6.2.2 Switching frequency
The permissible number of start-ups in a given period of time depends on the circumstances prevailing in the plant and the operating conditions. Overloading of the motor may generally result in:
-an abnormal increase in motor temperature exceeding the temperature limit of the winding or bearing grease
-premature coupling wear
-reduced service life of the pump components
-irregularities or malfunctions in the plant
To prevent abnormal temperature increases in the motor and excessive loads on the motor, coupling, pump, seals and bearings, the switching frequency must not exceed the following number of start-ups per hour (h):
Motor rating | Max. start-ups/h |
| |
up to 3 kW | 20 |
from 4 to 11 kW | 15 |
from 11 to 45 kW | 10 |
45 kW and higher | 5 |
| |
6.2.3 Minimum flows
The pump must not be operated against a closed gate valve. The minimum flows required are defined as follows.
For MTC 32, MTC 50 and MTC 65, the required minimum flow for continuous operation is:
t -10 to + 100 C | 15 % of Qopt |
t > 100 to + 140 C | 20 % of Qopt |
t > 140 to + 200 C | 25 % of Qopt |
For MTC 100, MTC 125 and MTC 150, the minimum flow required for continuous operation, independent of the temperature, is:
0.35 x Qopt.
For MTC 100, MTC 125 and MTC 150 an additional, short--term minimum flow of 0.25 x Qopt. has been defined, which is permitted for up to 1 hour’s uninterrupted operation and approx. 200 h/year.
The minimum flows indicated for MTC 32 to 150 above are for single pump operation and will prevent thermal and mechanical overloading of the pump. In case of parallel operation with pumps of identical or different design higher flow rates may be required in some cases, to guarantee a stable operating behaviour.
6.2.4 Density of fluid pumped
The pump input power will increase in proportion to the density of the fluid handled. To avoid overloading of the motor and pump, the density of the fluid must comply with the data specified on the purchase order.
6.3Shutdown / Storage / Preservation
6.3.1 The unit / pump remains installed; periodic check of operation
In order to make sure that the pump is always ready for instant start-up and to prevent the formation of deposits within the pump and the pump intake area, start up the pump set regularly once a month or once every 3 months for a short time (approx. 5 minutes) during prolonged shutdown periods. Follow the instructions for commissioning (see 6.1).
Prolonged shutdown periods should be avoided in the case of pumps in material variants 10, 13, 20 and 21 (cast-iron variants), particularly if the pumps are handling aggressive water qualities (high oxygen content). In such cases, the pump should remain filled, and the operation check run should be performed at least every other day, instead of once a month or once every 3 months (see also 6.1.5).
In the event of frost and/or prolonged shutdowns, the pump must be drained and protected against freezing and corrosion. To drain the pump, open drain plug 6B.
Caution In the case of horizontal pumps, virtually complete drainage of the stage casings in installed condition can only be ensured by opening the plugs on
the stage casings (optional). If this is not possible, it is recommended to remove the pump from the system and proceed according to section 6.3.2.
6.3.2The pump is removed from the pipe and stored Before putting the pump into storage, carry out all checks and maintenance work specified in section 7.1. Then preserve as follows:
Drain the pump as completely as possible. On vertical pumps, this can be done by opening the drain plugs on the suction casing.
Horizontal pumps with drain holes in the stage casings (optional) can be drained almost completely by opening the drain plugs. The pump can also be drained by bringing it into a vertical position - suction nozzle pointing downwards - by crane (see 3.1). Turn the rotor by hand. However, the seal housing must still be drained separately by opening the respective drain plug.
If the pump cannot be drained completely, we recommend to dismantle it and dry the individual
components.
Afterwards fill the pump with a water-repellent preservative, e.g. RUSTELO DEWATERING 924 (producer CASTROL) OSYRIS DW (producer TOTAL) or equivalent.
Turn the pump rotor by hand several times, to ensure even distribution of the preservative. Then drain the pump and close the suction and discharge nozzle.
Exposed blank metal parts must be treated with a suitable anti-corrosive agent.
Caution | If the pump is preserved for a prolonged storage |
| period with KLÜBERTOP K 01-601 or another |
glycol-base preservative, the preservative must not be drained. In this case, the pump must be completely filled with preservative for storage. The preservative must be drained before the pump is returned to service. It can be re-used. Before re-use, make sure that the water content in the preservative does not exceed 20%.
6.4Returning to service after storage
Before returning the pump to service, carry out all instructions laid down in the sections on ”Commissioning” (6.1) and ”Operating limits” (6.2).
Immediately following completion of the work, all safety-relevant and protective devices must be re-installed and/or re-activated.
