Remote Sensing; Freeze Protection - Baker Hughes Consolidated 4900 Series Instruction Manual

XI. Recommended Installation Practices (Cont.)
A continual oscillation of the discharge piping (wind
loads) may induce stress distortion in the valve body.
The resultant movement of the valve's internal parts
may cause leakage.
The pressure drop (P.D.) between the source
of pressure in the protected equipment and the
pressure relief valve inlet is not to exceed 3% of the
valve set pressure.
Where possible, use properly supported drainage
piping to prevent the collection of water or corrosive
liquid in the valve body.
In every case, the nominal discharge pipe size
should be at least as large as the nominal size of the
POSRV outlet flange In the case of long discharge
piping, the nominal discharge pipe size must
sometimes be much larger.
D. Remote Sensing
If the pressure drop between the source of pressure
in the equipment to be protected and the pressure
at the relief valve inlet exceeds 3%, the sensing line
to the pilot valve should be connected directly to
the equipment being protected. For remote sensing,
.375" (9.53 mm) diameter tubing is adequate for
distances up to 10 feet (3.048 m). If distance is
longer than 10 feet (3.048 m), please contact
Baker Hughes Application Engineering.
ATTENTION!
Change in elevation between relief valve and
source of sensing line may cause set pressure
E. Freeze Protection
Type of applications:
• Applications where the process media, in the
liquid state, has a freezing point between the
ambient temperature limits of the local region.
• Steam service applications where the pilot
operated valve is exposed to the climate, extreme
cold ambient temperatures.
Example: the condensed steam in the pilot and
tubing may become frozen
• Applications where the process media is
temperature sensitive to thick formations.
Example: hydrocarbon applications where the
possibility of hydrate formation may occur.
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changes.
Reasons for freeze protection:
• If the pilot sensing line becomes clogged or
frozen, then system pressure can be isolated
from the pilot valve. This will not allow the pilot
to detect system pressure, open and relieve the
overpressure situation.
Recommendations for insulating and heat tracing
pilot operated safety relief valve:
Types of freeze protection:
• Insulation by fiber glass blankets or wrap.
• Heat tracing with electrical heat tape.
• Radiant heat sources, such as a heat lamp.
For applications where heat tracing or radiant
heaters are used, the temperature should be limited
to approximately 200.F (93.3°C) so that the
elastomers are not damaged. Higher temperatures
may be allowed upon review of the application.
• Valve illustrations showing acceptable locations
for insulation are shown in Figure 11.
INSULATION NOT
REQUIRED FOR
BONNET AND CAP
ACCESSORIES
(I.E. FILTERS)
PILOT VALVE
BASE
MAIN VALVE
BASE
Figure 11: Valve Insulation
Consolidated 4900 MPV Series POSRV Manual
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