Water Hammer Eliminator
I would say it is a device to act as a "buffer" to prevent the water hammer effect. The water hammer effect is the banging that is heard when a water valve is closed extremely fast. The energy of the moving water has no place to disipate so it slams into the piping, casuing the loud banging. If the length of the pipe, water flow and velocities are great enough, the pipes can be ruptured by the water hammer effect. The electrically controlled solenoids on cloths and dish washing machine are the source of much of the water hammer banging in the home.
The accumulator is mounted close to the valve in the line where the flowing water will passing. The pear is 1/4 to 1/2 filled with air and the air cannot escape as there is water in the lower part of the pear. When the water valve is rapidley closed, the moving water compresses the air and disipate the energy of the moving water, eliminating the hammer effect. It cannot be seen what type of equipment "the pear" is mount upon but with the pipes and gage, I would think it has something to to with water/steam.
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