Mechanical-seals manufacturer AESSEAL is supplying four seals, worth R500 000, to concessionaire for oil and gas exploration on the subsoil and continental shelf of Angola, Sonangol.

AESSEAL MD Rob Waites tells Engineering News that the company first started working with Sonangol a year ago and has installed some 20 high- specification API 682 units.

“Sonangol needed fast-reaction suppliers of API-682-specification seals and AESSEAL could meet the requirements through quick deliveries of high-specification seals,” he says.

Waites notes that the company also supplies a local oil refinery, where the company has a mechanical-seal transac- tional arrangement.

“The refinery has four seal suppliers and AESSEAL is one of them. The company maintains 34% of the plant’s pumps, which amounts to 1 358 pumps out of 4 582,” he explains.

Waites adds that the company is in the middle of a second rollover of a five-year contract, which will come up for renewal in two years.

“We bid for the job against a list of installed mechanical pumps by tag number. Whether AESSEAL repairs or replaces a particular seal, we try to give the best price for it,” he explains.

Further, Waites explains that it is in the company’s best interest to repair a seal if it can be repaired, rather than to replace it entirely, which, he adds, is the fundamental premise of the contract with the refinery.

“This company has a reward structure in place, whereby mechanical-seals companies receive a fiscal reward for extending the time between failures on pumps. We either repair or replace mechanical seals so that the time between seal failures is as long as possible,” he notes.

Legislation

Waites explains that, fundamentally, in the refinery sphere, mechanical seals have to comply with the API 682 Edition 3 regulatory standards.

“The majority of refineries generate their own regulations in addition to that specification, whereby they accept the fundamental protocol of API 682, but add extra criteria that they deem necessary,” he says.

“The seals supplied have to meet these specifications to ensure that the poisonous substances inside the refineries’ pumps are not released into the atmosphere,” Waites points out.

The regulations categorise dangerous liquids that could be fatal or carcinogenic, like benzene, hydrogen sulphide or heavy metals. These liquids cannot, under any circumstances, leak into the atmosphere, he explains.

“Petrochemicals refineries are beginning to replace single mechanical seals with double mechanical designs, owing to stricter safety legislation,” he notes.

The biggest driver of the mechanical- seals industry is the necessity for refine- ries to upgrade from existing seals to mechanical seals designed to prevent harmful gases or liquids from escaping into the atmosphere.

Waites notes that this is due to API 682 Edition 3 and refinery overlay specifica- tions, which require the fitting of double mechanical seals on pumps that transfer hazardous fluids that fall into any of five categories – fluids that are immediately lethal or toxic on exposure, fluids that will cause a chronic condition as a result of long-term exposure, flammable products, reactive products and any product of high monetary value.

He adds that many of the seals being used by process industries producing toxic substances do not meet the requirements of API-specific regulations and will eventually have to be replaced, in accordance with government legislation.

The standard also specifies that a double seal be used to improve reliability, says Waites.

South African refineries implementing seal replacement programmes may encounter difficulties, depending on the seals supplier, when upgrading earlier- edition API 610 pumps, he explains, as many suppliers do not have mechanical- seal housings large enough to accommodate the API 682 Category 2 seals.

“Therefore, it would be necessary to either modify the housings or replace them,” notes Waites.

Mechanical seals supplied by AESSEAL are more recently designed and fit the mechanical-seal housings of all API 610 pumps.

“AESSEAL is the only supplier of mechanical seals that provide the end-user with a viable alternative to the costly pump modification or replacement option,” claims Waites.

He adds that excessive expenditure is not necessary because the company’s Cartridge API mechanical seals range has been designed with specific consideration for new and old equipment.

Waites points out that the range is fully compliant with the specifications of API 682 and has the same qualified seal face technology for the API 610 Edition 5 and Edition 10 pumps, as well as all the pump variants of the range in between.

“All the older pumps at refineries across South Africa can be retrofitted as a result, saving millions of rands in unnecessary expenditure,” he concludes.