Page 127 - Handbook Of Multiphase Flow Assurance

Hydrate of natural gas 123

Health impacts
Health impact of each chemical considered for hydrate control is based on the toxicity of two
key components: active ingredients which control hydrate formation and the solvent used to
transport the active ingredient to the location of hydrate control. Health impact of a chemical
should be described in a Material Safety Data Sheet (MSDS) and such information must be
made available to the workers dealing with the chemical injection. Specialty Personal Protective
Equipment (PPE) must be made available to and used by the workers dealing with chemicals.
In one instance, an onshore field was in operation with hydrate control implemented by
methanol injection. An operator took some methanol to their garage for use as a vehicle anti-
freeze coolant. The garage got burglarized and the liquid in an unlabeled container got stolen
and mistakenly ingested which led to a fatality. The field then got converted to the use of a
kinetic hydrate inhibitor as a safer and more economic method for hydrate control. When
selecting the hydrate control strategy, eventualities in storage, delivery and staff awareness
must be also considered.

Effect of hydrates on corrosion
There are reports that hydrates may accelerate corrosion rate if formed at both the carbon
steel and stainless steel interfaces as illustrated in Figs. 5.16 and 5.17 (Makogon et al., 2000,
2002; Makogon and Makogon, 2004). It is hypothesized that one of the mechanisms is crevice
corrosion where hydrate forms a solid over the steel material, and the gap between the steel
wall and hydrate creates a crevice with a concentration difference leading to corrosion.
Stainless steel 316 exhibits corrosion during hydrate formation as shown in Fig. 5.18
(Makogon and Makogon, 2004).

FIG. 5.16 Carbon steel coupons immersed in the same water, without hydrate (left) and with hydrate (right)
formation (Makogon, personal communication, 1999).