Sampling Method GPA 2166

Prepared by :

Candra Aditya Wiguna 6512010005

Magda Dwi Apriani 6512010014

Agenda

Scope

Important Note

Definition

Principles of Sampling

Safety

Scope of GPA 2166

Purpose

To recommend procedures for obtaining representative samples from flowing natural gas stream

Not Included

Two-phase sample

Composite gas sample

Vacuum sources

Note of GPA 2166

Hydrogen Sulfide

Should be analyzed on site

Moisture

Should be analyzed on site or using moisture saturation calculation

Dew Point

Determine the dew point using chilled mirror test (the gas portion at two-phase system is at hydrocarbon dewpoint)

Temperature setting

Temperature of the line must 30F (17C) above the calculated hydrocarbon dewpoint

Note of GPA 2166

Equipment

All equipment between sample valve and sample cylinder must be maintained above hydrocarbon dewpoint

Sample conditioning downstream and sample purging must be maintained above hydrocarbon dewpoint

Regulator must be heated due to temperature decrease because of the JT process

Flow control must be located at the outlet of sample container

Flow control must be located at the end of an extension tube (pigtail) to thermally isolate the cooling effect caused by JT process

Definitions

Absorption

Natural gas constituents are dissolved into a liquid or solid that is not considered to be part of the mixtures liquid phase

Adsorption

A thin film of molecules adheres to aliquid or solid surface

Chilled mirror test

Used to determine dew points (water and/or hydrocarbon) by passing the natural gas over amirror while gradually reducing the temperature of the mirror until condensation forms in the surface of the mirror

De-sorption

Adsorbed or absorbed molecules are release from a liquid or solid surface

Definitions

Floating Piston Cylinder

A sample container which has moving piston that has sample pressure on one side of the piston, balanced by a pre-charge pressure on the other side of the piston

Flow-Proportional Composite Sampling

The process of collecting gas over a period of time at a rate that is proportional to the pipeline flow rate

Gas Sampling Separator

A device in the sampling system used to remove contaminant liquids from the natural gas sample

Multi Phase Flow

Two or more phase such as vapor and liquid in the sample stream

Representative Gas Sample

A gas sample that is compositionally identical, or as near to identical, as possible to the sample source stream

Sample Container

Any container used to hold a natural gas sample

Sample Probe

A device extending through the meter tube or piping into the stream to be sampled

Single-Phase Flow

For natural gas, natural gas flowing at the temperature above the Hydrocarbon Dew Point and free of compressor oil, water, or other liquid or solid contaminants in the flow stream

Principles of Sampling

Purging Fill and Empty Method

Purging Controlled Rate Method

Evacuated Container Method

Reduced Pressure Method

Helium Pop Method

Glycol or Water Displacement Method

Floating Piston Cylinder Method

Portable or On-Line Gas Chromatograph

Aparatus

Aparatus

Aparatus

Aparatus

Principles of Sampling Fill and Empty Purge Cycles

Method

Principles of Sampling

Maximum gas pressure in container, psig (kPa gauge)

Number of fill and empty cycles

15-29 (100-200) 13

30-59 (200-405) 8

60-89 (405-615) 6

90-149 (615-1025) 5

150-500 (1025-3450) 4

>500 (>3450) 3

Fill and Empty Purge Cycles Method

Number of Purge Cycles = log(X)Y X = atmospheric pressure + fill pressure (psia) Y = maximum allowable mole fraction of contaminants

Principles of Sampling

Purge Rate Controlling Method

Hig

her

Volu

me

Longer Purging

Reducing Pressure Method

Reducing pressure from high pressure line to sample line system

Sample not allowable to cross the two phase area

Helium Pop Method

He

5 psig Desired pressure

Water and Glycol Displacement Method

Water and Glycol Displacement Method

Water and Glycol can cause absorbtion and desorbtion

Use Glycol as displacement medium

When temperature

is below 32F (0C)

Use Water and Glycol as displacement medium

When temperature

is above 32F (0C)

Seals or Lubricant can absorb sample component

Seal or Lubricant must be inert

Floating Piston Cylinder Method

Open sample valve

Open purge valve

Close purge valve

Open sample inlet valve

Adjust pressure

Adjust pressure

Portable Gas Chromatography

Must using a regulator

Must heating the sample tubing and regulator

Use stainless steel and nylon 11 tubing

Separator in downstream sample conditioning must be heated and cleaned regulary

On-line Gas Chromatography

Must reduce pressure at or close to the sample probe to reduce

transfer sample lag time

Sampling system must be heated

Using bypass to get the current sample

Using membrane filter to protect GC from the

unwanted liquid

Portable and On-line GC Method

Handling

Sample container should be stored on shelves or racks

If sample container is known to have leaked, secure another sample. If another sample is unavailable, follow company procedure

Sample container should be heated to a minimum of 20OF (11oC) above sample source temperature. Sample Containers should be held at temperature for at least 2 hours prior to sample analysis

Safety

No. Activity Hazard Consequences Control

1 Sampling Natural Gas

Hydrocarbon vapors

Can cause fire Can cause

explosion

Technician should be trained properly

Dangerous component (H2S)

Can cause health hazards

Replacing breathing air

Technician should be trained properly

Auto-ignition and air mixture

Explosion Dont open valve rapidly

High Pressure Can injure the technician

Technician should be trained properly

2 Transportation Pressure Can cause leakage of the sample

Containers should meet appropriate pressure and pressure relief requirements

Those who transport or ship sample containers must be trained

Safety Hazard Preventive Hydrocarbon vapors are flammable and can be explosive

Technician should be trained properly in the safe handling of natural gas

Natural gas samples may contain component that cause health hazards (H2S) or replacing breathing air

Heating in laboratory analysis Ensure that any heating device meets the requirements

Transportation Containers should meet appropriate pressure and pressure relief requirements. Those who transport or ship sample containers must be trained in the current regulations.

Auto-ignition of natural gas and air mixtures in gaas sample cylinders

Dont open valves rapidly

High pressures Technician must be properly trained to work with compressed gasses. Sampling equipment shoul be rated equal to or higher than the highest expected pressure.pressure reduction from pipeline must be carried out with appropriately designed pressure regulators. Pressure relief devices should be used to protect from over pressure conditions

No. Activity Hazard Consequences Control

3 Analysis Heat Injured the analyst

Ensure that any heating device meets the requirements