Pressure testing

What are the 2 types of pressure testing?

• Hydrostatic:

  • most popular by far- because water is virtually incompressible

    • If large volumes of pipe, you would need alot of air

    • Relieving air pressure would also take long

    • Lowers chance of explosive release of gas from pipe

    • Hydro test leaks are easier to find

  • Not limited to water, can be mixture

    • may need separate drain and fill connections to prevent environmental damage. Or spill pans.

  • Require vents at all high points and drains at all low points.

• Pneumatic:

  • some lines require no moisture or liquid at any time.

  • Or too costly to bring a water truck on site

  • Air normally has high moisture- air must be dried otherwise you may use nitrogen or CO2.

  • Always monitor leak test pressures as ambient temperature swings may increase test pressure beyond maximum allowable.

Pump vs Compressor

• pump- discharge fluid against pressure

• Compressor- also a pump but discharges gases against pressure

Pump styles/test gas supply used on pressure tests:

• Pump styles for pressure tests:

  • Pump driver

    • hand lever, moves a pneumatic diaphragm, smaller systems

  • Pneumatic diaphragm pump

    • operates direct ratio if input to output pressure. 100:1 can make 3000 psig with 30psi supply pressure

  • Motor driven pump

    • emits CO and CO2 so not typically used indoors or space needs to be ventilated

    • Local environment determines which motor type to use for the job

      • If electric motor: should check if the motor classification is TEXP (totally enclosed explosion proof)

        • Most plants require motor to be connected via GFI on the end of extension cord if the motor cannot be plugged into gfi outlet.

      • If air driven:

        • needs high air pressure. Larger hose. Lubricator installed in line.

        • Ensure all air connections are tight before powering.

  • Air compressor

    • uses a regulator (PRV)

    • Moisture in test air should be removed prior to PRV.

  • Gas cylinders

    • dry gas at very high pressure through a PRV

    • Hose connections are right hand.

      • only oxygen tanks have a CGA 540 thread.

      • Other gasses have a thread based on gas composition

• Pump styles for pressure tests:

  • Pump driver

    • hand lever, moves a pneumatic diaphragm, smaller systems

  • Pneumatic diaphragm pump

    • operates direct ratio if input to output pressure. 100:1 can make 3000 psig with 30psi supply pressure

  • Motor driven pump

    • emits CO and CO2 so not typically used indoors or space needs to be ventilated

    • Local environment determines which motor type to use for the job

      • If electric motor: should check if the motor classification is TEXP (totally enclosed explosion proof)

        • Most plants require motor to be connected via GFI on the end of extension cord if the motor cannot be plugged into gfi outlet.

      • If air driven:

        • needs high air pressure. Larger hose. Lubricator installed in line.

        • Ensure all air connections are tight before powering.

  • Air compressor

    • uses a regulator (PRV)

    • Moisture in test air should be removed prior to PRV.

  • Gas cylinders

    • dry gas at very high pressure through a PRV

    • Hose connections are right hand.

      • only oxygen tanks have a CGA 540 thread.

      • Other gasses have a thread based on gas composition

Older vs New high pressure hose coupling differences

• • Connected via universal couplings (chicago, crow coot, claw coupling)

    • Older versions needed saftey pin to prevent accidental twist in use

    • Newer hose may have self lock mechanism

Hose and Fittings:
How is it reinforced?

Which material is most common?

What are 2 common types of connectors for the hose?

Why might you need a larger fill line?

What should the pressure rating be for the hose?

What is a whipcheck?

• extreme high pressure hose is reinforced with metal or fibre mesh

• Carbon steel fittings are most commonly used unless fluid conditions require other material.

• Usually union or quick connects

• Most pressure hoses are small ID, so a larger diameter fill line sometimes needed to speed up fill time(usually tee that gets capped after)

• Pressure rating must be equal to or greater than your maximum pump output pressure.

• Whipcheck can be used to prevent hose from lashing

Gauges:

Most common type?

What happens to it if the dial face is larger?

Needs to be ______.

Most common type? Bourdon Tube

What happens to it if the dial face is larger? Increased Accuracy

Needs to be ______. Calibrated

List the standard for pressure testing gauges and what it means?

• PFI Standard ES-4 states:

  • pressure test gauge must be indicating pressure gauges and be connected directly to piping system if possible

  • Dial on gauge graduated double max test pressure, no less than 1.5 and no more than 4 times.

If vibrations are not excessively severe for a pressure gauge’s connection point what can you use? What if they are severe

• Vibrations:

  • if not severe use oil filled gauge

  • If severe, remote mount

  • Pulsation dampeners (snubber) can be used to prevent pulsation damage

Who determines which code to follow on site? Who is responsible for the QC?

• owner’s management or safety code officer determines which code to use in job

• Fabrication company’s QC responsible for performing testing and ensuring standards met

Common codes that contain pressure testing procedures

• Codes:

  • ASME B31: fabrication and install of pressure pipe.

  • CSA

  • AWWA

  • National Plumbing Code

  • B149 Gas Install Code

• Inspectors are responsible for ensuring testing is performed and equipment meets/exceeds minimum QC requirement.

• Always consult authority having jurisdiction over test requirement

Hydrostatic Test:

Is it safer than pneumatic, why or why not?

Why is it dangerous in the winter time?

What pressure and how much time to hold?

Is it safer than pneumatic, why or why not? Yes, the liquid is not as compressible and it depressurizes quick.

Why is it dangerous in the winter time? If using water, it can freeze causing immense pressures

What pressure and how much time to hold? 1.5X working pressure, 10 minutes as per B31.3

As Per ASME B31.3:

3 rules of the pressure test

4 info required to be written om pressure test report.

• Once components are assembled and fastened, pipe code requires a leak test. As per ASME B31.3:

  • before placing in operation, a leak test must be done

  • Test shall be hydrostatic and hold for 10 minutes

  • All joints/connections tested for leaks.

• ASME B31.3 requires this info:

  • Id of system, assembly being tested

  • Test date

  • Fluid used for hydro test

  • Certification of result by examiner

5 things to consider to conduct the pressure test safely

• Other things to consider:

  • flag off area when pressure testing

  • Ensure all air removed, it should take very little fluid to pressurize.

  • Pressurize to half pressure and verify for leaks first

  • Record ambient temperature and time when starting test. Ambient temperature swings will greatly change hydro test pressure

  • Increase in small increments to allow pipe stresses to normalize.

Pneumatic testing -

What are common testing gases?

Do you need a pressure relief? If so, what pressure?

How should you pressurize it?

What pressure should you use for the test?

What is needed if the volume is large? What is the value that triggers this?

• Pneumatic Test

  • air, nitrogen, argon is common

  • Other things to consider:

    • ensure a pressure relief is installed with no more than test pressure + 50 psig OR test pressure plus 10%. Whichever is leasT

    • Flag off area

    • Open valves slow

    • Pressure first to 25 psig or half the test pressure, whichever is less and perform preliminary test before going to full pressure

    • Test to 110% design pressure, when done, reduce to operating pressure. Record time and ambient temp and start pressure test.

  • Documents for pneumatic tests are the same as hydro, but:

    • If volume is large, a permit from authority having jurisdiction is required. Usually if greater than 0.5 m3 or 18ft3 OR >300 psig test pressure. Oo

    • A engineering calc is needed for total energy compressed. Document to be attached to test documents.

• Compressed gas is much more dangerous than pressurized liquids. Amount of energy can be calculated equivalent to ___

• Compressed gas is much more dangerous than pressurized liquids. Amount of energy can be calculated equivalent to TNT

  • 500ft of 1” pipe at 150psi can be 1.63 ounces of TNT. 2” =8oz TNT, 6”=5lbs TNT

Safety preparation notes (6)

• all openings sealed

• Isolation valve- fill and test piping isolation as close to assembly as possible.

• Provisions to vent air from system

• Support system adequate for test fluid and test assembly.

• If separate fill hose used, add extra fluid through test hose to ensure full before capping last vent.

• Watch pressure gauge during pump start up,

  • Sharp spike may be a valve is isolated somewhere

  • Slow to increase may indicate air is trapped, open vents and vent out air.

True or False - a whip check is used to connect hydraulic hoses?

False - it is used for pneumatic hoses

Why check pump electrical rating nameplate?

Ensure it is suitable for environment (explosive or not) and ensure voltage is correct for what you are about to supply it with.

Why should you increase test pressure in stages?

Allows pipe stresses to normalize

What is the main purpose of a hydrostatic test on a piping assembly?

Ensure the system can more than adequately carry design pressure

What components are used to make up a pressure test harness? (5)

• Union

• pump shutoff valve

• pressure bleed valve

• pressure gauge

• recorder connection outlet

What determines maximum output ratio of a pneumatic diaphragm pump?

The input air pressure to the pump

What enclosure rating is for a electric motor in a potentially explosive atmosphere?

TEXP