noob to steam, lot of issues with the plant

swilder

Hey Guys, i am new to steam, started a new contract as a PM w/a federal govt building in SF CA that uses steam for perimeter radiators and injection into a condenser water loop. The last contractor's engineers were clueless so i know i inherited alot of issues. The issues that I see are:
1. The vacuum pump cannot build any vacuum in the return piping. Does this mean stuck traps? Would this explain steam escaping out of the vent pipe in the vacuum unit almost continuously? Should this vent pipe be piped back into the header rather than into the boiler room?
2. Vacuum pumps cavitate. Are the stuck traps causing too high of a temperature (215F) in the vacuum reservoir causing flashing off in the pumps? I see on the controls that I can choose the vac pumps to run on float or float&vacuum, with stuck traps, should I be running the pumps on float only until I get a handle on the stuck traps?
3. Stuck traps. How exactly does one go about finding which traps are stuck?
4. The condensate return tank continually overflows. No clue about this one, the float switch on the tank looks to be mounted very high - might this be an alarm switch? See the pictures. The site glass is always flooded, this is where the chemical treatment is added and I fear it mostly just goes down the drain instead of into the system.

That is all for now, I would appreciate your insights thanks a lot! NOOB

Jamie Hall

The vent must go to atmosphere. However, the steam (and high temperature) in the condensate return tank is a serious concern, and my first reaction is that the first thing to do is to go after the traps -- all of them -- and find out which ones are not working. Pretty much anything else will be useless without that.

EBEBRATT-Ed

To answer your questions:

#1 Yes, Yes and no
#2 yes and yes run on float
#3 by testing the traps. There are all kinds of trap testing equipment. Ultrasonic, temperature etc
#4 you probably have make up water being introduced to the condensate tank. It could be a self contained float that adds water as needed or there could be a control on the tank that operates a solenoid valve in the water line. Find the city water line and trace it to find out.

You need a good steam guy if you can find one.

I would suggest looking at a bunch of steam traps and finding the mfg of the traps. You can contact them it could be Sarco, Armstrong, Watson Mcdaniel, Hoffman, Barnes and jones etc their are others but those are the most common

They can steer you towards a trap testing program. That is the first step to getting the system in shape.

If you have someone with steam experience you could buy the testing equipment and do this in house. You can buy replacements pars. The two most common suppliers are barnes & Jones in the Boston area or Tunstall Assoc in Chicopee, ma you can google them.

The steam expert on vacuum pumps on this site is @Pumpguy you can send him a message

Those two McDonnell Miller controls in your last picture are #63 controls I think. I would guess the upper one is a high level alarm and the lower one controls your make up water and may shut the feed pumps off on a low water condition.

retiredguy

My advice would be to follow what @EBEBRATT-Ed wrote as a starting point . Also, what is the boiler's operating steam pressure and how large of a system is this. You mentioned a "condenser water loop" , what is that and what is it for; is it a domestic hot water heater, a single tank DA, Please explain. Please show the mfg and model numbers for the large tank in the bottom picture. What is the size of the boilers and how many do they run at a time? Pull the camera back a lot and show the whole tank and related piping and maybe a picture of the boiler room.

swilder

Thank you for your input, keep it coming! Jamie, there is over 500 radiator traps! Ed, do you suppose there is a float on the inside where the soft water line enters the tank at mid point to control the level at half full? A bad float seat would definitely keep the tank overfull. Retiredguy, here is a little background, 350K sq ft. building, 2- 3,500 MBTU Bryan LP boilers running 4# in the header, boiler is around 8#. I have only ever seen one run at a time I assume they are set up for lead lag however. They serve primarily 500 exterior radiators and 2 heat exchangers that inject heat into a condenser water loop that serves interior heat pumps. As stated before system has one duplex vacuum return system pumping into one condensate return tank which pumps into one deaerator tank then into the boilers. Still can't figure out how the level in the condensate return tank is maintained, there seems to be no solenoid valve in the soft water line that goes into the condensate return tank. See the pictures...

condensate return tank plate:

Condensate return tank


DA tank


Boiler room

Intplm.

A company to look into to do the steam traps is TP Tunstall. They have repair kits for most if not all makes of steam traps.

I see a chemical feed pump in the above picture.
Are there any shot feeders to add chemicals as well?
The chemicals are probably not going down the drain as you might expect unless a tank is leaking or an immediate blowdown is close by.

retiredguy

Looking at the pictures that you have posted, I looks like that system may have been engineered reasonably well. That said, I have a few questions and/or observations.

#1; looking at the last picture you posted it looks like the steam line entering that condensate tank does not have any temperature control valve to control the tank temperature. If that is the case, I would shut off that line entirely until a temperature controlled valve could be installed. If there is a temperature controlled valve that is not shown then that valve should be set to keep the water temp at about 180F. That steam line into the tank could be a direct injection steam lance or could be entering a steam coil.

#2; on the other side of the condensate tank, that soft water line looks like it goes into a float device that may be out of adjustment or worn out. Normally a tank like that the water level is maintained at the middle of the tank. If there is no float device controlling the water level, then one needs to be installed. That condensate tank should never be flooded or have steam flowing from it.

#3; The feed water temperature in the deaerator should be about 210F or higher depending on the type of the deaerator that it is.

#4; The fact that the vacuum tank is dumping steam and the pumps cavitating usually means that there are problems in the building steam system. The @Pumpguy could address the vacuum return system. I have worked on a few but he is the expert.

#5; those McDonnel Miller controls on the tank are there to protect the system. The lower control probably shuts down the pumps if the tank water level drops and the upper control probably controls an alarm for high water.

EBEBRATT-Ed

There could be a float control in the tank behind that flange. I would have to see the rest of the make up water piping to rule that out.

Pumpguy

First and foremost, your condensate temperature is too high for vacuum operation.

Doesn't matter what brand or type of vacuum pump, Mother nature's laws of physics just don't permit much if any vacuum in a closed space occupied by hot water. As a practical matter, I would say 175*F would be a max condensate temperature for vacuum operation. As a practical matter, 150*F would be a realistic condensate temperature.

For vacuum operation, the colder the better.

The attached file explains the details.

When a system has condensate returning from perimeter building heat, and hotter condensate from a process, it is recommended that the returns be separated so the vacuum pump only sees low temperature condensate from building heat.

Hope this reply is helpful

The high temperature condensate should be handled separately, pumped back to the boiler feed tank