS. 5. Compare the level shown on the display with that found with the measuring tape. If the level shown on the transmitter display is within an inch or two of the level found with the measuring tape, your transmitter is ready for use as is. If the levels differ more than about two inches, you may want to reset the transmitter according to instructions herein for better accuracy. SETTINGS YOU CAN CHANGE Certain settings of the transmitter can be changed in the field using the magnetic push buttons shown in Figure 5. Settings in Mode 6 allow for adjustment of specific gravity, transmitter mounting height, and maximum tank height. In the past we recommended changing settings in Mode 7 to correct for differences between indications shown on the transmitter and actual level measurements made with a measuring tape. However, we no longer recommend using Mode 7 to correct for such variations. Please refer to the information under the heading Trial and Error for new recommendations. We set the transmitter to display the level of the liquid asphalt in the tank in inches (Figure 4). This is our standard unit of measure for level indications and cannot be changed in the field by operators. A number of other settings are based on inches and would require re-programing for other units of measure. Moreover, we provide tables of information so operators can easily convert level indications into gallons. These tables are based on inches of height and the inside diameter of our tanks. Therefore, we do not set the transmitter for other units of measure or tank sizes except on special orders, which may incur extra programing and costs. ACCURACY If you need to obtain better accuracy than achieved with our factory settings, please consider the following factors: Accuracy is affected by specific gravity of the asphalt, which is also affected by its storage temperature. So, if the specific gravity and/or storage temperature for your asphalt is significantly different from our factory settings, it may be necessary to change Mode 6 settings on the transmitter to obtain more accurate level indications. Accuracy is also affected by the height of the transmitter above the inside bottom of the tank. Mounting flanges of transmitters installed on vertical asphalt tanks at Heatec are centered at a height of 11 inches above the inside bottom of the tank. Mounting flanges of transmitters retrofitted in the field are usually installed at the drain outlet, which is only 2.5 inches above the bottom of the tank. Different flange heights require different Mode 6 settings. We attach an engraved plastic plate on the front of the transmitter (Figure 2) with information that denotes the mounting height and tank height for which the transmitter was programed. Figure 4. Display on transmitter. Page 2 Figure 5. Magnetic push buttons.

3 CONCERN FOR TRAPPED AIR Trapped air between the isolation valve and the diaphragm in the transmitter flange may prevent the liquid asphalt from making proper contact with the diaphragm. This may cause erratic level indications. To avoid trapping air on a new tank, be sure to open the isolation valve for the transmitter before filling the tank with asphalt. When retrofitting a transmitter onto an asphalt tank, always mount it on a shutoff valve. The valve serves to isolate the transmitter if it needs to be removed for any reason. If the transmitter is being retrofitted onto the drain valve of a tank that is already filled with asphalt, trapped air should escape if you slowly open the valve to allow asphalt to make contact with the diaphragm. However, if air remains trapped between the valve and the diaphragm, you will likely see erratic level indications. In that case you will need to do the following: 1. Completely empty the tank. 2. If the drain valve is clogged with asphalt, flush it with a solvent to clear the asphalt. 3. Make sure transmitter is securely mounted on the valve. 4. Open the valve. 5. Refill the tank with asphalt while the valve is open.!warning Do not attempt to purge trapped air by loosening transmitter mounting bolts and opening the isolation valve. This would allow hot asphalt to escape along with the trapped air, endangering anyone it might contact. SETTINGS FOR MODE 6 The following information is intended for checking the existing setting in Mode 6 and changing it for a new specific gravity and/or new storage temperature. Settings in this mode are known as full scale blind settings. These settings can be made at virtually any time no matter how much asphalt is in the tank. A single full scale blind setting combines specific gravity, transmitter mounting height, and maximum tank height. Therefore, the number that appears in the transmitter display does not directly indicate specific gravity. Instead you must use the information in Figures 6 or 7 to see what specific gravity setting was included in this setting. The blind scale settings shown in these figures apply to transmitters used on Heatec tanks and incorporate a wide range of specific gravities. 1. Before changing the setting in Mode 6, determine the specific gravity of your asphalt corrected for storage temperature. Use the information discussed under the heading SPECIFIC GRAVITY to do that. 2. Loosen the cover on the magnetic push buttons of the transmitter (Figure 5) and open it for access to the three push buttons (mode, up arrow, and down arrow). 3. Push the mode button several times until the number 6 appears in the lower left corner of the display. This indicates the transmitter is in Mode 6. The value that appears on the main display is the full scale blind setting. 4. Read the numerical value shown on the main display. Now find the nearest blind scale value in Figure 6 or 7 as applicable, and note the specific gravity for that value. For example, suppose the blind scale number that appears on the display is The closest match in Figure 6 is A specific gravity of is shown for that blind scale value. Figure 6. Specific Gravity Vs Full Scale Blind Setting. (11-inch sensor height) Specific storage temp Full Scale Blind Setting Specific storage temp Full Scale Blind Setting The full scale blind setting is equal to a tank height of 600 inches minus the sensor height of 11 inches multiplied by the specific gravity of the asphalt. Page 3

4 5. If the specific gravity shown for that blind scale reading is significantly different from the one you found in Step 1 above, you need to change this setting. 6. Thus, to obtain a full scale blind setting for another specific gravity, simply choose a specific gravity value shown in Figure 6 or 7 with a value closest to the specific gravity from Step 1 above. Then note the full scale blind setting shown alongside the specific gravity listed. 7. Use the up arrow and down arrow to change the full scale blind setting to the new value you found in the previous step. Secure the cover after making changes. Figure 7. Specific Gravity Vs Full Scale Blind Setting. (2.5 inch sensor height) Specific storage temp Full Scale Blind Setting Specific storage temp Full Scale Blind Setting The full scale blind setting is equal to a tank height of 600 inches minus the sensor height of 2.5 inches multiplied by the specific gravity of the asphalt. SPECIFIC GRAVITY To obtain maximum accuracy of level indications, the transmitter must be set for the specific gravity of the material that will actually be stored in the tank. This must be the specific gravity of the material at the temperature at which it will be stored in the tank. If its specific gravity is significantly higher or lower than that used to set the transmitter, the transmitter will not provide accurate level indications. This could allow operators to overfill the tank or cause coking of the heating coils. Specific gravities vary with the types of asphalt. And the specific gravity of a particular type of asphalt varies with its temperature. If you decide to store a different type of material, or if you change its storage temperature significantly, you need to reset the transmitter. If the specific gravity and/or storage temperature of the material varies only slightly from one tank load to another, you can use a setting that is average for most loads. In that case, the level indications will be slightly less accurate, but may be plenty accurate for your operations. Your supplier should be able to tell you the specific gravity of the asphalt you intend to store in your tanks. The BOL (Bill of Lading) for the truck that delivers your asphalt may show the specific gravity for each load. But be aware that the specific gravity shown on the BOL may be for standard temperature of 60 degrees F, which is not your storage temperature. Or it may only show API (American Petroleum Institute) gravity, which is not the same as specific gravity. Another way to learn the actual specific gravity of your material is to have it analyzed in your own laboratory, if you have one. In any case the known specific gravity at 60 degrees F will have to be corrected to your storage temperature. You can easily do that yourself using the information shown in Figure 8. Just multiply the known specific gravity for 60 degrees F by the multiplier shown next to the temperature that matches your tank storage temperature. For example if the known specific gravity is at 60 degrees F, and your storage temperature is 300 degrees F, use the multiplier of shown in the Figure 8. Thus: times equals 0.949, which is the specific gravity corrected for your storage temperature. If you have difficulty determining the corrected specific gravity for your material, try using one shown in Figure 9. It shows the specific gravities for several grades of asphalt cement at various storage temperatures. However, these are typical and may vary somewhat from actual specific gravities of your material. Page 4

5 Figure 8. Temperature Corrections For Specific Gravities Temperature Multiplier 60 Degrees F Degrees F Degrees F Degrees F Degrees F Degrees F Degrees F Multipliers shown here are from Matls. IM T102C, published by Iowa Department of Transportation Temperature Figure 9. Specific gravities for typical asphalt cements for a variety of storage temperatures. Unmodified Asphalt Binders PG PG PG PG PG PG Degrees F Degrees F Degrees F Degrees F Degrees F Degrees F Degrees F Specific gravities shown in green are for unmodified asphalt binders at 60 degrees F, offered by BP Products North America, published in TDS/US/ Specific gravities at other temperatures were calculated using the multipliers shown in Matls. IM T102C, published by Iowa Department of Transportation. This information is shown for reference purposes only. The specific gravity of your material may vary from those shown here. If your supplier doesn t know the specific gravity of your material you might want to use the specific gravity for PG 52-28, which is an approximate average of those shown. Page 5

6 VERIFYING ACCURACY OF LEVELS You should verify that the asphalt level indications produced by the pressure transmitter are acceptably accurate. You need to use a measuring tape marked in inches to determine the actual level of asphalt above the inside bottom of the tank. To minimize error make the measurement while the asphalt level in the tank is about 36 inches below the top. To find the exact level, measure the empty space at the top of the tank using the measuring tape. (See Figure 10). Then subtract the empty space measurement from the inside height of the tank shown in Figure 11. Note: When making your measurement it is difficult to measure directly from the inside top surface of the tank to the asphalt surface. It is much easier to measure from the bottom edge of the manway to the surface of the asphalt. If you do that you will need to make a separate measurement to determine the distance from the edge of the manway to the topmost surface inside the tank. Then you should add the two measurements together as indicated in Figure 10. Your final answer should match the number of inches displayed on the transmitter and controller, within an inch or two. If the indicated level differs much more than that try and find the cause. Start by checking the full scale blind setting of the transmitter as detailed under the heading SETTINGS FOR MODE 6 to confirm correct settings. Make sure it is properly set for the asphalt actually stored in the tank based on the specific gravity of the asphalt at its storage temperature. Be aware that debris or anything blocking the port where the transmitter connects to the tank will cause erroneous operation of the transmitter. TRIAL AND ERROR In the event that measured levels differ significantly from levels indicated by the transmitter it may be possible to use a trial and error method to bring the two into agreement. You might want to try this method especially when you are not sure about the specific gravity of the asphalt stored in the tank. Please remember that temperature variations can significantly change its specific gravity. So make sure the temperature used for specific gravity is the same as the actual storage temperature. But before proceeding with the trial and error method, carefully recheck your taped measurements and your arithmetic for errors. And then check the full scale blind scale setting on the transmitter to make sure it is correct. ASPHALT SURFACE EMPTY SPACE (A PLUS B) MANWAY A B If the two levels still do not agree, proceed with the trial and error method. It involves nothing more than changing the existing values of the full scale blind setting on the transmitter in Mode 6 (see Figures 6 or 7, as applicable). Either increase or decrease those values in small increments until the displayed level indications agree with the level found with the measuring tape. For example, if the existing value is 559.6, increase it to Or decrease it to Continue this process until you get a suitable match. LEVEL SHOWN ON DISPLAY TANK INSIDE HEIGHT Each time you enter a new value and store it, check the transmitter to see how close it agrees with the level found using the measuring tape. Keep doing this until you get an acceptable match. PRESSURE TRANSMITTER EITHER 11 INCHES OR 2.5 INCHES DEAD ZONE Figure 10. Key distances related to level display. After using this method to attain agreement between the transmitter and measuring tape we recommend that you recheck one against the other several times over a period of a several days. TANK OVERFLOW PROTECTION The pressure transmitter works in combination with the level controller (Figures 12 and 13) to provide overflow protection. Accordingly, the controller automatically shuts off the unloading pump when the material in the tank reaches a level approximately 24 inches from the inside top of the tank. Figure 11. Inside height (inches) of vertical asphalt tanks. TAV-10 TAV-15 TAV-20 TAV-25 TAV-30 TAV Page 6 The tank is also equipped with a high level float switch. It functions as a backup system for the shutoff provided by the controller. The float switch will shut off the unloading pump

7 Figure 12. Controller currently used with pressure transmitter. at a level of approximately 7 inches from the inside top if the controller fails to shutoff the unloading pump. TANK COIL PROTECTION The pressure transmitter works in combination with the level controller (Figures 12 and 13) to prevent coking of the heating coil. Accordingly, the controller automatically shuts off the heat when the material in the tank reaches a level slightly above the tops of the heating coils. DISPLAY LEVELS VS. GALLONS As already noted the transmitter displays levels in inches. You may need to know how many gallons of material that various levels represent. Some error is unavoidable when measuring levels and converting them to gallons of asphalt stored in the tank. Such determinations are not reliable substitutes for metering and calibration equipment. It is important to note that pressure transmitters on Heatec tanks are now set up to display the height of the asphalt above the inside bottom of the tank. Several years ago we set the transmitters to display the height of the asphalt above the location of the transmitter sensor. You should not change the position of the transmitter or the location of its sensor. Doing that would cause all indications to be wrong. The standard height for sensors of transmitters installed at Heatec is 11 inches above the bottom of the tank. (This distance may vary plus or minus 1/4-inch.) Consequently, the transmitter displays inches when the asphalt level is at the same height as the sensor. And when the asphalt level is 11 inches there are approximately 647 gallons of material in the tank. Figure 13. Controller previously used with pressure transmitter. When transmitters are retrofitted in the field they are usually installed in the drain outlet. The height of the drain outlet is 2.5 inches. Consequently the transmitter displays 2.50 inches when the asphalt level is at the same height as the sensor. And when the asphalt level is 2.5 inches there are approximately 147 gallons of material in the tank. But note that the transmitter does not actually indicate asphalt levels lower than the height of its sensor. This is known as the DEAD ZONE (Figure 10). So when the display of a transmitter installed at a height of 11 inches shows 11.00, the amount of asphalt in the dead zone is somewhere between 0 and 647 gallons. And when the display of a transmitter installed at a height of 2.5 inches shows 2.50, the amount of asphalt in the dead zone is somewhere between 0 and 147 gallons. The table shown in Figure 14 enables you to convert levels to gallons. The column labeled inches refers to the numbers that are displayed on the transmitter (Figure 4) and on the liquid level controller (Figure 12). (The number of decimal points that appear on the displays vary, but do not affect accuracy.) It is useful to remember that each inch of liquid level equals about 59 gallons. INSTALLING A NEW TRANSMITTER New transmitters must be programmed at the Heatec factory using special Siemens software configured for Heatec tanks. An engraved placard (Figure 2) on the transmitter indicates that we programed the transmitter at our factory. Transmitters that have not been programmed using the special software cannot be re-programmed by plant operators to work properly. After the transmitter is programmed by Heatec, certain settings can be changed in the field by operators as explained earlier. Page 7

8 LIMITATIONS The level indicating system is ideal for determining the amount of asphalt stored in asphalt tanks. But its level indications cannot be used for liquid metering or for custody transfer. The system has limitations due mainly to variations in the specific gravity of liquids stored in the tank and due to dimensional variations in tank components. Temperature variations are a major concern. As previously stated, the transmitter must be set for asphalt at its storage temperature in order to get accurate level indications. Please be aware that the level indications produced by the pressure transmitter are not measured directly. The transmitter only senses pressure (pounds per square inch). The pressure is produced by weight of the liquid asphalt pressing against a small diaphragm in the transmitter. Pressure on the diaphragm varies a 4 to 20 ma signal that is converted into an indication of level. Only the liquid asphalt above the transmitter affects pressure on the diaphragm. The pressure is proportional to the height of the liquid above the bottom of the tank. Liquid asphalt in the tank below the transmitter has no effect on the transmitter and is considered to be in a dead zone. The volume of the liquid in the tank changes in proportion to changes in its temperature. An increase in the temperature of the liquid causes it to expand and increase its level in the tank. A decrease in temperature causes it to contract and decrease its level in the tank. But level changes caused solely by changes in temperature do not change the weight of the liquid in the tank. Therefore, pressure on the diaphragm in the transmitter remains the same despite changes in temperature. Accordingly, the transmitter cannot sense a change in level due to expansion or contraction and the level displayed on the transmitter will no longer match the actual level. This is why the transmitter must be calibrated for liquid at a certain temperature and will not produce accurate level indications at other temperatures. USING 4 TO 20 ma OUTPUT The pressure transmitter can be used to generate a 4 to 20 ma signal for checking a controller used in combination with the transmitter. The signal can also be used to check a remote display such as a Datel display. The procedure is as follows: 1. Push the mode button several times until Mode 8 Cur appears on the transmitter display. 2. Push the up and down arrow buttons simultaneously until the display on the transmitter shows 4.0 ma. 3. Check the value that appears on the controller and/or remote display. If the transmitter is mounted at a height of eleven inches, 11 should appear on controller and/or display. If the transmitter is mounted at a height of two and one half inches, the whole number 3 should appear on the controller and/or display. 4. Push the up arrow two times. The display on the transmitter should show 20.0 ma. 5. Check the value that appears on the controller and/or remote display. They should show Push the mode button until the display on the transmitter returns to display mode. HELP In the event that you cannot get your Heatec level indicating system working properly, please call Heatec at and ask to speak to a service technician. We recommend that you become familiar with the information in this Tec-Note before calling Heatec. This information will make it easier to discuss your concerns by phone. Heatec, Inc Wilson Road Chattanooga, Tennessee (423) (800) Fax (423) Heatec, Inc. Page 8

9 Figure 14. Asphalt volumes at various levels (Page 1 of 3 pages) INCHES GALLONS INCHES GALLONS INCHES GALLONS INCHES GALLONS INCHES GALLONS , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,576 Page 9

10 Figure 14. Asphalt volumes at various levels (Page 2 of 3 pages) INCHES GALLONS INCHES GALLONS INCHES GALLONS INCHES GALLONS INCHES GALLONS , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,817 Page 10

11 Figure 14. Asphalt volumes at various levels (Page 3 of 3 pages) INCHES GALLONS INCHES GALLONS INCHES GALLONS INCHES GALLONS INCHES GALLONS , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Page 11

12 HEATEC,INC. an Astec Industries Company 5200 WILSON RD CHATTANOOGA, TN USA FAX heatec.com