Bertfelt is the leading manufacturer of constant flow valves for industrial use, sold under the brand BT-Maric. The BT-Maric constant flow valves (sometimes called flow restrictors, flow limiters) are designed to deliver a pre-determined, constant flow rate for water and similar media regardless of the pressure variations.

Bertfelt offers a complete range of precise constant flow valves for industrial use that saves water and makes products and processes more efficient. Their constant flow valves are used in many different industries/applications such as mining, process industry, irrigation and farming, water treatment, pump & filter protection etc. the company is the first choice partner for OEM manufacturers.

Easy Engineering: What are the main areas of activity of the company?

BERTFELT: BT-Maric constant flow valves are used in many industrial applications. The most commons applications are:


  • Dosing equipment – controlled mixing of ingredients.
  • Mechanical seals – indicating minimized but correct flow.
  • Vacuum Pumps – for controlling flow of crucial sealing/service liquid to liquid ring vacuum pumps.
  • Fire Fighting; proportioners – correct ratio dosing of foaming agent in high flow applications.
  • Dust Suppression – sprinkler control on mobile water tankers.
  • Cooling equipment – correct flow of cooling water to machinery. Often with solenoid valves.
  • Safety Showers & Eyewash equipment – controlled flow ensures consistent and safe operation.

Water treatment & filtration equipment:

  • Back-wash flow rate control – for preventing media loss.
  • Optimized flow rate control through delicate filters.
  • Control trickle flow to water quality analysing equipment.
  • UV-sterilisation – controlled speed = controlled bacteria kill.

Water authorities

  • Flow limiting – extending water meter life, enabling economical distribution to rural connections.
  • Flow control instead of water meters and to force water restrictions.

Irrigation and farming

  • Sprinkler flow control – over-spraying mists wastes water.
  • Fitted to each outlet ensures uniform output at different elevations.
  • Animal farms – correct and limi­ted flow to all animal stalls.

Project market– hotels, restaurants, condominiums, event areas

  • Drinking Fountains – controlled stream prevents frustration at the drinking fountain.
  • Washing & dish washing machines In condominiums – making sure that all users get a correct but limited flow.
  • Wash basins – controlled and limited flow rates.
  • Water Heaters – keeping flow below a preset maximum ensures gas & electric instantaneous heaters can heat to a sufficiently hot & advertised temperature.


  • Gland water flow control to gland-packing/stuffing box and mechanical seals of centrifugal and slurry pumps.

Pump protection

  • For keeping a pump on its curve and preventing cavitation damage.
  • For use on high draw-down bores for preventing up-thrust damage and for preventing over-pumping beyond bores capacity & drawing in of air or sand – leading to unstable conditions.
  • Protection from overloading of electric motors, control of cooling water to liquid ring vacuum pumps.
  • Gland-water & mechanical seal – seal water flow control.

E.E: What’s the news about new products?

BERTFELT: In many applications today, it is necessary to have the smallest possible throughput. For a long time, the smallest flow rate was 0.4 L / min. To help customers optimize their flow and save water, Bertfelt Teknik has now added 5 new flow rates below 0.4 L / min: 0.15 L / min, 0.2 L / min, 0, 25 L / min, 0.3 L / min as well as 0.35 L / min. All with the standard accuracy of nominal flow +/- 10% over the entire pressure delta range 1.4-10 bars.

E.E: What are the ranges of products?

BERTFELT: Bertfelt flow limiters deliver a constant, pre-set water flow regardless of pressure variations. The flow rate is kept constant by increasing or decreasing the orifice of the diaphragm inserted in the body of the limiter during pressure variations. Bertfelt Teknik has a complete line of water flow regulators regulating flow rates from 0.15 L / min to 13,500 L / min (DN6-DN400). The constant flow valves are available with 3 types of connections: 

  • Inserts that are fitted into existing piping or cavities in the equipment, 
  • As screwed valvest
  • As wafers (for large flow rates), that are installed between 
  • BT-Maric limiters are simple, compact, reliable, 100% mechanical, for low pressure (from 0.4 bar) and high pressure (up to 20 bar).

E.E: What can you tell us about market trends?

BERTFELT: Today, we can see an increase in interest in controlling water flow and saving water. Many industries and applications are using more and more constant flow valves to regulate flow rates.