An Alexandria consulting firm was indicted yesteday by a federal grand jury on charges that it illegally inflated pay vouchers by $23,000 on contracts with the Army, Air Force and Interior Department.

The 16-count indictment accused Kinton Inc., its president, Edgar L. Shriver, and his wife, Sarah, the company's treasurer, of submitting false claims during a 14-month period on contracts with a total value of about $147,000.

Kinton, a research firm with more than 100 employes, developed testing materials and brochures for the two services and Interior's Bureau of Mines, sources familiar with the investigation said.

"There is no truth to the allegations and they will be shown to be false in court," Edgar Shriver said yesterday. He declined further comment. f

Plato Cacheris, who is representing Shriver, called the indictment "a tempest in a teapot. We intend to fight it and we'll be in court Monday morning to plead not guilty." Cacheris said Kinton was audited regularly by the Defense Department during the period covered by the contracts.

Assistant U.S. Attorney Theodore Greenberg, who heads the prosecution, declined to comment on the charge.

If convicted, the Shrivers each face a maximum penalty of five years in prison on each count and a fine of up to $10,000 on each of the 16 alleged offenses. Kinton Inc. could face a maximum $10,000 fine on each count.

According to the indictment, the disputed contracts ran from Nov. 1, 1977, to Jan. 3, 1979, during which time the Shrivers submitted monthly invoices for payment for work on nine government contracts. The grand jury charged that the couple altered and falsified employe time sheets or ordered others to alter the sheets on which the invoices were based.

The result was a misrepresentation of the number of employe hours worked, the indictment said. The allegedly fraudulent vouchers ranged in total value from a minimum of $2,327.42 for work performed for the Army in September 1978 to $24,072.64, also billed to the Army, in July of the same year. Only a portion of each voucher is under dispute.

A source familiar with the grand jury probe said a single voucher for $9,618.29 submitted in December 1978 to the Bureau of Mines involved developing a training manual for miners.

In all, seven allegedly illegal vouchers worth a total of $76,149 were submitted to the Air Force during the period covered by the indictment. The Army also paid six disputed vouchers totaling about $61,000.

Cacheris yesterday characteized the company's services as "piecemeal consulting work" involving training and testing materials and developing brochures telling government agencies how to conduct their own testing. He said Kinton currently holds other government contracts, but said he was unable to furnish any details.