Northwest Pipeline LLC
NOTICE #29095
Dithiazine update posted on Jul  9 2019  2:07PM

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