32-differences between centrifugal pumps and reciprocating pumps

COMPARISON BETWEEN CENTRIFUGAL PUMPS & RECIPROCATING PUMPS
Sl No.	Centrifugal pump	Reciprocating pump
1	It is dynamic type pump	It is a positive displacement pump
2	It produces more flow	It produces lesser flow
3	It produces less head (pressure) for same size of pump	It produces more head (pressure) for the same size of pump
4	Work is done by rotating the impeller	Work is done by back & forth movement of piston or plunger or diaphragm
5	Simple construction	Complex construction
6	Simple operation	Complicated operation
7	Smoother operation no vibrations	Due to reciprocating movement vibrations are always there
8	Continuous supply of fluid	No continuous supply of fluid
9	Pressure increases by decreasing the flow	Flow is independent on pressure
10	High viscosity fluid cannot be pumped easily	High viscosity fluids can be p[umped very easily
11	Low viscosity fluids can be pumped very easily	Cannot be pumped very easily
12	Centrifugal pumps are low costlier	More costlier than centrifugal pumps
13	Maintenance is easy	Maintenance is difficult
14	Less maintenance cost	More maintenance cost as there are more rotating & moving parts in pump
15	Grease & oil lubricated	Most of the pumps are oil lubricated only
16	Cab ne installed easily	Complicated installation
17	Require less space for same size pump	Require more space for same size pump
18	Less accurate in flow measurement	More accurate for flow measurement
19	Not suitable for small quantity dosing system like chemical plants or water treatment plants	Best for small & accurate quantity dosage like in water treatment plants to maintain desired water parameters
20	Priming is required for centrifugal pumps	Priming is not required
21	Pumps can be started with discharge valve closed condition	Pumps cannot be started with discharge valve closed condition
22	In consists of impeller to create head & flow	In consists of plunger, pistons & diaphragms to create head & flow
23	Centrifugal pumps might be of positive as well as negative suction	Most of the reciprocating pumps are of positive suction
24	PRV is not required	PRV is required to protect the pump during discharge line blockage
25	Minimum recirculation system is there to protect pump at lower discharge flow	Recirculation line is not required as head is independent of flow
26	Pump major internal parts are impeller, wear ring, shaft sleeve, stuffing box, lantern ring, balance & counter balance disc  etc	Pump major internal parts are, connecting rod, crank, piston, plunger, diaphragm, gears etc
27	Reverse rotation of the pump affects pump performance & capacity	Reverse rotation of the pump does not affect much
28	Pipe lines have fittings like eccentric & concentric reducer	Eccentric & concentric reducers are not used
29	Generally air vessels are not used in reciprocating pumps	Air vessels are used in reciprocating pumps
30	Thrust balancing is required in high pressure centrifugal pumps	Thrust balancing is not required
31	Cavitation can damage pump internals & related piping system	Cavitation does not affect much
32	For same flow foundation required  is not much robust & strong	Strong & robust foundation is required

Reference books for power plant O&M

Reciprocating pumps

Reciprocating pumps parts

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Chain conveyor troubleshoot guide

 

Sl No.	Problems	Potential Cause	Solution
1	Chain rises off from sprocket	1. Excess chain slack.	1. Adjust the amount of slack equally at both sides.
		2. Excess wear at the bases of sprocket teeth.	2.Carryout hard facing of the sprockets
		3. Excess chain extension.	3. Replace the elongated chain parts.
		4. Foreign material stuck to the bases of sprocket teeth.	4. Remove the foreign material from the bases of the teeth.
		5.Reverse rotation of conveyor	5.Avoid reverse rotation of the conveyor when chain tightened is uneven
		6.Uneven chain tightening of chain
2	Chain separates poorly from the sprocket.	1. Sprocket misalignment.	1-Adjust alignment.
		2. Excess chain slack.	2-Adjust the amount of slack.
		3. Excess wear at the bases of sprocket teeth.	3-Avoid uneven tightening of the chain
		4.Uneven chain tightening of chain
3	Wear to sides of link plats and sprockets	1-Sprocket misalignment.	1-Adjust alignment.
		2-Trough width is lesser than required	2-Increase trough & runner flat width as per site conditions & links assembled width
		3-Chain runner flats size is less
4	Poor chain flexure	1-Inadequate oiling/lubrication	1-Lubricate properly, use standard lubricant during chain assy.
		2-Foreign materials between pins and bushes.	2-Wash the chain to remove foreign materials, and then oil it.
		3-Corrosion between bushes.	3-Replace with an environment resistant chain series.
5	Abnormal noise	1-Chain is too tight or too loose.	1-Adjust the chain slack.
		2-Inadequate oiling.	2-Lubricate properly.
		3-Excess wear of sprockets and chain.	3-Replace chain and sprockets or get worn-out area filled & hard face it
		4-Sprocket misalignment.	4-Eliminate contact with the case.
		5-Slats touching the trough
6	Chain vibration	1-Excess chain slack.	1-Adjust slack.
		2-Excess load vibration.	2-Reduce load variation
		3-Excess chain speed leading to pulsation.	3-Use guide stoppers to stop chain swaying.
		4-Chain flexes poorly at some points.	4-Replace the more worn-out chain parts during overall maintenance
		Sprocket wear.
		5-Worn out or more clearances in rollers & bushes
7	Damage to pins, bushes, rollers.	1-Inadequate oiling.	1-Lubricate properly.
		2-Jamed foreign bodies.	2-Remove foreign bodies.
	Deformation of link plate holes.	3-Corroded components.	3-Review chain and sprocket selections.
		4-Use with greater than allowable load.	4-Eliminate the abnormal load, and review chain and sprocket selections
		5-Abnormal load action.
8	Chain link cut or pins cut	1-Overload operation	1-Ensure all over load, ZSS protections are working
		2-Low breaking load of chain	2-Select chain with higher breaking load if this problem persists

Points to be kept in mind

1-Never weld the heat treated chains, as heat effect can reduce the strength & cause chain to break

2-Never go for electroplating of heat treated chain links, as it causes the hydrogen embrittlement failure

3-Do not use new chain on worn out sprockets

4-Gradual elongation of chain above 3%  in total chain length, indicates that the chain will soon jump the sprockets

Read SOP Coal handling & DE system