01 · DIAPHRAGMS
Rubber Diaphragms,
Moulded to Your Stroke and Pressure.
Flat, rolling and convoluted diaphragms for metering pumps, valves, regulators and sprayers — plain or fabric-reinforced, moulded to your drawing at our ISO 9001:2015 plant in Nashik. The diaphragm sits in the medium on every stroke, so we choose the compound from what you are pumping, not from a default.
- ISO 9001:2015
- 8 COMPOUNDS IN-HOUSE
- FABRIC-REINFORCED
When does a rubber diaphragm need fabric reinforcement?
Above roughly 3 bar, or wherever a stretching diaphragm would change the dose, the rubber alone cannot carry the pressure and fabric reinforcement takes over. Margo moulds flat, rolling and convoluted diaphragms from Ø20 to Ø400 mm effective diameter, at 40–80 Shore A, and picks the compound from the medium you pump, not from a default.
02 · TYPES
Four Shapes, Chosen by Stroke
The shape follows the stroke. A short stroke can run on a flat diaphragm; a long one needs the sidewall to roll or the convolution to unfold, or the rubber works in tension and tears at the clamp.
Flat diaphragm
A clamped disc, plain or with a moulded-in plate. Simplest to tool and the lowest cost per piece. Stroke is limited to roughly a tenth of the effective diameter before the rubber starts working in tension.
Typical useRegulators, pressure switches, low-stroke valve actuators
Rolling diaphragm
The sidewall rolls between the piston and the bore instead of stretching, so the effective area stays near constant through the stroke and the force curve is flat. Needs a controlled piston-to-bore gap, which we confirm against your housing drawing.
Typical useMetering and dosing pumps, long-stroke actuators, air cylinders
Convoluted diaphragm
One or more moulded convolutions unfold to give stroke without stretching the rubber. Takes more stroke than a flat diaphragm at the same diameter and tolerates a less precise housing than a rolling one.
Typical useDiaphragm pumps, sprayer heads, large actuators
Fabric-reinforced diaphragm
Nylon, polyester or aramid fabric bonded into the moulding. The fabric carries the pressure load and holds the effective area stable; the elastomer seals and takes the chemical duty. Any of the three shapes above can be reinforced.
Typical useAnything above roughly 3 bar, and any duty where stretch would change the dose
03 · SPECIFICATION
What We Need to Quote
| Input | Range | Why we ask |
|---|---|---|
| Effective diameter | Ø20 mm – Ø400 mm | Set by tooling, not by the compound. Larger is quotable against the part |
| Stroke | to drawing | Decides the shape — flat, rolling or convoluted |
| Working pressure | to drawing | Decides ply count and whether reinforcement is needed at all |
| Medium | named fluid | Decides the compound. This is the input most enquiries leave out |
| Service temperature | −60 to +250 °C across the eight compounds | Narrows the compound with the medium |
| Cycle rate | strokes/min | A dosing pump at 200 strokes a minute and a regulator that moves twice a day are different parts |
| Mounting | clamped rim · bead · bolt circle | The clamp is where diaphragms fail. Send the housing detail |
| Insert | steel · stainless · brass · none | If a plate or stem is moulded in, we need its material and finish |
| Hardness | 40 – 80 Shore A | Our output, not your input — recommended against the duty unless your drawing fixes it |
| Dimensional tolerance | ISO 3302-1 class M1 | Tolerance follows the section, as on every moulded part in this catalogue |
Send a drawing in PDF, DWG, DXF or STEP — or send the diaphragm you are replacing and tell us how it failed. A hardened, cracked diaphragm means heat; a swollen one that has lost its shape means the wrong compound for the medium; a split at the clamp line means the stroke or the housing, not the rubber.
04 · COMPOUND
Tell Us the Medium. The Compound Follows.
A diaphragm is submerged in the medium on every stroke, so the compound is not a preference — it is the part. EPDM is right for water, dosing chemicals and brake fluid, and it swells until the diaphragm loses its shape in oil, fuel or grease. Every compound we mix is available on every part. These are ranked for a diaphragm.
| If the medium is | Compound | Service temperature | Note |
|---|---|---|---|
| Water, coolant, steam, dosing chemicals, dilute acids and alkalis, brake fluid | EPDM | −40 to +140 °C | The default for water treatment and dosing. Never in oil, fuel or grease |
| Mineral oil, fuel, hydraulic fluid, grease | NBR | −30 to +120 °C | The default for oil duty and the lowest cost of the oil-capable compounds |
| Solvents, aggressive chemistry, hot hydrocarbons | FKM | −20 to +250 °C continuous to +200 °C | The escalation when NBR is out of range. Poor in the cold and it fails in steam and glycol brake fluid |
| Hot oil and oil mist above nitrile’s ceiling | AEM | −40 to +175 °C continuous to +160 °C | The middle answer between NBR and FKM, at well under FKM cost. Absent from almost every competitor’s menu |
| Refrigerants, moderate oil, outdoor and marine | Neoprene | −40 to +120 °C | General purpose with flame-retardant grades available |
| Large low-pressure diaphragms, high stroke, air or water | Natural rubber | −20 to +90 °C | The best flex-fatigue resistance of the eight. No oil contact |
| Abrasive slurry, low cost, water | SBR | −30 to +100 °C | Abrasion resistance at commodity cost. No oil contact |
| Clean, high-temperature, low-pressure duty | Silicone | −60 to +220 °C | Widest temperature range and the weakest diaphragm. Low tear strength and poor flex fatigue — specify it only where temperature genuinely forces it, and expect a shorter life |
Not sure which applies? Send the fluid, the temperature and the pressure and we will recommend the compound with the datasheet, before you commit to a drawing.
05 · CONSTRUCTION
What Carries the Pressure
Fabric reinforcement
Moulded-in inserts
Plain moulded
Tooling is cut in-house. A new diaphragm tool runs alongside the compound trial, so first samples come back in 48 to 72 hours from an approved drawing.
06 · QUALITY
Tested Before It Ships
| Property | Method | Where |
|---|---|---|
| Hardness | ASTM D2240 | In-house |
| Tensile and elongation | ASTM D412 | In-house |
| Compression set | ASTM D395 Method B | In-house |
| Tear strength | ASTM D624 | NABL partner laboratory |
| Fluid immersion / volume swell | ASTM D471 | NABL partner laboratory |
| Ozone resistance | ISO 1431-1 | NABL partner laboratory |
| Dimensional conformity | ISO 3302-1 class M1 | In-house |
| Pressure-cycle life | ISO 132 · ASTM D430 · ASTM D813 | not held |
Material test reports, dimensional inspection sheets and a certificate of conformance ship with every consignment. Batch records are retained per shipment and are available on request under NDA. Diaphragms are packed flat and unloaded, so the sealing bead is not set before installation.
ISO 9001:2015 · Certificate 09111526A
Integral Certification Ltd · Valid to 21 February 2027
Scope: rubber moulded components — quality management, not a product approval
IATF 16949 — upgrade in progress, certification targeted by end 2026
ISO 14001 and ISO 45001 — targeted 2027
FREQUENTLY ASKED QUESTIONS
Technical & commercial questions
What is the minimum order quantity for diaphragms?
We supply in bulk. The minimum run is 10,000 pieces per part number, per compound, or quoted against the part where geometry or tooling makes that unrealistic. Prototype and first-article lots sit outside the minimum.
How long will the diaphragm last?
We do not publish a cycle figure, because we do not own a fatigue rig and a number without a test behind it is worthless to you. What we will do is qualify against your duty: give us the stroke, the working pressure and the target cycle life, and we will propose a compound and construction, run samples, and have them tested at a named laboratory to ISO 132, ASTM D430 or ASTM D813 — with the report in your name.
Can you reverse-engineer a diaphragm from a failed sample?
Yes. Send the old diaphragm and tell us how it failed. We size from the housing and the stroke rather than from the worn part, and the failure tells us what to change — hardened and cracked means heat, swollen and distorted means the wrong compound for the medium, split at the clamp line means the stroke or the housing rather than the rubber.
Do you supply fabric-reinforced diaphragms?
Yes. Nylon, polyester and aramid are all bonded in-house during cure, with ply count and orientation specified against your pressure and stroke. Metal inserts — steel, stainless or brass — are moulded in the same way, so there is no adhesive joint to fail.
Are your diaphragms approved for drinking water or food contact?
No, and we will not imply otherwise. Potable-water approval is granted to a specific compound formulation held by the compound supplier, not to a polymer and not to us — the schemes are WRAS to BS 6920 in the UK, NSF/ANSI/CAN 61 in North America, AS/NZS 4020 in Australia and New Zealand, and KTW-BWGL with DVGW W270 in Germany. Tell us which scheme your market requires and we will confirm what we can supply against it. We hold no food-contact or pharmaceutical approvals.
What are your payment and delivery terms for international orders?
TT and LC accepted, discussed per order. Ex-works Nashik or FOB Nhava Sheva. Commercial invoice, packing list and certificate of origin are issued with every consignment. Production is three to four weeks from drawing approval, or two weeks on an express basis where we have confirmed capacity.
09 · ENQUIRIES
Request a Diaphragm Quotation
Send your drawing with the effective diameter, stroke and working pressure, or the diaphragm you are replacing with a note of how it failed. Tell us the medium and the cycle rate. Our engineering team responds within 48 hours with a compound recommendation, dimensional confirmation and a quotation.