Steam & Power Forum RSS Welcome to the steam & power forum, a bulletin board dedicated to power & heating plants, boilers, turbines, steam, HTHW, pressure vessels, HRSG, piping and condensate, combustion including ASME questions and more. 1/22/2018 1:24:55 PM Poppy at Steam & Power Forum RSS 64 150 Re: Steam Drum Safety lifting first... - By: Jim Watts [764] If the settings have been set correctly and I will take that to be true, then the drum safety will lift if there is a pressure drop across the superheater that should not be there.<br />You have discounted overload but have introduced dynamic changes in pressure from the PRV.<br />I will discount superheater fouling from water treatment but you may have temporary pressure drop due to slugs of water from the drum level or a temperature controller that splits steam flow flow with a sticky valve .<br />Sometimes a steam leak from a gland can impinge on the safety valve spring and alter its setting due to temperature.<br /> Fri, 19 Jan 2018 05:00:00 -0300 Re: Air Pre heater leakage - By: Jim Watts [764] Further to my previous answer.<br />I do not think you have a problem with air heater tube leakage.<br />All of your symptoms can occur with substoicometric firing. eg low air.<br /><br />How you got into this position and cant get out of it is the question.<br /><br />My guess is that due to type of fuel you have you are using steam flow air flow ratio control where the ammount of air is matched to the steam flow.<br />One problem that can occur with this system is when the combustion is poor due to low O2 the steam flow drops and the air flow is then reduced further by the auto control. This reduces pressure and the fuel is then increased making everything worse and this continues until some back up limit in the air fuel ratio prevents further air reduction.<br />This lands you where you are. <br />Getting out of it on auto is difficult because if you reduce fuel using pressure control the air will go down as well unless the steam flow increases.<br />You need to put your air on manual and reduce fuel untill combustion is normal.<br />The back up limit need to be set higher to prevent this problem recurring.<br /><br />Do not suddenly increase air to get out of this as the unburnt fuel in your boiler may ignite and cause a serious overpressure in the furnace.<br /><br /><br /> Thu, 18 Jan 2018 21:49:00 -0300 Re: Steam Drum Safety lifting first... - By: Mike [2216] Thanks for your response Jim. <br /><br /><br />The boiler is an older unit and not overloaded as far as steam flow is concerned. She is a 400psi boiler rated for 100 000lb/hr although it is typically operated between 60-70k Ib/hr. Whats happening is when we increase our 600/400 PRV which feeds into the 400# main closer to 400psi, the boiler drum safety tends to lift without the superheater safety lifting. <br />All safeties were inspected &amp; set summer 2017. Thu, 18 Jan 2018 15:07:00 -0300 Re: Air Pre heater leakage - By: Murphy [21] Well you have more issues than an air pre-heater leakage problem, but I think Mr. Watts is spot on for you need professional help to sort out the issues, which is more than one issue. Murphy Wed, 17 Jan 2018 12:48:00 -0300 Re: Air Pre heater leakage - By: Jim Watts [764] You have a very very serious situation.<br />Your boiler is running so short of air it is panting and half extinguishing which drops the furnace pressure and allows more air in from the FD and the seals which are spilling.<br />The air reignites the unburning part of the furnace and causes a puff through to the air heater.<br />You are very close to a furnace explosion.<br /><br />Your load is down because you are not burning the fuel correctly giving low o2 and high unburnt.<br /><br />You have probably got in this position by putting too much fuel in your boiler and should slowly reduce fuel until the pulsations stop . Do this slowly.<br />Your load may go up as you reduce fuel and proper combustion is restored.<br /><br />If you are unhappy with the load you get with stable combustion and proper O2 level call an expert to check your conditions.<br /> Sun, 14 Jan 2018 21:14:00 -0300 Air Pre heater leakage - By: APH leakage [2217] Dear Sir,<br />Boiler capacity is 150 TPH Bagasse Fired Boiler Travelling Grate <br /><br />Problem Facing :-- <br />1. Boiler is not running at rated capacity & max. load 110 TPH .<br />2. Furnace pressure is very high & fluctuation 110 TPH Boiler Load .<br />3. APH humming / Buzzing sound is coming after interval 20 sec . at load 110 TPH & 110 TPH sound is coming continue .<br />4. Unburnt carbon very high .<br />5. Oxygen % is very Low<br />6. SMBC water spillage – As Riddling hopper pressure reach 64 mmwc, start heavy fluctuation every 25-30 sec. <br /><br />we are suspecting the problem in Air Pre heater APH tube leakage . What is your comment .<br /><br />But FD, SA, ID Fan motor is taking normal load . &<br />ESP Flue gas temp. is normal not increasing . <br /><br />pls reply we are facing these problem last 1 year . Sat, 13 Jan 2018 07:21:00 -0300 Re: High Sulfite Residual - By: Jim Watts [764] It now seems clear that the high sulfite in the WHB is caused by increasing dosing to suit extra demand on the High pressure Boiler.<br />With the coincidence of demand increasing with BFP pump operations the likely spotis the pumps.<br />Air cannot get into the pumps directly but there is a path in via gland sealing water.<br />Check the source of the gland cooling water and figure out a way to make sure no Air is being injected.<br /><br />BTW I assume you do not have a spray attemperator as solids should not be injected at the DEA in such a case. Wed, 10 Jan 2018 19:39:00 -0300 Re: High Sulfite Residual - By: Ross [390] You may want to consider the waterside deposits in the 500-psi High Pressure Watertube Boiler is consuming the NaSO3. <br /><br />You have a common NaSO3 injection pump into the DA Tank. All FW Pumps have common Inlet piping. The differences are the pumps, which seem reasonable to rule out. Then we are left with the discharge piping and boilers are the difference.<br /><br />It is not a horrific spot to be in and maybe consider a more comprehensive waterside deposit investigation including the discharge piping wet surfaces.<br /><br />Ross Wed, 10 Jan 2018 15:09:00 -0300 Re: High Sulfite Residual - By: Freeman [2215] After DA, theres main header which suctions of steam pump and electrical pump are connected to it.<br /><br />We measure the sulfite residual in HP and WHRB boilers twice a day and change the sulfite dosing pump stroke based on HP boiler result, we try to keep sulfite residula in HP boiler in range 20-30 ppm. <br />Recently after putting one more steam pump, we had to increase dosing pump stroke for keeping sulfite residula in HP boiler in range 20-30. Wed, 10 Jan 2018 14:19:00 -0300 Re: High Sulfite Residual - By: Ross [390] Maybe you could comment on the piping on the deaerator to the Feed Water Pumps. Does the FW Piping to the Steam Pumps draw DA water from a different outlet in the DA than the Waste Heat Recovery Boiler?<br /><br />Ross Wed, 10 Jan 2018 10:04:00 -0300 Re: High Sulfite Residual - By: Freeman [2215] Thanks for your helpful reply.<br /><br />We have been investigating the reasons of this issue.<br /><br />For boilers, the deaerator is the same but pumps are different. Steam turbine pumps are used for HP boiler and electrical driven pumps are used for WHRB. After investigation we see that after putting in service one more Steam turbine pump for HP boilers, sulfite residual increase again in WHRB.<br /><br />Is that possible that air leakage happens in steam turbine pumps and consume sulfite ?<br /><br />Thanks in advance for your helpful guide! Wed, 10 Jan 2018 06:09:00 -0300 Re: Steam Drum Safety lifting first... - By: Jim Watts [764] Drum Safety lifting can occur if the boiler is overloaded causing high pressure drop over the superheater due to higher flow than designed, you need to reduce outlet pressure if you are doing this and need to overload.<br />If the lifting is occuring with a shutoff of boiler load the settings are uncoordinated and this is a very serious problem as firing can continue with no flow in the superheater and damage will be a very shot time to occur.<br /><br />Setting of safety valve blowdown can sometimes result in the lifting occuring in the correct order but the closing of the drum occuring later than the superheater. This should also be watched out for as the same problem can arise.<br /> <br /> Sun, 7 Jan 2018 02:35:00 -0300 Re: High Sulfite Residual - By: Jim Watts [764] The most likely cause for having too much Sulfite is that you are pumping too much in.<br />However the numbers you present are inconsistent and difficult to diagnose confidently.<br />Your High pressure has the lowest reported chemicals but the highest TDS. This is probably because you are not neutralising the sample to remove OH alkalinity before measuring conductivity. as OH has 3 times the conductivity of other components the actual TDS may be lower than reported. You do not indicate the actual PH and each boiler could be at opposite ends of the range reported.<br />You sulfite units appear to be the result of different procedure as one is reported as SO320 and one as SO380 and who knows what mysteries that represents.<br />It is not clear if there is one DEA or two involved but it is hard to see two different tests required if only one is used.<br />Sulfite decomposition would be different at the different pressures and my be contributing to some of the issue.<br />It would make sense to me to reduce sulphite until you got nearer to the minimum on the HP boiler if they are in fact common feed and obvious if they are not.<br />Running high levels is a waste of money at minimum and tending to problems you dont need.<br />It is also normal to run the TDS in the high pressure boiler lower than the WHRB.<br /> Sun, 7 Jan 2018 02:21:00 -0300 Steam Drum Safety lifting first... - By: Mike [2216] Why would a steam drum safety valve lift before the superheater safety valve? Fri, 5 Jan 2018 05:04:00 -0300 Re: High Sulfite Residual - By: Ross. [390] First, I want to say that large amounts of Sodium Sulfite NaSO3 becomes a contaminate because it will produce foaming and other problems, but foaming is the primary problem.<br /><br />Your 500-psi Water Tube Boiler is seems to have reasonable level of residual Sodium Sulfite NaSO3 remaining in the boiler water. Nice pH too.<br /><br />Your 300-psi Waste Heat Recovery Boiler has twice what I would expect for Sodium Sulfite NaSO3 at ranging 80-ppm to 100-ppm. pH is good so you are getting a good yield. <br /><br />As you probably know Sodium Sulfite NaSO3 does not decompose until around 1800-psi.<br /><br />So, my thoughts are the 500-psi Water Tube Boiler has some troublesome contaminates that are consuming the Sodium Sulfite NaSO3. But I am assuming you are using the same Deaerator, FW Pumps and piping.<br /><br />Hope this helps and Good Luck. Ross<br /> Wed, 3 Jan 2018 09:57:00 -0300 Re: Low pH of Boiler HP water HRSG - By: Jim Watts [764] Since all of your feed and condensate is normal but your boiler water is high in silica conductivity and low in PH and you are pumping in chemicals continuously I would say your problem is in your chemical feed tank.<br />You should not increase silica unless you have stopped blowdown or are pumping it in.<br />Phosphate hideout should increase PH when phosphate goes low.<br />It is possible you are pumping in monosodium phosphate which will reduce PH and may cause hideout at the same time.<br /><br />Increase blowdown to control silica and TDS <br />Change your chemical dosing tank over to a new batch of TSP<br />Vary the load a bit as Murphy suggests Sun, 31 Dec 2017 19:48:00 -0300 High Sulfite Residual - By: Freeman [2215] Hi all,<br />We have two type boiler in our gas processing company, with the following condition:<br /><br />1.High Pressure Boiler P36bar T320 C <br />Blowdown Water: pH10.5-11.5 TDS 500ppm PO430-50 ppm SO320-40 ppm<br /><br />2. Waste Heat Recovery Boiler WHRB:P20 bar T214 C<br />Blowdown Water: pH10.5-11.5 TDS 300ppm PO430-60 ppm SO380-100 ppm<br /><br />Sulfite is injetcted in DA reservoir tank. Although, the feed water of both boilers are the same ph8.3 TDS2ppm and cycle concentration in WHRB is lower than HP boiler but sulfite residual in WHRB are higher than High Pressure Boiler.<br /><br />We re going to find out the reason of high sulfite residual in WHRB, could someone explain whats the reason of this phenomena? The standard limit for sulfite residual is 20-40 pmm, Is this high level sulfite residual in WHRB harmful?<br /><br />Thanks in advance!<br /><br /><br /><br /> Sun, 31 Dec 2017 14:26:00 -0300 Re: Low pH of Boiler HP water HRSG - By: Murphy [21] Your Boiler HP section in your HRSG is experiencing Phosphate Hide-out. To learn if this is Phosphate Hide-out just lower the boiler HRSG firing rate to a low steaming rate then wait and do water treatment tests. I would expect your water treatment readings to right themselves. Your professional water treatment people should help you resolve this.<br />Murphy Sun, 31 Dec 2017 11:53:00 -0300 Low pH of Boiler HP water HRSG - By: Fazal [2214] <br />We have HRSG with three drum LP, IP and HP. Pressure of HP drum is 120. We have facing problem of low pH 5-8 and Low PO4 in HP drum in spite of continuous dosing of Tri Sodium Phosphate. Conductivity of boiler water is also high i.e about 200 us/cm. While Feed, Hot well condensate pH and steam pH is ok. We dosing Ammonia and Hydrazine in feed water system.<br />Beside this Sio2 in both IP and HP Boiler water is higher than Limit i.e above 500-900 ug/l. but Sio2 in feed and in our demi storage is within limit i.e less than 10 ug/l <br />Please solve our this problem that what are the causes that:<br />1. pH and Po4 is not maintaining in HP boiler.<br />2. High conductivity of Boiler water.<br />3. High Sio2 in Boiler water. <br /> Sat, 30 Dec 2017 08:19:00 -0300 Re: Pressure Drop in a Superheater - By: Jim Watts [764] I would think it is reasonable that you have designed and manufactured correctly but the test procedure is wrong.<br />Pressure drop is easy to measure and will be correct however flow is tricky.<br />High pressure drop occurs if actual flow is higher than measured or if the mass flow is correct but density is lower than the flow meter is callibrated for. <br />This would happen if you are measuring the flow while the superheater is at a lower pressure than designed. Tue, 26 Dec 2017 19:22:00 -0300