PSI - Issue 20

Nickolay Ovchinnikov / Procedia Structural Integrity 20 (2019) 113–118 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

117

5

It should be noted, that the operation of the sectional pump at a critical axial displacement of the rotor is not always accom panied by an increase in the water temperature in the discharge pipe above 20 ºC. Typically, such a temperature increase is observed or with long-term dispersal of pumping equipment to the rated speed, or in the case of his work with a low end gap, which is due to poor maintenance of the site hydraulic balancing unit. The value of the water flow in the discharge pipe is usually determined using electromagnetic flowmeters in explosion-proof design. In practice not all section pumps of underground kimberlite mines of the Company are equipped with flowmeters for measurement of q value that, is caused, including, their high cost (the cost of one original flowmeter in explosion-proof execution makes about 400 thousand roubles) and errors when working on water with a significant content of iron oxides (the mine waters of the company's underground mines contain a large number of salts that accelerate the process of corrosion of the metal) and oil products (the presence in the mine water of underground kimberlite mines of the Company is quite common). Thus, in the underground kimberlitic mines of the Company, it is important to find an alternative to flow meters for recording the change in the value of q. Statistical processing of the results of laboratory tests carried out on the pumping unit (based on the cantilever pump model K8/18) indicates that the flow (q*) of water in the pipe simulating the discharge pipe correlates well with RMSV of the vibration velocity of this design (Fig. 4, a) (Vikulov et. al. (2017)). Substituting in the empirical formula (see Fig. 4 (a), lower threshold (3 m/h 3 - for pumps with Q = 300 ÷ 400 m/h 3 and 2 m/h 3 - for pumps with Q = 150 ÷ 250 m/h 3 ), weighted average (6 m/h 3 - for pumps with Q = 300 ÷ 400 m/h 3 and 4 m/h 3 - for pumps with Q = 150 ÷ 250 m/h 3 ) and the upper threshold (9 m/h 3 - for pumps with Q = 300 ÷ 400 m/h 3 and 6 m/h 3 - for pumps with Q = 150 ÷ 250 m/h 3 ) values q, it was found that the deviation of the vibration velocity RMSV υ from its weighted average value, both downward and upward by 16 % (for pumps with Q = 150 ÷ 250 m/h 3 ) and 20 % (for pumps with Q = 300 ÷ 400 m/h 3 ) are critical.

b

a

Fig. 4. (a) Statistical processing of the results of laboratory tests of the cantilever pump model K8/18 (a) and field tests of sectional pumps of underground kimberlite mines (b)

It should be noted that all of the above values of q were determined by the authors in the course of full-scale tests of pumping equipment and surveys of working personnel of mechanical power services of the Company's MPC. Sectional pumps with a range of Q = 150 ÷ 400 m/h 3 are the most common models in the underground kimberlitic mines of the Company(Fig. 4, b). Due to the fact that sectional pumps at underground kimberlitic mines of the Company are one of the most important machines, they need additional protection from operation in case of critical axial shift of the rotor. The authors propose sectional pumps in addition to ADSR, vibration and temperature sensors installed on bearing assemblies, vibration sensor and temperature sensor installed on the discharge pipe, also to equip the flow relay, which is mounted in the discharge pipe. The need for the use of the flow switch is explained further. Vibration and temperature sensors, as well as ADSR are quite "sensitive" devices, in this connection, they are characterized by breakdowns and malfunctions that can