How to judge whether the thermal dispersion booster pump and its assembly of papermaking machinery need to be replaced?

The paper-making thermal dispersion booster pump and its assembly judge whether it needs to be replaced as a whole.

The medium of thermal dispersion booster pump is high-temperature and high-consistency waste paper pulp at 120,160℃, which contains sand, filler and adhesive. It can be divided into two situations: local parts can be repaired when damaged; If the overall performance of the assembly is degraded, the shell structure is damaged, and the bearing position is seriously worn, it is not recommended to repair and replace the assembly directly. Let's distinguish which ones can be repaired and which ones must be replaced from performance parameters, abnormal vibration, leakage, body damage and maintenance cost performance.

First, the operation process parameters are abnormal (first, it means that the hydraulic capacity of the pump has been attenuated)

1. The outlet pressure can't reach the design value, and the regulating valve can't get up.

Under the same rotating speed and slurry concentration, the working pressure at the pump outlet is obviously lower than the historical normal value; Insufficient heat dispersion pressure in the system leads to poor beating effect of heat dispersion and unqualified peeling of adhesive.

-Maintainable: the impeller is slightly fouled and the inlet filter screen is blocked; Recover after cleaning.

-The assembly needs to be replaced: the impeller and the wear-resistant lining plate of the pump casing are eroded and perforated in a large area, and the gap is seriously out of standard; After the impeller was overhauled and replaced for many times, the pressure fell again in a short time, and the volute of the shell was washed and worn by slurry, and the shell body lost its repair value.

2. Abnormal motor current

-Current continues to be high: internal friction, bearing damage, impeller hitting the shell;

-Low current and insufficient output: impeller wear and internal medium backflow.

After repeatedly adjusting the working conditions, the current always deviates from the normal range of the equipment nameplate. If the volute and pump body matrix are found to be worn after disassembly, the assembly shall be replaced.

3. Cavitation occurs frequently and repeatedly

Frequent cavitation, after eliminating the problems of feed level, feed pressure and pipeline blockage, opened the pump body and found a large area of honeycomb cavitation pit of volute and impeller, and a large number of matrix metals were missing, so the maintenance time of repair welding was very short. It is recommended to replace the assembly directly.

Second, vibration and noise, judge the bearing, coaxiality and shell state.

1. The vibration value continuously exceeds the allowable vibration limit of the pump; The temperature of the bearing box is high for a long time, and the bearing is replaced many times, which causes heat and vibration rebound again in a short time.

> if only the bearing is damaged: just replace the bearing separately.

> assembly replacement conditions: the bore (bearing seat) in the bearing box is worn out, the bearing position is out of round, the hole is out of round, the cost of repairing the insert is high, and the reliability of on-site maintenance is poor, so the replacement of the whole assembly is preferred.

2. The pump operation has periodic impact and abnormal friction sound, and the turning has obvious jamming and rubbing; Disassembly inspection is not a simple blockage of sundries, but a serious deformation of the pump housing and guard plate, interference between the impeller and the housing, and the deformation of the housing cannot be corrected, so the assembly needs to be replaced.

Third, the leakage situation (mechanical seal is a wearing part, which does not mean replacing the assembly)

> key distinction: bad seal ≠ bad pump assembly. The mechanical seal of thermal dispersion pump belongs to consumable parts, and the seal leaks water and slurry, so the container mechanical seal should be replaced first.

1. After replacing a new set of mechanical seals, a large number of shotcrete leaks occurred again in a short time (days to weeks):

On the premise of checking that the flushing water system is normal, the following appears:

-The surface of the pump shaft is scoured and worn, and the shaft sleeve is seriously corroded;

-the shaft runout is too large, and the bearing wear causes the shaft to move radially;

This kind of replacement-only seal can't be cured, so it needs to be evaluated and replaced.

2. The flange surface of the shell is eroded and sunken, the sealing gasket fails repeatedly, the flange is sprayed continuously, the sealing surface of the flange can not be repaired by grinding, the shell body is damaged, and the assembly needs to be replaced.

Four, the physical damage of pump body shell, over-current parts (hard replacement index)

In case of any of the following, it is recommended to replace the assembly directly, and it is not recommended to repair welding to continue long-term production:

1. Cracks and sand holes appear in the volute casing of the pump, and welding repair under the condition of high temperature slurry is easy to crack repeatedly, which has high safety risk;

2. The wear-resistant guard plate inside the pump shell falls off in a large area, and the matrix is washed away by the slurry to become thinner, and the wall thickness of the shell is seriously reduced;

3. The whole impeller is broken and severely deformed; The matching clearance in the pump cavity far exceeds the maximum allowable clearance of the original factory, and the impeller will still fail quickly after being replaced many times.

4. The foundation of the base shell is cracked, and the base is deformed, so it is impossible to find the right alignment.

> minor erosion pits can be repaired by wear-resistant welding; The shell wall thickness is greatly reduced and cracked, and it is not recommended to repair it under high temperature and pressure.

Five, judging from the perspective of maintenance cost and downtime (factory actual production judgment)

1. Repeated maintenance of the same booster pump in a short period: frequent seal replacement, bearing replacement and shell repair welding, shorter and shorter fault interval, high maintenance man-hours and spare parts cost, frequent shutdown affecting thermal dispersion of the whole pulping line, and comprehensive evaluation of direct replacement of the assembly is more economical.

2. It is difficult to purchase old equipment and spare parts, and the old pump spare parts have been discontinued, so it is impossible to purchase matching spare parts, and the new assembly is directly replaced.