Pipes, Pipe Fittings and Valves PDF

SUMMARY-2024-2025--Pipes, Pipe fittings and Valves Pipes, Pipe fittings − Ship pipes and fittings are essential components in the design and operation of marine systems. − Ship pipes and fittings must meet specific engineering standards to ensure safety, reliability, and efficiency. − The m...

SUMMARY-2024-2025--Pipes, Pipe fittings and Valves Pipes, Pipe fittings − Ship pipes and fittings are essential components in the design and operation of marine systems. − Ship pipes and fittings must meet specific engineering standards to ensure safety, reliability, and efficiency. − The majority of ships’ pipes are made of mild steel. − Flow rate, viscosity and pressure of fluid being carried determine a pipe’s diameter. − Pipes in areas of a ship where there is a risk of gas explosion are earthed because fluid flow can build up a static electricity charge. − Pipes, especially open-ended ones, compromise the integrity of the compartments they pass through. − The water circulating in cooling pipes will corrode them over time. − Pipes passing through tanks containing liquid are exposed to corrosive attack on both surfaces. − Liquid flowing quickly will be turbulent as a result of fluid separation and cavitation. − Flow turbulence in a pipe will cause pitting. − A pipe with the correct diameter for the job will eliminate turbulence. − Pipes can be joined by butt-welding, with flange connections or mechanical joints. − The use of expansion mechanical joints is restricted to locations where pipes move because of thermal expansion or contraction, or ship bending. − Classification society rules prohibit expansion mechanical joints to use for the connection of cargo piping in chemical tankers. − The most common expansion joints are compression couplings or slip-on joints. − A pressure test of 1.5 times design pressure is a strength test − A test at the design pressure is a tightness test. − Pressure testing can show the small cracks and holes that will not be found by a visual examination. − Pipes are held in place by supports or clips that prevent movement from shock loads and vibration. − Pipe failure is common when pipes are allowed to vibrate.. − Mechanical joints are not normally fitted on pipes carrying flammable liquids. Pipe classification Class I : pipes have to comply with the most stringent rules. They include fuel oil pipes operating above 16 bar pressure or above 150 ºC, and steam pipes where the temperature exceeds 300ºC. Class II : pipes fall between the two rule requirements. Class III : pipes have the lowest requirements. They include fuel pipes that operate at or below 7 bar pressure and 60 ºC. Regulatory Compliance − Ship classification societies publish regulations for the design and installation of ship piping systems, defining, 1  strength, materials, system requirements, testing procedures, surveying requirements pipes to be inspected during annual, intermediate and renewal surveys. Cretaria in designing Engine Room Piping Layout − Pressure rating − Temperature rating − Corrosion resistance − Protective Coatings − Vibration and Movement − Support and Clamping Ship piping systems Bilge system Ballast system Fire mains system Sprinkler systems Inert gas (IG) piping CO 2 piping 2 Foam system Dry powder system Cargo piping-tankers Hydraulic piping systems Chemicals piping Sounding pipes Steam system Compressed air system 3 Lubricating oil system Refrigeration plant Air-conditioning system Freshwater system Seawater systems in general Pipe Materials − Pipes that carry dangerous chemicals or particularly corrosive fluids are manufactured from stainless steel. − Some seawater pipes are copper, − Most pipes are made of mild steel. − Plastic pipes are used in, applications where corrosion resistance and lightweight properties are advantageous. freshwater systems and some chemical transport, ballast, brine and sanitary systems. − Composite Pipes are combine materials like fiberglass with resin. They are used for lightweight, corrosion-resistant applications in demanding environments. − Carbon steel pipes are commonly used for general applications where high strength and durability are needed. They are typically used for fuel oil and water systems. − Alloy Steel pipes are used for high-temperature applications such as exhaust systems and steam pipes. 4 − Stainless Steel pipes have excellent corrosion resistance so they are used in seawater systems, and where high hygiene standards are required. Oil Pipes Boiler Pipes Chemical Pipes Drill Pipes Causes of pipe failure Water hammer Low temperature Expansion Pipe alignment Pipe Corrosion and Erosion − The majority of ships’ pipes are constructed of ferrous material, a material that is attacked by all forms of corrosion. − Galvanic corrosion is a major challenge for any pipes which carry sea water. − Galvanic corrosion can occur if the different metals are connected electrically and mutually in contact with the sea water. − Rust is a particular corrosion problem for steel pipes exposed to contact with sea water. Pipe connections Welding Female Flange Male Other 5 Pipe fittings − Elbows are used to change the direction of the pipe. Available in various angles (e.g., 90°, 45°) and materials matching the pipe. − Tees are used to branch off from the main pipe. Allows for the creation of secondary lines. − Reducers are used to connect pipes of different diameters, facilitating a smooth transition between sizes. − Flanges provide a means for connecting pipes and other equipment. They are bolted together with gaskets to create a seal. − Valves control the flow of fluids through the system. Types include gate valves, ball valves, and check valves, each suited to different applications. Pipework flexibility − The pipework system must be sufficiently flexible to accommodate the movements of the components as they expand. − Metallic pipes expand and contract as the temperature changes. Use of spacer for expansion when pipework is installed Pipe Chair, Roller and Saddle − Roller supports (Figures above) are ideal methods for supporting pipes, at the same time allowing them to move in two directions. − For steel pipework, the rollers should be manufactured from ferrous material. − For copper pipework, they should be manufactured from non-ferrous material. − It is good practice for pipework supported on rollers to be fitted with a pipe saddle bolted to a support bracket at not more than distances of 6 meters to keep the pipework in alignment during any expansion and contraction. 6 − Where two pipes are to be supported one below the other, it is poor practice to carry the bottom pipe from the top pipe using a pipe clip. Expansion fittings − Provision must be made in pipe systems to accommodate changes in length due to change of temperature, and so prevent undue stress or distortion as pipes expand or contract. − expansion fitting is one method of accommodating expansion. − Expansion fittings are placed within a line, and are designed to accommodate the expansion, without the total length of the line changing. − They are commonly called expansion bellows, due to the bellows construction of the expansion sleeve. − Other expansion fittings can be made from the pipework itself. Sliding joint − is an expansion joint has an anchored sleeve with a stuffing box and gland in which an extension of the joining pipe can slide freely within imposed limits. Steam-line expansion arrangement − allows for change of length with a right angle bend arrangement or a loop. (a) (b) Stainless steel bellows expansion joints − are commonly used since they will absorb some movement or vibration in several planes, eliminate maintenance, reduce friction and heat losses. − maximum and minimum working temperatures must be considered when choosing a bellows piece, which must be so installed that it is neither overcompressed nor over-extended. 7 Expansion bellows − has the advantage that it requires no packing. Watertight bulkheads − Bulkhead piece for use when a pipe passes through a watertight bulkhead. − Pipes are carried through watertight bulkheads with the use of special fittings to avoid impairment of their integrity. − The large flange of the fitting, covers the necessary clearance in the bulkhead. Connection to pumps − Pipes are connected to pumps by flanges. − Flanges are a potential weak point in a piping system. Welded flanges are prone to accelerated corrosion in the weld metal or in the heat-affected zone. − Pipes in wet areas where corrosion is likely need to be examined at regular intervals. Pipe support spacing − Clips and supports are used to hold pipes in position and to prevent movement or vibration. − Pipes can fracture when there is insufficient support. − Failures often occur as a result of mechanical wear when the clip loosens, allowing the pipe to move. − Grip type Mechanical joints provide axial resistance and can be used with pipes under medium or high pressure. − Machined groove type Mechanical joints provide axial resistance and can be used with pipes under medium or high pressure. − Slip type Mechanical joints − No axial resistance. These joints can only be used with pipes under low or medium pressure. The seal is achieved by packing. − Swage type Mechanical joints are pre-assembled and cannot be dismantled. They can be used with pipes under medium to high pressure. − Press type Mechanical joints are pre-assembled and cannot be dismantled. They can be used with low to medium pressure pipes. There is an internal seal which achieves joint tightness. − Byte type/compression Mechanical joints which can be used in high-pressure pipes. − Flared type Mechanical joints can be used in high-pressure pipes. A flared joint is generally used in the connection of copper pipes on refrigeration systems. 8 Pipe fittings Elbows 90 Welded Elbow 45 Long-Type Welded Elbow 90 Welded Elbow-Straight end 45 Welded Elbow Threaded Elbow Tees Equal Welded Tee Equal Welded Tee Y type Tee U type Tee Equal Union Cross Clamp Cross Welded Clamp Reducers Reduce Clamped reducer Eccentric Reducer 9 Sanitary reducer Concentric Reducer Clamps Clamp High Pressure Clamp Three-piece clamp Heavy Duty clamp Pipe Hangers Pipe hanger Pipe clip Hexagon Pipe Support Unions Stainless steel blind nut/ cap Sanitary Union, Ferrule Stainless Steel Union SMS union Sanitary Union 10 Stainless Steel Male Stainless Steel Round Nut Stainless Steel Male Bilge piping system The bilge system is used to remove small quantities of fluid that have leaked or condensed into a dry space. The diameter of the bilge main is: d = 25+1.68√L(B+D) d = internal diameter of bilge main, in millimetres L = length between the ship’s perpendiculars, in metres B = extreme breadth, in metres D = moulded depth, in metres In a tanker with a separate cargo pumping and piping system, the ‘enclosed space’ is the engine room and the diameter of the bilge main is: d = 35+3√Lo (B+D) Lo = length of the engine room, in metres. Ballast system piping − Ballast is taken on to increase a ship’s draught, particularly the stern draught, when sailing without cargo. − On a tanker, the entire ballast system is located within the cargo area and is operated from a pump room. − Ballast piping is usually made of ordinary mild steel. − A ship’s size determines the capacity of its ballast system. Fire mains system piping − Piping is used extensively throughout a ship for fire control purposes. The specific features of ships’ fire-fighting equipment are governed by the Safety of Life at Sea Convention (SOLAS). Fire mains system piping − Mild steel piping fitted with hydrants for hoses where saltwater is used for manual firefighting. − The fire main is designed for a typical working pressure of about 10 bar. − Pipes in the fire main are affected by corrosion both externally and internally. − Pipes are joined with flanged connections. 11 Sprinkler system piping − Small-bore pipes kept permanently charged with freshwater at about 10 bar pressure. − A sprinkler system is arranged to release automatically at temperatures of about 70°C, so the system can both detect and extinguish a fire. − The system uses saltwater after the fresh. − After use, it is flushed with freshwater to minimise corrosion. Inert gas (IG) system piping − Fitted on all tankers over 20,000 dwt and on all tankers fitted with crude oil washing (COW) systems. − IG piping is usually large diameter low-pressure mild steel, with smaller diameter branch lines. − The internal surface of inert gas piping does not usually corrode. − The external surface is painted but will corrode if the paint coating deteriorates. CO2 system piping − Relatively small bore hot galvanised mild steel piping designed to withstand the surge loads that occur with the release of CO2. − Main CO2 lines are designed to withstand the same pressure as that of CO2 bottles, while distribution lines off the main valve are designed for a lower pressure. − Typically, the main line is pressure tested to 200 bar, the design pressure being at least 160 bar. Foam system piping − Uses foam with an expansion ratio of 900 to 1 in mild steel low-pressure piping. − Pressure in the lines ranges from 4 to 5 bar. − Foam compound in storage tanks is pumped to a foam generator. − The system is required to deliver foam at a rate of one metre of compartment depth per minute. − Uses foam with an expansion ratio of 12 to 1 in mild steel low-pressure piping. − Typical pressure in low expansion foam piping is 12 bar. Dry powder system piping − Used mainly for the fixed fire-extinguishing system on the deck of gas carriers and on older chemical tankers. − Dry powder is held in tanks and is propelled by nitrogen gas stored in pressure bottles. − Dry powder delivery pipes are pressurised to 18 bar. 12 Engine cooling system piping − The main engine is cooled by two separate but linked systems: An open system (sea-to-sea) in which water is taken from and returned to the sea (seawater cooling) A closed system where freshwater is circulated around an engine casing (freshwater cooling). − Freshwater is used to cool machinery directly, whereas seawater is used to cool freshwater passing through a heat exchanger. − Fluid in motion causes abrasive corrosion and erosion. − To reduce the effects of turbulent flows, seawater systems incorporate large diameter mild steel pipes, the ends of which open to the sea through sea chests where gate valves are fitted. − If a seawater cooling pipe bursts, both suction and discharge valves will have to be closed to prevent engine room flooding. − In order to make sure the valves operate correctly when you need them to, open and close them at regular, say monthly, intervals. − Seawater pipes are usually mild steel, but galvanised steel, copper or copper alloy are also used. − Freshwater cooling pipes are generally made of mild steel. Air and sounding pipes − Air pipes allow an enclosed space to breathe. − They prevent over-or under-pressure by letting air in or out of the space when liquid is pumped in or out, or when temperature changes cause air or fluids to expand or contract. − Cargo holds are ventilated by air pipes passing through the weather deck and these are fitted with self-closing watertight covers. − Sounding pipes are small-bore mild steel pipes used to measure the quantity of fluid in a tank or a hold bilge. − The pipe allows a tape or sounding rod to pass through to the bottom of a tank or hold. − Air and sounding pipes are normally constructed of mild steel. Cargo piping − Cargo piping in tankers is usually mild steel and is protected from rusting by external painting. − Flanged connections are allowed on oil tankers, as well as on chemical tankers at valve connections and for fitting portable spool pieces, which are removable short lengths of pipe used for segregation of piping. − Regular pressure testing of cargo pipes is essential to detect weak points before they fail. Hydraulic systems piping − Hydraulic pipes are high-pressure pipes. 13 − Hydraulics are used for: Manoeuvring the steering gear Actuating controllable pitch propellers and thrusters Control of watertight doors and valves Lifting appliances and deck equipment Opening stern, bow or side doors Moving mobile ramps for hatch covers Driving cargo and ballast pumps and for many other minor shipboard utilities. − It is a requirement that hydraulic systems for steering, pitch control and watertight doors have dedicated piping and pumps. − It is important to prevent the external corrosion of hydraulic piping located on deck. − Hydraulic pipes operate at very high pressure and corrosion-induced weakness frequently causes hydraulic pipes to burst. Fuel oil and flammable liquid piping − There are two principal types of pipes that carry fuel and they are categorised by the pressure the pipe is designed to withstand. − Low-pressure pipes are used to move fuel from a storage tank to; a service tank an injection pump − High-pressure pipes are used to deliver fuel from an injection pump to an engine combustion chamber. − Ships’ fuel is usually stored in; Double-bottom tanks Deep tanks Side bunker tanks Settling tanks Service tanks − Piping between a service tank and a fuel transfer or booster pump is rated as low pressure. However, between each pumping stage, pressure increases. − Pipes from fuel tanks can pass through ballast tanks and pipes serving ballast tanks can pass through fuel tanks. − Because of pollution risks, classification societies have stringent rules restricting the length of any oil pipe passing through a ballast tank (and vice versa); it must be short, have increased wall thickness and stronger flanges. The Safety of Life at Sea Convention (SOLAS) includes requirements for fire safety in engine rooms. − Double-skinned pipes must be used to deliver fuel to engine combustion chambers. These are made of low carbon steel alloys and operate at high pressure, between 600 and 900 bar. Double skins are necessary because pipe fracture will cause fuel to spray in a fine aerosol. Fuel will ignite on contact with a hot surface, such as a turbocharger casing or exhaust pipe. The second skin is to guard against direct spraying. The pipe is designed so that fuel will be contained in the space between the outer skin and the main pipe, and will drain into a collecting tank fitted with a high-level alarm. 14 − Low-pressure lubricating and fuel oil pipes passing close to a hot surface have to be secured against the possibility of oil spraying from a flange. To prevent this, the flange is usually taped. In addition, and whenever possible, the pipes are routed clear of hot surfaces. Similarly, to prevent leaking oil falling onto a hot surface, pipes should never be allowed to run above a hot surface. Cocks − Cocks and valves are designed to control or interrupt flow. − Controlling or interrupting the flow is done in cocks by rotating the plug, − Controlling or interrupting the flow in valves by lowering, raising or rotating a disc in relation to a seating surface or by controlling the movement of a ball. − Cocks and valves have bodies furnished with flanged or screwed ends for connection to the joining pipes. Cocks − A cock may be straight-through, right-angled or open-bottomed as required by its situation in a pipe system. − Coks plug may be tapered or parallel with tightness achieved by lapping in or by resilient packing material. − In machinery spaces, the short sounding pipes for fuel or lubricating oil tanks, must be fitted with cocks having parallel as opposed to tapered plugs. Bronze Stop Cock Brass Stop valve Brass Sill Cock Example of sleeve packed cock 15 Valves − Flexibility in the operation of a water-supply system requires the proper valves for the condition that is to be controlled. − Valves are used to; Stop Throttle Control the flow of water in a pipeline. − Valves are used for controlling the; Flow Pressure Direction of the fluid flow. − Valves must be accurate in the control of fluid flow and pressure and the sequence of operation. − Valves are controlled; Manually Electrically Pneumatically Mechanically By combinations of two or more of above methods 16 − Leakage between the valve element and the valve seat is reduced to a negligible quantity by precision-machined surfaces, resulting in carefully controlled clearances. − Factors that determine the method of control include the, purpose of the valve, design and purpose of the system, location of the valve within the system, availability of the source of power. Valve classification − Valves are classified according to their use: Flow control Pressure control Directional control Level control Proportioning flow Flow control valves − Although many different types of valves are used to control the flow of fluids, the basic valve types can be divided into two general groups: Stop valves Check (Non-return) valves Stop valves − Stop valves are used to shut off or, in some cases, partially shut off the flow of fluid. − Stop valves are controlled by the movement of the valve stem. − Stop valves can be divided into six categories: Stop Gate valves Stop Globe valves Stop Butterfly valves Stop Ball valves Stop Plug valves Stop Needle valves Stop Gate Valves − The gate valves are used in systems where a straight flow with the least amount of restriction is needed. These valves are used in; Steam lines Waterlines Fuel oil lines Fire-main cutouts The gate valve should be left in one of two positions- completely open or closed. Gate valves are classified as either; Non-rising stem Stop Gate Valves 17  Rising stem Stop Gate Valves Non- rising stem Stop Gate valve Rising stem Stop Gate valve Stop Globe Valves − Globe valves are used as stop valves on the suction side of many fireroom pumps, as recirculating valves in the fuel oil system and as throttle valves on most fireroom auxiliary machinery. − The globe valve is ideal for service that requires frequent valve settings (throttling). Globe valve inlet and outlet openings are arranged in several ways to satisfy different requirements of flow. 18 − Three common types of globe valve bodies are: Straight Stop Globe valves Angle Stop Globe valves Cross Stop Globe valves − Stop Globe valves are commonly used in; Steam lines Air lines Oil lines Water lines − Pneumatic Stop Globe valves are flow control valves that regulate the flow or pressure of a fluid. − Hydraulic Stop Globe Valves controls the flow rate of natural gas fuel to various stages of an industrial gas turbine combustion system. − Butterfly Stop Globe Valve is a type of flow control device, typically used to regulate a fluid flowing through a section of pipe. 19 − Butterfly valves consist of a; Body Resilient seat Butterfly type of disk Stem Packing Notched positioning plate Handle − Butterfly valves used in; Salt water systems Fresh water systems P-5 fuel systems Naval distillate fuel oil systems Diesel oil systems Lubricating oil systems Air ventilation systems Stop Ball valves − Stop valves use a ball to stop or start a flow of fluid. One-way Stop Ball Valves Plug Stop valves A plug valve is a rotational motion valve used to stop or start fluid flow. 20 Needle Stop valves A needle valve is a type of valve having a small orifice and a threaded, needle-like plunger. It has a relatively small orifice with a long, tapered, conical seat. A needle-shaped plunger, on the end of a screw, exactly fits this seat. It allows precise regulation of flow, although it is generally used for, and is capable of, only relatively small flow rates. Check (Non-return) valves − Check valves permit liquids to flow through a line in one direction only. − Check valves have two openings in the body, one for fluid to enter and the other for fluid to leave. − Check valves work automatically and do not have any valve handle or stem. Reasons using check valves − Protection of any item of equipment that can be affected by reverse flow, − To check the pressure surges associated with hydraulic forces, Types of Check Valves − Ball check valves − Diaphragm check valve − Swing check valve − Clapper check valve − Stop-check valves − Lift-check valve 21 − Double check valves − Disc check valves Ball check valve closed open Diaphragm Check valves − A diaphragm check valve uses a flexing rubber diaphragm positioned to create a normally-closed valve. − Pressure on the upstream side must be greater than the pressure on the downstream side by a certain amount, known as the pressure differential, for the check valve to open allowing flow. − Once positive pressure stops, the diaphragm automatically flexes back to its original closed position Swing Check valves − A swing check valve consists of a flap or disc of the same diameter as the pipe bore, which hangs down in the flow path. − With flow in the forwards direction, the pressure of the fluid forces the disc to hinge upwards, allowing flow through the valve. − Reverse flow will cause the disc to shut against the seat and stop the fluid going back down the pipe. − In the absence of flow, the weight of the flap is responsible for the closure of the valve. Stop Check valves − A stop-check valve is a check valve with override control to stop flow regardless of flow direction or pressure. 22  Combination of a lift check valve and a globe valve Lift Check valves − A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. − A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. − When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow. Disc Check valves − The disc check valve consists of four main components: the body, a disc, a spring a spring retainer. The disc moves in a plane at right angles to the flow of the fluid, resisted by the spring that is held in place by the retainer. The body is designed to act as an integral centring collar that facilitates installation. Pressure control valves − Pressure control valves are used for safe and efficient operation of fluid power systems, system components, and related equipment requires a means of controlling pressure. 23 Regulating (Unloading) Pressure control Valves − Pressure regulators, often referred to as unloading valves, and are used in fluid power systems to regulate pressure. − In pneumatic systems, the valve, commonly referred to as a pressure regulator, simply reduces pressure. − In hydraulic systems the pressure regulator is used to unload the pump and to maintain and regulate system pressure at the desired values. Reducing Pressure Control Valves − Pressure control, reducing valves are automatic valves used to provide a steady pressure lower than that of the supply pressure. − Pressure control, reducing valves can be set for any desired discharge pressure that is within the limits of the design. − Several types of reducing valves used in the water service system are normally; Direct acting pressure control, reducing valves Pilot-operated pressure control, reducing valves Spring loaded pressure control, reducing valves Single seated pressure control, reducing valves Variable pressure control, reducing valves Non-variable pressure control, reducing valves Pressure control - Relief valves − This type of valve discharges water from pipes or systems when the maximum desired pressure is exceeded. − They do not maintain flow or pressure at a given amount, but prevent pressure from rising above a specific level when the system is temporarily overloaded. Valve accessories − There are different types of valve accessories and the methods used to maintain them. Accessories that aid in the control of valves include; Gear boxes Valve boxes Floor stands Post indicators Valve actuators Valve position indicators show when the valves are open or closed. Steam traps is a special type of valve which prevents the passage of steam but allows condensate through. 24 Mechanical Steam traps have been installed with ball floats, figure left, or open floats figure right, for control of a needle valve to release condensate. Figure: Ball float type Figure: Open float type Thermostatic Steam traps use the expansion of an oil-filled element, a bimetallic strip or flexible bellows to actuate a valve. As the condensate temperature rises in the oil filled element type element A expands to close the valve D. Strainers − The term strainer is sometimes used specifically for a simple device made up with a single layer of coarse gauze, a very coarse wire mesh or a drilled or perforated plate. − The strainer in this sense is installed to hold large foreign objects which could cause damage or blockage. − Simple strainers consist of a box with a removable lid in which a flat perforated plate is inserted such that the fluid must pass through the perforations. Auto-clean Strainers Circular straining plates, separation washers and spider are shown in Figure below. Lubricating oil systems are fitted with a wide variety of strainers some of which can be cleaned in situ. The knife edge strainer, figure below, has a series of discs ganged to a shaft. Interspaced between the discs are a number of thin ringers. The solid particles are trapped on the edges of, and between, the discs. By rotating the disc shaft the particles are cleared by the fingers and fall to a sump, which is drained periodically. It is essential to operate these strainers regularly to prevent clogging when rotation may be difficult. Some have been fitted with electric motors for continuous operation. Filter is a device designed to prevent the passage of unwanted solids into or further along a system, but the implication is that the particles are very small and the filter cartridge or element has a more complex or elaborate make up. Wire mesh cartridge Filters are usually of the duplex type and have various types of element. Some cartridges can be removed for cleaning; others have renewable elements. Cartridges can 25 be of gauze layers with different mesh sizes others are made up with layers of mesh and felt, some use membrane type materials. Magnetic Filters provide extra protection for engines and gearboxes where iron or steel wear particles are likely to be present. 26