JERGUSON SOLUTION: Magnicator® II FlashProof Gage Comparison

Application Issue

Jerguson® recently introduced the FlashProof Magnicator II Level Gage to solve a common problem with light-end gas and refrigeration applications. By employing an over-sized chamber with guide rods, a vapor by-pass zone is created to allow entrained gas (or bubbles) to pass behind the float rather than collect underneath, which would cause the float to sink. Prior to the release of this product, Jerguson conducted extensive testing to optimize the chamber size and verify performance of the unit in both lab-simulated and real-world situations.

Over the past few years, other manufacturers have introduced products based on this concept. However, simply adding a guide rod of minimal diameter and going up one pipe size (as compared to the standard chamber pipe size) does not produce the same result.

Jerguson recently tested another manufacturer’s “FlashProof” gage and found that the float sank under the same conditions that caused a Standard Jerguson gage float to sink!! After the test, an analysis was conducted on float and by-pass area to seek answers.

As you can see in row three of Table 1 below, the amount of free area in both the other manufacturer’s gage and Jerguson’s standard gage is about the same (calculations based on nominal chamber bore values) but there is a significant increase when moving to a FlashProof type gage. However, even though the other manufacturer’s design produced an area over double that of their standard gage, the float still sank in the same amount of boiling compared to a standard Jerguson Magnetic Level Gage! The explanation behind this is that you not only need to consider the free area of the chamber, but also the available buoyancy of the float. The cross-sectional area of the float is directly proportional to the available buoyancy. The Jerguson FlashProof Gage contains a 2.25″ OD float that offers 1.4 times the buoyancy of the competitor’s 1.9″ OD float.

As entrained gases rise in a standard gage chamber, they collect under the float and detract from the float’s positive buoyancy (the float is now displacing vapor instead of liquid), causing the float to sink. With a FlashProof chamber, those bubbles move to the By-Pass Zone and escape to the surface, allowing the gage to provide a reliable level measurement.

Testing conducted on different styles of FlashProof chambers has shown that the positive buoyancy generated by the float is critical for proper operation in a FlashProof Gage. In conclusion, that both the Float Diameter and By-Pass Zone areas are equally important when specifying a FlashProof Gage.

Illustration 1: Typical FlashProof Chamber (3/8-inch diameter rods)

Jerguson® Solution

Jerguson’s FlashProof Magnetic Level Gage is constructed using a 3” Schedule 40 chamber with large, square guide rods. The square rods provide a consistent bearing surface to guide the float and greater area for securing the rods to the chamber.
The guide rods on all Jerguson FlashProof Gages are spot-welded at 3-foot maximum intervals to ensure the rods stay straight and do not bow in the chamber due to temperature differences.
Jerguson has extensive experience with worldwide oil refiners and chemical producers solving problems
associated with boiling liquids in Magnetic Level Gages. Let us solve your problem today.

Illustration 2: Jerguson FlashProof Chamber (1/2-inch diameter bar)

ACCESS Professional Viet Nam Limited Company is distributor of Jerguson Gage & Valve Company – a brand of Clark Reliance Coporation.

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