BULLETIN 640
APCO SILENT CHECK VALVES
JULY 2011
Series 600
Globe Style
Sizes 3" Through 42"
Series 300
Wafer Style
Size 1" Through 10"
Water Hammer
Hydraulics engineers are concerned in increasing numbers with the problem of water hammer. At best it
is a noise nuisance while in its most virulent form it can tear the finest pumping system apart.
What Causes Water Hammer?
The conditions responsible for this phenomenon are
well known; they occur when a quantity of energy
is suddenly released in a confined space. Energy is
a function of mass times velocity and relating this
to practical hydraulics engineering means that water
hammer occurs when a body of water in motion in a
pipe is suddenly stopped.
One of the circumstances under which this
phenomenon most commonly occurs is when
a pump is shut down and the forward flow of
water reverses under the influence of gravity and
commence to run the opposite way until stopped by
a check valve.
Recognizing this, it becomes obvious that one secret
to preventing water hammer due to flow reversal in
a system is to provide a check valve which will close
before this reversal of flow can take place. APCO
Silent Check Valves perform excellently in these
applications.
The following briefly outlines the characteristics of
various types of check valves:
Swing Checks
The common Swing Check Valve is so designed that
it often sees the reversal of flow before closing. This
means that the body of water is already in motion
and has to be stopped abruptly as the Swing Check
Valve closes.
to achieve perfection in one characteristic in a
design at the expense or compromise with other
characteristics. We feel that we would be remiss
if we did not draw the engineer’s attention to the
compromise that has been made in perfecting
the silent virtues of the Silent Check Valve and
elaborate to some extent on the significance of
this compromise.
This compromise is higher head loss than swing
check type valves. The graph on the next page
shows the relative head losses for three popular
types of check valves. It can be clearly seen that
Silent Check Valves do not suffer badly in comparison,
especially when it is recognized that slightly higher
head loss in the Silent Check Valves means a little
more electrical power is used during pumping
operation. When comparison is made with prevailing
rates for commercial power, this head loss may
become an academic rather than a practical concern.
These facts show why more engineers are
specifying APCO Silent Check Valves for their
customers’ protection.
Typical Silent Check Valve Installation
on Vertical Turbine Pumps
Silent Check Valves
It was to meet this steadily growing problem that
the Silent Check Valve evolved. In designing this
valve all other characteristics were subordinated to
the principal need that it must positively close before
a reversal of flow takes place, silently.
The Silent Check Valve was designed to open at
approximately
that when a pump is shut down, a Silent Check
Valve will completely close while there is still
positive head on the inlet side of approximately
1
/2 psi (3 kpa).
In this simple manner reverse flow, which is a major
cause of water hammer, never gets a chance to start
(in contrast to the swing check).
Experienced engineers know that it is only possible
© 2011 DeZURIK, Inc.
2
1
/4 to 1/2 psi (2 - 3 kpa), which means
Los Angeles County Sanitary District
Los Coyotes Plant 2-16" (400mm) 125# Class Silent Check Valves
Factory Mutual System Approved
ISO flanges available
Wide variety of materials and pressure classes
Specifying Silent Check Valves
Installing Silent Check Valves on
Discharge Side of the Pump Stops
Reverse Flow and Water Hammer
Before it Starts
Water hammer can be both destructive and
annoying. It is caused when a pump is shut down
and the forward flow of water is allowed to reverse
and is suddenly stopped by the check valve.
By positioning a Silent Check Valve on the discharge
side of the pump, the reverse flow (which is one
cause of water hammer) never has a chance to
start. This is because APCO Silent Check Valves are
designed to open at approximately
(2 - 3 kpa) and to completely close before the flow
can reverse itself.
Short face-to-face dimensions of APCO Silent Check
Valves also contribute to compactness in equipment
room piping.
1
/4 to 1/2 psi
Water
Hammer
Eliminated
Typical Silent Check Valve Installation
Note: APCO Silent Check Valves can be installed
in any position.
Temp
ºF
ºC
0-150
-18-66
-20-100
-29-38
-20-150
-29-66
200
93
250
121
300
149
Seat Test
PSI
kPa
Shell Test
PSI
kPa
Check Valves
Comparison Head
Loss Curves
Maximum Non-Shock Service Pressure, PSI/kPa
Ductile
Cast Iron ASTM A126 GR.B
Iron
ASTM
A536
Class 125# Class 250#
1-12"
14-24""
25-300
350-600
— — — — — — — —
— — — — — —
200
1379
190
1310
175
1207
165
1138
200
1379
300
2068
30" ≥
750 ≥
150
150
1034
1034
135
115
931
793
125
86285586
110
75850345
150
150
1034
1034
230
230
1586
1586
1-12"
25-300
500
3447
460
3172
415
2861
375
2586
500
3447
750
5171
14-24""
350-600
300
2068
280
1931
260
1793
240
1655
300
2068
450
3103
30"
750 ≥
2068
1724
1379
1034
2068
3103
Pressure
Class
≥
150 300 150 300 150 300 400 600 150 300 400 600
250
1724
300
242
1669
250
235
1620
200
235
1620
150
215
1482
300
275
1896
450
400
2758
640
4413
620
4275
600
4137
582
4013
565
3896
720
4964
975
6722
Head Loss Increase
Bronze
ASTM B62
Pressure
Class
225
500
1551
3447
— —
— —
210
465
1448
3206
195
425
1344
2930
180
390
1241
2689
300
1000
2068
6895
450
1500
3103
10342
Silent
Check
Swing
Check
Slanting
Disc
Velocity Increase
Carbon Steel
ASTM A216 GR WCB
Pressure Class Pressure Class
— — — — — — — —
285
740
990
1965
272
1875
260
1793
245
1689
230
1586
315
2172
450
3103
5102
707
4875
675
4654
665
4585
655
4516
815
5619
1125
7757
6826
945
6516
900
6205
887
6116
875
6033
1090
7515
1500
10342
1480
10204
1415
9756
1350
9308
1332
9184
1315
9067
1630
11238
2225
15341
Stainless Steel
ASTM A351 CF 8M
275
720
4964
670
4619
620
4275
590
4068
560
3861
795
5481
1100
7584
960
6619
892
6150
825
5688
785
5412
745
5137
1060
7308
1450
9997
1896
257
1772
240
1655
227
1565
215
1482
305
2103
425
2930
1440
9928
1340
9239
1240
8549
1180
8136
1120
7722
1585
10928
2175
14996
FºCºPSI
kPa
Inch
Millimeter
3
Wafer Style Series 300
125 lb.Class
150 lb.Class
Bolt Circle
250 lb. Class
300 lb. Class
Bolt Circle
Full Flow Area Approximately 3% Greater Than Pipe Size
Standard Construction
Ductile Iron Body
Stainless Steel Trim
Stainless Steel Spring
Optional Construction
Stainless Steel
Use Only Flat Face
Flange and Full Face
Gasket
Cast Steel Body with Bronze or
Stainless Steel Trim
Resilient Seating (Buna-N)
See Figure 1 (Optional)
Note: ID of mating flange (seat side only) should never
be greater than seat ring OD.
Model Size
1" 252.063"
301
1.25" 302.063"
301.25
1.5" 402.375"
301.5
2" 502.625"
302
2.5" 652.875"
302.5
3" 803.125"
303
305
358
360
100
125
150
200
10"
250
200
10"
250
4"
5"
6"
8"
8"
304*
306*
308*
310*
Dimensions for 125#/250# Class Valves
Face
to
Face
52
52
60
67
73
79
4"
102
4.625"
117
5.5"
140
6.5"
165
8.25"
210
6.5"
165
8.25"
210
No. of
Bolts
Bolt Circle Bolt Size
125# 250# 125# 250# 125# 250#
4 4
4 4
4 4
4 8
4 8
4 8
8 8
8 8
8 12
3.125" 793.5" 89.5" x 4.25"
3.5" 893.875" 98.5" x 4.25"
3.875" 984.5"
4.75"
121
5.5"
5.875"
140
6"
6.625"
152
7.5"
7.875"
191
8.5"
9.25"
216
9.5"
10.625"
241
114
5"
127
149
168
200
235
270
13 x 108
.5" x 4.75"
13 x 121
.625" x 5.25"
16 x 133
.625" x 5.75"
16 x 146
.625" x 6.25"
16 x 159
.625" x 7"
16 x 178
.75" x 7.75"
19 x 197
.75" x 8.75"
19 x 222
125 lb. ANSI Pressure Class
8 —
12 —
11.75"
298
14.25"
362
—
—
.75" x 10"
19 x 254
.875" x 12.5"
22 x 318
250 lb. ANSI Pressure Class
— 12 —
— 16 —
13"
330
15.25"
387
13 x108
—
—
Seat
Ring
OD
.625" x 4.5"
16 x 114
.625" x 4.5"
16 x 114
.75" x 5.25"
19 x 133
.625" x 5.5"
16 x 140
.75" x 6.5"
19 x 165
.75" x 7"
19 x 179
.75" x 8"
19 x 203
.75" x 9"
19 x 229
.75" x 10"
19 x 254
—
—
.875" x 11.25"
22 x 286
1" x 13.75"
25 x 349
Mating
Flange
ID
Resilient
Seat Detail
Figure 1
optional for both
Wafer or Globe
Styles
Inch
Millimeter
Operating pressure to 1500 lb. class is available.
Please contact factory for higher pressure classes.
4
Pressure joint is effected after installation.
Applies to both wafer and globe styles.
Screw retains seat during handling and shipping.
Globe Style Series 600
Full Flow Area Approximately 10% Greater Than Pipe Size
Standard Construction
Ductile Iron Body
Stainless Steel Trim thru 24" (600mm)
Stainless Steel Spring
*Max.
Mating
Flange
ID
Seat
Ring
OD
Use Only
Flat Face
Flange
and
Full Face
Gasket
Model Size
603
604*
605*
606*
608*
610*
612*
614
616
618*
620
624
630
636
642
3"
80
4"
100
5"
125
6"
150
8"
200
10"
250
12"
300
14"
350
16"
400
18"
450
20"
500
24"
600
30"
750
36"
900
42"
1100
Resilient
Seat Detail
125# & 150# ANSI Pressure Casses
Flange
Dia.
7.5"
191
9"
229
10"
254
11"
279
13.5"
343
16"
406
19"
483
21"
533
23.5"
597
25"
635
27.5"
699
32"
813
38.75"
984
46"
1168
53"
1346
Face
Face
7.25"
10.125"
14.25"
15.75"
17.625"
18.75"
20.625"
29.25"
to
6"
152
184
8.5"
216
9"
229
257
12"
305
362
400
448
476
524
24"
610
743
45"
1143
50"
1270
Bolt
Circle
Dia.
6"
152
7.5"
191
8.5"
216
9.5"
241
11.75"
298
14.25"
362
17"
432
18.75"
476
21.25"
540
22.75"
578
25"
635
29.5"
749
36"
914
42.75"
1086
49.5"
1257
Bolt
Size
.625"
16
.625"
16
.75"
19
.75"
19
.75"
19
.875"
22
.875"
22
1"
25
1"
25
1.125"
29
1.125"
29
1.25"
32
1.25"
32
1.5"
38
1.5"
38
No. of
Bolts
4
8
8
8
8
12
12
12
16
16
20
20
28
32
36
*Max
Mating
Flange
ID
3.375"
86
4.75"
121
5.5"
140
6.5"
165
8.5"
216
10.75"
273
12.875"
327
14.75"
375
16.5"
419
18.75"
476
20.625"
524
24.75"
629
29.5"
749
36"
914
42"
1067
Optional Construction
Stainless Steel
Cast Steel Body with Bronze or
Stainless Steel Trim
Duplex Stainless Steel
Resilient Seating (Buna-N)
Compression molded (not glued or chemically
bonded) onto the seat allowing metal to metal
contact with drop tight resilient shut-off
Note: If special mating flanges are used, ID of mating flange
(seat side only) should never be greater than seat ring OD.
250# & 300# ANSI Pressure Casses
Model Size
653
654
655
656
658
660
662
664
666
668
670
674
680
686
692
3"
80
4"
100
5"
125
6"
150
8"
200
10"
250
12"
300
14"
350
16"
400
18"
450
20"
500
24"
600
30"
750
36"
900
42"
1100
Flange
Dia.
8.25"
210
10"
254
11"
279
12.5"
318
15"
381
17.5"
445
20.5"
521
23"
584
25.5"
648
28"
711
30.5"
775
36"
914
43"
1092
50"
1270
57"
1448
Face
Face
10.125"
14.25"
15.75"
17.625"
18.75"
20.625"
29.25"
to
6"
152
7.25"
184
8.5"
216
9"
229
257
12"
305
362
400
448
476
524
24"
610
743
45"
1143
50"
1270
Bolt
Circle
Dia.
6.625"
168
7.875"
200
9.25"
235
10.625"
270
13"
330
15.25"
387
17.75"
451
20.25"
514
22.5"
572
24.75"
629
27"
686
32"
813
39.25"
997
46"
1168
52.75"
1340
Bolt
Size
.75"
19
.75"
19
.75"
19
.75"
19
.875"
22
1"
25
1.125"
29
1.125"
29
1.25"
32
1.25"
32
1.25"
32
1.5"
38
1.75"
44
2.125"
54
2.25"
57
No. of
Bolts
8
8
8
12
12
16
16
20
20
24
24
24
28
32
36
*Max
Mating
Flange
ID
3.375"
86
4.75"
121
5.5"
140
6.5"
165
8.5"
216
10.75"
273
12.875"
327
14.75"
375
16.5"
419
18.75"
476
20.625"
524
24.75"
629
29.5"
749
36"
914
42"
1067
Inch
Millimeter
Inch
Millimeter
Operating pressure to 1500 lb. class is available. Please contact factory for higher pressure classes.
5
What Makes the APCO Silent Check Valve
So Outstanding?
Performance Guarantee
The graph below shows the comparative head loss through different manufacturers’ Silent Check Valves. The
figures used to construct this graph were obtained from certified independent laboratory tests for the APCO
valves and compared against other available published data.
The lower losses of APCO Silent Check Valve as indicated by this graph frequently gives rise to the question
“How does APCO manage to keep its losses below those of the other valves examined?”
Superior performance is never accidental and this question is best answered by the following details.
First, every APCO valve is designed with the initial premise that the minimum cross-sectional area shall exceed
that of the pipe it serves. In every APCO valve the full cross-sectional area of the most critical points, is greater
than the cross-sectional area of the pipe. This is clearly illustrated on the valve drawing of a 5" APCO Silent
Check Valve on the adjacent page.
Secondly, APCO has designed many types of valves for hydraulic service for over sixty years and our
engineers are especially conscious of the importance of good hydraulic flow lines. Again, an examination of the
drawing on the next page will show how very carefully the contours have been worked out to give the best
possible hydraulic flow results.
Even small details such as streamlining the spokes have been given due consideration. This devotion to design
detail makes it readily obvious why the APCO Silent Check Valve can reasonably be expected to have the most
favorable flow characteristics of any Silent Check Valve.
Pressure Loss Curve Comparison Between Apco Silent Check Valves and Other
Similar Makes (Actual Tests Shown for a Particular Size)
Construction
The superior performance characteristics of the
APCO Silent Check Valve are matched by its equally
superior quality of construction as the following
design details will show.
The seat is held by stainless steel screws so that it
can be taken apart after years of service as easily as
the day it was made.
Electrolytic action is eliminated by having the shaft
of the plug ride in bushings made of the same
material as the shaft itself.
A simple loose guide bushing for the shaft is
provided and made of the same material as the
shaft. This bushing is held in place by the spring so
that in the event it is considered necessary to take
the valve apart in the field, the bushings can be
easily removed by hand.
Range of Most Common
Operating Velocity Flows
Pressure Loss
(In Feet Of Water)
Velocity in Pipe (F.P.S.)
Valve
C
Valve
W
Valve
M
APCO
Valve
4
3
(In P.S.I.)
2
1
Pressure Loss
6
APCO Silent Check Valves have been thoroughly tested by Factory Mutual Research
Corp. As a result, the 300 Series and 600 Series Valves can be used on hazardous fire
fighting equipment and fire protection systems with assurance of performance. For
such applications, insist on the Factory Mutual Guarantee Label of Approval on your
Silent Check Valve. Available on sizes as indicated.
Materials of Construction
All the materials used in APCO valves are clearly referred to by their appropriate ASTM numbers.
APCO offers ductile iron as a standard on sizes thru 24" (600mm).
A brief technical explanation of the qualities is given below.
The Advantages of Ductile Iron
Ductile iron, contrary to its name, is not really a cast iron at all but an alloy developed by the International
Nickel Company.
Cast iron has graphite present in lenticular flakes which causes it to be brittle and have a relatively
low tensile strength.
The graphite in ductile iron is present in spheroidal shape making it ductile with a much higher
tensile strength.
Various types of ductile iron are available and we use the one especially recommended for valves. This is
Type 65-45-12 ductile iron ASTM A536 strength of 65 to 80,000 psi and a yield strength of 45 to 60,000 psi,
equivalent to carbon steels, yet retaining the anti-corrosion properties of iron.
5" (127mm) APCO Series 600 Silent Check Valve with Minimum
10% Greater Flow Area.
All APCO Silent Check Valves
100% hydrostatically
tested to ANSI standards
Flow area of
valve at cross
section lines
shown below
E
27.1 Sq. in.
D
C
27.2 Sq. in.
B
22.1 Sq. in.
Stroke
A
23.1 Sq. in.
Compare flow area of pipe below with those shown at different sections of the valve.
Area of 5" pipe = 20.1 sq. in.
Stainless Steel Ball & Seat Retaining Screws
Bronze bushing
protects against
electrolytic action
Smooth flow
body contour
guarantees
minimum loss
Stainless
steel spring
(Also available
In monel
for critical
water condition)
7
Specifications
Head Loss Characteristics For
10
9
8
7
6
5
4
3
2
1
.9
.8
.7
.6
.5
Head Loss In Feet
.4
.3
.2
.1
2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 100
Silent Check Valves Series 300 (Check Style)
1" 11⁄4" 11⁄2" 2" 21⁄2" 3" 4" 5" 6" 8"
Flow In Gallons Per Minute
2 3 4 5 6 7 8 9 1,000 2 3 4 5 6 7 8 9 10,000
At Left: Typical Silent Check Valve
application on vertical turbine
pumps (30"). Utah Valley Water
Treatment Plant, Orem, Utah.
Head Loss Characteristics For
100,000
Silent Check Valves Series 600 (Globe Style)
9
8
7
6
50,000
4
3
2
10,000
9
8
7
6
5,000
4
3
2
1,000
9
8
7
Flow In Gallons Per Minute
6
500
4
3
2
100
.1 .2 .3 .4 .5 .6 .7 .8 .9 1 2 3 4 5 6 7 8 9 10
42"
36"
30"
24"
20"
18"
16"
14"
12"
10"
8"
6"
5"
4"
3"
Head Loss In Feet
100,000
9
8
7
6
50,000
4
3
2
10,000
9
8
7
6
5,000
4
3
2
1,000
9
8
7
6
500
4
3
2
Series 300 Wafer Style Silent Check Valve
Wafer Style Silent Check Valves shall be designed with ductile iron bodies, and stainless steel seat, plug and spring.
The valve plug must be center guided at both ends with a through integral shaft and spring loaded for guaranteed
silent shut-off operation.
The spring must be helical or conical. Seat and plug shall be hand replaceable in the field for ease of maintenance.
The flow area through the body shall be equal to or greater than the cross-section area of the equivalent pipe size.
All materials of construction shall be certified in writing to conform to ASTM specifications as follows:
Body Ductile Iron ASTM A536 65-45-12
Plug & Seat Stainless Steel ASTM A276 T304
Spring Stainless Steel ASTM A276 T316
Exterior Paint Universal Metal Primer FDA approved for potable water contact
Valve to be APCO Series 300 - 1"-10" (25-250mm) Silent Check Valve - Wafer Style, Factory Mutual Approved - sizes
4" (100mm), 6" (150mm), 8" (200mm) and 10" (250mm) (125 Lb. Class), sizes 4" (100mm), 6" (150mm), (250 Lb. Class).
Series 600 Globe Style Silent Check Valve
Globe Style Silent Check Valve shall be designed with ductile iron bodies, and stainless steel seat, plug and spring.
The valve plug must be center guided at both ends with a through integral shaft.
The spring must be helical or conical. The seat and plug shall be hand replaceable in the field for ease of maintenance.
The flow area through the body shall be equal to or greater than the cross-sectional are of the equivalent pipe size.
All materials of construction shall be certified in writing to conform to ASTM specifications as follows:
Body Ductile Iron ASTM A536 65-45-12
Plug & Seat Stainless Steel ASTM A276 T304
Spring Stainless Steel ASTM A276 T316
Exterior Paint Universal Metal Primer FDA approved for potable water contact
Valve to be APCO Series 600 - 3"-42" (80-1100mm) Silent Check Valves - Factory Mutual Approved - sizes 4" (100mm),
6" (150mm), 8" (200mm) and 10" (250mm), 12" (300mm) and 18" (450mm).
Sales and Service
For information about our worldwide locations, approvals, certifications and local representative:
Web Site: www.dezurik.com E-Mail: info@dezurik.com
250 Riverside Ave. N. Sartell, Minnesota 56377 • Phone: 320-259-2000 • Fax: 320-259-2227
Design features, materials of construction and dimensional data, as described in this bulletin, are provided for your information only
DeZURIK, Inc. reserves the right to incorporate our latest design and material changes without notice or obligation.
and should not be relied upon unless confirmed in writing by DeZURIK, Inc. Certified drawings are available upon request.
Printed in the U.S.A.
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