SAPAG
Installation & Maintenance Instructions
Change-Over valve
Delivery conditions
The
Change-Over valve
flange rating.
The discs are tested with air under water at 1.1 time the maximum working pressure.
The
Change-Over valve
Our
Change-Over valve
or in accordance with our standard Quality Plan. Packing and protection caps shall remain in
position up to the very last moment prior to the assembly of the
order to protect end connections of any damage
Storage
When the change over valves are to be stored some time before their installation, the storage shall
be made in the original crates of delivery with a watertight protection and/or with desiccant bags.
Storage shall be done above ground, indoor in a dry and clean place.
If the storage period is above 6 months, the desiccant bags (if any) shall be replaced at this date.
Selection
The materials of change over valves are selected in taking into account the working temperature,
the fluid characteristics and any other relevant data that is given at quotation stage.
Before to install a change over valve, the compatibility of materials as well as pressure/temperature
limitations that are mentioned on the tag plate are suitable to the fluid and process operating
conditions.
s are tested in factory at 1.5 time the maximum pressure of the connecting
s are delivered ready to be assembled.
s are delivered with protections in accordance with customer requirements,
Change-Over valve
in the piping in
Limitations
The change over valve has been design to install two safety relief valves in parallel. It can not be
used for other purposes than to isolate safety relief valves.
Operation
The change over valve is a globe valve with one inlet and two outlets. It is used to fit two safety
relief valves in parallel; if the change over valve is closed on one end, one safety relief valve is in
operation and the other one is isolated, as safe spare; also, if the change over valve is set in the
intermediary position, the two safety relief valves are in operation simultaneously. While one safety
relief valve is isolated, regular maintenance can be carried out.
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The change over valve is manually operated thanks to a wheel. An index located on the stem states
which side is open. With no index, the turning clockwise of the hand-wheel is making the opposite
side of the hand-wheel to be closed; turning the hand-wheel anti-clockwise is closing the side of
the change over which is near the hand-wheel.
When a safety relief valve is isolated for maintenance purposes, it is extremely important to check
that the outlet of the change over valve on which it is fitted is well depressurised before proceeding
to its disassembly. In order to depressurised the relevant outlet, the drain plug may be used.
The design of the change over valve is such that there is always at least one safety relief valve in
operation in order to insure safety of the system.
Emerson reserves the right to change the contents without notice SAPDR-0009-EN-1307
Installation & Maintenance Instructions
Change-Over valve
Installation
1. The
Change-Over valve
2. The
Change-Over valve
3. Generally the
some cases the inlet size can be one or two NPS greater than the outlets, the two outlets being
always of the same size.
4. The inlet flange (upstream) is generally horizontal; other mountings are possible, consult the
factory.
5. Check if the inlet flange and the two downstream flanges are compatible with respectively the
upstream flange and the inlet flanges of the safety valves. Check the shape and cleanness of
seating surfaces, gaskets, bolting.
6. The
Change-Over valve
7. Once the
8. Check if the wheel is at a location such that the access is free and the operation possible.
9. The two connected safety valves must be mounted vertically, spring up side, in parallel on the
two
Change-Over valve
10. It is highly recommended to fit a device allowing the drainage of each of the branches of the
Change-Over valve
is located on each branch; it is recommended to fit a drain valve and also of a pressure gage.
11. Start up the unit only when the correct assembly and leak test of the
the attached safety valves has been successfully completed.
12. Check it the gland nuts are securely fastened before operation (the fastening can be released
when starting up or in service).
13. If the
Change-Over valve
Change-Over valve
Change-Over valve
is to be installed upstream the connected safety valves.
has one inlet (upstream) and two outlets (downstream) in parallel.
has one inlet and two outlets of identical size and rating; in
is to fitted on the upstream flange, its shaft shall be horizontal.
is in place, its two outlet flanges must be absolutely horizontal.
outlet flanges.
when they are isolated; a drain hole (NPT thread) plugged with a steel plug,
Change-Over valve
is insulated, the access to the packing gland must remain free.
and
Operation
For safety reasons it is important to follow the precautions as listed below before initiating any
work on a
1. The
2. Operating a
3. A
4. When the
5. Operating the
6. Before the initial start up it is recommended to proceed with a pneumatical test at low pressure
7. Once this test has been successfully completed then the
8. According to local regulation there are two ways to operate the
9.
Change-Over valve
Change-Over valve
Change-Over valve
known procedure, and on a definite schedule.
Change-Over valve
its principle of operation.
Change-Over valve
duly locked.
Change-Over valve
should improve the valve operation and the plant safety.
to check the tightness; to achieve this test, open the
reference to the index on the shaft and slowly build up the pressure. Check for eventual leaks
at the inlet connection and at the safety valves connections, and at the packing gland.
operation.
• Either one branch in operation, one branch in back up;
• Either both branches in simultaneous operation.
• The type of operation should be clearly stated on the site procedure for operation and
maintenance.
Operation one branch in service, one in back up:
• One single safety valve (1) provides the site protection.
• The second safety valve (2) is a back-up.
• On a scheduled basis, or in case of failure (leakage of safety valve), the Change-Over valve is
operated to isolate one of the two safety valves.
• Check through the drain hole that the isolated branch has zero pressure.
• The damaged safety valve can be removed and repaired.
• During that period when one of the valve is removed and maintained it is recommended to fit
a blind flange onto the branch from where the safety valve is removed.
• Once the repaired valve is in place again, proceed if necessary with a pneumatic test (leak
test) of the isolated branch on which the safety valve has been mounted through the drain
hole.
• The Change-Over valve can then be operated to isolate the safety valve in service and put
back into service the repaired safety valve.
• Lock the wheel of the Change-Over valve when procedure is completed.
:
is a safety device, essential for the plant safety.
shall be made only by authorised personnel, according to a
is a speciality valve, requiring from the operator a perfect knowledge of
is not be operated, the wheel of the
on a regular schedule (recommended: once every six months)
Change-Over valve
Change-Over valve
Change-Over valve
to mid-way position in
can be put into
Change-Over valve
shall be
:
Emerson reserves the right to change the contents without notice page 2
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