2 replies to this topic

[aliadnan]

HI

I have some questions to ask and I hope that I will get the problems solved with the help of people on this forum.

First off all I like to know what are Packaged and Non-Packaged type Boilers? What is the difference between them? Where they are used? (I know about the 2 basic types of Boilers i.e. Fired Tube & Water Tube Boilers, but I have no idea about Packaged % Non-packaged type boilers).

Secondly, I am interested to know how many safety devices are provided on the boilers? Someone told me that if the Heating Surface is below 500 ft2, only 1 safety device is provided and above 500 ft2 2 safety devices are provided. Is this correct? If yes, then please someone can shed some little on this topic.

My thrid question is related to Ice Making Plant. I visited a site where textile chemicals were prepared and to maintain the reaction temperature Ice was used. Ice was made by using Ammonia, which carried heat from the water and the Ammonia was then cooled in U-tubes, on which water was showered. The container in which water was converting into ice was surrounded by salt-water, What is the reason for the salt-water? Can anyone explain the basic concept behind this process. Is this the basic Refrigration process?
I would be very grateful if someone can tell me other processes for Ice making and the advantages and disadvantages of the processes.

Looking forward to your respones. Thanks in advance.

Regards,
Ali

[mbeychok]

Aliadnan:

I will answer your question about packaged boilers. First of all, it is not another type of boiler like a water tube or fire tube boiler. Instead, it is how you purchase a boiler.

You can separately purchase each of the various equipment items for a boiler, such as: the fuel fired steam-generating boiler, the feedwater pumps, the condensate deaerator, the steam drum, the controls, etc. and you can then erect the boiler plant onsite. That would be a "non-packaged boiler" and it would a "field erected boiler".

You can also buy small packaged boilers that have all of the required equipment already connected to each other and contained on a pair of skids and all you have to do is place it in your plant and connect to your supply of electricity, treated feedwater, condensate return, your steam piping, your fuel supply, etc. That would be a "fully packaged boiler".

You can also buy boilers that are between the "fully packaged" and the "non-packaged". Each boiler vendor has their own definition of what a packaged boiler includes and you must question them closely so that you have a thorough understanding of what you are purchasing.

[Art Montemayor]

Ali:

Your questions are sound and basic in nature; however, you’ve concentrated 3 major issues in one thread. This is tough to handle because of the distinct and different nature of the queries. Each should be more than enough for one thread – in other words, it would have been better to handle them in three separate threads. But you succeeded in drawing Milton Beychok’s expert response and, as usual, Milton gave you a first class answer on Boiler specifications as related to scope of work. I'll try to respond to your other two queries.

Your question on boiler safety is a broad one that is best handled in a Hazop-type of atmosphere. For example there are a variety of required safety devices on any one boiler and regardless of what “someone” told you, more than one safety device is recommended for any boiler – regardless of heating surface. For example, to operate any boiler without flame-out protection, over-pressure on the steam side, low and high liquid levels, positive purge prior to initial burner ignition, etc, etc., is a grave error for an engineer to commit. Even a presumed “benign” fire-tube boiler used in a neighborhood laundry, can kill or maim a lot of innocent people if the safety relief device fails, the purge sequence fails upon ignition, or the flame is lost while the natural gas fuel continues to flood into a red-hot refractory chamber. Unsafe or improperly designed boilers in the USA were the main reason why the ASME code was mandated and instituted. A lot of people died before the code became a reality.

There are different manners and techniques in making water ice. The common home refrigerator uses a direct heat transfer from the refrigerant with the ice water in order to make the familiar cubes. However, salt brine has traditionally been employed for many years in making ice blocks when using Ammonia as a refrigerant. The brine acts as an intermediate fluid. I don’t know what type of process you have seen, but the cycle should be well-know by you. You are correct in assuming that the basic process relies on the classical mechanical refrigeration process and is described in almost all recognized Thermodynamics text books.

Art Montemayor