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Product code: PZ

North Ridge PZ Series Triple Screw pump

Pump Type - Screw

Max Flow Rate M³H - 324 M³H

Max Head - 160M

Pump Materials - Cast Iron

Max Temp - 150°C

Max Viscosity - 5000 cst

Max Solid Passage - 0mm

Self Priming - Y

Inlet/Outlet Sizes - 32mm to 250mm

Drive - AC Electric, Bareshaft

Max Suction Lift - 7.5M

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DESCRIPTION

PZ Series Triple Screw pump

Flow Rate	Up to 324m³/hr
Head (Pressure)	Up to 16 bar
Inlet/Outlet Sizes	DN32 to DN250
Operating Temperature	Up to 150°C
Viscosity	1.2 to 5000cp
Drive Options	Electric Motor, Magnetic Drive

The PZ series of triple screw pump can be utilised for a wide range of applications involving fuel oils and lubricating oils not containing solids, ranging in viscosity from 1.2 to 5000cp. The largest pumps in this series are able to achieve high flow rates up to 324m³/hr and medium pressures up to 16 bar.

This is the most modern design of triple screw pump within our range and has many benefits accumulating from years of product research.

As standard this positive displacement pump is supplied with in line suction and discharge ports for installation in areas where there are space limitations or where similar size pumps require replacement. The flanges are available in ANSI or DIN configurations. It can be mounted horizontally or vertically depending on customer requirements.

Our screw pumps have numerous benefits over other positive displacement pumps such as gear pumps. They produce low noise levels, are compact as no gearbox is required, produce low pulsations, are excellent at self-priming and can handle fluids containing trapped air.

This self-priming screw pump range is fitted with a maintenance free ball bearing and can be fitted with a built-in relief valve for protecting the system from overpressure.

This range is supplied with mechanical seal as standard but can be fitted with mechanical seal flushing or a magnetic coupling if required. The magnetic drive enables a completely maintenance and leak free solution for applications where this is a concern.

The PZ series can be fitted with an Atex motor for installation in non-safe areas. It is marine type approved by ABS, BV and RINA and can be marine witness tested by various classification bodies if required.

The PZ series of triple screw pump is available in various grades of cast iron, due to this fact it can be used for a wide range of applications within the marine and industrial markets. Some of the fuels and oils this range can handle include diesel (DO), Marine diesel oil (MDO), Low sulphur marine gas oil (LSMGO), Heavy fuel oil (HFO), lube oil, bitumen, asphalt and many more. Common applications include fuel cargo, fuel transfer, lube oil transfer, lubricating oil circulation, burner/boiler feed, fuel booster, fuel oil separator and many more involving compatible fuels and oils.

Product summary

• Suitable for a wide range of fuels and oils

• Excellent self-priming capability

• Quiet low pulsation operation

• Available in various grades of cast iron

• Nitrided steel screws

• Compact design

• In line suction and delivery ports

• Low NPSH required

• DIN and ANSI flanges available

• Can be supplied with counter flanges

• Can handle viscosities from 1.2 to 5000cp

• Motor speeds between 750 and 3600RPM without the requirement of a gear box

• Available with magnetic coupling for maintenance free and leak free operation

• Available with mechanical seal flushing

• Can be mounted horizontally or vertically

• Each pump is individually tested

• Marine type approved by ABS, DNV and RINA

• Marine witness testing available by various classification bodies

• Can be fitted with pressure relief valve

• Maintenance free ball bearing

• Single phase and three phase 50hz / 60hz motors

• Mill material certificates available, according to UNI EN 10204.

• Can be supplied with Atex motor

Read more about Screw Pump design in our guide

FAQS

Can this pump run dry?

No, definitely not! Screw pumps will incur damage even after short periods of dry running. Firstly, the screws require lubrication from the pumped fluid, for example fuel and oil. Dry running without these will cause fast and irreversible damage. The mechanical seal requires lubrication and cooling while the pump is operating. Without the presence of fluid, the mechanical seal will overheat and crack, and this may cause the pump to leak and fluid to enter the motor. There is also the possibility that the motor will burn out. Our advice is to ensure that the pump always has access to fluid while running, the vessel or sump on the inlet side of the pump must never run out of fluid while the pump is active. Level sensors or a float switch can be installed in the fluid chamber ensuring that the pump is turned off in the event there is no fluid. Another way of protecting the pump is to fit a dry running device, this will turn the pump off if it detects that no fluid is entering the pump. If you think that dry running is inevitable, then please speak to us and we will try to select a more suitable pump for your application.

What does the term self-priming mean?

A pump must be primed in order to operate correctly, this means that the pump casing and inlet pipe must be filled with fluid and the air removed before operation. This needs to be done manually by the pump operator for a non-self-priming pump each time the pump is used to avoid damage from dry running. A self-priming pump removes these issues by completing the priming process automatically. The air is removed from the inlet pipework and pump casing when the pump is activated. Self-priming pumps are particularly useful for installations with a suction lift on the inlet side of the pump, the pump will draw the fluid up the pipework by creating a vacuum and removing any air that is present. In ideal conditions, a self-priming pump can lift fluids up to around 8m on the inlet side, however this figure is affected by fluid viscosity, pipework bore and other installation conditions, therefore this figure can be much lower from case to case. Allowances must also be made for wear and tear; suction lift capabilities will be much lower for older and worn pumps.

What viscosity can this pump handle?

Please be aware that the figures displayed relate to the largest pump from this range of products, not specific models. For details on viscosity for specific models, please refer to datasheets or contact a member of our sales team.

How do I know what size pump and motor speed is correct for my application?

A clear picture of the pump system is required to make an accurate selection. The main pieces of information required include; a description of the application, bore of pipework, the fluid, viscosity, size and type of solids, flow rate and pressure/head. With these pieces of information, a pump can be sized correctly to ensure it delivers the required flow rate and pressure and that is also operates at its best efficiency point to lower lifetime costs. Knowing if the pump is running intermittently or continuously also allows the correct motor speed to be selected. For instance, a pump running continuously 24/7 will require a slower speed motor rather than a full speed motor. Running the motor slower and oversizing the pump will reduce wear of the motor and the pump, therefore lowering maintenance costs during their lifetime.

How does a bypass work and do I need one?

An integral bypass is designed to protect the pump and system from overpressure for small periods of time. It is typically set to around 10% higher than the working pressure, it will open and recirculate the fluid inside the pump head when the set pressure is achieved. An integral bypass is only a temporary solution and cannot operate indefinitely, an additional external bypass that runs back to the fluid source is always recommended as a more permanent solution.

What do the terms Atex and explosion proof mean and why are they so important?

ATEX is an abbreviation of “Atmospheres Explosibles”. It is a regulation set out by the European Union to ensure the safety of products that are used to handle flammable products or are installed in environments containing flammable gases, vapours, mists or combustible dusts. For instance, if the pump is being installed in an explosive environment, then only the motor needs to meet the Atex standard stopping it from causing a spark during operation and igniting the atmosphere. However, if the fluid being pumped is flammable, then the pump will also need to meet Atex standards to ensure that no sparks are caused inside the pump itself when the fluid goes through it. It is crucial that an Atex rated pump or motor are used for applications involving explosive environments or flammable fluids, using a non-Atex pump or motor in these situations is extremely dangerous and contravenes health and safety standards.

What is NPSH and why is it so important?

NPSH is an acronym for Net Positive Suction Head. NPSH measures the absolute pressure present in a fluid.

There are two main ways that NPSH is expressed in a pump system

NPSHa - This is the amount of Net Positive Suction Head available at the pump inlet. NPSHa demonstrates the amount of pressure acting on a fluid as it enters the pump. This measures the amount of pressure between the liquid staying in its current state and forming vapour bubbles (beginning to boil).

NPSHr - This is the amount of Net Positive Suction Head that the pump requires to operate without experiencing the damaging effect of cavitation, thus causing a dramatic reduction in pump performance.

It is very important to pay attention to these values when making a pump selection. Selecting a pump that requires more NPSH than is available in your system will cause fast and long-lasting damage to the pump and thus you will incur large repair costs and downtime.