Hemanth Karmali & Deepak Pai- Fomento

PIT WATER MANAGEMENT

MENSURATION PUMP SELECTION STATUTORY REQUIREMENT

MENSURATION

• RAINFALL V/S PIT VALUE DATA • LEVELWISE AREA AND VOLUME • CATCHMENT AREA • WATER LEVEL TO ACHIEVE • TIME FRAME • SEEPAGE • PUMP SELECTION

MENSURATION contd… ™ Rainfall measurement, Catchment area give the idea about the Quantity. ™ Rise in pit water level at particular contour can be used to ascertain quantity. ™ Difference in quantity from catchment area and in pit at that level gives Seepage. ™ In fair season to ascertain seepage, stop the pump for 24 hrs(at least 8hrs), rise in water level can be used to calculate the quantity. ™ Pit bottom shall be surveyed up to date(summer) to calculate the quantity in the pit. ™ Mine plan for the season shall determine the level up to which dewatering is to be done. This will give the quantity. Quantity is devided by no of hrs (say within 2 to 4months as the case may be) to give per hour discharge required.

TYPES OF PUMPS 1) Application Oriented: Domestic pump, industrial pumps, agriculture pumps, lift pumps, submersible pumps, metering pumps,vaccum pumps, dozing pumps, fire fighting pumps 2) Flow and discharge capability: Axial, mixed, radial 3) Material handling Capacity: Acid,slurry,concrete,oil,waste

4) Construction Oriented: Jet Pumps, gear pumps, screw pumps, piston plunger pumps, rotary pumps 5) Types of drives:Engine,electric,pneumatic,hand pump

CENTRIFUGAL PUMP

A centrifugal pump is one of the simplest pieces of equipment. Its purpose is to convert energy of an electric motor or engine into velocity or kinetic energy and then into pressure of a fluid that is being pumped. The energy changes occur into two main parts of the pump, the impeller and the volute. The impeller is the rotating part that converts driver energy into the kinetic energy. The volute is the stationary part that converts the kinetic energy into pressure.

CENTRIFUGAL FORCE

Liquid enters the pump suction and then the eye of the impeller. When the impeller rotates, it spins the liquid sitting in the cavities between the vanes outward and imparts centrifugal acceleration. As the liquid leaves the eye of the impeller a low pressure area is created at the eye allowing more liquid to enter the pump inlet.

CENTRIFUGAL PUMPS ARE CLASSIFIED INTO THREE GENERAL CATEGORIES

CENTRIFUGAL PUMPS

RADIAL FLOW

MIXED FLOW

AXIAL FLOW

Radial Flow - a centrifugal pump in which the pressure is developed wholly by centrifugal force. Pressure developed by centrifugal force only Mixed Flow - a centrifugal pump in which the pressure is developed partly by centrifugal force and partly by the lift of the vanes of the impeller on the liquid. Pressure developed by centrifugal force and kinetic energy Axial Flow - a centrifugal pump in which the pressure is developed by the propelling or lifting action of the vanes of the impeller on the liquid. Pressure developed by kinetic energy

CENTRIFUGAL PUMP COMPONENTS The two main components of a centrifugal pump are the impeller and the volute. The impeller produces liquid velocity and the volute forces the liquid to discharge from the pump converting velocity to pressure. This is accomplished by offsetting the impeller in the volute and by maintaining a close clearance between the impeller and the volute at the cut-water. Please note the impeller rotation. A centrifugal pump impeller slings the liquid out of the volute. It does not cup the liquid.

CAPACITY

A Centrifugal Pump is a variable displacement pump. The actual flow rate achieved is directly dependent on the Total Dynamic Head it must work against. The flow capacity of a centrifugal pump also depends on three (3) other factors:

Pump Design Impeller Diameter Pump Speed

SPECIFIC SPEED The specific speed determines the general shape of a centrifugal pump impeller. As the specific speed increases, the ratio of the impeller outlet diameter to the inlet of the eye diameter decreases. This ration becomes 1.0 for an axial flow pump. Radial flow impellers develop head through centrifugal force. Radial impellers are low flow high head designs. Pump of higher specific speeds develop head partly by centrifugal force and partly by axial force. A higher specific speed indicates a pump design with head generation ore by axial forces and less by centrifugal forces. An axial flow or propeller pump with a specific speed of 10,000 or greater generates its head exclusively through axial forces. Axial flow impellers are high flow low head designs. Specific speed (Ns) identifies the approximate acceptable ration of the impeller eye diameter (D1) to the impeller maximum diameter (D2) in designing an impeller: Ns 500 to 5000 D1/D2 > 1.5 - radial flow pump Ns 5000 to 10000 D1/D2 < 1.5 - mixed flow pump Ns 10000 to 15000 D1/D2 = 1 - axial flow pump

life cycle cost

in. cost main cost 1 2 3 energy cost

LIFE CYCLE ENERGY COST SAVING

‰ Throttling: Most common sloution.Flow is controlled by increasing losses in system.Which means losses of energy. ‰ On and off control: Used incases where stepless control is not necessary for instance when keeping pressure in tank between pre set limits. The pump is either running or stopped. ‰ Variable speed Control: Reduce the speed of the pump and with that flow generated which results in staggering energy savings

PUMP PERFORMANCE CURVE

A Pump Performance Curve is produced by a pump manufacturer from actual tests performed and shows the relationship between Flow and Total Dynamic Head, the Efficiency, the NPSH Required, and the BHP Required. Higher Head = Lower Flow Lower Head = Higher Flow Lower Flow = Lower Horsepower Higher Flow = Higher Horsepower

UNDERSTANDING CENTRIFUGAL PUMP PERFORMANCE CURVE The capacity and pressure needs of any system can be defined with the help of a graph called a system curve. Similarly the capacity vs. Pressure variation graph for a particular pump defines its characteristic pump performance curve. The pump suppliers try to match the system curve supplied by the user with a pump curve that satisfies these needs as closely as possible. A pumping system operates where the pump Curve and the system resistance curve intersect. The intersection of the two curves defines the operating point of both pump and process. However, it is impossible for one operating point to meet all desired operating conditions. For example, when the discharge valve is throttled, the system resistance curve shift left and so does the operating point.

DEVELOPING A SYSTEM CURVE

The system resistance or system head curve is the change in flow with respect to head of the system. It must be developed by the user based upon the conditions of service. These include physical layout, process conditions, and fluid characteristics. It represents the relationship between flow and hydraulic losses in a system in a graphic form and, since friction losses vary as a square of the flow rate, the system curve is parabolic in shape. Hydraulic losses in piping systems are composed of pipe friction losses, valves, elbows and other fittings, entrance and exit losses, and losses from changes in pipe size by enlargement or reduction in diameter.

DEVELOPING A PUMP PERFORMANCE CURVE

A pump's performance is shown in its characteristics performance Curve where its capacity i.e. flow rate is plotted against its developed head. The pump performance curve also shows its efficiency (BEP), required input power (in BHP), NPSHr, speed (in RPM), and other information such as pump size and type, impeller size, etc. This curve is plotted for a constant speed (rpm) and a given impeller diameter (or series of diameters). It is generated by tests performed by the pump manufacturer. Pump curves are based on a specific gravity of 1.0. Other specific Gravities must be considered by the user.

NORMAL OPERATING RANGE A typical performance curve (Figure D.01) is a plot of Total Head vs. Flow rate for a specific impeller diameter. The plot starts at zero flow. The head at this point corresponds to the shut-off head point of the pump. The curve then decreases to a point where the flow is maximum and the head minimum. This point is sometimes called the run-out point. The pump curve is relatively flat and the head decreases gradually as the flow increases. This pattern is common for radial flow pumps. Beyond the run-out point, the pump cannot operate. The pump's range of operation is from the shut-off head point to the run-out point. Trying to run a pump off the right end of the curve will result in pump cavitation and eventually destroy the pump.

Affinity Laws The affinity laws lay down the relationship between hydraulic characteristics and rotational speed of centrifugal pumps. Specific cases can use the general rule as follows: 1st Model Law

2nd Model Law

3rd Model Law

Q = flow H = head P = power input N = speed

H1 H2 N1 N2

Impeller Trimming Impeller trimming means the reduction of the impeller diameter to adjust the pump performance to the duty point.

Q = flow rate H = head D = impeller size The indices relate to the respective impeller diamete

NET POSITIVE SUCTION HEAD

A liquid cannot be towed in a suction pipe like a wheeled VIP suitcase. To make it flow it must be pushed from behind by some external energy, force or head. Atmospheric pressure provides this head on the free surface of liquid from which the pump draws the liquid. FACTORS DEPENDS 1)Atmospheric pressure. 2) Absolute vapor pressure of liquid at pumping temperature. 3)Friction losses in suction pipe. 4) Suction Lift.

NPSH (NET POSITIVE SUCTION HEAD) NPSH= Ha- hvp+ hst Ha= atmospheric pressure in mwc hvp= vapour pressure hst= Total suction lift/ suction head NPSH(A) : NPSH AVAILABLE IS A FUNCTION OF THE SYSTEM. NPSH(R) : NPSH REQUIRED IS THE FUNCTION OF PUMP DESIGN

FOR SATISFACTORY PUMP OPERATION NPSH(A) > NPSH(R)

8 WAYS TO MURDER

™ OVERWORK IT: Run pump at higher capacities, head, speed. ™ STARVE IT: Do not feed pump with oil/grease. ™ STAB IT: Open the suction cover, fill it with sand, grit. ™ POISON IT: Change the fluid you are pumping. ™ CHOKE IT: Make NPSH available less than required by the pump. ™ FRY IT: Operate the pump at shut off for a long time. ™ SHAKE IT TO PIECES: Run the pump in misaligned condition. ™ NEGLECT MEDICICAL CHECK UPS: Avoid periodical check ups.

MAINTAINANCE DAILY CHECKS 1. PRESSURE GAUGE READINGS 2. BEARING TEMPERATURE 3. OIL LEVEL/GREASE IN BEARING HOUSING 4. NOISE & VIBRATIONS 5. VOLTAGE & CURRENT 6. PUMP SHOULD NEVER RUN DRY

PERIODICAL CHECKS 1. CHECK THE ALIGNMENT OF PUMPSET 2. CHECK THESEALING CONNECTIONS

CHECKS DURING RUNNING/OPERATION

1. PUMP IS RUNNING SMOOTH. CHECK 2. NO MECHANICAL FRICTION IN PUMP 3. POWER CONSUMPTION WITHIN LIMIT 4. HEAD AND CAPACITY DEVELOPED BY THE PUMP IS AS SPECIFIED ON THE NAME PLATE 5. BEARINGS ARE NOT GETTING HOT 6. GLAND LEAKAGE IS NORMAL 7. PUMP SHOULD SWITCHED OFF ONLY AFTER CLOSING THE DELIVERY SIDE VALVE

PRE COMMISSIONG CHECKS ¾ PUMP ROTATES FREELY ¾ DIRECTION OF ROTATION OF MOTOR/PUMP IS CORRECT ¾ OIL LEVEL IN BEARING ¾ ENSURE PRIMMING ¾ VALVE ON DELIVERY SIDE IS CLOSED ¾ PUMP SET LEVELLED PROPERLY ¾ ALLOW ENOUGH SPACE AROUND PUMP ¾ FOUNDATION SHOULD BE SUFFICIENTLY RIGID TO ABSORB SHOCKS ¾ PROPER PIPE SIZES ¾ PROPER SUPPORTS ¾ PROVIDE NRV AND GATE VALVE IN DELIVERY LINE

SAFETY REQUIREMENTS • LAND BASED and PONTOON PUMPS • CLEAN AND TIDY ARRANGEMENTS • FENCING • LIFE GUARDS & JACKETS • LIGHTING • FIRE EXTINGUISHER • CERTIFICATION CONSTRUCTION OF PONTOON • LIFE GUARD & JACKET • CODE OF PRACTICE • ELECTRICAL SAFETY • VOCATIONAL TRAINING FOR OPERATORS • FIRST AID BOX

Code of practice: is the document which gives the comprehensive topic wise aspects to be followed during operation, maintenance of the pontoon and pumps.

Construction and certification of Pontoon: pontoon should have more than one tanks, Pressure testing is required, Draught levels should be noted and watched for any change, Man holes for inspection, stability tests, Certificate from Naval architect.

PUMPING AND COSTS • Pumping is inevitable for mining below water table • In one of our cases it goes 10% of per ton digging cost • Cost can be controlled by • Selection of right pumps • Operating the pumps in the curve range • Minimizing friction loss in delivery pipeline • Efficient prime movers • Operating the pumps round the clock

PIT TO PIT DEWATERING • USE OF SUBMERRISBLE PUMPS