Steaming Crabs

Steaming crabs

Caution: All drawings are conceptual drawings for illustration purposes only and may be incomplete.

In the coastal areas of the Chesapeake Bay and inland water ways the steaming and selling of crabs is a business as is a lot of other coastal areas. There is nothing like a good steamed hot Maryland Blue crab. The question is asked many times how to pipe steam boilers to do the steaming of these scrumptious crustaceans. There are many ways to pipe the boilers but here one of the best piping diagrams I have come across. It came from an old friend named Owen of Baltimore who guided many contractors through piping steam boilers installed for steaming crabs.

We all know when it comes to using a steam boiler for anything other than steam heating the condensate gets put down the drain. That means we add a whole lot of fresh water so the life expectancy of the boiler is greatly reduced. I have a list below of what should be done from sizing to piping which has given us the longest life from a steam boiler than any other diagram I have seen. The original installation may be more expensive but they work better and last longer, so it is worth it to do a better job up front and save $$$ in the long run. This gives us the driest steam for better tasting crabs. Remember our installations affect the taste of the crab and success of our customer.

1.Calculate 32,000 BTU's or 133.3 sq. ft. per bushel of crabs
If you have 5 - 2 bushel pots the boiler requirement is 320,000 BTU's net output or 1333 sq ft of steam
2. Preheat feed water through domestic hot water coil or preferably from an direct fired or indirect water heater
Adding hot water will get rid of oxygen and dissolved solids before entering the boiler.
I would rather do this from am active water heater than a domestic hot water coil in a boiler. I would not use a coil in the boiler used for steaming crabs. As the cold water would be drawn through the coil in the boiler used for steaming crabs it could greatly reduce the steam in the boiler dropping steam pressure and affect the steaming process of the crabs.
If the hot water supply is used only for the boiler feed and not an active hot water device, I would strongxly suggest an air eliminator on the feed line to the boiler. 3. Install at least two boiler risers from the boiler. Make the header as high as possible or use a dropped header on the boiler and system headers.
4. Use as high a riser as possible down to the crab pots
5. Insulate all piping
6. Keep header velocity between 25 and 30 fps
7. Keep system piping velocity below 50 feet per second
8. Clean the boiler well by heating it up and skimming the boiler very well, do not add chemicals.
9. Use a fast feeder for each boiler. Most electronic feeders feed too slow. Consider a M&M 101 electric feeder or equal, or a MM-47-2 mechanical feeder. 10. You will have to add a manual reset LWCO along with the auto-reset LWCO, same applies to the pressure controls 11. Two boilers are more efficient than one as the steaming load changes constantly.

Single Boiler Application

You will notice there seems to be much more piping than normal steam boilers. The reason for this is wet steam will carry less steam temperature. The more piping, direction changes and fittings the steam travels through the more water is extracted. The dryer the steam the faster it moves and lasts in a steam state longer.

Two boiler Application with Seperate Boiler Feeds

You will find this is the most common dual or multiple boiler application If you have boiler flooding situations caused by condensate from the running steam boiler you may have to add the extra steam traps per boil as shown below.

2 Steam Boilers with Water Heater Boiler Make-up

The drawing I received showed the make-up water into a hartford loop. I would not think it matters if it put into the tee where the drain is.

Steam Boiler with Water Heater Boiler Make-up

Caution: All drawings are conceptual drawings for illustration purposes only and may be incomplete.Refer to manufacturers drawing for specific's.

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