The pump consists of two figure "8" shaped rotors and two semicircular pump houses. The rotors rotate synchronously in opposite directions and high speeding. The pump cannot be used singly; it must be used as boosters combined with a backing pump such as a rotary piston or a rotary vane vacuum pump, or a liquid ring vacuum pump. These vacuum systems can get higher vacuum, a stable, fairly high pumping speed can be gained in effective pressure range. The backing pump decides the ultimate pressure of roots pump. The data of the list is lowest ultimate pressure with the standard equipment (equipped double stage oil machine vacuum pump). The Roots pumps are widely used in vacuum moulding, vacuum smelting, vacuum gas pumping, vacuum coating industry, vacuum distilling and vacuum drying of chemical and pharmaceutical industry etc. The pump is insensitive to a little dust.

Merit:
1. The lack of reciprocating parts allows a perfect dynamic balancing, because the rotors is processed by numerical control machine tool and balanced carefully. It has perfect geometry symmetry. There is certain clearance between the two rotors. The pump house and end-cover is processed by especial machine tool. It has high precision. So the pump own feature of stable operation, low noise, low vibration and high ultimate pressure.
2. The robust drive of ump and operating parts balanced carefully permit that the pump be stably operated continuously under the condition of high different pressure.?
3.They can be started quickly, and in short time ultimate pressure is reached
4. Lubrication is unnecessary as there is no contact between rotors, rotor and house, that avoid oil vapor from polluting vacuum system.
5. Good reliability characteristic. Their inherent overflow valve play auto-protective role.
6. Compact structure, low footprint design. There are three gas outlet ports that are in left, right and under pump house. It is convenient for consumer installing.

ZJ、ZJP pum main perfomance-parameter table

型號	Ultimate pressure(Pa)		pumping speed(L/S)	maximum permissible Different pressure (HPa)	lnlet & outlet dimensions (mm)		Power (kw)	Max Compression ratio with zero throughput	Weight(Kg)
	配用雙級油封 機械真空泵	配用單級油封 機械真空泵			lnlet	outlet
ZJP-70	≤2x10-2	≤1x10-1	70	100	80	50	1.5	≥35	100
ZJP-150			150	80	100	100	2.2/3	≥40	220
ZJP-300			300	80	150	150	4	≥40	300
ZJP-600			600	50	200	200	5.5/7.5	≥45	575
ZJP-1200			1200	50	250	200	11/15	≥50	860
ZJP-2500			2500	30	320	250	18.5/22	≥50	1480
ZJ-30			30	100	50	40	0.75	≥30	55
ZJ-70			70	100	80	50	1.5	≥35	90
ZJ-150			150	80	100	100	2.2/3	≥40	210
ZJ-300			300	80	150	150	4	≥40	285
ZJ-600			600	50	200	200	5.5/7.5	≥45	550
ZJ-2500			2500	30	320	250	18.5/22	≥50	1480
ZJ-5000			5000	30	400	320	37/45	≥55	3400

Series ZJP roots vacuum pump own the structure of overflow valve

Model	A	A1	A2	A3	A4	B	B1	B2	B3	H	H1	H2	H3	D	D1	D2	d	d1	d2	d3	d4	d5	m	n	p	e	f	g	k
ZJ70	330	120	370	584	829	219	247		324	226	122	18		90	125	145	50	90	110				4	4		8	8		18
ZJ150B	115	57.5	154	675	950	320	360	380	448	345	205	35	95	100	145	170	100	145	170	80	125	145	4	4	4	10	10	10	18
ZJ150BJ	440	118	480	675	950	320	370	380	448	380	240	70	130	100	145	170	100	145	170	80	125	145	4	4	4	10	10	10	18
ZJ300B	225	112.5	314	775	1125	320	360	370	452	345	205	35	120	150	195	220	150	195	220	100	145	170	8	8	8	10	10	8	18
ZJ300BJ	600	197	640	775	1125	320	360	370	452	380	240	70	155	150	195	220	150	195	220	100	145	170	8	8	8	10	10	8	18
ZJ600B	170	85	250	896	1270	500	550	570	610	530	320	40	170	200	250	285	160	200	225	160	200	225	8	8	8	10	10	10	18
ZJ5000	655	327.5	880	1915	2720	1020	1120	1150	1200	1050	600	40	250	400	480	510	320	395	425	320	395	425	16	12	12	12	12	12	32

Series ZJP roots vacuum pump own the structure of overflow valve.