Compressed air receiver tanks - sizing, installation, fittings
A receiver tank is the cheapest component in a compressor room, yet one of the most often chosen by guesswork. A properly sized air receiver stabilises pressure in the network, absorbs demand peaks, reduces the number of compressor cycles and drops out the first batch of condensate before the air reaches the dryer. We size, supply and install air receiver tanks together with fittings, including as an addition to an installation already in operation.
Why an installation needs a receiver tank
A compressor generates air at the rate its motor and controls allow, while the plant draws it unevenly, in the rhythm of machines and shifts. The receiver is the buffer that separates these two worlds. Without it, every change in demand instantly affects compressor operation and pressure at the point of use.
Buffer for demand peaks
The tank stores air and releases it the moment the plant needs more than the compressor can generate at that instant. Thanks to this, short peaks - for example several machines starting at once or a series of blow-offs - do not end in a pressure drop across the whole hall.
Pressure stabilisation
The larger the volume of air in the system, the more gently pressure changes when demand shifts. Stable pressure means repeatable operation of actuators and tools and a lower risk of quality defects caused by varying clamping force or an incompletely closed valve.
Fewer start-stop cycles
A compressor without a buffer switches on and off very often, and every start means a current surge and load on the motor, contactor and inlet valve. The tank extends the time between cycles, which directly translates into fewer failures and a longer service life for the machine.
Early condensate separation
Air enters the tank hot and saturated with moisture, and in a large volume it slows down and cools, so part of the water condenses out right there. The dryer and filters downstream of the tank receive less moisture, run more smoothly and need servicing less often.
How to size the tank capacity
Sizing the capacity is a compromise between space in the compressor room, price and comfortable operation of the installation. An undersized tank shows up immediately: the compressor switches on and off very often and pressure jumps with every larger draw-off. An oversized tank causes no technical harm, it just takes up space and raises the investment cost.
A practical sizing rule
The starting point is roughly 6 to 10 litres of tank capacity for every litre per second of compressor output. For a machine delivering around 50 l/s, that gives a range of 300 to 500 litres. It is an approximate rule, but in practice it shows the order of magnitude well and immediately reveals cases where a decidedly too small tank has been hung on a large compressor.
When to aim for the higher end
Closer to 10 litres per l/s and above is worth targeting in plants with large swings in demand: blow-offs, cleaning air guns, cyclical work in the rhythm of a press or a packaging machine. The same applies to a compressor with load/unload control, the classic loaded and idle mode, where a larger buffer directly reduces the number of switches per hour.
When less is enough
A variable-speed compressor keeps up with demand changes on its own, so the tank can be smaller and mainly serves to smooth pressure and separate condensate. A smaller buffer is also justified with constant, even demand throughout the shift, when the machine practically never comes off load.
Typical catalogue capacities
In practice we size from the range of 270, 500, 900, 1000 and 2000 litres. In larger installations it more often pays to split the volume between a main tank in the compressor room and an additional tank near a receiver with high instantaneous demand, rather than fitting a single very large tank at the start of the network.
What the rule cannot replace
In the end, what counts is the demand profile, not the motor nameplate. If it is not known how the plant actually consumes air, it is worth starting with a measurement of the compressor's loaded running time and the pressure trace in the network. Such a measurement also shows whether pressure drops will be solved by a tank or rather by a pipeline that is too narrow.
Vertical or horizontal, galvanised or painted
Beyond capacity, three things need to be decided: orientation, internal protection and the allowable pressure. Each of them affects the tank's durability and ease of operation more than is usually assumed at the time of purchase.
Vertical or horizontal
A vertical tank takes up noticeably less floor space and is the natural choice in a cramped compressor room, and condensate drainage from the bottom works very well in it. A horizontal tank is lower, easier to transport and to service the fittings on, and it often fits where height is lacking or where it is meant to serve as a base for the compressor unit. From the point of view of installation operation both variants are equivalent - the deciding factors are the location, service access and how the pipework connects.
Galvanised or painted
A tank painted on the inside is cheaper and is sufficient where condensate is drained systematically and the tank operates in a heated room. Internal galvanising withstands constant contact with water much better, so we choose it for installations without a dryer, for seasonal work with long standstills, in humid rooms, and everywhere the tank is to stand outdoors or in an unheated hall. The price difference pays for itself through the absence of bottom corrosion, which in practice is the most common reason a tank is taken out of service.
Working pressure 11 and 16 bar
For plant installations at 6 to 8 bar, tanks rated for 11 bar are the standard and in most cases the right choice. 16 bar versions are used in installations working at higher pressure, for example in moulding, selected process applications, or wherever the tank is to buffer air upstream of a regulator that lowers the pressure to the network. The tank must always have an allowable pressure higher than the maximum pressure the compressor can generate.
Tank fittings
A tank without a complete and functioning set of fittings is not ready for operation. This is also the part that is easiest to neglect in service, because it works unattended right up until the moment it stops working.
Safety valve
Matched to the tank's allowable pressure and to the compressor's output. This is a component that must never be blanked off or replaced with a valve set to a different value, and we check its operation at every compressor room inspection.
Pressure gauge
A clear pressure indicator for the tank, ideally with the working range marked. It lets you immediately assess whether a pressure drop at a point of use comes from the compressor's operation or arises further along the installation.
Automatic condensate drain
We strongly recommend an electronic or float-type drain instead of a manual valve that usually nobody remembers to open. An automatic drain removes water without air losses and protects the tank's bottom from corrosion and the installation from water in the pipework.
Connections and tie-in
We select the tank together with its connections: inlet from the compressor, outlet to the dryer and network, ports for the pressure gauge, safety valve and drain, and a port for a control pressure sensor if needed. We set the spacing and diameters of the connections to match the existing pipework, to avoid restrictions and unnecessary bends.
Formalities around a pressure vessel
Compressed air receiver tanks are pressure equipment and are subject to pressure equipment regulations. This means that before being put into service the tank is registered for acceptance and later undergoes periodic inspections at intervals resulting from the regulations and from the operating parameters. These obligations rest with the user as the operator of the equipment and we do not take them over.
Our role is to supply the tank together with the full set of manufacturer documentation needed for registration, along with data on how it is to be connected into the installation, its positioning and fittings. We also advise on what to ask about before acceptance and how to prepare the installation site so the tank stays accessible for servicing and inspection.
In practice most delays come from small things: missing documentation for a second-hand tank, a safety valve set to a value that does not match the tank, or a location that cannot reasonably be accessed. That is why we settle these matters at the sizing stage, not after delivery.
Our offer
We start by sizing the tank for the specific installation: we check the compressor's output and type of control, the demand pattern in the plant, the available space and the condition of the pipework. Only on that basis do we propose the capacity, orientation, allowable pressure and scope of fittings.
We supply the tank together with a new Hertz Kompressoren compressor when the customer is buying a whole compressor room, or separately as an addition to an installation already in operation. We carry out installation, connection to the pipework, hookup of the condensate drain and a tightness check of the joints, and while on site we also inspect the whole compressor room: pressure, filtration, the dryer and points where air is escaping.
See also compressor sales, compressed air installation modernisation, compressed air installation design and installation and our guide to rotary screw compressors.
Compressed air receiver tanks - FAQ
The most common questions about sizing, positioning and formalities.
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