Oh I got the heebies
Got the heebie jeebies
I'm talkin' about
Got the heebie jeebie blues.

("Heebie Jeebies," B. Atkins & R.M. Jones, 1926)

 

HEEBIE JEEBIES HAPPEN IN CIRCULATED SYSTEMS

The featured image above shows a simplified flow schematic of a Cooling Water System enclosed in a blue outline.

The industrial Cooling Water System illustrated above is similar to the cooling system in a car. Both systems have a circulating process stream that continuously collects heat and then needs to get rid of the heat.

PTOA Readers and Students already know that the circulating process stream in a car's cooling system is a mixture of water and glycol.

The circulating process stream in the Cooling Water System is chemically treated water.

PTOA Readers and Students will be introduced to many types of gas and liquid circulating streams in the process industries.

Every circulating process stream generates some "icky stuff" that will eventually bring the system down if it is allowed to build up.  

Many lofty names are given to this "icky stuff." The composition of the "icky stuff" is different for each type of circulating system.

A textbook might refer to "icky stuff" with the much more polished sounding "suspended solids" or "heat stable amine salts" in the case of an amine gas sweetening unit.The real, scientific name for the chemical structure of the "icky stuff" could be six or seven syllables long.

The "icky stuff" in your car's circulating oil might be called "gunk." The You-Tube below refers to the icky build up as "elements."

The PTOA chooses to call the "icky stuff" that builds up in any circulating system the totally non-technical nickname "Heebie Jeebies."

If the Heebie Jeebies are allowed to build up, the Process Operator will indeed wallow in the Heebie Jeebie Blues.

 

SIMPLIFIED COOLING WATER SYSTEM SCHEMATIC

PTOA Readers and Students that do not wish to squint should refer to the big picture of a Cooling Water System at the top of this page.

The ISA symbol for a Cooling Tower structure is in the middle of the schematic.

An arrow on the right side shows air entering the louvers of the Cooling Tower. PTOA Readers and Students already know that air enters both sides of the Cooling Tower even though the schematic only shows air flow into the right side.

The Hot Water Return Header brings water to the top of the Cooling Tower (labelled "Return" in the above graphic).

Unfortunately, the Cold Water Supply Header (labelled "Supply" in the above graphic) is not well drawn for new learners. Cold water in the basin of the Cooling Tower flows into the suction of the Cold Water Supply Pump which is labelled "Supply." Additionally unhelpful, the ISA symbol  for the Cold Water Supply Pump is missing the discharge nozzle (an accurately drawn pump would have a discharge nozzle drawn below the word "Supply").

Anyway, the Cold Water Supply Pump discharges cold water into the Supply Header which is labelled "Recirculation-2".

The notation "Recirculation 2" infers that the Cold Water Supply Header separates into two sub-headers that serve the processing facility.

The single shell and tube HEx symbol in the schematic represents many exchangers that are serviced by the cooling water.

The cold water in the Cooling Water system exits the HExes warmer and joins the Hot Water Return Header that flows back to the top of the Cooling Tower.

The cycle of cooling the hot water into cold water is repeated over and over. The cold water is circulated back to the process users in the Supply Header and hot water exits the HExes and  flows back to the Cooling Tower in the Return Header.

 

HOW TO PREVENT HEEBIE JEEBIE BUILDUP

Blowdown Lines and Blowdown Valves

All circulating systems will include a mechanism to either manually or automatically purge out a small portion of the process stream. The purpose of purging is to prevent the build up of Heebie Jeebies.

A valve on a small line will manually or automatically be opened up on a routine basis to intentionally discharge a  small volume of the process stream into the sewer.

The name of this line is universally called "The Blowdown Line" and the valve through which the small volume of process stream is purged is called "The Blowdown Valve."

Process Operators must be careful when manually operating a Blowdown Valve.

The process line can be hot and can have a lot of pressure behind it.  The Process Operator must have proper PPE (Personal Protective Equipment) donned before opening the valve.

FRC clothing and safety glasses with splash guards will protect against debris and hot fluid that blows back at the Operator. Gloves will protect hands. Hearing  protection will help decrease the impact of the high-pitched noise that arises when a large fluid volume tries to squeeze through a small-diameter pipe.

Make Up Water

PTOA Readers and Students have probably already figured out that the volume of Cooling Water dumped to the sewer on a routine basis needs to be made up by a fresh supply of water. Without the addition of a fresh water supply, the Cooling Water System would eventually be drained dry!

All circulation systems will have Make Up Lines to replenish the process stream that is dumped to the sewer.

The Make Up fluid has no Heebie Jeebie build up in it and helps dilute the concentration of Heebie Jeebies in the circulating process stream.

The Make Up fluid will enter the process where it can be easily assimilated into the process. In a liquid system,the fresh Make Up line will enter the process near a pump suction (aka intake). In a gas system the Make Up line will enter the process near a compressor suction.

In the Cooling Water System, the Make-Up is fresh, chemically treated water. The fresh water flows into the basin of the Cooling Water Tower. The  Cold Water Supply Pump draws suction from the basin.

Other Cooling Water System Losses

All circulating systems have the features of Blowdown Lines, Blowdown Valves, and Make-Up fluids.

The Cooling Water Tower has two other losses from the circulating system that are unique to Cooling Tower operations.

Two arrows on the top of the Cooling Tower indicate that  Evaporation Losses and Drift Losses exit the top of the Cooling Tower above the fan and flow into the atmosphere.

Drift Losses are entrained water droplets that manage to get through the mist eliminator and drift up and out of the tower.

Evaporation Losses result from water being evaporated into vapor. Since 80% of the cooling accomplished in the Cooling Tower is done by evaporation, these losses are expected and required to make the Cooling Tower effective in cooling hot water.

PTOA Readers and Students are already experts in understanding that the process of evaporating  a liquid into a vapor requires heat.  The removal of this heat is exactly why the remaining water that trickles down into the basin is cooler and that's why the Cooling Tower has Evaporation Losses.

PTOA Readers and Students have probably already figured out that the volume of Make Up Water required in a Cooling Tower must resupply water that exits the system for all three reasons: Blowdown, Evaporation, and Drift.

 

TERLYN TECH COOLING TOWER YOU-TUBE

A picture is worth a thousand words.  Any PTOA Reader or Student still confused about Cooling Tower operations can access the below You-Tube made by Terlyn Tech.

Please note these differences between the language use in the Terlyn Tech You Tube and the PTOA jargon used in this segment:

• "Heebie Jeebies" are called "elements."
• "Blowdown" is called "bleed-off."
• Air is not shown being drafted through the sides of the Cooling Tower as is done in the real world.

 

Take Home Messages: All circulating systems will build up Heebie Jeebies that will eventually bring the system down if not systematically removed.

All circulating systems will have the following features:

Blowdown lines with Blowdown Valves

Make-Up lines replenishing the system with make up fluids.

Process Operators must wear proper PPE when manual blowdown valves are in use.

Cooling Towers have three sources of system losses: Blowdown, Evaporation Losses, and Drift Losses. These three system losses are replenished with fresh Make Up water.

©2015 PTOA Segment 00040
Process Industry Temperature Changing Equipment

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