CT546 Integral process seals and factory seals · PDF fileConduit wiring system ... through the conduit. NEC 501.17: Single Sealed/ dual Sealed devices contain ... Benefits of Integral

September 2014

Products Solutions Services

INTERNAL

Benefits of Integral Process Seals and Factory Seals

Reducing risks and costs of instrumentation electrical installation in hazardous areas

Slide 1 Craig McIntyre

September 2014INTERNAL

Topics covered

Some definitions of electrical system seals to start The “real situation” concerning process seals in practice Typical process seal practices used today Definition of ANSI/ISA 12.27.01 process seal standard/requirements The risk reduction and cost reduction available to engineers and

operations using certified integral process seal instrumentation




Some typical instrument related hazardous area seals

Conduit SealsA seal installed in a conduit to minimize the passage of gas or vapor at atmospheric pressure and to prevent the passage of flames from one portion of an electrical system to another. Conduit seals are not designed to eliminate the passage of gas or vapor under pressure.

Cable SealsA seal installed in a cable to minimize the passage of gas or vapor at atmospheric pressure and ,to prevent the passage of flames from one portion of an electrical system to another. Cable seals' are not designed to eliminate the passage of gas or vapor under pressure.




Some typical instrument related hazardous area seals

Process SealsPrimary Process Seal

A seal which isolates process fluids (gas or vapor) from an electrical system. One side of the seal is in contact with the process fluids under conditions of normal operation

Secondary Process Seal A seal which is installed between a device which incorporates a primary seal and conduit (s) or cable(s) systems. The design of the secondary seal must prevent process fluids from entering the conduit or cable systems in the event of failure of the primary seal




The “real situation” process seal practices in industry

• ”Experience has shown that conduit or cable seals do not provide the necessary protection to prevent the migration of process fluids under pressure through the wiring system. Despite this, the CEC and NEC “process seal” requirements have been largely ignored.”

• “As a result, availability of certified (listed) and marked products is limited and the NEC and CEC requirements are not being broadly applied”.

• “Mitigation of this hazard: Recognize product standard ANSI/ISA 12.27.01 for device certifications (listings), both single and dual sealed devices.” ”Device manufacturers need to get products certified (listed), as it is time consuming, costly and subject to quality concerns if secondary seals or engineered solutions are applied in the field.”

Source: ELECTRICAL PROCESS SEAL REQUIREMENTS IN NORTH AMERICAN ELECTRICAL CODES, IEEE Paper No. PCIC 2008-34 presented at the 2008 Petroleum and Chemical Industry Committee Technical Conference Cincinnati, OH September 23, 2008




Typical process seal practices used today

None Double block and bleed (1) Venting junction boxes/enclosures Mineral insulated (MI) cable (2)

Explosion proof

Seal#2

Explosion proof

Seal #1

Vent

Process

Wiring

(1)

(2)




ANSI/ISA 12.27.01-2011 Standard recognition/requirements Per current NEC* and CEC guidelines,

process connected equipment certified as conforming to ANSI/ISA 12.27.01 and marked either “Single Seal” or “Dual Seal” do not need added process seals.

Integral Process Seal• ANSI/ISA 12.27.01 requirements designed

and built within the instrument without externals

• Generally these are provided within the instrument certification and without cost adders

• Reduce requirements for electrical system field engineering


* as of NEC 2010



ANSI/ISA 12.27.01-2011 standard recognition/requirements Manufacturer/third party assessor has to conduct (or prove via modeling)

device meets rigorous fatigue cycling, leakage testing and burst pressure testing Process temperature range Maximum Working Pressure (MWP)

Process temperature range Maximum and Minimum extremes

Manufacturer has to supply Information necessary for the determination of chemical compatibility of process

wetted materials that form part of a primary seal

Instructions for installation and use of primary seal failure annunciation (if applicable)

Instructions necessary for proper maintenance of seals, vents, drains, and annunciators

Although it might seem counter intuitive, under ANSI/ISA 12.27.01-2011, testing for “Single seal” is more rigorous than “dual seal” testing




Example certified integral process seal label




Example certified integral process seal label




Some ANSI/ISA 12.27.01 “add-on” process seal practices

External certified ANSI/ISA 12.27.01 “add-on” devices might be added to conduit installations at additional cost when integral process seal instruments are not available or be considered when there are requirements that the integral process seal solution may not fit. Wiring/cable set feed-through (1) Housing assembly (2)


Secondary process seal housing assembly

Conduit wiring system

draw vent indication

hazardous area unclassified area

(1)

(2)



ANSI/ISA 12.27.01-2011 StandardHow to Annunciate or Not to Annunciate, That is the Question

Electrical Conduit

Annunciation




Factory sealing (XP Installation only)Listed factory sealed equipment does not require use of additional associated conduit seal fittings.




Sealing conceptsExternal conduit seal and external process seal

Control room orunclassified area

Conduit seal (flame proof)

Process seal (gas tight)

< 18 inches

Class I, Div. 1

vent, annunciation

NEC 501.15: Conduit Seals are provided in conduit or cable systems to minimize the passage of gases and

vapors and prevent the passage of flames from one portion of the electrical installation to another through

the conduit.

NEC 501.17: Process Seals are devices to prevent the migration of pressurized process fluids from the

designed containment into the external electrical system and the control room

Flammable or combustible product

pressurized process tank

NRTL certified




Sealing conceptsIntegral factory seal and external process seal

Control room or unclassified area


Process seal* (gas tight)

NEC 501.15: Factory Sealed devices contain only non-incendive components in the connection

chamber, which is flame proof sealed against incendive components. “conduit seal not required”

NEC 501.17: Process Seals are devices to prevent the migration of process fluids from the designed

containment into the external electrical system and the control room

< 18 inches

NRTL certified including

FACTORY SEALED

vent, annunciation(*frequent practice: installation with vented junction box)

Class I, Div. 1






Sealing conceptsExternal conduit seal and Integral process seal

Control room orunclassified area


Process seal (gas tight)

< 18 inches


Integral SINGLE or DUAL SEAL (per ANSI/ISA 12.27.01)

vent, annunciation

NEC 501.15: Conduit Seals are provided in conduit or cable systems to minimize the passage of gases

and vapors and prevent the passage of flames from one portion of the electrical installation to another

through the conduit.

NEC 501.17: Single Sealed/ dual Sealed devices contain integral seals per ANSI/ISA 12.27.01 and do not

require a secondary process seal in the conduit

Class I, Div. 1






Sealing conceptsIntegral factory seal and Integral process seal

Control room or unclassified area


Integral SINGLE SEAL or DUAL SEAL (per ANSI/ISA 12.27.01)

and FACTORY SEAL

NEC 501.15: Factory Sealed devices contain only non-incendive components in the connection

chamber, which is flame proof sealed against incendive components. “conduit seal not required”

NEC 501.17: Single/dual integral sealed devices containing integral process seals per ANSI/ISA

12.27.01 do not require a secondary process seal in the conduit

Class I, Div. 1






Benefit by using certified integral process seals: Safer installation, flexible wiring and repair, lower installation cost• Flame proof conduit seal

• Installation ½ hour (fiber filler, mounting..) $30

• Conduit seal package $50

• Junction box $20

• Fittings $10

• Secondary process seal with annunciation• Installation ½ hour $30

• Secondary process seal package $140

• Fittings $10

• Junction box $20


Use of a factory sealed device may save $110

Use of a single/dual sealed device may save $200 Use of a single/dual sealed and factory sealed device may save $310



Endress+Hauser - Safety by Design


http://www.us.endress.com/process-safety


Documents

CT546 Integral process seals and factory seals · PDF fileConduit wiring system ... through the conduit. NEC 501.17: Single Sealed/ dual Sealed devices contain ... Benefits of Integral