Labconco VACUUBRAND Diaphragm Pump 7393001: Replacing diaphragms and valves

page 52 of 74

+

 Please read section ”Replacing diaphragms and valves” com-

pletely before starting maintenance. 

  The pictures may show other versions of pumps. This does not change 

the method of replacing diaphragms and valves.

➨

Never operate the pump if covers or other parts of 

the pump are disassembled. 

➨

 Before starting maintenance, 

disconnect the electri-

cal power cord

. 

Wait two minutes

 after isolating the 

equipment from AC power to allow the capacitors to 

discharge.

➨

 Ensure that the pump cannot be operated  accidentally. 

➨

Note

: The pump might be contaminated with the pro-

cess chemicals that have been pumped during oper-

ation. Ensure that the pump is decontaminated before 

maintenance. 

➨

 Avoid the release of pollutants.

+ 

Never operate a defective or damaged pump

.

+ 

Take adequate precautions to protect people from the 

effects of dangerous substances that may have con-

taminated the pump and may be released upon dis-

assembly. Ensure that the maintenance technician is 

familiar with the safety procedures which relate to the 

products processed by the pumping system. 

  Use appropriate protective clothing, safety goggles and 

protective gloves.

+

  Check every motor capacitor regularly by measuring its 

capacity and estimating its service life. Replace old ca-

pacitors early enough to prevent a failure. The capaci-

tors must be replaced by a trained electrician.

+

  Allow  sufficient  cooling  of  the  pump  before  starting 

maintenance. Drain condensate, if applicable.

+

Vent the pump and isolate it from the vacuum sys-

tem before you start maintenance.

Replacing diaphragms and valves

 page 53 of 74

Tools required (metric):

-  Torx driver T20

-  5 mm wide Allen key

-  2.5 mm wide slotted screwdriver

-  Flat pliers

-  Diaphragm key width 66 mm

Service kit for ME 2C NT

  ............................................................................

696878

Service kit for ME 4C NT

  ............................................................................

696864

Service kit for MZ 2C NT / PC 201 NT

  .......................................................

696869

Service kit for MD 4C NT / PC 201 NT

   ..................................................... 

696870

Service kit for ME 8C NT

  ............................................................................

696867 

Diaphragm key 

(width 66 mm)  ....................................................................

636554

Ensure that maintenance is done only by suitably 

trained and supervised technicians.

The valves and diaphragms as well as the motor capac-

itors are wear parts. If the rated ultimate vacuum is no 

longer achieved or in case of increased noise level, the 

pump interior, the diaphragms and the valves must be 

cleaned and the diaphragms and valves must be checked 

for cracks or other damage. 

All bearings are encapsulated and are filled with long-life 

lubricant. Under normal operating conditions, the drive 

system is maintenance free.

In  demanding  circumstances,  it  may  be  efficient  to 

check and clean the pump heads on a regular basis. In 

normal use, the lifetime of the diaphragms and valves 

is more than 10,000 operating hours.

-  Prevent internal condensation, transfer of liquids or 

dust. The diaphragms and valves will be damaged if 

liquid is pumped in significant amount.

-  Carry out maintenance frequently if the pump is ex-

posed to corrosive media or in case of deposits.

-  Regular maintenance will improve the lifetime of the 

pump and also protect both users and the environment.

NOTICE

page 54 of 74

The replacement of the diaphragm and the replacement of the valves can 

be carried out separately.

+ 

To replace the valves, remove the head covers of one side of the pump 

along with the assembled valve heads and fittings.

+

 To maintain the diaphragms, the valve heads and the fittings need not  

be disassembled. The head covers can be removed along with the as-

sembled valve heads and fittings.

+

 Service only one side of the pump at a time to avoid the mixing of 

parts.

 Cleaning and inspecting the pump heads

Pump on pump support:

➨

  Remove catchpots (9) at inlet and outlet (see 

”Use and operation”, page 38).

➨ 

Remove the 4 screws affixing the head cov

-

er cowling (W) with a Torx driver T20. Pay 

attention to the washers under the screws 

and remove.

➨

 Pull off head cover cowling (W) carefully. Do 

not tilt.

W

 page 55 of 74

Fittings and tubing of the different pump models:

ME 4C NT

MZ 2C NT

ME 8C NT

MD 4C NT

page 56 of 74

MZ 2C NT 2AK

 MZ 2C NT AK + EK

MZ 2C NT AK SYNCHRO + EK 

PC 101 NT

MD 4C NT 2AK 

MD 4C NT AK + EK

MD 4C NT AK SYNCHRO + EK

PC 201 NT

ME 8C NT +  2 AK 

 page 57 of 74

J

A

I

C

B

E

F

G

H

K

R

T

M

L

N

S

P

U

Q

V

O

D

A: Head alignment pin / mark

B: Connecting rod

C: Housing

D: Washer

E: Diaphragm support disc

F: Diaphragm

G: Diaphragm clamping disc 

  with square head screw

H: Allen screw

 I: Cap

J:  Head cover 

K: Square nut

    View of the disassembled pump head parts

(fig.: MD 4C NT)

L: Fillister head screw

M: O-ring

N: Valve

O: Valve head

P: Hose nozzle 

Q: Connection fastener 

  with hinged cover

R: Disc spring

S: Clamping bracket

T:  Countersunk screw

U: Hose clip

V: Connection tube

This labeling is used throughout the following pages.

page 58 of 74

Opening the hose clip:

➨

 Apply slotted screwdriver as shown and 

turn.

Detach the coupling of the connection tube (V) 

to the other side of the pump at the valve head 

(O). 

Pump at pump support:

Detach the coupling of the connection tube (V) 

to the other side of the pump as well as the 

hose connection to the inlet/outlet of the vacu-

um system at the valve head (O).

➨

 Open the hose clip (U) with a slotted screw-

driver.

➨

 Pull the tubing off the hose connector.

➨

 Disassemble head covers (J) to check the 

diaphragm (F).

➨

 Unscrew four (pump with one/two heads) or 

eight (pump with four heads) Allen screws 

(H) with a 5mm wide Allen key. Remove both 

head covers (J) (pumps with one/two heads: 

only one head cover) together with valve 

heads (O) and connections.

+

 It is not necessary to disassemble the valve 

heads (O), the connection fasteners (Q), or 

the hose connection between the adjacent 

head covers (pumps with four heads).

 Replacing the diaphragm

V

O

U

J

H

O

 page 59 of 74

➨

 Position new diaphragm (F) between dia-

phragm clamping disc with square head 

screw (G) and diaphragm support disc (E).

+

 Note: Position diaphragm with pale side to-

wards diaphragm clamping disc (facing pump 

chamber).

+

 Make sure that the square head screw of the diaphragm clamping disc 

is correctly seated in the guide hole of the diaphragm support disc.

➨

 Lift the diaphragm at the side. Place the diaphragm carefully together 

with diaphragm clamping disc and diaphragm support disc in the dia-

phragm key.

+

 Avoid damage of the diaphragm: Do not excessively bend or crease  

the diaphragm.

➨

 Check for washers (D) between the diaphragm support disc (E) and 

the connecting rod (B). Do not mix the washers from the different pump 

heads, since these are set at the factory to ensure proper pump per-

formance. Make sure that the original number is reassembled at the 

individual pump head. 

+

 Too few washers: The pump will not attain vacuum specification. Too 

many washers: Diaphragm clamping disc will hit head cover, causing 

noisy operation and possibly causing the pump to seize up.

+

 If the old diaphragm is difficult to separate from the diaphragm support 

disc, immerse assembly in naphtha or petroleum ether. Do not inhale 

vapors!

+

 Check diaphragm (F) for damage and re-

place if necessary.

➨

 Lift diaphragm carefully sidewise.

+

 Never use a pointed or sharp-edged tool to 

lift the diaphragm.

➨

  Use the diaphragm key to grip the diaphragm 

support disc (E) below the diaphragm. 

➨ 

Unscrew diaphragm support disc (E) with diaphragm (F) and dia-

phragm clamping disc (G).

F

G

G

E

F

page 60 of 74

+

 Assemble the original number of washers 

(D) between diaphragm support disc (E) and 

connecting rod (B).

➨

 Screw diaphragm clamping disc (G), dia-

phragm (F), diaphragm support disc (E), and 

washers (D) to connecting rod (B). 

➨

 Optimum torque for the diaphragm support disc: 4.4 ft

.

lb

f 

(6 Nm), it is 

recommended to use a torque wrench. Attach torque wrench to dia-

phragm key (hexagonal bolt 6 mm wide). 

  Note: Never use the diaphragm key with any additional tools like tongs 

or Allen keys without appropriate torque limitation. 

Loosen the clamping brackets (S) on the valve 

heads (O).

➨

 Unscrew at each clamping bracket the two 

countersunk screws with a Torx driver T20. 

Remove the clamping brackets.

Loosen connection fastener slightly.

➨

 Turn the fillister head screw (L) with a Torx 

driver T20 at most one turn.

+

 Do not detach the fillister head screw from 

the square nut (K).

➨

 Open the hinged cover of the connection 

fastener (Q) with a slotted screwdriver.

 Replacing the valves

F

G

Q

O

S

 page 61 of 74

➨

 Remove valve heads (O) along with the disc 

springs (R), connection tube if applicable, 

hose nozzles (P) and connection fasteners 

(Q) or move the valve heads carefully aside. 

Note position and orientation of the valve 

heads.

+

 Note position and alignment of valves (N).

➨

 Check valves (N) and O-rings (M) for damage and soiling.

➨

 Replace valves or O-rings if necessary.

➨ 

Use petroleum ether or other industrial solvent to remove deposits. Do 

not inhale vapors.

➨

 Insert O-rings (M) and valves (N). See figure 

for the correct position of the valves:

+

 Inlet side (IN): 

  Marked ”IN” next to the valve seat. The valve 

tongue points at the kidney-shaped orifice in 

the valve seat.

+

 Outlet side (EX):

  Marked with ”EX” next to the valve seat. The 

valve is oriented the same direction as the 

valve at the inlet side.

EX

IN

➨

 Position valve heads (O), with hose nozzle 

(P), if applicable, connection tube or connec-

tion fastener (Q), and disc springs (R) on the 

valve seats. Position disc springs with large 

opening downwards. Pay attention to the 

correct orientation of the valve heads.

+

 Center the valve head with respect to the 

valve seat. The valve head must lie flat on 

the valve seat.

M

N

O

R

O

R

N

Q

page 62 of 74

➨

 Position clamping bracket (S) with counter-

sunk bores facing upwards.

➨

 Align the countersunk bores with the thread-

ed pegs.

➨

 Loosely fasten the countersunk screws and 

correct the alignment of the valve heads if 

necessary.

➨

 Tighten countersunk screws with Torx screwdriver T20.

+

 Torque: 2.2 ft

.

lb

f  

(3 Nm).

➨

 Bring the diaphragms (F) into a position, in 

which they are in contact with the housing 

(C) and centered with respect to the bore.

➨

 Put on head cover (J) with valve heads (O) 

and connections attached. 

+

 Pay attention to the correct orientation of the 

head covers: 

  Housing with head alignment pin: The head 

alignment pin (A) at the pump housing (C) 

has to fit into the recess at the head cover 

(J). 

  Housing with mark (A): Align the recess at 

the head cover with the mark at the pump 

housing.

➨

 Loosely screw in the Allen head screws (H) 

at the head covers diagonally at first slightly 

with a 5 mm wide Allen key, then tighten.

+

 Recommended torque: 8.9 ft

.

lb

f 

(12 Nm). 

➨

 Slide the caps (I) into the head cover.

Valve head with gas ballast or hose nozzle connection:

➨

 Insert square nut (K) in the groove of the head cover (J) or position 

square nut in the groove and then screw on connection fastener.

+

 Loosely fasten fillister head screw (L).

S

H

 page 63 of 74

Pump at pump support:

➨

 Assemble catchpots (9) with joint clips.

➨

 Put head cover cowling on.

➨

 Slide the head cover cowling in the grooves 

of the caps (I) and under the connection fas-

teners (Q). 

➨

 Install the washers. Use a Torx  driver T20 to 

attach the 4 screws holding the head cover 

cowling.

➨

 Tighten  the  fillister  head  screws  (L)  of  the 

connection fasteners (Q) with a Torx driver 

T20.

➨

 Close the hinged covers.

Affix the connection tube (V) to the other side of 

the pump at the valve head (O). 

Pump on pump support:

Affix the connection tube (V) to the other side 

of the pump, as well as the hose connection to 

the inlet or outlet of the vacuum system at the 

valve head (O). 

➨

 Slip connecting tube (V) onto hose connection of valve head.

➨

 Slide on the tube and the hose clip (U) until touching the nose at the 

valve head.

➨

 Close hose clip (U) with flat pliers.

I

Q

Replace diaphragms and valves of the opposite side of 

the pump in the same way!

page 64 of 74

If the pump does not achieve the ultimate vacuum:

-  Whenever the diaphragms and valves have been replaced, a break-in 

period of several hours is required before the pump achieves its ulti-

mate vacuum.

-  In case of an unusual noise, switch off pump immediately and check 

clamping disc positions.

If  the  specified  ultimate  vacuum  is  not  achieved,  and  if  this  does  not 

change after the break-in period:

Check hose connectors at pump heads for leaks. If necessary recheck 

valve seats and pump chambers.

Checking the ultimate vacuum

➨  

After any intervention at the equipment (e.g., repair / maintenance) 

the ultimate vacuum of the pump has to be checked. Only if the pump 

achieves its specified ultimate vacuum, the pump’s leak rate is low 

enough to ensure that no explosive atmospheres will occur in the inte-

rior of the equipment.  

 page 65 of 74

➨ 

Remove  the  4  screws  affixing  the  counter 

holder of the exhaust vapor condenser with 

a Torx driver T10.  Remove the exhaust va-

por condenser. In doing so pull the PTFE 

hose out of the inlet of the exhaust vapor 

condenser.

➨

 If necessary, pull off the old pressure relief 

valve and install the new one. Check for cor-

rect position of the PTFE-foil under the pres-

sure relief valve.

➨

 Feed the PTFE hose into the inlet of the ex-

haust vapor condenser. Mount the condens-

er with the counter holder (Torx screws T10) 

to the pump. Fasten union nut. 

Overpressure 

safety relief device

 ............................

638821

(at exhaust waste vapor condenser)

➨

 Remove catchpot (9) at outlet (see ”Use and 

operation”, pg. 38). 

➨

 Loosen the union nut at the inlet of the ex

-

haust vapor condenser.

 Replacing the overpressure safety relief device

page 66 of 74

1

2

2

Important: Check operability and safety of the pump 

after repair and after replacing the device fuse.

Check the electrical safety (protective conductor resis-

tance, insulating resistance, high voltage test) according 

to IEC 61010 and national regulations.

 Replacing the fuse

Order-no. Set of fuses NT

............................

636542

The pigtail fuses are integrated into wires ((1), 

black and blue) inside the terminal box. 

To replace the fuses it is necessary to replace 

both wires completely (fixed with flat pin bush

-

ings (2)).

➨

 Open the terminal box. Unscrew the four screws with a Torx driver 

T20. Remove the terminal box cover. Remove both wires with inte-

grated fuses (fixed with flat pin bushings (2), see figure). Mount the 

new wires (flat pin bushings) and close the terminal box. Fasten the 

cover with the four screws.

➨

Switch off the pump. 

➨

 Disconnect the electrical power cord

 before opening 

the terminal box. After disconnecting from power, 

wait 

two minutes

 to allow the capacitors to discharge. 

+

 The replacing of the fuse has to be carried out by a 

trained electrician.

+ 

After replacing the fuse, the pump must be checked for 

electric safety (see below)! Identify and eliminate the 

cause of failure before switching on the pump again.