MDX [en-US]
36
Forward Flush and Throat Bushing stuffing boxes are generally pressure controlled, but flow control is an option. Seal
water requirements listed in the table show potential flow with worn packing.
Flow control may be achieved in different ways. A Positive Displacement pump that delivers the correct volume can be
used with a safety or “pop-off” valve so the purge pressure can never exceed 10 psi (0.7bar) above the Maximum
Working Pressure of the pump. Where water supply is adequate, install a flow meter and regulating valves in the line.
A backflow preventer is recommended to prevent reverse flow should the pump pressure exceed supply pressure. All
components must have adequate pressure ratings. Verify that components will work with the volume, pressure and
water quality supplied to the stuffing box.
For best performance each pump should be adjusted for minimum water consumption while still providing adequate
drip rate. As the volume of water is reduced, the stuffing box gland will need to be loosened slightly to maintain the
proper drip rate. This will ensure adequate flush while limiting water use. The temperature of the water exiting the
stuffing box can be a better indicator than “drip rate” or volume. This should be at a temperature that would be
comfortable for hand washing which indicates that the packing is not overheated.
Stuffing Box Maximum Seal Water Requirements
For hot, high pressure or otherwise severe service conditions, an optional combination lantern ring / throat bushing is
recommended in place of the standard lantern ring and first ring of packing. Water requirements for this option will be
about mid-way between the forward flush and KE configurations shown in the table below.
For expeller applications, the stuffing box used must be of the ‘KE’ (low flow) type with a ring of packing between the
lantern ring and pumped fluid. All rings of packing should be well coated with water resistant grease during assembly.
Shaft
Size
Stuffing Box Type
Throat Bushing
KE Design
Forward Flush
*SpiralTrac™
L/sec
(gpm)
L/sec
(gpm)
L/sec
(gpm)
L/sec
(gpm)
2 - 7/16
0.32
(5.0)
0.13
(2.0)
0.63
(10.0)
0.24
(3.8)
2 - 15/16
0.38
(6.0)
0.19
(3.0)
0.76
(12.0)
0.28
(4.5)
3 - 15/16
0.63
(10.0)
0.25
(4.0)
1.26
(20.0)
0.47
(7.5)
4 - 7/16
0.82
(13.0)
0.32
(5.0)
1.58
(25.0)
0.62
(9.8)
5 - 7/16
0.95
(15.0)
0.38
(6.0)
1.89
(30.0)
0.71
(11.3)
6- 7/16
1.70
(27.0)
0.69
(11.0)
3.47
(55.0)
1.32
(21.0)
7 - 3/16
1.77
(28.0)
0.69
(11.0)
3.47
(55.0)
1.32
(21.0)
9
2.71
(43.0)
1.07
(17.0)
5.36
(85.0)
2.02
(32.0)
10 - 1/4
3.47
(55.0)
1.39
(22.0)
6.94
(110.0)
2.59
(41.0)
10 - 1/4
Extra
4.73
(75.0)
1.89
(30.0)
9.46
(150.0)
3.53
(56.0)
11 -1/2
4.73
(75.0)
1.89
(30.0)
9.46
(150.0)
3.53
(56.0)
13
7.13
(113.0)
2.84
(45.0)
14.20
(225.0)
5.30
(84.0)
*Non-standard option
Summary of Contents for GIW MDX
Page 53: ...MDX en US 53 14 Notes...
