281.491.2331 13839 West Bellfort Street Sugar Land, TX
281.491.2331 13839 West Bellfort Street Sugar Land, TX
ISO 9001:2015
U.S. Patents
90 + U.S. Patents
Since 1954
Get A Quote



Tried and True

Need a bypass sampler with a proven track record? Look no further than the Welker inLoop™ Crude Oil Sampler! On the market for nearly 30 years, the inLoop™ is a positive displacement pump designed for crude oil and light liquid sampling applications. Ideal for lines up to 1”, take quality sample grabs proportional to flow or time with the inLoop™ at the heart of your bypass sampling system.

Power Up

Double-Acting Piston Motor

The inLoop™ is a reciprocating positive displacement pump. The pumping power of the piston motor is enough to overcome the reliefs to push the full sample volume through to the container every time. High-viscosity products won’t get left behind—the pneumatic or hydraulic pressure on the piston generates enough force to sample thick oils. This double-acting pump samples faster than similar electric samplers, giving you a more representative composite sample.

inLoop Motor
Vanishing Act

Unique Collection Head

Capture set volumes of sample with the Vanishing Chamber™ collection cup. Each actuation of the sample pump voids the collection cup, fully displacing the sample into the connected sample container.

Different Strokes

Piston-Style Collection Head

Does your application involve extreme temperatures, high pressures, or chemical contaminants? The B-style collection head is up to the challenge! Even under such harsh conditions, this piston-style collection head fully displaces fixed volumes of sample into the connected sample container.

inLoop Collection Head
inLoop Relief
Point of No Return

Backflow Protection

A companion to the collection head, the inline relief protects sample representativeness during fluctuations in pipeline pressure. Acting as a check valve, the inline relief keeps your samples in the sample container. If pipeline pressure drops, rest assured sample won’t flow from your container back to the pipeline.

Make of it What You Will

Tailor to Your Needs

Low pressure or high? NPT or flanged? Collection cup or piston-style collection head? Customize the inLoop™ with our variety of standard options and meet your process requirements without losing sampler or sample quality.



inLoop Sample Pump
Materials of Construction316/316L Stainless Steel, Fluorotrel®, PTFE, Viton®
Pipeline Spool Connection
Size: : 1" or 1½"
Rating: 150, 300, 600, 900, or 1500 ANSI RF
Process Connection¼" FNPT
Sample Outlet Connection1/4" FNPT
Utility RequirementsHydraulic or Pneumatic Supply: 40–65 psig
Sample VolumeB-Style Collection Head: 0.5 cc, 1 cc, or 2 cc
Vanishing Chamber™ Collection Cup: 0.22 cc, 0.5 cc, 1 cc, or 1.5 cc
OperationPiston-Operated Motor
Process Connection and Operating Pressure150 ANSI Stainless Steel: 275 psig @ -20 °F to 100 °F
300 ANSI Stainless Steel: 720 psig @ -20 °F to 100 °F
600 ANSI Stainless Steel: 1440 psig @ -20 °F to 100 °F
900 ANSI Stainless Steel: 2160 psig @ -20 °F to 100 °F
1500 ANSI Stainless Steel: 3600 psig @ -20 °F to 100 °F
FNPT Process Connection: 3600 psig @ -20 °F to 100 °F