TSP Name: Northwest Pipeline LLC TSP: 67977322
Critical: N
Notice Stat Desc: INITIATE
Notice Type Desc: OTHER
Post D/T: 07/09/2019 2:07 PM MCT
Notice Eff D/T: 07/09/2019 2:07 PM MCT
Notice End D/T:
Reqrd Rsp Desc: No response required
Rsp D/T:
Notice ID: 19-126
Prior Notice:
Subject: Dithiazine update
Notice Text:
Dithiazine Update Notice
Pursuant to the Dithiazine Notice published by Gas Transmission Northwest (GTN) on June 10, 2019 and
as a follow-up to Northwest Pipeline's (Northwest) April 11, 2019 Shipper Advisory Board Meeting,
Northwest provides the following update regarding the presence of dithiazine on its system.
Northwest previously communicated dithiazine was identified on the Spokane Lateral and within the
Columbia River Gorge at its Roosevelt compressor station. Subsequently, Northwest has preliminarily
identified dithiazine deposits on the Portland Lateral. Based on changing flow dynamics, Northwest now
anticipates potential discoveries south of the Stanfield interconnect in the mid-section of its system. As
communicated during the April 11th meeting, Northwest believes the dithiazine it has observed in these
areas is coming from producers upstream of the TransCanada system and is being transported
downstream through the GTN system.
Dithiazine is a reaction product resulting from the introduction of triazine based liquid chemical
scavengers used to remove hydrogen sulfide from gas streams. As stated by GTN in multiple shipper
notices, "Dithiazine may drop out of the gas stream, under certain conditions, in the form of a white
powder, and further chemically change to an adhesive, putty-like substance at some points of pressure
reduction (for example, at a regulator) due to a temperature drop that accompanies the pressure
reduction. If a sufficient quantity of the material is accumulated in certain appurtenances, it could cause
them not to function properly."
Northwest is undertaking a trial project attempting to capture dithiazine products using sub-micron
coalescing filters installed in fuel gas systems at a limited number of locations where dithiazine fallout
has already, or is expected to occur. This project is intended to determine the efficacy of the coalescing
filters with respect to dithiazine contaminant removal and evaluate potential applications at receipt
points.
Northwest anticipates communicating initial results of the trial filtration project by the end of the year.
In the meantime, Northwest encourages customers to maintain diligence in their own facility
maintenance to ensure safe and reliable operations and requests customers who suspect dithiazine
contamination to notify Northwest.
If you have any questions, please contact your Marketing Services
Representative or the Scheduling Hotline at (801) 584-7301
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