UNIREX Pump - Manual (Page 23)

MARK 3 USER INSTRUCTIONS ENGLISH 71569102 08-06
Page 23 of 68 flowserve.com
Figure 4-9 illustrates the ideal piping configuration with a
minimum of 10 pipe diameters between the source and
the pump suction. In most cases, horizontal reducers
should be eccentric and mounted with the flat side up as
shown in figure 4-10 with a maximum of one pipe size
reduction. Never mount eccentric reducers with the flat
side down. Horizontally mounted concentric reducers
should not be used if there is any possibility of entrained
air in the process fluid. Vertically mounted concentric
reducers are acceptable. In applications where the fluid
is completely de-aerated and free of any vapor or
suspended solids, concentric reducers are preferable to
eccentric reducers.
Figure 4-9 Figure 4-10
Avoid the use of throttling valves and strainers in the
suction line. Start up strainers must be removed shortly
before start up. When the pump is installed below the
source of supply, a valve should be installed in the
suction line to isolate the pump and permit pump
inspection and maintenance. However, never place a
valve directly on the suction nozzle of the pump.
Refer to the Durco Pump Engineering Manual and
the Centrifugal Pump IOM Section of the Hydraulic
Institute Standards for additional recommendations
on suction piping. (See section 10.)
Refer to section 3.4 for performance and operating
limits.
4.6.2.1 Mark 3 Self-Priming Pumps
The suction piping must be as short as possible and
be as close to the diameter of the suction nozzle as is
practical. The pump works by removing the air
contained in the suction piping. Once removed, it
operates exactly the same as a flooded suction
standard pump. Longer and larger the suction pipe
have a greater volume of air that has to be removed,
resulting in longer priming time. The suction piping
and seal chamber must be airtight to allow priming to
occur. When possible, it is recommended that
suction piping be sloped slightly towards the casing to
limit priming fluid loss down the suction line during
priming and shutdown.
4.6.3 Discharge piping
Install a valve in the discharge line. This valve is
required for regulating flow and/or to isolate the pump
for inspection and maintenance.
When fluid velocity in the pipe is high,
for example, 3 m/s (10 ft/sec) or higher, a rapidly
closing discharge valve can cause a damaging
pressure surge. A dampening arrangement should
be provided in the piping.
4.6.3.1 Mark 3 Self-Priming Pumps
During the priming cycle, air from the suction piping is
evacuated into the discharge piping. There must be
a way for this air to vent. If air is not able to freely
vent out the discharge pipe, it is typically
recommended to install an air bleed line. The air
bleed line is typically connected from the discharge
pipe to the sump. Car must be taken to prevent air
from re-entering suction pipe.
4.6.4 Allowable nozzle loads
Flowserve chemical process pumps meet or exceed
the allowable nozzle loads given by ANSI/HI 9.6.2.
The following paragraphs describe how to calculate
the allowable loads for each pump type and how to
determine if the applied loads are acceptable. The
first configuration covered is ASME B73.1M pumps,
including the Mark 3 Standard, Sealmatic, Lo-Flo,
Recessed Impeller, and Unitized Self-Priming pumps.
The second configuration covered is the ASME
B73.2M vertical, Mark 3 In-Line pump.
4.6.4.1 Mark 3 horizontal pumps (ASME B73.1M)
The following steps are based upon ANSI/HI 9.6.2.
All information necessary to complete the evaluation
is given below. For complete details please review
the standard.
a) Determine the appropriate casing “Material
Group No.” from figure 3-2.
b) Find the “Casing material correction factor” in
Figure 4-11 based upon the “Material Group No.”
and operating temperature. Interpolation may be
used to determine the correction factor for a
specific temperature.
c) Find the “Baseplate correction factor” in Figure
4-12. The correction factor depends upon how
the baseplate is to be installed.
d) Locate the pump model being evaluated in Figure
4-16 and multiply each load rating by the casing
correction factor. Record the ”adjusted Figure
4-16 loads”.
e) Locate the pump model being evaluated in
Figures 4-17 and 4-18 and multiply each load
rating by the baseplate correction factor. Record
the adjusted Figure 4-17 and 4-18 loads.