Types 92BT and 92BTP March 2000 Instruction Manual Form 5639 D102717X012 www.FISHERregulators.com Types 92BT and 92BTP Temperature Regulators Introduction The Type 92BT is a pilot-operated, direct-acting tempera- ture regulator that does not require an external power supply. The Type 92BT is used in heating applications where steam is normally the heating medium. With proper system sizing, the Type 92BT is accurate within 3% of the maximum temperature setpoint at steady state operating conditions. The key component of the Type 92BT is the thermostat of the Type 92T temperature pilot. The temperature pilots thermostat consists of a spring opposed bellows-capillary-bulb system. This system contains a fill of an incompressible fluid at a pressure that is calibrated to the pilot’s temperature control range to provide proportional control. The pilot body assembly (key 32, figure 13) is shipped from the factory in a separate box to prevent damage to the thermostat and must be assembled on the main body by the customer. The temperature pilot body assembly should be handled with care so as not to kink the capillary tube between the bulb and the pilot body. A kink in the capillary tube can make the temperature pilot inoperable. Temperature control can be a slow process because of the heat transfer characteristics of the system the temperature regulator is controlling. This is especially true of large tanks or jacketed kettles. Once steady- state operation (warm-up period) of the system is attained, the regulator may have to be re-adjusted to attain the required setpoint. Turn the adjusting knob of the tempera- ture pilot until steady-state operation is attained. Install a temperature gauge in the process piping to facilitate setpoint adjustment. Since the Type 92BT is a temperature control regulator, it does not sense downstream pressure. During startup of a heating system, the downstream pressure could rise to full inlet pressure which can be above safe operating pressures. In these applications, it is Figure 1. Type 92BT Temperature Regulator Figure 2. Type 92BTP Temperature and Pressure Limiting Regulator W7908 W7907 (continued on page 3)
Transcript
Types 92BT and 92BTPMarch 2000
Instruction ManualForm 5639
D102
717X
012
www.FISHERregulators.com
Types 92BT and 92BTP Temperature Regulators
IntroductionThe Type 92BT is a pilot-operated, direct-acting tempera-ture regulator that does not require an external powersupply. The Type 92BT is used in heating applicationswhere steam is normally the heating medium. Withproper system sizing, the Type 92BT is accurate within3% of the maximum temperature setpoint at steady stateoperating conditions. The key component of theType 92BT is the thermostat of the Type 92T temperaturepilot. The temperature pilot�s thermostat consists of aspring opposed bellows-capillary-bulb system. Thissystem contains a fill of an incompressible fluid at apressure that is calibrated to the pilot's temperaturecontrol range to provide proportional control.
The pilot body assembly (key 32, figure 13)is shipped from the factory in a separatebox to prevent damage to the thermostatand must be assembled on the mainbody by the customer. The temperaturepilot body assembly should be handledwith care so as not to kink the capillary
tube between the bulb and the pilotbody. A kink in the capillary tube canmake the temperature pilot inoperable.
Temperature control can be a slow process because ofthe heat transfer characteristics of the system thetemperature regulator is controlling. This is especiallytrue of large tanks or jacketed kettles. Once steady-state operation (warm-up period) of the system isattained, the regulator may have to be re-adjusted toattain the required setpoint.
Turn the adjusting knob of the tempera-ture pilot until steady-state operation isattained. Install a temperature gauge inthe process piping to facilitate setpointadjustment.
Since the Type 92BT is a temperature control regulator,it does not sense downstream pressure. Duringstartup of a heating system, the downstream pressurecould rise to full inlet pressure which can be abovesafe operating pressures. In these applications, it is
Figure 1. Type 92BT Temperature Regulator Figure 2. Type 92BTP Temperature andPressure Limiting Regulator
W7908 W7907
(continued on page 3)
Types 92BT and 92BTP
2
1. Pressure/temperature limits in this Instruction Manual and any application codes must not be exceeded.2. Temperature ratings are standard ANSI ratings taken from ANSI pressure/temperature curves.
Specifications
Available ConfigurationsType 92BT: A Type 92B main valve with a Type 92Ttemperature control pilot. The Type 92T pilot onlycontrols temperature.Type 92BTP: A Type 92B main valve with a Type 92Ttemperature pilot and a Type 6392 pressure limitingpilot. The Type 6392 pilot prevents the downstreampressure from rising above its setpoint.
Body Sizes And End Connection StylesSee table 1
Maximum Allowable Inlet Pressures(1)
Type 92BTNPT Screwed and ANSI Class 250 RF Flanged:150 psig (10,3 bar)ANSI Class 125 FF Flanged: 125 psig (8,6 bar)Type 92BTPNPT Screwed and ANSI Class 250 RF Flanged:250 psig (17,2 bar)ANSI Class 125 FF Flanged: 125 psig (8,6 bar)
Maximum Allowable Outlet Pressures(1)
NPT Screwed and ANSI Class 250 RF Flanged:150 psig (10,3 bar)ANSI Class 125 FF Flanged: 125 psig (8,6 bar)
Minimum Differential Pressure(1)
20 psi (1,4 bar) with standard stainless steel springand 10 psi (0,69 bar) with optional Inconel spring
Maximum Differential Pressures(1)
NPT Screwed and ANSI Class 250 RF Flanged:250 psig (17,2 bar)ANSI Class 125 FF Flanged: 125 psig (8,6 bar)
Type 92T Temperature Control RangesSee table 2
Maximum Allowable Temperatures(1, 2)
NTP Screwed and ANSI Class 250 RF Flanged:406°F (208°C)ANSI Class 125 FF Flanged: 353°F (178°C)
Type 6392 Pressure Limiting Pilot Control RangesSee table 3
Thermostat ConnectionsSee figure 15
Temperature Control Accuracy3% of maximum scale at steady state conditions
Type 92BTP Downstream Control Line Connection1/4-inch NPT Screwed
Pilot VentType 92T: Housing open to atmosphereType 6392: 3/32-inch (2,4 mm) drilled hole
Table 2. Type 92T Temperature Control Ranges(1)Table 1. Main Valve Body Styles and End Connection Styles
,EZISYDOB)NID(SEHCNI
ELYTSNOITCENNOCDNEdewercsTPN degnalFFR052roFF521
)52(1)04(2/1-1
)05(2)08(3)001(4
seYseYseYoNoN
oNseYseYseYseY
Table 3. Type 6392 Pressure Limiting Pilot Control Ranges
ERUSSERPTELTUO)rab(GISP,EGNAR
TRAPGNIRPSREBMUN
GNIRPSROLOC
)rab(GISPNRUTREP )1(
)8,4ot43,0(07ot5 210726293E1 neerG )67,0(11
)3,01ot4,1(051ot02 241727293E1 deR )7,1(42.wercsgnitsujdatolipehtfonrutetelpmocenoreperusserpteltuoniegnahC.1
Types 92BT and 92BTP
3
recommended to use a pressure regulator upstream ofthe temperature regulator to reduce the pressure to safeoperating pressures. A popular alternative is to use aType 92BTP temperature and pressure limiting regulator.The Type 92BTP regulator features a pressure limitingpilot that prevents downstream pressure from risingabove the pressure pilot's setpoint.
Using a pressure limiting pilot does notexclude the installation of ASME certifiedfull flow relief device as specified by localcodes and regulations or system design.
Principal of Operation
Type 92BT Temperature Regulator (figure 3)The pilot is operated by a contracting or expandingspring opposed bellows, according to the sensedtemperature through a connected thermostat bulb and
capillary assembly. The thermostat assembly is filledwith an incompressible liquid, which expands or con-tracts in a linear response to the sensed temperature toprovide proportional control.
The main valve is spring closed. The pilot is held openby the force from its springs. Inlet steam passesthrough the pilot seat to increase loading pressure onthe main valve diaphragm.
The flow through the pilot is greater than the flowthrough the bleed restriction, increasing loading pres-sure and opening the main valve to provide more flow tothe downstream system.
As steam flow increases through the main valve, thedownstream temperature increases and is sensed bythe thermostat assembly. As temperature approachesthe setpoint, the liquid fill in the thermostat assemblyexpands, causing the bellows to expand. The expand-ing bellows throttles the pilot which positions the mainvalve at a flow to control temperature.
When set temperature is exceeded, the bellows assem-bly causes the pilot to close. Flow through the bleedrestriction decreases loading pressure allowing the mainvalve to close.
Figure 3. Type 92BT Temperature Regulator
BELLOWS
THERMOSTATBULB ANDCAPILLARYASSEMBLY
ADJUSTINGKNOB
TEMPERATURERANGE LABEL
SPRINGS
SEAT
MAIN VALVEDIAPHRAGMS ANDDIAPHRAGM PLATES
ORIFICE
TYPE 92TTEMPERATUREPILOT
VALVE PLUG
REDUCINGVALVE SPRING
TYPE 92B MAIN VALVEE0224
BLEED RESTRICTION
SET SCREW
INLET PRESSURE
LOADING PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
INCOMPRESSIBLE FLUID FILL
Types 92BT and 92BTP
4
Temperature AdjustmentTemperature adjustments are made by turning the greenadjusting knob (see figure 3) on top of the pilot bodyassembly clockwise to decrease and counterclock-wise to increase the temperature. The color-codedtemperature range label shows the high and low ends ofthe pilot's temperature control range. Exact valuesdepend on pressures and flow. To make final setpoint,use a temperature gauge to find the actual temperature.
When making temperature adjustments,wear gloves or other protective gear. Thetemperature pilot may be hot.
Recalibration of the Type 92T temperaturepilot may be necessary after the regulatorreaches operating temperature. Thetemperature control range may shiftdownward 0.5 degrees for every 1 degreerise above ambient temperature. See theTemperature Pilot Calibration procedure.
Type 92BTP Temperature and PressureLimiting Regulator (figure 4)The Type 92T temperature pilot on the Type 92BTtemperature regulator only controls temperature. Toprevent overpressure during startup or large tempera-ture disturbances the Type 92BTP has a Type 6392pressure limiting pilot to limit the downstream steampressure to the Type 6392 pilot's pressure setpoint.
The Type 6392 pressure limiting pilot measures down-stream pressure. It interrupts the loading signal fromthe temperature pilot to the main valve to limit themaximum outlet pressure. The Type 92BTP tempera-ture and pressure limiting regulator has two controlspring options for the Type 6392 pilot, 5 to 70 psig (0,34to 4,8 bar) and 20 to 150 psig (1,4 to 10,3 bar).
Pressure AdjustmentPressure adjustments are made by turning the pressureadjusting screw clockwise to increase the pressuresetting or counterclockwise to decrease the setting. Seetable 3 for psig (bar) per turn by spring range. Read theType 92BTP Startup section before making pressureadjustments.
Figure 4. Type 92BTP Temperature and Pressure Limiting Regulator
BELLOWS
THERMOSTATBULB ANDCAPILLARYASSEMBLY
ADJUSTINGKNOB
TEMPERATURERANGE LABEL
SPRINGS
SEAT
MAIN VALVEDIAPHRAGMS ANDDIAPHRAGM PLATES
ORIFICE TYPE 92TTEMPERATUREPILOT
VALVE PLUG
REDUCINGVALVE SPRING
TYPE 92B MAIN VALVE
TYPE 6392 PRESSURELIMITING PILOT
E0225
BLEED RESTRICTIONSET SCREW
Types 92BT and 92BTP
5
Selecting Downstream Limiting PressureWhen selecting and adjusting the pressure pilot, makesure the set pressure meets downstream systemdesign requirements. A pressure too high may exceedthe system's pressure limits. Lower saturated steampressures correspond to lower temperatures which canlengthen the heat transfer rate (time to heat) of thedownstream system. Also, select a pressure limitingsetting high enough to overcome the head (pressure)requirements of the condensate return system. Toolow of a limiting pressure can cause condensate toback up into heat transfer equipment as the steam traploses its minimum operating differential.
Pressure higher than downstream system require-ments can create additional problems. Higher steampressures have lower latent heat values which meansmore steam flow can be required to meet a demand.Therefore, raising the set pressure too high can causethe regulator to be undersized. Also, higher down-stream steam pressure may produce greater amountsof flash steam across a steam trap.
Condensate Return SystemSteam flow and condensate return system pressurecan be difficult to determine and sometimes over-looked. The heat transfer equipment manufacturershould be able to provide the exact steam flow require-ments and should be consulted in the design process.When replacing equipment in existing applications,
provide the heat transfer equipment manufacturer withthe equipment's serial number and model number toobtain steam flow information.
When sizing the condensate return system, poundsper hour (kg per hour) of steam flow equals pounds perhour (kg per hour) of condensate produced. Therefore,the steam trap selected must pass the same amount ofcondensate flow as steam flow used in the steamsystem. Remember, system mass is always conservedunless there are leaks in the heat transfer equipment.
Inadequate condensate return systemdesign can cause poor temperaturecontrol.
Installation
Personal injury, equipment damage, orleakage due to escaping steam or burst-ing of pressure-containing parts mayresult if this regulator is overpressured oris installed where service conditionscould exceed the limits given in thespecifications and on the appropriatenameplate, or where conditions exceed
Figure 5. Typical Tank Heating Application Schematic
19B0936E0235
INLET
INTERMEDIATE
TYPE 92B TYPE 92BTBLOCKVALVE STRAINER
BLOCKVALVE
BLOCKVALVE
OUTLET
DRAINVALVE
DRAINVALVE
DRIPTRAP
FLOAT ANDTHERMOSTATICSTEAM TRAP
COLD WATER INLET
HOT WATER TANK
THERMOSTAT BULB
HOT WATEROUTLET
SAFETYRELIEF VALVE
P
P
P
T
T
P = Pressure Gauge
= Temperature Gauge
Types 92BT and 92BTP
6
any pressure or temperature ratings of thedownstream piping components. To avoidsuch injury or damage, provide pressure-relieving or pressure-limiting devices toprevent service conditions from exceed-ing those limits.
Type 92BT and 92BTP installations shouldbe checked for compliance with all appli-cable codes and regulations, such as theANSI B31.1-1977 Power Piping standard orthe ASME Boiler and Pressure Vesselcode, if applicable.
Use qualified personnel when installing, operating, andmaintaining Types 92BT and 92BTP regulators. Makesure that there is no damage to or foreign material inthe regulator and that all tubing and piping are clean andunobstructed. Install the regulator so that the flowdirection matches the arrow found on the regulator body.Figures 5, 6, 7, and 8 show some typical Type 92BTand 92BTP regulator applications.
Handle the temperature pilot body assem-bly with care so as not to kink the capillarytube between the bulb and the pilot body.A kink in the capillary tube can make thetemperature pilot inoperable.
To prevent damage, do not lift or carryregulator or thermostat assembly by thecapillary tubing.
Since a clogged vent may cause improperregulator functioning, install the regulatorso the Type 92T pilot housing and theType 6392 pilot (if used) spring case ventremain clear and unobstructed.
Damage to the thermostat assembly mayrelease the fluid fill which containsapproximately one cubic inch (16,4 cc) ofkerosene or pentane as dictated by fillrequirements.
To prevent condensate buildup, install the regulator sothat condensate can drain from the body. For NPTbodies apply compatible pipe compound to the malepipeline threads and for flanged bodies use acceptableflange gaskets between the regulator and pipe flanges.Then, using acceptable piping procedures, install theregulator into the pipeline.
Figure 6. Typical Air Heating or Air Pre-Heating Application Schematic
19B0397E0236
INLET
TYPE 92BT
BLOCKVALVE
OUTLET
DRAINVALVE
STRAINER
DRIPTRAP
FLOAT ANDTHERMOSTATICSTEAM TRAP
THERMOSTATBULB
P P
OUTLET
T
AIRINLET
HEATED AIROUTLET
STEAM COIL
INLET
T
T
P = Pressure Gauge
= Temperature Gauge
Types 92BT and 92BTP
7
Type 92BT Temperature Regulator(figures 5, 6, 7, and 9)The following is a list of guidelines for installing theType 92BT temperature regulator.
1. Follow proper piping practice when installing theType 92BT in steam service. Install drip traps in theinlet and outlet piping of the regulator as required.Install a strainer to prevent debris from damaging theregulator. Install a steam separator if the steam qualityis poor (~90% or less).
2. Install a three valve bypass to allow for mainte-nance as shown in figure 9, if continuous service isrequired during maintenance.
3. Do not kink or crush the capillary tubing betweenthe bulb and the temperature pilot. This can render thetemperature pilot inoperable requiring replacement ofthe entire temperature pilot body assembly (key 32,figure 13).
4. The temperature pilot body assembly (key 32,figure 13) is shipped in a separate box to protect thecapillary tubing. Install the temperature pilot bodyassembly (key 32) onto the pilot adaptor (key 31) asshown in figure 13 with the four cap screws (key 32m)and gasket (key 32k) provided in the box with thetemperature pilot. The roll pin (key 31a) ensures properalignment of the pilot body assembly and the pilotadaptor.
5. Various options of thermal bulb connection assem-blies are available as shown in figure 15. Each assem-
bly requires the bulb or thermowell of the thermostatassembly to be fully immersed in the process media.Failure to do so can result in poor temperature control.
6. All thermowells should be filled with heat transfercompound prior to placing the bulb in the thermowell.This will improve thermal contact by removing air spacein the thermowell. Johnson Control�s Heat TransferCompound� is recommended, but high temperatureNeversieze� or equivalent can also be used as long asthe compound is compatible with the system's operatingtemperatures.
7. Install a temperature gauge in the process media.Locate the temperature gauge close to the thermostatbulb. The temperature is sensed where the thermostatbulb is located.
8. Inlet and outlet pressure gauges should be installedto monitor pressures on the system components.
9. Prior to startup, ensure the inlet steam piping isfree of debris and condensate by blowing off steam to asafe location through the main inlet strainer or othermethods. Check the strainer, clean as required, andrepeat until strainer is free of debris and condensate.
10. During startup, the regulator may respond withmaximum flow and pressure to meet the heat demandof the unheated process fluid. The temperature pilotdial may require adjustment to obtain the requiredtemperature setpoint after steady state conditions.
11. The temperature pilot has maximum and minimumtemperature values with graduations to approximate
Figure 7. Typical Open Tank Heating Application Schematic
19B0938E0257
BLOCKVALVE
BLOCKVALVE
BLOCKVALVE
BLOCKVALVE
INLET
TYPE 92BT
OUTLET
STRAINER
P P
OPEN TANK
DRIPTRAP
FLOAT ANDTHERMOSTATICSTEAM TRAP
T
STRAINER
STRAINER
T
P = Pressure Gauge
= Temperature Gauge
Types 92BT and 92BTP
8
startup setpoint. Use a temperature gauge to measureactual temperature and to adjust pilot setpoint aftersteady-state operation is attained. This will helpprevent overheating. One method to reduce possibleoverheating is to start with the temperature setpointbelow the desired setting and slowly increase thesetpoint until the desired temperature is achieved.
Type 92BTP Temperature and PressureLimiting Regulator (figures 8 and 10)The following is a list of guidelines for installing theType 92BTP temperature and pressure limiting regulator.The guidelines listed for the Type 92BT temperatureregulator also apply to the Type 92BTP.
The pilot supply and the regulator loading connectionsare normally factory installed as shown in figures 18and 19. The downstream control line must be installedbetween the 1/4-inch NPT pilot body connection andthe downstream system as shown in figure 10.
1. Install the control line connection in a section ofstraight pipe several pipe diameters away from theregulator. Do not locate the control line connection inan elbow, swage, or other area where turbulence orabnormal velocities may occur. This reduces measure-ment of erratic pressures caused by piping components.Also make sure the control line is sloped away from theregulator so that condensate can drain into the pipelineaway from the regulator.
2. Install a pressure gauge in the control line or nearthe regulator to aid in setting the outlet pressure.
3. Install inlet pressure gauge.
4. Install a shutoff valve (not a needle valve) in thecontrol line to completely isolate the pilot duringmaintenance. A needle valve can restrict the smallbleed flow in the control line effecting pressure control.
5. Review the Type 92BTP Startup section beforeadjusting the Type 6392 set pressure. (The temperaturecontrol loop must be open to supply pressure to theType 6392 pilot and allow set pressure adjustment.)
Startup
Type 92BT Startup (figure 9)The maximum inlet pressure for a specific constructionis stamped on the main valve nameplate. Use pressuregauges to monitor upstream and downstream pressuresand a temperature gauge to monitor temperature. Donot exceed the system component pressure andtemperature ratings.
To avoid personal injury, introduce steaminto the system by slowly opening the
Figure 8. Typical Shell and Tube Heat Exchanger Application Schematic
19B0939E0258
INLET
BLOCKVALVE
STRAINER
OUTLET
FLOAT ANDTHERMOSTATICSTEAM TRAP
HEATEXCHANGER
VACUUMBREAKER
SAFETYRELIEF VALVE
P P
TYPE 92BTPTHERMOSTATBULB
T
T
STRAINER
INLET
DRIPTRAP
OUTLET
TYPE 92W
BLOCKVALVE
PROCESSFLUID OUT
CENTRIFUGALPUMP
STRAINER
T
P = Pressure Gauge
= Temperature Gauge
Types 92BT and 92BTP
9
isolation block valves. This will reduce theeffects of destructive waterhammer.
Make sure upstream and downstreamcondensate removal is operational.Condensate can cause erratic temperaturecontrol from poor trap sizing. Personalinjury and/or dangerous equipmentdamage can occur from water hammercaused by movement of condensate.
Pre-Startup Guidelines1. Make sure the thermostat bulb or thermowell is
fully immersed in the process media. Large tanksshould have adequate circulation and mixing to ensureuniform tank temperature.
2. To prevent condensate from flooding heat transfersurfaces, make sure the condensate removal system isinstalled and sized adequately.
3. The heat transfer equipment should be sized withan approach temperature suitable for the process. Theapproach temperature is the difference between steamtemperature and the set temperature of the regulator.As a general rule, an approach temperature of 30°F(17°C) is typical for heating water.
4. A vacuum breaker should be installed to preventa vacuum on the steam side of the heat transferequipment (if required).
5. Ensure a that a temperature gauge is installed inthe process fluid and it is easily viewed from thetemperature pilot's adjusting knob. The temperature
range label on the adjusting knob shows the approxi-mate high and low ends of the temperature range andshould only be used as a guide during startup. Makesure the temperature gauge is installed near the thermo-stat bulb because the bulb is the feedback monitor forprocess media temperature control.
Startup Procedure (figure 9)
To put the regulator into operation:
1. Open all drains in the system (located on strainers,drip legs, and heat exchangers) to allow condensate todrain. This can prevent dangerous water hammer uponsystem startup.
2. For new system startup, perform a blowdown ofthe inlet piping to prevent damage to the regulator.Make sure the drains are piped to a safe location.Close the upstream and downstream block valves.Open the strainer drain valve located upstream of theregulator. Slowly open the upstream block valve forseveral seconds allowing steam to blow-off through thestrainer's drain valve. Close the upstream block valve.Remove the strainer basket. Inspect, clean, and replacethe strainer basket. Repeat this step until the strainerbasket is free of debris.
For existing systems that are being re-started afterseasonal or periodic shutdowns, make sure theregulator, heat transfer equipment, and steam traps areclean and free of condensate. These componentsshould be cleaned and inspected so that they are freeof scale, rust, debris, and condensate that accumulatedduring shutdown periods.
Figure 9. Typical Type 92BT Startup Schematic
E0277
T
P = Pressure Gauge
= Temperature Gauge
DRAINVALVE
INLET
BLOCKVALVE
P
T
TYPE 92BT
STRAINER
DRIPTRAP
BLOCKVALVE
BLOCKVALVE
BLOCKVALVE
THERMOSTAT BULB
Types 92BT and 92BTP
10
3. Open the downstream block valve.
4. Slowly open the upstream block valve while mon-itoring the temperature gauge and system pressures.
5. If a bypass line is used, slowly close the bypassline block valve as the upstream block valve(mentioned in step 4) is being opened.
6. Check the temperature after waiting for steadystate to be established. If necessary, change thetemperature setpoint and wait for steady state.
Type 92BTP Startup (figure 10)The Type 92BTP temperature and pressure limitingregulator requires pressure as well as temperaturesetting to startup. Refer to the Type 92BT Startupsection for temperature setting and the startup guide-lines. Pressure setting steps are outlined in the Pres-sure Setting Adjustment section.
The warning tag above is attached to the adjusting screwof the Type 6392 pressure limiting pilot on a Type 92BTPtemperature and pressure limiting regulator.
Each pressure pilot is factory-set atapproximately the lowest spring rangevalue. Check the spring range to makesure it is correct for the application. (Thepressure range is stamped on the pressurepilot nameplate.) Final pressure adjust-ment may be necessary after steady-stateoperation is attained for best temperaturecontrol. The pressure pilot must not be setabove the allowable system pressure toprevent dangerous pressures.
Pressure Setting Adjustment1. Adjust the temperature pilot several degrees below
its desired set point. This will cause the temperaturepilot to open, providing loading pressure (see figure 4)to the Type 6392 pressure limiting pilot.
2. Adjust the Type 6392 to its desired set pressure byturning the adjusting screw while viewing a downstreampressure gauge. See table 3 for the change in psig(bar) per turn information.
3. Raise the temperature pilot to its desired setpointand monitor the system operation.
4. Repeat as necessary until steady state operation isattained at the desired temperature and pressure.
Figure 10. Typical Type 92BTP Startup Schematic
T
P = Pressure Gauge
= Temperature Gauge
E0278
DRAINVALVE
INLET
BLOCKVALVE
P
TYPE 92BTP
STRAINER
DRIPTRAP
BLOCKVALVE
BLOCKVALVE
BLOCKVALVE
THERMOSTAT BULB
OUTLET
P
T
WARNING!
PERSONAL INJURY COULD RESULT FROMIMPROPER ADJUSTMENT.
REFER TO THE STARTUP SECTION OFPRODUCT INSTRUCTION MANUAL.
Fisher Controls
Types 92BT and 92BTP
11
Shutdown
To shutdown the temperature systemOpen the drains (located on strainers, drip legs, andheat exchangers) to remove condensate. Do not opendrains of pressurized piping unless outlet piping of eachdrain is piped to a safe location.
To take the regulator out of operation1. If a bypass line is used, slowly open the bypass
line block valve while monitoring the downstreampressure and temperature.2. Close the upstream block valve.3. Close the downstream block valve.4. Close the control line shutoff valve, if pressure
limiting pilot is used.5. Open all drain valves as needed to release all
pressure.
MaintenanceRegulator parts are subject to normal wear and must beinspected periodically and replaced as necessary. Thefrequency of inspection and replacement depends uponthe severity of service conditions and upon applicableFederal, State, and local codes and regulations.
Avoid personal injury or property damagefrom release of pressure, high tempera-ture steam, or other process fluid. Beforestarting disassembly:� Isolate the regulator from the processpressure.� Vent all pressures from the main valveand pilot(s).� Allow the regulator to cool to a safetemperature.
This section contains separate maintenance proceduresfor the Type 92B main valve, the Type 92T temperaturepilot, and the Type 6392 pressure limiting pilot.
Type 92B Main Valve (figure 11)The regulator may remain in the pipeline during mainte-nance procedures. The pilot(s) may remain on the mainvalve during maintenance.
Main Valve Disassembly1. Remove all tubing connections from the main valve
(figures 16, 17, 18, and 19).
2. Mark the outside edge of the body and diaphragmcase flanges with assembly marks to ensure properassembly. Remove bolts from diaphragm case and liftoff the case.
3. Take out the diaphragm assembly which consistsof two metal diaphragms (key 60), diaphragm plate plug(key 61), and diaphragm plate (key 59).
4. Remove cap screws from bottom flange (key 52).Take off bottom flange. The valve plug (key 56) andspring (key 57) will drop out.
5. Unscrew the orifice (key 58), if necessary.
6. Remove guide bushings (key 53) from body andbottom flange, if necessary.
Main Valve ReassemblyInspect all internal parts for excessive wear or damage.Use new parts wherever necessary. Reassemble themain valve as follows:
1. Install new guide bushings (key 53) in the body(key 51) and bottom flange (key 52) if old ones wereremoved.
2. Screw in the orifice (key 58).
3. Install valve plug (key 56) and its spring (key 57).
4. Use new bottom flange gasket and replace thebottom flange and cap screws (key 55).
5. Make up the diaphragm assembly by screwing thediaphragm plate plug (key 61) into the diaphragm plate(key 59), clamping the diaphragms (key 60) in place.
6. Put the diaphragm assembly in place on the bodyand replace the diaphragm case (key 62). Make sureassembly marks line up. Replace cap screws and nuts(keys 63 and 64).
7. Reconnect all tubing connections to the main valve(figures 16, 17, 18, and 19).
Types 92BT and 92BTP
12
Type 92T Temperature Pilot(figures 13 and 14)
Parts Inspection and ReplacementUse the following procedure to inspect the seat andlower plug of the stem cartridge assembly for wear, wiredrawing, or scale buildup. To inspect the stem car-tridge, disassemble the thermostat assembly byunscrewing the 1-1/8-inch locknut located below thegreen adjusting knob. Remove the stem cartridgeassembly and clean or replace as required.
1. Unscrew the lock nut (key 32c). Carefully lift offthe subassembly including the adjusting knob (key 32a),thermostat bulb, and capillary tubing. Set it aside (donot disassemble).
2. Pull out the head and guide assembly (key 32f) andthe copper head guide gasket (key 32g).
3. Unscrew and remove the seat (key 32h) and seatgasket (key 32j) using a thin walled 1/2-inch extendedsocket.
4. Apply a high temperature thread sealant to thethreads of the new seat (key 32h).
5. Place the new seat (key 32h) and seat gasket(key 32j) in the temperature pilot body assembly(key 32) and tighten the new seat.
6. Place a new copper head guide gasket (key 32g)into the temperature pilot body assembly (key 32).
7. Place a new head and guide assembly (key 32f),with the ball plug down, into the temperature pilot bodyassembly (key 32).
8. Carefully replace the subassembly which includesthe adjusting knob (key 32a), thermostat bulb, andcapillary tubing. Tighten the lock nut (key 32c).
Screen
To inspect the temperature pilot screen, remove thescreen plug (key 31b) from the temperature pilotadaptor (key 31). Inspect the screen (key 31c) andclean or replace with new screen. Replace the screenplug (key 31b) and tighten.
Pilot Body Assembly Replacement1. Follow the directions in the Shutdown section and
remove the thermostat bulb from the process fluid orthermowell.
2. Remove the four cap screws (key 32m) connectingthe temperature pilot body assembly (key 32) to thetemperature pilot adaptor (key 31).
3. Lift off the temperature pilot body assembly(key 32) and remove the gasket (key 32k).
4. Place the new gasket (key 32k) on top of thetemperature pilot adaptor (key 31). Check that thegasket is aligned with the roll pin (key 31a) and the holepattern in the temperature pilot adaptor.
5. Place the new temperature pilot body assembly(key 32) on top of the gasket (key 32K) and tempera-ture pilot adaptor (key 31). Make sure the temperaturepilot body assembly (key 32) is aligned with the pilotadaptor (key 31) holes and roll pin (key 31a). Thearrows on the side of the pilot body assembly and thepilot adaptor should be aligned when the pilot body is inthe correct position.
6. Insert and tighten the four cap screws (key 32m).
7. Install the thermostat bulb in the process fluid orthermowell and follow directions in the Startup section.
Temperature Pilot CalibrationBefore calibrating, make sure the temperature rangebeing used is appropriate for the application. Calibrationmay be required if the regulator is controlling thetemperature smoothly but the adjusting knob reachesits travel stop before the desired temperature isachieved. Follow these steps to re-adjust the knob:
1. Turn the adjusting knob (key 32a) to its travel stopclosest to the desired temperature.
2. Use a 3/32-inch hex (allen) wrench to loosen theset screw (key 32b) on the adjusting knob (key 32a).Be careful not to move the knob up or down against thecase tube because the pointer could rub against theknob or slide under the travel stop. If the pointer rubsagainst the knob during normal operation, loosen theset screw and raise the adjusting knob 1/8-inch.Tighten the set screw. If the pointer slides under thetravel stop during normal operation, loosen the setscrew and lower the adjusting knob 1/8-inch. Tightenthe set screw.
3. Turn the adjusting knob (key 32a) away from thetravel stop approximately 1/4-inch as measured on thelabel. This will correspond to a temperature adjustmentof approximately 5°F (3°C).
4. Tighten the set screw (key 32b) in the adjustingknob.
Types 92BT and 92BTP
13
Type 6392 Pressure Limiting Pilot(figure 12)Perform this procedure if inspecting, cleaning, or replac-ing any pilot parts. Key numbers refer to figure 12. Allpilot maintenance may be performed with the pilot body(key 1) attached to the main valve.
1. Loosen the jam nut (key 15), and turn the adjustingscrew (key 16) counterclockwise until all compression isremoved from the control spring (key 13).
2. To replace diaphragm, remove the cap screws(key 17), spring case (key 2), control spring, and upperspring seat (key 14) from the body. Remove the lowerspring seat (key 9), the diaphragms (key 7), and thediaphragm gasket (key 8) from the body. Lift out thestem assembly (key 6) consisting of the stem and thepusher plate. Clean the 1/16-inch (1,6 mm) diameterpilot bleed hole. Clean and replace parts as necessary,and assemble the stem assembly, the gasket, thediaphragm, and the spring seat in the order shown infigure 12.
3. Install the control spring (key 13) and spring case(key 2). Insert and tighten the cap screws (key 17).Lubricate the adjusting screw (key 16) tip and threadsthen thread it into the spring case.
4. To replace trim, unscrew the valve plug guide(key 5). Remove the strainer screen (key 12), the valveplug (key 4), the valve plug cap (key 26), and the valveplug spring (key 11). Inspect the seat ring (key 3). Cleanand replace parts as necessary. Apply lubricant to theseat ring threads and metal body seal surface, thenscrew the seat ring into place.
5. Place the valve plug spring (key 11) into the valveplug guide (key 5). Insert the valve plug cap (key 26)into the valve plug (key 4), and then slide both partsover the spring and into the valve plug guide. Place thestrainer screen (key 12) onto the valve plug guide.Apply sealant to the valve plug guide threads and metalbody seal surface, then screw the valve plug guide withthe attached parts into the pilot body (key 1).
Troubleshooting Temperature ControlThe following is a list of possible causes if the regulatordoes not reach set temperature:
1. The thermostat bulb or thermowell may not be fullyimmersed in the process fluid.
2. The heat exchanger surfaces may be fouled orflooded with condensate.
3. The steam trap may be operating below its mini-mum pressure differential.
4. The capillary tubing may be kinked or broken.
5. A failed bellows may have caused the thermostatbulb to loose its fill.
6. Inlet process temperature may have dropped belowacceptable heat exchanger ratings.
7. The tank may not be mixed adequately.
8. A vacuum breaker may need to be installed on theheat exchanger.
9. There is no thermowell compound between thethermowell and the thermostat bulb.
10. The regulator may be operating below its minimumpressure differential.
11. The regulator may be undersized and will not passthe required flow.
The following is a list of possible causes if the controltemperature cycles around the set temperature:
1. The condensate control system may not beoperating properly.
2. Inlet process temperature may be swinging aboveor below the acceptable levels of the heat exchanger'sratings.
3. The tank may not be mixed adequately.
4. Heat exchange surfaces may be fouled or floodedwith condensate.
5. A vacuum breaker may need to be installed on theheat exchanger.
6. There is no thermowell compound between thethermowell and the thermostat bulb.
7. Regulator is operating below its minimum pressuredifferential.
8. The regulator is oversized.
Parts OrderingWhen corresponding with your Fisher Sales Office orSales Representative about this regulator, specify theserial number or fs number found on the regulatornameplate. When ordering replacement parts or partskits, specify the complete 11-character part numbersfound in the following parts list.
Types 92BT and 92BTP
14
Parts List
Type 92B Main Valve (figure 11)Key Description Part Number
31 Pilot Adapter, Cast iron 18B3510X012Includes: 31a - Roll pin, 31b - Screen plug, and 31c - Screen
32 Pilot Body Assembly See table 4Includes:32a - Adjusting knob 32g - Head guide gasket32b - Set screw 32h - Seat32c - Lock nut 32j - Seat gasket32d - Thermowell 32k - Gasket32f - Head and guide 32m - Cap screw
assembly (4 required)
Types 92BT and 92BTP
17
Figure 15. Thermostat Connection Options.Thermostats are available with a standard 8 feet (2,44 m) armored capillary or an optional 15 feet (4,57 m) armored capillary. Each
thermostat has an overheat protection bellows that protects against overheating up to 200°F (93°C) over setpoint, provided the systemtemperature does not exceed 350°F (177°C). Note: Stainless steel thermostatic elements are available upon request.
3/4-inch(19 mm)
5-3/4-inches(15 cm)
3/4-inch NPT
5/8-inch(16 mm)
8-inches(20 cm)
PLAIN COPPER BULB UNION NUT ON COPPER BULB WITH STAINLESS STEEL WELL (STANDARD)
3/4-inch(19 mm)
18-inches(46 cm)
3/4-inch NPT
3/4-inch(19 mm)
5-7/32-inches(13 cm)
3/4-inch NPT
UNION NUT ON COPPER BULB (STANDARD) UNION NUT ON COPPER BULB WITH BRASS EXTENSION WELL
3/4-inch(19 mm)
18-inches(46 cm)
3/4-inch NPT
3/4-inch(19 mm)
5-3/4-inches(14 cm)
3/4-inch NPT
UNION NUT ON COPPER BULB WITH BRASS WELL UNION NUT ON COPPER BULB WITH STAINLESS STEEL EXTENSION WELL
2227102E0082
Mounting Parts (figures 16, 17, 18, and 19)
Type 92BTKey Description Part Number
15 Hex Pipe BushingCopper and brass 1C379026232Stainless steel 1C3790X0012
22 Pipe NippleCopper and brass 1C488226232Stainless steel 1C488238982
29 ConnectorCopper and brass 15A6002X212Stainless steel 15A6002X642
30 ElbowCopper and brass 15A6002X172Stainless steel 15A6002X632
34 Warning Tag - - - - - - - - - - -
Types 92BT and 92BTP
18
Figure 16. Type 92BT Temperature Regulator Assembly with Temperature Pilot Installed in the Up Position
Figure 17. Type 92BT Temperature Regulator Assembly with Temperature Pilot Installed in the Down Position
39B0538E0230
49B0539E0231
Types 92BT and 92BTP
19
Figure 18. Type 92BTP Temperature and Pressure Limiting Regulator Assembly with the Pilots Installed in the Up Position
Figure 19. Type 92BTP Temperature and Pressure Limiting Regulator Assembly with the Pilots Installed in the Down Position
49B0541E0233
39B0548E0232
Types 92BT and 92BTP
Fisher is a mark owned by Fisher Controls International, Inc., a business of Emerson Process Management. The Emerson logo is a trademark and service mark of Emerson Electric Co. All other marks are theproperty of their respective owners.
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, expressor implied, regarding the products or services described herein or their use or 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.
For information, contact Fisher:Marshalltown, Iowa 50158 USAMcKinney, Texas 75070 USA28320 Gallardon, France40013 Castel Maggiore (BO), ItalySao Paulo 05424 BrazilSingapore 128461
