Walchem EHE Series Electronic Metering Pump

The workhorse solenoid metering pump of the E-Series

The EHE is described by Walchem as the workhorse of the E-Series metering pumps. It combines output up to 20 GPH (75 L/h) and pressure capability to 150 PSI (10 bar) with a turndown ratio of 1800:1, which allows one pump to cover a wide range of chemical feed rates in water treatment. Operation at 360 strokes per minute gives high-resolution chemical feed and long service life, and Walchem states that EHE pumps prime in seconds and hold prime reliably.

Mechanical design features include dual bearing support for the armature and shaft, dual check-valve assemblies in the suction and discharge fittings with precision ball guides and tapered seats, and a high compression ratio that supports proper feed with off-gassing chemicals such as sodium hypochlorite.

Technical specifications

Capacity, control and model code

Walchem uses a power index, the maximum pressure multiplied by the maximum output at that pressure, to compare pumps. The EHE36 delivers 8.5 GPH at 105 PSI for a power index of 892.5, a figure Walchem cites as a measure of hydraulic output. Microprocessor control is standard on every EHE: manual speed adjustment from 1 to 360 spm through a four-button keypad, external pulse control with internal multiply and divide, or analog control from a 4-20 mA signal. Pulse control is often used with a contacting flowmeter in flow-proportional systems.

The model identification is built from the series, capacity size, control module, voltage and liquid-end codes, for example EHE36E1-PCV as printed in the brochure. Liquid-end options are described in the brochure and manual, so the choice of PVC or PP and the valve and seal materials should be matched to the chemical being fed.

Selection and installation points

Start from the required flow at the real discharge pressure, then choose the smallest size that covers the peak with headroom, because output rises as discharge pressure falls. Check chemical compatibility for the wetted parts, the liquid temperature limits above, supply voltage, and whether a signal from a flowmeter or a 4-20 mA controller will drive the pump. Keep the pump out of direct weather, and note that the manual provides mounting dimensions (for example 132 x 114 mm hole pattern on the EHE56 drawing).

The EHE sits beside Walchem’s EWN-Y and the digitally controlled IX pumps; buyers who need higher pressures at lower flows can compare the EWN-Y at up to 290 PSI, while those who need very wide turndown or higher capacity can review the IX series.

How the Walchem EHE works

The EHE is a solenoid-driven diaphragm metering pump. Each pulse of the solenoid moves the diaphragm and pushes a measured volume of chemical through the discharge check valves. Changing the stroke rate changes the feed rate, so the controller can match the dose to the water flow.

Where the EHE is used

• Water treatment chemical feed
• Sodium hypochlorite dosing
• Cooling tower treatment
• Boiler water treatment
• Pulse-proportional dosing from a water meter

Selection checklist for the EHE

• Required output in GPH or L/h
• System back pressure
• Liquid end material
• Liquid temperature
• Chemical viscosity
• Control input type
• Supply voltage
• Tubing and fitting size

Installation, commissioning and maintenance notes for the EHE

Mount the pump below the chemical tank level where possible and shield it from direct exposure to the weather. Fit a back pressure or anti-siphon valve where the system needs one. Prime the pump, set the stroke rate and check the output with a calibration column. Inspect the check valves and the diaphragm at regular intervals.

Requesting a quotation for the Walchem EHE

Please send the model, the required flow, the discharge pressure and the chemical to be dosed. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

EHE pump family

The EHE belongs to the Walchem E-Series of metering pumps.

EHE maximum output

The family reaches an output of up to 20 GPH, which is 75 L/h.

EHE maximum pressure

The pressure capability reaches 150 PSI, which is 10 bar.

EHE turndown ratio

The turndown ratio is 1800 to 1.

EHE stroke rate

Speed runs from 1 to 360 strokes per minute in steps of 1.

EHE priming

Walchem states that the pump primes in seconds and holds prime reliably.

EHE armature support

The armature and shaft have dual bearing support.

EHE check valves

Dual check valve assemblies sit in the suction and discharge fittings.

EHE valve seats

The check valves have precision ball guides and tapered seats.

EHE off-gassing chemicals

A high compression ratio supports proper feed with off-gassing chemicals such as sodium hypochlorite.

EHE31 output

The EHE31 gives 5.5 GPH, or 340 mL per minute, at up to 150 PSI.

EHE36 output

The EHE36 gives 8.5 GPH, or 520 mL per minute, at up to 105 PSI.

EHE46 output

The EHE46 gives 12.0 GPH, or 750 mL per minute, at up to 60 PSI.

EHE56 output

The EHE56 gives 20.0 GPH, or 1250 mL per minute, at up to 30 PSI.

EHE stroke volume

The volume per stroke runs from 0.94 mL on the EHE31 to 3.47 mL on the EHE56.

EHE high viscosity models

The EHE36-HV and the EHE46-HV are built for high viscosity liquids.

EHE36-HV output

The EHE36-HV gives 5.2 GPH at 73 PSI.

EHE46-HV output

The EHE46-HV gives 8.0 GPH at 60 PSI.

EHE pulse input

The pulse input has multiply and divide settings from 1 to 999.

EHE analog input

A programmable 4 to 20 mA input has a user-defined minimum and maximum speed.

EHE electrical supply

It runs on 115 VAC or 230 VAC, 50 or 60 Hz, single phase.

EHE power draw

The average power is 48 W.

EHE liquid temperature

PVC liquid ends take 0 to 40 degrees C and PP or PVDF liquid ends take 0 to 60 degrees C.

EHE ambient conditions

The ambient range is 0 to 50 degrees C at 30 to 90 percent humidity, non-condensing.

EHE shipping weight

The shipping weight is about 10.5 kg.

Pump records for the EHE

Record the model, the stroke setting and the date of each check valve inspection.

Choosing the right EHE model

Choose the model from the output you need and the pressure of the injection point.

Documents and quotation

The EHE brochure is attached. Other dosing pumps are listed under Pumps; a comparable item is the ProMinent Sigma X S1Cb motor-driven metering pump. Send the model code (for example EHE36E1-PCV), quantity and chemical to be dosed through the RFQ form.