Sapag Safety Valves Series 8400/8500/8490/8590
Installation and Maintenance Instructions
Emerson reserves the right to change the contents without notice
page 5
Outlet Piping
Outlet piping should be simple and direct. Where possible, for non-hazardous fluids, a short
discharge pipe or vertical riser connected through a long radius elbow venting directly to
atmosphere is recommended. Such discharge piping should be at least the same size as the valve
outlet.
All discharge piping should be run as direct as is practicable to the point of final release for
disposal. Valve effluent must discharge to a safe disposal area.
Where discharge piping is long, due consideration shall be given to the use of long radius elbows,
and the reduction of excessive line strains through the use of expansion joints and proper means
of support to minimize line sway and vibration under operating conditions. Adequate drainage
is required to prevent corrosive media from collecting in the discharge side of the pressure relief
valve. When required, low point drains shall be provided in the discharge pipe. Particular care
must be observed to ensure that the drains are directed or piped to a safe disposal area.
In installations where the pressure relief valve discharges into a closed system, care must be taken
to ensure that built up and superimposed back pressure has been properly calculated, specified,
and accounted for when sizing and selecting the valve.
Where built up back pressure is expected to exceed 10% of set pressure or if superimposed back
pressure is variable, a bellows valve is required.
Discharge pipe
Low point
drain
Long radius
elbow
Free
support
Top of vessel
Rounded
approach
Short as
possible
Lid
Figure 3
Recommended installation-
discharging to atmosphere
4. Hydrostatic Pressure Tests
Hydrostatic Test of Vessel or System
When a pressure vessel or system is to be hydrostatically tested, it is recommended that the
pressure relief valve be removed and a blank flange be installed in its place. This practice
precludes the possibility of any damage to the pressure relief valve. Bent spindles and damaged
valve seats are problems that can be caused by improper hydrostatic test procedures.
Blank flanges must be removed and the pressure relief valve reinstalled before the vessel is placed
in service.
When the hydrostatic test must be performed with the valve in place, a test gag may be used.
Sapag Series 8000 are provided with test gags as standard. In the case of the Type C cap with
lifting lever, the lifting lever assembly must be replaced with a hydrostatic test cap and test
rod prior to hydrostatic testing. When test rods are used, care must be exercised to prevent
overtightening that could damage the valve spindle and valve seats. A test rod which is hand tight
will generally provide sufficient force to hold the valve closed.
After the hydrostatic test, the test rod (gag) must be removed and replaced by either a cap plug or
a cap not fitted with a test rod.
Hydrostatic Test of Outlet System
When a hydrostatic test must be conducted on the outlet piping system, with the valve in place,
special consideration must be given not to exceed the design pressure limits of the downstream
side of the pressure relief valve. The outlet side of a pressure relief valve is known as the
secondary pressure zone. This zone is normally designed to a lower pressure rating than the
inlet and frequently is designed to a lower pressure rating than the outlet flange. This is
particularly true in the case of balanced bellows designs and in the larger valve sizes.
Consult Sapag products specifications for the back pressure design limits of the Series 8000
valves.
5. Setting, Testing and Adjustments
New Valves
Each Sapag pressure relief valve is carefully set and tested at the factory prior to shipment.
However, it is good practice to inspect the valve prior to installation.
This inspection determines any damage which may have occurred due to rough handling in transit
or storage and initiates appropriate service records.
Reconditioned Valves
Valves which have not been in service for extended periods due to plant shutdown or long term
storage, or valves which have been repaired or reconditioned, should also be tested before being
put into operation.
Valves Removed From Service
Valves being removed from service should be tested on a shop test bench before being
disassembled to determine the set pressure and seat tightness. This is an important phase of
the maintenance routine and the test results should be recorded for review and determination of
necessary corrective action.
The “as received from service” condition of a pressure relief valve is a most useful tool in
establishing the proper time interval between inspections.
CAUTION: Improper testing may
cause valve damage and seat
leakage.
