Sheet 7447-1 Page 2
4 pipe diameters downstream of the point where outlet piping was increased in size. Avoid tapping the control line into elbows, tees, or other points of turbulence.
Installation. Install 7447 Regulators in a straight run of horizontal pipe, with a steam strainer upstream of the regulator. Install traps in the steam line upstream and downstream of the regulator. Size the steam line downstream of the regulator per Table 2. When installing the ¼ " control line from the pilot to the downstream steam line, pitch it away from the pilot and avoid water pockets. The control line should enter the side or top of the pipe at least
‡ Indicates pressure below which no further increase in capacity can be obtained .
Table 2 Regulator outlet pipe sizes
flow rate of saturated steam, lb/hr recommended outlet
290
600
900
1700
2800
4880
9970
1"
1 ¼ "
1 ½ "
2"
2 ½ "
3"
4"
pipe size
Pipe size recommendations are based on 2 psi pressure drop per 100 equivalent feet of pipe for 100 psi saturated steam.
pilot
at least 20 pipe diameters (D 2 ) to first turn or secondary pressure relief valve or control valve
at least 10 pipe diameters (D 1 )
straight run, full size
¼ " control pipe--pitch away from pilot, avoid water pockets
gate valve
D 2
4 pipe diameters
strainer
preferred transistion--15° max. total included angle (D 2 ) min.
regulator
drip and trap ahead of rise in piping or secondary pressure relief valve or control valve
drip and trap
OPERATING PRINCIPLE (Ref: Dimensions and Installation Dwgs.)
Insulation. Insulation can be applied to the upper portion (globe and flanges) of main valve. Do not insulate diaphragm chamber, or any part of pilot. STARTING UP AND SETTING.
1. Regulator is operated by initial steam pressure. It is normally closed, being held so by initial pressure on disc and by an internal main spring. Pilot is opened by compressing its adjust- ing spring. 2. When steam is turned on, it flows through the pilot, to the No. 8B tee. Bleedport No. 4A restricts flow, builds pressure un- der the diaphragm and opens main valve. Restriction No. 5A steadies the operation of the regulator. 3. Delivery pressure feeds back through control pipe to the pilot diaphragm. As this pressure approaches a balance with the thrust of the adjusting spring, pilot throttles the loading pres- sure. In turn, main valve takes a position established by the loading pressure where just enough steam flows to maintain the set delivery pressure. 4. Base bypass line is a pressure equalizing connection be- tween diaphragm case and downstream side of main valve. It provides a means of insuring a quick response to pressure changes, that may not be possible with normal stem clearance.
1. Close pilot by releasing compression on adjusting spring.
2. Open ¼ " control pipe valve.
3. Crack inlet stop valve. Blow down strainer. Caution: Never open a reducing valve without positive indication the high side is clear of condensate. 4. Open inlet stop valve and gradually compress adjusting spring until the valve opens and takes control at desired pressure. Maintenance and trouble-shooting. For details see instructions supplied with each regulator.
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