1. Amount of fluid to be heated
2. The type of fluid being heated
3. The starting temperature of the fluid
4. The ending temperature of the fluid
5. The minimum or starting pressure of the fluid
6. The maximum or ending pressure of the fluid

First, let’s define each one of these components. Amount of fluid is the gallons of system volume. This can be obtained either from the system drawings or estimated based on the size of the trunk main of the system and the dimensions of the building. Often, an accurate way to acquire this number is to ask a chemical treatment professional. They can dilute a trace chemical in the system and then measure that dilution, which can be used to extrapolate the system size.

The type of fluid being heated is normally water or a mix of glycol and water. The specific volume of glycol increases with temperature faster than that of water. The difference between the specific volume at the starting and ending temperatures dictates the percentage increase in volume of the fluid. It should be noted that the piping system will also increase in size as it is heated. ASHRAE sizing, and most manufacturers, use a net expansion factor that accounts for the change in specific volumes less the expansion of the piping.

The starting and ending temperatures of the fluid depend on the type of system. For a heating system, the starting temperature is normally ambient, or 70 degrees Fahrenheit. The final temperature is typically your operating temperature, equal to the boiler set point. For a chilled water system, the starting temperature is normally the operating temperature or 30 to 40 degrees Fahrenheit. The final temperature of the chilled water system occurs if the system is allowed to go from operating temperature to ambient. The temperature used for tank sizing is typically 100 degrees Fahrenheit, which is the temperature of a very hot day for most areas.

The minimum starting pressure for the tank depends on the height of the building above the expansion tank location. Starting with a penthouse installation, the pressure of the piping in the top floor installation needs to be 10 psi to ensure proper purging of the air that can collect at high points in the system. This means that the expansion tank located in a penthouse would be set for that same pressure, or 10 psi. As the tank moves downward in the system, an increase of 1 psi is needed for every 2.3 feet from the top. If the tank moves down 80 feet from the top, an additional 80 feet/2.3 feet per psi, or 35 psi more is added. The resulting charge for the tank is 35 psi plus 10 psi (needed at the top) or 45 psi.

The maximum ending pressure is normally set by the “weakest link” of the system. For example, if a boiler, heat exchanger, and air handler have maximum pressures of 100, 150, and 75 psi, respectively, you may be tempted to think the air handler is that “weakest link”. If, however, the air handler is at the top of the piping system, the pressure of a 65 psi increase from 10 psi to 75 psi is allowable. The boiler, if located at ground level where the pressure is 45 PSI to start, can only experience a 55 psi increase before it reaches its maximum rated pressure. A good practice is to allow the maximum pressure to increase by 25 to 35 psi over the initial starting pressure. Consider an operator watching the cycle of the HVAC system; if they observe an increase from 45 psi to 100 psi, they may consider that an abnormally high-pressure swing. Observing a pressure from 45 to 70 PSI is deemed in the eye of most operators as normal, as it does not approach the equipment’s maximum pressure.

The governing equation for sizing any expansion tank is:

Tv=(EF(Vs))/(Pin/P1 -Pin/P2)

Where:

Tv = Tank volume
EF = expansion factor of fluid
Vs = System Volume
Pin = initial or pre-charge pressure (psia)
P1 = starting pressure for system (psia=psig+14.7)
P2 = final pressure for system (psia=psig+14.7)

EF is the expansion factor that equals the percentage difference of the starting and ending specific volume of the fluid, minus the volumetric expansion of the system piping. Expansion factor tables are available from most manufacturers to make this calculation more convenient.

Once you know the tank volume (Tv) you need, you can cross-reference that number with the acceptance volume of expansion tanks in our PDF catalog or our online ordering catalog wesselsvessels.com

You can also download the Wessels Company phone apps or use you web-browser to access free-to-use sizing software by clicking “Size Your Tank Now”

The post How To: Size an Expansion Tank first appeared on Wessels Company.

The WessViewTM bladder integrity monitor from Wessels Company is a quick, at-a-glance indicator letting you know if water has breached your tank’s internal bladder or diaphragm.

The design uses a desiccant that sits on top of a red disk. If the desiccant touches water and dissolves, the bright red disk will start to show. If the tank is charged with an air compressor in the field, the desiccant can turn pink, yellow, brown, or black if the air is moist or contaminated with oil or glycol.

The WessViewTM is replaceable. If you need to replace your WessViewTM, you must make sure you release air pressure from the tank beforehand.

WARNING! Release air pressure from the tank before replacing WessViewTM. Failure to remove air may lead to serious injury or death.

The post How To: Troubleshoot the WessView Bladder Integrity Monitor first appeared on Wessels Company.

The elbow is tightened to the NPT threads of the diffuser. If there is torque created by piping into the elbow, this can cause misalignment and a subsequent air or water leak. To test the tank, first remove the potential torque.

1. Isolate tank from system.
2. Drain water from bladder (ideally there is a drain between the shutoff and the tank.)
3. Break the union to the tank (again, ideally between shut off and tank).
4. Charge air pressure to required pre-charge.
5. Apply soapy solution on lock nut. Tighten until there are no air bubbles.
6. Place piping into union to reintroduce torque (if there was any to begin with).
7. Apply soapy solution to lock nut again. Tighten until there are no air bubbles.
8. Service tank back into operation.

The tightening of the lock nut is in a normal clockwise manner that draws the diffuser down to compress the bladder. The elbow is then threaded to the NPT threads of the diffuser. If the elbow and diffuser spin freely, it has the same effect as loosening up the lock nut. This loosening will result in loss of air charge. The lock nut will require retightening to 60-70 ft-lbs. to re-establish the seal.

The post How To: Check and Repair Leaks at the Bottom System Connection of an Expansion Tank first appeared on Wessels Company.

Wessels manually punches bladder holes to the correct size. However, if a bladder you receive needs modification, you can follow these easy steps to correctly expand the connection opening. The size of the hole will depend on the size of the tank.

Tank Size:                                          Hole for connection:
85 – 130 liters                                    1 inch
200-400 liters                                    1 ½ inch
400+ liters                                         2 inch

Be sure to carefully remove the bottom system connection and use the inside lip to trace a hole centered around the pre-punched hole at the base of the bladder.

The hole can be expanded with either a leather punch or carefully cut with a pair of very sharp shears (gardening shears will work). If using shears, cut along the traced line from the previous step.

WARNING: If the bladder tears or is not cut based on the interior lip of the bottom system connection, the connection will be unable to seal and the bladder will not work properly.

If using a leather punch, make sure it is the correct diameter. Once the correct punch is secured, place a piece of wood large enough to cover the entire hole into the bladder. Place the pre-punched hole over the wood and center the leather punch on top of the bladder hole. Strike the handle of the punch with a mallet until the metal of the leather punch punctures the wood and cuts cleanly through the butyl.

Once the hole is cut, replace the bottom connection, and replace the bladder.

For instructions on replacing a bladder, watch the Step-by-Step Guide Video on Youtube or reference the installation manual.

Please contact the warehouse at 317-888-9800 for more technical information on bladders or hole punching.

The post How To: Punch an Expansion Tank Bladder Hole first appeared on Wessels Company.