DN80 with a pneumatic pressure and mechanical relief valve.

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Product Description
Technical data

Gear pumps

High reliability and robust design combined with active product development have given the Wennstrom gear pump a genuinely good reputation and a long history. The pump has been developed to meet the most varying installations and demands.


The latest addition is the double acting relief valve that permits the pump to be reversed thus allowing pipe and hose pipe systems to be emptied with ease. This reduces the risk for product contamination when the same installation is used for pumping different products or grades.

Many applications

The pump is mostly used within the petroleum distribution industry but has also, thanks to its versatility, found many other industrial applications. It is manufactured in three different sizes with capacities from 400 up to 2000 litres per minute.

It can be configured in eight different ways which simplifies installation and pipe layout. The pump can be powered directly linked to an electrical or hydraulic motor or a truck PTO. For truck and PTO installations the pump can be extended with a hydraulic pump to supply other power consuming equipment.

Mechanically powered pumps

The basic model is directly connected to a PTO, electric motor or any kind of transmisson.

Hydraulically powered pumps

Running the pump with a hydraulic motor simplifies the installation and piping and facilitates fitting the pump in the most suitable place. It also makes it easier to control speed and direction. The two smaller pumps, 2 1/2” and 3”, can be delivered with a specially designed bracket for VOAC´s F12 series and Sunfab´s M-series of hydraulic motors. The pump can be ordered with or without the hydraulic motor.

Pumps with hydraulic pump

Wennstromís pump with an extended drive shaft and fitted with a hydraulic pump offers an economical alternative to the hydraulically powered pump. With the pump connected to the PTO it still offers the possibility of hydraulic power to other equipment. Our standard delivery is a Bosch pump giving 16 cm3/revolution and 210 bar maximum working pressure.

Relief valves and pressure control

To achieve the most optimized and safest working conditions the pump pressure can be set between 1.5 and the maximum permissible 10 bar. The two available relief valves are described below. Spring loaded. Suitable for fixed installations with stable working conditions pumping a liquid with uniform viscosity. The pressure is set by adjusting the tension of the relief spring. Normally the pressure can be set between 4 and 10 bar. If a lower pressure span is required please indicate this when ordering.


A pneumatic relief valve with a spring loaded plunger. The pressure in the primary pumping direction is controlled by a pneumatic regulator. In the reverse direction the pump pressure is set by a spring. The relief valve can be opened by shutting off the pneumatic pressure. This will enable fast degassing of a pipe system under gravity pressure.

The reversible 3” pump has the following relation between the pneumatic pressure and the opening pump pressure of the relief valve. To prevent the pump pressure from exceeding 10 bar (the maximum permissible pressure for a pipe system on a road tanker), the relief valve is designed to give 9.5 bar to a closed pipe system at a pneumatic pressure of 7 bar. Depending on the flow rate and the viscosity of the liquid the total pump pressure will exceed the opening pressure of the relief valve. For diesel oil the pump pressure is about 1 bar above the opening pressure. In reverse the pump will give a maximum pressure of approximately 5 bar.


Road tanker installations

The reversible pump is the best alternative in combination with Wennstrom’s other systems for road tankers. Together with the electronic gas separator FlowCheck the pump provides a fast and efficient degassing with gentle degassing stops and starts. This is particularly noticeable when discharging from a drawbar trailer through a pump fitted on the truck. Together with the electronic measurement system VolumeCheck the reversible pump can empty the delivery hose and make the handling of a long and heavy hose much easier.

Shaft seal

A well proven design with both teflon and graphite parts combined with teflon impregnated cotton braid. The seal is lubricated by the pumped liquid and can easily be tightened up which gives a very long life span. When required the seal is easily dismantled and new parts fitted.

Capacity and Power Requirements

The graphs below are related to pumping a liquid similar to diesel oil with a density of 773 kg/m3 at 15° C without any pressure on the feed side and with a secured relief valve. The upper part of the each graph shows the power requirement when pumping steadily without any relief flow. When deciding about the motor size considerations must also include the temperature and viscosity of the pumped liquid as well as the pressure drop of the connected pipe system. Remember that very long hoses and pipe systems have a considerable start up resistance. The lower part of the graphs shows the pumped volume in relation to the speed in rpm. The shaded areas indicate the approximate pressure limits for a pump equipped with a spring loaded relief valve. The size of this area is very much influenced by the viscosity of the liquid. A pneumatically controlled relief valve gives the pump a much wider pressure span.

Assembly configurations, flowand rotation directions

The three flange connections of the pump can be used as either in- or outlet and there are two possible shaft positions giving in total eight different assembly possibilities. Configurations one to four have a low fitted main shaft and five to eight come with the top placed shaft. When ordering please state both item number and the desired configuration.

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