Design Philosophies for Building

Modern State-Of-The-Art Green Facilities

with Efficient Environmental &

Emissions Controls

Storage Tank Pressure Control and Minimizing Emissions

We now live in a Green World and that world includes onshore well sites!

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• Governments around the world are addressing the negative health effects of emissions – and the positive environmental benefits of reducing them

• As a result, emissions regulations have been substantially tightened

An undeniable shift has taken place in the world

• According to the EPA, storage tanks

account for a large percentage of VOC

emissions in oil & gas production

• The EPA’s “Quad O” regulation limits

the level of emissions allowed from

storage tanks

• Enforcement of tank emission

regulations at local levels in some

cases is more stringent

– Colorado DPHE Air Quality Control

Regulation 7

– Alberta Energy Regulator Directive 060

• “Assessment of Methane Emissions

from the U.S. Oil and Gas Supply

Chain” R. A Alvarez et al., Science (2018) claims

methane emissions are ~60% higher

than U.S. EPA estimates

Challenge: Regulatory enforcement has become high-tech and unforgiving

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Not adapting to this change will likely result in a negative future

Inspectors often use an

optical gas imaging

infrared camera (IR

camera) to detect leaks

from storage tanks.

Common compliance

issues include leaking

hatches and other

pressure relief devices.

Violations have resulted in

significant fines and even

facility shutdown.

Infrared (IR) cameras are

being used for

enforcement

• No identifiable

emissions from

hatch when not

venting

• Intrinsically safe IR

camera now

available that allows

inspectors to get

closer to devices

• Begin with an integrated design approach which takes into account the unique performance characteristics of each pressure control device

• Choose devices which offer sealing features

appropriate for the application

Tank Pressure Control considerations to minimize emissions

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DroopLock-up Tail

Blowdown Build-Up

• Perform regular maintenance in accordance

with manufacturers’ recommendations

• Consider remote monitoring to identify problems

immediately and improve labor efficiency

Tank Pressure Control Equipment

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Proper Selection, Sizing and Integration of Pressure Control Devices is Essential to Minimize Emissions

Vapor

RecoveryTank

Blanketing

Emergency

Venting

PVRV

Gauge Hatch

Detonation

ArrestorFlame

Arrestor

“Layers” of Tank Pressure Control

Tank Rupture

Tank Implosion

In-B

reath

ing

Ou

t-B

reath

ing

Vapor to Atmosphere

Atmospheric Air In-Breathing

Emergency Venting

Emergency In-Breathing

Blanketing Gas In-Breathing

Vapor Destruction / Vapor Recovery

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Spring Loaded Thief Hatch & Layers of Pressure Control

Tank Rupture

Emergency Venting

Vapor to Atmosphere

Vapor Destruction / Vapor Recovery

Blanketing Gas In-Breathing

Atmosphere In-Breathing

Emergency In-Breathing

Tank Implosion

In-B

reath

ing

Ou

t-B

reath

ing

Tank Rupture

Emergency Venting

“Breathable” Thief Hatch

The function of the thief hatch depends on the setpoints, it can be used as

primary, backup or supplemental pressure control.

“Breathable” Thief Hatch

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Example: Upstream Tank Battery “Vent to Atmosphere”

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OR

Device Setpoint

(Oz)

Setpoint

(inch H2O)

Hatch-VAC - 0.4 -0.69

PVRV-VAC - 0.4 -0.69

PVRV - Press 8 14

Hatch 12 20.7

ERV 16 27.7

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Without Vapor Control/Recovery, Inspection Results Do Not Distinguish Between Leakage and Venting

Upstream Tank Battery with Vapor Recovery

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Device Setpoint

(Oz)

Setpoint

(inch H2O)

Hatch-VAC - 0.4 -0.69

Blanket 2 3.5

VRU 3 - 8 5 - 14

PVRV - Press 12 20.7

ERV 16 27.7

OR

Blanket

Gas

Note: Using a single blanketing regulator for a multiple tank application

is generally not recommended due to pressure loss in piping.

FA ?

Integrated Tank Pressure Control Solution

Avoid Excessive Emissions and Product Loss

DroopLock-up Tail

Blowdown Build-Up Overpressure Emergency Pressure Vent

High Pressure Pressure Relief (Depad)

Low PressurePad

Underpressure Emergency Vacuum Vent

Tank Blanketing

System Control

Proper Integration of all Pressure Control Devices, Taking Into Account Unique Operating

Characteristics of Each, is Required to Provide an Optimal Solution

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Pressure Vacuum Relief Vent

Pressure Vacuum Relief Vent

Integrated Tank Pressure Control Solution

Avoid Excessive Emissions and Product Loss

Overpressure Emergency Pressure Vent

High Pressure Pressure Relief (Depad)

Low PressurePad

Underpressure Emergency Vacuum Vent

Tank Blanketing

System Control

Proper Integration of all Pressure Control Devices, Taking Into Account Unique Operating

Characteristics of Each, is Required to Provide an Optimal Solution

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Pressure Vacuum Relief Vent

Pressure Vacuum Relief Vent

No overlap on

settings but

insufficient

deadband

among themBlanket gas may be flowing while

the PVRV and emergency vent

may be venting.

Recommendation for Normal versus Emergency Venting Settings

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Max Out-breathing

Max In-breathing

Normal Breathing Region

Best Practice

<75% of ERV Setpoint

Best Practice

<75% of ERV Setpoint

Leakage vs. Venting – What’s the Difference?

• Venting – pressure and vacuum control to protect the tank

• Leakage – the escape of vapors when tank pressure is satisfied

FLIR Camera Inspection Does Not Distinguish Between Venting and Leakage

Hatch Closed:

No detectable emissions

Hatch above Pressure Setpoint:

Center assembly opens to relieve

pressure

Hatch below Vacuum Setpoint:

Vacuum pallet opens to relieve

vacuum

Leakage Venting

No

Leaks

Expected

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Leakage Standards and Characteristics for Low Pressure Relief Devices

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API 2000 Allowable High-Performance

Size Flow (CFH) % of S.P Product Size Flow (CFH) % of S.P

≤ 6” 0.5 75%PVRV

Vent Valve≤ 6” 0.5 – 1.0 90%

8” to 16” 5.0 75%

Gauge Hatch 8” 0.1 90%

PVRV 8” – 12” 0.5 – 1.0 90%

EPRV>12” to

16”1.0 90%

> 16” 20.0 75% EPRV > 16” 1.0 90%

Sustained High Performance Requires Regular Maintenance

• Inspect monthly or

sooner if leakage is

observed

• Wipe clean metal sealing

surfaces & seal, and

replace pressure seals if

worn or cracked

• EPRV’s should not cycle

during normal conditions.

Cycling will result in

premature seal wear and

excessive emissions –

• Inspect monthly or

sooner if leakage is

observed

• Wipe clean metal sealing

surfaces

• Verify settings by

verifying proper no. and

size of weights

• Replace pressure seals if

worn or cracked

• Inspect weekly

• Wipe clean metal sealing

surfaces and seals

• Verify spring setting by

color-coding, and replace

when worn or corroded

• Replace pressure and

vacuum seals if worn or

cracked

• Most important factor is

proper selection and

installation

• Consider response time if

significant tank pressure

fluctuation is expected

• If sensing lines are used,

mount on top of tank if

possible

• If mounted at grade, low

point drains are required

for sensing lines

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Hatches Vent Valves Emergency Vents Blanketing

Consider Remote Monitoring of Pressure Relief Devices

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Identify Potential Pressure Management Problems Immediately

Reduce Cost by Deploying Maintenance Personnel Only When Needed

Remote Monitoring of Pressure Management

Device Status by Means of Integrated Sensors

with Options for Wired or Wireless Connections

Identify Potential Pressure Management Problems Immediately

Reduce Cost by Deploying Maintenance Personnel Only When Needed16

Case Study : Minimize emissions with improved sealing performance

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• Challenge: Hatch replacement needs:

– Access to the tank for gauging

– Pressure and vacuum normal venting

– Emergency Venting

– Connection to a single existing API 8” x 18” or API 8” x 22” oblong tank nozzle

– Best-in-class sealing to minimize emissions

• Solution:

– Custom adaptor providing two device connections

– Emerson Enardo ES-665 thief hatch

• Leakage rate of 0.1 SCFH @ 90% of setpoint

– Emerson Enardo 2000 Series emergency vent

• Leakage rate of 1.0 SCFH @ 90% of setpoint

Results Proven in Field Testing

2 x 1 Custom Adaptor

Emergency VentES-665 Hatch

Questions

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