BS&B 6400 Instructions for use

INSTRUCTIONS AND MAINTENANCE MANUAL
SAFETY VALVES
MODELS 6400
MA-64/07
NOVEMBER 2020

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VALVULAS NACIONAL, S. A. recommends you read this Instructions Manual carefully, where you can find the minimum
precautions to be taken into consideration before the installation of the safety valves to ensure their correct operation.
VALVULAS NACIONAL, S. A. guarantees its safety valves against all kind of manufacture flaws for a 12-month period
from their installation or maximum 18 months after their delivery, whichever occurs first. Furthermore, the company
declines all responsibilities resulting from malfunction caused by an inaccurate installation, storage and / or handling by
the buyer.
VALVULAS NACIONAL, S. A. considers that any safety valve with a non-original spare part installed, and / or where the
certifying seal is missing as void of any guaranty.
The instructions written in bold text and in boxes must be given particular attention, as their purpose is to avoid
incurring in a faulty installation, and mainly, to prevent that someone manipulating the safety valve may suffer
any harm during the operation.
VALVULAS NACIONAL, S. A. reserves the right to modify all or part of the contents of this manual without previous
notification.

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MAIN DEFINITIONS
(UNE-EN ISO 4126-1)
Safety valve: Valve which automatically, without the assistance of any energy other than that of the fluid concernet,
discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and which is designed
to re-close and prevent further flow of fluid after normal pressure conditions of service have been restored.
Pressure: The pressure unit used in this standard is the bar (1 bar = 105 Pa). It is quoted as gauge (relative to
atmospheric pressure) or absolute as appropriate.
Set pressure: The predetermined pressure at which a safety valve under operating conditions commences to open.
Maximum allowable pressure: The maximum pressure for which the equipment is designed as specified by the
manufacturer.
Overpressure: A pressure increase over the set pressure, at which the safety valve attains the lift specified by the
manufacturer, usually expressed as a percentage of the set pressure.
Re-seating pressure: The value of the inlet static pressure at which the disc re-establishes contact with the seat or at
which the lift becomes zero.
Cold differential test pressure: The inlet static pressure at which a safety valve is set to commence to open on the test
stand. This test pressure includes corrections for service conditions, e. g. back pressure and/or temperature.
Relieving pressure: The pressure used for the sizing of the safety valve which is greater than or equal to the set
pressure plus the overpressure.
Built-up back pressure: The pressure existing at the outlet of a safety valve caused by flow through the valve and the
discharge system.
Superimposed back pressure: The pressure existing at the outlet of a safety valve at the time when the device is
required to operate.
Blowdown: The difference between the set and re-seating pressures, normally stated as a percentage on the set
pressure of a safety valve.
Lift: The actual travel of the valve obturator away from the closed position.
Flow area: The minimum cross-sectional flow area (but not the curtain area) between inlet and nozzle which is used to
calculate the theoretical flow to discharge.
Flow Diameter: The diameter corresponding to the flow area.

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CONTENTS
PAGE
1 - INTRODUCTION 5
2 - DESCRIPTION 5
3 – TRANSPORTATION AND STORAGE 5
4 – INSTALLATION 5
4.1 – HYDROSTATIC TEST OF INSTALLATION 6
5 – MODIFICATION OF SET PRESSURE AND BLOWDOWN 7
5.1 – SET PRESSURE MODIFICATION 7
5.2 – BLOWDOWN ADJUSTMENT 7
6 – MAINTENANCE 8
6.1 – ASSEMBLY AND DISASSEMBLY OF THE 64GC AND 64LC MODEL VALVES 8
6.1.1 – DISASSEMBLY 8
6.1.2 – ASSEMBLY 8
6.2 – ASSEMBLY AND DISASSEMBLY OF THE 64GF, 64LF, 64GP AND 64LP VALVE MODELS 9
6.2.1 – DISASSEMBLY 9
6.2.2 – ASSEMBLY 9
6.3 – DISASSEMBLY AND ASSEMBLY OF LEVER CAP 9
6.3.1 – DISASSEMBLY 9
6.3.2 – ASSEMBLY 10
6.4 – RECONDITIONING OF CLOSING SURFACES 14
6.4.1 – LAPPING OF CLOSING SURFACES 14
6.4.2. – NOZZLE MACHINING 14
6.4.3 – DISC MACHINING 14
7 – SET PRESSURE ADJUSTMENT AT THE TEST BENCH 14
7.1 – GASES AND VAPOURS 15
7.2 – LIQUIDS 15
7.3 – TEMPERATURE AND BACKPRESSURE CORRECTIONS 15
7.4 – ADJUSTING RING POSITION 16
7.5 – SET PRESSURE ADJUSTMENT 16
8 – TIGHTNESS TEST 16
8.1 – TIGHTNESS TEST WITH AIR 16
8.2 – TIGHTNESS TEST WITH WATER 17
8.3 – EXCESSIVE LEAK 17
9 – TEST PRESSURE GAUGES 17
10 – ATEX MARKING 17
10.1 – SAFETY RECOMMENDATIONS 17
– TABLE OF POSSIBLES ANOMALIES AND SOLUTIONS 18

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1 – INTRODUCTION
The purpose of this manual is to provide all the
information required for the correct installation and
maintenance of model 6400 safety valves.
2 – DESCRIPTION
The model 6400 safety valves have been designed,
manufactured and tested in compliance with the
Pressure Equipment Directive 2014/68/UE Category IV
and Directive 2014/34/UE (ATEX) Group II Category II.
The model 6400 safety valves are safety devices whose
main function is to protect all kinds of pressurised
containers, with gases, vapours, liquids or mixtures,
from excess pressure.
For improved performance, the internal parts of the
valve have been designed depending on whether the
application is to work with gas of liquid. In both cases,
the valve opens instantly (pop).
Model 64G.- Designed to work with gases or vapours.
Model 64L.- Designed to work with liquids or gas-liquid
mixtures.
Depending on the requirements of the application, they
can be supplied as conventional valves (C), bellows
valves (F) or as piston valves (P).
They are constructed with an angle of 90º between the
inlet and outlet connections. The flanged body has a
large internal capacity to avoid backpressures when the
valve discharges. Other parts are: a fixed complete
nozzle easy to disassemble, a closed bonnet, an
helicoidal spring-loaded, a disc holder mechanism
designed accurately to obtain a good discharge
coefficient with both gases and liquids. Perfect alignment
of the guided components, avoiding rubbing and
premature wear and tear.
All safety valves are calculated and manufactured for a
specific application. If you wish to reuse an existing
valve for any other application, you must contact the
V.N. Technical Department for the corresponding
adaptation study.
3 – TRANSPORTATION AND STORAGE
The internal components of the safety valve are
precision-manufactured and fitted in such a way that
they will remain perfectly aligned.
Rough handling can damage the closing surfaces or
unalign the internal parts of the valve, causing leaks
or malfunctions. Therefore, handle the safety valve
with care.
Do not remove the adhesive protective disc that covers
the inlet and outlet flanges until the valve is in its final
position. This ensures the protection of the closing
surfaces and prevents foreign bodies from entering into
the internal chamber of the valve.
Carbon steel valves are protected externally with a
phosphated anticorrosive primer coat and enamelled
final coat which provides the valve a strong external
protection from oxidation. The studs and nuts are
protected with a dichromatized, a protection electrolytic
treatment.
If the valves have to be stored for a long period of time,
it is better not to remove them from their packing. It is
essential for the adhesive disc that protect the inlet and
outlet flanges not to be removed until their installation. It
is recommended the warehouse atmosphere to be
clean, dry and protected from open-air. If this is not
possible, the valve must be appropriately protected to
prevent from deterioration.
4 - INSTALLATION
Correct installation is essential for the safety valve to
operate correctly.
Remove the adhesive protective discs from the inlet
and outlet flange.
Once the valve has been fitted, it will probably need to
be serviced in the short term when the valve has not
been installed correctly, when the protected line is
contaminated with dirt or slag, when it is given a use for
which it was not designed or when the valve is not
handled correctly.
Before fitting the valve, make sure that the valve is
correct by checking the identification plate. Make sure
the seal has not been broken (otherwise, the set
pressure and tightness have to be checked again). Make
sure the valve is perfectly clean and that there is no dirt
inside the nozzle or in its body. If necessary, perform a
blow.
The pipe, the connection flanges and the valve holders
must be perfectly clean. You must be completely certain
that there are no foreign bodies such as particles on the
gaskets, slag, and/or dust which could be deposited on
the closing surface between the disc and the nozzle.
All the bolts that fasten the valve to the container must
be cross-fastened evenly to prevent deformations to the
body of the valve.
When the discharge is performed through a pipe to the
atmosphere, make sure that no water, dirt or
condensation accumulates inside the body of the valve.
The free discharge pipes must be fastened securely to
prevent the stress produced during discharge being
withstood by the neck of the valve.
The valve must always be fitted in vertical position. The
valve inlet pipe from the equipment or the installation
must be direct and as short as possible. The return
connection to the tank must be curved to avoid
turbulence and to enable the discharge of the fluid by
the valve.

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The bellows valves have a screwed orifice on the
bonnet (vent) which must be in contact with the
atmosphere (Figure -1). If the fluids with which the
valve works are pollutant or dangerous and in the
event of a possible leak through the bellows, this
orifice must be piped to a safe place and at
atmospheric pressure (Figure-2).
Do not cover it up under any circumstances!!
Under no circumstances the pressure drop between the
tank and the valve must be greater than 3% of the set
pressure when the valve is discharging the maximum
flow. If the pressure drop is greater, chattering may
occur.
Check that the diameter of the inlet pipe is greater or
at least equal to the diameter of the corresponding
inlet connection.
The body of the valve has been dimensioned to
withstand great mechanical stress; however, the
installation of the discharging pipe must be studied in
detail so that it does not transmit tension to the valve.
Sliding holders must be used in the installation and
excessively long pipes fixed directly to the valve
discharge flange must be avoided.
With valves to be used with gases, vapours or water
steam, the discharge pipe must be directed upwards and
be fitted with the appropriate discharge. The valves that
work with liquids should be directed downwards to
prevent the body of the valve from flooding.
Never point valves outlets, in service with gases or
vapours, to areas where a danger for people could
exist.
In gases or vapours installations, when the valve
poppes, a noise level that exceeds the allowed
decibel limit for persons working in the area near the
valve, may be produced.
All the safety valves have a drainage orifice in the
bottom part of the body. Whenever necessary, connect a
tube to the drainage orifice and conduct it to a safety
recipient. This prevents the accumulation of water,
corrosive liquids, contaminants and other products that
might deteriorate the internal parts of the valve. See
Fig.-3.
When several safety valves discharge to the same
collector, the backpressure generated during the
opening of one or more of them can cause indirect
backpressure on the remaining valves. This can cause
an increase in the set pressure by a value equal to the
backpressure generated. In such cases, the valves
should be fitted with bellows (balanced) so as not to be
affected by the backpressure.
In the case of containers with saturated vapour, the
valve must be fitted on the vapour side as far away as
possible from the surface of the liquid.
In all installations, do not fit the safety valve in positions
where residue can accumulate.
During the installation, bear in mind that the valve must
be fitted and removed for maintenance; consequently,
there must be a free access area around the valve.
The vibration of the pipes and the containers on which
the valve is fitted may compromise the tightness and
service life of the valve. Excessive turbulences of the
fluid and pulsations of valve inlet pressure might cause
chattering of the disc on the nozzle (fast opening and
closing of the valve) during the discharge, reducing the
tightness and the service life of the valve.
In the installations where the vibrations cannot be
eliminated, we recommend to increase the difference
between the operating pressure and the set pressure by
a minimum of 20%.
For other installation recommendations, please consult
API-RP520 “Design and Installation of Pressure –
Relieving System in Refineries”.
4.1 HYDROSTATIC TEST OF INSTALLATION
When the hydrostatic test of a container or installation is
required, make sure that the safety valve will not be
deteriorated.
Before making the test “water upwards”, remove the cap
plug (22) and fit the test-gag (36) to cancel the valve. To
prevent damage to the internal parts, tighten the test-
gag by hand. See Fig.-4.
VENTEO A LUGAR
SEGURO
VENTEO
ATMOSF
É
RICO
FIGURA - 1 FIGURA - 2
DRENAJE A LUGAR
SEGURO
FIGURA - 3

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Immediately after the hydrostatic test has
concluded, replace the test gag with the plug,
otherwise the safety valve will remain cancelled and
the installation will not be protected from excess
pressure.
When the hydrostatic test is performed “water
downwards”, make sure that the pressure to which the
valve is to be subjected does not exceed the design
limits, especially with belows valves. If possible, we
recommend disassembling the valve and performing the
test by installing a “blind” flange.
5 – MODIFICATION OF SET PRESSURE
AND BLOWDOWN
All the valves manufactured and expedited by
VALVULAS NACIONAL have been carefully assembled,
tested and certified before their expedition.
We recommend that before fitting the valve in the
installation you test it again to make sure that the closing
elements and, therefore, the tightness, have not been
damaged during transport and handling.
If for any reason it is required to modify the adjusting
range of the valve, please consider Section 5.1
5.1 SET PRESSURE MODIFICATION
To modify the set pressure on an existing valve, the
use of a properly selected spring is crucial.
Please consult VALVULAS NACIONAL to check and
supply the spring and the new specifications plate.
The use of the spring for set pressures that are higher
than those for which it was designed can lead to a lower
disc holder lift (and consequently a smaller discharge
capacity) and greater overpressure on the protected
equipment. Similarly, the installation of a spring below its
range can endanger the mechanical resistance of the
spring and increase the blow-down, which means that it
is more difficult for the valve to close after it has opened.
Before increasing the set pressure of an installed valve,
make sure that the new pressure is within the nominal
pressure range for which it has been designed. Similarly,
before decreasing the set pressure, check that the
discharge capacity with the new pressure is enough to
protect the container with which it operates.
Once you are absolutely certain that the selected spring
is correct for the new application, complete the change
by following the instructions given in Section 6.
5.2 BLOW-DOWN ADJUSTMENT
The reduction of the re-seating pressure with regard to
the set pressure when the valve closes after popping
can be adjusted by the adjusting ring (7), mounted on
the nozzle (4). Check drawings on pages 10; 11 and 12.
Valves from VALVULAS NACIONAL are designed with a
standard range of the blowdown value between 10%
and 15%. To complete the adjustment, proceed as
follows:
Unscrew the lock screw (14) which contains the lock
stud (22) that fixes the adjusting ring (7).
Through the orifice of lock screw and using a
screwdriver, turn the adjusting ring upwards
(anticlockwise) until it comes into contact with the disc
holder (8), then make it come down by turning it
clockwise as many notches as indicated in table 1.
Table -1
ORIFICE
V
ALVE MODEL
64G (C,F,P)
GAS
64L (C,F,P)
LIQUID
D, E 2 2
F3 2
G3 3
H4 3
J5 4
K7 5
L9 7
M 12 9
N 14 10
P 17 12
Q 15 11
R 18 14
T 23 16
Notch correction from contacting with disc holder
Once the adjusting ring has been adjusted, the lock
screw has to be re-assembled, checking that the stud
remains placed inside the notch of the adjusting ring,
and fixing the adjusting ring to keep it from spinning, but
free for its auto-alignment.
To increase the blow-down (the valve closes at a very
low inlet pressure), the adjusting ring must be raised by
turning the notches anticlockwise (from left to right).
To decrease the blow-down (the valve closes at a very
high inlet pressure), the adjusting ring must be lowered
by turning the notches clockwise (from right to left).
TORNILLO BLOQUEO
TEST-GAG
FIGURA - 4

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6 - MANTEINANCE
If the valve has been operating on an installation
with fluids classified as dangerous or contaminant,
it must be decontaminated before it is touched.
It is extremely important to follow the disassembly
instructions in order as follows, otherwise it may be
dangerous for the worker who manipulates the
valve, owing to the spring stress.
6.1 DISASSEMBLY AND ASSEMBLY OF THE 64GC
AND 64LC MODEL VALVES
To assembly and disassembly, please consult the valve
section drawings on Page 10.
6.1.1 DISASSEMBLY
Unscrew the nuts (25), remove the cap (3); (for screwed
caps, disassembly unscrewing it by turning it
anticlockwise).
To disassembly the lever cap, see Section 6.3 and
Figure-7.
Before loosening adjusting screw (11), take note of the
distance from the top of it to the end of the stem (9). You
will then be able to return the adjusting screw to the
same position during assembly.
Loosen the adjusting screw nut (13) and set free the
spring stress (10) unscrewing the adjusting screw (11).
Disassembly the bonnet (2) unscrewing body nuts (24).
Do not perform this operation under any
circumstances unless you are completely sure that
spring stress has been completely set free.
Disassembly the spring (10) and the spring buttons (15).
Pull on the stem (9), to remove the set composed of the
following parts: guide (6), push rod (12), disc holder (8)
and disc (5). To disassemble this set, unscrew the disc
holder from the push rod, setting free the stem-push rod,
the guide and the set composed of disc-disc holder. To
disassemble the disc from the disc holder, screw in the
drill it has for this purpose a screw or tool which allows
to extract it from the disc holder. See Fig.-5.
Unscrew the adjusting ring (7), once the lock screw (14)
has been removed, which is fixed by the lock stud (20).
To disassembly the nozzle (4) from the body (1) of the
valve, fix the body and, use the drill of the outside
diameter of the nozzle and with a suitable tool, turn it
anticlockwise.
6.1.2 ASSEMBLY
The procedure to assemble the valve will be exactly the
opposite of the one used to disassemble it.
All components must be cleaned, checked and polished
insisting on sliding and frictional surfaces.
When assembling, it is extremely important to grease all
screwed unions, sliding guide areas and the different
kneecap points that prepare the internal parts of the
valve for self-centring. See Fig-6.
For a good performance of the valve it’s extremely
important to keep the internal components aligned.
FIGURA - 5
FIGURA - 6

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Replace all the gaskets. The reuse of them can lead to
malfunctions, such as leaks, connected chambers and
variations in the opening lift.
The blow-down adjusting ring must be fitted taking into
account its position before it was removed or consulting
Table 1 (turn clockwise the same number of notches,
from the contact position of the ring with the disc holder).
To assemble the disc inside the disc holder, put the disc
holder with the bell positioned upwards; place the disc
with the elastic ring in position and press it in.
As the nozzle and the disc closing surfaces are lapped
with a “mirror like” finish, it is important to fit them very
carefully so that they do not receive any knocks, since
no matter how slight the knock, it could make marks
and, consequently, lead to fluid leaks, making it
necessary for it to be removed and relapped.
Press adjusting screw until the position noted during the
disassembly. This will prevent unnecessary pops and,
therefore, this will reduce possible marks on the closing
surfaces of the valve.
6.2 DISASSEMBLY AND ASSEMBLY OF THE
64GF, 64LF, 64GP AND 64LP VALVE MODELS
To assembly and disassembly these models of valve,
consult the valve section drawings on Pages 11 and 12.
During the assembly and disassembly of these valve
models, particular care must be taken due to the fact
that they include a bellows (33), which is an extremely
fragile component. If handled roughly, it may go out of
shape and be useless for refitting.
6.2.1 DISASSEMBLY
The valves 64GF; 64LF; 64GP y 64LP are
disassemblied in the same way as the 64GC y 64LC,
except for the disassembly of the bellows, which is
carried out as follows:
Once have extracted stem (9), push rod (12), guide (6),
disc holder (8), disc (5) and bellows (33) from the valve
body, unscrew the push rod from the disc holder to free
the guide. During this operation, take special care since,
owing to the weight of the guide, if it is not handled
correctly, it may damage the bellows. Use the drill of the
threaded part of bellows and with a suitable tool,
unscrew the bellows from the disc holder (bellows of
orifices up to “J” are welded to disc holder forming only
one single component). To disassemble disc from disc
holder, see Fig.-5.
In valve models 64GP y 64LP, depending on the size,
the push rod (12) and piston (46) can be one single
component or two. To disassemble the piston, remove
the elastic ring (47).
6.2.2 ASSEMBLY
For the assembly process, proceed in reverse order with
regard to the disassembly process, bearing in mind the
recommendations given in Section 6.1.2 and following:
In bellows-disc holders up to orifice “J”, which are of one
single component, take special care not to damage the
bellows when assembling the disc in the disc holder. In
the others, first assemble the disc in the disc holder first
and then screw the bellows to the disc holder.
Make sure that the screwed orifice of the bonnet
(vent) is uncovered. This is essential for the valve
to operate correctl
y
. See Fi
g
.-1.
6.3 DISASSEMBLY AND ASSEMBLY OF LEVER
CAP.
6.3.1 DISASSEMBLY
To disassemble the lever cap, position the lever (41) at
its lowest position, unscrew the nuts (25) and remove
the unit. See Fig.-7.
Before unscrewing stop-nuts (38), take note of the
distance “h”, between the upper nut and the top of the
stem (40). Therefore, when you reassemble the unit, you
will be sure that the lever is in the correct position.
Unscrew the nut (44), to release the lever (41) from the
shaft (43). Disassemble the packing gland (45) and
FIGURA - 7

10
remove the packing (42) from the casing. Pull on the
shaft, taking into account that the cam (37) will come
loose inside the cap.
6.3.2 ASSEMBLY
Once the parts have been checked and cleaned, begin
the assembly inserting the cam (37) inside the cap (39),
fit the shaft (43) in position by inserting the cam. Lightly
grease the emplacement of the packing slightly to
enable the sliding movement and insert sufficient
packing rings (42) so that once they are packed tight,
the packing gland (45) does not come into contact with
the cap and the shaft becomes blocked laterally. Once
the lever has been fitted (41), a certain amount of
resistance should be noticed when it is operated due to
the rubbing on the packing.
To assemble it on the valve, proceed in reverse order
with regard to the disassembly.
Under no circumstances must you reuse the packing
rings because, once pressed, it is very difficult to get
good tightness.

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CONVENTIONAL SAFETY VALVES MODELS 64GC AND 64LC
Nº PART NAME Nº PART NAME
1 BODY 16 ELASTIC RING
2 BONNET 17 PLUG
3 CAP 18 ELASTIC PIN
4 NOZZLE 20 LOCK STUD
5 DISC 21 GASKET
6 GUIDE 22 PLUG
7 ADJUSTING RING 23 STUDS
8 DISC HOLDER 24 NUT
9 STEM 25 SCREW
10 SPRING 26 GASKET
11 ADJUSTING SCREW 27 GASKET
12 PUSH ROD 28 GASKET
13 NUT 29 GASKET
14 LOCK SCREW
15 SPRING BUTTON

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BALANCED SAFETY VALVES (BELLOWS) MODELS 64GF AND 64LF
Nº PART NAME Nº PART NAME
1 BODY 16 ELASTIC RING
2 BONNET 17 PLUG
3 CAP 18 ELASTIC PIN
4 NOZZLE 20 LOCK STUD
5 DISC 21 GASKET
6 GUIDE 22 PLUG
7 ADJUSTING RING 23 STUDS
8 DISC HOLDER 24 NUT
9 STEM 25 SCREW
10 SPRING 26 GASKET
11 ADJUSTING SCREW 27 GASKET
12 PUSH ROD 28 GASKET
13 NUT 29 GASKET
14 LOCK SCREW 33 BELLOWS
15 SPRING BUTTON 34 GASKET

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BELLOWS-PISTON SAFETY VALVES MODELS 64GP AND 64LP
Nº PART NAME Nº PART NAME
1 BODY 17 PLUG
2 BONNET 18 ELASTIC PIN
3 CAP 20 LOCK STUD
4 NOZZLE 21 GASKET
5 DISC 22 PLUG
6 GUIDE 23 STUDS
7 ADJUSTING RING 24 NUT
8 DISC HOLDER 25 SCREW
9 STEM 26 GASKET
10 SPRING 27 GASKET
11 ADJUSTING SCREW 28 GASKET
12 PUSH ROD 29 GASKET
13 NUT 33 BELLOWS
14 LOCK SCREW 34 GASKET
15 SPRING BUTTON 46 PISTON
16 ELASTIC RING 47 LOCK WASHER

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6.4 RECONDITIONING OF CLOSING SURFACES.
The perfect tightness of the safety valve depends largely
on the condition of the closing surfaces, the contact
surfaces between the nozzle (4) and the disk (5).
If the safety valve has excessive leaks and you do not
have the means or experienced personnel, we
recommend that you send the valve to our installations,
where it will be checked thoroughly and the
corresponding repair certificate will be issued.
6.4.1 LAPPING OF CLOSING SURFACES
Owing to the fact that a perfect lapping of the nozzle and
the disk surfaces is essential for the valve in order to
avoid leaks, we recommend this operation to be carried
out with the appropriate means and by experienced
workers.
When the closing surface has been slightly damaged, a
lapping operation will suffice to return it to optimum
conditions. If the closing surface is weathered or too
marked by dirt, it must be resurfaced as finely as
possible in a lathe before it is lapped. (See Section 6.4.2
and 6.4.3)
To perform manual lapping, you must have a special
lapping plate made of alloy grade cast-iron or a flat,
polished surface (for example, a glass disk), together
with the different lapping products depending on the
finish required. See Table-2.
Table - 2
GRAIN DIMENSION
(m) FINISH TYPE PRODUCT
400 15 ÷ 21 MEDIUM IN SUSPENSION
SILICIUM CARBIDE
800 7,5 ÷ 10,5 THIN
1200 4 ÷ 6 MIRROR-LIKE
POLISHED
IN SUSPENSION
DIAMOND POWDER
In the standard process, after reconditioning the closing
surfaces, the lapping process is carried out with a
product for medium finish. When perfect flatness has
been obtained, lap with a fine-finish product on a
different surface. If operating conditions of the valve
requires more tightness, the final finish must be obtained
with a suspension diamond powder solution, leaving the
closing surface with a polished mirror-like finish.
The lapping process is carried out as follows:
Apply a fine layer of paste with the selected grain to the
lapping plate surface for the type of finish you wish to
obtain. Do not use the same surface for different types
of finishes and clean it well after each lapping process.
Place the piece perfectly flat on the lapping surface and,
pressing lightly and evenly, move it in the shape of an
eight until the desired finish is obtained. When a lapping
ring is used, the movement should be oscillating.
It is recommendable to remove the nozzle from the body
of the valve for correct lapping. If this is not possible or if
the surface is only slightly damaged, use the lapping
ring. Remember that excess paste on the lapping ring
can round off the edges of the nozzle lip.
The most important basic conditions for obtaining a good
final result in the lapping process are:
A) Flat surface for supportting the lapping plate.
B) Flat, cleaned and polished lapping surface.
C) Clean the lapping plate, the part that is to be
lapped and the lapping paste.
D) Choice of the type of grain of the lapping paste
for the required finish.
E) Even and smooth lapping movement (without
vibrations or sudden movements).
F) A worker specialised in lapping operation.
6.4.2 NOZZLE MACHINING
When the closing surface of the nozzle has marks with a
depth that cannot be removed with lapping, the surface
must be machined in a lathe, removing as little material
as possible.
To machine the closing surface, fasten the nozzle by its
flange, on a plate with three self-centring claws. Using a
comparator, make sure that the concentricity between
the internal surface of the nozzle and the external
surface of the flange is on a limit of 0,05 mm.
Machine the closing surface until the damaged area is
fully recovered, checking that as thinner is the finish as
lapping will be easier. Recompose nozzle lip until the
original width is obtained in the closing area, observing
the length between the closing surface and the face of
the flange that is in contact with the body of the valve.
Lap the closing area until a “mirror-like” finish is
obtained. See Section 6.4.1.
6.4.3 DISC MACHINING
To machine the closing area, fix the disk on the lathe
plate, avoiding excessive pressure so as not to produce
deformations. Centre the disk using a comparator,
making sure that the outside diameter and the closing
surface are aligned within a tolerance of 0,05 mm.
Machine the closing surface until the damaged area has
been fully recovered. Recompose the lip until the original
width is obtained in the closing area.
Lap the closing area until a “mirror-like” finish is
obtained. See Section 6.4.1.
7 – SET PRESSURE ADJUSTMENT AT THE
TEST BENCH
All tests and adjustments must be made by workers
who have been appropriately technical trained in the
operation of safety valves, as well as in the risks
involved in the tests.
Eyes and ears must be protected when the valve is
under pressure.
Also, when valve is under pressure, NEVER stand in
front of its outlet flange.

15
7.1 GASES AND VAPOURS
If a valve test bench is not available, the pressure
adjusting test may be performed using a pressurized
reservoir (bottle) with air or nitrogen, if possible, with a
good shock-absorbing “mattress” to avoid damaging the
closing areas of the valve when the popping is done.
The connection between the valve and the container
must be preferably direct through a cut-off valve. The
connection pipe must have a minimum inside diameter
of 8 mm.
It’s necessary to blow the connections and pipes of
the test bench before placing the valve to eliminate
any dirt that may have deposited there, which would
damage the closing areas.
The test can be performed in two different ways:
A) Increase the valve inlet pressure until there is a
continuous leak of fluid which can be identified
by a whistler or an unexpected noise.
B) Increasing the valve inlet pressure until it pops.
To get this, position the adjusting ring in contact
with the bell of the disc holder and then lower it
one or two notches. To perform this operation,
proceed as indicated in Section 7.4.
If the test is carried out correctly, the results of both
methods are practically identical.
Test (B) requires a larger container to prevent damage
to the closing surfaces and greater care must be taken
when fastening the valve.
7.2 LIQUIDS
This test is performed with clean water at ambient
temperature.
The test circuit must be purged and there must be no
accumulation of gas inside the test system. The use a
vacuum pump to depressurize the circuit before filling
with the test liquid is recommended.
An accumulation container is not normally necessary but
an air/water expansion tank is essential if an alternative
pump is used.
The set pressure will be identified when a continuous jet
of water flows vertically from the valve discharge flange.
7.3 TEMPERATURE AND BACKPRESSURE
CORRECTIONS
When the valve that is to be corrected on the test bench
at ambient temperature and atmospheric pressure is to
operate with temperatures of over 100 ºC and/or a
backpressure other than atmospheric, a correction by
temperature and backpressure must be made in the
adjustment of the set pressure in conventional valves.
For balanced valves (with bellows), only the correction
by temperature correction must be carried out since the
backpressure is compensated by the bellows.
The correction factor indicated in Table-3 must be
applied to the set pressure of the valves that are to work
with fluids at temperatures of over 100 ºC.
Table-3
OPERATING TEMPERATURE INCREASE OF THE SET
PRESSURE
Up to 100º C
FROM 101º C TO 250º C
FROM 251º C TO 500º C
Over 500º C
0 %
2 %
3 %
5 %
The above correction factor must be applied even
through the valve set pressure has been corrected to
compensate the effect of backpressure.
Therefore, the pressure at which the valve must be
tested in the bench, known as the Cold Differential Test
Pressure, is the inlet pressure at which the valve will
open on the test bench at ambient temperature and
atmospheric pressure.
To perform the exact calculation of the cold differential
test pressure, the pressure at which the valve in
question must open has to be taken into account,
together with the increase by temperatures over 100 ºC
and the backpressure that is different from atmospheric
pressure.

16
Examples of the calculation of the cold differential test
pressure with regard to backpressure and temperature:
A) DATA: Conventional valve (without bellows), set
pressure 20 bar, operating temperature 260ºC and
constant backpressure 1 bar, vapour service.
The cold differential test pressure adjustment:
20 bar – 1 bar = 19 bar
According to the table for temperature correction, a
correction factor of 3% must be applied (because
temperature is between 251ºC and 500ºC):
3 % of 19 bar = 0,57 bar (~ 0,6 bar)
Therefore, the cold differential test pressure to which the
valve must be adjusted in the bench will be:
19 bar + 0,6 bar = 19,6 bar
B) DATA: Balanced valve (with bellows), set pressure
50 bar, operating temperature 180ºC and constant
backpressure 1,5 bar, vapour service.
The cold differential test pressure adjustment:
As it is a balanced valve (with bellows), the
backpressure does not affect to the set pressure,
therefore, the backpressure is not substracted.
According to the table for temperature correction, a
corrector factor of 2% must be applied (because
temperature is between 101ºC and 250ºC):
2% of 50 bar = 1 bar
Therefore, the cold differential test pressure to which the
valve must be adjusted in the bench will be:
50 bar + 1 bar = 51 bar
The procedure is always the same and applicable in all
valve models.
7.4 ADJUSTING RING POSITION
For the pop of the valve in test benches where the flow
is low, the control ring must be adjusted as follows.
Once the tests have been completed, position the ring
as indicated in Table 1.
Do not carry out this operation when the valve is
under pressure, since it could lead to accidental
popping and cause injury to the worker who is
working on the valve.
Disassemble lock screw (14), turn the adjusting ring (7)
anticlockwise rotation until the bell comes into contact
with the disk holder (8). Then lower clockwise 1 or 2
notches to prevent contact. This operation can be
carried out using a screwdriver through the valve outlet
flange or through the locking screw hole.
Once the ring is in its position, fit the locking screw
paying attention that lock stud (20) is placed between
the adjusting ring notches. Once the lock screw is
tightened, make sure the ring is fixed so that it does not
turn but is free for self-alignment.
It may be necessary to readjust the blowdown once the
valve has been fitted since, depending on the product,
temperature, pressure and type of installation, it may
have been altered.
7.5 SET PRESSURE ADJUSTMENT
If valve opens at lower or higher pressure than set
pressure, the spring needs to be adjusted as shown
below:
A) Disassemble the cap (3) or (39) if the valve has
a lever.
B) Loosening the adjusting screw nut (13), the
adjusting screw will be freed (11). Turn it
clockwise to increase the set pressure and
anticlockwise to reduce it.
C) Once the set pressure has been reached,
tighten the nut and assemble the cap.
The tolerance ranges for adjusting the set pressure are
from ± 0,15 bar for pressures equal to or less than 4,8
bar and ± 3% for pressures over 4,8 bar.
Do not adjust the set pressure under any
circumstances when the valve is under pressure,
since the closing surfaces of the nozzle and the disk
may be damaged if sliding occurs.
8 – TIGHTNESS TEST
Tightness tests of the valves that work with gases and
vapours or liquids must be performed after the set
pressure has been adjusted and using the same fluid.
With valves with a set pressure of over 3,5 bar, the test
pressure shall be set to 90% of the set pressure. With
valves without set pressure equal or less than 3,5 bar,
the test pressure shall be 0,35 bar below the set
pressure.
With this test, particular care must be taken since
there is a risk of unexpected popping because of the
fact that work is being carried out under conditions
that are very near to the set pressure and there may
be a hazard for the worker who is working with the
valve.
8.1 TIGHTNESS TEST WITH AIR
Figure 9 shows the methods to be used for this test on
files that are to work with gases or vapours.

17
RECIPIENTE
ACUMULADOR DE AIRE
Brida de pruebas
Tubo de Ø 6 x 8 mm
12,7 mm
The valve outlet must be covered with a flange whose
only outlet hole is a pipe with an interior diameter of 6
mm and a wall of 1 mm, curved at 90º whose end is
submerged 12,7 mm in a container with water.
With tightness test pressure adjusted as indicated in
Section 8 and after maintaining it for 1 minute with a size
of DN-50 (2”) or less; 2 minutes for valves with a size of
DN-80 and DN-100 (3” and 4”) and 5 minutes for valves
with a size of DN-150 (6”) or higher; count the bubbles
that appear during a period of 1 minute.
The test is passed as long as the values indicated in
table 4 are not exceded, as recommended by the API-
RP 527 Standard.
VALVE SET
PRESSURE
Barg. AT 15,6º C
ADMISSIBLE BUBBLE LEAKS
PER MINUTE
ORIFICES “C”
TO “F”
ORIFICES “G”
TO “T”
DIAMETER
≤18mm
DIAMETER>18
mm
FROM 1 TO 69 40 20
TO 103 60 30
TO 130 80 40
TO 172 100 50
TO 207 100 60
TO 276 100 80
TO 385 100 100
TO 414 100 100
Table – 4
8.2 TIGHTNESS TEST WITH WATER
Before adjusting tightness test pressure, fill the interior
of the body with water. When it has stabilized and water
has stopped running through the valve outlet flange,
adjust the tightness test pressure as indicated in Section
8.
When the test pressure has been adjusted, collect the
drops that fall from the outlet nozzle during the period of
one minute in a container. The amount collected shall
not exceed 10 cm³/h for every 25 mm nominal diameter
of the valve (API-RP 527).
8.3 EXCESSIVE LEAK
If the tightness test has been performed correctly and it
gives a result of excessive leakage, remove the valve to
check that there is no dirt or foreign bodies between the
nozzle and the disk.
If the leakage is due to dirt from the contamination of the
test fluid, simply clean the closing surface with cellulose
paper or any other non-abrasive medium soaked in
solvent. However, if the leakage is due to marks on the
closing surface and in accordance with the depth of the
marks, relap or recover the surfaces as indicated in
Section 6.4.
9 – TEST PRESSURE GAUGES
The pressure must be measured using pressure gauges
that have been regularly checked and calibrated, and
whose calibration is certified accordingly, as ANSI B
40.1 Grade A Standard indicates.
The pressure gauge must be selected in accordance
with the test pressure, which must be between 25% and
75% of the scale bottom, where an error no greater than
1% of the measurement field is acceptable.
10 - ATEX MARKING
The safety valves supplied for installation in potentially
explosive atmospheres are compliant with Directive
2014/34/UE (ATEX). They are classified within Group II,
Category 2, and marked with a specifications plate that
reads as follows:
II 2 G c TX
10.1 SAFETY RECOMMENDATIONS
To avoid the risk of ignition, bear in mind the following
points:
a) Prevent dust from accumulating on the valve casing.
b) It is absolutely important to keep the protective
painting on the casing in good condition, owing to the
fact that, if there is any friction or shock, the oxide would
act as a high risk of ignition.
TX TEMPERATURES RANGE
T
(
ºC
)
T1 300º<T≤450º
T2 200º<T≤300º
T3 135º<T≤200º
T4 100º<T≤135º
T5 85º<T≤100º
T6 T≤85º
FIGURA - 8

18
c) It is essential to make sure that the valve is not
insulated from the earth connection of the installation,
since the different layers of paint resulting from its
maintenance create a plastic insulation on the valve that
favours the accumulation of static electricity which, if not
eliminated correctly, can produce radiant discharges that
could lead to ignition.
d) When the valve has to be fitted to or removed from
the installation, use tools that do not produce sparks
from friction.

19
FAILURE POSSIBLE CAUSE SOLUTION
Excessive leak
Dirt between nozzle and disc.
Perform one or two pops and check. If there is a leak
again, internal components should be disassembled and
cleaned.
Marked or scratched closing
surfaces. Disassemble valve and lap nozzle and disc.
Use the valve with a fluid
different to the one it was
designed for.
Lap nozzle and disc with the thinnest polish finish.
(Typical behaviour of valves designed to be used with
liquids and really used with gases).
Valve isn’t installed in upright
position.
Modify installation. Valves should be always installed in
upright position.
Set pressure is too close to
operating pressure (When
operating pressure is more than
90 % of set pressure, leaks
could be produced).
Increase set pressure to get a 10 % minimum
differential. If that’s not possible, you should modify
closing surface (to provide “stellite”, lap with an
extremely thin grade, etc.)
Discharge of the valve
at a different pressure
it’s been adjusted
Built-up backpressure.
In conventional valves, you should check that the
release manifold has the same size or greater than the
outlet connection of the safety valve and / or there’s no
obstruction. Ideally, install balanced valves (with
bellows).
Backpressure different to early
specified.
Valve should be adjusted considering the correct
backpressure (conventional valves).
Loose adjusting screw nut. Tighten nut once valve has been adjusted again.
Misalignment of the internal
components of the valve. Perform 2 or 3 pops so that valve could self-align.
Chattering (fast and
cyclic opening and
closing of the valve.)
Excessive turbulences at the
valve inlet. Modify the valve installation.
Adjusting ring (blow-down)
incorrectly positioned.
Check that the adjusting ring is correctly positioned. If
not, adjust it according to Section 5.2.
Oversized valve. Recalculate and install correct valve.
Excessive pressure drop at the
valve inlet.
Increase blow-down positioning the adjusting ring as
nearest as you can to disc holder bell.
Accumulation is too small. Increase the distance between the adjusting ring and the
disc holder.

20
NOTES
For valves with BW connections applied as indicated in the document except that where indicated inlet or outlet flange
should be understood as BW inlet or outlet connection respectivel
y
.