GRUNDFOS DATA BOOKLET Shaft seals
Contents Type designation Type designation to EN 12756 Grundfos type designation Selection of shaft seals 3 5 7 7 7 8 8 8 9 11 12 13 14 Shaft seals in viscous liquids Shaft seals in viscous liquids Recommended shaft seals for viscous liquids 15 15 Seal face materials Seal face material combinations Tungsten carbide/tungsten carbide Silicon carbide/silicon carbide Carbon/tungsten carbide or carbon/silicon carbide Carbon/ceramic (aluminium oxide) Tungsten carbide/hybrid Silicon carbide 16 16 16 17 17 1
Type designation Shaft seals Type designation to EN 12756 Material key The EN standard describes the mechanical design of shaft seals and the combination of materials. The materials of the individual main components are indicated by means of a material code consisting of five letters. The EN 12756 standard contains Example • type key (1)U (2)B (3)E (4)G (5)G Material of rotating seal face • material key.
Type designation Standard codes for material versions Pos.
Type designation Shaft seals Grundfos type designation Position 1 codes Mechanical shaft seals are classified according to a Grundfos type designation based on the design of the shaft seal.
Type designation Shaft seals Position 4 codes Position 4 of the mechanical shaft seal variant code shows the secondary seal material.
Shaft seals in general What is a shaft seal Shaft seals Rotating shaft seals How are shaft seals used Shaft seals are used where the pumped liquid can damage the motor. Canned rotor type pumps have no shaft seals which means that the pumped liquid is allowed to enter the motor. Rotating shaft seals are used where two pump components move relative to one another. Rotating shaft seals include mechanical seals and soft seals (stuffing boxes, lip seals) among others.
Shaft seals in general Shaft seal components To obtain an acceptable surface pressure between the primary seal faces, shaft seals are available in two different designs: Static seal Seal driver with retaining ring Spring Shaft seals • balanced shaft seals • unbalanced shaft seals. Balanced shaft seal Spring retainer Secondary seal Seal face Seat TM02 6889 1903 The sketch below shows a balanced shaft seal with indication of the forces acting on the seal faces. A B Fig.
Shaft seals in general Seal balancing Shaft seals Calculation of the balancing K-factor: Calculation formulas 180 K = ---------150 Formula for calculation of the balancing K-factor: K = 1.2 Calculation of forces acting on the shaft seal: A K = ---B Formula for calculation of the closing force (FC): FC = ( A × P ) + FS Calculation of the closing force (FC): F C = ( 180 × 0.
Shaft seals in general Shaft seals Calculation of the efficient closing force (FC, eff.): F C, eff. = 165 – 60 F C, eff. = 105 [N] Calculation of the efficient seat load (Peff.): 105 P eff. = ---------150 P eff. = 0.70 [N/mm2] Calculation example, balanced shaft seal, Grundfos type K Data: 120 mm2 A B 150 mm2 FS 45 N P 0.8 N/mm2 Calculation of the balancing K-factor: 120 K = ---------150 K = 0.
Shaft seals in general Shaft seals For unbalanced shaft seals, the following applies: A K = ---- > 1 [-] B Key to symbols: K Area ratio A The hydraulically loaded area in mm2 B Contact face in mm2 How does a shaft seal work The functioning of a shaft seal depends on the formation of a load-carrying lubricating film between the seal faces during pump operation. The lubricating film is formed by the pumped liquid or an external liquid.
Shaft seals in general The seal faces of a shaft seal are lubricated by the pumped liquid. Thus, better lubrication means less friction and increased leakage. Conversely, less leakage means worse lubrication conditions and increased friction. The following factors contribute to the power consumption ("power loss") of a shaft seal: • The centrifugal pumping action of the rotating parts. The power consumption increases dramatically with the speed of rotation (to the third power).
Shaft seals in general Shaft seals According to the figure below, the lubricating film can be pumped to the pumped liquid side or to the atmosphere side, depending on the direction of the scratches on the surface. O-ring TM00 2581 4593 Leakage rate [ml/h] 4.5 4 3.5 3 Fig. 15 O-ring shaft seal 2.5 Advantages and disadvantages 2 Advantages: 1.5 Suitable in hot water and high pressure applications. 0.5 0 0 0.05 0.1 0.15 0.2 Roughness [Ra] TM02 7454 3603 1 Fig.
Shaft seals in general Shaft seals Cartridge shaft seals Metal bellows shaft seals In an ordinary mechanical seal, the spring produces the closing force required to close the seal faces. In a metal bellows mechanical seal the spring has been replaced by a metal bellows with a similar force. TM02 7100 2603 Metal bellows act both as a dynamic seal between the rotating ring and the shaft and as a spring. The stainless steel are corrugated to give the desired spring force. Fig.
Shaft seals in viscous liquids Shaft seals in viscous liquids With the basic principles of the mechanical shaft seal in mind, it seems logical that a high-viscous liquid creates a thicker liquid film with better lubricating properties. However, the following shaft seal problems may occur when pumping viscous liquids: • If it has a vapour pressure lower than that of water at room temperature, the viscous liquid will not evaporate. Consequently, it accumulates around the shaft seal.
Seal face materials Shaft seals Seal face material combinations The material combination has the following features: The choice of seal face materials is decisive of the function and life of the mechanical shaft seal. Below is a description of the possible material combinations. • Extremely wear resistant. Noise is generated as a result of the poor lubricating conditions in seals in connection with low-viscosity liquids. The viscosity of water decreases with increasing temperature.
Seal face materials Shaft seals Q1G, self-lubricating, sintered SiC Several variants of SiC materials containing dry lubricants are available on the market. In this document, the designation Q1G applies to a SiC material which is suitable for use in distilled or demineralized water, as opposed to the above materials. • With reduced mechanical strength, but higher corrosion resistance, synthetic resin-impregnated carbon (B) covers a wide application field.
Seal face materials Silicon carbide The ceramic silicon carbide (SiC) has been manufactured for many years. There are three main types of SiC: • Reaction-bonded and liquid-phase sintered grades have limited corrosion resistance in alkaline water due to the content of free silicon. Shaft seals During the last 15 years almost 50 different SiC grades have been tested at Grundfos and categorized in groups according to performance. Qs is a conventional dense-sintered SiC with a porosity of less than 2%.
Seal face materials Shaft seals Performance in hot water The lubrication of the seal faces in hot water is scarce due to the low viscosity of water at high temperatures and evaporation in the seal gap. Limits of temperature and pressure ranges are based on tests where factors such as friction, torque and leakage are measured. Above these limits noise from the seals may be expected and fatique wear may occur.
Seal face materials Shaft seals Leak rate (comparative) Q S Q P 6 5 2,000 ppm sand It is not recommended to use a porous SiC seal face against a carbon face in water containing a high level of dissolved solids. Abrasive wear may be observed on seals with hard seal faces in corrosive liquids. Wear on SiC may occur in demineralised water due to corrosion in grain boundaries. Wear on SiC faces may occur in hot water.
Seal face materials Shaft seals Chemical adhesion of surfaces Failures [%] 0 2000 4000 6000 8000 10000 TM02 7288 3203 100 90 80 70 60 50 40 30 20 10 0 12000 [hour] Fig. 28 Failure of SiC seals in demineralised water Seizure of seal faces caused by storing Very smooth and flat seal faces will easily adhere to each other. In extreme situations the adhesion becomes so strong that the shaft on the motor of the pump cannot rotate.
Materials of secondary seals Secondary seals The choice of materials for secondary seals, i.e. rubber components such as O-rings and bellows, is just as important as the choice of seal face combinations. Both are essential to the functioning of the mechanical shaft seal. The Grundfos seals are intended to cover a wide application field with few materials. FKM FKM rubber covers a very wide range of liquids and temperatures.
Materials of secondary seals FXM FXM (fluorinated copolymer) is particularly suitable for extremely high temperatures and pressures as well as for use in acid liquids and gasses within oil and gas extraction (in boreholes, on land and at sea). Its resistance to chemicals and high temperatures has been considerably improved as compared to fluorized rubber, with excellent resistance to hot water and steam.
Types of shaft seals Shaft seals Types of shaft seals Suitability The following pages give a short description of some of Grundfos’ mechanical shaft seal types, including their application profiles. Due to the wear on carbon seal faces, the description of carbon shaft seal types includes a table indicating service intervals.
Types of shaft seals Shaft seals Grundfos type B Suitability Grundfos type B seal is defined as a bellows seal with rubber bellows. Description/features • Suitable for lime- and sludge-containing liquids where there is a risk of deposits and seizure. Suitable Suitable under certain conditions Not suitable Alkaline liquids Acid liquids Dry running • Resists fretting (wear corrosion) which occurs when an O-ring wears the protective oxide film of a stainless steel shaft.
Types of shaft seals Shaft seals Type B with SiC/SiC seal faces (Q1G/Q1G) Type B with SiC/carbon seal faces There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile. There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile.
Types of shaft seals Shaft seals Grundfos type C Pressure-temperature diagram Grundfos type C seal is defined as a O-ring seal with a spring as seal driver. The pressure-temperature diagram is based on clean water. Description/features • Simple seal for low pressure and temperature ranges. The figures in the following table refer to the pressuretemperature diagram. Recommended service intervals [operating hours] before wear-out 1 14,000 - 20,000 2 8,000 - 15,000 TM00 2592 3097 Pos.
Types of shaft seals Shaft seals Grundfos type D Type D with SiC/SiC seal faces Grundfos type D seal is defined as a balanced O-ring seal. There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile. Description/features • The design of the shaft seal makes it an ideal solution when pumping solid-containing and high-viscosity liquids. • The shaft seal is independent of the direction of rotation.
Types of shaft seals Shaft seals Grundfos type E Type E with tungsten carbide/hybrid seal faces Grundfos type E seal is defined as a O-ring seal, type A, cartridge type. There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile. Description/features • Strong seal drivers transmit the torque even under extreme operating conditions. • Risk of fretting (wear corrosion) in corrosive liquids.
Types of shaft seals Shaft seals Type E with tungsten carbide/tungsten carbide seal faces There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile. Type E with tungsten carbide/carbon seal faces There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile.
Types of shaft seals Shaft seals Grundfos type G Grundfos type G seal is defined as an unbalanced Oring seal with a rubber bellows. Description/features • Especially suitable for anti-freeze liquids or liquids containing large quantities of solid or precipitated particles. • Suitable for lime- and sludge-containing liquids where there is a risk of deposits and seizure. • Resists fretting (wear corrosion) which occurs when an O-ring wears the protective oxide film of a stainless steel shaft.
Types of shaft seals Shaft seals Pressure-temperature diagram The pressure-temperature diagram is based on clean water. At temperatures below freezing point the diagram is based on a mixture of water and glycol. p [bar] 20 15 5 0 -20 0 20 40 60 80 100 Fig.
Types of shaft seals Shaft seals Grundfos type H Suitability Grundfos type H seal is defined as an O-ring seal of the cartridge type. Description/features • Thanks to the balanced seal design, this robust seal is suitable for pressures up to 30 bar. • Can be replaced without dismantling the pump part. • Easy to replace during service. • Risk of fretting (wear corrosion) in corrosive liquids. Fretting occurs when an O-ring wears the protective oxide film of a stainless steel shaft.
Types of shaft seals Shaft seals Type H for ø12, ø16 and ø22 mm shaft with SiC/ carbon seal faces Type H for ø12, ø16 and ø22 mm shaft with tungsten carbide/carbon seal faces Suitable for use in CR/CRI/CRN pumps, the seal is recommended for use in very hot water (above 100°C). Can be replaced without dismantling the pump part. Suitable for use in CR/CRI/CRN pumps, the seal is recommended for use in very hot water (above 100°C). Can be replaced without dismantling the pump part.
Types of shaft seals Type H for ø12, ø16 and ø22 mm shaft with tungsten carbide/tungsten carbide seal faces • The seal is suitable for use in CR/CRI/CRN pumps for many applications, except for very hot water (above +100°C). Can be replaced without dismantling the pump part. • The strong seal carriers contribute considerably to the cooling of the seal faces in case of dry running. This makes the seal capable of withstanding several minutes of dry running, despite the seal face material combination.
Types of shaft seals Shaft seals Grundfos type K Type K with tungsten carbide/carbon seal faces Grundfos type K seal is defined as a metal bellows seal (type M, cartridge type). There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile. Description/features • Especially suitable for liquids containing large quantities of precipitated particles. Suitability • The seal is suitable for temperatures above +100°C.
Types of shaft seals Shaft seals Type K with tungsten carbide/hybrid seal faces There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile. Suitability Type K with tungsten carbide/tungsten carbide seal faces There is no relation between the indication of suitability and the pressure-temperature diagram, but together they form the application profile.
Types of shaft seals Shaft seals Grundfos type R Pressure-temperature diagram Grundfos type K seal is defined as an O-ring seal, type A, with fixed seal driver and reduced seal face. The pressure-temperature diagram is based on clean water. At temperatures below freezing point, the diagram is based on a mixture of water and glycol. Description/features • Especially suitable for anti-freeze liquids or liquids containing large quantities of solid or precipitated particles.
Types of shaft seals Shaft seals Seal arrangements The double seal mounted back-to-back is used in Grundfos offers the following types of double seals: • paint industries • distilling industries • Double seal mounted back-to-back, Grundfos type O • petrochemical industries. • Double seal mounted in tandem, Grundfos type P • Cartex-DE seal, Grundfos type Q. Double seal (tandem) Grundfos type P seal is defined as two seals mounted in a tandem arrangement.
Types of shaft seals Shaft seals Applications Tandem arrangement Double seals mounted in tandem are recommended for crystallising, hardening or sticky liquids in PP • negative pressure deaeration systems (vacuum) Back-to-back arrangement • industries handling potentially hardening oil products • industries producing caustic soda (sodium hydroxide - NaOH) PF O-ring PP O-ring • industries producing hydrated lime (calcium hydroxide - Ca(OH)2 PF TM02 7449 3503 • pharmaceutical industries (i.e.
Types of shaft seals Shaft seals 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 I/h TM02 7402 3503 Air-cooled top (for high temperatures) DW 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 Fig. 62 Circulation volume of Cartex-DE Application profiles GR5228 The Cartex-DE shaft seal has the following application profiles: • carbon graphite/SiC • SiC/SiC. Fig.
Types of shaft seals Shaft seals As the temperature in the seal chamber does not exceed +120°C during operation, a standard Grundfos shaft seal can be used. The Grundfos air-cooled top does not require any external cooling. An automatic air vent is required to vent the pump seal chamber. Air vent Shaft seal Liquid Pipe Air chamber • • • • • • • • • TM01 4785 0899 Bush Fig.
Types of shaft seals Shaft seals Comparing seal types The comparison is based on a seal design for maximum 16 bar without considering seal face and secondary seal materials, as they have been dealt with separately. The asterisks indicate degree of suitability with respect to the parameters stated, five asterisks being the optimum suitability.
Selection of shaft seals Selection of the most suitable shaft seal The list of pumped liquids in a data booklet often indicates several suitable shaft seals for the pumping of the same liquid. As the properties of the suitable shaft seals often differ, the purpose of this section is to give an example of how to select the most suitable shaft seal.
Pumped liquids Shaft seals Lists of pumped liquids The following tables indicate the suitability of the individual shaft seals in various pumped liquids. The suitability only applies to the mechanical shaft seal and is not related to pumps in general. The suitability of the individual seal combinations is based on the information on temperature, concentration, etc. given in the tables. Changes in these conditions will affect the suitability of the seal.
Pumped liquids Shaft seals Acids Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Acetic acid CH3COOH Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Max. temp. [°C] 20 20 20 Max. conc. [%] 5 5 5 Suitability ++ Q Q V G G – B Q E G G + B Q V G G – B V E G G – B V V G G – U U E G G ± U U V G G B U E G G B U V G G 20 5 – ± Comments Acetic anhydride (CH3CO)2O Max.
Pumped liquids Shaft seals Acids, continued Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Salicylic acid C6H4(OH)COOH Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Q Q V G G B Q E G G B Q V G G Max. temp. [°C] 80 80 80 Max. conc.
Pumped liquids Shaft seals Alkalis Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Alkaline degreasing agent Rotating face: Stationary seat: Secondary seal: Spring: Other parts: B V V G G U U E G G U U V G G B U E G G 60 80 60 10 25 10 Suitability ++ – + – – – ++ – + 20 20 20 20 Max. conc. [%] 100 100 100 100 Suitability ± – ++ – ± 90 120 90 Max. conc.
Pumped liquids Shaft seals Salts Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Ammonium bicarbonate NH4 Rotating face: Stationary seat: Secondary seal: Spring: Other parts: B Q E G G B Q V G G B V E G G B V V G G U U E G G U U V G G B U E G G 60 60 60 60 60 Max. conc. [%] 20 20 20 20 20 Suitability ++ – + – + – B U V G G ++ – + – 20 Decomposes in hot water. Max. temp.
Pumped liquids Shaft seals Salts, continued Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Sodium nitrite NaNO2 Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Q Q V G G B Q E G G B Q V G G B V E G G B V V G G U U E G G U U V G G B U E G G B U V G G Max. temp. [°C] 90 90 90 90 90 90 90 90 90 90 Max. conc.
Pumped liquids Shaft seals Water Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Max. temp. [°C] Boiler feed water Q Q V G G 120 B Q E G G B Q V G G B V E G G B V V G G 140 80 90 80 + ± + + U U E G G U U V G G B U E G G B U V G G 140 80 + + Max. conc. [%] Suitability Comments Max. temp.
Pumped liquids Shaft seals Coolants Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Calcium chloride CaCl2 Rotating face: Stationary seat: Secondary seal: Spring: Other parts: B V V G G U U E G G U U V G G 5 5 5 35 35 35 ++ + ++ + Suitability – – – – B U E G G B U V G G – – Shaft seal with flush/double shaft seal may be required if the liquid contains additives; presence of oxygen entails risk of pitt
Pumped liquids Shaft seals Fuels Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Q Q V G G B Q E G G Max. temp. [°C] B Q V G G B V E G G 60 B V V G G U U E G G U U V G G B U E G G 60 B U V G G 60 Max. conc.
Pumped liquids Shaft seals Synthetic and mineral oils Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Max. temp. [°C] Q Q V G G B Q E G G 20 B Q V G G B V E G G B V V G G U U E G G 20 U U V G G B U E G G 20 B U V G G 20 Max. conc. [%] Crude oil Suitability Comments – Max. temp.
Pumped liquids Shaft seals Vegetable oils Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Max. temp.
Pumped liquids Shaft seals Solvents Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Acetone (dimethyl ketone) CH3COCH3 Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G B Q E G G B Q V G G B V E G G B V V G G U U E G G U U V G G B U E G G Max. temp. [°C] 60 60 60 Max. conc.
Pumped liquids Shaft seals Oxidants Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Hydrogen peroxide H 2O 2 Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q V G G B Q E G G B Q V G G B V E G G B V V G G Max. temp. [°C] 20 20 20 20 20 20 Max. conc.
Pumped liquids Shaft seals Organic compounds Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Q Q V G G B Q E G G B Q V G G B V E G G B V V G G U U E G G U U V G G B U E G G B U V G G – – – – – – – – – – Max. temp. [°C] Benzene (petroleum naphtha) C 6H 6 Max. conc. [%] Suitability Comments Butanol (butyl alcohol) C4H7OH Max.
Pumped liquids Shaft seals Miscellaneous Legend ++ + = Best solution = Suitable ± = Suitable under certain conditions – = Not suitable Shaft seal (EN 12756) Liquid Cider Rotating face: Stationary seat: Secondary seal: Spring: Other parts: Q Q E G G Q Q V G G B Q E G G B Q V G G B V E G G B V V G G U U E G G U U V G G B U E G G B U V G G Max. temp. [°C] 90 60 120 60 90 60 90 60 120 60 + + ++ + + + + + ++ + Max. conc. [%] Suitability Comments Sugar Max. temp.
Failure analysis Shaft seals Shaft seal failure analysis guide The table below is intended as a general guide of typical seal failures. On the following pages are examples of the most common causes of seal failures.
Seal failure analysis Shaft seals Key to failure analysis Failure number Description of possible causes of failure 1 Seal opens due to differential expansion between stationary and rotating parts, caused by deposits preventing the rotating ring from moving axially on the shaft. 2 Seal is not set to correct working length, resulting in no contact between face and seat. 3 Seal faces are running dry, resulting in overheating.
Further product documentation Shaft seals WebCAPS WebCAPS is a Web-based Computer Aided Product Selection program available on www.grundfos.com. WebCAPS contains detailed information on more than 185,000 Grundfos products in more than 20 languages. In WebCAPS, all information is divided into 6 sections: • Catalogue • Literature • Service • Sizing • Replacement • CAD drawings.
Further product documentation Shaft seals Sizing 0 1 This section is based on different fields of application and installation examples, and gives easy step-by-step instructions in how to • select the most suitable and efficient pump for your installation • carry out advanced calculations based on energy consumption, payback periods, load profiles, life cycle costs, etc. • analyse your selected pump via the built-in life cycle cost tool • determine the flow velocity in wastewater applications, etc.
Being responsible is our foundation Thinking ahead makes it possible Innovation is the essence 96519875 1006 Repl. 96519875 0104 GB GRUNDFOS A/S . DK-8850 Bjerringbro . Denmark Telephone: +45 87 50 14 00 www.grundfos.com Subject to alterations.
