Each roots water ring pump unit of JZJ series is an exhauster unit comprising a JZ roots water ring pump as main pump and a 2BV water ring pump/2BE1 water ring pump/SK water ring pump or roots-water ring pump unit as a backing pump. The units are applied to exhausting normal gases and gases with water, organic solvents or a little dust. Compared with normal mechanical vacuum pumps, the units resist oil, steam and dust. Compared with normal water ring vacuum pumps, they have high vacuums and high exhaust speeds under high vacuum.
The backing pumps for the roots water ring pump units usually use water as the operating fluid as well as organic solvents (methanol, ethanol, xylene, acetone, etc.) or other liquids. The backing pumps are closed circulatory systems, remarkably reducing environmental pollution and increasing recycle rate of organic solvent. The limiting vacuum is determined by saturated vapor pressure of the operating liquid.
The models are expressed by basic codes and assistant codes as follows:
<J> <ZJ> <1>-<2>-<3> <4>
J, ZJ and <1> are basic codes, among which J stands for the unit; ZJ stands for code of the main pump,
and <1> stands for code of the backing pump, specifically, 2BE,2BV,2SK.
<2>, <3> and <4> are assistant codes,
<2> stands for nominal exhaust speed of the main pump (L/S);
<3> stands for code of exhaust speed ratio of the main pump to the backing pump, main pump to intermediate pump or intermediate pump to backing pump;
and <4> stands for modification code which can be null if no modification is carried out.
For example, J ZJ 2SK 600-2.2.1 stands for a three-stage water ring roots unit in which exhaust speed of the main pump is 600L/S, exhaust speed of the intermediate pump is 300-150 L/S and the backing pump is 2SK(2SK-6).
Common ratios of JZJ roots-water ring vacuum pump units:
Values described above are common pump ratios. The limiting vacuums and exhaust speeds are ideal values under standard condition. Actual performances of the unit are determined by working condition.
The limiting vacuum of the unit can be increased to a certain degree when the circulating liquid of the water ring pump is oil or other liquids with low saturated vapor pressures.
The roots pump will heat and the limiting vacuum will fall when performance differences between the main pump and backing pump are over large. Such problem deserves special attention as it affects stable operation of the unit. For better reliability of the unit, we suggest larger ratio for the backing pump as long as overall power is maintained.
When the roots pump is combined with a water ring pump, water in the water ring pump may flow into the roots pump when the unit stops, resulted in emulsification of oil in gear box of the roots pump after a certain period. Our company equips a liquid stopper at inlet of the water ring pump and an air pocket between the water ring pump and roots pump so as to prevent the backflow, thus the unit is more reliable.