J E Klein

M D Fowley

T J Steeper

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Contract No. and Disclaimer:
This manuscript has been authored by Savannah River Nuclear 
Solutions, LLC under Contract No. DE-AC09-08SR22470 with the U.S. 
Department of Energy. The United States Government retains and the 
publisher, by accepting this article for publication, acknowledges that 
the United States Government retains a non-exclusive, paid-up, 
irrevocable, worldwide license to publish or reproduce the published 
form of this work, or allow others to do so, for United States 
Government purposes.
A NORMETEX MODEL 15 m3/Hr WATER VAPOR PUMPING TEST 
 
 
 
 
M. D. Fowley, T. J. Steeper, and J. E. Klein 
 
Savannah River National Laboratory: Aiken, SC 29808, james.klein@srnl.doe.gov 
 
 
 
 
Tests were performed using a Model 15 m3/hr Normetex 
vacuum pump to determine if pump performance 
degraded after pumping a humid gas stream.  An air feed 
stream containing 30% water vapor was introduced into 
the pump for 365 hours with the outlet pressure of the 
pump near the condensation conditions of the water.  
Performance of the pump was tested before and after the 
water vapor pumping test and indicated no loss in 
performance of the pump.  The pump also appeared to 
tolerate small amounts of condensed water of short 
duration without increased noise, vibration, or other 
adverse indications.  The Normetex pump was backed by 
a dual-head diaphragm pump which was affected by the 
condensation of water and produced some drift in 
operating conditions during the test.  
 
 
I. INTRODUCTION 
 
For tritium processing and many other industrial 
applications, dry, oil free vacuum pumps are used which 
do not introduce contaminants into the process and do not 
produce waste oil which requires proper disposal.  Some 
roots style vacuum pumps claim to be oil-free, but the 
seals used between the pumping section and the oil 
reservoir eventually leak or fail resulting in pump oil 
contamination of the process gas. 
 
The Normetex brand pumps (Ref. 1) are used world-
wide in tritium process applications.  The most commonly 
used pump in tritium process applications is the Model 15 
pump which is advertised as having a pump speed of 15 
m3 per hour (9 cfm) when operated using 50 Hz electrical 
power.  The only materials exposed to the process gases 
are stainless steel or nickel plated steel. The pumps are 
made up of two overlapping scrolls, machined to tight 
tolerances (50 m) to produce small operational 
clearances when pumping gases. 
 
In some tritium process operations, it is necessary to 
pump gases containing water vapor.  Various 
manufactures of dry scroll pumps utilize a ballast port 
between various stages of compression to prevent water 
condensation in the pump (e.g. BOC Edwards Models 
ESDP12 and GVSP30, and Varian model PTS 300 and 
PTS 600 pumps).   
 
Condensation of water between the bellows of a 
metal bellows style pump is known to quickly cause a 
leak in a pump bellow.  It was unknown if pumping gases 
with water vapor with a Normetex pump would cause 
condensation in the pump and damage the performance of 
the pump.  The purpose of this paper is to describe a test 
to examine the effects of pumping a ‘wet” gas stream with 
a Normetex pump and if it altered the pumping 
performance of a Normetex 15 m3/hr pump. 
 
 
II. BACKGROUND 
 
Figure 1 shows the pump speed curve for the 
Normetex 15 pump reproduced from vendor literature.  
The pump speed peaks at approximately 12 m3/hr (3.3 
liters/sec) at an inlet pressure of approximately 400 Pa (3 
torr).  The vendor states the pump curve was created 
using air with the scroll pump backed by an elastomer 
diaphragm backing pump.   
 
It was decided for the test to feed 30 volume percent 
water in air into the pump near the peak of the Normetex 
pump curve.  Typically a metal bellows MB-601 (Ref. 2) 
pump with the two pump heads connected in series is 
used to back the Normetex pump.  Due to concerns of 
failing the metal bellows pump from water vapor 
condensation a bellows, an alternate backing pump was 
selected (described in the next section).   
 
To determine the exhaust pressure of the Normetex 
pump for the test, the properties of saturated water vapor 
were examined.  At 30 percent water vapor, condensation 
will occur around 34.0 kPa (255 torr) if the water 
temperature is less than approximately 47°C.  It was 
thought the internals of the Normetex pump would be 
hotter than 47°C and testing with an exhaust pressure near 
34 kPa would be near the condensation conditions for the 
water.  A long-term test duration of 2 weeks (336 hours) 
was chosen to demonstrate the durability of the pump. 
0
2
4
6
8
10
12
14
1.E-2 1.E+0 1.E+2 1.E+4 1.E+6
Inlet Pressure (Pa)
P
u
m
p
 S
p
ee
d
 (
m
3 /
h
r)
 
 
Fig. 1. Normetex 15 Pump Speed Curve (Reproduced 
From Vendor Literature) 
 
 
III. EXPERIMENTAL 
 
A schematic of the experimental system is shown in 
Figure 2.  A compressed air supply was dried, reduced in 
pressure, and fed to the test inlet system.  The air inlet 
system could supply air to rotameters to feed the pump 
during the test and some air could also bypass the pump 
to adjust the pressure at the exhaust of the pump.  The air 
inlet system could also fill a vacuum vessel used for 
pump-down tests (PDTs) to ascertain the Normetex pump 
performance before and after the water pumping test 
 
The Normetex pump was backed by a Laboport 
Model N820.3FTP two-stage diaphragm pump with was 
also used to rough down the system. This pump had an 
ultimate pressure of 800 Pa (6 torr).  The line between the 
outlet of the Normetex pump and the backing pump was 
heat-traced to prevent condensation. 
 
The water for the test was contained in a vessel with 
a heater and was placed on a scale.  Water was introduced 
into the inlet of the pump by varying the opening of the 
valve connecting the water container to the manifold.  The 
water flow rate was determined by the mass change with 
time of the water container. 
 
Two tests were used to benchmark the performance 
of the Normetex pump.  PDTs were transient tests where 
the vacuum chamber was filled with air to roughly 12 kPa 
(90 torr) and the rate of pressure decrease calculated to 
determine pump speed/performance.  Steady-state flow-
through tests (FTTs) were also used to determine pump 
performance.  Various inlet pressures of air were fed to 
pumping system and the flow rate of air measured.  
Benchmark pump performance test data were collected 
before the introduction of water.  Comparison of these 
results to post water vapor test results were used to 
determine if the pumping performance of the Normetex 
pump had been altered. 
 
For the water vapor pumping tests, the inlet pressure 
to the pump was adjusted to give an inlet pressure of 0.4 
kPa (3 torr), the water vapor flow controlled by adjusting 
the valve opening to the connection tee at the inlet of the 
pump, and the outlet pressure controlled by supplying air 
to the back side of the pump via a bypass line.  Valve 
positions were adjusted to maintain test conditions.  The 
water feed rate was determined by the mass change of the 
water container with time.  At the end of the test, the 
water supply was stopped for 30 minutes to dry out the 
system before the benchmark performance tests.   
 
 
Regulator
Heater
Water
Container
Heater
Balance
Cable
Heater
Drier
R
o
to
m
et
er
Air
V
a
c
u
u
m
 C
h
a
m
b
e
r
Normetex
Pump
Diaphragm
Pump
 
 
Fig. 2. Experimental Test System Schematic 
 
 
IV. RESULTS 
 
Five attempts were made before a successful long-
term run could be completed.  For the first attempt, the 
water vapor flow rate was unstable which was traced to 
the design of the water vapor inlet system.  Ice crystals 
formed at the control valve orifice.  Attempts to supply 
sufficient heat to the control valve to prevent ice 
formation were unsuccessful due to the temperature limit 
of materials in the valve surrounding the orifice.  The 
total run time was 120 hours with the run not at the 
desired test conditions of 30% water vapor in air, 0.4 kPa 
(3 torr) inlet pressure, and a 34 kPa (255 torr) outlet 
pressure.  Baseline pump tests were repeated after this 
attempt and no effect on pump performance was 
indicated. 
For the second attempt, the water inlet system was 
modified where water vaporization occurred in the water 
vessel and not in the control valve.  A cable heater in the 
container provided improved stability of the water supply 
rate.  After establishing the inlet conditions of flow rate 
and pressure, the outlet condition (pressure) was set 
which produced unstable operation: the inlet and outlet 
pressures fluctuated.   
 
For the third attempt, the inlet conditions of 30% 
water vapor in air at 0.4 kPa (3 torr) inlet pressure were 
tried with a lower outlet pressure of 26.7 kPa (200 torr).  
For this test, the inlet pressure and outlet pressures were 
first set and then the water flow initiated.  Flow 
instabilities were encountered as the water flow rate 
approached the desired test condition.  The flow 
instability was attributed to significant room temperature 
variations where the tests were conducted due to the 
winter season and the constant opening and closing of 
building doors during the test.  Condensation occurred in 
the water inlet line and then formed ice as it flashed into 
vapor.   
 
The fourth attempt was similar to the third attempt 
after the test system was moved to a location with better 
ambient temperature control.  A heat source was also 
added to the pump inlet line.  Even without condensation 
in the pump inlet line, flow instabilities occurred.   
 
A parametric study where the different parameters 
were varied from desired test conditions found 
instabilities occurred when the pump outlet pressure 
exceeded 18.7 kPa (140 torr) or the water vapor content 
exceeded 20%, but no instabilities were observed when 
the pump outlet heat tracing temperature ranged from 
20°C to 50°C.  Examination of water vapor pressure data 
found a temperature of 35°C produced saturated vapor for 
30% water vapor at 18.7 kPa (140 torr) and also produced 
saturated vapor for 20% water vapor at 26.7 kPa (200 
torr).  A thermocouple attached to the Normetex pump 
housing measured a temperature of 31°C – slightly lower 
than the 35°C inferred from the test results. 
 
Based on the results from the fourth run, the fifth run 
was made assuming the internal Normetex pump 
temperature was 35°C.  The outlet pressure for the test 
was selected as 18.0 kPa (135 torr), slightly below the 
previous instability pressure of 18.7 kPa (140 torr).  The 
water vapor flow was started after the inlet and outlet 
conditions were set and took approximately three hours to 
get near the desired water flow rate.  Several additional 
hours were needed to obtain the desired water flow rate. 
 
The inlet pressures during the test are shown in 
Figure 3 and varied mostly between 387 and 413 Pa (2.9 
and 3.1 torr).  The inlet pressure required little adjustment 
during the test and was usually done by adjusting the air 
inlet flow rate.  The pump outlet pressures during the test 
are shown in Figure 5. 
 
 
360
380
400
420
440
460
480
500
520
0 50 100 150 200 250 300 350 400
Time (Hours)
In
le
t 
P
re
ss
ur
e 
(P
a)
 
 
Fig. 3. Normetex Pump Inlet Pressure 
 
 
15
16
17
18
19
20
21
22
23
24
25
0 50 100 150 200 250 300 350 400
Time (Hours)
O
u
tl
et
 P
re
ss
u
re
 (
k
P
a)
 
 
Fig. 4. Normetex Pump Outlet Pressure 
 
 
V. DISCUSSION 
 
The instabilities in the test inlet and outlet pressures 
were attributed to variations in room temperature.  Figure 
5 shows the room temperatures during the test.  Around 
88 to 95 hours into the test, the inlet pressure experienced 
its largest fluctuation.  Figure 5 shows that preceding and 
during part of this time, the room temperature was 
decreasing to almost 22°C and likely causing 
condensation somewhere in the system producing the 
inlet pressure fluctuations.  As the room temperature 
returned to it previous, higher values, the inlet pressure 
returned to its stable pressure range. 
 
The outlet pressure spikes seen in Figure 4 are real 
and are only shown as a single point due to the sampling 
frequency of the data collection system.  Periodic peaks 
lasting on the order of two minutes could be seen on the 
data collection system display screen.  These higher 
discharge pressures were attributed to the way 
condensation was cleared from the roughing pump, but 
did not impact pump inlet pressures.  Water would collect 
in the area around the roughing pump and would 
periodically leave the system as a “slug” of water.  Once 
the water would clear the system, as indicated by its 
presence in a catch pan, water would slowly accumulate 
again and the cycle would be repeated.  Performance and 
benchmark tests were repeated and no measurable 
difference in pump performance could be determined. 
 
 
20
22
24
26
28
30
32
0 50 100 150 200 250 300 350 400
Time (Hours)
R
oo
m
 T
em
p
er
at
u
re
 (
°C
)
 
 
Fig. 5. Room Temperature During Test  
 
 
VI. CONCLUSIONS 
 
A Normetex Model 15 pump is able to pump water vapor 
in air for over 370 hours as long as temperatures within 
the system do not produce condensed water.  The 
apparent temperature of the Normetex pump for these 
tests was 35°C even though the pump casing temperature 
was lower and the exhaust piping temperature higher.  
Even with some condensation in the Normetex pump 
during unsuccessful pump test trials, the Normetex pump 
was still functional and its performance not altered during 
these tests.  Water condensation in the backing pump will 
occur if the water vapor exiting the Normetex pump is 
near saturation conditions and will likely be the source of 
pressure fluctuations in the system. 
 
 
ACKNOWLEDGMENTS 
 
The authors would like to thank Mike Armstrong, Vernon 
Bush, D. Andy Foreman, and Mike Restivo for their 
support of this work.  This manuscript has been authored 
by Savannah River Nuclear Solutions, LLC under 
contract No. DEAC09-08SR22470 with the U.S. 
Department of Energy.  The publisher, by accepting this 
article for publication, acknowledges that the United 
States Government retains a non-exclusive, paid-up, 
irrevocable, worldwide license to publish or reproduce the 
published form of this work, or allow others to do so, for 
United States Government purposes.   
 
 
REFERENCES 
 
1. Normetex Pompes, 13, Rue De La Brasserie, 27500 
Pont Audemer, France 
2.  Senior Aerospace Metal Bellows, 1075 Providence 
Highway, Sharon, MA 02067, U.S.A. 


A NORMETEX MODEL 15 m 3 /Hr WATER VAPOR PUMPING TEST

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A NORMETEX MODEL 15 m 3 /Hr WATER VAPOR PUMPING TEST

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