Grundfos DMH and DMX are both series of dosing pumps used in various industrial applications, such as water treatment, chemical dosing, and process engineering. Here are the key differences between the two:

Grundfos DMH Series

1. Design and Construction:

   • The DMH series is designed for high precision and reliability, often used in demanding applications.
   • It features a mechanically actuated diaphragm, ensuring leak-free operation.
   • Constructed with materials suitable for handling aggressive chemicals.

2. Performance:

   • DMH pumps are known for their high-pressure capabilities, often handling pressures up to 200 bar (2900 psi).
   • They offer accurate dosing with a high repeatability rate.

3. Capacity:

   • DMH pumps can handle a wide range of flow rates, typically from 0.15 to 2000 liters per hour (L/h).

4. Applications:

   • Ideal for high-demand applications such as oil and gas, water treatment, and the chemical industry.

5. Control Options:

   • Available with various control options, including manual control, pulse control, and integrated digital controllers for automated dosing.

Grundfos DMX Series

1. Design and Construction:

   • The DMX series is designed for flexibility and ease of use, suitable for a broad range of applications.
   • It uses a diaphragm dosing pump with a mechanically actuated diaphragm.

2. Performance:

   • DMX pumps are designed for medium to low-pressure applications, usually handling pressures up to 10 bar (145 psi).

3. Capacity:

   • These pumps offer a broad capacity range, typically from 0.4 to 4000 liters per hour (L/h).

4. Applications:

   • Suitable for general dosing applications, including water treatment, chemical processing, and industrial applications.

5. Control Options:

   • Comes with basic control options such as manual adjustment and pulse control.
   • Can be integrated with external controllers for automated operations.

Summary of Key Differences

• Pressure Handling: DMH pumps are suitable for high-pressure applications (up to 200 bar), whereas DMX pumps are designed for medium to low-pressure applications (up to 10 bar).
• Precision and Reliability: DMH pumps are engineered for high precision and reliability in demanding environments, while DMX pumps are more versatile and user-friendly for general applications.
• Capacity Range: Both series cover a wide range of capacities, but DMH pumps are more focused on high-precision, high-pressure dosing, while DMX pumps offer more flexibility for different dosing needs.
• Applications: DMH is better for heavy-duty, demanding industrial applications, while DMX is suitable for a wider variety of less demanding applications.

Both pump series provide robust solutions for different dosing needs, with DMH focusing on precision and high-pressure applications, and DMX offering flexibility and ease of use for a variety of dosing tasks.

1. Product introduction
Features and benefits
Proven and versatile
The DMX pump range has proven its worth in dosing applications worldwide. With their robust diaphragm-based design and their high-quality motors, DMX pumps require minimum maintenance and are the best choice for many dosing
applications. The DMX range is highly versatile: it covers a wide flow range and offers a variety of dosing head sizes, materials and accessories.

Accurate dosing - all the time
The diaphragm design makes sure that the dosing flow fluctuation and the linearity deviation are very low. This allows very precise dosing of chemicals - as much as necessary, as little as possible.

Smooth and low-pulsation dosing
Sophisticated drive technology and gear kinematics ensure smooth and low-pulsation dosing. This means less stress to all system components, such as tubes and valves, and leads to longer service intervals for the entire system.

Compact design saves money and space
DMX pumps are available in different dosing head sizes. The compact design allows placing several pumps right next to each other in confined spaces. Double-head versions (DMX models 226 and 227) offer a very cost-efficient way to save space or to dose two different chemicals. The extra capacity offered by double-head versions can also be used to gain higher flow rates for a single chemical.

Perfect material selection for housing and liquid-wetted parts
The models DMX 221 have PPE housings offering chemical resistance and all the protection necessary for many applications. The models DMX 226 and DMX 227 have a robust cast-aluminium housing with epoxy coating to meet all
application needs. 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 NBR and PTFE-coated.

Motors to match application needs
For applications with specific motor requirements, the versatile mechanical dosing pump range offers the following options:
• Ex-classified or ATEX-certified high-quality motors
• Motors with integrated variable frequency drive (VFD) are available on request.
Mechanical dosing pumps equipped with a motor with factory-mounted integrated VFD provide extended capacity range and functionality. They include analog inputs and outputs, an integrated potentiometer for precise and easy
setting of speed, control and self-monitoring functions as well as an interface for field bus communication (Profibus, Profinet).

This option is only available for pumps that are able to run at 100 Hz. See performance data tables.
• Motors with PTC, prepared for operation with external variable frequency drive (VFD).
Mechanical dosing pumps equipped with a motor with PTC, planned to be operated by a VFD, the VFD is not supplied with the pump. The PTC protects the motor against locked-rotor conditions, continuous overload and high
ambient temperature.
- Use a VFD that can operate at constant torque. The VFD should have a 150 % overload capacity for 60 seconds.
- Respect the limitations on minimum and maximum operating frequency to prevent gear breakdown or motor
overheating. See performance data tables.

This option is not available for pumps selected for ATEX.

Accessories ensure perfect operation of the entire system
A wide range of accessories specially designed for the DMX range helps to optimise performance: AR control electronics (contact signal control with multiplier and divisor function, 4-20 mA control or stroke frequency control via display and keypad, low-level/empty signal), integrated relief valve, dosing controller, diaphragm leakage detection and servomotor for automatic stroke-length adjustment.
In addition, we offer system components such as pressure-loading valves and pulsation dampers.

ATEX approval
EX classified and ATEX approved motors and pumps for potentially explosive areas are available on request. 

Ex zones for DMX 226
ATEX approved DMX 226 pumps can be used in the following EX zones:
• ATEX Directive, Group II, category 2 (zone 1/21)
• ATEX Directive, Group II, category 3 (zone 2/22)
Note: DMX pumps are not suitable for dosing combustible media.

Applications
DMX pumps are intended for the dosing of chemicals in tasks like disinfection, coagulation, flocculation, precipitation in various application fields:
• Drinking water treatment
• Wastewater treatment
• Pulp and paper industry
• Textile industry
• Cleaning water treatment
• Food and beverage industry, dairies
• Cooling tower water treatment
• Low-pressure boiler feed water treatment
• Agriculture
• Irrigation
• Fertigation

Electric servomotor
To facilitate automatic control of the flow rate, mechanical dosing pumps can be equipped with an electric servomotor in IP65 housing. The electric servomotor primarily consists of a digitally controlled stepper motor, reduction
gear and min/max limit switches. The electric servomotor is connected to the control slide of the dosing pump. This adjusts the active stroke length and the corresponding dosing flow. The electric servomotor is available as ATEX version, EX II2G

Ex db IIB T4 for potentially explosive zones.

Variants
• Electric servomotors with different operating voltages
• Electric servomotors with 4-20 mA control and output signal and manual/automatic switch

AR control unit
The AR control unit contains convenient electronics in an IP65 housing, and is suitable for the following pump models:
• DMX 221 with special single-phase motor
• DMX 226 with special single-phase motor

Control modes
• Manual control: stroke frequency is manually adjustable from 1 up to the maximum strokes per minute.
• Pulse signal control: multiplier 1:n (n strokes per incoming pulse) and divisor n:1 (1 stroke per incoming n pulse), memory function (stores a maximum of 65,000 pulses).
• 0/4-20 mA analog signal control: adjustment of stroke frequency in proportion to the current signal and weighting of current input is possible.
• The AR control unit is mounted on the terminal box of the motor.

Inputs
• Pulse signal
• Analog signal
• Remote on/off
• Tank-empty sensor
• Dosing controller and diaphragm leakage sensor

Outputs
• Analog signal
• Error signal (fault)
• Stroke signal
• Low-level signal

Integrated pressure-relief valve (PRV)
The DMX models 221 and 226 (up to 460 l/h) are available with an optional pressure-relief valve (PRV) integrated in the dosing head. If the pressure rises above the set opening pressure, the PRV opens and the dosing medium is returned to the dosing tank.

Diaphragm leakage detection
Pumps prepared for diaphragm leakage detection have a special dosing head flange for inserting the opto-electronic sensor. The opto-electronic sensor contains an infrared sender and an infrared receiver.
In case of a leaking diaphragm, liquid penetrates the dosing head flange and the light refraction in the opto-electronic sensor changes. The sensor produces a signal. This signal can be used to trigger an alarm device or to switch off the
pump via:
• Electronic unit for optical sensor (230 V, product number 96725701)
• AR control unit (DMX 221 and DMX 226).

Variable frequency drive (VFD)
Mechanical dosing pumps with integrated variable frequency drive provide extended capacity range and functionality.
They include analog and digital inputs and outputs and an integrated potentiometer for precise and easy setting of speed and flow as well as control and self-monitoring functions. Mechanical dosing pumps can be prepared for variablefrequency-drive operation and include a variable frequency drive (VFD).