POLNA Z1A User manual

www.polna.com.pl
CONTROL VALVE
Z1A
®
type
INSTRUCTION MANUAL FOR INSTALLATION,
OPERATION AND USE
Edition Z1A/ 10 /20 22

Instruction manual for installation, operation and use
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Technical characteristics of the product
Marking Conformity marking
DN/NPS PN/CLASS PT [bar] TS [°C]
Date of pressure test
Serial number/ year of production
Category acc. to PED Category of fluid Liquid 
Gas 
List of contents:
1. Introduction
2. General warnings
3. Requirements for equipment used in potentially explosive
atmosphere according to Directive 2014/34/UE (ATEX)
4. Conditions of safe use
5. Design and operating principle
6. Dimensions
7. Normal operating conditions
8. Storage and transport
9. Installation
10. Start-up and assembly with drives
11. Service
12. Repair
13. List of spare parts
14. Product disposal
15. Troubleshooting
1. Introduction
The Instruction manual for installation, operation and use is
intended for products designed and manufactured according to
the requirements of the ISO 9001 quality management system,
Pressure Equipment Directive (PED) 2014/68/EU, ATEX
directive 2014/34/UE and AD2000 Merkblatt regulations,
intended for installation on pipelines.
2. General warnings
WARNING
Prior to the product installation and use, read carefully
and follow the Instruction. All activities related to
installation, operation and use of the product have to be
carried out by appropriatly trained and skilled staff.
"POLNA" S.A., hereinafter also called the manufacturer ,
has highly qualified service staff able to assist in
installation, maintenance and repairs of our valves.
The warning symbol in the Instruction means that
the content (of a WARNING or CAUTION message) is very
important due to safety reasons.
The product is intended for installation on pipelines.
Any other use has to be agreed with "POLNA" S.A. at the
stage of ordering of the product. If in doubt, contact
"POLNA" S.A. for explanation before performing any
further actions.
If the product is installed and maintained correctly, its
most ergonomic operation is ensured. However, it is
necessary to follow the requirements given in the
Instruction.
The product has to be installed and maintained
according to domestic and industrial regulations and
instructions.
The Instruction does not cover all cases and incidents
that may occur during installation, use and maintenance or
local safety regulations.
The content of the Instruction is of informative nature
and is considered to be true. The company reserves the
right to modifications, improvements and changes in the
technical data without notice.
"POLNA" S.A. is not liable for a valve selection made
by the buyer on his own or for operation and use of the
valve against its intended use. Failing to comply with the
provisions of this document, in particular when it comes to
use, repairs etc., will result in losing the guarantee and
warranty.
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Instruction manual for installation, operation and use
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3. Requirements for equipment used in
potentially explosive atmosphere
according to Directive 2014/34 UE (ATEX)
3.1 Conditions of completing
Z1A type valves are designed according to the requirements for
equipment operating in potentially explosive atmosphere for
group II, category 2 according to PN-EN 13463-1:2002,
considering the following in particular:
• ensuring operation according to technical parameters
established by the manufacturer and high level of protection,
• using the product in areas that can become potentially
explosive atmosphere caused by air mixtures with gases,
vapour, mist or dust.
3.2 Conditions of use
“Z1A” type valves marked as can be used for operation in
the following zones according to PN-EN 1127-1: 1997:
• Zone 1,
• Zone 2,
• Zone 21,
• Zone 22.
3.3 Conditions for repairs and maintenance
Safety conditions applying to tools and zones where they can
be used according to EN1127-1, Appendix A have to be
ensured during inspections, repairs and maintenance in
explosive atmospheres.
4. Conditions of safe use
The following rules have to be observed to ensure safe use:
• disassembly of the valve from a pipeline or disassembly of
parts in contact with the medium can be performed after
making sure that they are not subject to the action of the fluid
pressure,
• when working at high temperatures take care to avoid burns
caused by hot parts of the valve and use shields wherever
possible,
• valves have to be mounted and installed only by qualified
staff,
• rotation of the valve stem in the bonnet body is not
acceptable in valves with a bellows seal bonnet as the bellows
can become damaged.
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5. Design and operating principle
The basic components of a Z1A type control valve include:
body (1a, 1b), bonnet (2a, 2b, 2c), seat (3), valve plug (4a, 4b),
cage (6a, 6b), plug stem (5) and valve plug stem sealing (13).
Marking and names of components are presented in Figure 1
and Table 1.
The flow of the working medium through the valve is
adjusted by a linear movement of the valve plug with a fixed
connection with the stem of the actuator or manual drive.
Input signal being the following:
a) in pneumatic actuators:
compressed air with the nominal range of the control
pressure between 140 and 600 kPa or within other ranges if
a positioner is used,
b) in electric drives:
with a 3-point control
- electric signal with the supply voltage of 220 V AC; 24 V
AC; 380 V AC, 500V AC etc.,
with continuous control
- voltage signal 0…10 V; 2…10 V or current signal 0…5
mA; 0…20 mA; 4…20 mA, profibus and other
causes linear displacement of the drive stem. The movement is
proportional to the value of the input signal.
Table 1. Marking and names of components.
No. in the
Figure 1
Component name
1a Flanged body
1b Valve body with socket welded ends (BW type)
1c Valve body with socket welded ends (SW type)
2a Standard bonnet
2b Extended bonnet
2c Bellows seal bonnet
3 Seat
4a Contoured valve plug
4b Piston valve plug (perforated)
5 Valve stem
6a Pressing cage
6b Choking cage
7 Body gasket
8 Seat gasket
9 Plug stem pin
10 Guiding sleeve
11 Body screw
12 Body nut
13 Packing
14 Pressing sleeve
15 Pressing lever
16 distance sleeve
17 Spring
18 packing washer
19 Bonnet screw
20 Bonnet nut
21 Fixing nut
22 bellows seal bonnet housing
23 Packing set of bellows seal bonnet
24 Retaining plate
25 Packing set gasket
26 Bellows seal bonnet gasket
27 Pin
28 Retaining ring
29 Nut
30 Plug
31 Bellows seal bonnet housing screw
32 Bellows seal bonnet housing nut
33 Spacer sleeve
34 Packing
35 Distance sleeve
36 Packing set
37 Pressing sleeve
38 Disk spring
39 Pressing plate
40 Low nut
No. in the
Figure 1
Component name
41 Nameplate
42 Grooved pin
43 Actuator connector
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Standard bonnet with PTFE-V
sealing
Extended bonnet with
GRAPHITE sealing
Extended bonnet with live
loading sealing
Bellows seal bonnet with
PTFE+GRAPHITE sealing
Contoured valve plug Piston valve plug (perforated) Pressing cage Choking cage
Flanged body
(FL type)
Valve body with socket welded ends
(BW type)
Valve body with socket welded ends
(SW type)
Fig. 1. Z1A type control valve - internal components
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Fig. 2. Z1A type control valve with a contoured valve plug and choking cage
Fig. 3. Z1A type control valve with a contoured valve plug and choking cage
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Fig. 4. Z1A type control valve with a c
ontoured valve plug and choking cage
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Fig. 5. Z1A type control valve with a perforated valve plug and pressing cage
Fig. 6. Z1A type control valve with a perforated valve plug and pressing cage
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Fig. 7. Z1A type control valve with a perforated valve plug and pressing cage
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6. Dimensions
Valve with a flanged connection (FL type)
Dimension E for the valve plug position - valve closed *) If
mounted with P/R 1000 actuator - dimensions: E=195 mm
and F=115 mm
Valve with socket welded ends (SW type) DN 15 ... 50
Valve with butt welded ends (BW type)
Fig. 8. Dimensions of valves
Table 2a. Connection dimensions of control valves
DN 25 40 50
P N/C
L PN10... CL300 PN63...C L600 CL900; PN160 PN250; CL1500
PN320
PN400;
CL2500
PN10...
CL300 PN63... CL600 CL900; PN160 PN250; CL1500
PN320
PN400;
CL2500
PN10...CL3
00 PN63...CL6 00 CL900; PN160 PN250; CL1500
PN320
PN400;
CL2500
105108988311 0989385759080757063B max 11 8
C
237175155214172145193149135DS
DW 402345326385348306364320306
DM -----270-----254-----254
80DN 100 150
PN/CL PN10...
CL300 PN63...C L600 CL900; PN160 PN250; CL1500
PN320
PN400;
CL2500
PN10...
CL300 PN63... CL600 CL900; PN160 PN250; CL1500
PN320
PN400;
CL2500
CL900;PN160PN63...CL600PN10…CL300
1168155145138128153138133120145105B max 19017816085
C
365287329252217257233206DS
DW 483426498442407447402375
DM --470-----405-----405
DN300 and DN400 - special design,
technical data according to individual
arrangements (ref. to Tables 2a and 2b)
200DN 250
PN10...CL300PN63...CL600PN10...CL300PN/CL PN10...CL300
(kv800) PN63...CL600
255258235190B max
C
439DS 458
DW 539 558
DM -660580-580
NOTE: Weight of a valve with a standard bonnet without an actuator.
Table 2b. Connection dimensions of control valves.
25…50DN 80; 1008050 110080; 100 50 250200; 250200
10…25Kvs 125; 16063; 94402540 63; 94 125; 160 200; 250 94320 125;
160 200; 250
500320 630;
800
108063503880635038503838203820Stroke 0
d
1
M24x1.5M20x1.5M16x1.5M20x1.5M16x1.5M12x1.25
d
2
1)
95.2584.15 / 3 5/16”-18NS2A57.15 / 2 1/4”-16UN2A / 3 3/4”-12UN2A
d
3
201612 24
NOTE:
1)
Dimension d
2
= 84.15 f9 for valves DN80 and 100 with live loading sealing
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Table 3. Face-to-face dimensions of control valves with flanged connections.
DN
Dimension A [mm]
PN / DIN CL
10; 16; 25;
40 63 - 100
250 -320160 CL1500CL900CL600CL300CL150400 CL2500
30827324821019718430026023023016025 35931127025123522235030026026020040 40034031128626725440035030030023050 49846038733631729850045038038031080 575530464394368352580520430430350100 **556508473451**550550480150 ***610568543***650600200 ***752708673***775730250
300 special design, technical data according to individual arrangements
400 * technical data according to individual arrangements
"A" face-to-face dimensions given in Table 3 foNOTE: r CL150; CL300; CL600; CL900; CL1500 and CL2500 apply to bodies
with face B (RF). For other designs, the A1 lengths can be calculated based on the relation specified in Table 4.
Table 4. Algorithms for calculating the lengths of control valves with flanged connections.
- with a groove
- with races
- with a groove for a ring
Body type and marking
Pressure CL DN A
1
PN / ANSI
With a groove
DL / (GF)
With races
F / (FF)
CL300
25…250
A = A + 5 x 2
1
CL600
CL900
CL1500
CL2500
A = A - 1.5 x 2
With a groove for a ring
J / (RTJ)
CL150 25…250
A = A +6.5 x 2
CL300 25…40
CL300 50…250
A = A + 8 x 2
1
CL600
CL900
CL1500
25…40
A
1
= A
CL2500 25
CL600 50…250
A = A + 1.5 x 2
CL900
CL1500
50…100
CL900 150
CL2500
80
A = A + 3 x 2
1
100 A = A + 4.5 x 2
Table 5. Face-to-face dimensions of control valves with butt welded ends
DN
Dimension A [mm]
Nominal pressure identification
PN 10...CL600
CL900…PN160
PN250...CL2500
25 210 230 300
40 251 260 350
50 286 300 400
80 337 380 500
100 394 430 580
150 508 550 -
200 610 - -
250 752 - -
300
special design, technical data according to individual arrangements
400
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7. Normal operating conditions
NOTE
The control valve should be used at pressure,
temperature and medium type with parameters complying
with the ones assumed for calculating the value and for
identifying the design and material variant of the valve. To
ensure failure-free operation during the whole service life,
the control valve and its accessories and equipment have
to be protected against impact and damage and subject to
regular maintenance and periodical inspections.
A valve used at high (> 50°C) or low temperatures (<
0°C) has to be properly insulated or marked. Failing to
observe this condition may result in personal injury.
It is forbidden to disassemble the actuator or drive from
the valve, if the valve is under pressure. Moving parts of
the valve may cause body injury.
8. Storage and transport
NOTE
The valve shall be stored under conditions ensuring its
failure-free operation even after a long period of storage.
Warehouse spaces should be closed, dry and airy with
the relative humidity not exceeding 80%. The atmosphere
should be free of vapours and aggressive gases.
The valve can be transported by any covered means of
transport, with or without its packaging, protected against
throwing, collapsing or excess shock. During packing,
loading or unloading handle the valves using flexible
clamps (e.g. rubber V-belts) wrapped around the valve
body flanges and actuator diaphragm case (through an eye
bolt - for pneumatic actuators ).
9. Installation
Exercise care while unpacking the valve so as not to
damage the valve or its accessories. If any problems occur,
contact "POLNA" S.A.
WARNING
Z1A type control valves (Edition_ 10/2022 )
Prior to installing the valve, read carefully the
Instruction. The Instruction contains information and
warnings on safety that have to be observed strictly.
Otherwise a serious injury to the operator or persons
standing nearby may occur or the equipment may be
seriously damaged.
Prior to installing the valve in a pipeline system, the
following have to be performed:
1. Carefully clean the pipeline of contaminants, metal
chips, rust, welding and rolling scale, fat and grease and
any other foreign bodies. It is of particular importance for
valves with a perforated plug or control cage. Thoroughly
clean the surface of gaskets to ensure correct tightness of
connections.
2. Remove caps and elements of transport packaging
from the valve to be installed.
3. If the valve is activated for the first time after more
than 3 months from the date of its purchase, check the
stem movement smoothness prior to its installation on the
site. Start the actuator or drive and check whether the
valve stem (5) moves smoothly and with no disturbance
within the entire range of the nominal stroke. If the
movement is not smooth, contact "POLNA" S.A. service.
4. The allowed position of the control valve is with the
stem vertically upwards. In justified cases, it is possible to
install the valve with a permissible deviation of ±30° from
the vertical. Other positions may cause uneven and
accelerated wear of internal parts of the valve (plug, seat,
stem, guide sleeve) and seals.
If it is necessary to use a different valve installation
position on the pipeline than permitted, consultation with
the valve manufacturer is mandatory.
Without the approval of the manufacturer, an
unauthorised installation position will result in loss of
guarantee.
5. The valve shall be installed so that the direction of
the working medium flow in the pipeline is according to
the direction marked by the arrow on the valve body. If the
direction of the flow is not marked in the centre of the
body, it is marked on the flange.
6. The working pressure of the medium flowing through
the valve should comply with the value assumed for the
nominal pressure given on the valve nameplate.
7. When installing the valve, follow standard
procedures for making pipe connections and welding.
Use a correct gasket between the valve flange and the
pipeline system with flanged connections.
8. The valve location should take the
following requirements into account:
- straight sections of the pipeline 20xDN before the
valve and 10xDN after the valve. In systems intended for
light working conditions and less serious applications,
straight sections with the minimum lengths of 6xDN before
the valve and 3xDN after the valve can be used.
- pressure measurement points ca. (1-2)xDN before the
valve and (4-6)xDN after the valve,
- distances to provide access to the actuator - min. 300 mm
around the diaphragm case and min. 500 mm above the
actuator.
9. If the valve is welded, welding shall be
performed observing safety measures i.e. at many
sections so that the body interior is not heated to a
temperature exceeding the maximum acceptable
temperature or so that no contaminants, e.g. scale,
get inside the valve. The valve has to remain open
during welding ( plug lifted above the seat ).
10. If the nominal diameter of the valve is smaller than
the diameter of the pipeline, use appropriate reducers
whose length complies with relevant standards. In such
cases, avoid using threaded, femal-male reducers etc. In
process system units it is recommended to use a by-pass
system composed of three additional valves, allowing for
disconnecting the control valve from the system (e.g. for
making repairs, grinding of seats, replacement of parts)
with no breaks in the operation.
11. When connecting with adjacent elements pay
attention not to stress the body and adapt the connecting
elements (screws, sealing rings, flanges) to the shape of
the body and its operating conditions. If necessary, use a
support to prevent stress to the body (the support can be
placed under the valve flanges).
12. Make sure that lifting equipment, chains and slings
with appropriate load bearing capacity are used for
handling the valve.
13. Do not paint the screws when painting pipelines. If
construction works are carried out, protect the fixtures
against dust, sand and residues of building materials (they
should be covered with appropriate materials).
14. The manufacturer is not responsible for fixtures, if
the user fails to observe the provisions of the Instruction.
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10. Start-up and assembly with drives
Prior to start-up of the process system, check the operation
of the installed valve. Start the actuator or manual drive and
check whether the valve stem moves smoothly and with no
disturbance within the entire range of the nominal stroke. If the
movement is not smooth, contact "POLNA" S.A. service.
NOTE
Prior to start-up, take the following recommendations
into consideration:
1. The first filling of the pipeline has to be performed
with the valve open.
2. Use the by-pass or completely cut-off the valve from
the working pressure and then release process pressure
on both sides of the valve. Avoid a sudden release of the
working pressure as it may cause injury to the operators.
Release the process medium on both sides of the valve.
3. The bonnet nuts are tightened in the plant before
delivery but before starting the valve make sure they have
not come loose or that there is no leakage within the valve
stem. A leaking bonnet may cause injury to the operators.
If there are leaks within the valve stem, perform
relevant actions described in the Instruction (Table 9).
4. For pneumatic actuators - vent the actuator system
and relieve the tension of its springs.
5. To avoid injury, when doing installation and service
works, wear gloves, protective clothing and glasses.
6. Always check occupational safety with the
responsible person whether there is no need to take extra
precautions against the process medium.
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Assembly with valves
Fig. 9. Z1A type control valve with P/R pneumatic actuator Fig. 10. Z1A type control valve with P1/R1 pneumatic actuator
Fig. 11. Z1 type control valve with a post-style electric drive Fig. 12. Z1A type control valve with electric drive and linear
gear
Prior to assembly, installation and adjustment of Z1A type control valves with pneumatic and electric drives, read the
instructions in the Operation and Maintenance Documentation of the drive manufacturer.
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11. Service
The service of a control valve during its use involves
maintaining appropriate tightness of the valve pressure
chamber and ensuring its operating capacity.
For valves operating on a continuous basis it is
recommended to perform regular inspections every 6 months,
while for valves operating on a non-continuous basis every 12
months. The inspection covers a visual check of the valve
operation, checking its external tightness, settings and correct
adjustment. If the valve does not operate correctly, e.g. there
are leaks on the bonnet partition or within the stem, the valve
jams during operation or reveals poor adjustment, perform
relevant actions described in the Instruction (Table 9).
If the valve operates correctly, there is no need to perform
disassembly or inspection of internal parts.
12. Repair
The following activities shall be performed within the repair:
• cleaning of the valve and evaluation of the degree of its
components wear,
• grinding of the seat and valve plug,
• replacement of the seat, plug and stem,
• replacement of the valve bonnet gaskets,
• replacement of the body, seat and plug gaskets,
• replacement of the housing gaskets and packing set (for a
bellows bonnet).
WARNING
Prior to repair, release the pressure in the whole valve
and cool it down.
Disconnect all supply cables of compressed air as well
as electric and signal supply cables from the actuator or
drive. Make sure that the actuator or drive cannot
incidentally open or close the valve. Never disassemble an
actuator or drive from the valve when the valve is under
pressure.
Disconnect the valve from the rest of the system with
cut-off valves and release the working fluid.
Disassembly a bonnet under pressure poses a potential
hazard to life!
The valve bonnet may contain process medium under
pressure, even if the valve has been removed from the
process system. The process medium can flow under
pressure when the bonnet elements or sealing rings are
being disassembled.
To prevent penetration of foreign bodies into the body
and to avoid damage to the equipment, cover the hole in
the valve body.
NOTE
It is recommended to use original spare parts. If the
user fails to observe the rule, it releases the
manufacturer from the liability for the product, leads to a
loss of guarantee rights and may result in incorrect
operation of the valve, constituting hazard to occupational
safety.
Internal elements of the valve are accessible after removing
the actuator or drive. When removing the actuator or drive,
perform the following:
a) disconnect the cables supplying the input signal to the
actuator or drive and remove the valve from the system. In the
case of a pneumatic actuator with a positioner, disconnect the
line supplying the electric control signal and supply air,
b) disconnect the connection between the valve stem and
the actuator of drive stem,
c) loosen the nut (21) mounting the actuator or drive and
disconnect it from the valve,
After removing the actuator or drive, disassemble the valve
and separate its internal components as described below.
12.1 Disassembly of the bonnet
12.1.1 Valve with a contoured and perforated plug
a) loosen the nuts (20) of the bonnet screws,
b) loosen the nuts (12) on the body screws,
c) disassemble the bonnet (2a, 2b) with the stem (5) and
plug (4a, 4b) as one assembly,
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d) remove the pressing cage (6a) or choking cage (6b) from
the body interior,
e) remove the seat (3) with gaskets of the body (7) and
seats (8),
f) clean and check the condition of the sealing surfaces of
the body for the seat and bonnet and the body interior,
g) clean and inspect the condition of the face surfaces of
the seat (3) and plug (4a, 4b) and guiding surfaces of the stem
(5) and plug,
h) check whether the pass-through holes of the pressure
cage or choking cage (6a, 6b) and perforated plug (4) are not
clogged. Restore passage of the holes, if necessary.
12.1.2 Valve with a bellows bonnet
a) loosen the nuts (20) of the bonnet screws,
b) undo the nuts (32) on the screws of the bellows seal
bonnet housing,
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c) disassemble the bellows seal bonnet (2c),
d) undo the nuts (29) taking care so as not to overtighten
the packing set of the bellows bonnet, as it may result in the
damage to the bellows,
e) remove the retaining ring (28), retaining plate (24) and
gaskets (25, 26),
f) loosen the nuts (12) on the body screws,
g) disassemble the bellows seal bonnet housing (22) taking
care so as not to damage the bellows,
h) remove the valve plug as a whole (4a, 4b) together with
the packing set (23), taking care so as not to damage the
bellows,
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i) remove the pressing cage (6a) or choking cage (6b) from
the body interior,
j) remove the seat (3) with gaskets of the body (7) and
seats (8),
k) clean and check the condition of the sealing surfaces of
the body for the seat and bonnet and the body interior,
l) clean and inspect the condition of the face surfaces of the
seat (3) and plug (4a, 4b) and guiding surfaces of the stem (5)
and plug, as well as the packing set of the bellows seal bonnet
(23),
m) check whether the pass-through holes of the pressing
cage or choking cage (6a, 6b) and perforated plug (4b) are not
clogged. Restore passage of the holes, if necessary.
12.2 grinding of the seat and valve plug
If excess leakage of the shut off is discovered, it is
necessary to grind the face surfaces of the seat and plug again.
NOTE
Due to the possible damage to the bellows, grinding of
the valve plug at the bellows seal bonnet should be
performed by the manufacturer 's service.
grinding is carried out for contoured and perforated valve
plugs. The following actions shall be performed after
disassembly of the bonnet according to p. 12.1.1:
a) insert the seat (3) with the seat gasket (8) and the body
gasket (7) into the body interior, paying attention to the coaxial
alignment,
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b) insert the pressing cage (6a) or choking cage (6b) to the
body interior,
c) apply a thin and homogenous layer of grinding paste to
the face surface of the seat (3) and plug (4a, 4b),
d) carefully apply the bonnet (2a, b) with the plug (4a, 4b)
and stem (5) to the valve body, fixing it with four nuts on
opposite sides,
NOTE
At this point do not tighten the nuts with the torque for
normal installation of the valve. The role o the bonnet in
this process is only to guide the stem.
e) grind the face of the seat and plug turning the stem
manually several times by 45 degrees in both directions,
pressing it slightly towards the seat,
NOTE
Perform the grinding carefully, using fine-grain
abrasive agent. Remember that if it is pressed too hard,
the quality of the face surfaces can be deteriorated. The
sealing surfaces of the plug and seat must be free of any
large scratches, cracks, chipping and the contact surface
should be as smooth as possible.
f) lift the stem, turn it by about 30 degrees and carefully
lower it towards the seat and repeat the actions described in
point e),
g) repeat the abovementioned actions several times until
the plug performs a full turn,
Z1A type control valves (Edition_ 10/2022 )
EN

Instruction manual for installation, operation and use
- 20 -
h) once the grinding is completed, remove the bonnet with
the plug, stem and gaskets, remove the pressing or choking
cage, thoroughly clean the seat and plug of the residues of the
grinding paste with washing benzene and check the condition
of the grinding face surfaces.
12.3 Replacement of the seat
If it is not possible to grind the seat due to its excess wear
or damage, replace the seat with a new one. Perform the
following actions after removing the bonnet according to p.
12.1.1 ...2:
a) remove the old seat (3) and the seat gasket (8) and
thoroughly clean the body interior,
b) clean and check the condition of the sealing surfaces of
the body for the seat,
c) insert a new gasket into the seat and the seat into the
body interior, and proceed to perform actions as mentioned in
the instruction.
12.4 Replacement of the stem
The guiding surface of the stem has the greatest effect on
the bonnet tightness. If serious wear of the guiding surface of
the stem or damage to the stem is discovered, the stem has to
be replaced.
12.4.1 Valve with a contoured and perforated plug
Perform the following actions after removing the bonnet
according to p. 12.1.1:
a) fix the plug (4a, 4b) with the stem (5) in a vice
NOTE
Be careful when placing the plug in the vice so as not
to damage the working surfaces of the plug.
Always use vice jaws made of soft metal or other soft
material.
b) beat out the pin with a knocker,
NOTE
Z1A type control valves (Edition_ 10/2022 )
EN