When the plunger pump is in the suction stroke, the pressure at the front packing 2-2 is calculated by Py-Px= (1/3~2/3)P-0= (1/3~2/3)P, where Px denotes the suction pressure which is relatively low when compared with the discharge pressure and usually considered as 0; and the pressure at the rear packing 2-4 is calculated by Py-Pq= (1/3~2/3)P-0= (1/3~2/3)P, where Pq denotes the atmospheric pressure which is relatively low when compared with the discharge pressure and usually considered as 0.If only the front packing 2-2 fails, the pressure value displayed by the pressure sensor 2-11 on the plunger packing lubrication pipeline is equal to, or approaches, the discharge pressure of the plunger 2-7 pump. The intelligent control system then gives an alarm to alert the operator of the failure of the front packing 2-2 and thus the replacement of a new front packing.If only the rear packing 2-4 fails, the pressure value displayed by the pressure sensor 2-11 on the plunger packing lubrication pipeline is equal to, or approaches, 0. The intelligent control system then gives an alarm to alert the operator of the failure of the rear packing 2-4 and thus the replacement of a new rear packing. Of course, the rear packing 2-4 will serve for a much longer period of time than the front packing 2-2.If both the front packing and the rear packing 2-4 fail, the flow of the large-flow plunger pump will be insufficient and the flow monitoring system will gives an alarm.During the operation of the plunger 2-7 pump, the pressure at both the front packing 2-2 and the rear packing 2-4 is (1/3~2/3)P. The uniform pressure distribution avoids the influence on the fatigue life of the packings from the high alternating stress. Meanwhile, it is easier for the lubrication oil to permeate into the friction pair between the plunger packings under high pressure. Accordingly, the friction coefficient therebetween is reduced and the service life of the packings is prolonged. Most importantly, if the packings narrow, after the plunger packings are worn, in the axial direction (the movement direction of the plunger 2-7) under the effect of the high-pressure oil to ensure the tight contact with the plunger 2-7, the small gap resulted from the deformation is filled by the high-pressure oil (liquid is uncompressible under a certain pressure while the high-pressure oil is equivalently rigid. The amount of lubrication oil consumed by the friction pair between the plunger packings is limited and the lubrication oil can be replenished in time when decreasing down to a certain pressure). That is, the packings can be compensated automatically after being worn, without requiring any manual packing adjustment. This solves the practical difficulty that it is unable to tighten the gland nut manually and it is likely to cause the fluctuation of the high-voltage grid if the pump is stopped for adjustment, due to the large diameter (>100mm) of the plunger 2-7 in the large-flow plunger pump and the large annular area stress (>55000N) at the packings.As shown in Fig. 7, a suction-pressure stabilizer 6 having a cooling water coil 6-1 therein is provided at a suction inlet 12 of the plunger pump. The cooling water coil 6-1 is distributed within the suction-pressure stabilizer 6. A circulating cooling water inlet 13 at one end of the cooling water coil 6-1 is communicated with a water replenishing tank 11 via a pipeline while the other end of the cooling water coil 6-1 is communicated with a cooling water inlet 8 of a plunger pump oil pool cooling coil 15. The cooling water becomes high-temperature water after absorbing heat from the lubrication oil when flowing through the cooling coil within the oil pool. A high-temperature water outlet 9 is communicated with a domestic heat supply pipeline 10, and the domestic heat supply pipeline 10 is communicated with the water replenishing tank 11. What is cooled between the cooling water inlet 8 and the high-temperature water outlet 9 is the lubrication oil at the power end of the plunger pump.