DMH hydraulic piston diaphragm dosing pump

General Details


The Grundfos DMH range is a series of extremely strong, robust pumps for applications requiring a reliable dosing and high-pressure capability, such as process engineering. The DMH 28x has been especially designed for high-pressure applications from 50 up to 200 bar. The range is highly versatile: it covers a wide flow range and offers a variety of dosing head sizes, materials and accessories. Customers worldwide have enjoyed years of trouble-free operation from their DMH pumps.

Accurate dosing – all the time

DMH pumps have a very high dosing accuracy and allow an exact reproducibility. For DMH25x, the dosing flow fluctuation is <± 1.5 % within the 10-100 % control range, and the linearity deviation is ± 2 % of the full-scale value. For DMH28x, the dosing flow fluctuation is <± 1.0 % within the 10-100 % control range, and the linearity deviation is ± 1 % of the full-scale value.

Smooth and low-pulsation dosing

The DMH range combines sophisticated drive technolo­gy and gear kinematics to ensure smooth and low-pulsation dosing without pressure peaks. This means less stress to all system components, such as tubes and valves, and leads to longer service intervals for the entire system.

Motors to match application needs

For applications with specific motor requirements, the versatile DMH range offers high-quality motors for 50 Hz, 60 Hz, 100 Hz (with Variable Frequency Drive VFD), as well as EX classified or ATEX-certified motors, if required.

Perfect material selection – for housing and liquid-wetted parts

The DMH models have a robust cast-aluminium housing with epoxy coating to meet all application needs (grey cast-iron if API 675 is required). Investment costs and running costs for spare parts are kept low over the years: A wide choice of materials for dosing head, valves and accessories allow selecting exactly the degree of chemical resistance required. All liquid-wetted parts need to be resistant to the chemicals used. The diaphragm is made of full-PTFE material.

Safe and trouble-free operation

The serially integrated pressure relief valve and active diaphragm protection system (AMS) keep the pump and entire system protected against overpressure, if the discharge line is blocked. In addition, the degassing valve at the pump guarantees high functional safety of the pump, the installation and the whole process. Due to aluminium enclosure and the piston diaphragm technology, DMH pumps have a very long operating life and long service intervals.

Approvals and certificates

For potentially explosive areas we offer EX classified or ATEX-certified motors and pumps. For applications in the petro chemistry we provide special versions of our DMH dosing pumps with API 675 certificates.

Flexibility – in pump configuration and applications

A number of different product configurations are available to match requirements: Flexible control concept for flow rate: manual or automatic stroke-length adjustment with electric servomotor. Pumps fitted with double diaphragm with failure indication, or special dosing heads with electrical heating. Universal fields of application are possible for this pump series due to the full-PTFE dosing diaphragm. Wetted parts are available in material combinations that suit virtually all dosing tasks. Choose the best configuration for your specific dosing task.

Ready for tough application areas

Power plants

Dosing of various chemicals in all stages in a power plant:

  • For boiler feed water, treatment of cooling water and process water (raw water purification, chemicals for ion-exchangers, supplementary water treatment, effluent water neutralization).
  • Dosing of ammonia, hydrazine, phosphates in high-pressure areas (boiler feed water).

Petrochemical/oil & gas industry, refinery

Dosing of chemicals in process areas around the production of oil and gas (apart from drilling hole, platform):

  • Dosing of chemicals for treatment of cleaning water and process water
  • Dosing of wax as lubricant in oil-pipelines
  • Dosing of inhibitors and anticorrosion chemicals to protect oil pipelines
  • Dosing of additives and catalysts
  • Odorisation of gas because of safety aspects in case of leakages

Treatment of process water and drinking water

  • Rough environments (hot climate, desert, outdoor installations)
  • Higher flow and pressure ratings

EX zones

  • ATEX Directive (94/9/EC), Group II, category 2 (zone 1/21) and
  • ATEX Directive (94/9/EC), Group II, category 3 (zone 2/22)

Dosing of flammable liquids

  • Dosing of alcohol or methanol in wastewater treatment
  • Cleaning of kerosene and petrol in mechanical engineering and airport areas
  • Dosing of ethanol and methanol
  • Dosing of food-grade alcohol for disinfection in meat and bread packaging


Technical service