Boiler Sight Glass Erosion

If any of you have been around a boiler sight glass that explodes, I am sure the noise made you jump or else flinch as it sounds like a gunshot. Consider yourself fortunate if you were standing near the glass when it exploded and were not hit in the face or eyes by shards of glass.

Water treatment chemicals are frequently blamed for sight glass explosions when in fact, it is erosion at the base of the glass that is the root cause of the failures. My experience has been with round sight glasses being the most likely to fail. Flat sight glasses are much less prone to fail unless it is accidentally struck by a ladder or some other object.

Sight glass erosion occurs when condensation takes place in the piping connections above the glass. This results in a continuous stream of condensate running down into the glass. Since the liquid in the glass usually contains a high percentage of condensate, very little internal treatment chemicals are in direct contact with the glass itself.

You can identify erosion attack on round sight glasses as there is a thinning on the side near the bottom of the glass. Telltale cracks can sometimes be seen in this area prior to failure. If cracks are noticed, it is time to replace the glass. Flat sight glasses show this effect by thinning or complete removal of the vertical ribs on the glass. Some erosion of the the gage glass occurs when the water column and sight glass are given a blowdown.

To minimize erosion, round sight glasses should be replaced with the more expensive flat glasses. No matter which style of glass used, mica gaskets inserted between the glass and water will help protect the glass from erosion.

Now it is time for a story. The story illustrates the importance of having properly educated personnel who are responsible for maintenance and operation of steam boilers. I was in Illinois at a plant that I was able to sell because of a good relationship my company had with the plant manager. The account was sold with no buy in from the plant personnel as they were basically told that they were going to use our company for water treatment.

Things went well for the first few months and the maintenance manager was very helpful and followed all of our suggestions and recommendations. What I did not know was that he in fact had a deep dislike for being told by the plant manager to use us. When the plant manager left the company, the attitude of the maintenance manger suddenly changed. This became apparent when one of their fire tube boilers had been having sight glass failures on a regular basis (I was never told of this) and he blamed our chemicals when in fact the failures had occurred with the previous company as well. One day, the boiler operator asked me if it was safe to run a boiler without a sight glass. I asked him why he would ask that question. He told me that the sight glass had failed and when he reported it to the maintenance manager, he told him to run the boiler without one as he was never going to buy another sight glass! When I went to the see the maintenance manager, he got angry again and told me to mind my own business. I told him that his insurance inspector would red tag the boiler if he saw that it had a missing sight glass. He looked me in the eye and said, ” Well, we will just have to see about that.” I will let you draw your own conclusions about the total lack of safety and concern. I lost the account shortly after and was not disappointed to see this one go.

Going Cheap Resulted in Bulk Acid Tank Leak

The themes of the next few blogs will discuss safety issues with chemical feed, chemical storage, and boiler operation.

I had a customer back in 1992 that wanted to eliminate handling of heavy 55 gallon drums of 66 Baume sulfuric acid. The drums were located outdoors in a heated chemical building near the cooling tower. During the winter months, it became difficult to move palleted drums through the snow to get them close to the chemical building for transfer.

I brought up the idea of a using a 2000 gallon steel bulk storage tank with containment basin to the customer. He liked the idea and immediately issued a PO for one of our storage tanks.

After a visit to one of my refinery customers, I noticed they had desiccant dryers installed on their tanks as well as high quality tank level sight gauges specific for sulfuric acid. When I mentioned these two items to our equipment manager, he told me, ” They are not really necessary and adding they would be more expensive than the tank itself.” I took his advice on the gauge glass but did recommend the desiccant dryer anyway because I knew that moisture in the tank could cause serious tank wall corrosion at the liquid/air interface. In retrospect, I should have recommended a quality liquid level transmitter.

I became concerned when the tank arrived as the sight level gauge was a cheap piece of heavy wall tubing that was not reinforced to handle the weight of the sulfuric acid. When I asked our equipment manager about the tubing, he said, “Don’t worry about it.”

After the initial 2000 gallon fill of sulfuric acid was made, I visited the plant for a routine service call, and noticed the gauge glass tubing was in the shape of an ‘S’ caused by the weight of the acid. I told the customer (who was not very happy) about this and he went out and valved off the level gauge. This of course defeated the purpose of having it installed in the first place. Every two weeks, the level would be manually checked by an operator with a stick (he was not very happy either and let me know it).

Plant personnel finally adjusted to the inconvenience of measuring the tank level until a few months later when I got another call. This time I was told to immediately come to the plant as there had been an acid spill. The operator decided he was not going to climb on top of the acid tank and measure the liquid level because of ice and snow on top of the tank so he opened the gauge valves and ‘Wham’ the tubing blew off dumping almost 1000 gallons of acid into the containment basin.

When I arrived at the plant, the plant engineer wanted to know what to do with the acid in the containment basin. I gave him two options (neither of which he liked). One was to pump the acid out of the basin into another tank, or neutralize the acid with soda ash and have it hauled away or send it to the municipal sewer system. They decided to neutralize the acid and then called the city sewer plant top let them know what their plans.

The story has a happy ending. The plant purchased an ultrasonic level transmitter and tied it into their building management system and they permanently valved off the sight gauge glass connections.

All of this wasted time and effort would have been avoided if I had made the recommendation to install a level transmitter. Experience is the best teacher.

What Were They Thinking?

Many years ago, I was at a wire mill (it is no longer in business) and was introduced to a young engineer who turned out to be one of the best engineers I had ever worked with. He had only been employed for a short period of time and had already discovered a number of problems at the plant including several safety issues.

He asked me to take a walk with him through the plant and he pointed out a number of problems that had nothing to due with our boiler and cooling water programs however I knew there was something bugging him as we approached one of the cooling towers we were treating.

He told me he had read my last service report regarding the high cooling tower conductivity (over 5000 micro mhos) and my recommendation to inspect the blowdown piping for line blockage as the blowdown water meter did not register flow when the solenoid BD valve was actuated. He stated that a new blowdown line had just been installed a month earlier. The new tower blowdown line was routed underground into a pit which connected to a tunnel at the front of the plant. He told me two of their plumbers inspected the old line and could find no blockage but decided to do as requested and installed a new line.

Before walking any further, he pointed out a large, puddle of water that was located near where the blowdown pipe went underground into the pit. He removed the pit man way cover and the pit was full of water. He then said, he noticed the puddle a few days ago and they had not had any rain since my last visit three weeks ago! He told me that he was going to have the pit pumped out and he was going to personally inspect the underground piping himself.

I received a phone call from him later that afternoon. He told me that the new blowdown line had been terminated underground into a blanked off line which happened to be an old natural gas pipeline! He said in a loud voice ” WHAT WERE THEY THINKING?”

The blowdown line was routed to the city sewer line and the high conductivity problem was solved.

The confused plumbers were very lucky that there was no pressure on the gas line and the line had been previously purged. Good thing OSHA had not been there for an inspection that day. This is one of those stories that sound like fiction but it really did happen.

PTSA and Remote Monitoring Saves the Day!

Greetings everyone. This is the first blog I have created in which I will be discussing ‘Things I Have Seen Over the Years’. I hope you will enjoy the content and are welcome to post comments at the end of the blog.

During startup at a new cooling tower account, 110 gallons of an all organic scale/corrosion inhibitor product containing PTSA was delivered to a mini-bulk storage tank located near the cooling tower. The tower had a concrete basin below ground.

A new tower controller was installed that included pH, conductivity, and PTSA sensors. Chemical feed piping was installed prior to start up however one of the old injection tees and injection nozzles were discarded by the plumbing contractor as well as the old CPVC chemical feed piping where the injectors were located. The customer was anxious to get the program started so it was decided to temporarily feed the inhibitor chemical directly to the tower basin. This turned out to be a big mistake as there was no anti-syphon valve on the discharge tubing.

In the evening, when the service rep got home and used his laptop to access the controller, he noticed a high PTSA alarm. He checked the inhibitor pump relay and discovered that it had been off for several hours. He then looked at the PTSA trend graph and noticed it was continuing to increase! At that point, he realized the inhibitor was siphoning through the pump. A call was placed to the plant operator to remove the inhibitor feed line from the tower basin location and temporarily place it in the mini-bulk tank.

The rep visited the plant the next day with the new anti-syphon valve and injection nozzle and after installation, inhibitor feed was safely resumed. If it was not for the PTSA and remote monitoring capability of the controller, the entire 110 gallons of inhibitor could have been added to the system in less than 24 hours. Not a good way to start a new program with a new customer!