Hot Tip #27 - Effects of Ozone

Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. Ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue. Ozone is very corrosive, it causes damage to the lung's bronchioles and alveoli (air sacs that are important for gas exchange.) Repeated exposure to ozone can inflame lung tissues and cause respiratory infections. Young children and the elderly are most susceptible to high levels of ozone.

In addition to its effects on humans, the corrosive nature of ozone can damage plants and trees. High levels of ozone can destroy agricultural crops and forest vegetation.

No agency of the federal government has approved these devices for use in occupied spaces.

Almost 100% absorption will occur if ozone is injected at a depth of 20 feet into water. No washer is 20 feet deep though. While mixing chambers and injecting it into long runs of pipe help, there is still an amount of ozone that does not get absorbed into the water. Washers that have ozone injected right into the basket have very little absorption!

Most washers equipped with ozone generators (not all) have a fair amount of off-gassing. It doesn't take long for the ozone to fill the air space within the washer and then start "spilling" out.

In Southern California, the ambient ozone level exceeds the federal action levels most all summer days.

If you choose to use ozone, it is highly recommended that you receive approval from your insurance carrier & OSHA. You will also want to enter-lock the ozone generator to an ozone sensor that shuts down the generator when there is any “spilling”.

Hot Tip #26 - Temperature Sticks

At $10.00 each, these may be the best maintenance tool you can purchase!

We have seen laundries that have spent hundreds of dollars on different types of tools to measure process temperatures. Many times the user has become very dissatisfied with their purchase!

Inferred temperature guns are the most common tool that we hear complaints about.

A few users love them; most users have learned that they have very few uses within a laundry.

The operation manual for these guns, it states that they cannot be used on reflective surfaces.

Most of the surfaces we need to measure the temperature have reflective surfaces, such as an iron chest.

Temperature sticks are great! They are cheap, do not require batteries, can’t fail because they were dropped, do not require a skilled operator, and never get out of calibration.

I recommend that every facility have at least two, one at 325 degrees F. and a second at 250 degrees F.

If you are running your boiler at or above 100 PSIG, both temperature sticks will melt when touched to a service that is in contact with steam at boiler pressure. 100 PSIG = 338 degrees F.

For a laundry, that is most of your pre-trap process equipment; steam delivery piping, ironer chest, garment presses, etc.

If your condensate return system is below 15 PSIG (250 F.), which it should be for most laundries; then the second temperature sticks (250 F.) will not melt when touched by this system.

The 325 F temperature stick (stick #1) should melt at the inlet of all steam traps that are operating at boiler pressure. If it does not melt you know that the trap is stuck closed or that the trap is undersized.

The 250 F temperature stick (stick #2) should not melt at the outlet of any steam trap. If it does melt you know that the trap is stuck Opened.

The steam temperature at the inlet of the trap should be > 325 F. at all times.

The temperature of the condensate (measured 6 inches downstream of the trap) should be < 250 F. at all times.

Hot Tip #25 - Unit of thermodynamic energy

The British thermal unit (BTU or Btu) is a unit of energy equal to about 1.06 kilojoules.

It is the amount of energy needed to heat one pound of water one degree Fahrenheit.

Engineers use MMBTU to represent one million (106) BTUs.

A Therm is used to represent 100,000 (105) BTUs.


One boiler horsepower is equal to 33,479 BTUs per hour.

One cubic foot of natural gas is about equal to 980 BTUs.

A 400-pound dryer will have a maximum burner rating of about 25 Therms per hour.

A gallon of diesel fuel has about 138,700 BTUs per US gallon.

A gallon of regular gasoline has about 125,000 BTUs per US gallon.

To heat a small (10,000 gallon) swimming pool from 58 F. to 78 F. requires:

10,000 gallons * 8.34 pounds/gallon * 20 degrees =   1,668,000 BTU’s

Hot Tip #24 - Stain Gauge

How does the strain gauge on my tunnel loading conveyor work?

The strain gauge is one of the most widely used strain measurement sensors. It is a resistive elastic unit whose change in resistance is a function of applied strain.

Where R is the resistance, e is the strain, and S is the strain sensitivity factor of the gage material (gage factor in some books).
Among strain gages, an electric resistance wire strain gage has the advantages of lower cost and being an established product. Thus it is the most commonly used type of device. Other types of strain gages are acoustic, capacitive, inductive, mechanical, optical, piezo-resistive, and semi-conductive.

A wire strain gage is made by a resistor, usually in metal foil form, bonded on an elastic backing. Its principle is based on the fact that the resistance of a wire increases with increasing strain and decreases with decreasing strain, as first reported by Lord Kelvin in 1856.

When the strain gage is attached and bonded well to the surface of an object, the two are considered to deform together. The strain of the strain gage wire along the longitudinal direction is the same as the strain on the surface in the same direction.

Hot Tip #23 - Salt Usage

Are you using too much salt when you regenerate your softeners?

Most laundries are.

A simple check: Salt usage should be between:     

3.1 to 3.6 grains of salt used per grains of hardness removed.   

I round it off to between 3 & 4 grains per grain.

Another way to state that is, that one pound of salt usage should remove between:

1,950 grains of hardness, when regenerating at 15 Lbs of salt per Cu.Ft. of resin and

2,450 grains of hardness, when regenerating at 12 Lbs of salt per Cu.Ft. of resin.

A gallon of brine will have:

Percent saturation        pounds of salt per gallon of brine

95%                    = 2.491

96%                     = 2.522

97%                    = 2.552

98%                    = 2.570

99%                    = 2.616

100%                  = 2.647

Therefore, if you regenerating at 12 pounds of salt per cubic foot of resin and have

25 cubic feet of resin, your brine usage should be

(25 Cu.ft.*12 lbs./cu.ft.) = 300 pounds of salt

(300 Lbs / 2.491 lbs/gallon) = 120.4 gallons of 95% saturated brine needed.

Brine usage should be measured at every regeneration!

If your city water hardness is 10 grains, then you should be regenerating every:

(27,000 grains/cu.ft. at (12 Lbs) * 25 cu.ft / 10 grains/gallon) = 67,500 gallons = 2,450 grains per pound

(29,200 grains/cu.ft. at (15 Lbs) * 25 cu.ft / 10 grains/gallon) = 73,000 gallons = 1,946 grains per pound

Brine usage should be measured at every regeneration!                                          

Did I already state that brine usage should be measured at every regeneration?   It is the best methodology to confirm that regeneration was performed correctly.  Which salt dosage should you regenerate at? That’s a future Hot Tip!

Hot Tip #22 - Boiler Blowdown Exchanger

Boiler blow-down occurs from two different boiler locations. The first location is from the bottom of the boiler water reservoir.

This is known as “bottom blow-down” or “rapid blow-down”. It is usually less than 10 seconds in duration and depending on water quality is performed once or twice per shift.

This blow-down is intended to remove “mud” from the bottom of the boiler. The high velocity and short duration of this blow-down do not make it a good candidate for heat recovery.

The second location is from the top of the boiler water reservoir. This is known as “top blow-down”, “surface blow-down” or “continuous blow-down”.

This method of blow-own is continuous in duration and the volume of blow-down depends on water quality; as determined by boiler water chemical analysis.

This method of blow-down is intended to remove contaminates that are floating on the boiler water surface. The majority of all boiler blow-down water is from this “Surface blow down” method.

I measured a heat exchanger on a 400-horse power boiler that was heating water, which had a flow rate of 2.4 GPM, 90 degrees.

This boiler had fairly clean make-up water and blow-down seemed to be in good control.

At $8.00/MM Btu and 80% thermodynamic efficiency, this exchanger was recovering $1.04 per hour.             

At 4,000 run hours per year, the total savings would be = $4,323 per year.


2.4 GPM * 60 Minutes/Hour * 8.34 pounds/Gallon * 90 degree rise * 4,000 Hours/Year * 4,000 Hours/Year * $8.00/MM Btu / 1,000,000 / 80% efficiency = $4,323/Year.

Note: If an exchanger is to be installed, comply with all safety codes! You do not want to install this wrong!

Hot Tip #21 - Refrigerant Type Compressed Air Dryers

Question: I have a refrigerant air dryer after my compressor. The temperature of the exit air is only “slightly” colder than the inlet air, and yet the dryer seems to be working fine. How is this possible?

Within the compressed air dryer, there are two heat exchangers.

Exchanger # 1 is a compressed air to compressed air heat exchanger.

Exchanger # 2 is a compressed air to refrigerant heat exchanger.

The path of the compressed air flow is:

First, it enters side A of exchanger # 1, exits exchanger # 1, then enters side A of exchanger #2, exits exchanger # 2,

then enters side B of exchanger # 1, then exits exchanger # 1 and exits the dryer.

Approximate temperatures of the heat cycle are:

Entering # 1 A (100 F) Entering # 2 A (60 F)

Entering # 1 B (40 F) Exiting # 1 B (95 F)

When the compressed air exits exchanger # 2 its temperature has been reduced to below the dew point.

At this point, the water drops out and exits the dryer via the water separation trap.

The dry, cold compressed air then enters side B of exchanger # 1 where it absorbs heat energy from the air on side A.

It now exits the dryer at a temperature “slightly” cooler than the entering air.

Hot Tip #20 - Ozone

Instead of adding ozone, it is much cheaper & safer to use a low-pressure high-volume blower to blow atmospheric air into your wash water. The addition of this air seems to have all of the same benefits as the ozone. I do not know if the benefits are due to:

  • The oxygen & ozone that is in the ambient air
  • The increase in mechanical action caused by the injection
  • Or if the injection is causing the wash liquor to become more homogeneous.

I know that you will not get as much ozone into the washer but the increase in O2, a great oxidizer by itself, maybe the cause of wash quality improvement.

A simple calculation comparing the amount of oxygen plus ozone present in your ambient air to the amount of ozone generated by the ozone generator will determine the size of the blower needed. 


  • There are about 5 grams of O2 in a cubic foot of air.
  • Ozone generators are available in many sizes with 30 grams per hour a common size.
  • Ambient ozone is frequently in excess of 100 PPB.
  • Blower output pressure will need to be about 2 PSIG = 4.6 feet of the water column.

Hot Tip #19 - Flash Steam

The percentage of flash steam (by weight) that will be formed when discharging hot condensate to a lower pressure is easily determined by using this formula. The sensible heat (heat of the saturated liquid) of the condensate at the lower pressure is subtracted from the sensible heat at the higher pressure. This number is then divided by the latent heat of the steam at the lower pressure and multiplied by 100 to get a percentage.

SH = Sensible heat in the condensate at higher pressure before discharge
SL = Sensible heat in the condensate at the lower pressure to which discharge takes place
H = Latent heat in the steam at the lower pressure to which the condensate has been discharged


If 100psig hot condensate is discharged to atmospheric pressure, the percentage of flash steam is determined as follows. (It may be helpful to have a copy of the steam tables available for reference.)                                    

Subtract the sensible heat of the condensate at the lower pressure (180 Btu/lb) from the sensible heat of the condensate at the higher pressure (308.8 Btu/lb) and the answer is 128.8 Btu/lb. This figure is divided by the latent heat at the lower pressure (970.3) to yield .133 which, when multiplied by 100, provides an answer of 13.3 percent.

Bonus Hot Tip!

When fly fishing a Montana spring creek, that you have hiked into, remember to drink upstream from the herd

Hot Tip #18 - One More Degree

Frequently when I’m talking to laundry operators or their engineers, I ask them what it would be worth to them if they could recover one more degree with their wastewater heat recovery system. The most common response is “Gee, I don’t know”. When encouraged to make a guess, their response is something like “I bet it’s a lot, maybe several hundred dollars a year”.

Since effort will be needed to recover this one more degree, I think it is important to calculate its’ value, to justify the recovery effort.

The calculation is:

(Pounds of water discharged down the drain yearly)  Divided by (1,000,000) Multiplied by  

(fuel cost, per 1,000,000 BTU’s) Divided by (overall thermodynamic efficiency)


  • Water discharged is about 3% less than water purchased.
  • Multiply gallons by 8.34 to get pounds.
  • If you do not know your overall thermodynamic efficiency and you think you are doing a really good job at controlling fuel usage, use 80%. (read chapter 12 of TRSA’s Textile laundering Handbook)


(30,000,000 gallons per year) X (8.34#/gal) / (1,000,000) X ($11.00 MM BTU) / (80% Eff.) =

$3,440.25 per year. This number will be higher if you are not doing a real good job at controlling fuel usage.

As you can see, there is ample justification to expend effort to recover one more degree.

How many degrees are available for recovery?

If your discharge temperature is constantly within 10 degrees Fahrenheit of your incoming water temperature, you are doing very well! Many plants have reached this level. The best I have seen is a six-degree “cold end approach”.  That plant had 60 F incoming water with a 66 F effluent temperature. It becomes easier as your incoming water temperature increases.