1.Round nut ; 2.Shaft ; 3.Grease retainer ; 4.Frame 5.Bearing ; 6.Labyrinth ;
7.End cover ; 8.Shaft sleeve ; 9.Gland assembly ; 10.Lantern ring ; 11.Packing ;
12. Expeller ; 13.Oil cup ; 14.Discharge joint ; 15.Frame plate ; 16.Oil cup seat ;
17. Expeller ring ; 18. FPL insert ; 19.Impeller ; 20.Volute ; 21.Cover plate ; 22.Intake joint.
Why is the outlet valve closed when the centrifugal pumps is started?
Answer: Because the centrifugal pumps flow is equal to zero, the power is the smallest. In this way, the starting current of the motor can be reduced and the motor can be protected.
How are the rated flow, head and power of the centrifugal pumps specified?
Answer: The flow, head and power when the centrifugal pumps is the most efficient are set as the rated flow, head and power of the centrifugal pumps.
What are the consequences of cavitation in centrifugal pumps?
Answer: (1) produce noise and vibration;
(2) With the reduction of flow, head and efficiency, it is even impossible to operate;
(3) The impeller casing and blades have pitting and honeycomb damage, which may even cause the casing to penetrate;(4) Damage to the pumps shaft.
Does the flow change of centrifugal pumps in normal operation generate radial force?
Answer: It can generate radial force. Because the change in flow makes the pressure distribution around the impeller uneven, radial forces acting on the impeller are created.
What kind of harm will the existence of radial force of centrifugal pumps cause?
Answer: Because the radial force of the centrifugal pumps acts vertically on the pumps shaft, the pumps shaft will have a large deflection (public number: pumps housekeeper), and the rotating shaft will be subjected to the force of the alternating load. The presence of the force will make the pumps shaft fatigue and damage.
What measures have been taken to eliminate the axial force in the design of centrifugal pumps?
(1) Balance holes, balance discs, balance tubes and balance drums are used;(2) Impeller double suction;(3) Use thrust bearings;(4) Use the symmetrical arrangement of impellers, etc.
What is the main reason that the centrifugal pumps does not fill the water?
(1) There is gas in the pumps inlet and inlet pipe;(2) The viscosity of the medium increases, which is inconsistent with the design;(3) Leakage of inlet pipeline or mechanical seal;(4) The inlet pipeline is blocked;(5) The number of revolutions of the pumps does not reach the rated number of revolutions;(6) The pumps is reversed;(7) The gap of the mouth ring is too large.
The main reason for centrifugal pumps vibration?
(1) The coupling is not concentric;(2) The bending degree of the shaft exceeds the standard;(3) The bearing clearance is too large or damaged;(4) The rotor is unbalanced;(5) The rotor and the stator generate friction;(6) The medium carries gas and has cavitation phenomenon;(7) The pumps is evacuated;(8) There are foreign objects in the impeller flow channel;(9) The unreasonable installation of the process pipeline makes the pumps subject to external force.(10) Long-term low-load operation;(11) The influence of the vibration of the auxiliary pipeline;(12) The anchor bolts are loose.
What are the reasons for the overheating of centrifugal pumps bearings?
(1) The rolling bearing is of poor quality or worn during operation;(2) The sliding bearing clearance is too small;(3) The bearing housing is not well cooled;(4) Insufficient or excessive amount of lubricating oil and grease or impurities.
There are several reasons for the excessive current of the centrifugal pumps motor?
(1) The medium is too heavy or the viscosity is too large and does not match the design;(2) Serious friction occurs between the rotor and the housing;(3) The coupling is not concentric or the bearing is worn.
Which types of centrifugal pumps rotors are generally installed only need to find static balance?
(1) Single-stage pumps;(2) Multistage pumps rotor with smaller diameter;(3) A rotor with a lower speed.
Which types of centrifugal pumps rotors must be dynamically balanced?
(1) There are many impellers;(2) The diameter is larger;(3) Rotor with high speed.
What are the methods for aligning the coupling?
(1) Find the correct method in a single table;(2) Double-table finding the right method;(3) Three tables to find the correct method.
What are the reasons for the unstable or large fluctuation of the pointer of the pressure gauge at the outlet of the centrifugal pumps?
(1) The pressure gauge damage indication is not working;(2) pumps evacuation or flow fluctuation;(3) There are impurities or blockages in the pipeline;(4) pumps vibration;(5) There is gas in the pipeline or pumps casing;(6) Cavitation.
What is the effect of centrifugal pumps evacuation on mechanical seals?
(1) It will cause a large amount of leakage of the mechanical seal;(2) Destroy the sealing surface of the mechanical seal or even cause damage.
What is the general maximum allowable value of centrifugal pumps shaft bending?
At the journal: no more than 0.02mm;
Middle shaft:(1) 1500 rpm is not more than 0.08mm;(2) 3000 rpm is not more than 0.06mm.
What is the general requirement for the clearance of the centrifugal pumps mouth ring (expressed in fractions)?
Answer: For pumps used at normal temperature, when the diameter of the mouth ring is less than 100mm, the diameter gap is 0.5mm. If it is greater than 100mm, it is 0.5+(D-100) × 0.002 (D is the diameter), and 0.1mm is added when the temperature is high.
What are the consequences of too large or too small a centrifugal pumps ring gap?
(1) The gap of the mouth ring is too large, and the efficiency of the pumps cannot be reduced;
(2) The clearance of the mouth ring is too small, which will cause friction and even cause the shaft to be held.
What work must be done before the centrifugal pumps is overhauled and debugged?
(1) Check the maintenance work steps;(2) Carry out cranking;(3) Open the inlet valve, and the high-pressure pumps slightly opens the outlet valve;(4) Open the empty valve;(5) Start the pumps and pay attention to the direction of rotation;(6) It can be put into use after checking the operation condition and meeting the requirements.
What is the purpose of centrifugal pumps cranking?
Answer: The main purpose is to avoid the bending deformation of the shaft due to its own weight or friction.
