PPH Diaphragm Valve

PPH diaphragm valves (polypropylene homopolymer) are the value choice for strong alkaline service — high-concentration caustic soda, alkali carbonates, and salt solutions — to about 85 °C. Their toughness stands up to hot caustic and abrasion where other plastics struggle. We supply them in true union, flanged, and pneumatic configurations for chlor-alkali, alkali recovery, and neutralisation duties.

A diaphragm valve isolates the media behind a flexible diaphragm, so no stem packing contacts the fluid and there is no crevice to trap or contaminate it — a clean, low-maintenance choice for hot caustic and salt-laden lines.

PPH chemical compatibility

PPH is rated to about 85 °C and excels in strong alkaline and salt service.

Suitable: high-temperature strong alkalis (high-concentration sodium hydroxide / caustic soda); alkali-metal carbonates; inorganic salt solutions; non-oxidising dilute inorganic acids.

Not recommended: strong oxidising acids (concentrated nitric, fuming sulfuric); high concentrations of free chlorine and halogen gases; aromatic hydrocarbons.

As with all thermoplastics, the allowable pressure falls as temperature rises. For a specific medium and temperature, send us the details or see our chemical resistance reference.

Why our PPH diaphragm valves

• Best value for caustics. In strong alkaline media, PPH offers excellent molecular toughness and wear resistance, making it the cost-effective choice for hot caustic service.
• High toughness. Strong impact resistance and good resistance to thermal deformation and crack propagation under temperature swings.
• Double-diaphragm design, low compression set. The diaphragm assembly seals tightly and the body distributes closing pressure evenly, lowering closing torque and keeping flow regulation stable.
• No dead space, no packing wear. The diaphragm seals the media completely — nothing stagnates and nothing wears against the stem.
• Customisable. Bonnet, compressor, stem, bolts, and diaphragm can all be specified, including 304 or 316 stainless steel stems and fasteners. We use virgin branded resin and supply factory-direct.

Diaphragm material options

Diaphragm	Best suited to
EPDM + PTFE	Alkalis, alcohols, acetone, ambient water
FKM + PTFE	Oils, aromatics, strong acids, high temperature
EPDM + FEP (F46)	High-pressure gas, pure water, anti-permeation duty

Configurations

True union PPH diaphragm valve

Manually operated, DN15–DN50 (1/2″–2″), with union end connectors that let you lift the valve out for service without cutting pipe — ideal for dosing skids and tight installations.

Flanged PPH diaphragm valve

DN15–DN150 (1/2″–6″) to ANSI, DIN, or JIS flange standards. The bolted flange gives greater strength against pipe stress, vibration, and thermal movement, and is the standard choice for larger-bore and permanent caustic lines.

Pneumatic PPH diaphragm valve

DN15–DN150 with a corrosion-resistant all-plastic actuator in double-acting or spring-return (fail-safe) action. An adjustable closing-stroke stop protects the diaphragm, and the valve accepts solenoid valve, limit switch, positioner, and air filter regulator for automated caustic dosing and neutralisation lines.

Specifications

Body material	PPH / polypropylene (virgin branded resin)
Size range	DN15–DN150 (1/2″–6″); true union DN15–DN50
Pressure rating	PN10 (derates with temperature)
Max temperature	~85 °C
Body design	Weir type
Diaphragm	EPDM + PTFE / FKM + PTFE / EPDM + FEP
Connection	True union / flanged (ANSI / DIN / JIS)
Operation	Manual / pneumatic (double-acting or spring-return)
Stem & bolts	304 or 316 stainless steel option

Typical applications

PPH diaphragm valves are specified for hot alkaline duty: chlor-alkali plant caustic and brine circulation lines, high-temperature alkali recovery in dyeing and paper mills, and waste-alkali neutralisation in steel pickling. To weigh PPH against the other thermoplastics, see our plastic valve material selection guide.

Proven in the field: see how our integrated PPH valves replaced a failing field retrofit at a Vietnamese lithium plant.

Why buy PPH diaphragm valves from Huiya

Our PPH diaphragm valves are built for hot caustic and strong-alkaline service, supplied factory-direct — so you get the right configuration, competitive pricing, and a fast reply with no trading-company markup.

• ✅ Factory-direct — our own 2,000+ m² plant in Zhejiang, no middleman
• ✅ 100% virgin branded resin, fully traceable; produced at an ISO 9001-certified facility; material test reports on request
• ✅ Low MOQ — 20 pieces; samples available; OEM / custom welcome
• ✅ Fast lead time — about 7 days standard, 14 days custom
• ✅ 12-month warranty

Or explore our full range of PPH valves.

Frequently asked questions