Correctly Using A Pump With A Middle Opening Is Beneficial For Extending Its Service Life

Oct 25, 2025

 

1,Correct selection and installation

The selection of the medium opening pump should be based on the liquid being transported, and the required performance should be checked, including analysis of suction and discharge conditions, whether it operates intermittently or continuously, etc. Medium opening pumps should typically operate at or near the pressure and flow conditions specified by the manufacturer's design. The following rechecks should be conducted during pump installation:
1. The size, position, and elevation of the foundation should meet the design requirements. The anchor bolts must be properly and correctly fixed in the concrete foundation, and the machine should not have missing parts, damage, or rust;
2. Based on the characteristics of the medium conveyed by the pump, it is necessary to check the materials of the main components, shaft seals, and gaskets when necessary;
3. The leveling and alignment of the pump should comply with the provisions of the equipment technical documents. If there are no provisions, it should comply with the current national standards;

 

4. The installation of all pipelines and fittings connected to the pump body, as well as the cleaning requirements for lubricating oil pipelines, shall comply with the relevant national standards.

 

2,Correct use: The trial operation of the medium opening pump should meet the following requirements

1. The steering direction of the driving machine should be the same as that of the pump;
2. Identify the direction of rotation of pipeline pumps and coaxial pumps;
3. Each fixed connection part should be free of looseness, and the specifications and quantities of lubricant added to each lubrication part should comply with the provisions of the equipment technical documents;
4. Parts with pre lubrication requirements should be pre lubricated according to regulations;
5. All indicating instruments and safety protection devices should be sensitive, accurate, and reliable;
6. The turning gear should be flexible and free of abnormal phenomena;
7. Before the trial operation of the high-temperature pump, the pump body should be preheated, and the temperature should rise uniformly. The temperature rise per hour should not exceed 50 ℃; The temperature difference between the surface of the pump body and the process pipeline with working medium inlet should not exceed 40 ℃;
8. Set up connection devices to eliminate the impact of temperature rise, and install bypass connection devices to provide cooling water sources.

3, When operating a medium pump, the following points should be noted:

1. Do not operate without water, do not adjust the suction capacity to reduce the displacement, and do not operate at low flow rates;

 

2. Monitor the operation process to completely prevent leakage of the packing box, and use new packing when replacing the packing box;
3. Ensure that the mechanical seal has sufficient flushing water flow, and excessive water flow is prohibited for water-cooled bearings;
4. Do not use too much lubricant;
5. Check according to the recommended cycle. Establish operation records, including operating hours, adjustment and replacement of fillers, addition of lubricants, and other maintenance measures and time. The suction and discharge pressure, flow rate, input power, temperature of the cleaning fluid and bearings, as well as the vibration situation of the pump should be measured and recorded regularly.
6.The main engine of the middle pump relies on atmospheric pressure to pump water from lower areas to higher areas, and atmospheric pressure can only support a maximum water column of about 10.3 meters, so the main engine of the middle pump cannot work when it is 12 meters away from the water surface.

 

4, Analysis of Mechanical Seal Failure in Zhongkai Pump

The shutdown of the medium opening pump is mainly caused by the failure of the mechanical seal. The main manifestation of failure is leakage, which can be caused by the following reasons:

1. The leakage of the sealing surface of the dynamic and static rings is mainly caused by: the flatness and roughness of the end face do not meet the requirements, or there are scratches on the surface; There is particulate matter between the end faces, causing the two end faces to not run equally; Installation is not in place and the method is incorrect.
2. The main reasons for the leakage of the compensating ring sealing ring are: deformation of the pressure cover and uneven pre tightening force; Incorrect installation; The quality of the sealing ring does not meet the standards; The selection of sealing ring is incorrect.
3. Actual usage results have shown that the most frequently failed sealing components are on the end faces of the dynamic and static rings. Cracking on the end faces of the dynamic and static rings of the middle opening pump is a common failure phenomenon, mainly due to:
The gap between the sealing surfaces during installation is too large, and the flushing solution cannot take away the heat generated by the friction pair in time;
The flushing liquid leaked from the gap between the sealing surfaces, causing overheating and damage to the end faces.
The vaporization and expansion of liquid media cause the two end faces to separate due to the vaporization and expansion force. When the two sealing surfaces are tightly adhered, the lubricating film is damaged, resulting in overheating of the end face surface.
The lubricity of liquid media is poor, and coupled with operating pressure overload, the two sealing surfaces do not track and rotate synchronously. When a sealing surface lags behind and cannot track rotation, instantaneous high temperature causes damage to the sealing surface.
The sealing flushing liquid orifice plate or filter screen is blocked, causing insufficient water flow and resulting in the failure of the machine seal.
4.In addition, there are grooves on the surface of the sealing surface, and gaps appear when the end face is in contact, resulting in the failure of the sealing element. The main reasons are:

 

The liquid medium is not clean and contains tiny hard particles that slide into the sealing surface at a high speed, scratching the surface of the end face and causing failure.
The coaxiality of the transmission components of the pump is poor. After the pump is turned on, the end face is rubbed and shaken once every revolution, and the trajectory of the moving ring is not concentric, resulting in end face vaporization and overheating wear.
The frequent occurrence of hydraulic characteristics of liquid media causes vibration of the pump unit, resulting in misalignment of the sealing surface and failure.
Corrosion of sealing components by liquid media, stress concentration, compatibility of soft and hard materials, erosion, incompatibility between auxiliary sealing O-rings, V-rings, concave rings and liquid media, deformation, etc. can all cause surface damage and failure of mechanical seals. Therefore, a comprehensive analysis of the damage forms should be conducted to identify the root cause and ensure long-term operation of mechanical seals.