Solenoid-controlled systems

Transcription

1 olenoid-controlled systems This worksheet and all related files are licensed under the Creative Commons Attribution License, version 1.0. To view a copy of this license, visit or send a letter to Creative Commons, 559 Nathan Abbott Way, tanford, California 94305, UA. The terms and conditions of this license allow for free copying, distribution, and/or modification of all licensed works by the general public. 1

2 Question 1 Questions A burner management system (BM) monitors the status of the flame at the base of this incinerator, to ensure fuel gas does not keep entering the combustion chamber unless there is an established fire to burn it: F-1 INCIRATOR DP Atmosphere DT 1650 o F Res Time 1.5 sec minimum NOTE: 1. Gas safety pipes to extend 10 feet above grade, situated at least 30 feet from any source of ignition. 2. Burner management system supplied by vendor, located in MA4X enclosure at base of incinerator tower. ee drawing for wiring details. (3) - 3" nozzles 90 o apart at elev. 50 6" 67 above grade 1" 1" 1"x1/ AE 35 AE 34 O2 AT 35 O2 AT 34 AIR 34/35 AAH 35 1/ 3. Gas chromatograph supplied by vendor, located in analyzer shack at base of incinerator tower. ee drawing for wiring and tubing details. TIR 36 TAL TAH Rain shield from 24 to 67 Waste stream #1 Dwg T /4" TT TE " above grade thick from grade to 24 0" 3/4" TE TT " TIC 37 Waste stream #2 Dwg T 43 1" F-1 1" Waste stream #3 Dwg T 6"x 6"x 6"x 1" 1" BAL x3/4" 24" MW V 115 Vent (Note 1) V 102 V 101 V PH BE BE 109 PH 110 V V D FV FY b I / P FIC RP GC AT R-485 Modbus 33 (Note 3) Gateway AY 33 From natural gas header Dwg PL 105 PCV 39 BM (Note 2) 44 x1" x1" V 113 Vent (Note 1) FC BM (Note 2) PL 114 Ethernet H2 C2H2 NH3 HNO3 AIR AIR AIR AIR 33a 33b 33c 33d AIR 33e CH4 From fuel gas header Dwg PCV 40 Z FT HART FIQ FY c HART to analog TIR DIR FY a Explain the purpose of solenoid valve V-115, identifying whether it is normally energized () or normally de-energized (NDE). Also, explain the purposes of V-111, V-112, and V-113 in this incinerator control system. file i

3 Question 2 olenoid valve V-92 plays an important role in this compressor inlet separator control system. Level control valve LV-92 opens up when needed to drain liquid out of the boot of the separator vessel, which ideally contains only gas (vapor). Examine this P&ID and then answer the following questions: V-65 COMPREOR INL EPARATOR ize 3 5" ID x 12 0" length DP 450 PIG DT 100 deg F FIR P-8 COMPREOR deg F disch and 175 PID boost pressure 75 AND FL MCFH FY From natural gas source A-3 Dwg. 422 From natural gas source A-2 Dwg x6" 1x6" H 91 Vent stacks 20 above grade I M TIR PIR H L 132 PT FT 75 TE RTD 73 1x8" TG 72 To gas cooling Dwg M From natural gas source A-1 Dwg x6" PV PV PV TT 88 TE RTD 88 PT 89 1x8" 1/ 4" 4" 4" 1" 1 1 Anti-surge XC XA lope 1" V-65 1" lope 1"x1/ 1"x1/ PDT 93 LHH 231 HHLL = 2 6" (ED) HLL = 1 11" NLL = 1 4" LT 92 LG 93 L I / P XY IA 76a 1:1 XY 76b IA PDH PID PDIR H 93 OW FC LV 92 LLL = 0 7" Rod out NDE LIR 92 H L LIC 92 H L JAHH 220 VZE 221 JIR 220 JT 220 M 134 P TE RTD TT PDT " TH 325 deg F 232 P-8 V 92 DE IA VXE VYE RTD RTD TE TE VXE VYE VXE VYE ED To motor controls Dwg Vibration monitor I Bently-Nevada 3300 series H 230 (ee dwg for wiring details) Identify the statuses of V-92 and LV-92 when the separator boot liquid level is at or below the normal level of 1 foot 4 inches. Describe how this system responds to high liquid levels in the separator boot. What will be the consequence of an instrument air supply failure, as it relates to the separator boot liquid level? What will be the consequence of an AC power failure to LIC-92? file i

4 Question 3 This loop sheet shows a pneumatic reactor temperature control system utilizing a solenoid valve to assist in the actuation of process valve TV-: Loop: Reformer reactor #2 temperature o F A 20 PIG Reformer unit shelter TI Reformer unit control room TE TT O b I A 20 PIG TI a I O TIC PI In TH NC C In3 Com TY AC Out5 H N H N E 120 VAC Breaker #4 A 100 PIG TV P ATO 2 1 I 4 TAH A B 12 DE Determine the following, based on a close inspection and analysis of the diagram: The typical status of the output switch contact on TY- (NO or NC) The effect of an AC power loss from breaker #4 The effect of the solenoid becoming plugged or accidently capped by a technician file i

5 Question 4 Determine the normal energization states (e.g. or NDE) of each solenoid valve in this diagram, assuming the process valve needs to be closed when the process is running as it should: FO E IA D Also, determine whether one or both solenoids need to trip in order to make the process valve go to its fail-state. In other words, is this a 1oo2 to trip system, or a 2oo2 to trip system? uppose the ball valve refused to shut off when it should. Identify at least two possible faults that could cause this to happen. uggestions for ocratic discussion uppose the probability of each solenoid valve sticking in its regular operating position instead of tripping when commanded is Calculate the probability of the process valve refusing to trip when commanded as a result of this type of failure. uppose the probability of each solenoid valve sticking in its tripped position instead of going to its regular operating position when commanded is Calculate the probability of the process valve refusing to go to its regular operating position when commanded as a result of this type of failure. uppose the probability of each solenoid valve accidently tripping during regular operation is Calculate the probability of the process valve tripping accidently as a result of this type of failure. file i

6 Question 5 ketch arrows next to each of the two solenoid valves showing the directions of air flow in the energized (E) and de-energized (D) states, assuming both of the solenoid valves must trip in order to force the process valve to go to its fail position (i.e. 2oo2 to trip): NDE A.. A.. file i00982 Question 6 ketch arrows next to each of the two solenoid valves showing the directions of air flow in the energized (E) and de-energized (D) states, assuming the process control valve is supposed to be open in regular operation and close if both of the solenoid valves trip (i.e. 2oo2 to trip): NDE IA FO file i

7 Question 7 This fluid diagram shows the components and connections of a Bettis self-contained hydraulic module used to automatically shut off a line valve on a natural gas pipeline in the e of the pipeline pressure going outside of its limits (either falling below the low-pressure limit or rising above the high-pressure limit): HP gauge Hand pump Accumulator Regulator LP gauge Line valve FC (test) Relief, HP Relief, LP Reset Auto/Man olenoid trip Pressure pilot Identify all spool valve positions, and also trace the direction of oil flow, following a solenoid trip e. file i

8 Question 8 uppose this valve control system has a problem. The control valve (LV-104) does not move to the full-open position as it should when the solenoid is de-energized, although it will move when the 4-20 ma current signal to the I/P transducer is varied while the solenoid is energized: UY-104 DE Vent LY 104 I / P LV-104 A.. Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. no coincidental faults), determining whether or not each fault could independently account for all measurements and symptoms in this circuit. file i04692 Fault Possible Impossible Manual valve in bypass position olenoid coil failed open olenoid coil failed shorted olenoid valve (UY-104) spool stuck olenoid valve (UY-104) plugged Air supply to LY-104 failed 4-20 ma signal wiring to LY-104 failed open 4-20 ma signal wiring to LY-104 failed shorted Control valve (LV-104) stuck 8

9 Answer 1 Answers olenoid V-115 s all actuating air pressure from flow control valve FV- whenever its coil is de-energized. Thus, V-115 is normally energized to maintain actuating air pressure to FV-. olenoids V-111, V-112, and V-113 act to pre fuel gas from reaching the incinerator s burner assembly when the Burner Management ystem (BM) sends a trip signal. V-111 and V-112 are block valves, while V-113 is a bleed ( ) valve, making this a double-block and bleed valve arrangement. A similar solenoid valve arrangement can be seen on the pilot burner gas line with solenoids V-101, V-102, and V-103. Answer 2 Identify the statuses of V-92 and LV-92 when the separator boot liquid level is at or below the normal level of 1 foot 4 inches. LV-92 will be closed, and V-92 s coil will be de-energized. Describe how this system responds to high liquid levels in the separator boot. If LT-92 senses a high liquid level, controller LIC-92 will respond by applying electrical power to V-92. When V-92 actuates, it sends instrument air to the diaphragm actuator of LV-92 to cause that drain valve to open. As LV-92 drains liquid out of the boot, the level sensed by LT-92 decreases over time, eually to a point where controller LIC-92 stops sending power to the coil of V-92. What will be the consequence of an instrument air supply failure, as it relates to the separator boot liquid level? Without instrument air supply (IA), the level drain valve LV-92 can never open and the separator boot liquid level will rise unabated. Eually LHH-231 will detect the high-high level condition and command the Emergency hut-down (ED) system to turn the compressor off in order to avoid damaging that machine. What will be the consequence of an AC power failure to LIC-92? Without AC power to energized the coil of solenoid V-92, the level drain valve LV-92 will never be commanded to open by V-92 and the separator boot liquid level will rise unabated. Eually LHH-231 will detect the high-high level condition and command the Emergency hut-down (ED) system to turn the compressor off in order to avoid damaging that machine. Answer 3 The typical status of the output switch contact on TY- (NO or NC) TY- s output must typically be conducting (switch contacts closed) in order to pass AC power on to the coil of the solenoid valve and maintain its normally energized status. The effect of an AC power loss from breaker #4 the solenoid coil would de-energized, ing air pressure from the input of TV- and causing that process valve to go to its fail (closed) position. The effect of the solenoid becoming plugged or accidently capped by a technician If ever the discrete controller TY- commands the solenoid valve to trip, it would force TV- to hold its position rather than close as it should. 9

10 Answer 4 FO E IA D Answer 5 NDE A.. DE A.. E DE E 10

11 Answer 6 NDE D IA D E E FO Answer 7 HP gauge Hand pump Accumulator Regulator LP gauge Line valve FC (test) Relief, HP Relief, LP Reset Auto/Man olenoid trip Pressure pilot 11

12 Answer 8 Fault Possible Impossible Manual valve in bypass position olenoid coil failed open olenoid coil failed shorted olenoid valve (UY-104) spool stuck olenoid valve (UY-104) plugged Air supply to LY-104 failed 4-20 ma signal wiring to LY-104 failed open 4-20 ma signal wiring to LY-104 failed shorted Control valve (LV-104) stuck 12