Twinro - Outboard
Revision 2–15 January 2008
2.0DESCRIPTION & PRINCIPLE OF OPERATION
The Plenty Twinro Pump is a positive displacement twin screw design.
The pump is usually supplied horizontally mounted on a bedplate, directly driven by an electric motor.
through a flexible coupling.
The pumping element consists of two contra-rotating rotors, one above the other, each carrying a right and left hand screw form. The fluid being handled is pumped from each end of the pump body to a delivery annulus at the centre. See Fig. 1.
Fig. 1
The rotors are supported at each end by anti-friction bearings. The driving rotor is provided with a shaft extension through which the motor drive is transmitted. Timing gears keyed to the rotor shafts, and enclosed in a gearbox case at the non-drive end of the pump body, ensure synchronised rotation of the rotors.
Four mechanical seals are fitted thus enabling the gearbox case and bearings to be sealed from the fluid being pumped. This enables the pump to handled non-lubricating fluids such as water, petrol etc.
The timing gears and ball bearings are lubricated by means of an oil supply contained in the gearbox case. An oil window provides indication of the oil level. The drive end roller bearings are grease lubricated via grease nipples on the covers.
3.0 STORAGE & LIFTING
3.1 Storage
Ifthe pump is not to be installed immediately on receipt at site, please contact Plenty Ltd.for storage instructions.
3.2Lifting
See General Arrangement Drawing for unit weight,
and use only suitably rated lifting equipment.
Bedplate mounted units should be lifted by attaching slings to bars fitted through the holes provided in the bedplate.
Eye-bolts fitted to motors and gearboxes are for lifting individual components only, and must not be used for lifting unit.
For lifting a pump off a bedplate, slings should be fitted around pump branches.
4.0INSTALLATION
4.1Foundations
It is recommended that bedplates are mounted and grouted in on suitable re-inforced concrete plinths.
The plinth should be constructed to extend 50-75mm all round from the extremities of the bedplate. Cored holes should be provided to accept the foundation bolts so that they may hang freely from the bedplate before they are grouted in.
4.2Shaft Alignment
Pump and driver shafts will have been aligned prior to unit despatch from the factory.
It is essential to ensure bedplate is not twisted during bolting to plinth, otherwise correct re-alignment may be impossible.
Steel wedges should be positioned under bedplate adjacent to each grouted in foundation bolt.
Dial test indicators should be attached to coupling halves (after removing element if spacer or steel element coupling type fitted in order to measure misalignment at coupling periphery and faces. See Fig 2.
Fig. 2
Rotate both coupling halves together, record D.T.I. readings at 4 positions 90 Degrees apart.
If total indicated reading exceeds values in Table 1, adjust wedges as necessary to restore acceptable alignment. Re-check after fully tightening foundation bolts.
Pump Speed(RPM) / Up to750 / 750-1500 / 1500-3000 / 3000+
Periphery
T.I.R. (mm) / 0.3 / 0.25 / 0.2 / 0.15
Faces
T.I.R. (mm) / 0.3 / 0.25 / 0.2 / 0.15
Table 1
When unit is finally aligned, wooden shuttering should be built up around plinth and grouting poured level with underside of foundation bolt head. Depending on bedplate design, further grout may be introduced under deck of bedplate, after first blanking openings as appropriate.
4.3System Pipework
Pump should be positioned as near as possible to source feeding it, e.g., storage tank.
Suction pipework must be no smaller in diameter than pump suction branch and designed to avoid unnecessary sharp bends inverted loops, change in section or undue restriction.
Pressure drop through non-return valves and quick-release couplings can be considerable and must be taken into consideration.
Nett Positive Suction Head (N.P.S.H.) available must be greater than pump requirement.
If required for use on a 'static' suction lift condition it is important to design pipework to prevent complete draining of system. This can be achieved by pipework arrangement as shown in Fig. 3, or by inclusion of non-return valve(s).
Fig. 3
Care should be taken to eliminate the possibility of a dry pump having to start against a static head on delivery side of pump.
New pipework must be cleaned prior to assembly to remove weld spatter and pipe scale. Adequate pipe supports should be provided to minimise strain at pump branches. In a new installation, closing lengths of pipe either side of pump should be always left until the pump is in position. These should then be assembled, complete with correct gaskets, and flanges tack welded in position. The pipes can then be taken down for welding and finally re-assembled, after cleaning out thoroughly.
Under no circumstances should mis-aligned bolt holes be levered into alignment or gap between flanges closed up by tightening flange bolts.
Blank off the pump if subjecting the pipework to hydraulic test or flushing.
4.4 Bearing housing leak-off tappings.
Leak-off holes are provided in bearing housings to
prevent ingress of pumped liquid into
gearbox/bearings in the event of mechanical seal
failure.
Tapped holes are fitted with red plastic protective
plugs, which should be removed prior to running
the pump.
Warning : / If leakage of the liquid pumpedcould present a hazard, the lower of
these tapped holes (1" BSPT) at each
bearing housing must be connected
to pipework allowing draining of
leakage to a safe area.
5.0COMMISSIONING
Safety note : Ensure electric supply is isolated and product valves are closed before starting work.
5.1Gearbox oil fill
Caution : / Gearboxes are drained of oilprior to shipping, and must be
filled prior to start - up.
Determine the appropriate grade and quantity of oil from Table 2 below.
PumpSize / W80 / W125 / W225 / W375
Approx. Oil
Quantity
(litres) / 1.6 / 1.6 / 3.3 / 2.5
Ambient Air Temp.
(0 C) / Max. Oil
Temp.
(0 C) / I.S.O.
Viscosity
Grade
Min. / Max.
-11 / 5 / 60 / 68
1 / 21 / 75 / 150
14 / 36 / 90 / 320
Table 2
Remove filler plug/vent from top of gearbox and add oil until level is half-way up sight glass window. Re-fit plug.
5.2System cleanliness
If possible a check on internal cleanliness of pipework should be carried out, particularly on unprotected suction line i.e. between suction filter and pump. This must be free of rust, scale and weld debris.
Filter basket should be removed and checked for mesh size and cleanliness, also temporary strainer if fitted.
5.3Pipework Strain
To ensure undue forces are not present, flange bolts (suction and discharge) should be completely slackened. If flanges are observed to spring apart, twist or move out of parallel excessively, remedial action must be taken.
5.4Coupling Alignment
A final check on coupling alignment should give same results as when bedplate was installed - if movement has occurred, investigate cause (which is likely to be misaligned pipework). This must be rectified before proceeding.
In the case of a 'hot' pump, final alignment should be carried out with the unit at operating temperature to allow for thermal expansion.
5.5External relief valve
If external relief valve is fitted, check setting.
5.6.Freedom of movement
Ensure pump rotates by hand.
5.7Special Requirements
Where seal flush/quench is provided check for correctly installed pipework. Any other special features should be checked.
When bearing constant level oilers are used.
Caution : / Bearings may be drained of oilprior to shipping, and must be
filled prior to start - up.
I.S.O. Viscosity
Grade / 100
Ensure there is oil visible in the bottle.
If necessary the oil must be filled by tipping the bottle back on its hinge and pouring oil into the bottle via the tube, then swiftly releasing back into its vertical position.
6.0. INSTRUMENTATION
Instruments should be provided to indicate operating suction and discharge pressure. Connections should be taken from tapped holes in pump body.
Gauge cocks or snubbers will be required to dampen pressure gauge vibration.
A compound gauge (pressure/vacuum) should be used on suction.
Diaphragm type gauges are recommended if product is liable to solidify when cooled.
On a hot duty, temperature measurement of product should be provided by thermowell pocket in pipework.
An ammeter is recommended to indicate motor current.
7.0START - UP
7.1If heating is necessary, turn on supply and allow pump temperature to stabilise.
7.2If pump is below level of liquid in tank (flooded suction), open appropriate system valves gradually, checking for signs of leakage.
Vent air from pump by slackening vent plug or opening vent valve.
Caution : / Do not completely remove plug or fully open valve.Be prepared for product leakage after air is expelled.
If the pump is above the level of liquid in the tank (suction lift), prime the pump by pouring as much liquid as possible into the pipework adjacent to the pump - particularly on the suction side.
Also ensure the pump is filled, by pouring liquid into the pump vent connection.
7.3Energise power supply to motor starter.
(To be carried out only by qualified electrician).
7.4Check pump rotation by quickly flicking motor starter 'on' then 'off'.
(Correct rotation indicated by arrow on pump).
Warning : / It may be necessary to remove guard to observe rotation. In this case extreme caution must be exercised to avoid personal injury.If incorrect, alter rotation by changing over two motor supply conductors .
(To be carried out only by qualified electrician).
7.5Ensure guards are correctly fitted.
7.6Start pump.
Ensure pump is delivering product.
If not, stop immediately and investigate
7.7Check pump and system for leaks.
NOTE : Packed gland leakage is normal - see Section 8.
7.8Check surface temperature around bearing housing and pumping element relative to the product temperature.
7.9Check relief valve operation. - see Section 8.
Emergency or Routine Shutdown
The pump can be switched off immediately.
Warning : / Always stop the pump before closingdischarge valve.
8.0Relief Valve
Caution :A relief valve is necessary to protect the pump and system from potentially dangerous over-pressure. The relief valve will operate in the event of a restriction in the discharge line or the inadvertent closure of a downstream valve.
The valve must not be used as a flow control device.
If pump is supplied without an integral relief valve, a suitable external relief valve must be incorporated.
An integral relief valve will have been factory set during pump performance test.
Correct operation should however, be checked as part of commissioning procedure.
Re-adjustment may be necessary due to viscosity variation.
8.1Relief Valve Setting
Run pump with suction and discharge valves fully open.
Ensure any air is vented from system.
In the case of a flooded suction, vent pump body and relief valve housing (where appropriate).
If negative suction exists it will be necessary to operate relief valve (see below) once or twice to expel trapped air.
Determine relief valve full by-pass pressure from specification sheet.
To operate relief valve, slowly close down discharge valve adjacent to pump while watching discharge pressure gauge.
Caution :If at any time it is observed that discharge
pressure exceeds specified relief valve full
bypass pressure DO NOT CONTINUE TO
CLOSE VALVE ANY FURTHER. Instead, back off discharge valve and reduce spring
load on relief valve by screwing adjusting screw (510) anti-clockwise. After adjustment, lock gland (511).
If it is necessary to increase spring load, gland (511) should be slackened before screwing in adjusting screw (510). After adjustment, lock gland (511).
Repeat procedure until it is possible to fully close discharge valve with pressure gauge recording specified full by-pass pressure.
8.2. Valve Characteristic Adjustment
In addition to the adjustment of spring load as described above, the valve fitted to the Twinro pump has the facility to adjust the valve characteristic.
This will have been set during factory test, and will not normally need to be re-adjusted.
However, if the pump is to be used on a different duty to that originally specified, or if the factory setting has been altered, the following procedure should be carried out.
1.Operate relief valve by closing discharge valve as described above, paying regard to safety warnings.
2.If it found that discharge pressure starts to rise, but then falls when continuing to close valve, this is termed an 'off-loading characteristic'.
It should be rectified by screwing throttle screw (514) in an anti-clockwise direction.
3. If it is found that discharge pressure rises excessively above set pressure when the discharge valve is closed, this is termed a 'rising characteristic'.
To reduce this rising effect the throttle screw (514) should be screwed in a clockwise direction.
R.V. characteristic
Fig.4
Adjustment of screw should be carried out in small increments (quarter turn at a time) to determine the optimum setting - usually resulting in a slightly rising characteristic.
To carry out adjustments, first isolate pump by closing valves, and then partially drain pump of product prior to removing plug (505) to gain access to throttle screw (514).
An 8mm Allen type hexagon wrench is required.
The screw thread is 'self-locking'.
Following adjustment of throttle screw (514), it may be necessary to re-adjust valve adjusting screw (510) as described above.
9.0. ROUTINE MAINTENANCE
Interval Action
Every 150 HrsCheck for leaks.
Check for excessive noise/vibration.
Check, and top up if necessary, gearbox oil level.
Check, and top up if necessary, bearing oil level via the constant level oilers, if constant level oilers
are used.
Every 1500 HrsCharge drive end bearing, grease nipples using No.2 lithium based grease, or re-fill constant level oilers
if this applies.
(Operating temp. up to 120 0 C when
No.2 Lithium based grease is used.)
Every 6000 HrsDrain, flush gearbox and refill with oil.
See Table 2 for quantity and specification of oil.
NOTE :Check motor instructions for routine maintenance required.
10.0. TROUBLE SHOOTING
Under each fault symptom given below is a list of recommended inspections that could indicate the cause of the problem, most of them are elementary but are often overlooked.
The best aid to fault finding in Positive Displacement pumps is the fitting of a vacuum gauge as close as possible to the pump inlet. This can readily indicate whether the imposed suction condition is within the pump's capability, or if there has been a dramatic change from normal conditions, which will indicate a change in the viscosity of the pumping media, resulting in higher pressure loss in the suction line, or that a filter requires cleaning, etc.
No liquid delivered/pump does not prime
Check the following :-
Direction of shaft rotation.
Are Suction line joints and fittings allowing ingress of air?
Is leaking seal allowing ingress of air?
Total suction condition, i.e. is there sufficient N.P.S.H. available ?
Has pump been properly primed before start up?
Is suction port blocked. Is filter clean ?
Relief valve setting must be well above operational duty.
All valves in the system are open.
Media reservoir level and amount of aeration in product. Can vortex permit ingress of air?
Is return line below level of product in the tank. Is return line well away from suction?
Has pump been fully vented ?
Caution : / The gauge on the suction side should be checked. If it is reading over -0.7 bar there is almost certainly a blockage in the suction line. Where the suction condition is flooded, availability of fluid at the pump suction can be checked by opening a test cock in the line.Pump noisy when operating
Check the following :-
Is product close to vaporising pressure?
Is viscosity and temperature of media as specified?
Is return line below level of product in the tank?
Is relief valve setting too close to operating duty?
Suction valve partially closed.
Pump internals may be worn.
Total suction condition, i.e. is there sufficient N.P.S.H. available?
Is level of product too low.
Reduction in output or discharge pressure
Check the following :-
Are suction line fittings allowing ingress of air?
Is liquid level in tank sufficient?
That relief valve is not in a partially open condition.
Is speed of prime mover as specified ?
Is suction port - filter partially blocked?
Is temperature of media as specified ?
Check pump internals, may be worn.
All valves in system are open.
Pump Runs Hot
Check the following:-
Temperature and viscosity of the pumping media.
Relief valve setting. Is R/V bypassing?
Pumping media for contamination, i.e. sand,
weld, etc.
Is pump running dry. Has pump been primed?
Are all valves open?
Pump internals may be worn or damaged.
Electric motor overheats
Check the following:-
Prime mover speed and current consumption
against the manufacturer's figures.
Viscosity of pumping media.
That motor air flow is unrestricted.
Freedom of rotation of the pump and motor
11.0. WORKSHOP OVERHAUL
No special tools are required.
The tools of a well equipped maintenance workshop should be suitable.
It is recommended that the pump is removed from its bedplate and taken to a workshop before dismantling.
If re-use of components is anticipated, mark parts as dismantled to enable re-assembly in same position.
11.1. Removal of Pump from Bedplate
Shut down and immobilise the prime mover; if this is an electric motor, remove the fuses.
Shut and lock the pump delivery and suction valves.
Remove the coupling guard.
Remove the coupling bolts (Spacer type coupling) or release Taper-lock bush to allow the coupling hub to be slid along the shaft.
Drain the fluid from the pump.
Disconnect all pipework from the pump.
Blank off or fit protective caps to all open pipe
ends and flanges.
Remove the pump holding down bolts.
Using suitable tackle, lift the pump from the
bedplate.
11.2.Pump Strip-Down
Remove pump coupling half/taper-lock bush; locate and retain key.
Gearbox
Drain gearbox oil.
Remove gearbox case (112) with gasket (114).
Remove screws (405) and withdraw timing gears (121/122) and keys (120).
Mark gears/keys to ensure they can be re-fitted in same position.
Note that on sizes W125-W375 the driven gear is doweled to a hub (131). It is not necessary to separate these components unless the gears are to be replaced or the screwset is to be re-timed.
Remove gearbox mounting plate (111) and gasket (109) from bearing housing.