How Much Do Buffer Tanks Cost?
8 min read
Are you engineering chilled water or heating water system that needs additional volume in the circuit? A practical solution is to incorporate a buffer tank into the system. Or perhaps you’re looking to buy a buffer tank for a chilled or heating water system you are installing.
In the old days, you would have to engage a pressure vessel engineer to firstly draw up what you needed. Then you would dial up your local steel fabricator and fax or deliver to him the certified drawing of what you needed.
Steel fabricators are mostly busy on their machines, so time was needed before you would hear back from him with a price. The time and cost involved to just get a price were frustrating. Lead times would often blow out too.
Once the tank was delivered to the site, the mechanical contractor would then have to engage an insulation company to insulate and clad the tank, which further delayed the installation process and affected other trades operating within the plant room.
Masterflow learnt of this in early 2005 and set out to alleviate these pains in the industry. Following a process of meticulous planning, design and consultation with engineers and installers across the market, the outcome was a standard range of fully certified buffer tanks branded AQUAZONE, that were:
- Designed to AS1210
- Manufactured to AS1210
- Pre-insulated in accordance with the National Code of Compliance (NCC), formerly the Building Code of Australia (BCA).
- Cladded
- Sufficiently packaged to protect against any damage during transit and onsite rigging.
- In stock, in the core capacity range of 300L to 5,000L.
Thus the frustration of having to deal with multiple parties and wait for answers just to get a buffer tank cost was now a pain of the past.
So exactly how do you determine the cost of a buffer tank? By the end of this article, you’ll have the answer to this question and understand what factors affect the price of buffer tanks. Firstly, we will consider what factors drive the cost of a buffer tank up.
What factors drive the cost of a buffer tank up?
Tank Capacity
This is the first detail you need to work out the cost of a buffer tank. Generally speaking, the greater the capacity, the greater the cost. It is possible for a smaller capacity tank to be more expensive than a larger tank. That is because there are other factors that can affect the cost which we’ll drill into below.
Tank Design Pressure
Once you know what volume buffer tank you need, the next key aspect to consider is the Pressure. If you are installing the buffer tank on the flow side of the circuit, then likely it needs to be suitable for the pump delivery pressure + the static pressure of the system + safety margin. But if it is going on the return loop, which is mostly where they are installed, then you need only consider the static pressure + safety margin.
There are 3 different pressure values:
- Operating Pressure or Design Pressure. This is the normal operating pressure of the system where the tank will be installed. When all equipment is operating to peak performance, what is the pressure.
- Working Pressure. Sometimes also referred to as Maximum Working Pressure particularly in the pumping world, this is the total pressure the system would see if all equipment was running at full speed and shut head.
- Test Pressure. Test Pressure might also be referred to as Hydrostatic Test Pressure, and it is 1.5 times the working pressure. AS1210 dictates this should be 1.43 times the working pressure.
When talking to a pressure vessel manufacturer such as Masterflow, it is important you communicate your required design pressure and if known the max working pressure of the system. Failure to do this could mean a low cost tank but with pressure rating too low for your system. On the converse, the outcome might be an expensive tank because the pressure rating is well in excess of what the system requires.
So the higher the max working pressure required of the tank, the thicker the steel needs to be and sometimes the grade of steel will vary. A 1000kPa rated tank will require thicker steel than a 500kPa tank, and a 3000kPa rated tank will likely need to be made from a tougher grade of material than a 1000kPa tank.
Concerning Test Pressure as defined in (3) above, if the supplier you speak with is a specialist in AS1210 pressure vessel design, they will know what the test pressure should be.
Material of Construction
For the majority of installations, mild steel or carbon steel buffer tanks are sufficient. But if the application fits into any of the below, then stainless steel might be necessary and therefore more costly.
- Industrial Process water.
- Glycol system.
- Corrosive Liquids.
- Domestic water / potable drinking water.
- Site is within close proximity to the coast.
- Temperature is in excess of 95degC.
- Pressure is over 3000kPa.
- Corrosive environment.
Hazard Level
AS1210, the Australian Standard for pressure vessels is also widely recognized outside Australia too such as PNG, New Zealand, Fiji, UAE and other countries. In AS1210 it references AS4343, which is the standard that spells out what hazard levels are. The pressure, temperautre, capacity and application all play into defining the hazard level of your tank. Herewith is a table from AS4343 summarizing the 5 different hazard levels:
For the majority of HVAC chilled water installations, buffer tanks fall into Hazard Level E. In some instances, the HVAC application may require a Hazard Level D tank. The higher the Hazard Level, the higher the capital cost of the buffer tank and the ongoing costs to satisfy regulatory 3rd party oversight.
Tank Diameter
The cost of a pressure tank is largely governed by its diameter.
The greater the diameter, the higher the cost. This is mostly due to the following 4 factors:
- An increase in diameter requires an increase in material thickness to maintain structural integrity and achieve the desired pressure rating. A tank that is 2000mm in diameter must be designed and fabricated from thicker steel than a similar size tank capacity that is only 1000mm in diameter but rated to the same pressure.
- Tank diameters over 2300mm become a logistical challenge, and so it is often more costly to transport tanks over this diameter. Road traffic authorities and their regulations may vary from one region to another, but a tank over 3.3m in diameter for instance might require a special oversized truck and police escort to transport from the manufacturer to the site.
- According to the Australian Standards there are specific design elements based on the diameter of the tank. The inclusion and size of the inspection opening is all based on the diameter. As the tank diameter increases, so too does the size of this inspection opening. For example, a tank diameter less than 914mm does not require a full manhole, but rather what AS1210 calls a head hole. This dramatically reduces the cost.
- Furthermore, it is the diameter to pressure ratio that determines the Hazard Rating of the tank. If the pD is less than 2300MPa and the temperature of the water is between 0-65°C (as is the case of Chilled water and many heating water circuits), then the tank will always be Hazard Level E. As detailed earlier in this article, Hazard Level E is the lowest Hazard Level.
Internal Structure – baffle or sparge pipe?
Internal structure refers to internal baffle plates or sparge pipes. The inclusion of either of these (or both) naturally will add to the overall cost of a buffer tank.
What factors drive the cost of a buffer tank down?
The elements that affect a cost reduction of a Buffer Tank are somewhat related to the aspects detailed above. Lets look into some of the key factors that might reduce the cost of a buffer tank.
Insulation of the Tank
If the pre-insulated tank is packaged correctly, it will not bear any damage during transit (unless the truck rolls over of course!) In considering the tank cost only, a bare tank will bring the cost down over against a pre-insulated tank. In some applications, the insulation isn’t required. But a tank that is insulated on site will always be more expensive than a tank that is insulated in a controlled factory environment.
Cladding over the insulation
Some tanks are available with a vinyl jacket rather than metallic cladding. These will typically be cheaper. Furthermore, standard cladding by the manufacturer will normally be cheaper than a special grade or colour of cladding.
Pressure or no pressure?
Just as an increase in pressure can drive the cost of a buffer tank up, the absent need of a pressure rating can drive the cost of a buffer tank down. In open, atmospheric applications for example, a pressure vessel may not be necessary but rather an open tank. There will be non-pressure applications where a plastic tank is sufficient too, in adding extra volume to the system.
Instrumentation
Aside from the buffer tank itself, generally a range of instruments are necessary for the tank. A pressure relief valve for example is mandatory on every buffer tank. However a vacuum breaker isn’t always necessary and so the exclusion of this will drive the cost down.
Customization
The more customized a tank needs to be for your application, the greater the cost impact. Therefore a standard tank will help to keep the cost of your buffer tank down and in many cases without any detrimental cost to the installation on site.
Why is it that some companies/brands are expensive?
Having looked at the main contributors that affect the production cost of a tank, lets now consider why some companies/brands differ in cost to others.
Pressure Testing Capabilities
A manufacturer that doesn’t pressure test every individual tank prior to delivery naturally has a lower cost basis than a company that does. The implications of a non-tested tank arriving to site that does happen to leak can be catastrophic for all parties.
ISO Certification
A supplier that has achieved ISO9001, ISO14001 and ISO45001 certification and continues to maintain this will naturally have a higher cost base than a company that doesnt. The cost implications
Company Insurance to protect you
Just as ISO certification and an adherence to meticulous quality assurance within a Company can impact the cost of a buffer tank, or indeed any product, so too does the level of insurance by the Company. Is the Company you are looking to deal with have Public and Products Liability insurance of $20 million?
Compliance to Australian Standards
AS1210 is a stringent standard that aims to protect all vested parties. A company that both designs and manufactures to AS1210 will have a higher cost than a company that does not have this capability. There are other pressure vessel standards across the globe that are cheaper, particularly European manufacturers where system pressures are typically lower than here in Australia and so the setup required is less.
Economies of Scale
As with any mass-produced product, it is about economies of scale. A company whose focus is not in manufacturing of Buffer Tanks will naturally be more expensive.
What Next?
Now having read this article, it wouldn’t be unusual to admit that the factors affecting the cost of a Buffer Tank, both up or down, are perhaps more than you may have previously considered. A tank is a relatively simple item, but simply buying the cheapest tank you can find can have catastrophic consequences. Importantly, a tank over-specified for your system can cost more than is necessary.
As a long-time designer and manufacturer of buffer tanks, Masterflow continues to lead the industry across Australia for such products. For an overview of the core range, CLICK HERE. Making it easy for engineers and contractors alike will always be at the heart of what drives Masterflow.
Reach out to us by phone on (02) 9748 2022 or share with us the information you have so far by filling out the fields on THIS FORM, and we’ll be very glad to support you.
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