Instruction Manual Form 5474 January 1999
Design CVX-T
Design CVX-T Steam Cooler Introduction Scope of Manual This instruction manual includes installation, maintenance, and operation information for the CON-TEKR Design CVX-T Steam Cooler. Only personnel qualified through training or experience should install, operate, and maintain a Design CVX-T Steam Cooler. If you have any questions about these instructions, contact your Fisher Controls sales office or sales representative before proceeding.
Description
Principle of Operation The Design CVX-T Steam Cooler incorporates a series of cooling nozzles connected by a manifold (figure 2). The cooling nozzles inject water into the steam flow to reduce the steam temperature. Water flow is controlled by an external spraywater control valve (SWCV) whose position is controlled by the output of the temperature control device, which controls the downstream temperature. The nozzles may be of the AF type installed to inject water just inside the pipe wall inside diameter or a series of nozzles installed on
W7352/IL
Figure 1. Design CVX-T Steam Cooler
a lance which extends into the steam piping, depending on the application. The type of nozzles installed in the lance type design may be either AF, fixed orifice, or drilled hole type depending on the application.
Steam Cooler and Instrumentation Installation The Design CVX-T should be located in an easily accessible location and allow sufficient clearance for nozzle removal. Although the preferred position is with the steam flowing vertical up, the Design CVX-T can also be mounted in the horizontal position. Guidelines contained in bulletin 85.1:015 CON-TEKR Steam Conditioning Valves Installation Guidelines may be a useful reference in designing a system that incorporates a Design CVX-T Steam Cooler.
D102623X012
The Design CVX-T Steam Cooler (figure 1) provides an inline desuperheater for applications where insertion style desuperheaters have inadequate capacity. The Design CVX-T can also be manufactured with an integral diffuser for use where backpressure on the pressure control valve is required or desirable. A typical installation is a turbine bypass with inadequate room to install a Design CVX-C steam conditioning valve.
Design CVX-T Table 1. Specifications (for Standard Designs)
End Connection Sizes Design CVX-T: R 1 through 20-inch steam inlet, R 2 through 42-inch steam outlet, and R 1 through 2-inch spraywater ANSI Ratings R Class 150 through 1500 water connection Body R SA105 Carbon Steel R SA182 GR Fl l (1-1/4 CR- 1/2 MO)
R SA182 GR F22 (2-1/4 CR- 1 MO)
Special materials such as F91 or stainless steel possible upon request
Nozzles R SA479 Type 410 (A/F Variable Orifice Nozzles
and Drilled Hole Orifices) R Type 303 SS (Fixed Orifice Nozzles)
Piping Considerations Upstream piping should consist of straight pipe for a distance of five (5) pipe diameters or more from the inlet connection. Downstream straight run piping will be a function of the particular application and respective operating conditions. This distance will be specified by CON-TEK for each individual installation. Pipe reducers or expanders may be used if the inlet and/or outlet size of the Design CVX-T does not match the system piping and the factory has preapproved the use of reducers and expanders. Reducers on the Design CVX-T inlet should have a maximum angle of 30 degrees, while inlet expanders should have a maximum angle between 15 and 20 degrees. Outlet expanders should be limited to between 15 and 20 degrees. These limits have been established to keep noise and vibration levels within an acceptable range. Deviation from these guidelines may occasionally be necessary to accomplish the required turndown.
Location of Temperature Sensor The location of the temperature sensor is dictated by the operating conditions for the application and is shown on the Design CVX-T installation drawing, figure 3. The type of temperature sensor selected can significantly affect the lag time and control parameters of the temperature control loop. Consult the manufacturer of the temperature sensor for details. Mounting of the temperature sensor and transmitter should be in accordance with the manufacturer’s instructions.
Control Strategies The temperature control strategy can be either feedforward or feedback depending on application requirements. A typical closed loop temperature feedback control system (figure 3) is used when there is an accurate and consistent method for temperature mea-
2
W7016-1 / IL
Figure 2. Design DVX-T Steam Cooler with AF Nozzles and Diffuser Section
surement. A temperature feedback control system detects a deviation in setpoint and feeds this information back to the control system to initiate a change in the spraywater control valve (SWCV) position. This control strategy allows very good temperature control within the limitations of the control system response time coupled with the magnitude and speed of the system load changes. A typical feedforward temperature control system is one that responds to input variables other than the downstream temperature to make adjustments in the injected water quantity. Feedforward temperature control is used when it is not possible to get accurate temperature measurement using normal feedback control techniques, when the control temperature is at saturation, when the desired outlet steam condition is below 100%, or when conditions are changing too rapidly to control temperature using traditional feedback methods. Feedback temperature control should be used wherever possible as it is capable of providing the most accu-
Design CVX-T
FISHER 667-EZ SPRAYWATER CONTROL VALVE
SPRAYWATER
TC STEAMFLOW
FISHER CVX-T
TE
B2637 / IL
Figure 3. Typical Design CVX-T Installation
rate temperature control. In general, close coupled turbine bypass systems are the only applications where feedforward control is used without also having feedback control as part of the control strategy.
Installation WARNING Personal injury or equipment damage caused by sudden release of pressure may result if the Design CVX-T is installed where service conditions could exceed the limits noted on the nameplate. To avoid such injury or damage, provide a relief for over-pressure protection as required by government or accepted industry codes and good engineering practices.
Before installation, all piping to the Design CVX-T must be blown clean, so that no particles, such as welding beads, dirt or other foreign matter, are left in the pipeline. Keep foreign matter away from the line openings while preparing the Design CVX-T for installation. Cleanliness of the upstream piping is especially critical in the event that the Design CVX-T is provided with integral diffusers. Debris in the piping can damage the integral diffuser and severely restrict steam flow. 1. Verify that the Design CVX-T is clean inside. 2. Arrange a lifting sling around the Design CVX-T to safely insert it to the pipe opening. 3. Flanged Connections窶認or high temperature applications, grease the flange connection bolts with a high temperature thread lubricant. Install flange gaskets and connection bolts per accepted practices and tighten securely.
3
Design CVX-T CAUTION
STEM BODY SPRING
Re-tighten bolts after the Design CVX-T has been pressurized. Do not expose the Design CVX-T to undue stresses by installing it in bent pipes or flanges. 4. Welded Connections—Welding procedures should be in accordance with the applicable codes and the base materials. For preheat, welding electrodes, and post-weld heat treatment, refer to the standard applicable codes and practices. Materials are specified on the Design CVX-T specification sheet delivered together with the Design CVX-T. For Design CVX-T’s with integral diffusers, the unit should be welded in-line using TIG or similar welding procedures to avoid introducing weld slag into the line. 5. Flush the cooling water line until all debris is removed from the line prior to connecting it to the Design CVX-T. Use only clean sources of cooling water to reduce the possibilities of nozzle clogging. A 100 mesh strainer should be used on the water line as close to the Design CVX-T as possible. Review strainer manufacturers pressure drop curves to determine appropriate strainer body size. It may be necessary to use a strainer that is larger than the water line size if available water pressure is low. 6. A straight run of pipe downstream of the Design CVX-T is necessary to ensure complete vaporization of cooling water. Consult the customer specification sheet for the required straight pipe distance. 7. Typically, a temperature sensor should be mounted a minimum of 30 feet (9.1 meters) downstream of the Design CVX-T. This distance will vary depending on a number of factors including steam velocity and percentage of spraywater. Consult the customer specification sheet provided with the unit for this distance. Contact your Fisher Controls sales representative or sales office if you have any questions. No branch lines should divide the steam flow between the Design CVX-T and the temperature sensor. A typical control loop is shown in figure 3. A temperature sensor (TE) measures changes in temperature and transmits a signal to the temperature control device. The output signal from the control device is sent to the positioner on the cooling water (spraywater) control valve (SWCV). The positioner’s output signal strokes the SWCV open, increasing water pressure on the nozzles. Increasing water pressure upstream of the nozzles initiates water flow through the nozzles.
4
NUT PIN
PLUG
WATER INJECTION HOLES A7191 / IL
Figure 4. AF Nozzle Cross Section
Maintenance Servicing Due to the care Fisher Controls takes in meeting all manufacturing requirements, use only replacement parts manufactured by Fisher Controls.
WARNING Avoid personal injury or damage to property from sudden release of pressurized process fluid. Before starting disassembly, isolate the Design CVX-T from the process and release all process pressure. 1. Loosen and remove the nozzle flange stud nuts (key 58). 2. Remove the nozzle body flange stud washers (key 59) and nozzle body flange (key 20). 3. Remove the nozzle sleeve (key 37) and spray nozzle (key 30). 4. Remove the nozzle sleeve gasket (key 47) and nozzle flange gasket (key 48). 5. Cut the tack weld holding the spray nozzle (key 30) in the nozzle sleeve. Liberally apply a thread lubricant and allow to soak prior to unscrewing the nozzle from the nozzle sleeve (key 37). 6. Replace the spray nozzle and tack with ER410 or other suitable welding rod.
Design CVX-T Table 2. Recommended Bolt Torque BOLT SIZE
THREADS PER INCH
RECOMMENDED BOLT TORQUE(1)
Inch
LbfRft
1/2
13
9/16
12
71 95
5/8
11
125
3/4
10
200
7/8
9
290
1
8
405
1. Torques for lubricated studs with heavy hex nuts.
Table 3. Troubleshooting Guide Problem
Possible Solution Check water source availability and pressure
Temperature setpoint is not reached
Check nozzle(s) for plugging Make sure that steam saturation pressure is not above setpoint Check to ensure full water control valve actuator stroke is reached Check temperature control loop – reset
Temperature Tem erature is below setpoint set oint
Check nozzle for fouling/poor spray pattern – clean/replace Check temperature sensor location – relocate per guidelines
Temperature oscillates around setpoint Water in steam line Water in steam line when steam line isolated
7. Reinstall using reverse order of the disassembly. Use a high temperature grease on the fitting parts to aid in future disassembly. Required torque levels can be found in table 2, Recommended Bolt Torque. 8. If the old nozzles are of the AF type and they are to be inspected and/or cleaned for reuse, refer to figure 4 for guidance. All AF nozzle parts should slide easily and smoothly together. Discard any nozzles that appear marginally operational.
Troubleshooting Table 3 is intended as a basic first line troubleshooting guide. Contact your local Fisher Controls sales office
Tune control system parameters Temperature setpoint may be too close to saturation Check that steam traps are functioning properly Review piping configuration for downstream tees and elbows Check for leakage of spraywater control valve
or sales representative for assistance if you are unable to resolve your field operation problem.
Parts Ordering Each Design CVX-T is assigned a serial number that can be found on the unit. Refer to the serial number when contacting your Fisher Controls sales office or sales representative for technical assistance. When ordering replacement parts, refer to the serial number and key numbers for each part required. The key number in the Parts List and figure 5 can be used to help in part identification.
5
Design CVX-T
B2638 / IL
Figure 5. Design CVX-T Assembly
Parts List
Key 37
Key 01
47*
20
30*
Description Body SA 105 SA 182 Grade F11 SA 182 Grade F22 Nozzle Body Flange SA 105 SA 182 Grade F11 SA 182 Grade F22 Spray Nozzle SA 479 Type 410 or 303, 316 SST
48* 57
58
59
Description Nozzle Sleeve SA 182 Grade F22 Nozzle Sleeve Gasket Inconel 600/Graphite Nozzle Flange Gasket Inconel 600/Graphite Nozzle Flange Stud SA 193 Grade B7, SA105 units SA 193 Grade B16, SA182 GR F11/F22 units Nozzle Flange Stud Nut SA 194 Grade 2H, SA105 units SA 194 Grade 7, SA182 GR F11 and F22 units Nozzle Flange Washer Plated Steel
*Recommended spare parts
CON-TEK, Fisher, Fisher-Rosemount, and Managing The Process Better are marks owned by Fisher Controls International, Inc. or Fisher-Rosemount Systems, Inc. All other marks are the property of their respective owners. RFisher Controls International, Inc. 1999; All Rights Reserved
For information, contact Fisher Controls: Marshalltown, Iowa 50158 USA Cernay 68700 France Sao Paulo 05424 Brazil Singapore 128461 *Recommended spare parts 6 Printed in U.S.A.