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Who can use this tool? Anyone who needs an exact profile of the temperature of their product or test medium over a long distance span (up to 250 feet). PTP was developed to determine the nature of temperature stratification within very large (250 foot tall) petroleum storage tanks. As the example above shows, when new product, although of the same type, is received into a tank, large discrepancies can occur with regard to what the temperature is when measured at various vertical points within the tank. In the example tank, there was a 9.2°F stratification from top to bottom. Now since a 0.01° delta in these tanks is equivalent to 59 gallons of fuel, the 9.2°F delta equates to a delta of 54,280 gallons! What is this temperature tool? The Temperature Element The temperature elements of each PTP system are thermistors. The thermistor (thermal resistor) is a ceramic semiconductor composed of metal oxides such as nickel, cobalt, copper, iron and titanium. After a research of the possible temperature methodologies, primarily thermocouples, platinum RTD's, and thermistors, the thermistor was decided on because of its much higher sensitivity and concomitant accuracy, which were the prime considerations in the design of this system. The technical reference section of one of the temperature industry's catalogs succinctly states the overriding factor in favor of the thermistor -- "While the thermocouple is the most versatile temperature transducer and the PRTD [i.e., platinum RTD] is the most stable, the word that best describes the thermistor is sensitive". Another manufacturer phrased it this way: "When accuracy and sensitivity are important, thermistors are the best choice". Each thermistor of a PTP assembly is sealed within a 316SS hermetic tubular probe. Through a proprietary wiring arrangement, special compensation circuits for such long cable assemblies (~300’), along with highly stable reference resistors, special digital signal processing algorithms, and primary standard temperature calibration at 3 temperatures of each thermistor under a very rigorous methodology*, Asteroid Scientific was able to achieve an industry first for this type of endeavor for field application under harsh conditions: an accuracy of ± 15 m°C (0.015°C) or ± 27 m°F (0.027°F) at the 95% confidence level relative to NIST (National Institute of Standards And Testing) over a range of 15° C to 35° C and a resolution of 0.001°C. The Electronics Element The electronics for PTP consists of National Instruments FieldPoint modules driven by a laptop computer via an Ethernet connection. This equipment can be up to approximately 250-feet from the last (top-most) probe in the assembly. * "Thermistor accuracy is entirely dependent on the accuracy and precision of the calibration system used.", Yellow Springs Instrument Co. White Paper. |
The laptop provides the multiplexing driver interface to the FieldPoint modules, the necessary Steinhart-Hart conversion (per thermistor), cable compensation, reference adjustment, special digital signal processing, filtering, and data storage for tests that can be as short as a few minutes, to hours, to months in length. Long tests may be left unattended and data retrieved at your convenience. A BITE panel (Built-In-Test-Equipment) provides a look at important system operating conditions.
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PTP: Where Precision Counts
This device is unique to the petroleum gauging industry.
- Allows very accurate,
high resolution temperature measurements.
- Real-time measurements logged to a database to be used for later analysis (can be for hours or months).
- Portable, can be moved from tank to tank.
- Displays a dynamic picture or profile of the temperature stratification
PTP has three versions:
| PTP-FA
Full Assembly There are three assemblies that make up a complete PTP system. The PTP-FA, or Full Assembly, is the unit that can measure temperature over the greatest span - up to 250 feet. It has 24 probes that spot measure the temperature at 10-foot intervals over a 250-foot span. This assembly may be configured for smaller spans with increased temperature interval resolution such as a 125-foot overall span with 5-foot spot temperature measurements. This assembly is typically used to monitor temperature over long time intervals. Data is stored to hard disk and is available for post analysis with PTP Profile Historical or with any other software. |
PTP-ZA Zone Assembly The PTP-ZA, or Zone Assembly, is an assembly that can provide higher resolution of the stratification over a 10-foot interval. PTP-ZA can be deployed any where over the full 250-foot span of the PTP-FA. It has 11 probes that spot measures the temperature at 1-foot intervals over a 10-foot span. This assembly is also typically used to monitor temperature over long time intervals. Data is stored to hard disk and is available for post analysis with PTP Profile Historical or with any other software. |
| PTP-CA
Calibration Assembly The PTP-CA, or Calibration Assembly, is the assembly that can be used to measure the temperature at any given spot over a 250-foot span. PTP-CA can be deployed any where over the full 250-foot span of the PTP-FA. It has 1 probe that spot measures the temperature at any selected point. This assembly can be used to measure the temperature at some point not covered by the other two assemblies in some given deployment or test set up, but it is typically used to calibrate existing temperature probes in a tank. Data is stored to hard disk and is available for post analysis. |
Purchase/Lease While PTP is available for purchase as a stand-alone item for use as you please, it may be more practical to lease the equipment for a specific period - contact Sales for a discussion of your requirements. |
An example of real tank temperature stratification
