Type 99
downstream control line
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| relief |
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| valve |
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| cap |
E |
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| H |
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| D |
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| J |
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| F |
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| yoke |
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| cap |
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| yoke | C |
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| yoke | relay |
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| adaptor |
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| valve |
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| inlet pressure |
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SSURE | A | tubing connection |
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RESSURE |
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inlet pressurePRESSURE |
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ERIC PRESSURE |
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outlet pressure |
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loading pressure |
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atmospheric pressure |
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A2505 |
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Figure 3. Schematic of Type 99 Regulator with Type 61HP (Extra High Pressure) Pilot
through the relief valve body (J) (Figure 4). Since loading pressure needs to exceed outlet pressure only moderately to stroke the main valve fully open, a continued increase in loading pressure differential extends the main diaphragm (E) and the pusher post assembly (K) far enough to separate the bleed valve (D) and the bleed orifice (H). This permits quick dumping of excess loading pressure into the downstream system.
With a decrease in loading pressure on top of the main diaphragm (E), the main spring (B) exerts an upward force on the diaphragm rod connected to the main diaphragm (E), pulling it upward. This moves the main valve toward its seat, decreasing flow to the downstream system.
Diaphragm (G) in the pilot valve acts as a sealing member for the loading chamber and as a balancing member to diaphragm (F). These two diaphragms are connected by a yoke so any pressure change in the pilot chamber has little effect on the position of the pilot valve. Therefore, the active diaphragm in the pilot is
(F)and the pressure on the top side of this diaphragm opposes the force of the pilot control spring (A).
Monitoring regulators serve as overpressure protection devices to limit system pressure in the event of open failure of a working regulator feeding the system. Two methods of using Type 99 regulators in monitoring systems are as follows:
Working Monitor
On a working monitor installation (Figure 4), the control line of the monitoring pilot is connected downstream of the working regulator. During normal operation, distribution pressure causes the monitoring pilot to stand wide open. Full pilot supply pressure enters the working monitor pilot and permits the working monitor regulator to control at its intermediate pressure setting.
Open failure of the working regulator increases distribution pressure as the working regulator goes
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