Failure in Glass lined steel tank

[ashtree]

I work for a Water Utility doing process engineering and water quality control. 12 months ago we commissioned a new treated water reservoir at one of our water plants. It is a Glass lined steel panel construction of about 1million USG capacity and stores potable water. The water is not unusually agressive but runs at a free chlorine level between 1.5 and 3 mg/l.

Over the last three months three lower panels in mid sheet have developed leaks through holes of about 3-5 mm in size. I have not personally had much experience with this style of construction but have seen tanks around of similar construction which still seem serviceable after 40+ years. Such leaks would obviously seem unusual. One appears to be related to internal damage as the glass layer on the outside is cracked radially out from the hole but the others are just holes. The sheets are about 10mm thick and even with a damaged glass layer you would expect that the sheet would not pin hole in 12 months.

Does anybody have a similar experience or offer any suggestions on the cause or solution.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[JStephen]

Check with the manufacturer for starters.
If you have a large area of stainless steel, aluminum, etc. that is electrically connected to a very small exposed area of carbon steel, you can get high corrosion rates- not to say this is happening, but it is one thing to look into. Or a cathodic system with the polarity reversed.

 

[ashtree]

We are currently talking with the manufacturers but i am just trying to see if there is any experience in this elsewhere. As far as i am aware there are no connectiuons with dissimilar metals at the locations where holes have appearred.
Not sure about the cathodic protection system. There is certainly no impressed current system but there may be a sacrificial anode which should not be able to have incorrect polarity.

Thanks for the info though. There are a couple of things to check.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[chicopee]

About posting some pictures. Differing opinions may be rendered.

 

[LittleInch]

If there is a CP system but you don't have good continuity between the plates you might get inadvertent earth currents on the plate finding a discontinuity in the lining. I've seen holes that look like they've been drilled due to simular effects.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ashtree]

A couple of them do look like they have been drilled. One looked like it had been shot with .22 calibre bullet except there was no dent.
Pic attached.

These are two different holes but there is a third one as well. You will notice the other glass failure above the rusted hole. This looks like an impact site.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[ashtree]

Another picture

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[LittleInch]

Any internal pictures / damage to lining?

If each plate is electrically isolated given the level of sealing material visible then some sort of current concentrated at small damage to the internal coating looks a possibility.

You may need to connect each page electrically.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ashtree]

No interior pictures yet.
The tank is still in service at the moment. Just trying to get the heads up on things to look for.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[JStephen]

Those could be bullet impacts where the bullet didn't go all the way through, but broke the coating up on both sides, or bullet penetration plus corrosion.
Low-power bullets won't go through something like that (22, most pistol), 30-06, maybe 223 likely would.

 

[chicopee]

The hole appear to be a bullet hole. The crack is anybody's guess. I don't deal with glass so contact glass firms for course of repair instead of replacement. The end of the crack will need to be drilled to redistribute the stress before repair.

 

[LittleInch]

"Bullet holes"???

Is that actually possible?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bimr]

I work for a Water Utility doing process engineering and water quality control. 12 months ago we commissioned a new treated water reservoir at one of our water plants. It is a Glass lined steel panel construction of about 1million USG capacity and stores potable water. The water is not unusually agressive but runs at a free chlorine level between 1.5 and 3 mg/l.

Over the last three months three lower panels in mid sheet have developed leaks through holes of about 3-5 mm in size. I have not personally had much experience with this style of construction but have seen tanks around of similar construction which still seem serviceable after 40+ years. Such leaks would obviously seem unusual. One appears to be related to internal damage as the glass layer on the outside is cracked radially out from the hole but the others are just holes. The sheets are about 10mm thick and even with a damaged glass layer you would expect that the sheet would not pin hole in 12 months.

Does anybody have a similar experience or offer any suggestions on the cause or solution.

For various reasons, the quality of the coating system used on these bolted steel tanks has declined over the years. After witnessing a number of failures, the firm that I working for decided to specify stainless steel instead of the "glass".

Have not witnessed the tanks failing in as little as a years service, but have witnessed tank coatings in wastewater service failing in only 5-7 years.

Any internal pictures / damage to lining?

If each plate is electrically isolated given the level of sealing material visible then some sort of current concentrated at small damage to the internal coating looks a possibility.

You may need to connect each page electrically.

These tanks use mechanical methods to bond the panels together. The bolting incorporates electrical bonding washers that dig into the metal. Bonding straps are also used. Some of the wastewater tanks incorporate zinc anodes.

 

[JStephen]

""Bullet holes'???

"Is that actually possible?"

Yes it is possible, I haven't explored what it takes. I remember when I was in college, a buddy of mine tried his 30-30 out on a steel plate about a half-inch thick. It made a crater about half-way through but didn't penetrate. Lower-velocity rounds, including most handguns, won't make much of a dent in steel; higher velocity rifles will. I expect a lot of hunting rounds would penetrate 10mm plate. There's probably a lot of research that could be done on Youtube if one cared to do so.

As to whether that's likely- in rural area in the US, entirely plausible that someone would take a shot at the tank "over yonder". If you see the road signs in an area all shot up, that's a good indication. Urban areas- much less likely, and you'd expect to see pistol impacts more than rifle.

It would be very uncommon to have a pit all the way through in one isolated place in a year without something else going on. Dissimilar metals would be suspect. Bullet holes are a possibility, and probably easier to tell what's going on in person than in the photos for that. It would be informative to have a good look at the interior to see if there were other similar failure partway through or not.

 

[Compositepro]

223, 308, and 30-06 will all put holes through 1/2" steel plate.

 

[bimr]

There are a few videos on youtube showing the effects of bullets although the caliber and steel thickness are not mentioned:

Tank1

Tank 2

 

[ashtree]

Just to be clear here these holes have not been caused by bullets.
When i discovered the first one (the one in the picture) i actually looked at it (nervously) and wondered whether it had actually been shot. The hole was circular but a little jagged and as i said about .22 calibre size. Where this is located though it is unlikely that it has been shot given what surrounds the tank. Up higher it might have been but down low is unlikely. When investigating the hole it actually got bigger because of the paper thin material around the hole. There is no denting inwards and a few jagged bits are facing outwards.

We are taking the tank out of service next week for a look inside.



Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[chicopee]

Good thing that it was not tempered glass. About a powdered actuated stud gun making that hole? I've heard that when used such tool have shot projectiles that penetrated wood studs and kill people on construction sites. a coworker had such a tool which at the time, in Ct., required some type of gun permit.

 

[ashtree]

We were able to inspect the tank today.
The internal pictures are not impressive but have attached some.
Had seven failures altogether with 3 yet to come through. All but one were down low in the bottom sheet and had a patch of damaged glass about 3/4 inch or 20mm diameter with the hole through the steel progressively smaller down to a small hole going through the outside.

The tank supplier was with us to give their opinion and expertise. They believe these were all related to construction damage. The fact that the steel rusted through in 12 months is still a concern.

The hole will be bored out and a bolt inserted. This will then be epoxied over and coated with mastic.
Straight forward apparently.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[bimr]

As mentioned above, for various reasons, the quality of the coating system used on these bolted steel tanks has declined over the years. After witnessing a number of failures, the firm that I working for decided to specify stainless steel instead of the "glass".

Another problem with these tanks is the connections. Even if the coating is good on these tanks, the connections are a problem. Each connection includes mechanical methods to bond the panels together. The bolting incorporates electrical bonding washers that dig into the coating and metal. All of the hundreds of bolted locations have to be coated with some type of sealant and gasket to prevent corrosion. The bolts themselves may be covered with plastic caps that may come off leading to corrosion of the bolts.

My experience with these glass tanks caused me to specify stainless steel.