Natural Gas Sampling

Constant Pressure
Cylinders

Precision-engineered to preserve the true composition of your sample from collection to analysis. Select models are DOT-rated for compliant transport.

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DOT Models: CP-2 · CP-2HP · CP-4 · CP-5 · CP-24 · CP-35

ISO 9001:2015Certified Manufacturing

DOT-Rated ModelsFor Compliant Transport

Made in Sugar Land, TXExperts Since 1954

Precision EngineeredReduced Adsorption & Carryover

Why It Matters

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.

The result: what arrives at the lab reflects your process conditions in the field—not the effects of handling or transport.

Representative SamplesHelps protect light ends and prevents fractionation during transport and storage.
Repeatable HandlingConsistent performance from field collection through laboratory delivery.
Downstream ConfidenceSupports custody transfer, allocation, and QA/QC reporting requirements.
DOT-Compliant TransportSelect models are rated for safe, regulatory-compliant over-the-road transport.

Our Advantage

The Welker Difference

Reduced Adsorption & Carryover

Our precision-engineered design minimizes adsorption to help maintain the sample's true composition from collection to analysis.

Extended Seal Life

Less wear against the polished cylinder surface means longer-lasting seals and more reliable performance over time.

Ready for Service

Every cylinder is meticulously cleaned and inspected prior to shipment, so it arrives ready to perform on day one.

Compliance

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 on every cylinder for inspection and records compliance.

Testing & Documentation

Built and tested in accordance with applicable DOT requirements. Documentation available upon request.

Transport-Ready

DOT-rated cylinders are designed for safe over-the-road transport from field to laboratory.

Product Lineup

Constant pressure cylinder designed for light liquids and refined products applications.

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Specifications

Quick Comparison

Model	Standard Sizes	Material of Construction	MAOP	DOT
CP-2	150, 300, 500, 800, 1000 cc	316/316L SS, FKM, PTFE	1800 psig @ -15°F to 120°F	YES
CP-2HP	150, 300, 500, 800, 1000 cc	316 SS, FKM, PTFE	3600 psig @ -20°F to 180°F	YES
CP-4	30, 50, 100 cc	316/316L SS, FKM, PTFE	1800 psig @ -20°F to 100°F	YES
CP-5	2000–6000 cc	316/316L SS, Anodized Aluminum, FKM, PTFE	2160 psig @ -20°F to 100°F	YES
CP-24	500, 800, 1000 cc	316 SS, FKM, PTFE	5000 psig @ -20°F to 100°F	YES
CP-35	150, 500, 1000 cc	Anodized Aluminum, FKM, PTFE	600 psig @ -20°F to 100°F	YES
CP-30	6.6 Gallon	316/316L SS, Anodized Aluminum, FKM, PTFE	300 psi @ -20°F to 120°F	NO
CP-77	13 US Gallon @ 100%	316/316L SS, Anodized Aluminum, Delrin, Inconel, Molythane, FKM, PTFE	450 psig @ -20°F to 120°F	NO
CP-78	—	—	—	NO
LS-14	3 Gal @ 80%, 5 Gal @ 80%	—	—	NO

Model configurations, volumes, pressure ratings, and materials are application-specific. Your Welker representative will provide exact specifications.

Customize Your Cylinder

CP Series: Options & Accessories

Valve & Connection Options

Quick-connects, needle valves, gauges, and fittings to match your sampling system configuration.

Cleaning & Preparation

Cleaning, passivation, and packaging options to support your analytical requirements and sampling protocols.

Carrying Cases

Protect, organize, and transport your Welker cylinders with confidence using purpose-built carrying cases.

Common Questions

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 from collection to laboratory analysis.

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, process media, transport needs (DOT or non-DOT), and connection preferences. Our team will recommend the optimal configuration for your service conditions.

Do you provide custom cylinders?

Yes. From materials to connections and accessories, Welker can tailor cylinders for unique applications and regulatory needs. Contact our team to discuss your requirements.

Constant Pressure
Cylinders

Why Constant Pressure Matters