10/29/01,2:16 PM TUNNEL WARM-UPPROC4--HIGHLITED REQUIRED ACTIONS.DOC KIRSNER CONSULTING ENGINEERING

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1 Start-Up Methodology for TSU Tunnel Steam /Condensate System Low Spots. Figure 1 shows an isometric view of the tunnel steam piping system. The steam mains in the tunnel are assumed to slope with the tunnel floor 1 so that condensate within the steam mains tends to drain in the same direction as water runoff along the floor of the tunnel toward UV-2 and out below the tunnel walkin entrance. Thus, with two exceptions, condensate that is not drained from the steam lines eventually flows to the vicinity of the T-4 Trap Assembly at Junction DSA. The two exceptions are the North A steam segment which drains toward T-30 at UV-2 in accordance with the tunnel floor invert; and the North B steam main segment which drains toward the central main at DS-B but, due to the offset of the steam line over the chilled water pipes, cannot drain into the central main line. Figure 1 depicts in blue where condensate will tend to accumulate in the steam mains if not drained. The Critical Trap(s). Note that Trap T-4 is the critical trap in the steam main system in that: (1) it receives condensate from 192 of 12 pipe from the direction of UV-1 and 304 of 10 pipe from west of the trap toward T-5, AND (2) is located at the low point in the system where undrained condensate will tend to accumulate if not drained by the other traps in the mains. If during operation of the steam system in the tunnel, the T-4 trap station can be kept clear of condensate, then all other trap stations should adequately handle their condensate load also. That, in a nutshell, is the start-up strategy. Condensate Backpressure. Condensate lines within the tunnel are normally pressurized by the water column required to lift the condensate roughly 30 feet 2 to the condensate receiver in the Steam Plant. The pressurization of the condensate return (CR) system places a backpressure on steam traps draining condensate from the tunnel steam lines which I estimate should be less than 20 psig 3. At start-up, this backpressure will cause condensate to be retained in the steam mains until steam pressure can build to overcome the condensate backpressure unless condensate is removed by alternate means. During the period traps are disabled by backpressure--which I will term Phase I of the Start-up-- condensate, if it is not drained, will fill drip legs 4 and then overflow to the T-4 trap station (as well as the low points in the north A & B lines). Trap Capacity. The capacity of the traps which are all identical, per SARCO literature for the TLV FS3-10, is slightly under 400#/hr at 90 psid 5 (which equals 110 psig Steam Plant operating pressure 20 psi backpressure). I calculate 6 that the condensate load at 110 psig/ 344 F on T-4 assuming no more than 1% uninsulated pipe is 85 #/hr. Thus, the trap has better than a 4 to 1 safety factor if the 3 insulation covers 99% of the pipe. (If more than 14% of the pipe became bare, the trap will not handle the condensate load). The critical questions to ask for an unsupervised start-up 7 is at what steam pressure could the critical trap handle the condensate load. The table below shows how trap capacity falls off with differential pressure across the trap. At 5 psid/ 25 psig, the trap can handle 100 #/hr of condensate. Trap Capacity #/hr W/ 20 psi backpressure 110 psig psig psid #/hr *manufacturer assumes 11 F subcooling 1 Per Telecom I.C. Thomasson. Drawings requested to verify. I.C. Thomasson cannot locate. Still trying 2 Ditto, footnote 1. 3 Pressure gauge read 20 psi 8 feet above steam line on , i.e psi. Previous reading was 8 psi? (Recommend a pressure and temperature gauge be installed in condensate mains at Junction DSA with communication points to the EMS). 4 Drip legs on the TSU system are very small, holding only about a quart of liquid each so they readily overflow. 5 Psid= pounds per square inch differential pressure 6 See spreadsheet entitled TSU Tunnel Steam Pipe Heat Loss 7 I.E., one where condensate is not drained manually 1

2 Condensate Load. I calculate the condensate load at 25 psig will be 53 #/hr at the critical trap T-4. Thus if my heat transfer presumptions are accurate, at 25 psig (actually 5 psid above the condensate backpressure)- - traps can handle the condensate load being generated in the steam tunnel with a safety factor of 2. The following presumptions were made in the heat transfer calculations: 1. 3 fiberglass insulation covering 99% of pipe being served by T-4 2. Both tunnel ventilation fans on creating a 10 mph breeze at T F in tunnel I calculate that if more than 4% of the pipe being served by T-4 is uninsulated, the T-4 trap will be overcome at 5 psid/25 psig. Therefore, it s paramount to insure pipes stay well insulated. Prior to reaching 5 psid (~25 psig) during warm-up, another method of draining condensate is necessary to keep it from accumulating at low spots in the system. Phase I of Start-Up : 70 F 212 F (0 psig) The steam plant shall admit steam to the steam system at a pressure a few psi above 0 psig after having warmed up the boiler(s) to 212 F. Phase I shall not end until the system is warmed to 212 F as indicated by a reduction in steam flow from the boiler plant and the read out of a temperature sensor near the end of the steam system. Condensate Generated. Over 2,500 # s of condensate (~325 gallons) will form in the tunnel steam mains in warming the steel from 70 F to 212 F not including condensate which forms in the North A & B lines which do not drain into the central steam main. (Not included in this amount is the additional condensate which forms due to heat loss as the pipes warm. This can be substantial where pipes are uninsulated). This condensate must be removed before additional steam flow and pressure is applied to the steam distribution system to warm it the rest of the way to final steam temperature of 344 F at 110 psig. If Trap T-4 had to act alone to remove this condensate after it had all flowed to Junction DSA, I calculate it would take trap T-4 acting alone over 28 hours to drain accumulated condensate 8 after steam pressure was raised above 30 psig (to provide 10 psid of positive pressurization). 8 (See TSU Tunnel Report\CondensateFormation.xls for calculation). Calc does not include condensate formed due to heat loss during period pipes are warming. 2

3 Because this is unacceptable, other provisions have been made to remove condensate during the period traps are inoperable. Thermotons. To help drain condensate at start-up, Sarco Thermotons (pictured above) were provided at trap assemblies in the Summer 1999 Repair of the Tunnel Steam System designed by I.C. Thommason. The thermotons automatically open to discharge condensate to the tunnel floor whenever condensate temperature is less than 212 F 9 -- which it should be during the initial Phase I of start-up. The capacity of thermotons to remove condensate, however, is limited. The CL-6 model provided at TSU has only a 3/8 orifice. At 1 psid (equal to a water head of 2.3 feet with no steam pressure), a thermoton will only discharge about 3.3 # s 10 of condensate a minute or 0.4 gpm. Consequently, unless steam is admitted very slowly to the steam system, condensate can easily overwhelm the capacity of a thermoton to drain it, fill the drip leg, and ultimately flow to the low spot in the system at Junction DSA. Based on the amount of condensate that flows to the nextmost critical trap after T-4 during start-up, the thermoton at T-5 needs as much as an hour to drain condensate during Phase I. If condensate is formed more rapidly, it will overflow the T-5 drip leg toward T-4 at Junction DSA. The T-4 trap station which receives condensate from two directions will take about 1.8 hours to drain just the warm-up condensate it normally receives 11. My guess is that even with a slow and careful start-up employing the thermotons, a substantial amount of condensate from the entire system could overflow trap stations and end up at T-4. If the condensate were allowed to accumulate there, the thermoton at T- 4 would be very slow to drain a large puddle of condensate 12. Manual Verification. Thus, the drain at the T-4 trap assembly as well as those at T-30 and T shall be manually opened at the end of the Phase I warm-up period (as signified by the achievement of 212 F at the end of the steam system) to: (#1) purge any condensate not removed, and (#2) verify that all Phase I condensate has been removed from the steam system. This may be accomplished relatively safely since there is minimum steam pressure in the system. After verification that all condensate is out of the system at each low point, the manual drain may be closed and Phase II of the Start-up may proceed. Air Removal. Another benefit of the thermotons is that they will vent air during warm-up where they have enough time to clear condensate before condensate temperature exceeds their set point. This will be the case at the farthest reaches of the tunnel steam lines. Phase II of Start-up: 212 F 274 F (30 psig) From 70 F to 212 F is a 142 F temp rise. The system has 132 F further to go to warm to 344 F, so during Phase I, just over one-half of the warm-up condensate has been formed and expelled. Above 212 F, Thermotons are closed, so the rest of the condensate to be formed during warm-up about 2400 # s (~300 gallons)-- must be removed by other means. Traps, as discussed earlier, will not remove condensate until the steam pressure exceeds the backpressure in the condensate system which I presume to be not more than 20 psig (based on the height of the riser to the condensate receiver in the steam Plant). Consequently, once it is confirmed that all condensate is drained from Phase I by manually checking for condensate at T-4, steam pressure may be hiked steadily to > 25 psig say 30 psig-- to enable traps to discharge condensate. 9 Temperature setting of thermotons should be verified. 10 See Spreadsheet cell G-19 in Warm-up Condensate 11 If both pipe segments east and west of T-4 drain to T-4, then it receives about 356# of condensate (45 gallons) during warm-up from 70 F to 212 F. At this rate, the thermoton at T-4 would need roughly 356/199= 1.8 hours to discharge all condensate. 12 In the worst case, for example, that one-half of the condensate generated in the entire tunnel steam piping during Phase I, less North A&B, overflowed the drip legs and flowed to T-4, the thermoton at T-4 would require over 6 hours to drain it all at 1 psi head. 13 The thermotons at T-30, T-27, and T-47 should be able to drain condensate accumulated in warming the section of line they serve in.62,.62, and.78 hrs respectively. 3

4 At 30 psig (assuming this is 10 psi above the CR backpressure), the FS3-10 TLV traps will discharge 135 #/hr of condensate about ¼ gpm. T-4, with the greatest condensate load, will receive 156 # s of warm-up condensate in warming from 212 F to 274 F plus roughly 53 #/hr due to heat losses after warming up. The trap can discharge this condensate in less than 2 hours. Thus, the duration of Phase II will be 2 hours. (This time duration could be more than cut in half by replacement of the TLV-FS3 trap with a larger FS5 model). Back-up Bucket Traps. Once again, it is possible that if steam is admitted too quickly to the system, condensate could overflow trap stations and end up at T-4 adding to its condensate load. Thus, to relieve any possible overload at T-4 which could result in a condensate accumulation, a low-pressure high-capacity bucket trap shall be piped in above the T-4 trap in the T-4 trap assembly. The purpose of the bucket will be to discharge any condensate that backs up at T-4. Like the thermotons, the bucket shall discharge to the tunnel floor. But, above 30 psid (~50 psig), the bucket shall be selected to automatically seal closed so it is inactive at normal steam operating pressure. An ARMSTRONG 812 trap with ¼ orifice will discharge 1500 # s of condensate per hour at 10 psid (~30 psig) and seal shut at 30 psid (~50 psig). The bucket will perform the same function as the thermoton in dumping subcooled condensate, but it has 2.4 times the capacity of the thermoton and will remain operable through Phase II of the Start-up Procedure. An additional benefit is that it will speed up Phase I of the Start-up-- the bucket trap will cut the condensate drain time at T-4 in half to less than 1 hour 14. The thermoton at T-4 may be removed from service to simplify the trap assembly. 15 Using the same logic as above, back-up low-pressure bucket traps shall also be installed at T-30 and T- 47. Phase IIIa of Start-up: 274 F(~30 psig) 293 F (60 psig) Increase steam pressure to 60 psig (~40 psid). At 60 psig (40 psid), the trap s capacity increases to 265#/hr. 86 # s of warm-up condensate will form and flow to T-4 during this portion of the warm-up plus condensate generated by heat loss less than 40# s over ½ hour. Condensate can be removed in ½ hour. Phase IIIb of Start-up: 293 F(~60 psig) 344 F (110 psig) At 110psig (90 psid ), trap capacity is almost 400#/hr. Raise steam pressure to 110 psig over the next ¼ hour, allow it to remain at 110 for another ¼ hour. 14 I have not recommended the bucket be used to reduce the duration of Phase II, however, because during Phase II, hot condensate (T> 212 F) would be dumped. 15 An ALTERNATE PLAN is to install a pumped trap at T-4 which can lift condensate the ~45 to the condensate receiver through a dedicated discharge pipe. The pumped trap would act as a regular trap when steam pressure was sufficient to overcome condensate backpressure to expel condensate, but when steam pressure was insufficient, it would be automatically powered by 70 psi air pressure (or an auxiliary steam pressure source) to lift condensate to the condensate receiver. (The air pressure available in the steam plant, I m told, is 100 psig). An advantage of this configuration is that it could avoid dumping some or most of the condensate to the tunnel floor especially if use of the thermotons were abandoned. This could amount to about 2600# s of condensate saved at start-up if the thermotons use were abandoned except for a few at the end of the line for air venting. (Could is in italics since the steam plant dumps most condensate return during start-up due to overfilling of the boilers, so the majority of returned condensate is not recovered). The rest of the condensate would still be emptied by traps once steam pressure exceeded 20 to 30 psig. Like the low-pressure bucket trap, the primary function of the pumped trap would be to act as a backup to catch any condensate not emptied by other traps in the tunnel system (other than those in North A & B lines). It would perform this duty even during normal steam pressure operation (when the bucket trap would be sealed closed by steam pressure). Flow of compressed air to the pump trap could be alarmed and monitored to give a warning when thermotons or traps were not remo ving all condensate formed. The pumped trap solution is more elegant, but is also more costly. An air or steam line would have to be run beneath the street and down the tunnel shaft from the Steam Plant to Junction DSA. I adjudge the additional advantage of the pumped trap to not be worth the extra installation cost. 4

5 At Completion of Warm-up Re-enter Tunnel. (1) To insure no condensate is backed up in steam lines, compare temperature of condensate-filled portion of drip leg at T-30, T-4, and T-47 trap assemblies with steam filled portion using an infrared radiation gun. If temperature of condensate is subcooled compared to steam, a condensate back-up is indicated as shown below. If there is a condensate back up, DO NOT attempt to drain it under full steam pressure. Reduce steam pressure to 0 psig, drain the line, troubleshoot the problem. (2) Close isolation valves upstream of thermotons at each trap assembly to keep them from dribbling condensate. (3) Check for proper contraction of expansion joints and alignment of guides. (4) Check traps for blowing (you ll hear a popping sound) or stopped up traps using the infrared gun. (5) Blow down trap strainers. (6) Open air vents in condensate loops over chilled water pipes at DSA and DSB. Be careful, condensate is hot and under ~20 psig pressure. (These vents should be replaced with automatic air vents or chain pull vents piped away from worker.) Pre-Start-Up Walk-Through Steam Subcooled Steam pipes shall be cleared of water before start-up. The normally closed gate valve located upstream of each Thermoton must be opened prior to start-up to permit the thermoton to drain condensate during start-up. This shall be accomplished during a pre-start-up walk-through of the entire tunnel system to inspect expansion joints, anchors, guides, and condition of insulation as well as open thermoton isolation valves. During walk-through: 1. Expansion joint slips shall be cleaned to bright shiny appearance. Make sure to replace insulation and covers on slips to minimize exposure to environment. 2. Misalignment of guides or joints shall be identified for repair and rectified prior to start-up. 3. After opening thermoton isolation valve, open drains below drip legs to clear drip leg mud accumulation and verify thermoton operation. Close drains. 4. Audit Insulation Condition. Observe condition of insulation and note lineal feet and pipe size where insulation is missing. On pipe segments draining to T-4 at DSA and in the North A line, no more than 1% of the lineal feet of insulation along the length of the pipe shall be missing. No more than 10% of the insulation shall be missing on any other pipe span served by a single trap in the system. If these figures are exceeded, rectify prior to start-up, or adjust start-up procedure. To Trap Assembly 5

6 Recap (Not Finished) Prior to start-up, tunnel entrants shall familiarize themselves with the Tunnel Entry SOP. It states, among other requirements, that the three primary safety systems in the tunnel: the lights, ventilation fans, and communication system must be operational for the Tunnel to be deemed non-hazardous and not permitrequired. The following procedures presume all these systems are fully operational. 1. Preliminary to start-up. Open all isolation gate valves to thermotons through-out the tunnel. Then, open drains from drip legs to clear drip leg mud accumulation and check thermoton operation. Close drains. Make sure to replace insulation and covers on slips to minimize exposure to environment. Clean slips at exp.joints and inspect guides and pipe alignement. Audit insulation. 2. Via telecom, give the steam plant the go ahead to admit steam to the tunnel main to bring the system up to 5 psig and have it dwell there over the span of 1 hour or longer. 3. Steam Plant will hold pressure at minimum level. 4. A steam tunnel qualified maintenance man shall enter the tunnel, travel to UV-1, where he shall observe the operation of the low pressure bucket trap. If it has stopped discharging repeatedly, he shall open the drain at T-3 to insure all condensate has been cleared. If so, he shall close the drain, exit the portion of the tunnel containing the steam main, and radio the steam plant coordinator to slowly raise steam pressure to 30 psig. 5. After 1 hour at 30 psig, steam pressure may be raised slowly over a period of 15 minutes to 110 psig. 6. After start-up is complete (as evidenced by the lack of discharge by the pumped trap, if installed), isolation valves upstream of thermotons at each trap assembly must be closed to keep them from dribbling. The condition of expansion joints and guides should be checked, and traps tested for blowing or stopped up traps. Strainers should also be blown down. 6

7 Figure 1. Isometric View of Tunnel Steam System (Pipe Pitch Based on telecom w/ I.C Thommason. ) Condensate Receiver in Steam Plant Dashed line represents level reference line. Represents a drip leg and trap station UV-1 T-3 12 T-25 ~2500 gal condensate to warm to 212 F T T North A UV-2 T-30 Tunnel Entrance 60,000 cfm from 2 fans North B 792 T-41 T-6 DSB 974 T-7 Slope T-8 T T-10 7