Coating Qualification, Process

The manufacturer applied liquid epoxy to lab panels, and an approved third-party lab performed the tests shown in table 5.

The liquid epoxy met all acceptance criteria shown in table 5 with the exception of the 2.5 flexibility requirements. Considering that field-joint coatings are not bent in the field, levels of flexibility lower than those expected for the shop-applied coating were acceptable. Formulation of the field-injected polyurethane foam was similar to the shop and spray-applied version except that there was less catalyst, slowing the cure process. The foam could be poured into the mold and flowed to the bottom before expanding to fill the cavity. Spray-applied foams are quicker reacting in order to prevent the foam running off the pipe. The field-injected insulation underwent qualification testing in the manufacturer’s lab according to the shop-applied foam qualification-test requirements.

The heat-shrink sleeves were assessed based on the following criteria:

• Ease of installation;

• Time of installation;

• Effects of preheat on shop-applied coating.

Visual assessment of sleeve (nothing adhesive flow at edges and lack of air entrapment).Peel testing at overlap to PE and to polyurethane foam (cohesive bond failures over the ^PE and adhesive bond failures over the foam, exceeding foam strength, were acceptable modes of failure). Acceptable modes of failure included a cohesive failure over the PE and the adhesive bond to foam exceeding foam strength The FBE was applied according to requirements of CSA Z245.20-98. Immediately before this application, the pipe surface vias abrasive blasted to SSPC-SP10/ NACE No. 2, near-white metal blast cleaning, treated with a phosphoric acid wash, rinsed, dried, and heated with a combination of induction coils and a propane-fired oven. Following FBE application, it was quenched and inspected for holidays (coating damage or defects), which were repaired with the approved field-joint liquid epoxy. The pipe was then temporarily stockpiled In the yard. Before application of the foam insulation and the outer jacket, the FBE was again holiday tested for any discontinuities.

Pipes with defects were set aside and repaired. Pipe free of holidays was cleaned of any foreign matter that would interrupt adhesion of the foam to the FBE. The pipe was preheated with an induction coil and the coating flame-oxidized to ensure adhesion of foam to FBE. Next, the polyurethane foam insulation was sprayed onto the pipe. As it cured, it was wrapped with PE tape, and finally PE was extruded over the PE tape. The bond between the PB tape and extruded PE was achieved by heat fusion. The pipe was quenched and the foam cutback area was holiday-inspected (2ndrepaired as necessary. Technicians performed several quality-assurance tests throughout production; table 6 describes the tests performed on each layer. The pipe was coated in two steps, first, the pipe was coated with FBE and stockpiled. Subsequently it was coated with insulation and an outer jacket.

The desire tc minimize the number of FBE repairs led to several precautionary measures in handling the pipe. Once the pipe was completely coated, pipe ends were covered with plastic bags to protect the exposed insulation from the elements and to maintain internal cleanliness of the pipe. A loader with wide, padded forks to avoid damage to the coating (crushing), then transported the pipe to the stockpile. Finally the pipe was stacked four tiers high on sawdust-filled bags. Trucks transported the pipe from the applicator's facility to the site. A crane loaded pipe onto truck trailers, stacking it no more than four tiers high and placing short joints on the top two tiers. During transport, the front end of each load was covered with a trap to ensure that the end bags survived the journey.

Questions:

1 Was the FBE applied according to requirements of CSDZ 245. 20-98?

2 What could be poured into the mold and flowed to the bottom to fill the cavity?

3 What were set aside and repaired?

4 What was the pipe preheated with?

5 Why were pipe ends covered with plastic bags?

15.1 What is the main idea of the article?