level / interface measurement

---

This technique is based on the unique moderating effect that hydrogen atoms have on the energy level of neutrons.  Simply put - a source of high energy neutrons is placed against the vessel.  Hydrogen atoms inside moderate these to low energy or thermal neutrons which can be readily measured with sensitive detectors.

Exploiting this property is extremely useful in that access need only be to one side of the vessel.  This makes it very quick.  It is also accurate with a tolerance typically ±1 inch.

The neutron backscatter technique not only determines liquid/vapor and solid vapor interfaces, but also in some instances, successfully locates liquid/liquid and liquid/solid interfaces.  Typical applications include:

• Determining liquid in distillation column downcomers and draw pans
• Level measurements during service or repair of installed gages.
• Calibration of nucleonic or conventional level gages on storage tanks, spheres, and tank cars.
• Measurements of levels in vessels not requiring monitoring such as knock out pots and heat exchanger shells
• Locating sludge levels in the bottom of tanks