Operating Problems: Causes And Remedies; The Pump Does Not Prime - Atlas Copco JS Serie Instructions Pour L'utilisation Et L'entretien

13.10 Replacing the TWIN-DISC coupling blocks (RBD series)
- Remove the pump from its seat
- Remove the worn blocks and replace them with new ones
- Check the state of wear of the aluminium flange
- Couple the pump to the engine
- Maximum alignment error: 0.7 mm
- When ordering spare rubber blocks, specify the shaft diameter and the type of coupling.
13.11 Replacing the rubber collar of SURE-FLEX couplings (fig. 23)
- Unscrew the anchor bolts at the base of the pump or motor and separate the two halves
of the coupling
- Remove the worn rubber collar and replace it with a new one. In the case of two piece
rubber collars (type S) leave the steel ring free to move in one of the two grooves near
the indentation
- Move the pump towards the motor and fit the indentation of the half coupling to that
of the rubber collar
- Close the coupling leaving an axial play of 2 mm max. for type J couplings and 3 mm
max. for type S couplings
- Check the radial and angular alignment as follows:
Radial: (fig. 23) with a ruler placed on the outer surface of the half couplings, measure the
maximum misalignment (dimension C) in at least four points around the circumference
and try to bring it as close as possible to zero (see table)
- Angular: (fig. 23) with a gauge, measure at a minimum of four points the distance
between the two halves of the coupling and bring the difference (b-a) as close as possible
to zero (see table)
- Tighten the anchor bolts at the base of the pump and motor
- When ordering spare parts, specify the type of coupling (stamped on the inside of the
half couplings) and the shaft diameter.
13.12 Replacing the rubber dowels of GFB flexible couplings (fig. 24)
- Unscrew the anchor bolts at the base of the pump or engine and separate the two
halves of the coupling
- Remove the worn dowels and replace them with new ones, fixing them in place with a
little adhesive
- Move the pump towards the engine until the coupling is completely closed, then draw
it back by 2-3 mm to separate the two halves of the coupling
- Tighten the bolts which anchor the pump and engine to the base plate
- When ordering dowels, specify the diameter of the shaft and the type of coupling.
14

OPERATING PROBLEMS: CAUSES AND REMEDIES

Attention: before examining the possible causes of operating problems, ensure
that all control instruments (vacuum gauge, pressure gauge, revolution counter,
flow recorder, electrical gauges etc.) are working correctly.
14.1

The pump does not prime

1 The pump casing is empty or non sufficiently full
fill the pump casing through the priming cover or plug (fig. 9)
2 The liquid inside the pump casing is overheated
add cold liquid to the pump casing through the priming cover or plug (fig. 9)
3 Air leaks in the joints or cracks in the suction line
Check that couplings and clamps are tight and inspect the suction line
4 Delivery line under pressure
bleed the delivery line
5 Low rotation speed of the pump
increase the speed only after having verified the contract data and the pump
performance curve
6 The impeller is worn or broken
check the state of the impeller through the impeller inspection cover (26) (fig. 10), or
remove the pump casing as described in paragraph 13.2
7 The cutwater (leading edge of the volute) is worn
remove the casing as described in paragraph 13.2. Build up the cutwater with weld and shape it to restore the original profile.
If the cutwater is severely damaged, replace the casing.
8 The suction strainer (if fitted) is clogged
remove the obstructions
9 The suction lift is too high
reduce the suction lift
10 Air enters through the mechanical seal
disassemble the seal and clean it (see paragraph 13.5, 13.6); if the problem persists, change the seal
11 The suction or discharge lines are obstructed or clogged
locate the obstructed or clogged area and clean
/ JS
JS / JP / JE / JO / JT
www.northridgepumps.com
Max. torque dNm
Max.
Coupling
speed
Cont.
type
(RPM)
duty
8 S 4500 17
10 S 4000 31
10 SS 4000 31
11 S 3500 48
14 S 2800 94
Half coupling
Rubber collar
Half coupling
fig. 23
Coupling C (b-a)
type mm mm
J4 0,25 1,1
J5 0,4 1,4
S6 0,4 1,8
S7 0,5 2,1
rubber dowel
f
ig. 24
Coupling type Max torque kgm
14 15
20 25
27 40
40 60
55 80
88 110
110 150
145 190
180 240
250 300
330 400
Intermitt.
duty
2
30
30
62
121
Torque
N m
10
20
40
70
rpm
4800
4400
4100
3500
3300
3000
2700
2500
2200
2150
2000
19
19