MIYAWAKI S31N User manual

THERMODYNAMIC STEAM TRAP
USER'S MANUAL

SAFETY GUIDE
The model S31N is a disc-type steam trap equipped with an automatic
blow-off mechanism.
In order to get maximum benefit from this product, be sure to read this
manual before installing it.
The following warnings and cautions are shown at appropriate
places in this manual.
WARNING
Failure to observe this type of precaution may
lead to serious injury or death.
CAUTION
Failure to follow this type of precaution can
lead to injury or damage to equipment and
property.
Table of Contents
1 SPECIFICATIONS AND MARKINGS 1
2 CONSTRUCTION DETAILS 2
3 INSTALLATION 3
4 OPERATION 4
5 MAINTENANCE 5
6 TROUBLESHOOTING 9
7 WARRANTY 10
8 SERIAL NUMBER (S. No.) DESIGNATION 11
9 GUIDANCE FOR READING SPECIAL PRODUCT
NAME 12

1
1 SPECIFICATIONS AND MARKINGS
WARNING
Be sure not to use this product at higher pressures than the specified maximum
allowable pressure (PMA) or at temperatures higher than the specified maximum
allowable temperature (TMA).
The following items are displayed on the name plate or the side of the product.
Check each item to avoid misuse of the product.
1) Maximum allowable pressure (PMA): 1.6 MPa (232 psig)
2) Maximum allowable temperature (TMA): 220 °C (428 °F)
3) Maximum Operating pressure (PMO): 1.6 MPa (232 psig)
4) Maximum operating temperature (TMO): 220 °C (428 °F)
5) Size: 15 mm (1/2”), 20 mm (3/4”), 25 mm (1”), 32 mm (1 1/4”), 40 mm (1 1/2”) and
50 mm (2”)
6) Year of production: The two leftmost digits in the four-digit or nine-digit “S. No.” on
the name plate are the last two digits of the year of production.
7) Flow direction: Shown by an arrow
8) Body material: ½” – 1” (15 – 25 mm) – Ductile cast iron FCD450
1 ¼” – 2” (32 – 50 mm) - Cast iron FC250
9) Model symbol: Showing the product model name
Some pictures and illustrations in this manual are examples of the model S31N. For
more details regarding dimensions and other specifications, please refer to the
catalog.
The models S31N and S31NF fully comply with the requirements of the European
Pressure Equipment Directive 2014/68/EU. They are classified according to Article 4,
Section 3 of the PED, which does not allow to bear the CE marking.

2
2 CONSTRUCTION DETAILS
15A, 20A, 25A
1. Body
2. Cover
3. Seat
4. Disc
5. Cap
6. Pin
7. Screen
8. Plug
10. Seat Gasket
11. Cap Gasket
13. Seat Gasket
14. Plug Gasket
37. Name Plate
38. Bimetal
39. Stopper Ring
32A, 40A, 50A
1. Body
2. Cover
3. Cap
4. Disc
5. Seat
6. Pin
7. Screen
8. Plug
10. Seat Gasket
11. Cap Gasket
12. Cover Bolt
13. Washer
14. Plug Gasket
15. Pipe
20. Bimetal
21. Stopper Ring
37. Name Plate
38. Rivet
(5)
(37)
(2)
(4)
(38)
(3)
(1)
(14)
(8)
(7)
(13)
(10)
(11)
(39)
(37)
(38)
(3)
(4)
(11)
(10)
(5)
(14)
(8)
(7)
(6)
(20)
(15)
(21)
(2)
(12)
(13)
(6)
(1)

3
3 INSTALLATION
WARNING
Pay very careful attention when working in hazardous environments. There is a risk
of explosion and the possibility of dangerous gases leaking. Always check whether
the pipeline contains flammable, high pressure or high temperature materials
before starting to work.
Make sure that isolation valves are installed on both the upstream and downstream
lines.
CAUTION
Before installing the product, open both isolation valves and the bypass valve, if
one exists, to blow out any debris or dirt inside the pipeline. After blowing out the
line, before starting to work, close the isolation valves and allow time for the
temperature to drop to a safe working temperature.
When installing the product, be sure to leave clearance for maintaining it.
1) Remove the dustproof seals covering both connections.
※Products shipped in plastic bags may not have dustproof seals.
2) Check the flow direction indicated on the side of the body.
3) The S31N can be used for both horizontal and vertical lines. However, when
installing a S31N in a horizontal line, be sure to maintain a slight slope to the line, so
that any condensate will flow smoothly.
4) Open the isolation valve on the upstream line and make sure the product works
normally.
Clearance for maintenance:
More than 80 mm
Clearance for maintenance
: More than 130 mm
Downstream line
Upstream
line Upstream
line
Downstream line
Flow direction is
indicated by an arrow.
Clearance for maintenance:
More than 50 mm
Clearance for maintenance: More
than 80 mm
Flow direction is
indicated by an
arrow.
15A, 20A, 25A 32A, 40A, 50A

4
4 OPERATION
CAUTION
Before starting operation, open the bypass valve or blow valve completely and blow
off the scale in the piping.
4.1 Operation procedure
1) After blowing off the scale from the piping, close the bypass valve or blow valve.
2) Open the stop valve on the trap outlet side.
3) Open the stop valve on the trap inlet side.
4.2 Stop procedure
1) Close the stop valve on the trap inlet side.
2) Close the stop valve on the trap outlet side.
* When stopping for a long time, completely drain the condensate from the piping and trap
and close the valves before and after the trap.

5
5 MAINTENANCE
WARNING
Before removing the trap from the pipe or disassembling it, be sure to close the
isolation valves. Then, release the residual pressure from the trap body (make
sure that the pressure in the main body is equal to the atmospheric pressure).
After it has fully cooled down (after the temperature of the main body has
reached ambient temperature), confirm for safe conditions and then begin work.
Even when the isolation valves are closed, there may be residual internal
pressure due to leaks from the isolation valves. Therefore, be very careful.
CAUTION
When replacing parts, make sure the replacement parts are supplied by
MIYAWAKI.
The performance of steam traps deteriorates gradually over time due to wear, corrosion
or dirt accumulating around the valve and the valve seat. Please conduct periodic
diagnosis of traps in order to keep steam control systems and equipment working well.
5.1 Tools for Diagnosing Steam Traps
Dr. Trap
Dr. Trap is a sophisticated steam trap management system for diagnosing steam traps
automatically by measuring the vibration and temperature of the steam trap. Survey
results are stored in the testing equipment and transferred to a steam trap analysis
software. The software aggregates and analyses steam trap survey data, identifying
faulty steam traps, providing steam loss and financial loss data, estimating CO2
emissions corresponding to leaking steam traps and providing many other analyze
possibilities to manage the steam trap population easily.
Dr. Trap Jr.
Dr. Trap Jr. is an inexpensive and easily to handle steam trap diagnostic system
consisting of an ultrasonic checker, temperature probe and a sophisticated analysis
software. The software allows to determine the condition of a steam trap, to estimate
steam and financial losses and the related CO2 emissions.
For more details, please, check our homepage:
https://www.miyawaki.net/en/products/steam-trap-management-system
or ask our local representative.

6
5.2 Repairs
When a trap fails, it is necessary to clean the internal parts and to replace damaged parts.
Take the failed trap apart following the steps below.
15A, 20A, 25A
5.2.1 Disassembling the trap
1) Remove the cover (2) by turning it clockwise until the ● mark on the side of the cover
is centered over the ● mark on the body (1). *Use a flat-blade screwdriver to remove
the cover.
2) Remove the cap (5) by turning it counterclockwise.
3) Remove the disc (4), stopper ring (39), and bimetal (38). Then remove the seat (3)
and pin (6).
5.2.2 Disassembling the screen
1) Turn the plug (8) counterclockwise to remove it. Remove also the plug gasket (14).
2) Remove the screen (7).
After cleaning the trap and replacing damaged parts, reassemble the parts in
reverse order as follows.
5.2.3 Reassembling the screen
1) Put the screen (7) and the plug gasket (14) back on the plug (8).
2) Then fasten the plug (8).
5.2.4 Reassembling the trap
1) Insert the pin (6) into the hole in the body (1).
2) Put the seat (3) back so that the pin (6) is inserted into the hole in the seat.
3) Put back the bimetal (38), stopper ring (39), and the disc (4) in that order.
*The groove of the disc should point to the seat of the trap.
4) Fasten the cap (5).
5) Put the cover (2) on the body (1) while aligning the ● mark on it with the gap in the
body and then turn it one quarter counterclockwise.
Torque table
Parts Tools Across the flats Torque
Cap (5) Torque wrench 41 mm (1.61”) 220 N∙m
Plug (8) Torque wrench 36 mm (1.41”) 80 N∙m

7
32A, 40A, 50A
5.2.5 Disassembling the trap
1) Remove the four cover bolts (12) and washers (13), and remove the cover (2).
2) Remove the cap (3), and take out the disc (4), stopper ring (21), bimetal (20), and cap
gasket (11).
3) Remove the seat (5). Then remove the seat gasket (10) and pin (6).
5.2.6 Disassembling the screen
1) Turn the plug (8) counterclockwise and remove it and the plug gasket (14).
2) Remove the screen (7).
After cleaning the trap and replacing damaged parts, reassemble the parts in
reverse order as follows.
5.2.7 Reassembling the screen
1) Put the screen (7) and plug gasket (14) back on the plug (8).
2) Fasten the plug (8) with the screen (7) to the body (1).
*Be sure to replace the plug gasket (14) with a new one.
5.2.8 Reassembling the trap
1) Insert the pin (6) into the hole in the body (1).
2) Put the seat gasket (10) back so that the pin (6) is inserted into the hole in the seat
gasket.
*Be sure to replace the seat gasket (10) with a new one. Replace the seat gasket
carefully, since it is easily folded.
3) Put the seat (5) back so that the pin (6) is inserted into the hole in the seat.
4) Put back the cap gasket (11), bimetal (20), stopper ring (21), and the disc (4) in that
order.
*Be sure to replace the cap gasket (11) with a new one. Replace the cap gasket
carefully, since it is easily folded.
5) Put the cap (3) on the seat (5).
6) Put on the cover (2) and fasten cover bolts (12) with the washers (13).
Torque table
Parts Tools Across the flats Torque
Cover Bolts (12) Torque wrench 24 mm (0.94”) 90 N∙m
Plug (7) Torque wrench 40 mm (1.57”) 120 N∙m

8
15A, 20A, 25A
1. Body
2. Cover
3. Seat
4. Disc
5. Cap
6. Pin
7. Screen
8. Plug
10. Seat Gasket
11. Cap Gasket
13.
Seat Gasket
14. Plug Gasket
37. Name Plate
38. Bimetal
39. Stopper Ring
32A, 40A, 50A
1. Body
2. Cover
3. Cap
4. Disc
5. Seat
6.
Pin
7. Screen
8. Plug
10. Seat Gasket
11. Cap Gasket
12. Cover Bolt
13. Washer
14. Plug Gasket
15. Pipe
20. Bimetal
21. Stopper Ring
37. Name Plate
38.
Rivet
(37)
(2)
(6)
(7)
(5) (11)
(13)
(12)
(37)
(38)
(2)
(1)
(6)
(14)
(4)
(39)
(38)
(3), (10), (13)
(1)
(8)
(3)
(11)
(4)
(21)
(20)
(5)
(10)
(15)
(7) (14)
(8)
15A, 20A, 25A 32A, 40A, 50A

9
6 TROUBLESHOOTING
Problem Possible cause Solution
Steam leaks or blows
through.
Dirt is stuck around the disc
(4) or the seat (3 for ½” – 1”; 5
for 1 ¼” – 2”).
Clean the disc (4) and the
seat (3 for ½” – 1”; 5 for 1 ¼”
– 2”).
Damage, wear or corrosion of
the disc (4) Replace the internal part.
Damage, wear or corrosion of
the seat (3 for ½” – 1”; 5 for 1
¼” – 2”).
Replace the internal parts.
The seat gasket (10 and 13
for ½” – 1”; 10 for 1 ¼” – 2”) is
damaged.
Replace the seat (3) and seat
gasket (10 and 13 for ½” – 1”).
Replace the seat gasket (10
for 1 ¼” – 2”).
The back pressure is too high.
(The back pressure must be
less than 50% of the inlet
pressure.)
Replace the trap with an
appropriate trap.
Steam leaks
from the
body.
From the cap
connection
The cap (5) is loose. (1/2”-1”) Tighten the cap (5). *1
The bolts (12) are loose. (1
¼”-2”) Tighten the bolts (12). *2
The cap gasket (11) is
damaged.
Replace the cap (5) and cap
gasket (11). (for 1/2”-1”)
Replace the cap gasket (11).
(for 1 ¼”-2”)
The seat gasket (13) is
damaged. (1/2”-1”)
Replace the seat (3) and seat
gasket (10 and 13).
The seat gasket (10) is
damaged. (1 ¼”-2”) Replace the seat gasket (10).
The sealing surface on the
body (1), seat (3 for ½” – 1”; 5
for 1 ¼” – 2”) or cap (5 for ½”
– 1”; 3 for 1 ¼” – 2”) is
damaged.
Replace the damaged part.
From the
plug
connection
The plug (8) is loose. Tighten the plug (8). *3
The plug gasket (14) is
damaged. Replace the plug gasket (14).
The sealing surface on the
body (1) or plug (8) is
damaged.
Replace the damaged part.
Insufficient condensate
discharged, or no
condensate discharged.
The screen (7) is clogged. Clean the screen (7).
Dirt has built up around the
seat (3 for ½” – 1”; 5 for 1 ¼”
– 2”).
Clean the seat (3 for ½” – 1”;
5 for 1 ¼” – 2”).
Dirt has built up in the fluid
path inside the body (1).
Clean the body (1).
The bimetal (38 for ½” – 1”; 20
for 1 ¼” – 2”) is damaged.
Replace the bimetal (38 for ½”
– 1”; 20 for 1 ¼” – 2”).
Insufficient condensate
capacity.
Replace the trap with a larger
capacity trap.
Wrong installation direction Reinstall the product in the
correct direction.
*1, *2 and *3: Refer to the torque tables in Section 5 “Maintenance” to retighten the parts with
the correct torque.

10
7 WARRANTY
7.1 Warranty period
The warranty period is 18 months after shipment or 12 months after installation, whichever
occurs first.
7.2 Details of the warranty
If the product stops working correctly within the warranty period, we will repair or replace
the product free of charge if the cause of the trouble is not one of the following items.
1) The precautions described in this manual were not observed.
2) User's errors or mistakes such as an inappropriate installation or incorrect handling,
or an excessively large impact caused by dropping
3) Problems caused by devices or equipment other than MIYAWAKI’s, or a disallowed
use environment
4) When a repair or modification has been performed by anyone other than MIYAWAKI
or people who are authorized to make such repairs
5) Intrusion of salt or other substances that promote significant rust or corrosion or
problems from fluids that contain the same substances
6) Consumable parts such as Packing, Gasket, O-ring, Diaphragm, etc.
7) Attachment or accumulation of foreign matter in the pipe, such as dust and scale
8) Problems from fires, natural disasters, or other force majeure which is not
MIYAWAKI’s responsibility
7.3 Warranty limitation
The remedy available under the warranty shall not exceed the sales price of the products
delivered, for any cause whatsoever.

11
8
SERIAL NUMBER (S. No.) DESIGNATION
The following 4-digit or 9-digit “S. No.” is displayed on the product.
●For 4-digit display
S.No. □□□□
Represents the day.
Represents the month.
Represents the year. (last two digits of the
year according to the Western calendar)
●For 9-digit display
S.No. □□□□□□□□□
MIYAWAKI identification number
Represents the month.
Represents the year. (last two digits of the
year according to the Western calendar)
Month designation system
Month 1 2 3 4 5 6 7 8 9 10 11 12
Symbol 1 2 3 4 5 6 7 8 9 X Y Z
Day designation system
Day 1 2 3 4 5 6 7 8 9 10 11 12
Symbol 1 2 3 4 5 6 7 8 9 A B C
Day 13 14 15 16 17 18 19 20 21 22 23 24
Symbol D E F G H J K L M N O P
Day 25 26 27 28 29 30 31
Symbol Q R S T U V W
Example of serial number designation
1 7 1 1 → Jan.1, 2017
2 9 X M → Oct. 21, 2029
Example of serial number designation
1 7 1 1 2 C 0 2 0 → Jan., 2017
2 9
X
0 5
M
0 5
0
→
Oct
.
,
2029

12
9 GUIDANCE FOR READING SPECIAL PRODUCT NAME
〇〇〇-○○-□
Special symbol:
The symbol applies only to
special products
(Please refer to table 1 for details)
Model symbol:
Product model number
Table 1 Symbol description
Suffix Special contents
A Trap for high-pressure gas installed property (only for Gas Trap)
C Blow valve attached
K Change of gasket
L Special face to face dimension
M Change of parts material
P, T Change of operating pressure, temperature, condensate capacity, etc.
R Change of screen mesh
V Change of air vent
X Other than mentioned above or complex of special contents above

© 2020 MIYAWAKI INC.
This user’s manual may not be reproduced or copied in whole or in part, without the
written consent of MIYAWAKI INC.
Some special specifications of the product you have, may found to be different from the
ones in the user's manual. If you have any question, please contact MIYAWAKI, our
local authorized agent, or the company where you purchased the product.
In the interest of the development and improvement of our products, MIYAWAKI Inc.
reserves the right to change the specification of the products without prior notice.

INTERNATIONAL SALES DEPT.
2-1-30, Tagawakita, Yodogawa-ku, Osaka, 532-0021, Japan
Tel: [phone]
www.miyawaki-inc.com/en e-mail: [e-mail]
EU Importer and Authorized representative:
MIYAWAKI GmbH
Birnbaumsmühle 65, 15234 Frankfurt (Oder), Germany
Tel: [phone]
www.miyawaki.de e-mail: [e-mail]
China Importer and Authorized representative:
MIYAWAKI WEST Co., Ltd.
Room 1705, No.1, Building No.311, Yanxin Road, Huishan Economic Development Zone,
Wuxi, Jiangsu, China
Tel: [phone]
www.miyawaki-inc.com.cn e-mail: [email protected]n
808022-05 2112
S31N