Online pH/ORP Electrode Housing — Stainless Steel Coil Tube (Coiltube)
Product Overview
This coil tube (Coiltube) product is a precision-engineered stainless steel seamless tubing solution specifically designed for use as the protective housing (sheath) of online pH/ORP (Oxidation-Reduction Potential) electrodes in industrial process analysis systems. The coil tube is supplied in continuous coiled form, enabling flexible fabrication into electrode housings of varying lengths and geometries tailored to specific installation requirements. Designed for direct contact with aggressive acidic and alkaline process media, the product ensures chemical inertness, mechanical integrity, and minimal interference with electrochemical sensing performance — meeting the stringent response time requirements demanded by real-time process monitoring applications.
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coil tube is categorized under the instrumentation and process analysis segment of the industrial stainless steel pipe market, serving critical roles in water treatment, chemical processing, pharmaceutical manufacturing, and environmental monitoring systems.
Material & Properties
Available Grades
- ASTM A270 / UNS S31603 — 316L Stainless Steel: The standard-grade option offering excellent corrosion resistance in mildly to moderately aggressive acidic and alkaline environments. The low-carbon designation (≤ 0.03% C) minimizes intergranular corrosion susceptibility following welding operations, making it ideal for housings that undergo post-forming welding.
- UNS N06600 / N06625 — Hastelloy C-276 / C-22: A premium nickel-chromium-molybdenum alloy option for extreme environments including concentrated hydrochloric acid, hot sulfuric acid, and highly reducing alkaline solutions. Hastelloy provides superior pitting and crevice corrosion resistance (as measured by PREN ≥ 127 for C-276) compared to 316L.
Key Mechanical & Chemical Properties
| Property | 316L Stainless Steel | Hastelloy C-276 |
|---|---|---|
| Tensile Strength (UTS) | ≥ 515 MPa | ≥ 550 MPa |
| Yield Strength (0.2% offset) | ≥ 205 MPa | ≥ 275 MPa |
| Elongation at Break | ≥ 40% | ≥ 40% |
| PREN (Pitting Resistance Equivalent Number) | ~ 26 | ≥ 127 |
| Operating Temperature Range | −196 °C to +425 °C | −269 °C to +600 °C |
| Acid Resistance (HCl, 37%, 20 °C) | Limited | Excellent |
| Alkaline Resistance (NaOH, 50%, 100 °C) | Good | Excellent |
| Surface Finish (As-Supplied) | Bright Annealed / Pickled & Passivated | Bright Annealed / Pickled & Passivated |
Specifications
| Parameter | Specification |
|---|---|
| Product Form | Coil Tube (Continuous Coiled Seamless Tubing) |
| Outer Diameter (OD) Range | 3.0 mm – 25.0 mm (customizable) |
| Wall Thickness Range | 0.3 mm – 2.0 mm (customizable) |
| Coil Diameter | Standard: 300 mm / 500 mm; Custom upon request |
| Coil Length | Standard: 50 m – 500 m per coil; custom lengths available |
| Manufacturing Standard | ASTM A269 / A270 (316L); ASTM B462 (Hastelloy) |
| Tubing Type | Seamless (Cold Drawn / Cold Formed) |
| Surface Treatment | Pickled & Passivated (P&P); optional electropolishing |
| End Condition | Plain end; optional bead-formed or chamfered ends for sealing |
| Sealing Structure Compatibility | Designed for O-ring groove, threaded (NPT/BSP), compression fitting, and welding-based seal configurations |
| Electrochemical Compatibility | Non-magnetic (post cold-work may exhibit slight magnetic response); low electrical conductivity ensures no interference with pH/ORP electrode signal transmission |
| Response Time Impact | Optimized wall thickness and bore diameter to minimize diffusion delay, achieving electrode response time ≤ 30 seconds (per IUPAC guidelines for Class 1 pH electrodes) |
| Traceability | Full heat number traceability; each coil accompanied by Mill Test Certificate (MTC) |
Manufacturing Process
- Raw Material Selection & Incoming Inspection: Virgin billet or rod stock conforming to ASTM/UNS specifications is procured from certified mills. Incoming material undergoes spectrographic analysis (OES) to verify alloy chemistry within specified limits.
- Piercing & Hot Rolling: The solid billet is heated to forging temperature and pierced to produce a seamless hollow section, eliminating any weld seam that could serve as a corrosion initiation site — critical for electrode housing applications where surface integrity directly impacts sensor performance.
- Cold Drawing / Cold Forming: The hot-rolled tube is drawn through precision tungsten carbide (WC) dies to achieve the target outer diameter, wall thickness, and dimensional tolerances (typically ± 0.05 mm OD, ± 10% wall thickness). This cold working process also improves surface finish and mechanical strength.
- Intermediate Annealing: Where required for multi-draw reduction, controlled annealing cycles are performed to relieve cold-work hardening and restore ductility without compromising corrosion resistance.
- Pickling & Passivation: The drawn tube is subjected to a chemical cleaning process using a mixed acid solution (typically HNO₃/HF) to remove mill scale, oxidation, and surface contamination. Subsequent passivation forms a uniform chromium oxide (Cr₂O₃) passive film, enhancing corrosion resistance and ensuring electrochemical neutrality at the tube surface.
- Coiling: The processed tube is wound onto precision coils using controlled tension to avoid kinking, ovality, or surface damage. Coil dimensions are optimized for downstream processing by electrode manufacturers.
- Final Inspection & Testing: Each coil undergoes dimensional verification (caliper, bore gauge), surface finish inspection (visual + roughness measurement), hydraulic pressure testing (typically 2–5× working pressure), and optional intergranular corrosion testing (ASTM A262 Practice E) for 316L grades.
- Packaging & Dispatch: Coils are wrapped in protective plastic film, secured with steel strapping, and palletized for shipment. Mill Test Certificates (MTC) per EN 10204 3.1 are provided with each delivery.
Applications
Primary Application: Online pH/ORP Electrode Housing
The coil tube serves as the protective sheath enclosing the sensing element (glass bulb for pH; platinum reference electrodes for ORP) of online process analyzers. Key design considerations include:
- Chemical Compatibility: Direct immersion in process media ranging from pH 0 (strong acids) to pH 14 (strong caustics) without degradation of the housing material, ensuring long-term sensor accuracy and reducing maintenance intervals.
- Response Time Optimization: The seamless construction and precisely controlled bore diameter facilitate rapid diffusion of process analytes to the sensing element, meeting the ≤ 30-second response time requirement for Class 1 pH electrodes as defined by IUPAC and NIST guidelines.
- Sealing Structure Integration: The tube geometry is compatible with multiple sealing configurations — including threaded couplings (NPT 1/4", 1/2", 3/4"), compression fittings, O-ring sealed flanges, and soldered/welded assemblies — ensuring leak-tight integrity at the process connection interface.
Industries Served
- Water & Wastewater Treatment: Municipal drinking water disinfection monitoring, industrial effluent pH control, and ORP-based oxidation state measurement in biological treatment stages.
- Chemical & Petrochemical Processing: Reactor feed monitoring, acid concentration control, and process safety interlock systems requiring reliable pH/ORP measurement in aggressive media.
- Pharmaceutical Manufacturing: CIP (Clean-in-Place) verification, fermentation process control, and formulation pH monitoring in GMP-regulated environments.
- Food & Beverage Industry: Process water monitoring, CIP system verification, and product quality control in acidic (citrus, dairy) and alkaline (carbonated beverage) production lines.
- Power Generation: Boiler feedwater monitoring, condensate pH control, and cooling water treatment in thermal and nuclear power plants.
- Environmental Monitoring: River, lake, and groundwater quality monitoring systems requiring corrosion-resistant electrode housings for long-term deployment.
Unique Selling Points
- Seamless Construction: Eliminates weld-induced corrosion weaknesses, ensuring uniform chemical resistance throughout the housing length — a critical differentiator over welded alternatives in aggressive process environments.
- Dual-Grade Availability: Offers both economical 316L stainless steel and premium Hastelloy options, enabling customers to optimize cost-performance balance based on their specific process chemistry.
- Coil Supply Format: Continuous coiled delivery enables efficient downstream fabrication, minimizing material waste and reducing production lead times for electrode manufacturers.
- Electrode-Specific Design Optimization: Dimensional tolerances and wall thicknesses are engineered specifically for pH/ORP electrode applications, balancing mechanical strength with minimal diffusion delay for fast response times.
- Sealing-Ready Geometry: Tube ends and body are manufactured to accommodate industry-standard sealing interfaces without requiring additional machining, streamlining the electrode assembly process.
- Full Traceability: Every coil is traceable to its original heat number with complete chemical and mechanical test data, supporting regulatory compliance in pharmaceutical, food, and power generation sectors.
Quality Certifications & Compliance
| Standard / Certification | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ASTM A269 / A270 | Stainless Steel Seamless Tubing (316L) |
| ASTM B462 | Hastelloy Alloy Seamless Tubing |
| EN 10204 3.1 | Mill Test Certificate (MTC) — Product Certificate |
| ASTM A262 Practice E | Intergranular Corrosion Testing (316L) |
| ASTM E10 | Rockwell Hardness Testing |
| ASTM A999 | Hydrostatic Pressure Testing |
| ASME BPE (available upon request) | Bio-Pharmaceutical Equipment — Surface Quality & Cleanliness |
| REACH / RoHS | Environmental & Hazardous Substance Compliance |
Technical Note: For applications involving highly aggressive media (e.g., concentrated hydrochloric acid, hot sulfuric acid, or mixed-acid solutions), Hastelloy C-276 or C-22 grade is strongly recommended over 316L stainless steel. Customers are advised to consult with Wenzhou Jixing Metal Materials Co., Ltd. engineering team for material selection guidance based on specific process chemistry, temperature, and pressure conditions. Custom dimensions, surface finishes, and end configurations are available upon request to meet unique electrode housing design requirements.