S251C Instruction Manual

Type S251C

Fisher Controls

Instruction Manual

Type S251C Pilot-Operated Regulators

March 1978

Form 5101

WARNING Fisher regulators must be installed, operated, and maintained in accordance with federal, state, and local codes, rules and regulations, and Fisher instructions.

If the regulators vents gas or a leak develops in the system, service to the unit may be required.

Failure to correct the trouble could result in a hazardous condition.

Call a gas service technician to service the unit.

Only a qualified person must install or service the regulator.

INTRODUCTION Figure 1. Type S251C

This instruction manual provides instructions and parts lists for the Type S251C regulator, including the main regulator and pilot.

Description The Type S251C is an accurate, pilot-operated pressurereducing regulator, intended for general gas pressure reduction service such as domestic and small commercial applications using pressure-factor measurement (fixedfactor billing).

Specifications Table 1 lists the specifications for Type S251C constructions. The following information is stamped on the regulator at the factory: orifice (seat ring) diameter, maximum inlet pressure, outlet pressure setting, and pressure factor.

ŠFisher Controls Comany 1978

INSTALLATION WARNING Personal injury or system damage may result if this regulator is installed, without appropriate overpressure protection, where service conditions could exceed the limits given on the regulator nameplate. Regulator installations should be adequately protected from physical damage.

CAUTION Like most regulators, the Type S251C regulator has an outlet pressure rating lower than its inlet pressure rating. If actual inlet pressure can exceed the outlet pressure rating, outlet overpressure protection is necessary. However, overpressuring any portion of a Type S251C regulator beyond the limits in table 2 may cause

D400015X012

Scope

Type S251C

Table 1. Specifications MINIMUM PRESSURE DROP REQUIRED FOR FULL STROKE

2 psi (0.14 bar differential)

SEAT RING DIAMETERS

See table 2

25 psig (1.7 bar)

TEMPERATURE CAPABILITIES

-20° to +170°F (-29° to 77°C)

OUTLET PRESSURE RANGE

2 to 20 psig (0.14 to 1.4 bar)

Internal

OUTLET PRESSURE ACCURACY

±1 percent of absolute outlet pressure setting (psia or bar absolute) when inlet pressure is held within allowable variations shown in table 2

DOWNSTREAM PRESSURE REGISTRATION APPROXIMATE WEIGHT

4.5 pounds (2 kg)

AVAILABLE CONFIGURATIONS

Pilot-operated regulator with angle-style main regulator body

BODY SIZES AND END CONNECTION STYLE

Sizes: n 34-inch inlet and 1-inch outlet or n 1-inch inlet and outlet

MAXIMUM ALLOWABLE INLET PRESSURES

See table 2

MAXIMUM EMERGENCY OUTLET PRESSURE

STARTUP leakage, damage to regulator parts, or personal injury due to bursting of pressure-containing parts.

Some type of external overpressure protection should be provided if inlet pressure will be high enough to damage downstream equipment.

Common methods of external overpressure protection include relief valves, monitoring regulators, shutoff devices, and series regulation.

If the regulator is exposed to an overpressure condition, it should be inspected for any damage that may have occurred. Regulator operation below these limits does not preclude the possibility of damage from external sources or from debris in the pipeline.

Before installing the regulator, check for damage which might have occurred in shipment. Also check for dirt or foreign matter which may have accumulated in the regulator body or in the pipeline. Apply pipe compound to the male threads of the pipeline and install the regulator so that flow is in the direction of the arrow cast on the body.

Do not install the regulator in a location where there can be excessive water accumulation, such as directly beneath a down spout.

2

CAUTION Pilot supply pressure must be introduced into the regulator before introduction of any downstream pressure, or internal damage may occur due to reverse pressurization of the pilot and main valve components.

Pressure gauges should always be used to monitor downstream pressure during startup.

Procedures used in putting this regulator into operation must be planned accordingly if the downstream system is pressurized by another regulator or by a manual bypass.

Note For proper operation, pilot supply pressure must exceed control pressure by the minimum differential pressure of 2 psi.

Use the following procedure: 1. Slowly open the upstream shutoff valve.

2. Slowly open the downstream shutoff valve. If the downstream system had already been pressurized by another regulator or manual bypass valve, observe regulator for anticipated performance.

3. Check all connections for leaks.

Type S251C Table 2. Allowable Inlet Pressure Variation for Maintaining Outlet Pressure within ±1 Percent of Setting (Accuracy Applies to Absolute Outlet Pressure, PSIA) MAXIMUM ALLOWABLE INLET PRESSURE

SEAT RING DIAMETER

ALLOWABLE INLET PRESSURE RANGE FOR MAINTAINING OUTLET PRESSURE WITHIN ±1 PERCENT OF SETTING* 2 Psig (0.14 Bar) 5 Psig (0.34 Bar) 10 Psig (0.69 Bar) 15 Psig (1.0 Bar) 20 Psig (1.4 Bar) Outlet Pressure Outlet Pressure Outlet Pressure Outlet Pressure Outlet Pressure Setting+ Setting+ Setting+ Setting+ Setting+

Psig

Bar

Inches

mm

Psig

Bar

Psig

Bar

125

8.6

1/8

3.2

P1±40++

P1±2.8++

P1±40++

P1±2.8++

100

6.9

3/16

4.8

P1±30++

P1±2.1++

60

4.1

1/4

6.4

5 to 60

0.34 to 4.1 10 to 60 0.69 to 4.1 15 to 60

1.0 to 4.1

20 to 60

1.4 to 4.1

25 to 60

1.7 to 4.1

2.1

3/8

9.5

5 to 30

0.34 to 2.1 10 to 30 0.69 to 2.1 15 to 30

1.0 to 2.1

20 to 30

1.4 to 2.1

25 to 30

1.7 to 2.1

30

Psig

Bar

Psig

Psig

Bar

10 to 100 0.69 to 6.9 15 to 100 1.0 to 6.9 20 to 100 1.4 to 6.9 25 to 100 1.7 to 6.9

*

Accuracy applies to absolute outlet pressure (psi or bar absolute).

+

For best perfromance, outlet pressure setting should be made using an inlet pressure that is midway between the highest and lowest expected inlet pressure.

++

Bar

15 to 125 1.0 to 8.6 20 to 125 1.4 to 8.6 25 to 125 1.7 to 8.6

P1 is the actual inlet pressure at which the outlet pressure setting is made. Variations must not be higher than the maximum allowable inlet pressure for the port diameter involved nor lower than the outlet pressure setting plus the 2 psi (0.1 bar differential) minimum pressure drop.

Adjustment To increase the outlet pressure setting of the regulator, the adjusting screw of the pilot (key 10, figure 4) must be turned clockwise. This requires loosening the locknut (key 11). To reduce the outlet pressure setting, turn the adjusting screw counterclockwise. Retighten the locknut.

Do not remove the locknut or adjust the spring to produce an outlet pressure setting outside the range of 2 to 20 psig. A pressure gauge should always be used to monitor downstream pressure while adjustments are being made.

SHUTDOWN

loading pressure from the pilot overcomes the spring force, and the main regulator valve disc moves farther open, to supply the required flow.

When downstream pressure increases due to lowered demand, greater pressure is registered beneath the pilot and main diaphragms. The pilot starts to close, and the excess loading pressure bleeds off to downstream through the pilot body. With the lower loading pressure, the spring can move the main regulator disc closer to the seat ring.

Since a main regulator diaphragm differential pressure of only about 1/2 psi is sufficient to stroke the main regulator

Installation arrangements may vary, but in any installation it is important that the valves be opened or closed slowly and that the outlet pressure be vented before venting inlet pressure to prevent damage caused by reverse pressurization of the pilot or main valve. The steps below apply to the typical installation as indicated.

1. Slowly close the upstream shutoff valve.

2. Inlet pressure will automatically be released downstream as the regulator opens in response to the lowered pressure on the diaphragm.

PRINCIPLE OF OPERATION The S251C has spring-to-close contruction which permits "two path control" where changes in the reduced pressure register beneath the main regulator diaphragm and the pilot diaphragm as well, refer to figure 2. Inlet pressure is also used for the pilot supply pressure. If downstream flow increases, lowering the reduced pressure below the regulator set point, pressure under the pilot diaphragm and the main regulator diaphragm decreases. The pilot opens to supply the required loading pressure increase. The increased

UPSTREAM PRESSURE DOWNSTREAM PRESSURE

Figure 2. Operational Schematic

LOADING PRESSURE

3

Type S251C

Figure 3. Type S251C Main Regulator Assembly valve disc fully open, a relief valve is used to keep loading pressure in the main regulator spring case within acceptable limits. The relief valve opens and excess loading pressure is dumped into the downstream system when pilot output exceeds the downstream pressure by about 5 psi. The relief valve, located in the pilot body, is non-adjustable.

Under normal flow conditions, the excess loading pressure bleeds through the pilot restriction hole to the downstream system until the pressures are equal.

To replace the main diaphragm: 1. Disconnect the tubing connectors, (key 41 & 42, figure 3) from pilot and regulator body.

2. Remove closing cap (key 3, figure 3) and unscrew the screw (key 43). Take out the spring retainer (key 34) and spring (key 6).

3. Take out the spring case screws and lift the spring case (key 2) with attached pilot off the body and stem (key 9).

MAINTENANCE

4. Lift the diaphragm assembly slightly so that the pusher post (key 7) can release the valve lever (key 11).

WARNING

5. Unscrew the stem from the pusher post. The diaphragm can be disassembled by removing the pusher post cap (key 19) and the seat pads (key 35).

To avoid personal injury or equipment damage, do not attempt any maintenance or disassembly without first isolating the regulator from system pressure and relieving all internal pressure as described in "Shutdown".

Regulators that have been disassembled for repair must be tested for proper operation before being returned to service. Only parts manufactured by Fisher should be used for repairing Fisher regulators. Relight pilot lights according to normal startup procedures.

Due to normal wear or damage that may occur from external sources, this regulator should be inspected and maintained periodically. The frequency of inspection and replacement of parts depends upon the severity of service conditions or the requirements of local, state, and federal rules and regulations.

4

Main Regulator

6. Reassemble in the reverse order of the above procedure. Be sure the diaphragm is aligned correctly.

The texturized side of the diaphragm should be towards the diaphragm head and lower casing. Be sure the diaphragm does not fold over at the flange when tightening the flange screws.

To replace valve disc and seat ring: 1. Insert a 1/2" allen wrench through the body inlet into the socket head of the seat ring (key 16) and unscrew.

2. A 1/2" thinwall socket can then be inserted through the body inlet to unscrew the valve disc assembly (key 15).

3. Replace the valve disc or seat ring if either is nicked, cut, or otherwise damaged.

4. Reassemble in the reverse order of the above procedure. Treat the male threads of the new seat ring with pipe compound before reassembling.

Type S251C

Pilot To remove the diaphragm for inspection or replacement, loosen locknut (key 11, figure 4) and turn adjusting screw, handwheel, or adjusting cap counterclockwise until compression is removed from spring (key 9). Remove six screws and separate body (key 1) and spring case (key 2). Inspect diaphragm assembly (key 7) and replace if necessary.

To replace valve plug (key 4), unscrew body plug (key 3).

Be careful to keep valve spring (key 6) and valve spring seat (key 5 – used only with composition valve plug) from falling out and getting lost while removing valve plug.

ORDERING PARTS The type number, seat ring (orifice) size, and date of manufacture are stamped on the nameplate. Always provide this information in any correspondence with your Fisher representative regarding replacement parts or technical assistance. If construction changes are made in the field, be sure that the nameplates are also changed to reflect the most recent construction.

Figure 4. Type S251C Pilot Assembly

PARTS LIST

Key

Main Regulator (Figure 3) Key

Description

Body 3/4" x 1" 1" x 1" 2 Spring Case 3 Closing Cap 4* Gasket 5 Adjusting Screw 6 Closing Spring 7 Pusher Post 9 Stem 10* Diaphragm Diaphragm Head 11 Valve Lever 12 Pivot Pin

13 14 15* 16

Part Number

1

T40286 T40244 T40101 1J3165 1E1056 1H9657 T12735 2H9656 T12736 1H9663 1H9659 1H9662 1E9837

T0012 T0012 08012 44012 06992 44012 T0012 08012 T0012 02082 11042 25062 35032

17 19 34 35 36 37 39 40 41 42 43 44

Description Screw (2 req'd) Valve Stem Disc & Disc Holder Seat Ring 1/8" 3/16" 1/4" 3/8" Screw (8 req'd) Pusher Post Cap Spring Retainer Pad (2 req'd) Pilot Inlet Tube Side Outlet Tube Elbow Nipple Tube Elbow (3 req'd) Tube Connector Screw Lock Washer

Part Number 1E9854 28982 1H9666 000A2 1H9668 000A2 1H9675 1H9676 1H9677 1H9678 1B2856 1H9660 T10073 T12461 T12753 T12754 1A9132 11A374 1A3971 1A3959 1B7839 1H2671

09012 09012 09012 09012 28982 25062 24152 T0012 T0012 T0012 21992 0X012 14012 14012 28982 28982

Pilot (Figure 4) Key

Description

1 2 3 4 5 6 7* 8 9 10 11 12 23 24

Body Assembly Spring Case Body Plug Inner Valve Valve Spring Seat Valve Spring Diaphragm Assembly Upper Spring Seat Spring, 2-20 psi Adjusting Screw Locknut Screw (6 req'd) Gasket Screen Holder Assembly Relief Valve

42

Part Number 1B7971 2B7974 1B7975 1D5604 1E5322 1B7979 1B7980 1B7985 1B9860 1B7986 1A9463 1B7839 1C4957

X0092 08012 09032 000A2 11032 37022 000B2 25062 27212 28982 24122 28982 04022

Type P501 13A508 3X012

* Recommended Spare Part

5

Type S251C

While this information is presented in good faith and believed to be accurate, Fisher Controls does not guarantee satisfactory results from reliance upon such information. Nothing contained herein is to be construed as a warranty or guarantee, express or implied, regarding the performance, merchantability, fitness

Fisher Controls

or any other matter with respect to the products, nor as a recommendation to use any product or process in conflict with any patent. Fisher Controls reserves the right, without notice, to alter or improve the designs or specifications of the products described herein.

For information, contact Fisher Controls: Marshalltown, Iowa 50158 USA Cernay 68700 France

Sao Paulo 05424 Brazil Singapore 2158 Printed in USA