Type 99

type 161AYW monitoring pilot (also representative of Type 627-109)

working

monitor pilot

pilot supply line

loading pressure

optional pilot supply regulator

upstream pressure

20A1389-A

B2484

distribution pressure control line

intermediate pressure control line

intermediate pressure

working

working

 

regulator

 

monitor

 

 

 

regulator

optional

distribution

 

pilot supply

 

regulator

pressure

pilot supply piping for working regulator when pilot is required to be supplied from upstream pressure

Figure 4.  Working Monitor Installation

The monitoring pilot should be upstream of the working monitor regulator. This enables a closer setpoint between the working regulator and the monitoring pilot. Special Types 161AYW and 627-109 monitoring pilots with quick-bleed operation have been designed to give faster response to abnormal downstream conditions. Table 4 gives the spread between normal distribution pressure and the minimum pressure at which the working monitor regulator can be set to take over if the working regulator fails open.

upstream regulator (requires o-ring stem seal)

10A1388-A

A2504

optional pilot supply regulator

Flexible arrangement that permits wide-open monitor to be either upstream or downstream

Wide-Open Monitor

The control line of the upstream regulator is connected downstream of the second regulator (Figure 5), so that during normal operation the monitoring regulator is standing wide open with the reduction to distribution pressure being taken across the working regulator. Only in case of open failure of the working regulator does the wide-open monitoring regulator take control at its slightly higher setting.

The upstream regulator must have an O-ring seal on the valve carrier assembly. This seals off the leak path that otherwise would let line pressure ahead of the working regulator inlet try to close the wide-open monitoring regulator.

upstream

 

regulator

 

(requires o-ring

Working

stem seal)

regulator

10A1386-A

A2503

optional pilot supply regulator

Flexible arrangement that permits wide-open monitor to be either upstream or downstream

Figure 5.  Typical Wide-Open Monitor Installations

5