Precision-Engineered for Sample Integrity.
Welker constant pressure cylinders are engineered to preserve the true composition of your sample from collection to analysis. Our precision-engineered design minimizes adsorption and carryover, while select models are DOT-rated for compliant transport.
DOT Models Available: CP-2, CP-2HP, CP-4, CP-5, CP-24, CP-35
Why Constant Pressure Matters
Whether you’re sampling gas or light liquids/refined products, pressure changes can shift composition. Welker CP series constant pressure cylinders maintain a controlled internal pressure so vapor and liquid phases stay stable, helping ensure that what arrives at the lab reflects your process conditions in the field.
- Representative Samples: Helps protect light ends and prevents fractionation.
- Repeatable Handling: Consistent performance through transport and storage.
- Downstream Confidence: Supports custody transfer, allocation, and QA/QC reporting.
The Welker Difference
- Reduced adsorption & carryover to help maintain the sample’s true composition.
- Less wear against the polished surface
- Meticulous clean & inspection prior to shipment to support readiness for service
DOT Certification You Can Trust
Select Welker constant pressure cylinders are built and tested to meet applicable U.S. Department of Transportation requirements for safe, compliant transport. Each DOT-rated cylinder includes permanent identification, serial traceability, and testing to the relevant code.
DOT-Rated Models
CP-2 · CP-2HP · CP-4 · CP-5 · CP-24 · CP-35
Marking & Traceability
Permanent markings and serial numbers for inspection & records.
Testing & Documentation
Built and tested in accordance with applicable DOT requirements. Documentation available upon request.
Constant Pressure Cylinder Lineup
Browse our most popular models below. A Welker representative can help you select the right cylinder based on pressure class, process fluid, volume, and certification requirements.
CP-2 DOT
Compact constant pressure cylinder for general service and compliant transport.
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CP-2HP DOT
High-pressure variant of CP-2 for elevated operating ranges with DOT transport rating.
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CP-4 DOT
Workhorse cylinder for field and lab use where constant pressure control is critical.
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CP-5 DOT
Robust design for rugged service with DOT rating for over-the-road transport.
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CP-24 DOT
Larger capacity, DOT-rated cylinder for extended sampling and longer transport windows.
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CP-35 DOT
High-volume, DOT-rated cylinder for sizable composite samples and long hauls.
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CP-30
Constant pressure performance for plant or lab environments where DOT rating is not required.
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CP-77
Specialty cylinder for unique applications; consult Welker for configuration guidance.
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CP-78
Specialty cylinder for unique applications; consult Welker for configuration guidance.
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CP-30
Constant pressure performance for plant or lab environments where DOT rating is not required.
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LS-14
Constant pressure cylinder for light liquids/refined products.
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Quick Comparison
| Model | Standard Sizes | Material of Construction | MAOP | DOT |
| CP-2 | 150 cc, 300 cc, 500 cc, 800 cc, 1000 cc | 316/316L Stainless Steel, FKM, PTFE | 1800 psig @ -15 °F to 120 °F | Yes |
| CP-2HP | 150 cc, 300 cc, 500 cc, 800 cc, 1000 cc | 316 Stainless Steel, FKM, PTFE | 3600 psig @ -20 °F to 180 °F | Yes |
| CP-4 | 30 cc, 50 cc, 100 cc | 316/316L Stainless Steel, FKM, PTFE | 1800 psig @ -20 °F to 100 °F | Yes |
| CP-5 | 2000 cc - 6000cc | 316/316L Stainless Steel, Anodized Aluminum, FKM, PTFE | 2160 psig @ -20 °F to 100 °F | Yes |
| CP-24 | 500 cc, 800 cc, 1000 cc | 316 Stainless Steel, FKM, PTFE |
5000 psig @ -20 °F to 100 °F | Yes |
| CP-35 | 150 cc, 500 cc, 1000 cc | Anodized Aluminum, FKM, PTFE |
600 psig @ -20 °F to 100 °F | Yes |
| CP-30 | 6.6 Gallon | 316/316L Stainless Steel, Anodized Aluminum, FKM, PTFE | 300 psi @ -20 °F to 120 °F | No |
| CP-77 | 13 US Gallon @ 100% | 316/316L Stainless Steel, Anodized Aluminum, Delrin, Inconel, Molythane, FKM, PTFE | 450 psig @ -20 °F to 120 °F | No |
| CP-78 | ||||
| LS-14 | 3 Gallon @ 80%, 5 Gallon @ 80% | No |
Note: Model configurations, volumes, pressure ratings, and materials are application-specific. Your Welker representative will provide exact specifications.
CP Series: Options & Accessories
Valve & Connection Options
Quick-connects, needle valves, gauges, and fittings to match your sampling system.
Cleaning & Preparation
Cleaning, passivation, and packaging options to support analytical requirements.
Carrying Cases
Protect, organize, and transport your Welker cylinders with confidence.
Frequently Asked Questions
What is the Welker difference?
Our precision-engineering and attention to detail helps reduce adsorption and supports seal life—key to preserving a representative sample.
Which cylinders are DOT-rated?
CP-2, CP-2HP, CP-4, CP-5, CP-24, and CP-35 are available with DOT ratings for compliant transport. We provide markings and documentation to support inspection and records.
How do I choose the correct model?
Consider pressure class, required volume, media, transport needs (DOT or non-DOT), and connection preferences. Our team will recommend the optimal configuration for your service.
Do you provide custom cylinders?
Yes. From materials to connections and accessories, Welker can tailor cylinders for unique applications and regulatory needs.
Get a Constant Pressure Cylinder Quote
Tell us your process fluid, pressure, volume, and transport needs—we’ll configure the optimal Welker cylinder.