Camera performs on-line vessel inspections

Thi Chang
Refining/Petrochemical Editor

Robotic Camera Systems (RCS), Calgary, has developed a camera that can enter on-line pressure vessels for inspection.

This camera can be inserted remotely, rotated, and articulated. Its video is recorded to broadcast NTSC (National Television Standards Committee) standards.

To date, RCS reports that two on-line inspections with two prototypes have been performed. One inspection was for Syncrude Canada Ltd.'s Fort McMurray, Alta., oil sands crude production facility and the other was for Imperial Oil Ltd.'s Sarnia, Ont., refinery. Both inspections saved millions of dollars by reducing downtime, the company says.

Features

The prototypes of the robotic camera are nicknamed the "pressure cam." The pressure cam, made of stainless steel or titanium, is about 1.25 in. in diameter, small enough to fit into most refinery pipes and vessels. It can enter pressures in excess of 1,000 psi and temperatures in excess of 1,000° F.

An integrated light fixture on the camera illuminates vessel internals. A picture of the camera is not shown because its patent is in the process of being approved.

The robotic camera system consists of the following elements:

A housing, camera, and cooling assembly
An insertion spool assembly to facilitate motorized insertion and rotation
A computer control unit with viewing and recording features
A viewing station.

Advantages and disadvantages

The robotic camera system moves in and out as well as up and down. It can pan 360° and articulate up to 320°.

Although operators can troubleshoot problems from pressure and temperature readings, the camera offers another tool for process improvements. It can enhance the data taken from pressure and temperature instruments with full-color video images during experimental runs. The operator can change variables and see a real-time picture of how the problem reacts.

To ensure that the camera provides good information, the equipment owner is given technical tools to provide accurate inspection interpretation. This training is necessary for consistent, high-quality inspections.

Because the pressure cam can broadcast to NTSC standards, its video quality is better than that of the pipe camera. The present standard is 525 lines of resolution and 30 frames per second.

Compared to the human eye, the robotic camera is more efficient and reliable. It does not require the vessel to be cooled down or shut down to observe the vessel internals. Because it simultaneously records what it sees, the camera does not rely on visual inspection to provide data. The video can be shared and objectively analyzed with other individuals.

When deciding to use the robotic camera system, users must consider a couple of caveats. If there is no entry to the vessel to be examined, the owner must install a hot tap. All precautions associated with hot taps must be considered.

In addition, the camera enters the vessel through a packing gland. Packing glands must be engineered properly, considering pressure, temperature, and personnel safety.

From the first two applications, RCS has developed detailed procedures for safety. These procedures address preparation of the site, insertion of the pressure cam, internally roaming within the vessel, and removal steps.

Applications

Syncrude's crude production facility in Fort McMurray makes 207,000 b/d of synthetic light crude oil. Syncrude is a ten-member consortium, of which Imperial Oil Resources Ltd. of Toronto, Energy Co. Ltd., Calgary, and Petro-Canada are the lead owners. Syncrude plans to spend about $6 billion over the next decade to expand oil-sands production.

In 1994, Syncrude used the pressure cam to troubleshoot a coker vessel that was overheating. According to RCS, the Syncrude vessel is the largest diameter vessel in the world, about 100 ft in diameter. The vessel contains a pressure of 32 psi and a flow rate of 150,000 cfm.

Fig. 1 [59,209 bytes] shows a diagram of the Syncrude vessel and the approximate areas that the two camera insertions reached. The coke transfer line in Syncrude's coker vessel directs the coke upwards to a chamber above the fluidized bed, where the burning takes place. Under the fluidized bed area, where the transfer line is located, the normal temperature is 450° F.

When Syncrude personnel realized that the vessel was overheated (about 750° F.), they decided to send the robotic camera to look at the transfer line. Although Syncrude did not know the problem at the time, a hole in one of the expansion joints on the transfer line was allowing heat to enter the space under the fluidized bed.

Initially, RCS extended the pressure cam about 80 ft through an existing 8-in. gate valve. According to the inventor of the robotic system, Russell Pahl, the first video picture was "like being trapped in a blizzard." The engineers determined that the flying particles were pieces of unburned coke. When the camera reached the area where the problem was located, a crack was found in the transfer line.

Although the camera showed a small crack on one side of the bellows, the engineers were able to evaluate it on the video screen and recognize that the problem was caused by something larger. To see the other side of the bellows, the pressure cam was inserted through an 8-in. hot tap in the coker vessel. From a few feet away, the camera identified a football-sized hole in the transfer line's bellows (Fig. 2 [6,107 bytes]). When the camera's light was turned off, an area 2-3 ft below the hole was cherry red, indicating a heat-affected area. In this way, the pressure cam found other locations that were in poor condition.

Had the camera not been available, the usual method to evaluate the cause of overheating would have been to send an inspector to internally view the problem. The unit would have been shut down and the vessel in question depressurized and cooled. Once the inspector determined the damage, he/she would document it, explain it to others, and together with others, formulate a repair plan.

The camera allowed inspection of the vessel and repair formulation to occur simultaneously with the unit operations. By the time the unit was shut down and cooled, the necessary replacement parts had been manufactured and were ready for installation.

At the time of inspection, Syncrude's on-line revenue was $4 million/day. Having avoided about 94 days of downtime, the pressure cam saved the company $376 million.

The second application of the pressure cam occurred at Imperial Oil's Sarnia refinery in 1995. Again, the camera was inserted into a coker vessel; Imperial's coker vessel is 30 ft in diameter.

The camera entered a 2-in. hot tap to detect a 2-in. hole in the structural skirt that supported the fluidized bed. Fig. 3 [7,739 bytes] shows a video capture of the hole the camera found. Like Syncrude, Imperial's alternative inspection would have required shutting down the unit and sending an inspector inside the vessel. Imperial saved over $40 million by reducing the downtime and knowing the extent of the damage before vessel entry.

Options

Based on feedback from the two commercial applications, Pahl has added several features to the camera. The camera now includes software analysis and reporting. A cross-licensing agreement with a software company allowed this upgrade. The new software standardizes the analysis of the video so that any insertion team can get the information required for analysis.

The software comprises three modules: an interface module to lead the operator through procedures, a size analysis module to provide failure data, and a reporting module to generate a written report.

The camera also has several additional safety features. A remote control system can control the camera insertion through the packing gland while the user operates it from a safe distance. In addition, a clamping mechanism can be used to clamp the camera and insertion rod to prevent loss of containment.

The following options are also available: an on-board temperature probe, a heat/color analysis module to provide quicker and more-accurate failure data, an on-board distance finder to assist the user in understanding the distances in the vessel, and a capability to link of vessel diagrams to video inspection to allow better navigation and interpretation of problems.