scope:

This specification covers environmentally hardened pressure gauges that utilize a mechanical elastic element to sense the pressure to provide an analog indication of the pressure on a circular dial or vertical scale, Helical Edgeview Mechanical Pressure, Indicator (HEMPI). Depending on case size and design, the pressure gauge may either be stem or flush/surface mounted.

Pressure gauges are classified according to the following variables (see 6.2):

(a) Design (see 1.2.1).

(b) Type of pressure (see 1.2.2).

(c) Dial size, case design (see 1.2.3).

(d) Elastic element material and style (see 1.2.4).

(e) Dial range and color (see 1.2.5).

(f) Pressure connection and connection location (see 1.2.6).

(g) Liquid fill case fluid and vibration category (see 1.2.7).

(h) Cleanliness (see 1.2.8).

Pressure gauge design is designated by one of the following symbols: Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Commander, Naval Sea Systems Command, SEA 55Z3, Department of the Navy, Washington, DC 20362-5101 by using the self-addressed Standardization Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter.

Pressure gauge design Symbol Simplex S Simplex - special applications. Caisson K Cruising range C Oxygen X Refrigerant R Duplex D

Type of pressure that the pressure gauge shall indicate is designated by one of the following symbols:

Type of pressure Symbol Gauge pressure G Vacuum V Compound C Suppressed, gauge pressure S Retarded, gauge pressure R Retarded, compound pressure T

The dial size and case design is designated by one of the following symbols:

Dial size Case design Symbol 2 Stem mounted 1 2-½ Stem mounted 2 3-½ Flush/surface mounted 3 4-½ Flush/surface mounted 4 8-½ Flush/surface mounted 8 1-¼ (vertical scale) Flush H

The elastic element is designated by two symbols as provided below. The first symbol designates the elastic element material. The second symbol designates the elastic element style.

Elastic element material Symbol K-monel M Inconel I K-monel or Inconel N (manufacturer option) Elastic element style Symbol C-type bourdon tube (gear drive) C Helical (also helical-spiral) H bourdon tube (gear drive) Helical (also helical-spiral) D bourdon tube (direct drive) C-type, helical (gear drive), N or helical (direct drive)-manufacturer option

The range and color of the pressure gauge dial is designated by a sequence of symbols for the range followed by a single symbol for the color of the dial. The sequence of symbols for the range should be selected from the appropriate table in 3.3.10.4. Each HEMPI shall be furnished with two dials; one with white background and black markings (installed) and one with black background and white markings. The single symbol for the color of the dial is designated by one of the following symbols:

Dial color Symbol Black background dial with white graduations and markings B White background dial with black graduations and markings W Special (see 6.2) S Vertical dials (HEMPI only)-white background with black G markings and black background with white markings

The type of pressure connection and its location for connection is designated by two symbols as provided below. The first symbol designates the type of connection fitting. The second symbol designates the location of the pressure connection.

Pressure connection Symbol O-ring union R ¼ NPT (male) P Welded nipple W Threaded vent (caisson only) K Flareless (bite type) 7/16-20 UNF-2A C 7/16-20 UNF-28 (HEMPI only) H Connection location Symbol Back A Bottom O 5 o'clock C

The option for the pressure gauge case containing a liquid fill and the vibration category is designated by the two symbols as provided below. The first symbol designates whether a fill fluid is required (see 3.3.8). The second symbol designates the vibration category (see 4.4.9.1).

Liquid fill Symbol None N Silicone S Vibration category Symbol Category A A Category B B Category C C

The cleanliness is designated by the symbols as specified below. The symbol designates the method of cleaning the pressure element assembly (see 3.3.4).

Cleanliness Symbol General applications G Oxygen applications X

intended Use: