Emerson Spence Type N6 User manual
www.SpenceValve.comwww.SpenceValve.com
Spence Type N6 Differential Pressure Valves
▲ WARNING
Failure to follow these instructions or
to properly install and maintain this
equipment could result property damage
and personal injury or death.
Type N6 differential pressure valves
must be installed, operated and
maintained in accordance with federal,
state and local codes, rules and
regulations and Emerson Process
Management Regulator Technologies,
Inc. (Emerson) instructions.
If the valve vents gas or a leak develops
in the system, service to the unit may be
required. Failure to correct issue could
result in a hazardous condition.
Installation, operation and maintenance
procedures performed by unqualified
personnel may result in improper
adjustment and unsafe operation. Either
condition may result in equipment
damage or personal injury. Only a
qualified person shall install or service
the Type N6 differential pressure valves.
Introduction
Scope of the Manual
This manual provides instructions for the installation,
troubleshooting, maintenance, valve setting and parts
ordering for Type N6 differential pressure valves.
Product Description
Type N6 differential pressure valves are designed
to maintain pump discharge pressures at a constant
differential above a separate source of pressure.
When installed in a boiler feed pump discharge line
Figure 1. Type N6 Dierential Pressure Valves
November 2021
Instruction Manual
VCIMD-16088
as a by-pass valve, a connection from the stream
drum is made to the top chamber of the Type N6.
The desired differential is made by adjusting the
spring. The boiler feed-water pressure will then be
maintained by Type N6 at a constant pressure above
steam drum pressure by modulating the quantity of
water by-passed to pump section. When installed in
a by-pass line across a pumped system, Type N6
will maintain a constant differential of supply main
pressure over return main pressure by modulating the
quantity of by-passed water.
Type N6
Specifications
This section lists the specifications for the Type N6 differential pressure valves. Factory specifications are
stamped on the nameplate fastened on the valve at the factory.
Rated Flow Coecient
See Table 1
Materials of Construction
Body: Cast iron
Stem, Disk, Seat Ring, Piston and Spring:
Stainless steel
Sealing Ring: Fluorocarbon (FKM)
Gasket: Graphite
Approximate Weight
See Table 2
Valve Sizes
NPS 3/4, 1, 1-1/4, 1-1/2, 2 and 2-1/2 /
DN 20, 25, 32, 40, 50 and 65
End Connection Styles
NPT and CL250
Pressure Rating(1)
250 psig / 17.2 bar
Temperature Rating(1)
350°F / 177°C
Spring Ranges
5 to 50 psid / 0.34 to 3.4 bar d
40 to 125 psid / 2.76 to 8.62 bar d
100 to 200 psid / 6.89 to 13.8 bar d
1. The pressure/temperature limits in this Instruction Manual and any applicable standard or code limitation should not be exceeded.
Table 1. Type N6 Dierential Pressure Valve Rated Flow Coecients
BODY SIZE FLOW COEFFICIENTS (CV)
NPS DN
3/4 20 7.1
1 25 13.3
1-1/4 32 22.0
1-1/2 40 32.5
2 50 51.0
2-1/2 65 88.0
Table 2. Type N6 Dierential Pressure Valve Approximate Weight
BODY SIZE APPROXIMATE WEIGHT
NPS DN lbs kg
3/4 20 10 4.5
1 25 12 5.5
1-1/4 32 19 8.6
1-1/2 40 26 12
2 50 39 18
2-1/2 65 74 34
2
Type N6
BOILER DRUM PRESSURE BOILER LEVEL CONTROL VALVE
BOILER WATER FEED LINE
TYPE N6 VALVE
1/4 IN. PIPE
BY-PASS LINE
FEED TANK
FEED PUMP
BOILER
Figure 2. Type N6 Installation Drawing
Principle of Operation
Flow enters the valve such that the initial pressure acts
against the working face of the disk and tends to move
it open. Opposing the opening are the forces of the
differential adjusting spring and the loading pressure
acting on the piston. The differential adjusting spring
force creates the differential between the retained
pressure (supply main or boiler feed water) under the
disk and the loading pressure (return main or boiler
drum) on top of the piston.
3
Type N6
Startup and Adjustment
1. Type N6 valves are shipped with the adjusting
spring precompressed. This precompression
may result in a differential pressure higher than
desired. Remove adjusting screw cover and
loosen adjusting screw locknut. It is recommended
that the precompression be removed by turning
the adjusting screw counter-clockwise until the
screw turns easily indicating the spring load has
been removed.
2. Open the inlet stop valve gradually until the
Type N6 differential valve takes control as
indicated by the differential pressure gauge.
3. Turn adjusting screw clockwise to increase the
differential pressure and counter-clockwise to
decrease it.
4. With no compression on the adjusting spring the
pump discharge pressure and the boiler pressure
applied to the spring chamber will be the same,
due to the fact that the piston and the disk have
the same area and are balanced. To increase
differential pressure, compress adjusting spring
until desired differential is obtained.
Maintenance
▲ WARNING
To avoid personal injury, property
damage or equipment damage caused by
sudden release of pressure or explosion
of accumulated gas, do not attempt any
maintenance or disassembly without first
isolating the valve from system pressure
and relieving all internal pressure from
the valve.
Installation
▲ WARNING
Personal injury or system damage may
result if this valve is installed, without
appropriate overpressure protection,
where service conditions could exceed
the limits given in the Specifications
section and/or valve nameplate.
Additionally, physical damage to the
valve may result in personal injury or
property damage due to escaping of
accumulated gas. To avoid such injury
and damage, install the valve in a
safe location.
Under enclosed conditions or indoors,
escaping gas may accumulate and be an
explosion hazard. In this case, the vent
should be piped outdoors.
For valve constructions with a spring
case vent, the vent should be kept
open to permit free flow of gas to the
atmosphere. Protect openings against
entrance of rain, snow, insects or any
other foreign material that may plug the
spring case vent or vent line.
All pressure equipment should be
installed in a non-seismic area;
should not be exposed to fire; and
should be protected from thunderbolt
(lightning) strikes.
△ CAUTION
After the valve is in service at operating
pressure and temperature, check all
gasketed joints and re-tighten. Failure to
follow these instructions may result in
damage to gaskets and mating surfaces.
• Carefully clear inlet piping system of foreign
matter such as: welding beads, scale, sand, pipe
compound, etc.
• Allow head room above the valve for maintenance.
• Provide a three-valve by-pass to facilitate
inspection of the regulator without
interrupting service.
• Preferred position for Type N6 valve is in a
horizontal line with spring chamber up and arrow on
body pointing in direction of flow.
• The loading line should be 1/4-in. pipe connected to
the spring chamber tap.
• Avoid damaging effects of foreign matter in the flow
by using Emerson strainer ahead of the valve.
4
Type N6
Valve Grinding
1. Use fine (grit 400 to 800) compound on the seat,
using light pressure.
2. Check seating by blueing the valve disk bevel face
before reassembling.
3. Clean all parts with kerosene or carbon
tetrachloride before reassembling.
4. Lubricate sealing ring (key 13) with a silicone
lubricant or soap solution to facilitate insertion into
guide area of body. Do not use petroleum base
lubricants on rubber sealing rings.
Dismantling Type N6 Valve
for Cleaning
1. Shut off supply and discharge valves and line from
steam headers.
2. Remove top cap (key 1).
3. Loosen lock nut (key 3) and unscrew adjusting
screw (key 2) until spring tension is released. (This
step can be omitted if setting adjustments cannot
be made after cleaning).
4. Disconnect pressure sensing line from boiler
steam header.
5. Remove the four spring chamber hex head
nuts (key 9).
6. Separate spring chamber (key 6) from the valve
body (key 20). Spring (key 7) and buttons (key 5)
will drop out.
Troubleshooting
1. Failure to Open—differential too high.
a. Differential adjusting spring setting may have
been tampered with.
b. Valve piston (key 14) and sealing ring (key 13)
may be binding.
c. Valve stem (key 18) and bushing (key 19) may
be binding.
2. Failure to Close—differential too low.
a. Foreign material may be between the seat and
disk of the main valve.
b. Line from steam header may be plugged,
restricted or broken.
c. Differential adjusting spring setting may have
been tampered with.
d. Chamber "C" may be dirt plugged or port in
bushing (key 19) may be plugged.
e. O-ring or piston may be damaged and leaking.
To avoid possible personal injury from
spring or pressure-loaded actuator,
make sure that the adjusting screw is
completely backed off or the spring case
pressure is vented prior to disassembly.
Otherwise, the spring load or loading
pressure could forcefully eject the
spring case.
Valves that have been disassembled
for repair must be tested for proper
operation before being returned to
service. Only parts manufactured by
Emerson should be used for repairing
this valve.
Under normal conditions, complete dismantling
at regular intervals is not recommended. A valve
kept relatively free of dirt will function for years with
minimum attention.
After the first few days of operation and twice a year:
1. Inspect for dirt collected in chamber "C". Remove
plug (key 22) to "blow down".
2. Inspect for dirt collected in cylinder (key 12).
3. Inspect all joints for leakage. Keep all joints tight,
never allow a leak to persist.
7. Remove valve disk assembly which consists of
keys 11, 12, 13, 14, 15 and 18.
8. Assemble in reverse order. Use silicone lubricant
on piston (key 14) so that it will move freely
through sealing ring (key 13).
5
Type N6
Viton®is a mark owned by E.I. du Pont de Nemours and Co.
*Recommended Spare Parts
1. Top Cap for 1-1/2, 2 and 2-1/2 in. / 38.1, 50.8 and 63.5 mm is Cast iron.
2. Included in Item 23:
Sizes 3/4 to 2 in. / 19.05 to 50.8 mm inclusive are screwed ends
Sizes 2-1/2 in. is 250 lbs / 113 kg
KEY DESCRIPTION MATERIAL VALVE SIZE, IN. / mm
3/4 / 19.05 1 / 25.4 1-1/4 / 31.75 1-1/2 / 38.1 2 / 50.8 2-1/2 / 63.5
1Top Cap(1) Steel WAL4-01303-0 WAL4-01303-0 WAL4-01303-0 WAL4-01331-0 WAL4-01331-0 WAL4-01331-0
2 Adjusting Screw Steel WAL5-04860-0 WAL5-04860-0 WAL5-04860-0 WAL5-04863-0 WAL5-04864-0 WAL5-04864-0
3 Adjusting Screw Locknut Steel WAL5-02942-0 WAL5-02942-0 WAL5-02942-0 WAL5-02943-0 WAL5-02943-0 WAL5-02943-0
4* Top Cap Gasket Copper
Asbestos WAL5-02356-0 WAL5-02356-0 WAL5-02356-0 WAL5-02357-0 WAL5-02357-0 WAL5-02357-0
5 Spring Buttons Steel WAL0-01040-0 WAL0-01040-0 WAL0-01040-0 WAL5-01060-0 WAL5-01050-0 WAL5-01062-0
6 Spring Chamber Cast iron WAL4-01398-0 WAL4-01399-0 WAL4-01400-0 WAL4-01401-0 WAL4-01402-0 WAL4-01403-0
7 Adjusting Spring
5 to 50 psi / 0.35 to 3.45 bar Aluminum
Steel WAL5-04957-0 WAL5-04958-0 WAL5-04959-0 WAL5-04960-0 WAL5-04961-0 WAL5-04962-0
40 to 125 psi / 2.75 to 8.62 bar 17-7 PH WAL5-04972-1 WAL5-04973-1 WAL5-04974-1 WAL5-04975-1 WAL5-04976-1 WAL5-04977-1
100 to 200 psi / 6.89 to 13.79 bar Aluminum
Steel WAL5-10327-0 WAL5-10328-0 WAL5-10329-0 WAL5-10330-0 WAL5-10331-0 WAL5-10332-0
8 Spring Chamber Studs Steel WAL4-05516-0 WAL4-10118-0 WAL4-05442-0 WAL4-05443-0 WAL4-10119-0 WAL4-05447-0
9 Spring Chamber Nuts Steel WAL5-02847-0 WAL5-02851-0 WAL5-02854-0 WAL5-02856-0 WAL5-02860-0 WAL5-02862-0
10* Spring Chamber Gasket Asbestos WAL5-02381-0 WAL5-02362-0 WAL5-02382-0 WAL5-02365-0 WAL5-02366-0 WAL5-02367-0
11 Cylinder Bronze WAL4-01569-1 WAL4-01570-1 WAL4-01571-1 WAL4-01572-1 WAL4-01573-1 WAL4-01574-1
12* Sealing Ring Viton®WAL5-04021-0 WAL5-04026-0 WAL5-10463-0 WAL5-04034-0 WAL5-04044-0 WAL5-04048-0
13 Stem Locknut Steel WAL5-03015-0 WAL5-03016-0 WAL5-03016-0 WAL5-03017-0 WAL5-03017-0 WAL5-03018-0
14 Piston Stainless
steel WAL4-03336-0 WAL4-03337-0 WAL4-03338-0 WAL4-03339-0 WAL4-03340-0 WAL4-03341-0
15 Disk Stainless
steel WAL4-02007-0 WAL4-01832-2 WAL4-01850-2 WAL4-01870-2 WAL4-01888-2 WAL4-01906-1
16 Seat Ring Stainless
steel WAL4-04075-1 WAL4-04084-1 WAL4-04092-1 WAL4-04496-1 WAL4-11544-0 WAL4-11539-0
17 Body(2) Cast iron - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
18 Stem Stainless
steel WAL4-05311-1 WAL4-05312-1 WAL4-05313-1 WAL4-05314-1 WAL4-05315-1 WAL4-05316-2
19 Bushing(2) 17-7 PH WAL4-01094-1 WAL4-01099-2 WAL4-01095-1 WAL4-10630-0 WAL4-10630-0 WAL4-10522-0
20 Body Cap Cast iron WAL4-01300-0 WAL4-01300-0 WAL4-01301-0 WAL4-01301-0 WAL4-01302-0 WAL4-01325-0
21 Pipe Plug, 1/8 NPT Steel WAL4-03769-0 WAL4-03769-0 WAL4-03769-0 WAL4-03769-0 WAL4-03769-0 WAL4-03769-0
22 Piple Plug, 1/4 NPT Steel WAL4-03772-0 WAL4-03772-0 WAL4-03772-0 WAL4-03772-0 WAL4-03772-0 WAL4-03772-0
23 Body and Bushing Cast iron WAL7-42862-1 WAL7-42863-1 WAL7-42864-1 WAL7-42865-1 WAL7-42866-1 WAL7-42867-1
Repair Kit
(4, 10, 11, 12, 13, 14, 15, 16
and 18)
- - - - - - - WAL7-08362-1 WAL7-08363-1 WAL7-08364-1 WAL7-08365-1 WAL7-08366-1 WAL7-08367-1
Parts Ordering
When corresponding with your local Sales Office about this
equipment, always reference the equipment serial number
that can be found on the nameplate.
When ordering replacement parts, reference the key number
of each needed part as found in the following parts list.
Table 3. Type N6 Parts List
Parts List
Type N6
See Table 3
6
Type N6
1
2
3
4
23
24
25
5
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
1/4 NPT
Figure 3. Type N6 Assembly Drawing
SERIAL NUMBER PLATE
7
Type N6
Type N6
Emerson Automation Solutions
SpenceValve.com
Americas
McKinney, Texas 75070 USA
T +1 800 558 5853
+1 972 548 3574
Europe
Bologna 40013, Italy
T +39 051 419 0611
Asia Pacic
Singapore 128461, Singapore
T +65 6777 8211
Middle East and Africa
Dubai, United Arab Emirates
T +971 4 811 8100
SIOI97
VCIMD-16088 © 2021 Emerson Electric Co. All rights reserved. 11/21
Spence is a mark owned by one of the companies in the Emerson Automation
Solutions business unit of Emerson Electric Co. The Emerson logo is a
trademark and service mark of Emerson Electric Co. All other marks are
property of their prospective owners.
The contents of this publication are presented for informational purposes only,
and while every eort has been made to ensure their accuracy, they are not to
be construed as warranties or guarantees, express or implied, regarding the
products or services described herein or their use or applicability. All sales are
governed by our terms and conditions, which are available upon request. We
reserve the right to modify or improve the designs or specications of such
products at any time without notice.
Emerson Electric Co. does not assume responsibility for the selection, use
or maintenance of any product. Responsibility for proper selection, use
and maintenance of any Emerson Electric Co. product remains solely with
the purchaser.
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