MOYNO® 500 PUMPS - 300 SERIES - 331, 332, 333, 344, 356 AND 367 MODELS - Service Manual

Oct 25, 2026

Service manual for MOYNO® 500 pumps, 300 series covering models 331, 332, 333, 344, 356, and 367. Includes design feature specifications for mechanical seal and packing configurations, plus installation guidance covering mounting position, pre-wetting, piping support, drive alignment, rotation direction, and packing water-flush procedures for 356 models. Provides pump data such as suction/discharge port sizes and discharge pressure, temperature limits for elastomers, operating requirements like self-priming and dry-run prohibition, storage draining, and troubleshooting for failures to pump, overloads, noisy operation, and seal or packing leakage.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages9

Reading Time23 min

AccessFree to download

Installation

Mounting Position

Pre-Wetting

Piping

Drive and Rotation

Water Flush of Packing (356 Models Only)

Operation

Self-Priming

Pressure and Temperature Limits

Storage

Troubleshooting

Failure To Pump

Pump Overloads

Noisy Operation

Mechanical Seal Leakage

Packing Leakage

Section: MOYNO® 500 PUMPS Page: 1 of 8 Date: March 1, 1998 SERVICE MANUAL MOYNO® 500 PUMPS 300 SERIES 331, 332, 333, 344, 356 AND 367 MODELS Mechanical Seal Models Packing Gland Models | DESIGN
FEATURES | MODELS | | | | | | --- | --- | --- | --- | --- | --- | | | 33101 34401
33201 35601
33301 36701 | 33104 34404
33204 35604
33304 36704 | 33108 33308
33208 34408 | 34411
35611 | 35613 | | Housing: | Cast Iron | AISI 316 SS | Nylon | Cast Iron | AISI 316 SS | | Pump Rotor: | Chrome plated 416 SS | Chrome plated 316 SS | Chrome plated 416 SS | Chrome plated 416 SS | Chrome plated 316 SS | | Pump Stator: | NBR (Nitrile) | NBR (Nitrile) | NBR (Nitrile) | NBR (Nitrile) | NBR (Nitrile) | | Shaft: | 416 SS | 316 SS | 416 SS | 416 SS | 316 SS | | Flexible Joint: | Carbon steel/ NBR | 316 SS/ NBR | Carbon steel/ NBR | Carbon steel/ NBR | 316 SS/ NBR | | Bearings: | Ball (sealed) | Ball (sealed) | Ball (sealed) | Ball (sealed) | Ball (sealed) | | Mechanical Seal: | Carbon-ceramic | Carbon-ceramic | Carbon-ceramic | --- | --- | | Packing: | --- | --- | --- | Braided PTFE | Braided PTFE | Note: Alternate elastomers available. Refer to Repair/Conversion kit numbers, page 8. INSTALLATION Mounting Position. Pump may be mounted in any position. When mounting vertically, it is necessary to keep bearings above seals to prevent possible seal leakage into bearings. Pre-Wetting. Prior to connecting pump, wet pump elements and mechanical seal or packing by adding fluid tobe pumped into suction and discharge ports. Turn shaft over several times in a clockwise direction to work fluid into elements. Piping. Piping to pump should be self-supporting to avoid excessive strain on pump housings. See Table 1 for suction and discharge port sizes of each pump model. Use pipe“dope” or tape to facilitate disassembly and to provide seal. Drive. On belt driven units, adjust belt tension to point of non-slip. Do not overtighten. On direct drive units, coupling components should be aligned and spaced at least 1/16” apart. Pump rotation must be clockwise when facing shaft to prevent damage to pump. Check direction of rotation before startup. Water Flush of Packing (356 Models Only) . The packing may be either grease lubricated through a grease fitting in the stuffing box or have plumbing connected to the housing to allow a water flush. Maximum speed is 1750 rpm. When the material being pumped is abrasive in nature, it may be advantageous to flush the packing to prevent leakage under packing and excessive shaft wear. Page 2 Clean water can be injected through a 1/8” NPT tapped hole that normally houses the grease fitting for lubricating the packing. The water can be permitted to leak axially along the shaft in either direction or can be removed from the second tapped hole in the stuffing box. In both cases, the discharge from the stuffing box should be throttled slightly to maintain 10-15 PSI higher pressure in the stuffing box than is present in the discharge housing. Table 1. Pump Data | Pump Models | 331 | 332 | 333 | 344 | 356 | 367 | | --- | --- | --- | --- | --- | --- | --- | | Suction Port (NPT) | 3/4* | 3/4* | 3/4* | 3/4* | 1-1/2 | 2 | | Discharge
Port (NPT) | 3/4 | 3/4 | 3/4 | 3/4 | 1-1/4 | 2 | | Discharge
Pressure (psig) | 150 | 100 | 50 | 40 | 50 | 50 | *08 versions = 1” NPT Table 2. Temperature Limits | Elastomer | Temperature Limits | | --- | --- | | *NBR | 10°-160°F | | *EPDM | 10°-210°F | | *FPM | 10°-240°F | *NBR = Nitrile *EPDM = Ethylene-Propylene-Diene Terpolymer *FPM = Fluoroelastomer OPERATION Self-Priming. With wetted pumping elements, the pump is capable of 25 feet of suction lift when operating at 1750 rpm with pipe size equal to port size. DO NOT RUN DRY. Unit depends on liquid pumped for lubrication. For proper lubrication, flow rate should be at least 10% of rated capacity. Pressure and Temperature Limits. See Table 1 for maximum discharge pr

FAQs

How should the pump be mounted to prevent seal leakage into bearings?

When mounting vertically, keep bearings above seals to prevent possible seal leakage into the bearings.

What are the key requirements before starting the pump?

Wet pump elements and the mechanical seal or packing before connecting. Also ensure the pump rotation is clockwise when facing the shaft and check direction before startup.

What should be done if the pump fails to pump?

Check for belt or coupling slip, verify stator condition and discharge pressure, confirm correct clockwise rotation, replace stripped rotor/shaft threads, and review excessive suction lift or vacuum.

Oct 25, 2026

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