Wet rotor type. Glandless rotor pump: operating principle

Glanded rotor pumps are used to supply liquids with high pressure. They are best suited for supplying coolant and aggressive media. Unlike glandless pumps, in these pumps the liquid does not come into contact with the motor.

Another difference from glandless pumps is the way the pump body/shaft is insulated. This is achieved using stuffing box or sliding mechanical seals (STU).

Standard glanded rotor pumps typically use three-phase constant speed motors. As a rule, they are regulated through external electronic system speed control. Today, dry rotor pumps are available with a built-in electronic speed control unit, which, thanks to modern technology Can also be installed on motors with high power output.

The overall efficiency of dry rotor pumps is significantly higher than that of wet rotor pumps. Glanded rotor pumps are divided into three main types:

In-line pumps
Pumps in which the suction and discharge pipes are on the same axis and have the same nominal diameter are called in-line pumps. In-line pumps are equipped with standard air-cooled flange electric motors. This type of pump is considered most suitable for building systems that require high power output. These pumps are installed directly on the pipeline. In this case, the pipeline is secured with brackets or the pump is installed on a foundation or a separate bracket.

Block pumps
Block pumps are low-pressure, constant-speed centrifugal pumps with a standard air-cooled electric motor. The liquid enters the pump in the axial direction and exits in the radial direction. Brackets or supports for the motor are included as standard with the pumps.

Cantilever pumps
Data centrifugal pumps have an axial inlet and radial outlet of liquid from the pump. The pump and motor have independent mounting units. Therefore they are installed on a foundation slab.

Depending on the fluid and operating conditions, they can be equipped with a STU or gland seal. The nominal bore of such pumps is determined by the pressure pipe. The suction pipe has a larger nominal bore.

Shaft seal
The shaft can be sealed (as standard or as an option, in the case of cantilever pumps) from the atmosphere using STU or a gland seal. Below is a description of these two types of seals.

STU pump with dry rotor

Mechanical seals
The mechanical seal design is based on two rings with carefully polished surfaces. They are pressed against each other using a spring and work together. STU are dynamic seals and are used to seal a shaft rotating in a liquid at high operating pressures. The STU consists of two polished wear-resistant rings (for example, silicone or graphite), which are pressed against each other by axial forces.

One ring (dynamic) rotates with the shaft, while the other ring (static) is fixedly fixed in the housing. A thin film of water forms between the sliding surfaces, serving as a lubricant and cooling agent. Depending on the operating mode of the pump, several types of friction of the mating surfaces are possible: mixed friction, boundary friction or dry friction, and the latter (occurring in the absence of a lubricating film) causes immediate destruction of the surfaces.

The service life depends on operating conditions such as the composition and temperature of the working fluid.

Gland seals
The materials used for glands are high-quality synthetic fiber yarns such as Kevlar® or Twaron®, PTFE, porous graphite yarns, synthetic mineral fiber yarns, and natural fibers such as hemp, wadding or ramie.

Material for oil seals is produced in the form of threads or compressed skeins, dry or with special impregnation, depending on the purpose. If the material is purchased in the form of threads, you first need to form a ring and give it shape. The seal ring is then wrapped around the pump shaft and tightened using a crimp sleeve.

Installation types

Acceptable installation methods
In-line pumps are designed for horizontal and vertical installation directly on the pipeline.
To dismantle the motor and pump elements, sufficient space must be left.
When connecting pipelines, the stress and weight of the pipelines should not be transferred to the pump, and the pump should be installed on supports (if any).

Unacceptable installation methods
Installation with the motor and terminal box pointing downwards is not permitted.
If the motor power exceeds a certain level, before installing the pump in horizontal position the manufacturer should be consulted.

- Cross-section of a centrifugal pump high pressure
- Characteristics of high pressure centrifugal pump

High pressure centrifugal pumps

These pumps are usually multi-stage. The flow rate of the pump depends on the size of the impeller and other factors. The pressure in high-pressure centrifugal pumps is achieved by using several impellers installed in series. Kinetic energy is converted into pressure partly in the working and partly in the straightening apparatus.

Thanks to the ability to vary the number of stages, high-pressure centrifugal pumps develop higher pressures compared to low-pressure single-stage centrifugal pumps.

Some pumps have up to 20 stages. Thus, they can provide a head of up to 250 m. Almost all of the high pressure centrifugal pumps that we have described belong to the dry rotor pump family. However, in Lately Manufacturers successfully equip them with wet rotor motors.

Special instructions for block pumps
Block pumps must be installed on suitable foundations or brackets.
Installation of a block pump with the motor and terminal box facing downwards is not permitted. All other installation methods are considered acceptable.
For detailed information on installation methods, see the installation and operating instructions.

Pump installed in the heating system.

A wet rotor circulation pump is an element of the heating system designed to circulate coolant through the heating circuit.

Design

The pump device consists of a cast iron casing in which an electric motor rotates a composite wheel mounted on a shaft. The wheel consists of two disks, between which curved blades are located radially. The coolant enters the wheel through a hole in the lower disk.

In wet running models, all moving parts (including the motor rotor) are in contact with the coolant, which will act as a lubricant/cooler for the ceramic (graphite) end bearings and the rotor itself. In this case, the stator is isolated from the coolant using a metal partition with sealing gaskets.

The design of “wet” pumps is more complex than the design of pumps with a dry rotor, so their cost with equal characteristics will always be higher.

Note! As a rule, circulation pumps have 3 speeds, which are switched by turning the regulator to one of three speeds. At the same time, at minimum speed, the pump consumes approximately 2 times less electricity compared to maximum speed.

Installation

Installation circulation pump for a heating system, like any other heating equipment, must be carried out in accordance with the installation manual, as well as in accordance with the project heating system. However, there are some General requirements for installing a circulation pump:

• The direction of movement of the coolant must coincide with the direction indicated by the arrow on the body;
• The pump must be installed between the boiler and the heating circuit (but not between the radiators). It can be installed on both the supply and return lines, but preference is given to the return pipeline. The specific installation location must be easily accessible, because during operation, it may require maintenance or replacement in case of failure;
• Do not place thermal insulation on the engine compartment;
• After a wet rotor circulation pump is recommended, which in case of emergency situation, will prevent the coolant from moving in the opposite direction;
• Before and after the pump it is necessary to install shut-off valves. In case of breakdown, shut-off valves will allow you to remove/replace the device without draining the coolant from the system;
• It is recommended to install anti-vibration inserts before and after it. This does not apply to small pumps;
• After installation, the housing should not experience pressure from the connected pipes. When installing a circulation pump on relatively long pipelines, it is recommended to fix both the pipes themselves and the pump. This will reduce negative impact vibrations;

Note! It is necessary to install a strainer in front of the pump, which will reduce the likelihood of damage to the mechanisms by various mechanical particles (sand, rust, scale or other sludge). In addition, its correct location will allow it to avoid contamination by such particles; it should not be installed in the lowest section of the heating system.

• Installation of a circulation pump with a wet rotor in highest point system may cause air to enter frequently. If, nevertheless, air has accumulated in it, it is necessary to slowly unscrew the air bleed screw using a screwdriver or a coin and allow the coolant to flow out for 2-4 seconds;

• To support the circulation pump for the heating system, it is prohibited to use wooden (or made from any other fire hazardous material) supports, because during operation, the housing can heat up to a temperature of +124°C, so such supports may catch fire;

Note! You should always remember that the casing of a running pump heats up to high temperatures and there is a possibility of burns upon contact with it.

• If the heating system has just been installed, before operation it is recommended to rinse it with water at a temperature of 80-85°C, then drain the water and only then fill the system with “permanent” coolant. This will remove all contaminants that may have entered the heating circuit during installation work;
• The motor shaft must always be in a horizontal position.

Wilo pump on the underfloor heating distribution manifold.

Electrical part

• The electrical connection must be carried out by a trained specialist in accordance with the connection diagram, which is in the instructions and installation manuals.
• The terminal box should not be directed downwards, because In the event of a leak, coolant may enter it. In addition, in this position it is inconvenient to maintain.
• The pump must be grounded.

High noise levels during operation of a wet rotor circulation pump can be caused by:

1. presence of air;
2. low suction pressure;
3. too high coolant speed;
4. mechanical particles have entered moving parts.

Video

Glandless rotor pumps, which can be purchased in Moscow at a budget price in the EGM-SHOP.ru online store, are designed to complete autonomous heating, hot water supply and air conditioning systems low-rise residential buildings and cottages.

Their main purpose is to maintain uninterrupted coolant circulation for the most efficient distribution of thermal energy and timely delivery hot water to water consumption points.

Design of DAB glandless pumps

The name of circulation pumps with a wet rotor reflects their key design feature- rotation rotor in the pumped coolant, thereby ensuring cooling electric drive and lubricants bearings.

For guard stator a special system is provided to prevent coolant from entering separating glass carbon fiber or stainless steel.

Advantages of DAB circulation pumps with a wet rotor

• A wide range of models and designs, from simple inexpensive to energy-efficient frequency-controlled;
• Three speed modes allowing you to adjust the heating speed of any room;
• Low noise level during operation;
• Light weight and compact dimensions;
• Long period of non-stop work;
• Quick and easy installation and configuration;
• Minimal maintenance;
• High maintainability.

In addition, pumps for circulating water and increasing pressure in the heating system, equipped with a wet rotor, reduce costs for space heating and hot water supply. They consume less energy and are designed to complete pipelines with a smaller cross-section, which allows rational consumption of heat due to the rapid and intensive movement of the coolant.

Many people thought that for domestic use it was necessary to use circulation pumps with a wet rotor. Dry rotor circulation pumps have been used for industrial use.

There was an opinion that dry rotor pumps were too big sizes and make a lot of noise. However, large manufacturers have increasingly begun to produce household models of circulation pumps with a dry rotor.

In industry, circulation pumps with a dry rotor are used.

In the domestic version, circulation pumps with a wet and dry rotor are used. For production needs, wet rotor pumps are not used, since they can be produced with a power of up to 3 kW and they are not widely used.

The advantages of circulation pumps with a dry rotor of industrial design: the quality of the coolant does not matter for them, they have good maintainability. The disadvantage of these pumps is that they are large, make a lot of noise, so they are installed in separate rooms, and consume a lot of electricity.

As for the domestic version of a pump with a dry rotor, its advantages:

has higher efficiency;

the purity of the coolant is not important to him;

has good maintainability, and spare parts are cheaper than pumps with a wet rotor;

The dimensions are almost no different from the wet-rotor analogue.

The downside is a lot of noise during operation and the need to regularly replace the mechanical seal.

The disadvantages of circulation pumps with a dry rotor are advantages for a pump with a wet rotor: silent, does not have a mechanical seal. The disadvantage is that the quality of the coolant is great importance during operation. The worse the quality of the pumped liquid, the faster the pump can fail.

Taking into account all the pros and cons of the pumps considered, we can draw the appropriate conclusions. If the quality of the coolant is not important to you, then it is better to choose a pump with a wet rotor, but you do not know what will happen to the rest of the heating system.

If you want everything to work smoothly, it is better to use a motor with a dry rotor, but you must take care of the quality of the coolant.

Regarding noise, everyone decides for themselves, because the pump does not come into view so often. Efficiency is not so important, since the difference in percentage is small, but the absence of the need to replace the mechanical seal is a big plus.

But maintenance should be carried out regularly along with an inspection of the entire heating system by a specialist.

What is a pump rotor

Pump rotor This is a separate assembly unit, which largely determines the efficiency, reliability and durability of the pump.

The basic part of the circulation pump rotor is a shaft on which an impeller, protective bushings, a seal, parts of a hydraulic unloader, a coupling half and other small parts mounted on the shaft are installed.

At the end of the rotor, an impeller is fixed, which is secured against displacement in the axial direction with a nut or fairing (depending on the type and design of the pump).

Glandless rotor pump

Structurally, in a pump with a “wet” rotor, the working fluid moves in the cavity between the rotor and stator. In this case, to avoid short circuits, the rotor and stator are protected with special cylinders (jackets) made of stainless steel. The working medium in this case lubricates the surfaces of the rubbing parts of the pump, such as bearings, and at the same time cools them.

The advantages of a wet rotor pump include high reliability; such pumps are almost silent and have a long service life.

The disadvantages of such pumps with a wet rotor include low efficiency, on average up to 50%, which decreases as a result large quantity partitions between the rotor and stator. Low efficiency leads to increased energy consumption.

Dry rotor pump

In pumps with a dry rotor, there is no contact between the rotor and the working medium. Movable sealed mechanical seals or non-sealed stuffing box seals are installed between the engine and the working environment.

The advantages of a pump with a dry rotor include high efficiency, up to 80%, and therefore relatively low energy costs.

The disadvantages of a dry rotor pump include high level noise, therefore such pumps are installed in separate sound-insulated rooms.

Modern pumps with wet and dry rotor.

Currently, many manufacturers, both foreign and domestic, provide circulation pumps with wet and dry rotor types. Such pumps are used in most cases for installation in heating and air conditioning systems.

The pumps are capable of pumping media with temperatures up to 110 degrees Celsius, at pressures up to 10 atm.

Pump body material is cast iron. The pumps are available in both single-speed and multi-speed versions and have low level noise.

To provide heating for the house, circulation pumps with a wet rotor are used.

Particularly popular are wilo wet rotor pumps of the Star-RS, TOP-RL, etc. series.

And Grundfos wet rotor pumps of the ALPHA2, ALPHA3 series, etc.

But in addition to their compact size and low power, such pumps are still not capable of heating truly large rooms.

This requires, for example, dry rotor pumps from the wilo BL series. Or dry rotor pumps from the Grundfos TP series.

Is it worth installing such pumps?

Should I buy a wet rotor pump or a dry rotor pump? This question may arise for any person who is thinking about creating uninterrupted coolant circulation in the heating system of a cottage or private home.

When operating, each pump with any type of rotor forces fluid to move through pipes. As a result of this impact you get:
constant temperature of heating radiators anywhere in your home;
removal of air pockets from the pipeline system, and as a result, elimination of water hammer;
saving budget and electricity for heating the coolant.

Pump rotor design

In a wide variety pumping equipment One or more impellers can be installed on the rotors of pumps of different types and purposes. A pump with one impeller is called a single-stage pump; if several impellers are installed, the pump is multi-stage.

If the impeller and the electric motor drive are installed on one (common) shaft, then this type of pump is called cantilever.

In industrial applications, the most common options are when the pump shaft and the motor shaft are connected by coupling halves, which are fastened together with rubberized steel cylinders/screws - “fingers”.

Most of the rotor parts are keyed onto the shaft. Parts installed without a keyed connection must be securely secured against rotation.

The absence of noise and vibration during pump operation is ensured by balancing the rotor assembly. This requirement is met through careful static balancing of individual rotor parts and subsequent dynamic (during rotation) balancing of the assembled rotor.

The most suitable pump rotor design to ensure balance is non-separable. A non-separable design is a design in which the impeller is mounted on the shaft with interference.

Wheel tension to circulation pump rotor provide heating of the impeller or cooling of the rotor.

In the vast majority of pumps at rotation speeds up to 3000 rpm, a collapsible rotor design is used, in which the wheel is mounted on the shaft using a movable fit on keys. The impeller in this case is installed in a sliding or tight fit, which ensures the minimum possible clearances.

Pump rotor material

The most common material for the pump rotor shaft is carbon steel grades 35 and 45, as well as structural alloy steel 40Х or 40 ХН. For corrosive liquids, shafts made of 3X13 stainless steel are used.

If the pump design requires the use of plain bearings with bobbitt filling, protective sleeves made of carbon steel should be installed on the shaft journals, since stainless steel is capable of scoring.

The protective sleeves are either screwed onto the shaft or pressed axially with round nuts. The thread direction must be selected taking into account the direction of shaft rotation to prevent self-unscrewing during operation.

All options for heating pumps from the most popular manufacturers with the ability to select them for specific parameters