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D20
0037
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2
2500-249 Series Pneumatic Controllers andTransmittersTypical caged and cageless sensor/instrumentconfigurations are shown in figures 1 and 2. Cagedsensors (figure 3) provide more stable operationthan do cageless sensors (figure 4) for vessels withinternal obstructions or considerable internalturbulence. Cageless sensors are generally used onspecific gravity and interface control applicationsrequiring large displacers that are more easilyaccommodated by flange connections up to 8inches, and the availability of many differentdisplacer stem lengths permits lowering the
displacer down to the most advantageous depth inthe vessel.
The Level-Trol� product line is used whereverrugged, dependable, and simply constructeddisplacer-style pneumatic instrumentation is requiredin liquid level, interface level, or density service. Theruggedness of these products is demonstrated bytheir use in many kinds of demanding applications,including those in the power, chemical process, oiland gas production, and petrochemical industries.
STANDARD CAGED SENSORS MOUNT ON
VESSEL SIDE WITH DISPLACER INSIDE CAGE
W8332
W8334
CAGELESS SENSORS CAN MOUNT ON VESSEL
SIDE OR TOP WITH DISPLACER INSIDE VESSEL
CAGELESS TYPE 249W SENSOR CAN
MOUNT ON VESSEL TOP OR ON
CUSTOMER SUPPLIED CAGE
W8230
Figure 1. Typical Level-Trol� Configurations
Product Bulletin34.2:2500May 2004 2500-249 Controllers and Transmitters
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
2
SpecificationsAvailable Configurations
See tables 1, 4, and 5
Input Signal(1)
Fluid Level or Fluid-to-Fluid Interface Level:From 0 to 100 percent of displacerlength—standard lengths for all sensors are� 356 mm (14 inches) or � 813 mm (32 inches);other lengths available depending on sensorconstructionFluid Density: From 0 to 100 percent ofdisplacement force change obtained with givendisplacer volume—standard volumes are � 980cm3 (60 inches3) for Types 249C and 249CPsensors or � 1640 cm3 (100 inches3) for mostother sensors; other volumes available dependingupon sensor construction
Allowable Specific Gravity
Specific gravity with standard volume displacersand standard wall torque tubes:Fluid Level and Fluid-to-Fluid Interface:.2500 Series, except 2503 and 2503R—Specificgravity range, 0.20 to 1.102503 and 2503R—Specific gravity range, 0.25 to1.10Fluid Density:.2500 Series, except 2503 and 2503R—Minimumchange in specific gravity, 0.202503 and 2503R—Minimum change in specificgravity, 0.25For other than standard applications, refer to PSSheet 34.2:2500(A).
Output Signal(1)
See table 1
Output Action
� Direct (increasing fluid or interface level orspecific gravity increases output pressure) or� Reverse (increasing fluid or interface level orspecific gravity decreases output pressure)
Area Ratio of Relay Diaphragms
3:1
Supply Pressure(1)(4)
Normal Operation: See table 3.
Maximum to Prevent Internal Part Rupture(2):3 bar (45 psig)
Steady-State Air Consumption(1)
See table 3
Proportional Band(1), Differential Gap, or Span(1)
See table 1
Set Point(1) (Controllers Only)Continuously adjustable to position control pointor differential gap of less than 100 percentanywhere within displacer length (fluid or interfacelevel) or displacement force change (density)
Zero Adjustment(1) (Transmitters Only)Continuously adjustable to position span(1) of lessthan 100 percent anywhere within displacerlength (fluid or interface level) or displacementforce change (density)
PerformanceIndependent Linearity(1) (Transmitters Only): 1percent of output pressure change at span of 100percentHysteresis: 0.6 percent of output pressurechange at 100 percent of proportional band,differential gap, or spanRepeatability(1): 0.2 percent of displacer lengthor displacement force changeDeadband(1) (Except Differential GapControllers(3)): 0.05 percent of proportional bandor spanTypical Frequency Response(1): 4 Hz and90-degree phase shift at 100 percent ofproportional band, differential gap, or span withoutput piped to typical instrument bellows using6.1 meters (20 feet) of 0.25 inch (6.4 mm) tubingAmbient Temperature Error: ±1.5 percent ofoutput pressure change per 28�C (50�F) oftemperature change at 100 percent ofproportional band, differential gap, or span whenusing sensor with standard wall N05500(K-Monel) torque tubeReset(1) (Proportional-Plus-Reset ControllersOnly): Continuously adjustable from 0.005 to over0.9 minutes per repeat (from 200 to under 1.1repeats per minute)Anti-Reset Differential Relief (Type 2502F and2502FR Controllers Only): Continuouslyadjustable from 0.14 to 0.48 bar (2 to 7 psi)differential to relieve excessive differencebetween proportional and reset pressures
Standard Tubing Connections0.25 inch NPT female
-continued-
2500-249 Controllers and TransmittersProduct Bulletin34.2:2500May 2004
3
Specifications (Continued)Sensor Connection Sizes
See tables 4 and 5
Maximum Working Pressures (Sensors Only)(4)
Consistent with applicable ANSIpressure/temperature ratings for the specificsensor constructions shown in tables 4 and 5
Operative Ambient Temperatures(4)
Controller.� Standard -40 to 71�C (-40 to 160�F)� High Temperature -18 to 104�C (0 to 220�F)Sensor.See table 2For ambient temperature ranges, guidelines, anduse of optional heat insulator, see figure 5.
Standard Supply and Output Pressure Gauge Indications
See table 3
Allowable Process Temperatures(4)
See table 2
Hazardous Area Classification
2500 Series controllers comply with therequirements of ATEX Group II Category 2 Gasand Dust
Construction Materials
See tables 2 and 6
Mounting Positions
See figure 10
Caged Sensor Connection Styles
See figure 11
Options
See Options section
1. Term defined in ISA Standard S51.1.2. Also see Supply Pressure Overpressure Protection section.3. For Types 2500S, 2500SC, and 2503 adjusting the differential gap is equivalent to adjusting the deadband.4. The pressure/temperature limits in this bulletin and any applicable standard or code limitation should not be exceeded.
Features
� Easy Adjustment—Set point, proportionalvalve opening, and reset changes are made withsimple dial-knob controls.
� Simple, Durable Construction—Few movingparts are used. Knife-edged driver bearing in sensorand plated brass instrument case ball bearing fortorque tube rotary shaft help provide low-frictionoperation. Sensors are available in ratings up toANSI Class 2500 and are hydrostatically tested toANSI standards.
� Mounting Versatility—Caged sensors areavailable in a variety of orientations and connectionstyles, and all sensors can be either right- orleft-hand mounted.
� Sensitive to Small Changes—Displacerreaction to small specific gravity changes allowsthese instruments to be used for density applications
and in other applications where a response to lowlevels of input signal change is required.
� Easy Reversibility—Action is field reversiblefrom direct to reverse or vice versa without additionalparts.
� Reduced Maintenance Costs—Spring-outwire provides for in-service cleaning of relay orifice(figure 2). Torque tube can be replaced withoutremoving torque tube arm.
� Reduced Operating Costs—Supply pressureconservation is enhanced in all constructionsbecause relay exhaust opens only when outputpressure is being reduced.
� Smaller Vessel Sizes Required for StableControl—Caged 249 Series sensors come standardwith a liquid damping orifice in the lower equalizingconnection that helps stability where vesselcapacitance is small and permits narrowerproportional valve settings.
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
4
Table 1. Additional Specifications for Selected 2500 Series Configurations
CONTROL OR TRANSMISSION MODE TYPE NUMBER(1) FULL OUTPUT SIGNAL CHANGE OBTAINABLEOVER INPUT OF:
OUTPUT SIGNAL
Proportional control 2500, 2500C(2)Proportional band of 0 to 100 percent ofdisplacer length or displacement forcechange (10 to 100 percent recommended)
0.2 to 1.0 bar(3 to 15 psig)
Proportional-plus-reset control 2502, 2502C(2) Proportional band of 0 to 200 percent of(3 to 15 psig)or 0.4 to 2.0 bar
Proportional-plus-reset controlwith anti-reset windup
2502F
Proportional band of 0 to 200 percent ofdisplacer length or displacement forcechange (20 to 200 percent recommended)
o 0 o 0 ba(6 to 30 psig)
Differential
With proportional valveand full differentialgap adjustment
2500S,2500SC(2)
Differential gap of 0 to 100 percent ofdisplacer length
0 and 1.4 bar (0 and20 psig) or 0 and 2.4bar (0 and 35 psig)
DifferentialGap(On-off)Control
Without proportional valve-has limited differentialgap adjustment
2503
Differential gap of approximately 25 to 40 percentof displacer length, when a 356 millimeter (14-inch)ideal-volume displacer is used on 1.0 specific gravityliquid level service and a standard 1.4 bar (20 psig)supply regulator setting is varied between 1.0 and1.7 bar (15 and 25 psig)(3)
0 and full supplypressure(4)
Proportional transmission2500T,2500TC(2)
Span of 0 to 100 percent of displacer lengthor displacement force change (20 to 100percent recommended)
0.2 and 1.0 bar (3 to15 psig) or 0.4 to 2.0bar (6 to 30 psig)
1. The suffix R is added to the type number for reverse action, and all types have a Type 67CFR supply regulator mounted as standard.2. The suffix C is added to the type number for indicator assembly.3. Other displacer lengths and volumes, or service conditions, will result in other differential gaps.4. 1.4 bar (20 psig) and 2.4 bar (35 psig) are the standard factory-set supply regulator pressures, but these values will vary whenever the supply pressure is changed to adjust thedifferential gap.
Table 2. Allowable Process Temperatures for Common 249 SensorComponent Materials
MaterialProcess Temperature
MaterialMinimum Maximum
Cast Iron(1) -29�C (-20�F) 232�C (450�F)
Steel -29�C (-20�F) 427�C (800�F)
Stainless Steel -198�C (-325�F) 427�C (800�F)
Monel -198�C (-325�F) 427�C (800�F)
Aluminum -195�C (-320�F) 99�C (210�F)
Soft Iron Gasket -29�C (-20�F) 427�C (800�F)
GasketsComposition andSST/compositionGraphite Laminate/SST
Monel/PTFE
-29�C (-20�F)-198�C (-325�F)
-73�C (-100�F)
150�C (302�F)427�C (800�F)
204�C (400�F)
BoltingB7 steelB7M steelB8M stainless steel
-46�C (-50�F)-29�C (-20�F)
-198�C (-325�F)
427�C (800�F)427�C (800�F)427�C (800�F)
1. Cast iron may be used to -73�C ( -100�F) provided a heat insulator is used below -18�C(0�F) and stainless steel studs and nuts are used below -46�C ( -50�F).
2500-249 Controllers and TransmittersProduct Bulletin34.2:2500May 2004
5
Table 3. Supply Pressure Data
OUTPUT SIGNAL
STANDARD SUPPLYAND OUTPUT
PRESSURE GAUGE
NORMALOPERATING
SUPPLYPRESSURE(2)
AIR CONSUMPTION ATNORMAL OPERATINGSUPPLY PRESSURE(3)
PRESSURE GAUGEINDICATIONS(1) Normal m3/h(6) Scfh(6)INDICATIONS
Bar Psig Min(4) Max(5) Min(4) Max(5)
0.2 to 1.0 bar (3 to 15 psig),except 0 and 1.4 bar (0 and 20psig)(2) for on-off controllers
0 to 30 psig 1.4 20 0.11 0.72 4.2 27
0.4 to 2.0 bar (6 to 30 psig),except 0 and 2.4 bar (0 and 35psig)(2) for on-off controllers
0 to 60 psig 2.4 35 0.19 1.1 7 42
1. Consult your Fisher sales office about gauges in other units.2. Control and stability may be impaired if this pressure is exceeded (except Type 2503 or 2503R controller without proportional valve).3. Except Type 2503 or 2503R controller, which bleeds only when relay is open at exhaust position.4. At zero or maximum proportional band or span setting.5. At setting in middle of proportional band or span range.6. Normal m3/hr=normal cubic meters per hour at 0�C and 1.01325 bar. Scfh=standard cubic foot per hour at 60�F and 14.7 psia.
DETAIL OF REVERSE−ACTING TYPE 2503R
ON−OFF CONTROLLER
DETAIL OF DIRECT ACTING TYPE 2502
PROPORTIONAL−PLUS RESET CONTROLLER
INDICATOR ASSEMBLY DETAIL DIRECT−ACTING TYPE 2500 CONTROLLER
RESET ADJUSTMENT 3-WAY BOURDON TUBE VALVE HAS LARGEPORTS WHICH GREATLY REDUCE CLOGGING
PIPE PLUG INSTEAD OF PROPORTIONALVALVE MEANS INTERMITTENT BLEEDTHAT MINIMIZES FREEZE UP
SPRING-OUTCLEANING WIRE
PROPORTIONAL BANDADJUSTMENT
POINTER
INDICATOR ANDBASE PLATES
W5637/IL
W0656-1/IL
W0648-1/IL
W0671-1/IL
Figure 2. Typical 2500 Series Constructions with Right-Hand Mounting Shown
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
6
W0144-1/IL
DAMPING ORIFICE(REMOVABLE IF CLOGGING WILL OCCUR)
W1800-1/IL
W2141-1/IL
KNIFE EDGE BEARING
TORQUE TUBE
DISPLACER ROD
ROTATABLEHEAD
DISPLACER
CAGE
Figure 3. Type 249B Caged Sensor (Typicalof all Rotatable-Head Caged Sensors)
DISPLACER ROD
DISPLACER STEM ENDCONNECTOR
OPTIONALTRAVELSTOP PINAND PLATE
DISPLACERSTEM
DISPLACERSTUD
TYPE 249BP MOUNTS
ON TOP OF VESSEL
W0660-1/IL
TYPE 249V MOUNTS
ON SIDE OF VESSEL
W0172-1
STANDARD TRAVEL STOP ASSEMBLY
TYPE 249W WAFER BODY 3- OR 4-INCHRF FLANGE
STILLWELL 1
1NOTE:
STILLWELL REQUIRED AROUND DISPLACER IF THE FLUIDIS IN A STATE OF CONTINUOUS AGITATION
W8252
CENTER OF DISPLACERSHOULD BE LOCATIONOF LIQUID OR INTERFACELEVEL DURING NORMALOPERATION
TYPE 249W MOUNTS ON TOP OF VESSEL AS SHOWN
OR CAN MOUNT IN CUSTOMER FABRICATED CAGE
Figure 4. Typical Cageless Sensors
2500-249 Controllers and TransmittersProduct Bulletin34.2:2500May 2004
7
Table 4. Caged Displacer Sensors(1)
TYPENUMBER
EQUALIZINGCONNECTION ANSI
CLASS(2)NUMBERStyle Size (Inch)
CLASS(2)
249(3)Screwed 1.5 or 2
125 or 250
Torque tube
249(3)Flanged 2
125 or 250
Torque tubearm rotatable
Screwed or optional socket weld 1.5 or 2 600arm rotatablewith respect 249B or 249BF(4)
Raised face or optional ring type joint flanged1.5 150, 300, or 600with respect
to equalizing
249B or 249BFRaised face or optional ring-type joint flanged
2 150, 300, or 600o eq a gconnections Screwed 1.5 or 2 600
249C(2)Raised face
1.5 150, 300, or 600249CRaised face
2 150, 300, or 600
249K Raised face or optional ring-type joint flanged 1.5 or 2 1500
249L Ring-type joint flanged 2(5) 25001. Standard displacer lengths for all styles (except Type 249) are 14, 32, 48, 60, 72, 84, 96, 108, and 120 inches. Type 249 uses a displacer with a length of either 14 or 32 inches.2. DIN flange connections available in EMA (Europe, Middle East, and Africa).3. Not available in EMA.4. Type 249BF available in EMA only. Also available in DIN size DN40 with PN10 to PN100 flanges and size DN50 with PN10 to PN63 flanges.5. Top connection is 1-inch ring-type joint flanged for connection styles F1 and F2.
Table 5. Cageless Displacer Sensors(1)
MOUNTING TYPENUMBER
FLANGE CONNECTION ANSI CLASS(2)
Mounts on top of 249BP(3)4-inch raised face or optional ring-type joint 150, 300, or 600
Mounts on top ofvessel
249BP(3)6-inch or 8-inch raised face 150 or 300
vessel249CP 3-inch raised face 150, 300, or 600
Mounts on top ofvessel
249P(4)4-inch raised face or optional ring-type joint
900 or 1500(DIN PN10 to PN250)
vessel249P( )
6-inch or 8-inch raised face 150, 300, 600, 900, 1500, or 2500
4-inch 125 or 250
Mounts on side249V
4-inch raised face or optional ring-type joint300, 600, 900, or 1500(DIN PN10 to PN160)Mounts on side
of vessel249V 4-inch ring-type joint 2500of vessel
4-inch raised face or flat face 150
4-inch raised face or optional ring-type joint 300, 600, or 900
Mounts on top ofvessel or oncustomersupplied cage
249W 3-inch or 4-inch raised face 150, 300, 600
1. Standard displacer lengths are 14, 32, 48, 60, 72, 84, 96, 108, and 120 inches.2. DIN flange connections available in EMA (Europe, Middle East, and Africa).3. Not available in EMA.4. Type 249P with 6 and 8 inch flanges and DIN flanges are available in EMA only.
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
8
80 90
0 20 40 60 80 100 120 140 160
-40 7071
400
300
200
100
00
400
800
-325 -240
NO INSULATOR NECESSARY
AMBIENT TEMPERATURE (�C)
STANDARD CONTROLLER
AMBIENT TEMPERATURE (�F)
HEAT INSULATOR REQUIREDTOOHOT
NOTE: FOR PROCESS TEMPERATURES BELOW -29�C ( -20�F) AND ABOVE 204�C (400�F)SENSOR MATERIALS MUST BE APPROPRIATE FOR THE PROCESS - SEE TABLE 2.2. IF AMBIENT DEWPOINT IS ABOVE PROCESS TEMPERATURE, ICE FORMATION MIGHTCAUSE INSTRUMENT MALFUNCTION AND REDUCE INSULATOR EFFECTIVENESS.
PR
OC
ES
S T
EM
PE
RA
TU
RE
( C
)
�
PR
OC
ES
S T
EM
PE
RA
TU
RE
( F
)
�
0 20 40 60 80 100 120 140 200
0 10 20-18 -10 30 40 50 60 7093
400
300
200
100
00
400
800
-325
NO INSULATOR NECESSARY
AMBIENT TEMPERATURE (�C)
HIGH−TEMPERATURE CONTROLLER
AMBIENT TEMPERATURE (�F)
HEAT INSULATOR REQUIREDTOOHOT
PR
OC
ES
S T
EM
PE
RA
TU
RE
( C
)
�
PR
OC
ES
S T
EM
PE
RA
TU
RE
( F
)
�
180160
B1413-1A/IL
1
1
-100
-200
-40 -20
1
-240
-100
-200HEAT INSULATOR REQUIRED
TOO COLD
TOO COLD
HEAT INSULATOR REQUIRED
0 10 20-20 -10 30 40 50 60-30
Figure 5. Guidelines for Use of Optional Heat Insulator Assembly
2500-249 Controllers and TransmittersProduct Bulletin34.2:2500May 2004
9
Table 6. Construction MaterialsPART TYPE NUMBER MATERIAL
In contactith
Cage, head,t t b
249 Cast ironwith process
g , ,torque tube arm 249B, 249BF(1) Carbon steel
249C and 249CP CF8M (316 stainless steel) standard,CF3M (316L stainless steel),CF8 (304 stainless steel), CF3 (304L stainless steel),LCB (steel), C5 (steel),LC3 (3.5 percent nickel steel), M35-1 (Monel),CN7M (Alloy 20)
249K Steel standard, CF8, CF8M, CF3M, LCB, C5,LC3, WC1 (chrome moly steel), M35-1, CN7M optional
249L Steel standard, CF8M, C5, WC1, LCB
249BP WCB
249P & 249V Cast iron or steel
Wafer body,torque tube arm
249W 3-inch4-inch
WCC (steel), CF8M (316 stainless steel)LCC (steel), CF8M (316 stainless steel)
Torque tube 249, 249B, 249BF(1),249K, 249L,249P, cast iron orcast steel 249V,249W
N05500 (K-Monel) standard
249C, 249CP,stainless steel 249V,249W
S31600 (316 stainless steel) standard
All S30403 (304L stainless steel), S31603 (316L stainless steel),N06600 (Inconel), N08020 (Alloy 20) optional
Displacer 249, 249B, 249BF(1),249K, 249V, 249W
S30400 (304 stainless steel) standard
249C, 249CP, 249W S31600 (316 stainless steel) standard
249L A91100F (solid aluminum) standard
All Solid PTFE, N04400 (Monel) or other special materials
Standard trim(2) All S31600
Bolting All Steel grade B7 studs or cap screws and grade 2H nuts (standard),steel grade B7M studs and grade 2M nuts optional on Type 249B and WCC 249W sensor
Standard torquetube end gasket
All 316 stainless steel/graphite laminate, except 304 stainless steel/graphite laminate for Type 249K sensor
Standard torquetube arm andcage gasket, if used
All Composition, except soft iron for Type 249L sensor
Optional trimand gasketing
All 316 stainless steel trim with 316L stainless steel gasketingor soft iron gasketing; 317 stainless steel or Inconel trim with compositiongasketing; 304, 304L or 316L stainless steel, Monel orCarpenter 20 trim and gasketing
In contactith l
Bourdon tube or bellows Brass, plus SST 3-way valve for Type 2503 or 2503R controllerwith supplypressure
Tubing Stainless steelpressure
Relay diaphragms Nitrile (standard) or polyacrylate (high-temperature)
Relay O-ring Nitrile
Gasketing Neoprene (standard) or rubber (high-temperature)
Seal ring O-rings (and reset reliefvalve O-rings if used)
Nitrile (standard) or fluoroelastomer (high-temperature)
Other Case Aluminum
Cover Aluminum with glass gauge windows and nitrile cover gasket
Retaining flange Steel1. Available only in EMA.2. Trim parts include displacer rod, driver bearing; displacer stem parts, and stem connection parts.
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
10
CD2114-EB2296/IL
Figure 6. Schematic of Direct-Acting 2500-249 Series Proportional Controller (or Transmitter) Shown with Right-Hand Mounting
Supply Pressure OverpressureProtection
Applying excessive pressure to any portion of acontroller, transmitter or connected equipment maycause leakage, part damage, or personal injury dueto bursting of pressure-containing parts. Althoughthe standard Type 67CFR supply regulator for 2500Series instruments has internal relief to provide verylimited overpressure protection, completeoverpressure protection between the supplyregulator outlet and the instrument case is needed ifa malfunctioning supply regulator can deliver asupply pressure that exceeds 3.4 bar (50 psig).
Principle of Operation
All 2500 Series controllers and transmitters use thesame basic pressure-balanced relay with a yokeddouble-diaphragm assembly. Supply pressure eitherpasses through the fixed orifice and bleeds out thenozzle (figure 6 or 7) or directly enters the Bourdontube valve (figure 8). Nozzle pressure registers onthe large relay diaphragm, and output pressure onthe small relay diaphragm.
The following descriptions show how the variouscontroller and transmitter constructions work inconjunction with displacer action.
2500-249 Controllers and TransmittersProduct Bulletin34.2:2500May 2004
11
PROPORTIONALBELLOWS
TORQUE TUBE SHAFT SET POINTADJUSTMENT
RESET VALVE
PROPORTIONALVALVE
EXHAUST TO PROPORTIONALBELLOWS
TO RESET BELLOWS
SUPPLY PRESSURE
OUTPUT PRESSURE
NOZZLE PRESSURE
PROPORTIONALPRESSURERESET PRESSURE
WITH ARROW DOWN-RELIEVES ONDECREASING OUTPUT(OUTPUT AT SUPPLYDURING SHUTDOWN)
DIFFERENTIALRELIEFVALVE
FROMRELAY
PROPORTIONBANDADJUSTMENT
RESETADJUSTMENT
CJ4081-AB2347-2E0792 PROPORTIONAL−PLUS−RESET CONTROL
WITH ANTI−RESET WINDUP
Figure 7. Schematic of Direct-Acting Proportional-Plus-Reset Controller
Proportional Controller or Transmitter
As long as the process remains constant, thedisplacer will hold the torque tube shaft and attachedflapper steady in relation to the nozzle. Thenozzle-flapper opening will be such as to permitpressure to bleed from the nozzle as fast as it entersthrough the fixed orifice of the relay, keeping thepressure loading on the large relay diaphragm at theamount necessary to balance the output pressureloading on the small relay diaphragm.
A process variable change (such as a variation indownstream demand that affects liquid outflow andthus the level of the tank shown in figure 6) changesthe buoyant force acting on the displacer and movesthe flapper with respect to the nozzle. An increasingbuoyant force with direct action, or decreasingbuoyant force with reverse action, produces anozzle-flapper restriction that increases nozzlepressure on the large relay diaphragm. This opensthe supply end of the relay valve and increases relayoutput pressure. But a decreasing buoyant force withdirect action, or increasing buoyant force withreverse action, produces a nozzle-flapper openingthat bleeds off nozzle pressure on the large relay
diaphragm and opens the exhaust end of the relayvalve to let output pressure (and thus actuatorloading pressure) bleed away. The relay diaphragmpressure differential equalizes and a new outputpressure is maintained according to the change indisplacer position.
Proportional-Plus-Reset Controller
All 2502 Series controllers (figure 7) have a two-wayreset restriction valve that channels proportionalpressure into a reset bellows to oppose proportionalbellows action. This automatically slows thecanceling effect of any proportional action by a setamount per time interval, as long as there is adeviation from the control point. Action of this resetpressure occurs on a delayed basis, and the resetvalve can be adjusted to vary the time of delay.
If a prolonged difference exists between the set pointand the process variable, output pressure with aproportional-plus-reset controller will either drop tozero or rise to the maximum delivered by the supplyregulator. This condition is called reset windup.
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
12
Anti-Reset Windup
Type 2502F and 2502FR controllers additionallyhave anti-reset windup to minimize the delay inreturning the controlled variable to the set point. Thiscapability is provided by a reversible differential reliefvalve with adjustable spring. As shown in figure 7,proportional pressure registers rapidly on the springside of the relief valve diaphragm as well as in theproportional bellows. Reset pressure registers slowlyon the opposite side of the diaphragm. As long asthe output pressure changes are slow enough fornormal proportional and reset action, the relief valvespring prevents opening of the relief valvediaphragm.
A large or rapid decrease in controller outputpressure decreases the pressure in the proportionalsystem, and on the spring side of the reliefdiaphragm. If the decrease on the spring side of thediaphragm is greater than the relief valve springsetting, the diaphragm moves off the relief valveorifice and permits reset pressure on the oppositeside of the relief valve diaphragm to bleed rapidlyinto the proportional system. The differential reliefvalve can also be reversed to relieve with anincreasing output pressure.
On-Off Controller With Proportional Valve
This construction has the same flapper, relay, andproportional valve responses to a level or densitychange as does a proportional 2500 Seriescontroller. However, the Bourdon tube is constructed(figure 2) so that output pressure change feedbackmoves the nozzle in the opposite direction from theway the flapper is moving. This reinforcementcompletely opens the relay valve either to full supplypressure or to full exhaust of output pressure,allowing no in-between throttling.
On-Off Controller Without Proportional Valve
As long as vessel level or density remains above thelower snapping point on a direct-acting controller (orbelow the upper snapping point on a reverse-actingcontroller), the flapper remains far enough away tokeep the exhaust port of the Bourdon tube valveclosed and prevent any pressure escape from theBourdon tube. The relay valve remains closed at theexhaust end and open at the supply end, allowingfull output pressure into the control valve actuator.
When level or density sufficiently decreases withdirect action or increases with reverse action, the
flapper pushes the Bourdon tube valve in enough toseal the inner Bourdon tube channel (figure 8). Thisopens the exhaust port of the valve and permitsexhaust of pressure from the actuator, initiating theappropriate control action. This control actioncontinues until the level or density change againmoves the flapper away enough to permit closing ofthe Bourdon tube valve exhaust port and the fullapplication of output pressure to the actuator.
Options
� Stainless Steel Heat InsulatorAssembly—Refer to figure 9. Available for mountingbetween the torque tube arm of any 249 Seriessensor and the instrument. Recommended forapplications where combination of process andenvironmental temperatures would result incontroller temperatures in excess of safe limits(figure 5).
� Jerguson Gauges—Permit direct observationof process level and other relevant characteristics.These gauges are described in the JergusonGauges supplement. The Type 249 sensor cagecomes standard with suitable bosses that can betapped for gauge installation. All other sensorsrequire the gauges to be installed at the factory.When specified, the bosses will be tapped 0.5 inchNPT on the Class 125 Type 249 sensor, and 0.75 inch NPT on the Class 250 Type 249.
InstallationAlthough it can be shipped alone for separateinstallation, a 249 Series sensor usually is shippedwith a controller or transmitter installed. Duringshipment, displacers are detached from cagelesssensors and optional tubular gauge glasses aredetached from caged sensors.
Equalizing piping, stillwells, or other equipment maybe required for installation. Fisher does not providethis equipment.
Complete dimensions and case connectioninformation for all 2500-249 Series constructionsappears in the separate Level-Trol Dimensionsbulletin supplement.
2500-249 Controllers and TransmittersProduct Bulletin34.2:2500May 2004
13
B04466-EA2546-1/IL
Figure 8. Schematic of Reverse-Acting Type 2503R Controller
W0630-2/IL
TORQUE TUBEARM
TORQUE TUBESHAFTEXTENSION
TORQUE TUBE SHAFT
SHAFTCOUPLING
Figure 9. Optional Heat Insulator Assembly
Ordering Information
Note: Fisher does not assume responsibility forthe selection, use, or maintenance of anyproduct. Responsibility for proper selection, use,and maintenance of any Fisher product remainssolely with the purchaser or end-user.
ApplicationWhen ordering, specify:
� Control (proportional, proportional-plus-reset,or on-off), or transmission mode
� Liquid level service (give type, pressure,temperature and specific gravity)
� Interface level service (give specific gravity ofboth liquids and minimum proportional band,differential gap, or span required)
� Density service (give minimum and maximumspecific gravity required)
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
14
AH9150-A15A110-CB1407-1/IL
Figure 10. Torque Tube Arm Mounting Positions
2500-249 Controllers and TransmittersProduct Bulletin34.2:2500May 2004
15
A1271-3/IL
SCREWED: S1FLANGED: F1SOCKET WELD: SW1
SCREWED: S2FLANGED: F2SOCKET WELD: SW2
SCREWED: S3FLANGED: F3SOCKET WELD: SW3
SCREWED: S4FLANGED: F4SOCKET WELD: SW4
Figure 11. Cage Connection Styles
ConstructionRefer to the specifications and the Options section.Review the descriptions for each specification, undereach option, and in the referenced tables andfigures; specify the desired selection whenever thereis a choice to be made. Right-hand mounting (withposition 1 if appropriate) will be suppliedautomatically unless some other mounting method isspecified. Unless another length is specified, 305millimeters (12 inches) will be used as the standard
cageless sensor length from flange face—ordisplacer rod—to displacer top.
Always specify the complete type number (includingthe R suffix for reverse action) of the Level-Trolcontroller or transmitter, sensor, supply pressureregulator, and other desired equipment. Ondifferential relief controllers, specify whether relief isto occur with excessive proportional or withexcessive reset pressure.
2500-249 Controllers and TransmittersProduct Bulletin
34.2:2500May 2004
16
Fisher Marshalltown, Iowa 50158 USACernay 68700 France Sao Paulo 05424 BrazilSingapore 128461
The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy,they are not to be construed as warranties or guarantees, express or implied, regarding the products or services described herein or their useor applicability. We reserve the right to modify or improve the designs or specifications of such products at any time without notice.
Fisher does not assume responsibility for the selection, use or maintenance of any product. Responsibility for proper selection, use and maintenance of any Fisher product remains solely with the purchaser and end-user.
�Fisher Controls International LLC 1990, 2004; All Rights Reserved Printed in USA
Fisher and Level-Trol are marks owned by Fisher Controls International LLC, a member of the Emerson Process Management businessdivision of Emerson Electric Co. The Emerson logo is a trademark and service mark of Emerson Electric Co. All other marks are the propertyof their respective owners.
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