Sheet 7457-1 Page 2
Installation. Install 7457 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 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.
When installing 7457 Regulators, keep heated oil line as close as possible to the 7457 pilot, to minimize cooling of oil in the dead- ended oil impulse line.
‡ 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
290
600
900
1700
2800
4880
9970
1 ¼ "
1 ½ "
2 ½ "
recommended outlet
1"
2"
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.
burner oil supply line
make as short as possible and trace if required
¼ " oil (differential) control pipe Install shutoff valve in this line, close to takeoff point.
differential pressure adjustment – remove cap and turn screw to adjust differential between steam and oil pressure
recommended means of ensuring warm oil control line
¼ " oil control pipe – connect to oil supply line to burner
pilot
at least 20 pipe diameters (D 2 ) to first run or secondary pressure relief valve or control valve
at least 10 pipe diameters (D 1 ) straight run, full size
see alternate view for a means of ensuring warm oil control line
gate valve
D 2
D 1
4 pipe diameters (D 2 ) min.
strainer
1⁄8 " NPT for connection to funnel and drain for tell-tale of steam or oil diaphragm failure in pilot Do Not Plug 1⁄8 " NPT
drip and trap
regulator
drip and trap ahead of rise in piping or secondary pressure relief valve or control valve
¼ " control pipe--pitch away from pilot, avoid water pockets
preferred transistion--15° max. total included angle
STARTING UP AND SETTING.
OPERATING PRINCIPLE (REF: DIMENSION AND INSTALLATION DWGS.)
1. Remove cap from top of pilot spring chamber. Close pilot by releasing compres- sion on adjusting spring and by having the valve closed in the oil control line. Caution: Do not remove adjusting screw or entirely loosen lock nut.
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 adjusting spring. 2. When steam is turned on, it flows through pilot, to the No. 8B tee. Bleedport No. 4A restricts flow, builds pressure under the diaphragm and opens main valve. Restriction No. 5A steadies the operation of the regulator. 3. Steam 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 pressure. In turn, main valve takes a position established by the loading pressure where just enough steam flows to maintain the set delivery/ differential pressure. 4. Base bypass line is a pressure equalizing connection between diaphragm case and downstream side of main valve. It provides a means of ensuring a quick response to pressure changes, that may not be possible with normal stem clear- ance.
2. Open valve in steam delivery control line.
3. Crack inlet stop valve. Blow down strainer. Caution: Never open the control valve without positive indication the high side is clear of condensate.
4. Open inlet stop valve and slowly open the valve in the oil control line.
5. Set desired steam to oil differential pressure by compressing the pilot adjusting spring. Compressing the spring increases differential.
6. Allow the trapped air in the pilot to bleed out around the threads of the adjusting screw before replacing the cap on top of the pilot spring chamber.
Maintenance and trouble-shooting. For details see instructions supplied with each regulator.
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.
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