API MPMS 7.2:2018 pdf download
API MPMS 7.2:2018 pdf download.Manual of Petroleum Measurement Standards Chapter 7- -1 Temperature Determination Section 2- Portable Electronic Thermometers.
6.3 Stabilization
The temperature reading of a PET has come to equilibrium in liquid when the reading varies no more than t 0I °C (02°F). The PET may also have a visual or audible method of indicating that the temperature reading has stabilized. Table 4 shows typical stabihzation times m liquid, but this may vary due to the mass of the probe sensor assembly.
6.4 Cable and Probe
The cable connecting the temperature sensor to the measuring instrument shall be long enough to cover the full depth of the tanks for which the PET Is likely to be used. It may be marked at meter or foot intervals In order to assist m lowering to the required level. In applications where the PET will be used with a Ihermowell, the probe dimensions shall permit full Insertion Into the thermowell.
NOTE Cables wrapped on a spool device may be damaged prematurely if used with heavy products, such as asphalt or healed, viscous proêicts. A PET constructed with a hand-wrapped cable may be more appiopnate for heavy or heated products.
6.5 Voltage Indicator
Include with each unit a test system or switches to mdicate low battery voltage.
If the equipment has a rechargeable battery, provide a suitable-voltage battery charger and only charge in an intrinsically safe area.
6.6 Additional Functionality
Additionally functionality, such as listed below, is not required, but may be useful in some applications:
— averaging of temperature readings;
— minimum)maximum storage of temperature readings;
— backlighted or illuminated display characters; or
— visual ci’ audio indication of temperature stabilization.
6.7 Thermowells
The use of therrnowells is required to Isolate the liquid material from the temperature sensor. There are two general classification types of thermowells: test wells and sensor wells. Both these classifications of thermowells should be filled with conductive fluid, grease, or paste to ensure proper temperature readings.
6.7.1 Test Thermowells
Test wells are thermowells installed for occasional use (temperature checking), and are capped when not in use. Test wells shall be installed adjacent to sensor wells. A suggested location is within three pipe diameters (maximum to be determined by company policy) between the test well and sensor well. Capping prevents foreign material from accumulating in the well bore. The test well should be the same type as the sensor well, which is used for the working device, but at a minimum, the test well shall have the same insertion length and a bore large enough to allow the use of a PET. A clogged thermowell can cause measurement errors and can damage thermometers. It is recommended that thermowells be checked periodically for an accumulation of foreign material, and cleaned, if needed.
7.2.2.3 Tank Cars and Tank Trucks (nonpressurlzed)
If the temperature of a tank car Is riot determined dynamically dunng the loading, temperatures should be taken on every tank car at the middle of the liquid. However, by mutual agreement, when loading multiple tank cars or with nonheated oil from one source, temperatures may be determined on the contents of at least 10 % (a minimum of three tank cars) of the number of cars, selected at random. This assumes that all of the tank cars are of the same nominal size and that all of them are either insulated or all of them are uninsulated. When a car Is to be heated to facilitate discharge Ii cold weather, lake the temperature of the contents of each car at the same time the car is gauged. In all cases, thermometer immersion times shall be in accordance with those specified in Table 4.
Before tank cars are loaded, determine the temperature of the volume in the heel of the tank car. The heel temperature may be assumed to be at ambient temperature, unless the heel volume exceeds 7 % of the tank car capacity. In that case, a temperature needs to be measured in the middle of the heel level. (See API
RI’ 3000.)
The above section also applies to determination of the temperature In tank trucks.
7.2.2.4 Pressurized Tanks
A spherical or spheroidal-type tank may be equipped with either a vertical thermowell, horizontal separable wells, or pressure locks that can be used for temperature determinations.
If a vertical thermowell is used, take and average temperature measurements according to Table 2 and Table 3 (volume-weighted averaging may be used).
If horizontal separable wells or sockets are used, take and average temperature measurements in the wells below the product liquid level.
7.2.3 AmbIent Temperature Measurement
Tanks undergo expansion and contraction due to variations in amb.ent and product temperatures. Such expansion or contraction in tank volume may be computed once the tank shell temperature is determined. Tanks that have been calibrated in accordance with API MPMS Ch. 2 have capacity tables based on a specific tank shell temperature.
