Expansion tanks

Our expansion tanks are designed and manufactured under both the Ad Merkblätter design code and ASME Section VIII, Division I U Stamp.

The normal version of these tanks connects to the heat oil collection tank without pressurization. The volume of these expansion tanks depends on three factors: the type of heat transfer fluid, the temperature of the circuit and the total volume of the system. Consult our engineering department for proper sizing of the tank volume.

Our tanks are provided with a level switch connected to the heater control cabinet which emits a general stop alarm when the level is insufficient. It also has a lateral magnetic sheet visual level easily visible from anywhere.

These tanks also have all the associated instrumentation, valves and tubing and are therefore ready for assembly.

In the absence of nitrogen pressurization, generally we recommend they are installed about 2 meters above the highest point of the facility.

Pirobloc’s expansion tanks also have a safety valve for the discharge leading to the collection tank, a vacuum breaker valve and another drain valve.

The volume of the expansion tank is based on the total volume of the heating
oil circuit, working temperatures and the type of fluid used.


Key features

  • Horizontal design
  • Design pressure: 10 bar
  • Temperature: 260 ° C
  • The construction material of the expansion tanks is ASTM A 516 Gr. 60
  • Total corrosion thickness 3 mm.
  • They have a 150 lb 24” manhole, and nitrogen intake for circuit pressurisation and inertisation.
  • They include all control valves and pressure transmitters for split-range regulation.


  • Pressurization with nitrogen
  • Thermal insulation
  • ATEX version
  • Internal warming
  • Our expansion tanks can be designed and made for locations classified as having an ATEX explosion hazard.
  • They can also include a heating element to prevent the fluid freezing when ambient temperatures are extremely low. In these cases, thermal insulation for the tank and its associated tubing is also included.
  • Our expansion tanks can be supplied mounted on skids with all control instrumentation and safety elements.


Expansion tank level control is carried out by a magnetic reed level transmitter also including a minimum level alarm. This instrument allows the tank’s level to be read easily, regardless of its accessibility. It basically consists of a chamber parallel to the tank, connected to it at two points, in which a float with a magnet moves which shows the position of the fluid level on an external strip with magnetic reeds.

This magnetic reed transmitter reduces to a minimum the risk of leaks due to accidents involving breakages which may occur in other systems which use, e.g., glass or methacrylate in their reading chambers containing the hot oil.

It is vertically mounted on the side of the expansion tank with flanges.
Electrical switch or continuous reading signals are added to complement it.

Profibus or Hart communication can also be provided for integration in distributed control systems (DCS), as well as safety integration levels (SIL) and ATEX area classification.

  • Acceptable temperature range: -200ºC to +400ºC.
  • Optimum viewing without power input.
  • Indication proportional to the depth of the tank’s contents.
  • Simple, robust, solid design, with multiple possible configurations.
  • Pressure separation between the chamber and local indicator.

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