Strainer Information Sheet

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Water Strainer DN25, 32, 40, 50, & 65 [1”, 1.25”, 1.5”, 2”, 2.5”]



Features Benefits

Bottom Inlet - 1

The inlet is positioned so that the incoming stream of water flows with minimal restriction into the interior of the basket.

The inlet position allows the strainer to be placed directly over the skin fitting / seacock. When the boat and engine are stopped accumulated debris can pass back into the waterway. This gives the strainer a ‘self

cleaning’ nature. The inlet may be threaded as BSP or NPT

Offset Outlet - 2

The rotational flow created by the offset outlet distributes the incoming water to a greater proportion of the basket thereby improving the flow rate

through the strainer. Two distinct flow paths are also created by the offset outlet. One path is reasonably direct from the inlet to the outlet. The other path is towards

the lid where its domed surface redirects flow down toward the outlet. In doing so the water passes through the strainer several times which stops

debris from consolidating on the strainer. This flow path also very effectively removes any air trapped or introduced into the top of the

strainer. The outlet may be threaded as BSP or NPT

Reversible Use The role of inlet and outlet may be easily exchanged to suit a different

installation. In this configuration the debris will be collected in the cavity on the outside of the strainer basket. Debris removal in this case requires

removal of the basket.

Machined Bands - 3 These bands are used to mount the strainer. A range of standard clamps

are available that can be used to mount the strainer to vertical or horizontal surfaces. Clamping allows the strainer to be freely oriented to

suit the associated piping system.

Bonding Screw - 4 The body is fitted with a screw for the purpose of connecting the strainer

to the same electric potential as other metals in contact with the seawater. This will provide protection from galvanic corrosion through the

use of a sacrificial anode.



Lid recess relief Two reliefs are present in the outer wall of the lid recess to allow the lid to be easily removed.

Basket

Strainer baskets have been sized to have similar fluid volumes on either side of the basket. This allows the inlet and outlet to swap function

without any penalty in the stored volume of debris. The baskets have been designed to provide a relatively large open area

when compared to the inlet area. Ratios range from 5 through to 10. The strainer comes standard with an ABS plastic basket. A 316 stainless

steel basket is available as an accessory. The ABS strainer basket has been coloured a bold yellow to make them

easy to locate if misplaced or dropped.

Gasket & Compression ring

A neoprene ring is fitted underneath the basket to eliminate rattle of the basket within the strainer body.

Another ring is fitted beneath the lid. This ring acts as a seal as well as restraining the basket.

The gasket & compression ring have been coloured a bold yellow to make them easy to locate if misplaced or dropped.

Knob with Stainless Steel Insert

The knob is constructed from ABS injected over a stainless steel insert. Should the strainer be subject to fire or elevated temperature there is no

risk of the lid coming off because the insert will remain in place. The knobs have been coloured a bold yellow to make them easy to locate

if misplaced or dropped.



Clear Lid A clear polycarbonate lid allows the interior of the strainer to be inspected without disassembly of the strainer. A stainless steel ring fitted around the

bolt circle prevents the damage to the lid from the knobs without restricting the view through the lid

Solid Lid (Optional)

The solid lid may be used in place of the polycarbonate lid. This lid is often used where the vessel is built to a survey standard.

Flange A stainless steel flange is used in conjunction with the polycarbonate lid to prevent the lid from being damaged by the retaining knobs.



Double Mount The double mount is used to fix the strainer to a vertical surface.

Single Mount (Horizontal)

This single mount is used to fix the strainer to a horizontal surface. Two single mounts may be used at different orientations or different styles

combined for difficult installations

Single Mount (Vertical)

This single mount is used to fix the strainer to a vertical surface. Two single mounts may be used at different orientations or different styles

combined for difficult installations



Water Strainer Flow Rates All throughout the design process Computational Fluid Dynamics (CFD) are used to fine tune the design of the Water Strainer. A lot of constraints always come into play with a design of this nature and CFD helps us to minimise losses and maintain high flow rates. One area where the ability to analyse the flow in such detail has helped us has been the development of the offset outlet. This configuration splits the flow into two distinct paths which greatly improves flow through the strainer and prevents the accumulation of debris on the strainer wall. The figure below is a trajectory plot of the water as it passes through the Strainer. Each line represents the path a particle of water would take and the colour indicates its velocity at that point. The two paths can be clearly seen. It can also be seen that the second path helps to deflect the first path towards the outlet which helps maintain such high flow rates. The second path also passes through the basket several times thereby keeping the debris agitated. The second flow path also very effectively scavenges air from the



Calculating Flow Rate The Water Strainer flow rates have been determined for a range of pressure drops using CFD analysis. The chart below gives the valve coefficient for each water strainer in the range. From this coefficient the expected flow rate or pressure differential can be calculated.

Valve Coefficient Strainer Cv Kv

DN25 [1”] Standard ABS 38.5 33.5 DN25 [1”] Standard SS 40.4 35.2 DN25 [1”] Compact ABS 16.8 14.6 DN32 [1.25”] Standard ABS 53.9 46.9 DN32 [1.25”] Standard SS 63.4 55.2 DN32 [1.25”] Compact ABS 28.5 24.8 DN40 [1.5”] Standard ABS 82.7 72.0 DN40 [1.5”] Standard SS 87.5 76.2 DN40 [1.5”] Compact ABS 32.7 28.5 DN50 [2”] Standard ABS 109.2 95.1 DN50 [2”] Standard SS 113.2 98.5 DN65 [2.5”] Standard ABS 146.8 127.9 DN65 [2.5”] Standard SS 150.3 130.8 DN80 [3”] Standard ABS 260.6 226.9 DN100 [4”] Standard ABS 368.1 320.5

SS - Stainless Steel basket,

ABS - ABS Plastic injected basket The Strainer is only one part of a complete piping system and consideration needs to be made of other components and the environment to determine the overall system performance.



Using the Valve Coefficient Cv The valve flow coefficient (Cv) is used as an indicator of the pressure drop across a valve under specific flow conditions and is defined as the number of US gallons per minute of room temperature water that will flow through a valve with a pressure drop of 1 psi across its inlet and outlet. The Cv is given by:

γP

QCv∆

=

where Q = Flow rate in US Gallons/minute P∆ = Pressure differential in psi γ = Specific Gravity of the fluid (1 for water, 1.025 for sea water) Knowing the Cv and the pressure differential, the flow rate Q can be calculated from:

γPCvQ ∆

=

Or knowing the Cv and the flow rate the pressure differential can be calculated from:

γ2

⎟⎠⎞

⎜⎝⎛=∆CvQP

Other methods should be used where the fluid has a high viscosity or it is non-Newtonian. The Cv values listed in the above table are the valve coefficients for particular strainer and basket combinations. Care should be taken to ensure the correct value is used.



Using the Valve Coefficient Kv The valve flow coefficient (Kv) is used as an indicator of the pressure drop across a valve under specific flow conditions and is defined as the number of cubic metres per hour of room temperature water that will flow through a valve with a pressure drop of 1 bar across its inlet and outlet. The Kv is given by:

γP

QKv∆

=

where Q = Flow rate in m ³/hour (1 m ³/hour = 16.67 litres/minute) P∆ = Pressure differential in bar (1bar = 101.325 kPa) γ = Specific Gravity of the fluid (1 for water, 1.025 for sea water) Knowing the Kv and the pressure differential, the flow rate Q can be calculated from:

γPKvQ ∆

=

Or knowing the Kv and the flow rate the pressure differential can be calculated from:

γ2

⎟⎠⎞

⎜⎝⎛=∆

KvQP

Other methods should be used where the fluid has a high viscosity or it is non-Newtonian. The Kv values listed in the above table are the valve coefficients for particular strainer and basket combinations. Care should be taken to ensure the correct value is used.



1" Series Water StrainerFlow Chart

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600

Pressure Differential (kPa)

Flow

Rat

e (m

³/hr)

DN25 [1"] ABSDN25 [1"] SSDN32 [1.25"] ABSDN32 [1.25"] SSDN40 [1.5"] ABSDN40 [1.5"] SS

1" Series Compact Water StrainerFlow Chart

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500 600


Flow

Rat

e (m

³/hr)

DN25 [1"]DN32 [1.25"]DN40 [1.5"]

Flow Charts

Metric Units




0

25

50

75

100

125

150

175

200

225

250

275

300

325

0 100 200 300 400 500 600


Flow

Rat

e (m

³/hr)

DN65 [2.5"] ABSDN65 [2.5"] SSDN50 [2"] ABSDN50 [2"] SS

DN 80 [3"], DN100 [4"] Water StrainerFlow Chart

0

100

200

300

400

500

600

700

800

0 100 200 300 400 500 600


Flow

Rat

e (m

³/hr)

DN80 [3''] ABS

DN100 [4"] ABS




0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60 70 80

Pressure Differential (psi)

Flow

Rat

e (U

S gp

m)

DN25 [1"] ABSDN25 [1"] SSDN32 [1.25"] ABSDN32 [1.25"] SSDN40 [1.5"] ABSDN40 [1.5"] SS

1" Series Compact Water StrainerFlow Chart (Imperial)

0

50

100

150

200

250

300

0 10 20 30 40 50 60 70 80


Flow

Rat

e (U

S gp

m)

DN25 [1"]DN32 [1.25"]DN40 [1.5"]

Imperial Units




0

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60 70 80


Flow

Rat

e (U

S gp

m)

DN65 [2.5"] ABSDN65 [2.5"] SSDN50 [2.0"] ABSDN50 [2.0"] SS

DN 80 [3"], DN100 [4"] Water StrainerFlow Chart

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40 50 60 70 80


Flow

Rat

e (U

S gp

m)

DN80 [3"] ABS

DN80 [4"] ABS



Typical Installations…

Strainer Information Sheet

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