Eequipment wear and types of repairs

Aug 15 10:15 2017 Aleksei Shladkov Print This Article

Overhaul is performed by the efforts of the CEMS or mining equipment repair plant. Overhaul of pump units pumping out clear water is performed once a year in the coal industry. Terms between routine repairs and overhauls when acid mine waters are pumped decrease considerably in the ore mining industry. Periods between repairs in this case will be established depending on the degree of mine water acidity and contamination.

Severe climatic conditions in mines and at open pits influence on the service life of pump and coal pump units.

High air humidity,Guest Posting as well as thermal shocks cause changes in winding resistance of electric machines and spools of trigger units. Ice plugs occur in hydraulic transport units, as well as in the water supply system at low temperatures in winter; they may cause breakdowns of weld joints and valves of pipelines. The hydraulic fluid in ground pumps and coal pumps freeze under the influence of low temperature, forms a leak-tight crust which may be warmed only by hot water or steam. The deposit generation inside pumps causes additional wear of impellers and seals due to the flow rate increase and solids carry-over. Natural wear is connected with continuous contact of pump unit parts with the contaminated water or hydraulic fluid flow. Major wear is observed in O-rings which separate the pump stages, as well as in discharge devices. Impellers and seals are subjected to the greatest wear in ground and coal pumps. To this end, the timely inspection and replacement of worn parts allow keeping the basic parameters of pumps and coal pumps within the operating area of characteristics and avoiding an emergency failure. Such failure, for example, thrust bearings may cause sharp increase of the axial force and motor failure.

A pump unit operator or dispatcher shall control carefully the operation of the water drainage, hydraulic lift or ground pump station when maintaining automated pump stations. All faults in the coal pump, pump and ground pump operation shall be recorded in a special log. For this purpose, a book shall be kept in the pump and hydraulic lift chamber or in the ground pump cab. Book or log records are the important grounds for planning scopes and establishing terms of various types of repairs.

A correctly built repair system ensures timely control of pump equipment serviceability for further operation.

Each type of equipment (water drainage, hydraulic lift, ground pump) in operation shall have a schedule of preventive repairs.

The preventive repair system includes the following main actions:

  • inspection of the pump, electric drive and trigger equipment by a maintenance operator during the shift acceptance and in the process of operation;
  • periodical inspection of the pump station by a special repair team;
  • periodical repair of the pump and coal pump unit carried out directly in the chamber or in the area (routing repair);
  • periodical replacement of the pump (coal pump) at the district and central water drainage (hydraulic lift);
  • periodical repair of water drainage (hydraulic lift) equipment in the central electric shop (CEMS).

The unique system of preventive repairs contains schedules of inter-repair maintenance, as well as routine repairs and overhauls. Emergency repair refers to unscheduled ones.

Routine repair of the pump unit is performed once in 15 days by the special repair team. The following scope of works is performed in this case:

  • small parts (discharge rings, pins, sleeves, and cocks) are partially replaced;
  • the suction and delivery pipelines and pump covers are disconnected and inspected;
  • the intake valve and mesh are cleaned;
  • gate valves and check valves are replaced;
  • oil baths or anti-friction bearings are flushed; oil, packing are replaced and glands are adjusted;
  • the impeller is inspected;
  • pumps, coal pumps or ground pumps are cleared from solid precipitations;
  • worn gaskets are replaced;
  • the conditions of the front sections of the motor rotor and terminal block are checked;
  • the insulation resistance and cooling system of the motor are controlled.

All types of routine repair are recorded in logs. A punch list being the main document for the unit preparation for overhaul is drawn up based on records. The sheet includes major defects and methods for their removal, as well as the list of required spare parts.

Overhaul provides for complete restoration of pumps in accordance with technical requirements. The pump, ground pump and coal pump is disassembled using all required auxiliaries (winches, hoists, overhead electric hoists). A possibility of the entire unit demounting is not excluded.

The overhauled pump performance shall be the same as the new pump performance.

Emergency repair is connected with the removal of faults occurring during accidents or faults which may cause an accident.

Each scheduled repair includes the repair preparation and unit testing after repair.

An emergency failure occurrence is explained by the fact that worn parts were left in the pump during the repair or defective parts were installed.

The pump failure is caused by the irresponsible attitude of maintenance personnel to its duties (for example, in case of lubricant absence, excess tightening of bearings).

As to the labor content, emergency repair may be equal to routine repair or overhaul. Therefore, each emergency is drawn up in the form of an act containing detail causes of the pump failure.

To avoid accidents, terms of repairs shall be strictly followed and their quality shall be increased.

Each mining enterprise shall struggle for the repair cost reduction: reduce the repair cost – this will reduce the prime cost of the mineral.

For this purpose the following actions shall be carried out:

  • reduce the need in repairs due to the pump unit maintenance improvement and introduction of the automatic pump duty control;
  • reduce the repair labor content;
  • increase terms of pump unit service life by replacing high-wear parts with stronger ones made of new synthetic materials.

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Aleksei Shladkov
Aleksei Shladkov

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