12 replies to this topic

[modianurag]

We are manufacturing acidic material (pH around 3.5) in Mild steel glass lined reactor. Current average life achieved of reactor is only about 2 years even with teflon and tantalum plugs.

 

As is experience across different industries, there is tremendous potential for increasing this life up to 10 years.

 

Kindly share your ideas on how to approach this.

 

[sgkim]

Hi Modianurag,

The life of a glass-lined(GL) reactors may be dependent on each service condition.  User guidelines provided by GL equipment manufacturer would be helpful basically.  Along with the basic guidance the following practice from my experience must be kept in mind:

 

  i.  Avoid sudden thermal shock by injecting cold liquid especially on the GL wall around nozzles; use feed nozzle 'insert' extended to drop liquid on the liquid surface. 

  ii. Avoid steam hammering in the jacket or coils.  Hammering would be the most harmful to GL walls; Jackets or coils may be surely filled with cold condensate under vacuum. Complete draining of condensate, and steam purging shall surely be included in the operating sequence before supplying steam.       

  iii. Gas or vapor (either cold or hot) injection to the bulk liquid phase could generate supersonic vibration - use suitable diffuser on the tip of the injection nozzle.

  iv. High temperature alkaline materials, phosphoric acid,etc can usually damage the GL surface gradually during long time service period; periodical surface check is essential.

  v. Initial perfect quality check seems essential - proper mild steam surface treatment, good selection of primer and frit, multiple frit applying to prove the absence of pinholes, complete surface flawlessness tests are to be fulfilled by  the 'good' vendor.      

    

If you have your own particular service features in the GL reactor, introduce them and ask more in detail to discuss and solve the problem with the professionals.  

 

~Stefano

Edited by sgkim, 25 December 2016 - 07:57 PM.

[shvet]

I had been working for ~9 years with this type of reactors and we had the same experience. There is some guide from my and my colleagues' experience:

1. Teflon taps are even better choice than tantalum in spite of tantalum are required by eurocodes. We made teflon taps on lathe. It looked like a big bolt and nut.

2. Glass lined vessels are exposed to high pH alkali solutions. Even short term contact with alkali solutions during polymer removal in my case has a negative impact.

3. They are very very susceptible to quick heating and cooling. Heating/cooling speed in any point shall be no more 1°C per minute. The slower the better.

4. Vessel wall thinkness shall be enough to stay fixed/stationary during vessel transportation and installation. Manufacturers usually save money on steel and you can't get to know that wall is too thin till some cracks/splits appear near lugs.

5. They are suspectible to all kind of strokes. Be sure that repair personnel use wood pad and soft boots. We made special simple wood devices for safe work inside of vessels.

6. Manufacturing quality is important for life time. Glass thikness, glazing, complex quality control - all this is important and you should purchase in proven manufacturers. Of course you can do your own quality control on manufacturer's side and we found some good eurocodes for glass lining but I would recommend to purchase in proven manufacturer instead of domestic quality control by purchaser.

Some manufacturer suggest to try glass lining before sale. We were regularly suggested to try some kind of test probe - a little (finger like) metall glass lined detail. You can put it into reactor hanging on teflon rope or on an existing teflon tap.

Edited by shvet, 22 December 2016 - 01:19 AM.

[modianurag]

Quoting you sir,

 

"Avoid steam hammering in the jacket or coils.  Hammering would be the most harmful to GL walls; Jackets or coils may be surely filled with cold condensate under vacuum. Complete draining of condensate, and steam purging shall surely be included in the operating sequence before supplying steam"

 

We do have issues of hammering. We do drain condensate using bypass valve before injecting steam into jacket. I don't clearly understand steam purging before supplying steam. kindly help me understand.

[modianurag]

 

 

4. Vessel wall thinkness shall be enough to stay fixed/stationary during vessel transportation and installation. Manufacturers usually save money on steel and you can't get to know that wall is too thin till some cracks/splits appear near lugs.

5. They are suspectible to all kind of strokes. Be sure that repair personnel use wood pad and soft boots. We made special simple wood devices for safe work inside of vessels.

 

Thanks for your valuable inputs based on your experience. How do we ensure point no. 4 is not one of the major reasons for glass line failure.

Could so suggest any vendors or drawings of wood pad/soft woods. We do use a wood ladder but that seems to be heavy. Could you share more light on this point.

Edited by modianurag, 22 December 2016 - 07:28 AM.

[sgkim]

"Avoid steam hammering in the jacket or coils.  Hammering would be the most harmful to GL walls; Jackets or coils may be surely filled with cold condensate under vacuum. Complete draining of condensate, and steam purging shall surely be included in the operating sequence before supplying steam"

 

We do have issues of hammering. We do drain condensate using bypass valve before injecting steam into jacket. I don't clearly understand steam purging before supplying steam. kindly help me understand.

 

Especially in cold start, the steam jacket of the GL reactor is usually charged with cold condensate under vacuum.  To avoid steam hammering in that case, the cold condensate shall be drained by breaking the vacuum with a jacket vent valve first, then drain the cold condensate completely through the jacket drain valve (or trap bypass valve), and purge the jacket with steam for a little while  to ensure complete draining of cold condensate.   Live steam discharging through vent and drain valves of jacket indicates the status of 'complete draining of condensate' and some 'initial warming-up' to prevent from steam hammering.    

 

A special care must be taken for the GL reactors charged with cold liquids for cold start.  Even condensate in steam header can rush to the jacket under vacuum and sometimes bring about liquid hammering in the jacket.  Vacuum breaking and condensate draining with warming-up to some degree would be essential before initial supplying of steam to the jacket.   

 

~Stefano

Edited by sgkim, 25 December 2016 - 07:50 PM.

[shvet]

 

 

 

4. Vessel wall thinkness shall be enough to stay fixed/stationary during vessel transportation and installation. Manufacturers usually save money on steel and you can't get to know that wall is too thin till some cracks/splits appear near lugs.

5. They are suspectible to all kind of strokes. Be sure that repair personnel use wood pad and soft boots. We made special simple wood devices for safe work inside of vessels.

 

Thanks for your valuable inputs based on your experience. How do we ensure point no. 4 is not one of the major reasons for glass line failure.

Could so suggest any vendors or drawings of wood pad/soft woods. We do use a wood ladder but that seems to be heavy. Could you share more light on this point.

 

 

4. There is no way you can ensure till cracks/splits appear. We had this situation only once - after vessel was lifted cracks/splits appeared near lugs on vessel head,

5, We used wood ladder the same as you do. Actually I don't think you need any vendor or drawing to made your own wood pad. We made it using 1-2 broken pallets, just improvise.

[modianurag]

 

"Avoid steam hammering in the jacket or coils.  Hammering would be the most harmful to GL walls; Jackets or coils may be surely filled with cold condensate under vacuum. Complete draining of condensate, and steam purging shall surely be included in the operating sequence before supplying steam"

 

We do have issues of hammering. We do drain condensate using bypass valve before injecting steam into jacket. I don't clearly understand steam purging before supplying steam. kindly help me understand.

 

Especially in cold start, the steam jacket of the GL reactor is usually charged with cold condensate under vacuum.  To avoid steam hammering in that case, the cold condensate shall be drained by breaking the vacuum with a jacket vent valve first, then drain the cold condensate completely through the jacket drain valve (or trap bypass valve), and purge the jacket with steam for a little while  to ensure complete draining of cold condensate.   Live steam discharging through vent and drain valves of jacket indicates the status of 'complete draining of condensate' and some 'initial warming-up' to prevent from steam hammering.    

 

A special care must be taken for the GL reactors charged with cold liquids for cold start.  Even condensate in steam header can rush to the jacket under vacuum and sometimes bring about liquid hammering in the jacket.  Vacuum breaking and condensate draining with warming-up to some degree would be essential before initial supplying of steam to the jacket.   

 

~Stefano

 

What difference in temperature would result in liquid hammering?

After heating is done, we cool using 80 degrees water and then with 50 degrees water. We don't vent after heating cycle is completed.

Would this be of any use in our situation?

[breizh]

Hi ,

As suggested above you can download brochures from European manufacturers like De Dietrich and Pfaudler to support your work . Definitely extra care must be taken prior to enter the vessel to prevent additional damages . Some manufacturers are providing "patches" to repair small cracks .

Among the key points , you should consider a control of the thickness of the coating with proper tool ( electrical comb).

For sure thermal shock, vibration , cycle hot/cold will cause damage .

 

my 2 cents

 

Breizh

Edited by breizh, 26 December 2016 - 09:16 AM.

[sgkim]

Modianurag, 

 

modianurag, on 26 Dec 2016 - 2:04 PM, said:

What difference in temperature would result in liquid hammering?

After heating is done, we cool using 80 degrees water and then with 50 degrees water. We don't vent after heating cycle is completed.

Would this be of any use in our situation?

 

(1) Refer to the following for the subject you asked (temperature difference does no matters): http://www.tlv.com/g...nism.html#toc_2

 

(2) Both injecting cold water into the jacket when steam is supplied, and injecting steam when cold water is full inside would surely raise problems; the former will lead to thermal shock, and the latter surely water hammering.  You usually vent the jacket and drain cooling(or tempered) water before and after introducing cooling water, don't you?  

 

~Stefano G Kim  

[modianurag]

 

Modianurag, 

 

modianurag, on 26 Dec 2016 - 2:04 PM, said:

What difference in temperature would result in liquid hammering?

After heating is done, we cool using 80 degrees water and then with 50 degrees water. We don't vent after heating cycle is completed.

Would this be of any use in our situation?

 

(1) Refer to the following for the subject you asked (temperature difference does no matters): http://www.tlv.com/g...nism.html#toc_2

 

(2) Both injecting cold water into the jacket when steam is supplied, and injecting steam when cold water is full inside would surely raise problems; the former will lead to thermal shock, and the latter surely water hammering.  You usually vent the jacket and drain cooling(or tempered) water before and after introducing cooling water, don't you?  

 

~Stefano G Kim  

 

We vent the jacket and then remove water before injecting steam for heating purpose. 

After heating is done, we have an isothermal cycle in which steam if any in jacket condenses. 

Then we start cooling using 80 degrees water.

We don't vent during this step as steam valves are closed after heating is done. Should we do that?

[breizh]

Hi ,

In addition to my previous answer .

Breizh

[sgkim]

(2) Both injecting cold water into the jacket when steam is supplied, and injecting steam when cold water is full inside would surely raise problems; the former will lead to thermal shock, and the latter surely water hammering.  You usually vent the jacket and drain cooling(or tempered) water before and after introducing cooling water, don't you?  

~Stefano G Kim  

 

After heating is done, we have an isothermal cycle in which steam if any in jacket condenses. 

Then we start cooling using 80 degrees water.

We don't vent during this step as steam valves are closed after heating is done. Should we do that?

1) After completion of heating step the steam valve will be closed, but the shell side temperature is sometimes much lower than the supply steam temperature.  Then the jacket side shall surely reach partly vacuum condition due to condensing of residual steam.  Supplying cooling liquid to the jacket under vacuum condition may give liquid hammering due to the liquid rushing to the jacket.    

 

2) After completion of cooling step, the cooling medium shall be full inside the jacket.  Supplying steam to the jacket full of cold liquid may lead to steam hammering. 

 

To avoid the above two cases,  you would rather not risk the hammering problem by draining the residual condensate or cooling medium by opening vent and drain valves.

 

Stefano G Kim

Edited by sgkim, 04 January 2017 - 07:18 PM.