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Diaphragm valves regulate, throttle or completely shut off liquids, gases and slurries, with a flexible diaphragm keeping the line fluid away from every working part of the valve.
The diaphragm does two jobs at once: it is the closing element, and it seals the process fluid off from the bonnet, stem and actuator.
A flexible elastomer or polymer diaphragm separates the line fluid from the bonnet, stem and actuator. Corrosive chemicals can't attack the moving parts, and lubricant or dirt can't contaminate the fluid.
The diaphragm presses down onto a weir or the floor of the body for bubble-tight shut-off, with no packing gland to leak.
The valve moves in a straight line up and down, so operators can adjust flow finely. Viscous fluids and media carrying suspended solids pass through without clogging.
Invented in Johannesburg. PK Saunders invented the original diaphragm valve on the West Rand gold fields in 1928. Today millions of Saunders diaphragm valves are in service across mining and every process industry, and we supply both the weir and straight-through designs.
Both types use the same three-part design: bonnet, diaphragm and body. You can replace the diaphragm or fit an actuator without taking the body out of the pipeline.
DN8 to DN350, screwed and flanged
The diaphragm closes onto a raised weir in the body. Short travel means longer diaphragm life and finer control, and it closes 100% leak-tight on pressure and vacuum.
DN15 to DN350, screwed and flanged
A straight-through body with no weir. The smooth, non-turbulent bore gives minimum pressure drop, resists erosion from abrasive media, and can be rodded out for cleaning.
Use this as a first guide. If your duty is unusual, send us the operating conditions and we'll specify the valve for you.
| Weir Type A | Full Bore Type KB | |
|---|---|---|
| How it closes | Diaphragm closes onto a raised weir across the bore | Diaphragm closes onto the floor of a straight-through bore |
| Diaphragm travel | Short, for longer diaphragm life and finer control | Long, for an unobstructed full-bore flow path |
| Best suited to | Clean and corrosive liquids, gases and vacuum service; throttling | Slurries, abrasives, powders and viscous media; lines that need rodding out |
| Sizes | DN8 to DN350 (screwed DN8 to DN80, flanged DN15 to DN350) | DN15 to DN350 (screwed DN25 to DN50, flanged DN15 to DN350) |
| Max working pressure | 16 bar DN8 to DN150; 6 bar DN200; lower above DN200 | 10 bar DN15 to DN100; 6 bar DN125 to DN150; 3.5 bar DN200 to DN300; 1.5 bar DN350 |
| Body materials | Cast and SG iron, bronze, gunmetal, stainless steel | Cast and SG iron |
| Linings | Rubbers, PP, PTFE, ETFE, PFA, Halar™, glass, Rilsan™, FBE | Rubbers, glass, Halar™, FBE |
| Installation | Any position; self-draining at 15° in a horizontal line | Any position; at least six pipe diameters from a pump or bend |
| Face-to-face standard | BS 5156 | EN 558-1 Series 7 (ex BS 5156) |
With the right body lining and diaphragm grade, one valve design covers clean water, aggressive chemicals and abrasive slurries.
Flow control and isolation on clean water, wastewater and effluent lines.
Abrasive slurries, tailings and process water. The full bore KB resists erosion and can be rodded out.
Acids, alkalis and corrosive liquids, handled with lined bodies and chemically resistant diaphragms.
Sterile, contamination-free processing, with grade 300 diaphragms suited to steam sterilisation.
Hygienic, easy-to-clean flow paths for products people will eat and drink.
Special diaphragms for fire-fighting, tank-cleaning and wash-deck services.
All dimensions are in millimetres and are for planning purposes only. Don't use them for manufacturing. Full details are in the datasheets.
| A, face to face (mm) | Nominal mass (kg) | |||||
|---|---|---|---|---|---|---|
| Size | Unlined | Lined | Coated | B max (mm) | Unlined | Lined |
| DN15 | 108 | 114 | 110 | 100 | 2.2 | – |
| DN20 | 117 | 123 | 119 | 100 | 2.5 | – |
| DN25 | 127 | 133 | 129 | 110 | 3.6 | – |
| DN32 | 146 | 152 | 148 | 150 | 4.5 | – |
| DN40 | 159 | 165 | 161 | 160 | 6.2 | 6.6 |
| DN50 | 190 | 196 | 192 | 180 | 9.4 | 10 |
| DN65 | 216 | 222 | 218 | 214 | 13 | 14 |
| DN80 | 254 | 260 | 256 | 220 | 20 | 22 |
| DN100 | 305 | 311 | 307 | 300 | 35 | 37 |
| DN125* | 356 | 361 | 358 | 375 | 50 | 53 |
| DN150 | 406 | 412 | 408 | 430 | 65 | 70 |
| DN200 | 521 | 527 | 523 | 507 | 145 | 156 |
| DN250 | 635 | 641 | 637 | 588 | 230 | 240 |
| DN300 | 749 | 755 | 751 | 683 | 360 | 366 |
| DN350 | 749 | 755 | 751 | 893 | 450 | 476 |
Maximum working pressures are for manual bonnets at ambient temperature and fall as temperature rises; the datasheet has the full temperature and pressure graph. A is face-to-face length to BS 5156; B is maximum height. Flanges to BS 4504. DN125 is a non-preferred size. DN200 to DN350 have a non-rising handwheel as standard.
| A, face to face (mm) | ||||
|---|---|---|---|---|
| Size | Cast, SG and malleable iron | Stainless, gunmetal and acid-resisting bronze | B max (mm), all materials | Nominal mass |
| DN8 | 48 | 48 | 59 | 140 g |
| DN10 | 48 | 48 | 68 | 410 g |
| DN15 | 64 | 64 | 91 | 570 g |
| DN20 | 83 | 83 | 94 | 890 g |
| DN25 | 108 | 95 | 115 | 1.4 kg |
| DN32 | 121 | 114 | 152 | 2.3 kg |
| DN40 | 140 | 133 | 164 | 3.3 kg |
| DN50 | 165 | 152 | 187 | 8.3 kg |
| DN65 | 203 | 191 | 224 | 9.4 kg |
| DN80 | 254 | 241 | 233 | 15.8 kg |
Threads to ISO R7. Masses under DN25 are in grams.
| Size | A open (mm) | B closed (mm) | C unlined (mm) | C rubber lined (mm) | E handwheel (mm) | Approx. weight (kg) | Max working pressure (bar) |
|---|---|---|---|---|---|---|---|
| DN15 | – | – | 108 | – | 80 | 2 | 10 |
| DN25 | 163 | 157 | 127 | 133 | 120 | 4 | 10 |
| DN32 | 163 | 157 | 146 | 152 | 120 | 5 | 10 |
| DN40 | 163 | 157 | 159 | 165 | 120 | 6 | 10 |
| DN50 | 185 | 165 | 190 | 196 | 120 | 11 | 10 |
| DN65 | 224 | 200 | 216 | 222 | 200 | 15 | 10 |
| DN80 | 273 | 240 | 254 | 260 | 250 | 23 | 10 |
| DN100 | 321 | 285 | 305 | 310 | 250 | 31 | 10 |
| DN125 | 347 | 305 | 356 | 362 | 315 | 46 | 6 |
| DN150 | 447 | 385 | 406 | 412 | 400 | 67 | 6 |
| DN200 | – | 415 | 521 | 527 | 400 | 110 | 3.5 |
| DN250 | – | 560 | 635 | 641 | 500 | 200 | 3.5 |
| DN300 | – | 640 | 749 | 755 | 630 | 300 | 3.5 |
| DN350 | – | 680 | 980 | 986 | 720 | 400 | 1.5 |
| Size | A open (mm) | B closed (mm) | C (mm) | Approx. weight (kg) | E handwheel (mm) | Max working pressure (bar) |
|---|---|---|---|---|---|---|
| DN25 | 166 | 159 | 111 | 2 | 120 | 10 |
| DN32 | 166 | 159 | 124 | 3 | 120 | 10 |
| DN40 | 166 | 159 | 143 | 4 | 120 | 10 |
| DN50 | 185 | 165 | 168 | 6 | 120 | 10 |
A is height with the valve open; B is height closed. C is face-to-face length to EN 558-1 Series 7 (ex BS 5156), unlined and rubber lined. E is handwheel diameter. DN200 to DN350 have a non-rising handwheel. Install the KB at least six pipe diameters from a pump or bend.
| Body or lining | Typical applications | Temp (°C) | Weir Type A | Full Bore KB |
|---|---|---|---|---|
| Cast iron, ductile (SG) iron | Strength and low cost on non-corrosive duties | −20 to 175 | DN15–DN350 | DN15–DN350 |
| Acid-resisting bronze, gunmetal, stainless steel | Long life in hostile, corrosive water; purity of service | −30 to 175 | DN20–DN150 | – |
| Soft rubber (SRL/AAL) | Abrasive duties | −10 to 85 | DN15–DN350 | DN25–DN350 |
| Hard rubber, ebonite (HRL) | Acids, chlorinated water, moist chlorine | −10 to 85 | DN15–DN350 | DN25–DN350 |
| Butyl rubber (BL) | Mineral acids and slurries | −10 to 110 | DN15–DN350 | DN25–DN350 |
| Neoprene (NL) | Abrasive duties where hydrocarbons are present | −10 to 105 | DN15–DN350 | DN25–DN350 |
| Polypropylene (PP) | Chemical and abrasion resistance in water treatment and effluent handling | −10 to 85 | DN20–DN150 | – |
| PTFE | High-temperature mineral acids; aromatic, aliphatic and chlorinated solvents | −10 to 175 | DN125–DN250 | – |
| ETFE | High abrasion resistance; strong acids and bases | −10 to 150 | DN20–DN150 | – |
| PFA | High-temperature strong acids | −20 to 175 | DN20–DN350 | – |
| Halar™ (ECTFE) | Mineral and oxidising acids, inorganic bases, salts | −10 to 150 | DN20–DN350 | DN25–DN350 |
| Borosilicate glass | Strong acids, halogens | −10 to 175 | DN20–DN200 | DN25–DN200 |
| Rilsan™ | Potable water | −20 to 80 | DN20–DN350 | – |
| Fusion-bonded epoxy (FBE) | Potable water | −20 to 80 | DN25–DN350 | DN25–DN350 |
Temperatures for lined bodies can also depend on the body material. Halar™ is a trademark of Ausimont UK Ltd; Rilsan™ is a trademark of ATO Chemical Products UK.
| Grade | Material | Typical applications | Type A (°C) | Type KB (°C) |
|---|---|---|---|---|
| Q (Type A) A (Type KB) | Natural rubber | Abrasives in slurry or dry powder form; water purification, brewing, inorganic salts, mineral acids | −50 to 100 | −40 to 90 |
| B | Butyl | Acids and alkalis, including up to 85% sulphuric acid at ambient; hydrochloric, hydrofluoric and phosphoric acids; caustic alkalis and many esters; sea water; inert and many industrial gases | −40 to 100 | −30 to 90 |
| C | Nitrile | Salts in water, dilute acids and alkalis, abrasives | −20 to 100 | −10 to 90 |
| 214/325 | PTFE faced, EPDM backed | Highest chemical resistance to all fluids except alkali metals; permeable to some, especially chlorine | −20 to 160 | – |
| 214/226 | PTFE faced, fluororubber backed | As 214/325, for higher temperatures; needs a slotted compressor | −5 to 175 | – |
| 226 | Fluororubber | Paraffinic and aromatic hydrocarbons; acids, especially concentrated sulphuric; chlorine. Not for ammonia and its derivatives or polar solvents such as acetone | −5 to 150 | −5 to 140 |
| 237 | Hypalon | Good acid and ozone resistance; certain chlorine services | −10 to 100 | 0 to 90 |
| 300 | Butyl | Hot water and steam sterilisation, so suited to brewing and pharmaceutical plants | −40 to 130 | −20 to 120 |
| 425 | EPDM | Salts in water, drinking water | – | −40 to 100 |
Temperature bands are a guide only; actual limits depend on the service conditions. On weir-type valves larger than DN80, diaphragms marked (V), such as Q(V), are reinforced for vacuum duty and have ferrous studs for all-iron-and-steel applications such as ammonia and acetylene. For continuous high-temperature and high-pressure duties, ask our technical team.
Tell us the line fluid, temperature, pressure and pipe size. Our team will recommend the body type, lining and diaphragm grade, and send you a quote.
