Temperatures

Temperatures are important in the refinery.  Mostly because we don’t want things to get too hot because it may blow up, or too cold, because it sticks to the pipes.  But temperature on levels also affect the measurement. We use thermometers, and temperature guns that shoot a laser to detect a temperature on a vessel or bearing on a pump. Knowing the temperature are very important when determining if something is working.

This is called a resistance temperature detector or RTD for short. These use resistance of two different types of metals, usually platinum with aluminum.  Most of them are 3-wire. They both have a certain amount of resistance.  As they heat, the resistance between them goes higher, which is then measured.  The comparison of the amount of resistance is what temperature they are reading. For instance, 1oo ohms resistance is usually 70 degrees. In fact, to see if the sensing element is a platinum, we will dip the end in 70-degree water, and if reads 100 ohms, then we have the correct type.  The reason we do this is because different metals have different resistance to temperature ratio patterns.  The good thing about using these is that they have a quick temperature reading.

Thermocouples, those sturdy sons of guns.  They look just like RTDs, except they use only two wires, and they produce electrical (very minute) called temperature dependent voltage.  There are a variety of types.  We use the J-type and K-type mostly.  The J-type is iron and Constantin, and the K-type is made up of chromium and nickel.  One wire is always the negative and one is always the positive.  To determine which is the negative, it is always the red wire, regardless of the metal.  Someone told me if the one is magnetic, it is the positive wire.  What I really like about temperature elements is that they either work or they don’t.  There is no guess work.  If they don’t work, it’s because the end of the probe probably separated, making them go “open”.  But if they intermittently work, it is usually loose wiring connection, or the bare wire is touching metal.

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